Orthodontic Appliance Construction Flashcards
7 cards from real CDT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Orthodontic Appliance Construction flashcards as text
Which wire alloy is preferred for fabricating Adams clasps on removable orthodontic appliances due to its springiness and formability?
Answer: Stainless steel 0.7mm hard wire
Hard stainless steel wire (0.7mm) provides the ideal combination of stiffness and springiness needed for Adams clasps to engage undercuts effectively.
When constructing a Hawley retainer, the labial bow should contact the anterior teeth at which third of the crown?
Answer: Middle third
The labial bow of a Hawley retainer is positioned at the middle third of the anterior crowns to maintain tooth position without impinging on the gingiva.
A palatal expander that uses a jackscrew mechanism and is cemented to molar bands is best described as which appliance type?
Answer: Rapid Palatal Expander (RPE)
A Rapid Palatal Expander (RPE) uses a midline jackscrew bonded or banded to the molars to apply heavy orthopaedic forces that open the mid-palatal suture.
What is the primary purpose of incorporating ball clasps (bullet clasps) into a removable orthodontic appliance?
Answer: To provide retention by engaging embrasures between teeth
Ball clasps engage the interproximal embrasure between adjacent teeth, providing passive retention for the appliance without wrapping around individual teeth.
During acrylic processing of a removable orthodontic appliance, what defect results from too-rapid polymerization caused by excessive heat?
Answer: Voids and porosity
Excessively rapid polymerization generates heat faster than it can dissipate, causing boiling of the monomer and leaving voids and porosity within the acrylic.
Which functional appliance is designed with separate upper and lower acrylic portions connected by guide planes that posture the mandible forward?
Answer: Twin Block appliance
The Twin Block uses interlocking upper and lower acrylic blocks with inclined guide planes that hold the mandible in a forward and downward position during function.
When trimming a stone model for construction of a removable orthodontic appliance, the posterior extent of the baseplate should end where?
Answer: At the junction of the hard and soft palate
The posterior border of the baseplate should terminate at the hard-soft palate junction to avoid impinging on movable soft tissue while maximizing palatal coverage for retention.