Dental crowding: the role of genetics and tooth wear.

OBJECTIVE: To evaluate the role of genetics and tooth wear in the etiology of dental crowding through the analysis of a split indigenous Amazon population. MATERIALS AND METHODS: Dental crowding prevalence (n  =  117), tooth wear (n  =  117), and inbreeding coefficient (n  =  288) were compared for both villages. A biometric investigation was performed by dental cast analysis of 55 individuals with no tooth loss. Mann-Whitney statistics, independent t-tests, and Fisher exact tests were used at P < .05. RESULTS: A high coefficient of inbreeding was confirmed in the resultant village (F  =  0.25, P < .001). Tooth wear was not significantly different (P  =  .99), while a significantly higher prevalence of dental crowding was confirmed in the original village (PR  =  6.67, P  =  0.02). Forty dental arches (n  =  20) were examined in the new group, and only one (2.5%) had a dental crowding ≥ 5 mm. In the original villages, we found 20 arches (28.6%) with dental crowding. No difference was observed for tooth size, while larger dental arch dimensions explained a lower level of dental crowding in the resultant village. CONCLUSIONS: Our findings downplay the widespread influence of tooth wear, a direct evidence of what an individual ate in the past, on dental crowding and emphasize the role of heredity, exacerbated through inbreeding, in the etiology of this malocclusion.

The ability of orthodontists and laypeople to discriminate mandibular stepwise advancements in a Class II retrognathic mandible.

OBJECTIVES: This study analysed the ability of orthodontists and laypeople to discriminate mandibular stepwise advancements. MATERIALS AND METHODS: Four pictures (in duplicate) were taken of a male patient with Class II malocclusion and mandibular deficiency with the mandible positioned in habitual maximum intercuspation (HMI) and with stepwise advancements of 2mm, 4mm and 6mm. These images were examined by orthodontists (n=30) and laypeople (n=30). The Wilcoxon signed-rank test was used to evaluate intra-examiner agreement. Intra-examiner ability to discriminate stepwise mandibular advancements was examined by Friedman's test. A Mann-Whitney's test was carried out to analyse score difference between orthodontists and laypeople. Type I error (alpha) was set as 5% for all statistical tests. RESULTS: We observed a satisfactory to excellent level of methodological reliability. While laypeople were able to notice mandibular advancements ≥4 mm (p<0.05), orthodontists were able to observe mandibular advancements ≥2 mm (p<0.05). The orthodontists were more critical than laypeople with regard to the facial profile evaluation when facial convexity increased (p<0.001), but no significant difference was observed when the sagittal maxillo-mandibular relationship approached normality (p<0.05). CONCLUSIONS: Considering that the mean sagittal mandibular growth due to the use of functional orthopaedic appliances is reported in the literature as 2mm, it seems that laypeople may not able to discriminate this amount of change in facial-profile attractiveness.

Evaluation of frictional forces of polycarbonate self-ligating brackets.

AIM: To evaluate the frictional forces generated by ceramic- (Opal, Ultradent) and glass-fiber-reinforced polycarbonate self-ligating brackets (Oyster, Gestenco) and compare the effectiveness of these ligatureless systems with glass-fiber-reinforced polycarbonate conventional brackets (Blonde, Gestenco). The hypothesis is that there is no difference between frictional forces generated by ceramic- and glass-fiber-reinforced polycarbonate self-ligating and glass-fiber-reinforced polycarbonate conventional brackets. METHODS: Twelve preadjusted 0.022 3 0.028-inch maxillary canine brackets were tested, divided into three groups: Opal, Oyster, and Blonde. Frictional tests were conducted with the Emic DL 10000 testing machine with a 20 N loadcell for 40 seconds at a 0.5 cm/min speed. Each bracket-wire combination was tested five times. The data generated were analyzed by parametric analysis of variance (one-way ANOVA) and Bonferroni tests. RESULTS: Analysis of variance indicated significant differences for the three groups (P<.01). The frictional forces of the Oyster glass-fiber-reinforced polycarbonate self-ligating brackets were significantly lower (37.0 ± 8.9 cN) than those of the Opal ceramic-reinforced polycarbonate self-ligating brackets (49.5 ± 10.1 cN), while the Blonde glass-fiber-reinforced conventional bracket frictional forces were 105.8 ± 6.4 cN. CONCLUSION: Oyster glass-fiber-reinforced polycarbonate brackets produced less friction than Opal ceramic-reinforced polycarbonate brackets. The polycarbonate ligatureless system showed significantly lower frictional forces compared to Blonde conventional polycarbonate brackets tied with elastomeric ligatures. The study rejected the initial hypothesis because there are significant differences of frictional forces among the tested systems.

Efeitos da biomecânica ortodôntica na estrutura radicular dos dentes anteriores / Effects of the orthodontic biomechanics in the root structure of anterior teeth

Realizou-se uma revisão da literatura com o objetivo de esclarecer os fatores etiológicos responsáveis pela reabsorção radicular ortodonticamente induzi da, a metodologia para o diagnóstico e os fatores biomecânicos que induzem essa alteração. Ao mesmo tempo é apresentado um caso clínico de uma paciente tratada ortodonticamente com extrações de primeiros pré-molares,destacando o papel da mecânica de deslize com forças leves no aparecimento da reabsorção. Os autores destacaram a etiologia multifatorial das reabsorções, sendo elas sistêmicas, locais e por vezes relacionadas ao tratamento. As causas sistêmicas estariam relacionadas a alterações hormonais e ao estado geral de saúde do paciente. As causas locais envolveriam a ocorrência de trauma, endodontia, e anatomia da raiz e das cristas ósseas alveolares e, por fim, as relacionadas ao tratamento, que apontarampara mecânicas que utilizam ou produzem níveis de força mais elevados, que quando aplicados aos dentes promovem uma resposta tecidual mais exacerbada, com formação de extensas zonas hialinas, que induzem ao processo reabsortivo. O caso clínico descrito no presente estudo mostrou um teor de reabsorção radicular compatível com a mecânica adotada caracterizadapor discreto arredondamento apical. Concluiu-se que as variáveis relacionadas ao tratamento que mais causaram reabsorções foram os movimentos intrusivos, fechamento de espaços, elásticos de Classe II, a correção de mordida aberta e o torque. Destacou-se, finalmente, que o tratamento deva ser instituído com forças leves e frequentemente monitorado com a utilização deexames radiográficos periapicais.

This study reviews the literature and presents a clinical case ofClass fI malocclusion treated orthodontically witb premolar extractions. Our objectives are to assess the etiology of orthodontically induced root resorption, as well as to determine the diagnostic methodsassociated with biomechanical factors that induced the resorption. The authors emphasize the multifactorial etiology ofresorption that can be systemic, local and sometimes triggered by lhe orthodontic treatment. The systemic factors are related to hormonalalterations, and the patient's general health. The localfactors include trauma, endodontics, and anatomy ofthe root and alveolar crest. The orthodontic treatment can also trigger resorption ifthe mechanics produces increased levels offorce, that cause intensetissue response, hyalinization zones that lead to the resorption processo The clinical case shown in this paper reveals root resorption with slight apical rounding due to the mechanics used. We concluded that the variables related to the orthodontic treatment thatlead 10 resorption were intrusive movements, space closure, Class 11elastics open bite mechanics and torque. Finally, this study suggests that the orthodontic treatment must apply light forces and be constantly monitored with periapical x-rays.

A estética no sistema de braquetes autoligáveis / The self-ligating system in an aesthetic view

INTRODUÇÃO: os braquetes autoligáveis foram, inicialmente, idealizados com objetivo de otimização do tempo de atendimento clínico. Por dispensar qualquer tipo de amarração, inúmeras vantagens foram atribuidas a este sistema, com a redução da fricção superficial na interface braquete/fio ortodôntico. Com esta redução, são necessárias forças de menor intensidade para o estabelecimento da movimentação dentária, realizada, assim, de uma forma mais rápida e eficiente. Em decorrência da maior demanda estética por parte dos pacientes, os braquetes autoligáveis começaram a ser confeccionados em policarbonato, promovendo ganhos estéticos únicos, quando em comparação a seus anólogos metálicos. OBJETIVO: realizar uma revisão de literatura sobre o sistema de braquetes autoligáveis estéticos.

INTRODUCTION: The self-ligating system was introduced aiming the reduction of chair time. Once this system does not need any ligation form, several advantages were observed, such as the reduction on superficial friction in couple bracket/ orthodontic wire, and the reduction on the force level that is necessary to establish the orthodontic tooth movement. The growing demands of aesthetic patients induced the self-ligating system to be made of polycarbonate material, resulting in unique aesthetic advantages when compared with the metallic form of this system. AIM: The objective of this paper was to proceed with a literature review about aesthetic self-ligating brackets.

Soldagem em ortodontia (parte 2): soldagem autógena / Soldering in Orthodontics (part 2): the welding process

O objetivo deste artigo foi realizar uma revisão de literatura sobre o processo de soldagem autógena em Ortodontia. A soldagem autógena, muito presente no cotidiano clínico, viabiliza a união de dispositivos, principalmente de aço inoxidável, necessários à realização da mecânica ortodôntica. A técnica foi descrita juntamente com as modificações apresentadas pelos componentes envolvidos no processo. Comparou-se, também, tal procedimento com a soldagem heterógena, evidenciando-se uma menor ocorrência de alterações estruturais nos elementos envolvidos, bem como uma menor subordinação da técnica à destreza do operador.