Christine Bettina Staudt

Different skeletal types underlying Class III malocclusion in a random population

INTRODUCTION We aimed to investigate the skeletal morphology underlying Class III malocclusion in a random population of young white men. METHODS We randomly selected 3358 Swiss Army recruits and examined them clinically. Of 77 (2.3%) with Class III malocclusion, 57 agreed to have lateral cephalograms. Mandibular and maxillary relationships (ANB, Wits), positions (SNB, SNA), and relative sizes (GoPg and ANS-PNS related to SN) were determined. Comparison with normal values showed discrepancies. RESULTS In 75.4% of the subjects, the Class III malocclusion had a skeletal origin. The discrepancy was mainly (47.4%) due to mandibular prognathism or growth excess (10.5% prognathism, 15.8% macrognathia, or 21.1% both), whereas the maxilla alone accounted for 19.3% (10.5% retrognathism, 8.8% micrognathia), and there was a combination of mandibular and maxillary disharmony in 8.7%. Dental compensation was common, with proclined maxillary incisors in 42.1% and retroclined mandibular incisors in 26.3%. CONCLUSIONS About 75% of the Class III malocclusion had skeletal origin in our subjects, mainly due to mandibular prognathism or macrognathia. The different skeletal types proposed in our study can give guidance in treatment planning and the evaluation of treatment effects in Class III malocclusion and in genetic studies.

Association between mandibular asymmetry and occlusal asymmetry in young adult males with class III malocclusion.

Abstract Objective. Our aim was to assess the association between mandibular asymmetry and sagittal and transverse occlusal asymmetry in young adult males with class III malocclusion. Our hypotheses were that (1) mandibular asymmetry increases with increasing mandibular length and (2) occlusal asymmetry is correlated with mandibular asymmetry. Material and methods. On lateral cephalograms of 54 subjects, skeletal class and mandibular length were measured. Mandibular asymmetry was evaluated on orthopantomograms as right–left difference between condylar or ramus heights. Occlusal asymmetry was assessed on dental casts by differences between right and left canine and molar relationship, anterior and posterior crossbite as well as midline deviation. Results. Mandibular asymmetry was significantly correlated with sagittal and transverse occlusal asymmetry (p < 0.05), but not with mandibular length (p > 0.05). Condylar asymmetry due to a longer condyle on one side was correlated with asymmetric aggravation of canine and molar class III on the ipsilateral side (r = –0.53 and –0.62, respectively). In contrast, ramus asymmetry was related to contralateral aggravation of canine and molar class III relationships (r = 0.27 and 0.29, respectively). Correlations existed between asymmetry in total height of the condyle and ramus and asymmetric aggravation of anterior crossbite (r = –0.33), posterior crossbite (r = –0.30) and lower midline deviation (r = –0.27) to the contralateral side (p < 0.05). Conclusions. Mandibular asymmetry is associated with occlusal asymmetry, especially in the sagittal plane. Condylar asymmetry had 28% and 38% of variance in common with sagittal canine and molar asymmetry, respectively. Asymmetry in total height of the condyle and ramus was related to transverse occlusal asymmetry.

Divergence in prevalence of mesiocclusion caused by different diagnostic criteria

INTRODUCTION The divergence in prevalence of a specific malocclusion is often striking. In addition to differences in ethnic background, sex, and age, inconsistency in diagnostic criteria might be important. Our aim was to investigate the prevalence of mesiocclusion in the same group by modifying the diagnostic criteria. METHODS We examined clinically 3358 young white men. The prevalence of mesiocclusion was determined by applying diagnostic criteria based on the sagittal relationship of the anterior teeth. Correlations to the molar sagittal relationship were calculated. RESULTS When the diagnosis was based on anterior crossbite, the prevalences were 9.0% for 1 incisor, 4.7% for 2 incisors, and 1.3% for 4 incisors involved. The prevalence decreased when teeth in edge-to-edge positions were excluded (5.2%, 1.9%, and 0.5%, respectively). When canine relationship was used, the prevalences varied from 5.2% to 0.2%, with mesiocclusion increasing from a quarter to 1 cusp width on average. When incisors and canines were combined, prevalences ranged from 0.2% to 3.0 %. The sagittal relationship of the anterior teeth was moderately correlated to the molars. CONCLUSIONS Subtle differences in diagnostic criteria lead to varying prevalence values for mesiocclusion. The diagnostic criteria of at least 2 incisors in crossbite or edge-to-edge and a mean canine mesiocclusion of at least a half cusp width are recommended for future epidemiologic studies as the anterior tooth relationship that correlates relatively highly to the sagittal molar relationship.