Estudo epidemiológico da agenesia de segundos pré-molares e sua relação com a agenesia de outros dentes permanentes / Epidemiological investigation of second premolar agenesis and its relationship with agenesis of other permanent teeth

Objective ? This study aims to evaluate the epidemiological characteristics of a sample of patients with agenesis of second premolars, as well as to investigate its association with agenesis of other permanent teeth. Material and methods ? A Brazilian sample of 203 patients aged from 8 to 22 years was selected, all patients presenting agenesis of at least 1 second premolar. Patient age, gender and ethnicity were recorded, as well as the history of extraction of permanent teeth and associated agenesis of other permanent teeth. Results: ? Most individuals presenting second premolar agenesis were female (66%), a sex ratio of 2F: 1M. The frequency of second premolar agenesis was higher in the mandible (61.5%) than in the maxilla (16.7%), while 21.6% of the patients showed second premolar agenesis affecting both arches. The prevalence of unilateral and bilateral agenesis was similar (50%) in the maxilla, while in the mandible 60% of the sample exhibited unilateral agenesis. The mandibular left hemi arch was the most frequently affected. Most of the patients (45.3%) had agenesis of just 1 second premolar. There was a high prevalence of agenesis of other permanent teeth associated with second premolar agenesis, especially of maxillary lateral incisors (16%) and third molars (48%). Conclusion: Agenesis of second premolars was more prevalent in females and at the left side of the mandibular arch and was often associated with agenesis of other permanent teeth.

Objetivo ? O presente trabalho visa avaliar as características epidemiológicas de uma amostra de pacientes com agenesia de segundos pré-molares, assim como verificar a sua associação com a agenesia de outros dentes permanentes. Material e métodos ? Foi avaliada a documentação ortodôntica de 203 pacientes brasileiros com idade entre 8 e 22 anos, apresentando agenesia de pelo menos um segundo pré-molar. Foi feito o registrado de: idade do paciente, sexo e etnia, histórico de extrações de dentes permanentes e presença de agenesias de outros dentes permanentes associadas. Resultados ? A maior parte da amostra era composta pelo sexo feminino (66%), apresentando oddes ratio de 2F: 1M. A agenesia de segundo pré-molar mostrouse mais prevalente no arco inferior (61,5%) do que no superior (16,7%), enquanto que 21,6% mostraram a referida agenesia em ambos os arcos. Os valores percentuais obtidos para agenesia tanto unilateral quanto bilateral foram semelhantes (50%) no arco dentário superior, enquanto que, no arco dentário inferior, 60% da amostra apresentaram agenesia unilateral. A maioria dos pacientes (45,3%) apresentou agenesia de apenas 1 segundo pré-molar. Observou-se uma alta prevalência de agenesia de outros dentes permanentes associada à agenesia de segundos pré-molares, principalmente dos incisivos laterais superiores (16%) e dos terceiros molares (48%). Conclusão: A agenesia dos segundos pré-molares foi mais prevalente no sexo feminino, no arco inferior do lado esquerdo e mostrou-se frequentemente associada a outras agenesias de dentes permanentes.

Increased occurrence of dental anomalies associated with second-premolar agenesis.

OBJECTIVE: To evaluate the prevalence of dental anomalies in patients with agenesis of second premolars and compare the findings with the prevalence of these anomalies in the general population. MATERIALS AND METHODS: A Brazilian sample of 203 patients aged 8 to 22 years was selected. All patients presented agenesis of at least one second premolar. Panoramic and periapical radiographs and dental casts were used to analyze the presence of other associated dental anomalies, including agenesis of other permanent teeth, ectopia of unerupted permanent teeth, infraocclusion of deciduous molars, microdontia of maxillary lateral incisors, and supernumerary teeth. The occurrence of these anomalies was compared with occurrence data previously reported for the general population. Statistical testing was performed using the chi-square test (P < .05) and the odds ratio. RESULTS: The sample with agenesis of at least one second premolar presented a significantly increased prevalence rate of permanent tooth agenesis (21%), excluding third molars. Among the sample segment aged 14 years or greater (N = 77), occurrence of third-molar agenesis (48%) exceeded twice its normal frequency. Significant increases in occurrence of microdontia of maxillary lateral incisors (20.6%), infraocclusion of deciduous molars (24.6%), and distoangulation of mandibular second premolars (7.8%) were observed. Palatally displaced canine anomaly was also significantly elevated (8.1%). CONCLUSION: The results provide evidence that agenesis of other permanent teeth, microdontia, deciduous molar infraocclusion, and certain dental ectopias are the products of the same genetic mechanisms that cause second-premolar agenesis.

Longitudinal effects of rapid maxillary expansion.

OBJECTIVE: To evaluate the long-term effects of rapid maxillary expansion (RME) via banded expanders in the sagittal and vertical facial planes. MATERIALS AND METHODS: The sample consisted of 25 patients who had undergone RME (with either Haas-type or Hyrax hygienic expanders) followed by standard edgewise orthodontic therapy. This sample was compared with a group of 25 patients who had edgewise treatment only and with a control nontreatment group of 26 subjects, matched by age and gender with the patients of the other two groups. Lateral cephalograms were taken before treatment (T1), at the end of treatment (T2), and at 3 years posttreatment (T3), comprising a 5-year average time of observation. RESULTS: RME treatment, in the long-term, did not influence the sagittal position of the apical jaw bases or the facial vertical dimension. CONCLUSION: Unfavorable cephalometric changes resulting immediately after RME are temporary, and therefore concerns about using RME in patients with vertical growth patterns or an extremely convex facial profile are not substantiated.