NBDE Exam Part 2
Which field of the dentistry is defined as the science and art of preventing and controlling detank diseases and promoting dental health through organized community efforts?
A primary misconception about dental public health is that its primary objective is the delivery of dental care to low-income persons. Although this is important, the actual delivery of dental care is only one aspect of dental public health. Pediatric Dentistry (choice A) is an age-defined specialty that provides both primary and comprehensive preventive and therapeutic oral health care for infants and children through adolescence, including those with special health care needs. Prosthodontics (choice B) is the dental specialty pertaining to the diagnosis, treatment planning, rehabilitation and maintenance of the oral function, comfort, appearance and health of patients with clinical conditions associated with missing or deficient teeth and/or oral and maxillofacial tissues using biocompatible substitutes. Endodontics (choice C) is the branch of dentistry which is concerned with the morphology, physiology and pathology of the human dental pulp and periradicular tissues Periodontics (choice E) Periodontics is that specialty of dentistry which encompasses the prevention, diagnosis and treatment of diseases of the supporting and surrounding tissues of the teeth or their substitutes and the maintenance of the health, function and esthetics of these structures and tissues. REFERENCE: American Dental Association. http://www.ada.org/en/education-careers/careers-in-dentistry/dental-specialties/specialty-definitions
An 11-year-old girl presents with a maxillary midline diastema of less than 2mm. The patient's mother is concerned about her appearance and asks you to close the space. What is the appropriate management in this situation?
A small midline diastema is not always an indication for orthodontic intervention. It is perfectly normal for an 11-year-old patient to experience some spacing in the maxillary anterior region, since the canines have not yet erupted. It would be prudent to wait for the canines to erupt, and then assess the patient’s situation. It would not be advised to close the space with an appliance (a) because that would require the patient to undergo unnecessary treatment at a cost to the family that is also unnecessary at this stage. Closing the space with composite veneers (c) would also not be advisable because that could impact the eruption of the permanent canines and impede physiological space closure. Further investigation for the cause of a diastema <2mm (d) is generally not indicated since that dimension falls into the category of physiologic diastema and is likely to close with eruption of the canines. If the diastema were greater than 2mm, it would then be advisable to investigate further as to the cause (frenum, mesiodens, cyst) because it would likely NOT close with the eruption of the canines. REFERENCE: Fields, Proffit a. Contemporary Orthodontics, 5th Edition. Mosby, 2013. Chapter 11.
An 85-year-old petite female presents for her recall appointment. She notes that her husband of 55 years died 6 months ago. Since then, she notes she has lost 15 pounds and is having difficulty with decreased appetite. What is the most appropriate step should you take yo aid this patient?
From the description, this patient may be suffering from depression, loneliness, or even an undisclosed medical ailment. It is unclear and beyond the scope of a dentist’s practice to diagnose completely and treat this type of situation. The most prudent course of action would be to refer the patient to her family doctor for a thorough analysis (b). Though the following recommendations may be beneficial, none of them allow for a correct diagnosis of the problem by the suitable health care practitioner: (a) Recommend adding liquid nutritional beverages to her diet (c) Refer her to a registered dietician (e) Give her a copy of the national food guide to healthy eating Finally, it would be inappropriate to congratulate this patient on weight loss (d) since she is exhibiting signs of loneliness and problems with appetite. REFERENCE: Stefanac, Nesbit. Treatment Planning in Dentistry, 2nd Edition. C.V. Mosby, 2007. Chapter 16.
To diagnose periodontal disease, the most important factor is:
The diagnosis of periodontal disease hinges upon the loss of attachment of the teeth. In other words, there must be an indication of epithelial migration of the periodontium. The depth of the pocket or sulcus is therefore paramount. You can have pseudopockets that can cause deep pockets with no attachment loss. The presence of bleeding or pain on probing (A, D) only signifies the presence of inflammation of the gingival tissues. The vitality of the teeth only reveals the presence of a healthy or unhealthy root canal system (B). Finally mobility of the teeth (E) may occur as a result of periodontal bone loss, or it may be a result of occlusal trauma without the presence of bone destruction. Additionally, tooth with moderate attachment loss and pocket depths may NOT exhibit mobility, so the diagnosis of periodontal disease cannot hinge upon the presence of mobility or not. REFERENCE: 1. Newman e al. Carranza's Clinical Periodontology, 11th Edition. Saunders Book Company, 2012. Chapter 31. 2. Rose e al. Periodontics: Medicine, Surgery and Implants. Mosby, 2005. Chapter 2.
Which stage of necrotizing ulcerative gingivitis occurs first?
The stages of NUG occurs as follows: -Stage 1: Necrosis of the tip of the interdental papilla (choice D) -Stage 2: Necrosis of the entire papilla -Stage 3: Necrosis extending to the gingival margin (choice A) -Stage 4: Necrosis extending also to the attached gingiva -Stage 5: Necrosis extending into buccal or labial mucosa -Stage 6: Necrosis exposing alveolar bone (choice B) -Stage 7: Necrosis perforating skin of cheek (choice E) REFERENCE: Newman MG, Takei HH, and Carranza FA. (2002). Carranza’s Clinical Periodontology (9th ed). Philadephia, PA: W.B. Saunders Company
Which disease is characterized by necrosis of the marginal gingival tissue and interdental papillae?
Necrotizing periodontal disease presents as acute inflammation of the gingival and periodontal tissues characterized by necrosis of the marginal gingival tissue and interdental papillae. Clinically, these conditions are often associated with stress or human immunodeficiency virus (HIV) infection. Chronic periodontitis (choice A) is the loss of connective tissue attachment to the tooth. Aggressive periodontitis (choice B) is found in an otherwise clinically healthy patient, has rapid attachment loss and bone destruction, characterized by inconsistent amounts of microbial deposit compared to disease severity, and has a familial aggregation of diseased individuals. Abscesses of the periodontium (choice D) are acute lesions that may result in a very rapid destruction of the periodontal tissues. Periodontal abscesses also may occur in the absence of periodontitis. REFEERENCE: Newman MG, Takei HH, and Carranza FA. (2002). Carranza’s Clinical Periodontology (9th ed). Philadephia, PA: W.B. Saunders Company
An acute apical periodontitis would present as:
Acute apical periodontitis describes pulpal disease that has begun to affect the periradicular tissues. The beginning of apical abscess formation can cause the tooth to feel "long". Pain on biting is due to pulpal inflammation and traumatic occlusion. Chronic apical abscesses would more likely present as incidental findings on radiograph with asymptomatic teeth (b) because of their slow growth. A tooth that is mildly painful on biting (c) would more likely be due to a mildly high filling or mild trauma from chewing hard items. It would also be characteristic of the initial stages of reversible pulpitis. If there were a gingival abscess without tooth findings (d), it would more likely be due to a periodontal condition. REFERENCE: Cohen, Stephen C. Pathways of the Pulp, 9th Edition. C.V. Mosby, Jan 2006. Chapter 2.
Which of the following antihypertensives is known to cause gingival hyperplasia in patients?
calcium channel blockers. Alpha-adrenergic receptor blockers (B) and beta-adrenergic receptor blockers (E) are known to cause tachycardia, nasal congestion and dry mouth. ACE inhibitors (C) can cause cough (common) and/or angioneurotic edema (uncommon) due to increased bradykinin. ATII receptor antagonists (D) may cause dizziness, diarrhea and myalgias. REFERENCE: Mosby’s Review for the NBDE Part II. Mosby Elsevier (2012).
Which of the following drugs is most likely to result in decreased metabolism of opioids that undergo hepatic metabolism?
Most opioids undergo hepatic metabolism, via either phase I or phase II reactions. Phase I reactions involve oxidative and reductive reactions, and are orchestrated by the cytochrome P450 enzyme system. Phase II reactions involve conjugation of the drug to a specific substrate. These reactions produce metabolites that are excreted renally or via the biliary tract. Some metabolites may have active analgesic activity, similar to their parent drug, and in some situations, with added side effects and toxicities. It is important to be aware of common inducers and inhibitors of the cytochrome system, which can decrease and increase duration of action of opioids, respectively. A) Carbamazepine is a CYP3A inducer, and would be less likely to result in decreased metabolism of hepatically-modified opioids. B) Phenytoin is a CYP3A inducer, and would be less likely to result in decreased metabolism of hepatically-modified opioids. C) St. John’s wort is a CYP3A inducer, and would be less likely to result in decreased metabolism of hepatically-modified opioids. D) Rifampicin is a CYP3A inducer, and would be less likely to result in decreased metabolism of hepatically-modified opioids. E) Diltiazem is a CYP3A inhibitor, and would be the most likely drug in the given selection to result in decreased metabolism of hepatically-modified opioids. REFERENCE: Dahan A, Niesters M, Olofsen E, Smith T, Overdyk F. Chapter 19: Opioids. In: Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC, Ortega R. Clinical Anesthesia. 7th ed. Philadelphia: Lippincott Williams & Wilkins; 2013.
A 22-year-old patient with an unrepaired cyanotic congenical heart defect is scheduled for a routine teeth cleaning. The patient is allergc to penicillins. Which of the following should be done with regards to this patient prior to their dental procedure?
Administer oral prophylactic clindamycin. (Choice A) Incorrect answer. In a patient who is allergic to penicillins, but is able to take oral medications, an oral alternative such as cefazolin or clindamycin should be given. (Choice B) Incorrect answer. In a patient who is allergic to penicillins, but is able to take oral medications, an oral alternative such as cefazolin or clindamycin should be given; intravenous administration is not necessary in this patient. (Choice C) Incorrect answer. In a patient who is allergic to penicillins, but is able to take oral medications, an oral alternative such as cefazolin or clindamycin should be given; intravenous administration is not necessary in this patient. (Choice D) Correct answer. In a patient who is allergic to penicillins, but is able to take oral medications, an oral alternative such as cefazolin or clindamycin. (Choice E) Incorrect answer. In a patient who is allergic to penicillins, but is able to take oral medications, an oral alternative such as cefazolin or clindamycin should be given; intravenous administration is not necessary in this patient. (Choice F) Incorrect answer. Patients with unrepaired cyanotic congenital heart defects are at risk for developing bacterial endocarditis, so they should be given prophylactic antibiotics. Typically, oral amoxicillin is given, but in a patient who is allergic to penicillins and able to take oral medications, an oral alternative such as cefazolin or clindamycin should be given. REFERENCE: Clinical Affairs Committee of the American Academy of Pediatric Dentistry. (2014). Guideline on antibiotic prophylaxis for dental patients at risk for infection. Reference Manual, 36(6), pp. 287 - 291. Nishimura, R. A., Otto C. M., Borrow, R. O., Carabello, B. A., Erwin, J. P., … & Thomas, J. D. (2014). 2014 AHA/ACC guideline for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines. Journal of the American College of Cardiology, 63(22), pp. e57 - e185.
Studies show that a minimal amount of ferrule is necessary for an endodontically treated tooth that is also treated with a dowel in order to prevent fracture by te dowel. What is the minimum ferrule needed?
The placement of a dowel for added retention of the core and crown adds additional stress to the tooth and may increase the risk of fracture to the tooth. As much coronal tooth structure as possible should be retained when preparing pulpless teeth for complete crowns to maximize the ferrule effect. A minimal height of 1.5 to 2 mm (C) of intact tooth structure above the crown margin for 360 degrees around the circumference of the tooth preparation appears to be a rational guideline for this ferrule effect. Surgical crown lengthening or orthodontic extrusion should be considered with severely damaged teeth to expose additional tooth structure to establish a ferrule. REFERENCE: Morgano, S. M. and Brackett, S. E.: Foundation restorations in fixed prosthodontics: Current knowledge and future needs. J Prosthet Dent 1999; 82: 643-657.
For a short clinical crown, what would be the greatest advantages to adding buccal grooves to the preparation?
Resistance (choice C) is defined as the prevention of dislodgment of a restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces. Often abutment teeth with short or wide clinical crowns are more susceptible to tipping forces. The length of the axial walls of the preparation must be great enough to interfere with the arc of the restoration as it pivots on a point on the opposite side of the tooth. If the axial wall is too short it will not interfere with the arc of the casting and will not add any mechanical force to prevent tipping. A wide crown will have a larger arc which will be less likely to have resistance during tipping forces. Walls that are over tapered will also not interfere with the crown as it tips. Grooves add axial walls that are closer to the pivot point where the arc of rotation is much smaller. This causes increased interference during tipping and thus greater resistance. The remaining choices (A, B, D, and E) may be increased by adding grooves but will not be affected as much as resistance form. REFERENCE: Herbert T. Shillingburg, Suniya hobo, Lowell D. Whitsett, Richard Jacobi, Susan E. Brackett. Fundamentals of fixed Prosthodontics, Third Edition. 1997. Quintessence Publishing. Potts, RG., Shillingburg, H.T., and Duncanson, M.G.: Retention and resistance of preparations for cast restorations. J Prosthet Dent 1980; 43:303-308.
When casting gold in prosthodontics, the portion of the flame used to heat the metal is:
Despite the fact that fewer restorations are being fabricated with metal, especially gold, there are many situations in which gold is utilized as the material of choice. When casting gold, attention must be paid to the casting techniques in order to achieve the best results. A blowpipe flame consists of these zones: 1- mixed zone: colorless, pure gas 2-consumption zone: mixture of gas and air 3-reducing zone: the hottest zone (blue) 4-oxidizing zone: the outer zone (red or orange) The reducing zone is used to melt the alloy as it is the hottest and prevents the formation of oxides. REFERENCE: Shillingburg, Jr HT, Hobo S, Whitsett LD, Jacobi R, Bracket SE, Fundamentals of Fixed Prosthodontics, 3rd ed. Chicago; Quintessence, 1997; P 373
Which type of margin is usually situated on hard enamel and is a preferred choice whenever possible when prepping a crown?
Supragingival margins are easier to prepare accurately without trauma to the tissues. They can usually be situated on hard enamel, whereas subgingival margins are often on dentin or cementum. In addition, supragingival margins can be finished without associated soft-tissue trauma and kept plaque free more easily. Impressions of supragingival margins are also made more easily with less potential soft tissue damage. In addition, restorations can be easily evaluated at the time of placement or recall. Subgingival margins (choice B) may be justified when dental caries, cervical erosion, or restorations extend subgingivally, and a crown-lengthening procedure is not indicated. If the proximal contact area extends into the gingival crest or more retention or resistance is needed, then a subgingival margin may be indicated. Equigingival margins (choice C) are preferred over subgingival margins, but not preferred over supragingival margins. Equigingival margins are easier to clean than subgingival margins. REFERENCE: Rosensteil, S. F., Land, M. F., & Fujimoto, J. (2006). Contemporary Fixed Prosthodontics (4 Ed.). St. Louis, Missouri:Mosby Elsevier
Composite resin restorations may use cavity liners for the purpose of:
The main purpose of using a liner or base underneath a composite resin is to minimize irritation to the pulp. Composite resins do not need to be protected from dentinal fluid (a). The process of etching and bonding prepares the tooth surface adequately for resin placement. The adhesion of composite to tooth structure is already sufficient and placing a liner or base does NOT improve it (c). The translucency of the composite (d) again is NOT affected by placement of a liner or base. REFERENCE: Roberson, Theodore. Sturdevant's Art and Science of Operative Dentistry, 5th Edition. C.V. Mosby, 2006. Chapter 11.
A smear biopsy reveals a large, tangled mass of gram-positive hyphae. What would be your diagnosis?
The presence of hyphae is diagnostic for a candidal infection or thrush. Most often the actual cells of the yeast are minimal, however the large number of hyphae is sufficient to produce the diagnosis. The remaining answer options contain bacterial species. A smear biopsy is generally not used for cytological examination of bacterial species. Generally, this type of biopsy or evaluation is used for candida or viral (e.g. herpes) type infections. An exception to this may be Trepomena infections (syphilis). Sometimes a smear is used to demonstrate the presence of such organisms quickly. REFERENCE: 1. Cawson, R. A. Cawson's Essentials of Oral Pathology and Oral Medicine E-Book, 8th Edition. Churchill Livingstone, 2012-02-16. Chapter 12. 2. Neville e al. Oral and Maxillofacial Pathology, 3rd Edition. W.B. Saunders Company, 2008. Chapters 5 & 7.
A patient presents with a white lesions on his buccal mucosa. The lesion is 4mm x 4mm in size and has been present in the patient's mouth for 4 months. Last week it became ulcerated and prompted the patient to see you. What would appropriate management entail?
Excisional biopsies are generally warranted for lesions smaller than 1 centimeter in diameter, and may be performed as definitive treatment for such lesions. Also, excisional biopsies remove an additional 2-3mm border of tissue around the lesion itself. This is determined by the suspected diagnosis. If a malignancy is suspected a wider perimeter may be taken. Because this patient exhibits a lesion that has been present for over two weeks and has recently become ulcerated, suspicion of malignancy would be quite high. As the dimensions remain less than 1 centimeter in diameter, an excisional biopsy would serve this patient well. Needle biopsies (A), or aspiration biopsy, are more frequently done to determine if a lesion contains fluid. There is no indication from the description given that this patient’s lesion would warrant a needle biopsy. Incisional biopsies (B) should be done for lesions greater than 1 centimeter in diameter. Continued monitoring (D) would be ill advised at this time since the patient has already had the lesion for 4 months. And with the recent changes, the suspicion of malignancy is high. Cytological investigation (E) may be prudent if there was suspicion of a candidal or viral infection. The presentation of this lesion warrants more definitive action than a cytological smear. REFERENCE: Hupp. Contemporary Oral and Maxillofacial Surgery, 5th Edition. Mosby, 2008. Chapter 21.
A patients presents with a mandibular first molar that has a failing root canal. Recurrent decay underneath the crown has caused severe damage to the remaining tooth structure and re-infection of the root canal space. Due to remove the tooth. What nerves would need to be blocked for surgical removal of this tooth?
Though the inferior alveolar nerve is the only nerve for mandibular tooth innervation, several other nerves must also be anaesthetized in order to perform a surgical extraction. The lingual nerve innervates the lingual soft tissue of mandibular teeth. And the long buccal nerve anaesthetizes the buccal soft tissue of the molars and second premolar. Since all of these tissues surround the mandibular first molar, they should all be anesthetized for surgical extractions. The mental nerve block (b, d) only provides anaesthesia to the buccal mucous membranes from the mental foramen to the midline. The cervical branches (c) of cranial nerve VII may rarely provide accessory innervation for some mandibular regions. However, it is not standard to anaesthetize those nerves for tooth extractions. REFERENCE: 1. Hupp. Contemporary Oral and Maxillofacial Surgery, 5th Edition. Mosby, 2008. Chapter 7. 2. Malamed, Stanley. Handbook of Local Anesthesia, 5th Edition. Mosby, 072004. Chapter 14.
Of the following root fracture possibilities, which has the WORST prognosis?
Vertical root fractures present some of the worst problems in diagnosis and treatment. In order to have a good prognosis with a vertical fracture, the tooth segments must not be movable, and the patient must not have any symptoms. All other types of root fractures have fair to poor prognosis and will likely not be helped by endodontic therapy. In most cases, vertical fractures necessitate the complete extraction of the tooth. Coronal horizontal fractures (b) are fractures of the tooth immediately apical to the cemento-enamel junction or within a few millimeters subgingivally. This type of root fracture will most likely necessitate the removal of the coronal fragment (the crown) and the remaining tooth structure is evaluated for restorability. Often it can be root canal treated and restored with a post and crown. Mid-root (c) and apical root fractures (d) both have a more favorable prognosis since the fracture is not connected to the oral environment. Often the body is able to heal each segment once the pieces are repositioned. Additionally, if the coronal portion of the root becomes non-vital, endodontic treatment of that segment will often be sufficient. It is extremely rare that the apical segment would lose vitality and require endodontic therapy. REFERENCE: Hargreaves, Cohen. Cohen's Pathways of the Pulp, 10th Edition. Mosby, 2011. Chapters 1, 17, 18.
You are performing endodontic therapy on an upper first molar, and a file is broken in the distobuccal canal. On radiograph, you discover the fragment is 2.5mm long and is wedged tightly in the apical portion of the root, but not extruding past the foramen. What should you do?
In this case, the piece of separated file is located at the apex of the tooth and wedged tightly in the canal. Because of this, it would be extremely difficult to remove the segment without possibly fracturing the root and necessitating extraction. Completing the cleaning and shaping coronal to the separated fragment and obturating well would allow the prognosis to be fair. The patient should always be informed of a separated instrument and should be placed on a monitoring schedule. It is not necessary to refer immediately (a) to an endodontist. This may be required in the future if the patient has symptoms, but not at this stage. Since the procedure and obturation are not yet complete, it would not be prudent to jump into surgical treatment (b) before completing standard therapy. Again, an apicoectomy may be warranted down the line if the patient develops symptoms or pathology around the apex. Extracting the tooth (c) would be extreme at this stage since there are still less invasive ways of treating the tooth in question. Extraction would be the last resort once other options are exhausted. REFERENCE: 1. Hargreaves, Cohen. Cohen's Pathways of the Pulp, 10th Edition. Mosby, 2011. Chapter 25. 2. Torabinejad, Mahmoud. Endodontics, 4th Edition. W.B. Saunders Company, 2008. Chapters 18 and 21.
In adolescents, when minor fractures occur to the permanent teeth, it is prudent to use which type of restoration?
In adolescents, tooth, bone and gingival development are not yet complete. When a permanent tooth is fractured, the nerve may be disturbed. Composite restorations are preferred because they restore esthetics and function, but also allow for a more definitive treatment when development has completed. Full coverage crowns (A) are not generally indicated in this scenario because of the incomplete bone, tooth and gingival development. Additionally, if pulpal problems should arise later, it would be better to complete endodontic therapy and then place a crown on the tooth once the patient is fully grown.Amalgam fillings (B) are not esthetic for anterior teeth. Stainless steel crowns (C) are also unesthetic and not indicated for permanent teeth. REFERENCE: Dean, Avery, McDonald. McDonald and Avery Dentistry for the Child and Adolescent, 9th Edition. Mosby, 2011. Page 413.
Which instruments are used for finishing and polishing amalgam?
Steel burs are used for finishing amalgam preparation and restorations (E). In addition, metal finishing strips may be used. Fine white stones (A), plastic finishing strips (B), finishing diamonds (C), and mounted abrasive rubber discs (D) are used for finishing composite restorations. REFERENCE: Kidd EAM, Smith BGN, Watson TF, and Pickard HM. (2003). Pickard’s Manual of Operative Dentistry. (8 Ed.). New York, NY: Oxford University Press
An asymptomatic red patch with or without foacl hyperkeratosis found in the floor of the mouth, lateral tongue or retromolar area is significant because:
Such a presentation is indicative of an erythroplakia (d). This is the most significant because 90% of such lesions are either carcinoma in situ or invasive squamous cell carcinomas. Pyogenic granulomas (a) do present as red lesions, however are usually correlated with pregnancy or traumatic events. They would also not present as a patch, but as a raised bulbous lesion. Patients with psoriasis (b) may present with red lesions with white patches, however they would more likely present on other skin and mucosal areas. They are not the most clinically significant type of red lesion for the locations listed. Kaposi’s sarcoma (c) is clinically significant due to the presence of the HIV virus and clinical manifestation of AIDS. However, the lesion would most likely present itself on the palate and would also contain red and blue macules or nodules. REFERENCE: Regezi e al. Oral Pathology, 6th Edition. W.B. Saunders Company, 2012. Clinical overview.
Which gland do most acinic cell adenocarcinomas occur?
Around 85% of all acinic cell adenocarcinomas occur in the parotid gland, a logical finding because this is the largest gland and one that is composed entirely of serous elements. Most surveys have shown that this neoplasm makes up 1% to 3% of all parotid tumors, although one study showed it represented 8.6% of all parotid tumors. It is much less common in the submandibular gland, which is the site for only 2.7% to 4% of these tumors. About 9% of all acinic cell adenocarcinomas develop in the oral minor salivary glands, with the buccal mucosa, lips, and palate being the most common site. Overall, around 2% to 6.5% of all minor salivary gland tumors are acinic cell adenocarcinomas. REFERENCE: Neville BW, Damm DD, Allen CM, Bouquot JE. (2002). Oral and Maxillofacial Pathology (3rd ed). St. Louis, Missouri: Saunders Elsevier.
Premature loss of a primary maxillary canine would MOST DIRECTLY result in:
The premature loss of a primary canine would most directly result in a shift of the midline towards the affected side. The loss of a canine prematurely would not directly impact the molar relationship bilaterally (a, b). It may impact one side’s molar relationship, but this is unlikely. The loss of the canine would not directly impact crowding in the posterior (c). It may have some influence on the position and eruption of the first premolar, however not as directly as it would influence the midline. REFERENCE: Fields, Proffit a. Contemporary Orthodontics, 5th Edition. Mosby, 2013. Chapters 6 & 12.