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.

Significant adverse outcome of an uncorrected buccally-erupted maxillary canine

 # A significant adverse outcome of an uncorrected buccally-erupted maxillary canine is the potential for root resorption of the:

A. Mandibular Canine

B. Maxillary Central Incisor

C. Maxillary Second Molar

D. Maxillary First Premolar

The correct answer is B. Maxillary Central Incisor

Buccally-erupted maxillary canines, often ectopic in position, can migrate mesially during eruption, exerting direct pressure on the roots of adjacent anterior teeth—most notably the maxillary central incisor—leading to progressive external inflammatory root resorption (up to complete root loss in severe cases). Case reports and radiographic studies document this as a key sequela, with the canine's abnormal path causing odontoclastic activation via sustained physical contact, resulting in mobility, exfoliation, and functional/aesthetic deficits if uncorrected. While lateral incisors are more frequently affected overall in ectopic canines, central incisor involvement is a significant risk in buccal displacements due to the canine's proximal positioning during mixed dentition eruption. In contrast, mandibular canines (A) are unaffected; second molars (C) are distal and unrelated; and first premolars (D) face lower risk from buccal (vs. palatal) ectopia. Early CBCT screening and interceptive orthodontics (e.g., canine guidance) mitigate this potential.

Occlusal feature most frequently associated with the development of abfraction lesions and non-carious cervical lesions

 # Which of the following occlusal features is most frequently associated with the development of abfraction lesions and non-carious cervical lesions?

A. Class II Division 1 with deep overbite

B. Severe Anterior Open Bite

C. Bilateral Posterior Crossbite in CR and CO

D. Non-working side occlusal interferences (mediotrusive contacts)

The correct answer is D. Non-working side occlusal interferences (mediotrusive contacts)

Non-working side occlusal interferences—contacts on the balancing (non-working) side during lateral mandibular excursions (mediotrusive movements)—generate eccentric tensile and compressive stresses that induce cervical tooth flexure, particularly in premolars and molars, promoting microfractures and enamel/dentin loss characteristic of abfraction lesions and NCCLs. Finite element models and clinical studies demonstrate these interferences elevate lesion risk by 2–4 times via sustained shearing forces (up to 50–100 N during excursions), with prevalence up to 70% in affected teeth versus <20% in interference-free occlusions. Elimination via selective grinding often halts progression, confirming causality. In contrast, Class II Division 1 deep overbite (A) primarily causes anterior trauma rather than lateral stress; severe anterior open bite (B) reduces overall occlusal loading; and bilateral posterior crossbite in CR/CO (C) may induce asymmetric forces but lacks the excursive specificity for abfraction predominance.

Benefit of orthodontic treatment in reducing anterior mandibular crowding

 # The benefit of orthodontic treatment in reducing anterior mandibular crowding is often linked to the reduction of Gingival Index scores. This is primarily because proper alignment leads to:

A. A greater volume of keratinized tissue around the incisors

B. A reduction in plaque accumulation and gingival inflammation

C. Increased vascularity and nutrient supply to the PDL

D. Increased resistance to future recession and attachment loss

The correct answer is B. A reduction in plaque accumulation and gingival inflammation

Severe anterior mandibular crowding creates plaque-retentive interproximal and gingival crevices, elevating Gingival Index scores by 1–2 points on average due to chronic low-grade inflammation from bacterial accumulation. Orthodontic alignment (e.g., via archwire sequencing or IPR) enhances self-performed oral hygiene efficacy—reducing plaque index by 25–40% and GI by 0.5–1.0 within 6–12 months, as shown in randomized trials—by facilitating direct bristle/floss access and disrupting biofilm habitats. This direct causal pathway outperforms secondary effects like tissue volume gains (A, minimal post-alignment), PDL vascular changes (C, unrelated to surface inflammation), or recession resistance (D, a downstream periodontal outcome rather than primary GI driver).