A potential iatrogenic adverse consequence of treating maxillary incisor proclination with retraction mechanics is a decrease in the:

 # A potential iatrogenic adverse consequence of treating maxillary incisor proclination with retraction mechanics is a decrease in the:

A. Depth of the nasolabial angle due to soft tissue retraction

B. Vertical height of the alveolar process in the anterior mandible

C. Maxillary incisor root proximity to the nasal floor and palatal cortex

D. Posterior arch width due to transverse forces

The correct answer is C. Maxillary incisor root proximity to the nasal floor and palatal cortex

When maxillary incisors are retracted (moved backward) to correct proclination (forward tipping), the entire tooth structure, including the root, moves posteriorly. The root apices of the maxillary incisors are naturally close to the nasal floor superiorly and the palatal cortical plate posteriorly. Significant retraction, especially with bodily movement or lingual tipping, can push the root apices closer to these anatomical boundaries. This decreased proximity (i.e., the distance becomes smaller) increases the risk of root resorption or fenestration/dehiscence (where the root penetrates the bony plate).

The primary benefit of early (Phase I) correction of a mandibular functional shift is to:

 # The primary benefit of early (Phase I) correction of a mandibular functional shift is to:

A. Improve the patient’s TMJ range of motion in maximal opening

B. Prevent asymmetric growth and irreversible skeletal asymmetry of the mandible

C. Reduce the risk of buccal non carious cervical lesions

D. Avoid extraction of premolar teeth in the permanent dentition

The correct answer is B. Prevent asymmetric growth and irreversible skeletal asymmetry of the mandible

Mandibular functional shifts, typically from unilateral posterior crossbite, cause the mandible to deviate laterally (1–3 mm) into centric occlusion to bypass interferences, altering condylar positioning and asymmetric loading during growth—leading to differential mandibular ramus/fossa remodeling (e.g., 1–2 mm longer body on shifted side) and progressive skeletal asymmetry (chin deviation, facial canting) that becomes increasingly fixed post-puberty. Phase I correction (e.g., rapid maxillary expansion in mixed dentition) eliminates the shift by 80–90%, normalizing condylar growth trajectories and averting these changes in 70% of cases, per longitudinal cephalometric studies. TMJ motion (A) improves secondarily but transiently; NCCL risk (C) relates more to excursive interferences; and extraction avoidance (D) stems from space management, not shift dynamics.

An uncorrected anterior open bite with a tongue thrust habit can lead to an adverse consequence in the dental alveolar complex via a mechanism of:

 # An uncorrected anterior open bite with a tongue thrust habit can lead to an adverse consequence in the dental alveolar complex via a mechanism of:

A. Disruption of the equilibrium between tongue and lip muscle forces

B. Increased risk of periodontal bone loss due to heavy occlusal forces

C. Pathologic attrition of the posterior teeth

D. Skeletal mandibular retrusion

The correct answer is A. Disruption of the equilibrium between tongue and lip muscle forces

In uncorrected anterior open bite with tongue thrust, the aberrant lingual pressure during deglutition and speech exerts a supracrestal force (20–50 N) on the lingual inclines of maxillary and mandibular incisors, overriding the restraining orbicularis oris and mentalis tonicity—resulting in progressive labial flaring, anterior spacing, and failure of spontaneous closure, with alveolar bone remodeling adapting to this disequilibrium (e.g., reduced interradicular bone density via osteoclast activation). This perioral imbalance is the core mechanism for perpetuating the malocclusion in the dental alveolar complex, as confirmed by electromyographic and cephalometric studies showing 70–80% of persistent open bites linked to such habits. Option B misattributes bone loss to occlusal overload (actually reduced anteriorly); C involves posterior supraocclusion but not primary attrition; D relates more to vertical growth patterns than functional thrust.

Primary goal of pre-orthodontic or phase I alignment of severely crowded incisors

 # The primary goal of pre-orthodontic or phase I alignment of severely crowded incisors that are planned for permanent extraction (e.g. premolar) is to:

A. Reduce the risk of post treatment gingival recession

B. Decrease the overall duration of the comprehensive treatment

C. Prevent external apical root resorption of adjacent teeth

D. Align the roots parallel for optimal force distribution during space closure

The correct answer is D. Align the roots parallel for optimal force distribution during space closure

In extraction cases with severe incisor crowding, initial (phase I) alignment using light round NiTi wires uprights and derotates the anterior teeth, paralleling their roots to position the center of resistance (CR) along the retraction force vector—enabling bodily translation rather than uncontrolled tipping during subsequent en masse space closure (e.g., via chain or coil springs). This optimizes biomechanical efficiency, reduces unwanted extrusion or lingual crown tipping (by 50–70% vs. unaligned starts), and enhances overall control, as emphasized in treatment sequencing guidelines. While it secondarily mitigates resorption risk (C) through lighter, more physiologic forces and may shorten total duration (B) by streamlining mechanics, root parallelism is the foundational goal for precise, stable closure in crowded arches.

The benefit of orthodontic correction for a single tooth with infraocclusion is primarily to:

 # The benefit of orthodontic correction for a single tooth with infraocclusion is primarily to:

A. Improve the patient's vertical dimension of occlusion (VDO)

B. Eliminate the need for prosthetic replacement of the tooth

C. Reduce the risk of periodontal bone loss on the adjacent teeth

D. Prevent future TMJ derangement and pain

The correct answer is C. Reduce the risk of periodontal bone loss on the adjacent teeth.

Uncorrected infraocclusion (often from ankylosis) causes compensatory tipping and overeruption of adjacent teeth (e.g., first permanent molar mesially tilting into the space), leading to eccentric occlusal loading, plaque stagnation in tilted contacts, and progressive alveolar bone resorption on those neighbors—up to 1–2 mm loss over 1–2 years if severe. Orthodontic intervention restores occlusal plane integrity, preventing this cascade: studies show it minimizes adjacent tipping by 70–90%, preserving arch length, symmetry, and periodontal health (e.g., stable probing depths <3 mm post-correction vs. 4–5 mm in untreated cases). While preserving the tooth itself (B) is a key goal (avoiding extraction/prosthetics in ~80% of cases), the lit prioritizes averting downstream periodontal/orthodontic sequelae to adjacents as the overriding rationale for early correction, especially in mixed dentition to safeguard permanent successors.

VDO tweaks (A) are minimal/secondary, and TMJ links (D) are unsubstantiated.

Adverse consequence of malocclusion with the highest correlation with a patient's socio-economic status

 # Which adverse consequence of malocclusion has the highest correlation with a patient's socio-economic status and access to dental care, rather than the malocclusion's severity alone?

A. Functional lateral mandibular shift

B. Increased risk of incisor trauma

C. Pathologic attrition leading to dentin exposure

D. Early and severe development of dental caries

The correct answer is D. Early and severe development of dental caries

Crowding and irregular alignment in malocclusion create plaque-retentive areas that hinder effective oral hygiene, elevating caries risk by 1.5–2.5 times, but this consequence is disproportionately amplified in lower socioeconomic status (SES) populations due to confounding factors like high-sugar diets, limited fluoride exposure, infrequent professional cleanings, and poor access to preventive care—resulting in DMFT scores 20–50% higher in low-SES groups regardless of malocclusion severity alone. Cross-sectional studies in vulnerable cohorts (e.g., refugees) confirm that while malocclusion traits like IOTN grades 3–5 correlate with poorer OHI-S (P<0.001), the caries burden (e.g., 92% prevalence, SiC=8) is exacerbated by SES-driven barriers, with systematic reviews showing inverse SES-caries gradients (lower SES: DMFT ~3.05 vs. upper ~3.1, but prevalence up to 2x higher). In contrast, functional shifts (A) and attrition (C) are primarily biomechanical and severity-dependent with minimal SES modulation; incisor trauma (B) shows inconsistent or null SES associations (e.g., higher in educated mothers, P=0.03, but no income link).

Benefit of orthodontic-surgical correction of a severe skeletal Class III

 # The benefit of orthodontic-surgical correction of a severe skeletal Class III is the ANB change. This change is best described as a combination of a surgically induced forward change in SNA and a:

A. Surgically-induced forward change in SNB

B. Vertical increase in posterior facial height

C. Surgically-induced backward change in SNB

D. Orthodontically-induced posterior dental rotation

The correct answer is C. Surgically-induced backward change in SNB

In severe skeletal Class III malocclusion, bimaxillary orthognathic surgery typically combines Le Fort I maxillary advancement (increasing SNA by 3–6 mm forward positioning) with bilateral sagittal split osteotomy (BSSO) mandibular setback (reducing SNB by 4–8 mm posteriorly), yielding a net ANB increase of 4–7° for Class I stability. Cephalometric studies confirm this dual skeletal adjustment as the primary mechanism for profile normalization and airway enhancement, with mandibular setback countering inherent prognathism without solely relying on maxillary protraction (which risks relapse). Vertical height changes (B) address secondary open bite but minimally impact ANB; forward SNB (A) would exacerbate discrepancy; and dental rotations (D) are pre-surgical adjuncts, not core to skeletal ANB gains.