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).

Key adverse consequence of uncorrected severe Class III malocclusion during adolescence

 # A key adverse consequence of uncorrected severe Class III malocclusion during adolescence is often an exacerbated negative self-perception primarily due to:

A. The convex profile resulting from the mandibular retrusion

B. Difficulty with mandibular posture and chewing

C. Increased risk of dental trauma to the mandibular incisors

D. The ‘dish face’ concave facial profile with prominent chin (prognathism)

The correct answer is D. The ‘dish face’ concave facial profile with prominent chin (prognathism)

Severe Class III malocclusion in adolescents often manifests as a concave "dish face" profile due to mandibular prognathism or relative maxillary retrusion, creating a prominent chin and retruded midface that deviates markedly from ethnic norms of facial harmony—leading to heightened self-consciousness, bullying, and diminished self-esteem as measured by tools like the Orthognathic Quality of Life Questionnaire (OQLQ), with scores 20–40% lower in untreated cases. Longitudinal psychosocial studies confirm this aesthetic distortion as the primary driver of negative self-perception (effect size d=0.8–1.2), surpassing functional concerns, unlike the convex profile in Class II (A, reversed etiology) or trauma risks more pronounced in protrusive uppers (C).

Malocclusion with highest risk for root resorption of the maxillary incisors

 # Which specific malocclusion, due to its inherent nature, presents the highest mechanical risk for palatal root resorption of the maxillary incisors during orthodontic alignment?

A. Skeletal Class III with severe reverse overjet

B. Deep Bite Class I with severe mandibular crowding

C. Impacting a maxillary canine horizontally near the central incisor root

D. Severe Class II Division 1

The correct answer is D. Severe Class II Division 1

In severe Class II Division 1 malocclusion, the proclined maxillary incisors necessitate substantial labial-to-lingual retraction during alignment (typically 4–7 mm bodily movement), which approximates the incisor roots to the lingual (palatal) cortical plate—reducing the root-to-cortex distance to <1 mm and imposing sustained compressive forces that elevate the risk of orthodontically induced inflammatory root resorption (OIIRR) on the palatal aspect by 1.5–2.5 times compared to Class I or III cases. Cephalometric and CBCT studies confirm this inherent biomechanical vulnerability, with resorption volumes up to 20–30% greater in retracted incisors due to limited PDL buffering against the denser palatal bone, independent of treatment duration or extractions. In contrast, skeletal Class III (A) often involves labial proclination away from the palatal plate; deep bite Class I (B) rarely requires such retraction; and canine impaction (C), while locally risky, lacks inherent malocclusal predisposition and shows no significant association when surgically distanced pre-alignment.

Benefit of orthodontic treatment for patients with a pre-existing periodontal compromise

 # A key benefit of orthodontic treatment for patients with a pre-existing periodontal compromise (e.g., reduced but healthy periodontium) is:

A. Elimination of all PDL forces in the compromised teeth

B. Complete regeneration of lost alveolar bone and attachment

C. Increased tooth mobility for better functional adaptation

D. Optimization of axial loading to distribute occlusal forces more favorably

The correct answer is D. Optimization of axial loading to distribute occlusal forces more favorably

In patients with pre-existing periodontal compromise (e.g., reduced but stable attachment levels), orthodontic treatment aligns malpositioned teeth—such as flared or tipped incisors—to promote more vertical (axial) force transmission during occlusion, minimizing deleterious lateral or eccentric loads that exacerbate mobility, attachment loss, or alveolar stress in weakened areas. This biomechanical optimization, achieved via controlled intrusion and torque control with light forces (5–15 g/tooth), enhances long-term periodontal stability and function without regeneration, as evidenced by systematic reviews showing probing depth reductions (avg. 3.31 mm) and clinical attachment gains (avg. 5.28 mm) through improved force distribution and hygiene access. Options A (impossible, as PDL forces drive movement), B (not achievable orthodontically alone), and C (contraindicated, as mobility worsens prognosis) are inaccurate.

Potential adverse consequence of rapid maxillary expansion (RME)

 # One potential adverse consequence of rapid maxillary expansion (RME) in a patient nearing skeletal maturity is an increase in:

A. Anterior Bolton Ratio Discrepancy

B. Apical Base Width

C. Mandibular Plane Angle

D. Palatal Vault Depth

The correct answer is C. Mandibular Plane Angle

In patients nearing skeletal maturity, the midpalatal suture is partially or fully interdigitated, reducing skeletal expansion efficacy and promoting dentoalveolar effects like buccal tipping and posterior molar extrusion (1–2 mm on average), which increases the mandibular plane angle (MPA) by 1–3° via clockwise mandibular rotation and bite opening. This vertical change exacerbates hyperdivergent tendencies, potentially worsening facial height and stability, as noted in cephalometric studies of late mixed/early permanent dentition cases. In contrast, apical base width (B) is the intended skeletal gain (though diminished); anterior Bolton discrepancy (A) is unrelated; and palatal vault depth (D) typically decreases with RME due to transverse widening.