ATDH - Admission Test for Dental Hygiene — Questions and Answers

Question 1: What is the area of a rectangle with length 8 cm and width 5 cm?

26 cm²
80 cm²
13 cm²
40 cm² (Correct answer)

Correct answer: 40 cm²

The area of a rectangle is calculated as length × width = 8 × 5 = 40 cm².

Question 2: Review the four angles presented. Rank them in order from largest to smallest.

A, C, D, B
B, C, D, A
A, D, C, B (Correct answer)
D, A, B, C

Correct answer: A, D, C, B

Angle A is the largest, being the only obtuse angle. Angle D is the next largest, appearing to be close to a right angle. Angle C is smaller than D, and Angle B is the most acute and therefore the smallest. The correct ranking from largest to smallest is A, D, C, B.

Question 3: The Mariana Trench is the result of an ancient geological confrontation—a collision between two massive plates in the planet’s crust—called a subduction. What is the author’s purpose for including the phrase: “a collision between two massive plates in the planet’s crust”?

To describe where the trench is located
To communicate the meaning of a scientific term (Correct answer)
To explain how the trench became so deep
To convey the dangers of oceanic exploration

Correct answer: To communicate the meaning of a scientific term

Explanation: The author's purpose for including the phrase "a collision between two massive plates in the planet’s crust" is to communicate the meaning of a scientific term, specifically, the geological process that led to the formation of the Mariana Trench.

Question 4: Peristalsis is a function of which body system?

Digestive system (Correct answer)
Urinary system
Respiratory system
Circulatory system

Correct answer: Digestive system

Peristalsis is the wave-like smooth muscle contractions that propel food through the digestive tract.

Question 5: Which word completes this sentence? I hope that you will __________ my congratulations.

accent
excerpt
accept (Correct answer)
except

Correct answer: accept

Explanation: The word "accept" means to receive or agree to something, which fits the context of receiving congratulations. The other options do not fit the context of the sentence.

Question 6: Which might have an RNA genome?

Protists
Fungi
Viruses (Correct answer)
Bacteria

Correct answer: Viruses

Explanation: Viruses can have RNA genomes. Unlike bacteria, fungi, and protists, which typically have DNA genomes, viruses can contain either RNA or DNA as their genetic material. Some viruses, known as RNA viruses, have RNA genomes, while others have DNA genomes.

Question 7: Which of the following compounds is an ester?

CH3OH
CH3NH2
CH3COOCH3 (Correct answer)
CH3COOH

Correct answer: CH3COOCH3

CH3COOCH3 (methyl acetate) is an ester, identifiable by the -COO- linkage formed from a carboxylic acid reacting with an alcohol.

Question 8: The sinoatrial (SA) node is located in which chamber of the heart?

Right atrium (Correct answer)
Left atrium
Right ventricle
Left ventricle

Correct answer: Right atrium

The SA node, the heart's natural pacemaker, is located in the wall of the right atrium near the superior vena cava.

Question 9: Read this excerpt from a letter to a patient. Your improved cholesterol test results are __________, and we encourage you to maintain a healthy diet and daily exercise regimen to help you sustain those results! Which option completes the sentence while maintaining the style?

pretty terrific
wicked awesome
commendable (Correct answer)
nifty

Correct answer: commendable

Explanation: "Commendable" is the most appropriate word choice for a letter to a patient because it conveys a sense of praise and approval for the improved cholesterol test results. It is a formal and respectful term that acknowledges the patient's efforts and achievements in maintaining their health.

Question 10: A passage describes the formation of dental biofilm: "The initial phase involves the adhesion of a conditioning film, known as the acquired pellicle, to the tooth surface. This acellular layer is rapidly colonized by early bacterial settlers, predominantly streptococci. Over time, a complex, multi-species community develops through coaggregation, creating a mature biofilm with a sophisticated structure that protects the embedded bacteria from antimicrobial agents and host defenses." According to the passage, which of the following is the first step in the formation of dental biofilm?

The formation of the acquired pellicle. (Correct answer)
Colonization by streptococci.
Coaggregation of multiple bacterial species.
Development of a mature, protected community.

Correct answer: The formation of the acquired pellicle.

The text outlines a clear sequence of events. It states, 'The initial phase involves the adhesion of a conditioning film, known as the acquired pellicle...' This happens before the bacterial colonization and subsequent maturation of the biofilm.

Question 11: A right angle measures exactly:

90° (Correct answer)
120°
45°
180°

Correct answer: 90°

A right angle is exactly 90° and is indicated by a small square symbol in geometric diagrams.

Question 12: Sodium fluoride (NaF), a common ingredient in toothpaste, is formed when a sodium atom transfers a valence electron to a fluorine atom. What type of chemical bond is formed between the resulting sodium and fluoride particles?

Hydrogen bond
Metallic bond
Covalent bond
Ionic bond (Correct answer)

Correct answer: Ionic bond

An ionic bond is formed by the electrostatic attraction between oppositely charged ions. In this case, sodium (Na) loses an electron to become a positive cation (Na⁺), and fluorine (F) gains that electron to become a negative anion (F⁻). The attraction between these two ions creates the ionic bond.

Question 13: What is the sum of the interior angles of a triangle?

270°
180° (Correct answer)
90°
360°

Correct answer: 180°

The interior angles of any triangle always sum to 180°.

Question 14: The process by which white blood cells engulf and destroy pathogens is called:

Phagocytosis (Correct answer)
Pinocytosis
Osmosis
Exocytosis

Correct answer: Phagocytosis

Phagocytosis is the process by which phagocytes (neutrophils, macrophages) engulf and digest microorganisms and cellular debris.

Question 15: Which type of reaction joins amino acids together to form proteins?

Condensation (peptide bond formation) (Correct answer)
Hydrolysis
Esterification
Saponification

Correct answer: Condensation (peptide bond formation)

Condensation (dehydration synthesis) links amino acids via peptide bonds, releasing a water molecule for each bond formed.

Question 16: The term 'distal' in anatomical directional terminology means:

Below another structure
Farther from the point of attachment or origin (Correct answer)
Toward the front of the body
Closer to the midline of the body

Correct answer: Farther from the point of attachment or origin

Distal refers to a position farther from the point of attachment or origin of a limb, opposite of proximal.

Question 17: Two lines that never intersect and are always the same distance apart are called:

Skew lines
Perpendicular lines
Intersecting lines
Parallel lines (Correct answer)

Correct answer: Parallel lines

Parallel lines lie in the same plane, never intersect, and maintain a constant distance from each other.

Question 18: The primary function of red blood cells (erythrocytes) is to:

Transport oxygen (Correct answer)
Produce antibodies
Aid in blood clotting
Fight infection

Correct answer: Transport oxygen

Erythrocytes contain hemoglobin, which binds oxygen in the lungs and delivers it to body tissues.

Question 19: A dental clinic budgets its monthly expenses based on the number of patients seen. The clinic's fixed costs are $15,000 per month. The variable cost per patient is $25. If the total monthly expenses were $27,500, which equation correctly represents the situation and how many patients (p) were seen that month?

15000 + 27500 = 25p; 1700 patients
25p - 15000 = 27500; 1700 patients
15000p + 25 = 27500; This is not the correct model.
15000 + 25p = 27500; 500 patients (Correct answer)

Correct answer: 15000 + 25p = 27500; 500 patients

The total monthly expense is the sum of the fixed costs and the total variable costs. The total variable cost is the cost per patient ($25) times the number of patients (p). Therefore, the equation is 15000 + 25p = 27500. To solve for p, subtract 15000 from both sides: 25p = 12500. Then, divide by 25: p = 500.

Question 20: In organic structural formulas, what does the symbol 'R' conventionally represent?

An alkyl group or generic organic substituent (Correct answer)
A radical species
A ring structure only
A reactive functional group site

Correct answer: An alkyl group or generic organic substituent

In organic chemistry, 'R' is shorthand notation for any alkyl group or generic organic substituent, used to generalize a structural formula across a family of compounds.

Question 21: Which type of tissue lines the inner surfaces of blood vessels and the heart?

Muscle tissue
Connective tissue
Epithelial tissue (Correct answer)
Nervous tissue

Correct answer: Epithelial tissue

Simple squamous epithelial tissue, called endothelium, lines the interior of blood vessels and the heart.

Question 22: A patient has a genetic disorder that prevents their cells from properly synthesizing proteins. A defect in which organelle would most directly cause this issue by failing to 'read' the mRNA transcript?

Mitochondrion
Ribosome (Correct answer)
Golgi apparatus
Lysosome

Correct answer: Ribosome

The ribosome is the cellular machinery responsible for translation, the process of synthesizing a protein from an mRNA template. The ribosome reads the codons on the mRNA strand and facilitates the linking of amino acids brought by tRNA to form a polypeptide chain. A defect in ribosomes would directly impair protein synthesis.

Question 23: A 3D object is constructed from 5 identical cubes. It consists of a 2x2 square base (4 cubes) with one additional cube placed on top of the front-left cube. Which of the following correctly describes the Front View and the Top View of this object?

Front View: An 'L' shape, 2 cubes high on the left and 1 cube high on the right. Top View: A 2x2 square. (Correct answer)
Front View: A 2x2 square. Top View: A 2x2 square.
Front View: A 2x1 vertical rectangle. Top View: A 2x2 square.
Front View: An 'L' shape, 2 cubes high on the left and 1 cube high on the right. Top View: An 'L' shape.

Correct answer: Front View: An 'L' shape, 2 cubes high on the left and 1 cube high on the right. Top View: A 2x2 square.

When viewed from the top, you see the complete 2x2 footprint of the base, so the Top View is a 2x2 square. When viewed from the front, the cube stacked on the front-left position makes the left column appear 2 cubes high, while the right column (which has no stacked cube) is only 1 cube high. This creates an 'L' shape.

Question 24: Which of the following sentences contains a punctuation error?

Dr. Miller's office is located at 123 Main Street, Anytown, USA.
After sterilizing the instruments the hygienist prepared the treatment room. (Correct answer)
The clinic offers several services: cleanings, X-rays, and fluoride treatments.
The patient's chart, which was updated yesterday, indicates a new allergy.

Correct answer: After sterilizing the instruments the hygienist prepared the treatment room.

The sentence 'After sterilizing the instruments the hygienist prepared the treatment room' has an introductory adverbial phrase ('After sterilizing the instruments'). According to standard punctuation rules, such introductory phrases should be set off from the main clause with a comma. The correct punctuation is: 'After sterilizing the instruments, the hygienist prepared the treatment room.'

Question 25: The axial skeleton includes which of the following structures?

Pelvis and clavicle
Humerus and radius
Skull, vertebral column, and rib cage (Correct answer)
Femur and tibia

Correct answer: Skull, vertebral column, and rib cage

The axial skeleton consists of the skull, vertebral column, sternum, and ribs, forming the central axis of the body.

Question 26: Which monosaccharide serves as the primary fuel molecule for cellular respiration in the human body?

Galactose
Ribose
Fructose
Glucose (Correct answer)

Correct answer: Glucose

Glucose (C6H12O6) is the main substrate for cellular respiration, being broken down through glycolysis and the citric acid cycle to produce ATP.

Question 27: What structural feature distinguishes unsaturated fatty acids from saturated fatty acids?

A different terminal functional group
More oxygen atoms in the chain
Presence of one or more C=C double bonds (Correct answer)
A shorter carbon chain length

Correct answer: Presence of one or more C=C double bonds

Unsaturated fatty acids contain one or more carbon-carbon double bonds (C=C) in their hydrocarbon chains, while saturated fatty acids have only single bonds.

Question 28: Saliva contains bicarbonate and phosphate ions that help maintain a relatively stable pH in the oral cavity, even after a person consumes acidic foods. This system is an example of a biological:

Isotope
Catalyst
Solvent
Buffer (Correct answer)

Correct answer: Buffer

A buffer system is a solution that can resist pH change upon the addition of an acidic or basic component. The bicarbonate and phosphate systems in saliva are crucial for neutralizing acids, thereby protecting tooth enamel from demineralization.

Question 29: Which condition is characterized by a symbiotic association between two species, without harm to either, but with some benefit to both symbionts?

Mutualism (Correct answer)
Commensalism
Parasitism
Predation

Correct answer: Mutualism

Explanation: Mutualism is a type of symbiotic relationship between two species in which both organisms benefit from the association. In mutualism, neither species is harmed, and both receive some form of benefit. This contrasts with predation, where one organism benefits at the expense of the other, and parasitism, where one organism benefits while the other is harmed. Commensalism, while similar to mutualism, involves one organism benefiting while the other is unaffected.

Question 30: Which type of joint allows the greatest range of motion?

Hinge joint
Pivot joint
Ball-and-socket joint (Correct answer)
Saddle joint

Correct answer: Ball-and-socket joint

Ball-and-socket joints (e.g., hip and shoulder) permit movement in all planes, providing the greatest range of motion.

Question 31: If a patient's chart records a temperature of 37°C, what is the equivalent in Fahrenheit? (F = 9/5 × C + 32)

96.8°F
100.4°F
102.2°F
98.6°F (Correct answer)

Correct answer: 98.6°F

F = (9/5 × 37) + 32 = 66.6 + 32 = 98.6°F, which is normal human body temperature.

Question 32: Which statement about aromatic compounds is FALSE?

They contain a cyclic ring with delocalized pi electrons
They satisfy Hückel's rule (4n+2 π electrons)
They are stabilized by resonance
They readily undergo addition reactions (Correct answer)

Correct answer: They readily undergo addition reactions

Aromatic compounds strongly prefer electrophilic substitution over addition reactions because addition would disrupt the aromatic pi system and its stabilizing resonance energy.

Question 33: A dental supply company sells two types of gloves, latex and nitrile. The ratio of the price of a box of latex gloves to a box of nitrile gloves is 3:5. If a box of nitrile gloves costs $12.50, what is the cost of a box of latex gloves?

$7.50 (Correct answer)
$4.17
$9.50
$20.83

Correct answer: $7.50

Let the price of latex gloves be 3x and the price of nitrile gloves be 5x. We are given that the price of nitrile gloves is $12.50. So, 5x = $12.50. Solving for x, we get x = $12.50 / 5 = $2.50. The cost of the latex gloves is 3x, so 3 * $2.50 = $7.50.

Question 34: Choose the word that correctly completes the following sentence: 'The dental hygienist gave the patient expert _______ on how to improve their brushing technique.'

advise
advice (Correct answer)
device
devise

Correct answer: advice

'Advice' is a noun meaning 'guidance or recommendations.' 'Advise' is a verb meaning 'to offer suggestions.' In this sentence, the hygienist is giving something (a noun) to the patient. Therefore, 'advice' is the correct choice.

Question 35: In eukaryotic cells, which organelle is primarily responsible for generating the majority of the cell's supply of adenosine triphosphate (ATP) through aerobic respiration?

Nucleus
Mitochondrion (Correct answer)
Ribosome
Golgi apparatus

Correct answer: Mitochondrion

The mitochondrion is known as the 'powerhouse' of the cell because it is the site of the Krebs cycle and oxidative phosphorylation, which together produce the vast majority of cellular ATP.

Question 36: What is saponification?

Oxidation of an aldehyde to a carboxylic acid
Acid-catalyzed esterification of a fatty acid
Base-catalyzed hydrolysis of an ester to form soap (Correct answer)
Acid-catalyzed formation of a peptide bond

Correct answer: Base-catalyzed hydrolysis of an ester to form soap

Saponification is the base-catalyzed hydrolysis of an ester (typically a fat or oil) to produce glycerol and the carboxylate salts of fatty acids, which are soaps.

Question 37: A study summary explains a new dental material: "The novel composite resin incorporates bioactive glass particles that release calcium and phosphate ions in response to a low pH environment, such as that occurring during an acid attack from plaque bacteria. This localized ion release is designed to promote remineralization of adjacent tooth enamel." A patient with a high-sugar diet and a history of multiple cavities receives a restoration with this new material. Based on the passage, what is the most likely benefit for this specific patient?

The restoration will change color to warn the patient of a low pH.
The restoration will prevent any future plaque from forming.
The material will help strengthen the tooth structure surrounding the filling during acid challenges. (Correct answer)
The bioactive glass will completely eliminate all plaque bacteria in the patient's mouth.

Correct answer: The material will help strengthen the tooth structure surrounding the filling during acid challenges.

The passage states the material releases ions to 'promote remineralization of adjacent tooth enamel' in response to low pH (acid attacks). A patient with a high-sugar diet is prone to such acid attacks. Therefore, the material's ability to help strengthen the surrounding tooth structure is the direct, applicable benefit described.

Question 38: A triangle has a base of 12 m and a height of 7 m. What is its area?

168 m²
42 m² (Correct answer)
84 m²
19 m²

Correct answer: 42 m²

Area of a triangle = ½ × base × height = ½ × 12 × 7 = 42 m².

Question 39: A key structural difference between deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) is the type of sugar present in their nucleotide backbones. What are the respective sugars found in DNA and RNA?

Glucose in DNA, Fructose in RNA
Deoxyribose in DNA, Ribose in RNA (Correct answer)
Ribose in DNA, Deoxyribose in RNA
Sucrose in both DNA and RNA

Correct answer: Deoxyribose in DNA, Ribose in RNA

The names of the nucleic acids themselves indicate their sugar components. DNA contains the pentose sugar deoxyribose, while RNA contains the pentose sugar ribose. The key difference is that deoxyribose lacks an oxygen atom at the 2' carbon position that is present in ribose.

Question 40: What is the general molecular formula for alkanes?

CnH2n+2 (Correct answer)
CnH2n-2
CnH2n
CnHn

Correct answer: CnH2n+2

Alkanes are saturated hydrocarbons with the formula CnH2n+2, meaning each carbon forms only single bonds and carries the maximum number of hydrogens.

Question 41: A negative feedback mechanism is best described as:

A mechanism that only operates during exercise
A process that returns the body to homeostasis by opposing a change (Correct answer)
A process that amplifies changes away from a set point
A one-way signaling pathway in the nervous system

Correct answer: A process that returns the body to homeostasis by opposing a change

Negative feedback loops detect deviations from a set point and trigger corrective responses to restore homeostasis.

Question 42: A dental hygienist needs to prepare 500 mL of a 0.2 M saline solution (NaCl) for a patient rinse. How many grams of sodium chloride (NaCl) are required? (Molar mass of NaCl ≈ 58.44 g/mol)

0.10 g
29.22 g
11.69 g
5.84 g (Correct answer)

Correct answer: 5.84 g

To solve this, first calculate the number of moles needed using the formula: Moles = Molarity × Volume (in Liters). Convert 500 mL to 0.5 L. Moles = 0.2 mol/L × 0.5 L = 0.1 mol. Then, convert moles to grams: Grams = Moles × Molar Mass. Grams = 0.1 mol × 58.44 g/mol = 5.84 g.

Question 43: A cell needs to move calcium ions from the cytoplasm, where the concentration is low, into the sarcoplasmic reticulum, where the concentration is high. This process requires energy. Which mechanism of cellular transport is being used?

Active Transport (Correct answer)
Osmosis
Facilitated Diffusion
Simple Diffusion

Correct answer: Active Transport

Active transport is the movement of substances across a cell membrane against their concentration gradient (from a region of lower concentration to a region of higher concentration). This process requires cellular energy, typically in the form of ATP. The other options are forms of passive transport, which do not require energy.

Question 44: The volume of a cylinder with radius 4 cm and height 10 cm is approximately: (Use π ≈ 3.14)

251.2 cm³
125.6 cm³
1004.8 cm³
502.4 cm³ (Correct answer)

Correct answer: 502.4 cm³

Volume of a cylinder = π × r² × h = 3.14 × 16 × 10 = 502.4 cm³.

Question 45: The Pythagorean theorem states that for a right triangle with legs a and b and hypotenuse c:

a² + b² = c² (Correct answer)
a × b = c²
a² − b² = c
a + b = c

Correct answer: a² + b² = c²

The Pythagorean theorem states a² + b² = c², relating the squares of a right triangle's three sides.

Question 46: A trapezoid has parallel bases of 6 ft and 10 ft and a height of 4 ft. What is its area?

32 ft² (Correct answer)
64 ft²
24 ft²
40 ft²

Correct answer: 32 ft²

Area of a trapezoid = ½ × (b₁ + b₂) × h = ½ × (6 + 10) × 4 = ½ × 16 × 4 = 32 ft².

Question 47: When a halogen replaces a hydrogen atom on an alkane under UV light, which type of reaction occurs?

Addition reaction
Free-radical substitution reaction (Correct answer)
Elimination reaction
Rearrangement reaction

Correct answer: Free-radical substitution reaction

Halogenation of alkanes is a free-radical substitution reaction where a halogen atom replaces a hydrogen atom on the alkane chain.

Question 48: Gas exchange between the blood and body tissues is called:

Pulmonary respiration
Ventilation
Internal respiration (Correct answer)
External respiration

Correct answer: Internal respiration

Internal (tissue) respiration is the exchange of O₂ and CO₂ between capillary blood and surrounding body cells.

Question 49: According to Markovnikov's rule, when HBr adds to an unsymmetrical alkene, where does the bromine atom attach?

To the carbon bearing the most hydrogen atoms
Only to the terminal carbon regardless of substitution
Randomly to either carbon of the double bond
To the carbon bearing the fewest hydrogen atoms (more substituted carbon) (Correct answer)

Correct answer: To the carbon bearing the fewest hydrogen atoms (more substituted carbon)

Markovnikov's rule states that the nucleophilic halide (Br-) adds to the more substituted carbon because the carbocation intermediate at that position is more stable.

Question 50: In the fluid mosaic model of the cell membrane, what is the primary function of integral proteins?

To transport molecules across the membrane and act as receptors. (Correct answer)
To synthesize ATP for cellular energy requirements.
To provide a rigid structure and shape to the cell membrane.
To store genetic information for cell replication.

Correct answer: To transport molecules across the membrane and act as receptors.

Integral proteins are embedded within the phospholipid bilayer and play crucial roles as channels or transporters for substances that cannot freely diffuse across the membrane, such as ions and glucose. They also function as receptors for cell signaling.

Question 51: A bar chart displays the results of a patient satisfaction survey for a dental practice. The percentages of 'Very Satisfied' responses for three hygienists are: Hygienist A: 85%, Hygienist B: 90%, Hygienist C: 75%. Which of the following statements accurately interprets the data?

The average satisfaction rating for the three hygienists is 85%.
Hygienist A's satisfaction rating is 10 percentage points lower than Hygienist B's.
Hygienist C has the highest patient satisfaction.
Hygienist B has the highest patient satisfaction. (Correct answer)

Correct answer: Hygienist B has the highest patient satisfaction.

By directly comparing the percentages, Hygienist B has a 90% satisfaction rating, which is higher than Hygienist A's 85% and Hygienist C's 75%. Therefore, Hygienist B has the highest patient satisfaction.

Question 52: The central nervous system (CNS) consists of:

Spinal cord and peripheral nerves
Brain and spinal cord (Correct answer)
All nerves outside the brain
Brain, spinal cord, and cranial nerves

Correct answer: Brain and spinal cord

The CNS is composed of the brain and spinal cord; all other neural tissue forms the peripheral nervous system.

Question 53: Which part of the brain regulates basic life functions such as breathing, heart rate, and blood pressure?

Brainstem (Correct answer)
Cerebral cortex
Cerebellum
Thalamus

Correct answer: Brainstem

The brainstem (medulla oblongata, pons, midbrain) controls vital autonomic functions including respiration and cardiovascular activity.

Question 54: Which of the following inequalities represents the range of values for 'x' if |3x - 6| < 9?

-1 < x < 5 (Correct answer)
x > 5 or x < -1
x < 5
x > -1

Correct answer: -1 < x < 5

The absolute value inequality |3x - 6| < 9 can be rewritten as -9 < 3x - 6 < 9. To solve for x, first add 6 to all three parts of the inequality: -9 + 6 < 3x < 9 + 6, which simplifies to -3 < 3x < 15. Finally, divide all three parts by 3: -1 < x < 5.

Question 55: You are presented with a 3D cube that has symbols on three visible faces: a solid circle on the top, a solid square on the front, and a solid triangle on the right side. Which of the following 2D patterns could be folded to form this exact cube?

A pattern where the square is central, the circle is directly above it, and the triangle is directly to the left of it.
A pattern where the square is central, the circle is directly above it, and the triangle is directly to the right of it. (Correct answer)
A pattern where the square and circle are adjacent, but the triangle is adjacent to the circle instead of the square.
A pattern where the circle, square, and triangle are arranged sequentially in a single row.

Correct answer: A pattern where the square is central, the circle is directly above it, and the triangle is directly to the right of it.

To form the described cube, the faces must be oriented correctly relative to each other. If the square is the front face, the circle must be able to fold into the top position, and the triangle must be able to fold into the right-side position. This requires both the circle and the triangle to be directly adjacent to the square in the unfolded pattern, in the correct 'up' and 'right' positions.

Question 56: What is the volume of a rectangular prism with length 5 cm, width 4 cm, and height 3 cm?

120 cm³
47 cm³
60 cm³ (Correct answer)
12 cm³

Correct answer: 60 cm³

Volume of a rectangular prism = l × w × h = 5 × 4 × 3 = 60 cm³.

Question 57: Photographs of planet Earth taken from satellites show an exquisite spherical body with an apparently smooth, clearly defined surface. However, we who dwell on the Earth’s surface have a different perspective: we know that the surface includes both miles-high peaks and miles-deep valleys. Which transition word could be substituted for the word “however” without changing the meaning of the sentence?

Thus
Therefore
Likewise
Yet (Correct answer)

Correct answer: Yet

Explanation: The word "yet" can be used as a synonym for "however" to indicate a contrast between two statements. In this context, "yet" effectively conveys the contrast between the perspective from space and the perspective from the Earth's surface, similar to how "however" does.

Question 58: A square piece of paper is folded in half diagonally from the top-right corner to the bottom-left corner. Then, the resulting triangle is folded in half again along its line of symmetry. Two small circular holes are punched through all layers: one near the right-angle corner and one in the center of the longest edge. What pattern will be visible when the paper is fully unfolded?

Two holes on one diagonal and two holes on the other diagonal. (Correct answer)
Four holes forming a square in the center of the paper.
Two holes along the diagonal that was first folded.
Four holes in a diamond pattern along the diagonals, and four holes in a square pattern in the center.

Correct answer: Two holes on one diagonal and two holes on the other diagonal.

The first unfold mirrors the two holes across the second fold line, creating four holes on the half-folded triangular paper. The final unfold mirrors these four holes across the main diagonal. The hole near the right-angle corner will be mirrored to create two holes on one diagonal. The hole on the long edge will be mirrored to create two holes on the other diagonal. The final result is four holes total, with two on each of the paper's diagonals.

Question 59: Which is the strongest attractive interaction in pure ethanol?

London dispersion forces
Dipole-dipole forces
Hydrogen bonding (Correct answer)
Ionic bonding

Correct answer: Hydrogen bonding

Explanation: In pure ethanol, the strongest attractive interaction is hydrogen bonding. This occurs because ethanol molecules contain hydrogen atoms bonded to highly electronegative oxygen atoms. These hydrogen atoms can form hydrogen bonds with other ethanol molecules, where the partially positive hydrogen atom of one molecule is attracted to the partially negative oxygen atom of another molecule. This type of bonding is stronger than dipole-dipole forces, London dispersion forces, and ionic bonding in the context of pure ethanol.

Question 60: A dental hygienist is writing a patient education brochure and wants to ensure the tone is professional and clear. Which of the following sentences is most appropriate for this purpose?

It's super important to maintain good oral hygiene by brushing and flossing.
Failing to floss daily is a really bad idea for your gums.
You've gotta brush your teeth better or you'll get nasty cavities.
Consistent daily brushing and flossing are essential for preventing periodontal disease and tooth decay. (Correct answer)

Correct answer: Consistent daily brushing and flossing are essential for preventing periodontal disease and tooth decay.

This sentence uses formal language ('consistent,' 'essential,' 'preventing periodontal disease'), maintains an objective and professional tone, and clearly communicates the necessary information without using slang or overly casual phrasing. The other options are too informal or subjective for a professional document.

Question 61: A disaccharide is a carbohydrate composed of how many monosaccharide units?

Three
Many (more than ten)
Two (Correct answer)
One

Correct answer: Two

A disaccharide consists of exactly two monosaccharide units joined by a glycosidic bond; sucrose and lactose are common examples.

Question 62: I like biology, but I'm taking cell biology 301 next semester, which looks difficult. Which option uses correct capitalization?

biology, but I'm taking Cell biology 301
Biology, but I'm taking Cell Biology 301
Biology, but I'm taking cell biology 301
biology, but I'm taking Cell Biology 301 (Correct answer)

Correct answer: biology, but I'm taking Cell Biology 301

Explanation: The word "biology" should be lowercase because it is not at the beginning of the sentence and is not a proper noun in this context. "Cell Biology 301" is the specific name of the course, so it should be capitalized.

Question 63: A 2D pattern in the shape of a cross is made of six squares. If it is folded into a cube, which face is always opposite the face labeled '3'? The pattern is arranged with four squares in a vertical line, labeled 1, 2, 3, 4 from top to bottom. A square labeled 'L' is to the left of square 2, and a square labeled 'R' is to the right of square 2.

Face 4
Face R
Face 1 (Correct answer)
Face L

Correct answer: Face 1

In this standard cross-shaped net, faces that are separated by one other face in a straight line will be opposite each other when folded. Face 1 is separated from Face 3 by Face 2. Therefore, Face 1 and Face 3 will be opposite. Similarly, Face L would be opposite Face R, and Face 2 would be opposite Face 4.

Question 64: A research article on xerostomia (dry mouth) states: "Saliva's buffering capacity is crucial for neutralizing plaque acids produced by cariogenic bacteria after carbohydrate consumption. A diminished salivary flow, therefore, not only leads to discomfort but also significantly elevates the risk of dental caries by compromising this vital protective mechanism." Based on this excerpt, what is the primary reason that reduced saliva flow increases the risk of cavities?

It prevents the proper digestion of carbohydrates.
It leads to significant patient discomfort.
It directly increases the population of cariogenic bacteria.
It reduces the mouth's ability to counteract acid. (Correct answer)

Correct answer: It reduces the mouth's ability to counteract acid.

The passage explicitly states that saliva's 'buffering capacity is crucial for neutralizing plaque acids' and that a diminished flow 'compromises this vital protective mechanism.' This directly supports the conclusion that the reduced ability to counteract acid is the reason for the increased caries risk. While discomfort is mentioned, it is not the reason for the increased risk of caries. The passage does not claim that low saliva increases bacterial populations or affects digestion.

Question 65: Which hormone is secreted by the pancreatic beta cells to lower blood glucose levels?

Cortisol
Glucagon
Insulin (Correct answer)
Epinephrine

Correct answer: Insulin

Insulin, released by beta cells of the islets of Langerhans, promotes glucose uptake by cells, lowering blood glucose.

Question 66: A patient uses a highly concentrated saline (saltwater) rinse, creating a hypertonic environment in the oral cavity. What is the most likely effect on bacterial cells present on the mucosal surfaces?

The cells will remain unaffected by the rinse.
The cells will rapidly divide.
The cells will lose water and shrink. (Correct answer)
The cells will swell and may burst.

Correct answer: The cells will lose water and shrink.

In a hypertonic solution, the solute concentration outside the cell is higher than inside. Due to osmosis, water moves from an area of higher water concentration (inside the cell) to an area of lower water concentration (outside the cell), causing the cell to lose water and shrink, a process called plasmolysis.

Question 67: How many inches are in 3.5 feet?

48 inches
42 inches (Correct answer)
36 inches
30 inches

Correct answer: 42 inches

Since 1 foot = 12 inches, 3.5 feet × 12 = 42 inches.

Question 68: A community dental clinic has 200 active patients. A review of their records indicates that 50 of these patients have been diagnosed with gingivitis. If a patient is selected at random, what is the probability that they have gingivitis?

1/3
1/4 (Correct answer)
1/2
1/5

Correct answer: 1/4

Probability is calculated by dividing the number of specific outcomes (patients with gingivitis) by the total number of possible outcomes (total patients). The calculation is 50 / 200, which simplifies to 1/4.

Question 69: Looking closer, Vescovo concluded that it was that ubiquitous artifact of twenty-first-century life— a plastic bag! What is the meaning of “ubiquitous” as it is used in this sentence?

Controversial
Conventional
Unusual
Universal (Correct answer)

Correct answer: Universal

Explanation: "Ubiquitous" means present, appearing, or found everywhere. In this context, it describes the plastic bag as a common and widespread artifact of twenty-first-century life.

Question 70: What is the hybridization of the carbon atom in a carbonyl group (C=O)?

sp3
sp2 (Correct answer)
sp
d2sp3

Correct answer: sp2

The carbonyl carbon is sp2 hybridized, forming three sigma bonds in a planar arrangement and one pi bond with the oxygen via overlapping unhybridized p orbitals.

Question 71: A passage discusses the oral microbiome: "A state of microbial equilibrium, or eubiosis, is characteristic of oral health. In this state, commensal bacteria predominate and pathogenic species are kept in check. A shift to dysbiosis, often triggered by factors like a high-sucrose diet or poor oral hygiene, allows pathogenic bacteria to flourish, leading to inflammation and disease. This is not merely an overgrowth of 'bad' bacteria, but a fundamental change in the entire microbial community's structure and function." Which statement best describes the relationship between eubiosis and dysbiosis as presented in the passage?

Dysbiosis is a necessary precursor to achieving eubiosis.
They are two unrelated states of the oral environment.
Eubiosis and dysbiosis describe the same condition but in different locations within the mouth.
They are opposing conditions, where eubiosis represents a healthy balance and dysbiosis represents an unhealthy imbalance. (Correct answer)

Correct answer: They are opposing conditions, where eubiosis represents a healthy balance and dysbiosis represents an unhealthy imbalance.

The passage defines eubiosis as a 'microbial equilibrium' associated with 'oral health' and dysbiosis as a 'shift' from that state which leads to 'disease.' This establishes them as opposite conditions: one representing a healthy, balanced state and the other an unhealthy, imbalanced one.

Question 72: During DNA replication, one enzyme is responsible for unwinding the double helix by breaking the hydrogen bonds between the nucleotide base pairs. Which enzyme performs this critical function?

DNA Polymerase
DNA Helicase (Correct answer)
DNA Ligase
RNA Polymerase

Correct answer: DNA Helicase

DNA Helicase is the enzyme that 'unzips' the two strands of the DNA double helix, creating the replication fork where replication can begin. DNA Polymerase then synthesizes the new strands, and DNA Ligase joins fragments together.

Question 73: What is the IUPAC name for the compound CH3CH2CH2OH?

1-Butanol
1-Propanol (Correct answer)
Propanol
Ethanol

Correct answer: 1-Propanol

CH3CH2CH2OH has a 3-carbon chain (prop-) with the hydroxyl group on carbon 1, so it is named 1-propanol.

Question 74: In an addition reaction involving an alkene, which bond is broken to allow new groups to add?

Single C-C sigma bond
C-H bond
C=C pi (double) bond (Correct answer)
C-O bond

Correct answer: C=C pi (double) bond

The pi bond of the C=C double bond breaks during addition reactions, allowing new atoms or groups to bond across what was the double bond.

Question 75: Which of the following best describes the primary outcome of meiosis?

Four diploid cells that are genetically different from the parent cell.
Two haploid cells that are genetically identical to the parent cell.
Four haploid cells that are genetically different from the parent cell. (Correct answer)
Two diploid cells that are genetically identical to the parent cell.

Correct answer: Four haploid cells that are genetically different from the parent cell.

Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell and from each other. This is in contrast to mitosis, which produces two genetically identical diploid cells.

Question 76: Which of the following sentences is a run-on sentence?

Gingivitis is reversible with professional treatment and good home care, but periodontitis involves bone loss and is not reversible.
The patient was anxious about the procedure he had never had a deep cleaning before. (Correct answer)
Although the child was nervous at first, the dental hygienist quickly put him at ease.
Fluoride helps prevent cavities; therefore, it is often included in toothpaste and mouthwash.

Correct answer: The patient was anxious about the procedure he had never had a deep cleaning before.

This is a run-on sentence, specifically a comma splice error. It incorrectly joins two independent clauses ('The patient was anxious about the procedure' and 'he had never had a deep cleaning before') with only a space. These clauses should be joined by a comma and a coordinating conjunction (e.g., ', for'), a semicolon (';'), or be made into two separate sentences.

Question 77: Enantiomers are best described as stereoisomers that are:

Constitutional isomers with the same boiling point
Non-superimposable mirror images of each other (Correct answer)
Identical in all chemical and physical properties
Geometric isomers that differ only in rotation

Correct answer: Non-superimposable mirror images of each other

Enantiomers are non-superimposable mirror images of one another, differing in how they rotate plane-polarized light but otherwise sharing identical physical properties in achiral environments.

Question 78: A text on periodontal disease states: "The inflammatory response to subgingival bacteria can lead to the degradation of periodontal tissues, including the ligament and alveolar bone. This process is often insidious, with minimal symptoms in its early stages, progressing silently until significant attachment loss has occurred." What is the meaning of the word "insidious" as used in this context?

Proceeding in a gradual, subtle way, but with harmful effects. (Correct answer)
Easily treatable with common antibiotics.
Rapid and painful.
Caused by a virus.

Correct answer: Proceeding in a gradual, subtle way, but with harmful effects.

The context clues 'minimal symptoms in its early stages' and 'progressing silently' point to the meaning of insidious. The process is gradual and subtle, yet it results in the harmful effect of 'significant attachment loss.' The other options are contradicted by the description in the passage.

Question 79: Which class of organic compounds contains a carbonyl group (C=O) with at least one hydrogen directly bonded to the carbonyl carbon?

Ketones
Carboxylic acids
Esters
Aldehydes (Correct answer)

Correct answer: Aldehydes

Aldehydes (R-CHO) have the carbonyl carbon bonded to at least one hydrogen, distinguishing them from ketones where the carbonyl is flanked by two carbon groups.

Question 80: The critical pH for enamel demineralization is approximately 5.5. A patient consumes a beverage with a hydronium ion [H₃O⁺] concentration of 1.0 x 10⁻⁴ M. What is the pH of this beverage, and what is its likely effect on tooth enamel?

pH = 10; Remineralizing
pH = 4; Demineralizing (Correct answer)
pH = 10; Demineralizing
pH = 4; Remineralizing

Correct answer: pH = 4; Demineralizing

The pH of a solution is calculated as the negative logarithm of the hydronium ion concentration (pH = -log[H₃O⁺]). For this beverage, pH = -log(1.0 x 10⁻⁴) = 4.0. Since a pH of 4.0 is more acidic than the critical pH of 5.5, it will cause the demineralization of tooth enamel.

Question 81: Which organelle is responsible for cellular respiration?

Mitochondrion (Correct answer)
Ribosome
Endoplasmic reticulum
Nucleus

Correct answer: Mitochondrion

Explanation: The mitochondrion is responsible for cellular respiration, a process that produces ATP (adenosine triphosphate), the cell's main energy currency. Within the mitochondria, various enzymes and metabolic pathways convert glucose and oxygen into ATP through a series of biochemical reactions. This process provides energy for cellular activities and is essential for the survival and functioning of eukaryotic cells.

Question 82: Which three components make up a nucleotide?

A phosphate group, pentose sugar, and nitrogenous base (Correct answer)
An amino acid, ribose, and adenine
A fatty acid, glycerol, and phosphate
A purine, pyrimidine, and deoxyribose

Correct answer: A phosphate group, pentose sugar, and nitrogenous base

A nucleotide is composed of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base — the monomeric building blocks of DNA and RNA.

Question 83: Which organ system is primarily responsible for regulating body temperature, fluid balance, and protection against pathogens?

Respiratory system
Integumentary system (Correct answer)
Urinary system
Digestive system

Correct answer: Integumentary system

The integumentary system (skin, hair, nails, glands) regulates body temperature, prevents water loss, and acts as the first line of defense.

Question 84: Phosphoric acid (H₃PO₄) is used in dentistry to etch tooth enamel, while calcium hydroxide (Ca(OH)₂) can be used as a pulp-capping agent. Which of the following are the correct products of the neutralization reaction between these two compounds?

Calcium phosphide and hydrogen gas
Calcium perchlorate and water
Calcium phosphite and hydrogen peroxide
Calcium phosphate and dihydrogen monoxide (Correct answer)

Correct answer: Calcium phosphate and dihydrogen monoxide

This is a double replacement and neutralization reaction. The calcium (Ca²⁺) from the base combines with the phosphate (PO₄³⁻) from the acid to form the salt calcium phosphate (Ca₃(PO₄)₂). The hydrogen (H⁺) from the acid combines with the hydroxide (OH⁻) from the base to form water (H₂O), also known as dihydrogen monoxide. The balanced equation is 2H₃PO₄ + 3Ca(OH)₂ → Ca₃(PO₄)₂ + 6H₂O.

Question 85: Read the following sentence: 'Each of the dental hygiene students are required to bring their own set of instruments.' Which of the following revisions corrects the grammatical error in the sentence?

Each of the dental hygiene students are required to bring his or her own set of instruments.
No correction is needed.
Each of the dental hygiene students is required to bring their own set of instruments.
Each of the dental hygiene students is required to bring his or her own set of instruments. (Correct answer)

Correct answer: Each of the dental hygiene students is required to bring his or her own set of instruments.

The subject of the sentence is 'Each,' which is singular. Therefore, the verb must also be singular ('is required'). Additionally, the pronoun must agree with the singular subject; 'his or her' is the grammatically correct singular pronoun to use in this formal context. 'Their' is a plural pronoun.

Question 86: An excerpt from a scientific journal reads: "While the mechanical removal of plaque via toothbrushing is effective, studies indicate that the topography of the bristles plays a role. End-rounded bristles are generally recommended as they are less abrasive to gingival tissue and tooth enamel compared to flat-cut, angular bristles. However, the ultimate efficacy of any manual toothbrush is overwhelmingly dependent on the user's technique and duration of brushing." What can be inferred from this passage about choosing a toothbrush?

A toothbrush with angular bristles is the most effective for plaque removal.
Brushing technique is more important than the type of bristle. (Correct answer)
End-rounded bristles are the only type that should be used.
All manual toothbrushes are equally effective regardless of use.

Correct answer: Brushing technique is more important than the type of bristle.

The passage states that end-rounded bristles are 'less abrasive' but concludes that 'the ultimate efficacy...is overwhelmingly dependent on the user's technique and duration.' This implies that while bristle type has some effect (on abrasion), proper use is the most critical factor for effectiveness, making technique more important.

Question 87: Which organelle is known as the 'powerhouse of the cell' because it produces ATP through cellular respiration?

Golgi apparatus
Endoplasmic reticulum
Ribosome
Mitochondria (Correct answer)

Correct answer: Mitochondria

Mitochondria carry out oxidative phosphorylation to produce the majority of ATP used by the cell.

Question 88: Rank the following angles from smallest to largest.

C, A, D, B (Correct answer)
B, D, A, C
C, D, A, B
A, C, D, B

Correct answer: C, A, D, B

Angle C is the most acute (smallest). Angle A is slightly larger than C. Angle D is larger still, approaching a right angle. Angle B is the most obtuse (largest) of the four. Therefore, the correct order from smallest to largest is C, A, D, B.

Question 89: A sample containing helium gas at 0.20 atm compresses so that its volume is halved at a constant temperature. What is the new pressure in atmospheres?

0.10
0.20
0.40 (Correct answer)
0.80

Correct answer: 0.40

Explanation: When a gas is compressed at a constant temperature, its pressure increases inversely to the volume. So, if the volume is halved, the pressure doubles. In this case, if the initial pressure is 0.20 atm and the volume is halved, the new pressure becomes 0.40 atm, as the pressure doubles when the volume is halved.

Question 90: A dental hygienist measures six periodontal pocket depths around a specific molar, recording the following values in millimeters: 3, 2, 4, 5, 3, 1. What is the mean (average) pocket depth for this tooth?

3 mm (Correct answer)
3.5 mm
4 mm
18 mm

Correct answer: 3 mm

The mean is calculated by summing all the measurements and dividing by the number of measurements. The sum is 3 + 2 + 4 + 5 + 3 + 1 = 18 mm. There are 6 measurements, so the mean is 18 mm / 6 = 3 mm.

Question 91: Many pathogenic bacteria that contribute to periodontal disease thrive in the low-oxygen environment of subgingival pockets. These bacteria primarily generate energy through which metabolic process?

Anaerobic respiration (Correct answer)
Aerobic respiration
Photosynthesis
Chemosynthesis

Correct answer: Anaerobic respiration

Anaerobic respiration is a form of cellular respiration that generates energy in the absence of oxygen. This process is characteristic of obligate and facultative anaerobes that colonize deep periodontal pockets where oxygen is scarce.

Question 92: A dental hygienist mixes a 2% fluoride solution with a 10% fluoride solution to create 80 ml of a 5% fluoride solution. How many milliliters of the 10% solution are needed?

30 ml (Correct answer)
50 ml
20 ml
60 ml

Correct answer: 30 ml

Let x be the amount of the 2% solution and y be the amount of the 10% solution. The two equations are x + y = 80 (total volume) and 0.02x + 0.10y = 0.05 * 80 (total fluoride amount). From the first equation, x = 80 - y. Substitute this into the second equation: 0.02(80 - y) + 0.10y = 4. This simplifies to 1.6 - 0.02y + 0.10y = 4. Then, 0.08y = 2.4. Solving for y gives y = 30 ml.

Question 93: In the mouth, salivary amylase is an enzyme that accelerates the breakdown of complex carbohydrates (starch) into simpler sugars. What is the role of salivary amylase in this chemical reaction?

A product
An inhibitor
A reactant
A catalyst (Correct answer)

Correct answer: A catalyst

Salivary amylase acts as a biological catalyst. A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Enzymes are proteins that serve as catalysts in biological systems.

Question 94: Which type of RNA binds an amino acid and carries it to the ribosome?

Transfer (Correct answer)
Small nuclear
Ribosomal
Messenger

Correct answer: Transfer

Explanation: Transfer RNA (tRNA) is the type of RNA that binds to specific amino acids and carries them to the ribosome during protein synthesis. Each tRNA molecule has an anticodon region that recognizes a specific codon on the mRNA (messenger RNA) and an attachment site for a specific amino acid. This allows tRNA to "translate" the information encoded in the mRNA into the corresponding sequence of amino acids in the growing polypeptide chain at the ribosome.

Question 95: Stereoisomers have the same molecular formula and connectivity but differ in:

The spatial arrangement of atoms (Correct answer)
The number of carbon atoms
The types of functional groups present
The molecular weight

Correct answer: The spatial arrangement of atoms

Stereoisomers share identical molecular formulas and bond connectivity but differ in the three-dimensional arrangement of their atoms in space.

Question 96: What is the surface area of a cube with an edge length of 3 inches?

81 in²
54 in² (Correct answer)
9 in²
27 in²

Correct answer: 54 in²

A cube has 6 faces; surface area = 6 × s² = 6 × 3² = 6 × 9 = 54 in².

Question 97: Which of the following best describes the primary role of enzymes in biological reactions?

To serve as the primary source of cellular energy.
To store and transmit genetic information.
To provide structural support to cell membranes.
To act as catalysts that increase the rate of reactions. (Correct answer)

Correct answer: To act as catalysts that increase the rate of reactions.

Enzymes are biological catalysts that lower the activation energy required for a chemical reaction to proceed. This significantly speeds up the rate at which the reaction occurs without the enzyme being consumed in the process.

Question 98: A sarcomere is the basic functional unit of which type of tissue?

Nervous tissue
Connective tissue
Smooth muscle only
Cardiac and skeletal muscle (Correct answer)

Correct answer: Cardiac and skeletal muscle

Sarcomeres are repeating contractile units found in striated (skeletal and cardiac) muscle fibers, bounded by Z-lines.

Question 99: What is the major function of the Golgi apparatus?

Translating messenger RNA into protein
Replicating chromosomal DNA
Making steroid hormones
Sorting secretory and membrane proteins (Correct answer)

Correct answer: Sorting secretory and membrane proteins

Explanation: The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids into vesicles for delivery to targeted destinations within or outside the cell. This includes sorting secretory proteins destined for secretion outside the cell and membrane proteins that are integrated into the cell membrane or other cellular compartments.

Question 100: In the geometric shape below, four interior angles are indicated. Which of the labeled angles is the smallest?

Angle B (Correct answer)
Angle C
Angle D
Angle A

Correct answer: Angle B

By inspecting the four labeled angles within the shape, Angle B is the most acute or 'sharpest' corner. Angle C is a right angle (90 degrees). Angles A and D are both obtuse, making them significantly larger than Angle B.

Question 101: From the options provided, identify the largest angle.

Angle D
Angle C
Angle A (Correct answer)
Angle B

Correct answer: Angle A

The largest angle is the one that is most open or obtuse. Comparing the four options, Angle A is clearly the most open, extending well beyond a 90-degree right angle. Angles B, C, and D are all acute angles, making them smaller than A.

Question 102: When she was younger. She went to the museum and saw the exhibit of reconstructed blue whale skeletons. Which option best combines these sentences?

She went to the museum and saw the exhibit when she was younger of reconstructed blue whale skeletons.
When she was younger, she went to the museum and saw the exhibit of reconstructed blue whale skeletons. (Correct answer)
She went to the museum and saw the exhibit of reconstructed blue whale skeletons. When she was younger.
She went to the museum and saw the exhibit of reconstructed blue whale skeletons, when she was younger.

Correct answer: When she was younger, she went to the museum and saw the exhibit of reconstructed blue whale skeletons.

Explanation: This option combines the two sentences in a clear and grammatically correct manner, providing the necessary context at the beginning of the sentence.

Question 103: Which best describes the main idea of this paragraph: The first human mission to the bottom of the trench was in 1960, when engineer Jacques Piccard and submariner Don Walsh descended in a deep sea submersible called the Trieste. It was 52 years before the second descent, by Titanic filmmaker James Cameron. In 2019 and 2020, explorer Victor Vescovo and various companions braved the gloomy depths five times. Having previously climbed to the summit of Mt. Everest, Vescovo and his companion Vanessa O’Brien have achieved the remarkable distinction of reaching both the highest and the lowest points on the planet. Another companion has accomplished a different singular feat. Kathy Sullivan is a former astronaut who walked in space in 1984. As an explorer of both oceanic depths and extraterrestrial heights, she has contemplated the earthly sphere from afar and probed its deepest inner recess.

The Mariana Trench is of interest to both geologists and oceanographers.
Most people who explore the Mariana Trench are motivated by curiosity.
Explorers of the Mariana Trench are a daring and accomplished group. (Correct answer)
Those who explore the Mariana Trench are honored internationally.

Correct answer: Explorers of the Mariana Trench are a daring and accomplished group.

Explanation: The paragraph highlights the notable achievements and bravery of the individuals who have descended into the Mariana Trench, emphasizing their remarkable distinctions and accomplishments. This aligns with the main idea that these explorers are a daring and accomplished group.

Question 104: A reversible hydrocolloid impression material is heated to become a liquid and then cooled in a tray to become a semisolid gel in the patient's mouth. The physical process of changing from a liquid state to a solid state is called:

Solidification (or Freezing) (Correct answer)
Evaporation
Condensation
Sublimation

Correct answer: Solidification (or Freezing)

Solidification, also commonly known as freezing, is the phase transition in which a substance changes from a liquid to a solid. Sublimation is solid to gas, condensation is gas to liquid, and evaporation is liquid to gas.

Question 105: The valleys, on the other hand, present daunting challenges—submerged under oceans, many of these valleys remain elusive to all but a tiny number of daring, highly motivated explorers. What is the meaning of the word “daunting” as it is used in this sentence?

Foreseeable
Mundane
Mysterious
Formidable (Correct answer)

Correct answer: Formidable

Explanation: The word "daunting" means intimidating or challenging, suggesting something that is difficult to overcome. "Formidable" is a synonym that conveys a similar meaning, indicating something that inspires fear or respect due to its size, power, or difficulty. In this context, "daunting challenges" refers to the difficult and intimidating nature of exploring the submerged valleys.

Question 106: An isosceles triangle has:

No sides equal
Exactly two sides equal (Correct answer)
One right angle
All three sides equal

Correct answer: Exactly two sides equal

An isosceles triangle has exactly two congruent (equal-length) sides and the base angles opposite those sides are also equal.

Question 107: A line segment has endpoints at coordinates (1, 2) and (4, 6). What is the length of the segment?

4 units
7 units
5 units (Correct answer)
3 units

Correct answer: 5 units

Distance = √[(4−1)² + (6−2)²] = √[9 + 16] = √25 = 5 units.

Question 108: A dental hygienist is examining the angulation of different periodontal probes. Which of the following instruments shows the largest angle?

Instrument A
Instrument C
Instrument B
Instrument D (Correct answer)

Correct answer: Instrument D

By visually comparing the four angles, Angle D is the most open, making it the largest (most obtuse) angle among the choices. Angle A is the smallest, followed by C, then B, with D being the largest.

Question 109: Which functional group is characteristic of an alcohol?

Carboxyl (-COOH)
Carbonyl (C=O)
Amino (-NH2)
Hydroxyl (-OH) (Correct answer)

Correct answer: Hydroxyl (-OH)

Alcohols are defined by the hydroxyl (-OH) functional group attached directly to a carbon atom.

Question 110: The number of bacteria in a culture triples every 4 hours. If the initial number of bacteria is B, what is the expression that represents the number of bacteria after 24 hours?

B * 3^4
B * 3^6 (Correct answer)
B * 3^24
B * (3*6)

Correct answer: B * 3^6

The bacteria triples every 4 hours. In a 24-hour period, this tripling event occurs 24 / 4 = 6 times. Therefore, the initial number of bacteria, B, must be multiplied by 3 six times. This is represented by the exponential expression B * 3^6.

Question 111: Which of the following is a noble gas?

Fluorine
Oxygen
Nitrogen
Helium (Correct answer)

Correct answer: Helium

Explanation: Helium is a noble gas. Noble gases are a group of chemical elements characterized by their low reactivity under normal conditions. They are found in group 18 of the periodic table and include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Noble gases have full valence electron shells, making them stable and unreactive with other elements. Helium, specifically, is the second lightest and second most abundant element in the universe, commonly used in balloons, airships, and cryogenic applications.

Question 112: What is the circumference of a circle with a diameter of 10 cm? (Use π ≈ 3.14)

15.7 cm
78.5 cm
314 cm
31.4 cm (Correct answer)

Correct answer: 31.4 cm

Circumference = π × d = 3.14 × 10 = 31.4 cm.

Question 113: What are the products when a carboxylic acid reacts with an alcohol in the presence of an acid catalyst?

An ester and water (Correct answer)
An aldehyde and water
A ketone and hydrogen gas
An ether and carbon dioxide

Correct answer: An ester and water

Esterification is the condensation reaction between a carboxylic acid and an alcohol, yielding an ester and water as products.

Question 114: An object is constructed from identical, stacked cubes. No cubes are floating. The structure has a base that is 3 columns wide and 2 rows deep. The front-left column is 3 cubes high. The front-middle column is 2 cubes high. The front-right column is 1 cube high. The entire back row of columns is 1 cube high. How many total cubes are in the object?

9
12
10
11 (Correct answer)

Correct answer: 11

Calculate the number of cubes in each vertical column and sum them. The leftmost column is 3 cubes high and 2 deep (3 * 2 = 6). The middle column is 2 cubes high and 2 deep (2 * 2 = 4). The rightmost column is 1 cube high and 2 deep (1 * 2 = 2). The total number of cubes is 6 + 4 + 2 = 12.

Question 115: I know the funny story about my sister is true because she told me themselves. How should the word “themselves” be changed?

herselves
herself (Correct answer)
yourself
himself

Correct answer: herself

Explanation: The word "herself" is the correct reflexive pronoun to use when referring to a singular female subject, which in this case is "my sister."

Question 116: Identify the sentence that is grammatically correct and uses parallel structure.

Her duties included taking X-rays, updating patient charts, and the sterilization of instruments.
Proper oral hygiene involves brushing thoroughly, flossing daily, and rinsing with an antiseptic mouthwash. (Correct answer)
To ensure patient comfort, the hygienist will adjust the chair, offer a blanket, and be explaining the procedure.
The dental assistant was responsible for scheduling appointments, patient intake, and to order supplies.

Correct answer: Proper oral hygiene involves brushing thoroughly, flossing daily, and rinsing with an antiseptic mouthwash.

This sentence correctly uses parallel structure by listing three gerund phrases ('brushing thoroughly,' 'flossing daily,' 'rinsing with an antiseptic mouthwash'). The other options mix different grammatical forms (gerunds, infinitives, and nouns) within their lists, violating the rule of parallelism.

Question 117: Which blood vessel carries oxygenated blood away from the heart to the body?

Pulmonary artery
Superior vena cava
Pulmonary vein
Aorta (Correct answer)

Correct answer: Aorta

The aorta is the largest artery in the body, carrying oxygenated blood from the left ventricle to systemic circulation.

Question 118: Fluoride ions (F⁻) strengthen tooth enamel by reacting with hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) to form the more acid-resistant fluorapatite (Ca₁₀(PO₄)₆F₂). Based on the balanced reaction Ca₁₀(PO₄)₆(OH)₂ + 2F⁻ → Ca₁₀(PO₄)₆F₂ + 2OH⁻, what is the stoichiometric mole ratio of hydroxyapatite to fluoride ions?

2:1
1:2 (Correct answer)
10:2
1:1

Correct answer: 1:2

Stoichiometry involves the mole ratios of reactants and products, which are indicated by the coefficients in a balanced chemical equation. In this reaction, the coefficient for hydroxyapatite is an implied 1, and the coefficient for fluoride ions is 2. Therefore, the ratio is 1 mole of hydroxyapatite to 2 moles of fluoride ions.

Question 119: A quality control report measures the fluoride concentration (in parts per million, ppm) in five different batches of city water. The readings are: 0.7 ppm, 1.1 ppm, 0.6 ppm, 0.9 ppm, and 1.2 ppm. What is the range of these fluoride concentrations?

1.2 ppm
0.9 ppm
0.5 ppm
0.6 ppm (Correct answer)

Correct answer: 0.6 ppm

The range is the difference between the highest and lowest values in a data set. The highest value is 1.2 ppm and the lowest value is 0.6 ppm. The range is 1.2 - 0.6 = 0.6 ppm.

Question 120: A dental hygienist is analyzing the ages of patients who received a specific cosmetic procedure in one week. The ages recorded are: 28, 35, 26, 41, 28, 50, 28, 33. Which of the following values represents the mode of this data set?

33.6
24
28 (Correct answer)
30.5

Correct answer: 28

The mode is the value that appears most frequently in a data set. In the given list of ages (28, 35, 26, 41, 28, 50, 28, 33), the age '28' appears three times, which is more often than any other age.

Question 121: Which organelle contains hydrolytic enzymes and is responsible for breaking down cellular waste, debris, and invading pathogens like bacteria?

Lysosome (Correct answer)
Endoplasmic Reticulum
Golgi Apparatus
Peroxisome

Correct answer: Lysosome

Lysosomes are membrane-bound organelles that function as the cell's digestive system. They contain a variety of acid hydrolases capable of breaking down proteins, nucleic acids, lipids, and carbohydrates. They degrade materials taken in from outside the cell and digest obsolete components of the cell itself in a process called autophagy.

Question 122: A study records the number of carious lesions in a group of 8 pediatric patients: 4, 1, 0, 3, 2, 5, 1, 6. What is the median number of carious lesions for this data set?

3
2.5 (Correct answer)
2
2.25

Correct answer: 2.5

To find the median, the data must first be arranged in numerical order: 0, 1, 1, 2, 3, 4, 5, 6. Because there is an even number of data points (8), the median is the average of the two middle values (the 4th and 5th values), which are 2 and 3. The average is (2 + 3) / 2 = 2.5.

Question 123: Hydrogen peroxide (H₂O₂) is used as a whitening agent because it decomposes into water (H₂O) and oxygen gas (O₂). This is a type of redox reaction known as a disproportionation reaction. What does this mean for the oxygen atoms in H₂O₂?

The oxygen atoms are transferred but their oxidation state is unchanged.
The oxygen atoms only undergo oxidation.
The oxygen atoms only undergo reduction.
The oxygen atoms are simultaneously oxidized and reduced. (Correct answer)

Correct answer: The oxygen atoms are simultaneously oxidized and reduced.

In H₂O₂, oxygen has an oxidation state of -1. In the product H₂O, oxygen's oxidation state becomes -2 (a reduction, gain of electrons). In the product O₂, its oxidation state becomes 0 (an oxidation, loss of electrons). Because the oxygen atoms from the same reactant are both oxidized and reduced, this is a disproportionation reaction.

Question 124: To maintain homeostasis, a drop in body temperature in a mammal is generally followed by:

a fever.
decreasing blood flow to the core.
sweating.
shivering. (Correct answer)

Correct answer: shivering.

Explanation: When a mammal experiences a drop in body temperature, one of the primary responses to maintain homeostasis is shivering. Shivering is a physiological mechanism in which rapid muscle contractions generate heat, helping to increase body temperature back to the normal range. This response helps to counteract the decrease in temperature and restore equilibrium within the body.

Question 125: The fundamental principle that requires the number of atoms of each element to be identical on both sides of a chemical equation is known as:

The Law of Conservation of Mass (Correct answer)
Avogadro's Law
The Law of Multiple Proportions
The Law of Definite Proportions

Correct answer: The Law of Conservation of Mass

The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions. Therefore, the mass of the reactants must equal the mass of the products, which is achieved by ensuring the same number of atoms for each element are present on both sides of the equation.

Question 126: Four surfaces of a tooth are represented by the angles below. Which of the angles is the smallest?

Angle A
Angle D
Angle C (Correct answer)
Angle B

Correct answer: Angle C

To find the smallest angle, look for the one that is the most 'closed' or acute. Angle C is visibly narrower than angles A, B, and D. Angle D is the largest, while A and B are intermediate and very close in size, but both are clearly larger than C.

Question 127: The functional unit of the kidney responsible for filtration and urine formation is the:

Nephron (Correct answer)
Glomerulus
Collecting duct
Renal pelvis

Correct answer: Nephron

The nephron is the structural and functional unit of the kidney, consisting of the glomerulus, Bowman's capsule, and tubules.

Question 128: The area of a circle with radius 6 cm is approximately: (Use π ≈ 3.14)

37.68 cm²
226.08 cm²
113.04 cm² (Correct answer)
18.84 cm²

Correct answer: 113.04 cm²

Area of a circle = π × r² = 3.14 × 6² = 3.14 × 36 = 113.04 cm².

Question 129: Solve the following equation for x: (2x + 5) / 3 = 3x - 5

x = -2
x = 10/7
x = 20/7 (Correct answer)
x = 20/11

Correct answer: x = 20/7

To solve the equation, first multiply both sides by 3 to eliminate the denominator: 2x + 5 = 3(3x - 5). Distribute the 3 on the right side: 2x + 5 = 9x - 15. Next, get the x terms on one side by subtracting 2x from both sides: 5 = 7x - 15. Then, add 15 to both sides: 20 = 7x. Finally, divide by 7 to solve for x: x = 20/7.

Question 130: What is the primary function of the chloroplast in plant cells?

Lipid synthesis
Photosynthesis (Correct answer)
Cellular respiration
Protein synthesis

Correct answer: Photosynthesis

Explanation: The chloroplast's primary function in plant cells is photosynthesis, the process by which plants convert light energy into chemical energy in the form of glucose. Chloroplasts contain chlorophyll, a green pigment that captures light energy from the sun. This energy is used to drive the synthesis of glucose from carbon dioxide and water, releasing oxygen as a byproduct. Photosynthesis is vital for the production of organic compounds that sustain plant growth and provide energy for all living organisms.

Question 131: What is the perimeter of a square with a side length of 9 inches?

27 inches
36 inches (Correct answer)
81 inches
18 inches

Correct answer: 36 inches

Perimeter of a square = 4 × side = 4 × 9 = 36 inches.

Question 132: Carbon-12 and Carbon-14 are two isotopes of carbon. Which of the following statements correctly describes the difference between an atom of Carbon-14 and an atom of Carbon-12?

Carbon-14 has two fewer protons than Carbon-12.
Carbon-14 has two more neutrons than Carbon-12. (Correct answer)
Carbon-14 has two more protons than Carbon-12.
Carbon-14 has two more electrons than Carbon-12.

Correct answer: Carbon-14 has two more neutrons than Carbon-12.

Isotopes are atoms of the same element, meaning they have the same number of protons. The number of protons defines the element (Carbon always has 6 protons). The number following the element name (12 or 14) is the mass number (protons + neutrons). Therefore, Carbon-12 has 6 neutrons (12 - 6), and Carbon-14 has 8 neutrons (14 - 6), which is a difference of two neutrons.

Question 133: Four angles are presented for comparison. Angle A is slightly smaller than a right angle. Angle B is a straight line. Angle C is very small and acute. Angle D is clearly obtuse, about halfway between a right angle and a straight line. What is the correct order of the angles from smallest to largest?

C, A, D, B (Correct answer)
A, C, D, B
C, D, A, B
B, D, A, C

Correct answer: C, A, D, B

Ordering by angle type is the first step. Acute angles are smallest, followed by right angles, then obtuse angles, and finally straight angles. Angle C (acute) is the smallest. Angle A (slightly less than 90°) is next. Angle D (obtuse, ~135°) is larger than A. Angle B (a straight line, 180°) is the largest. Thus, the correct order is C, A, D, B.

Question 134: What is the formula for sulfuric acid?

H2SO4 (Correct answer)
NaOH
H2O
HCl

Correct answer: H2SO4

Explanation: Sulfuric acid is represented by the chemical formula H2SO4. It is a strong mineral acid with the chemical formula H2SO4. It is soluble in water at all concentrations, and its aqueous solution is known as "battery acid" or "diluted sulfuric acid." It is one of the most important industrial chemicals, primarily used in the production of fertilizers, explosives, detergents, and various other chemicals.

Question 135: A patient's saliva helps to neutralize acidic byproducts from plaque bacteria. The reaction of an acid (like HCl from stomach reflux) with a base (like NaOH) to produce a salt (NaCl) and water (H₂O) is a classic example of what type of chemical reaction?

Single Replacement
Combustion
Decomposition
Neutralization (Correct answer)

Correct answer: Neutralization

A neutralization reaction is a specific type of double replacement reaction where an acid and a base react to form a salt and water. This process is crucial in the oral cavity for counteracting acids that can lead to enamel erosion.

Question 136: If two angles are supplementary, their measures add up to:

360°
180° (Correct answer)
90°
45°

Correct answer: 180°

Supplementary angles are two angles whose measures sum to 180°, forming a straight line when adjacent.

Question 137: What chemical transformation converts a primary alcohol into an aldehyde?

Reduction
Hydrolysis
Oxidation (Correct answer)
Substitution

Correct answer: Oxidation

Oxidation of a primary alcohol removes two hydrogen atoms, raising the oxidation state of the carbon and producing an aldehyde.

Question 138: The bird watcher saw three cardinals, one male and two females, observing the bird feeder. Which option best clarifies the relationship between ideas?

Observing the bird feeder the bird watcher saw three male and female cardinals.
The bird watcher saw three cardinals observing the bird feeder; one male and two females.
Three cardinals one male and two females saw the bird watcher observing the bird feeder.
While observing the bird feeder, the bird watcher saw one male and two female cardinals. (Correct answer)

Correct answer: While observing the bird feeder, the bird watcher saw one male and two female cardinals.

Explanation: This option clarifies that it was the bird watcher who was observing the bird feeder and seeing the cardinals, making the relationship between the observer and the observed clear.

Question 139: The process of teeth whitening often involves the decomposition of hydrogen peroxide (H₂O₂), which breaks down into water (H₂O) and oxygen gas (O₂). Which of the following correctly balances the chemical equation for this reaction?

2H₂O₂ → 2H₂O + O₂ (Correct answer)
2H₂O₂ → H₂O + 2O₂
H₂O₂ → H₂O + O₂
H₂O₂ → 2H₂O + O₂

Correct answer: 2H₂O₂ → 2H₂O + O₂

To balance the equation, the number of atoms of each element must be the same on both sides. The equation 2H₂O₂ → 2H₂O + O₂ has 4 hydrogen atoms and 4 oxygen atoms on the reactant side, and 4 hydrogen atoms and (2+2)=4 oxygen atoms on the product side, satisfying the Law of Conservation of Mass.

ATDH - Admission Test for Dental Hygiene

The ATDH is administered by the American Dental Association to evaluate prospective dental hygiene students in reading comprehension, language usage, quantitative reasoning, perceptual ability, biology, and general chemistry.

240

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230 min

Time Limit

50%

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