Flávio Vellini-Ferreira

Comparative study of dental arch width in plaster models, photocopies and digitized images

The aim of this study was to comparatively assess dental arch width, in the canine and molar regions, by means of direct measurements from plaster models, photocopies and digitized images of the models. The sample consisted of 130 pairs of plaster models, photocopies and digitized images of the models of white patients (n = 65), both genders, with Class I and Class II Division 1 malocclusions, treated by standard Edgewise mechanics and extraction of the four first premolars. Maxillary and mandibular intercanine and intermolar widths were measured by a calibrated examiner, prior to and after orthodontic treatment, using the three modes of reproduction of the dental arches. Dispersion of the data relative to pre- and posttreatment intra-arch linear measurements (mm) was represented as box plots. The three measuring methods were compared by one-way ANOVA for repeated measurements (alpha = 0.05). Initial / final mean values varied as follows: 33.94 to 34.29 mm / 34.49 to 34.66 mm (maxillary intercanine width); 26.23 to 26.26 mm / 26.77 to 26.84 mm (mandibular intercanine width); 49.55 to 49.66 mm / 47.28 to 47.45 mm (maxillary intermolar width) and 43.28 to 43.41 mm / 40.29 to 40.46 mm (mandibular intermolar width). There were no statistically significant differences between mean dental arch widths estimated by the three studied methods, prior to and after orthodontic treatment. It may be concluded that photocopies and digitized images of the plaster models provided reliable reproductions of the dental arches for obtaining transversal intra-arch measurements.

Mesiodistal width and proximal enamel thickness of maxillary first bicuspids

This study aimed at evaluating measurements relative to the mesiodistal crown width and enamel thickness of maxillary first bicuspids. The sample consisted of 40 extracted sound bicuspids (20 right and 20 left), selected from white patients (mean age: 23.7 +/- 4.2 years), who were treated orthodontically with tooth extraction at a private clinic in São Paulo, SP, Brazil. All teeth were embedded in acrylic resin and cut along their long axis through the proximal surfaces, parallel to the buccal side, to obtain 0.6-mm central sections. The mesiodistal crown width and proximal enamel thickness were measured using a stereoscopic microscope connected to a computer. Measurements for right and left teeth, as well as the mesial and distal enamel thicknesses in the total sample, were compared by the Wilcoxon test (alpha = 0.05). The mesiodistal crown width mean values found were 7.51 mm (+/- 0.54) on the right side and 7.53 mm (+/- 0.35) on the left side. The mean enamel thickness on the distal surfaces for both sides was 1.29 mm (right: s.d. = 0.12 and left: s.d. = 0.18). The mean values for the mesial surfaces were 1.08 mm (+/- 0.14) and 1.19 mm (+/- 0.25), on the right and the left sides, respectively. No significant differences were found between the crown measurements and enamel thicknesses on the left and right sides. However, enamel thickness was significantly greater on the distal surfaces. Reliable measurements of enamel thickness are useful to guide stripping, which may be an attractive alternative to tooth extraction because it allows the transverse arch dimension to be maintained.

Estudo do relacionamento ântero-posterior entre os arcos dentários decíduos, de crianças nipo-brasileiras, dos dois aos seis anos de idade

AIM: the purpose of this cross-sectional study was to verify the prevalences of different types of anteroposterior relationships between deciduous dental arches and its possible sexual dimorphism, in Japanese-Brazilian children from 2 to 6 years of age. METHODS: a total of 310 Japanese-Brazilian children from 19 schools in Sao Paulo, Brazil, comprising 154 males and 156 females, were examined by visual inspection. The qui-square statistical test was applied to evaluate the data, and the results revealed no statistically significant sexual dimorphism for the majority of types of anteroposterior relationship. Therefore, the results for both genders were grouped together. RESULTS: the prevalences of anteroposterior relationships between deciduous second molars were: mesial step, 47.4%; flush terminal plane, 41.3%; distal step, 5.5% and asymmetric cases, 5.8%. The prevalences of anteroposterior relationship of deciduous canines were: Class 1, 77.4%; Class 2, 6.8%; Class 3, 6.8% and asymmetric cases, 9%. Only Class 2 revealed sexual dimorphism: 3.9% for female and 9.7% for male. The prevalences of overjet, were: normal, 71.3%; increased, 14.2%; anterior cross-bite, 7.4% and edge-to-edge bite, 7.1%. CONCLUSION: it was concluded that the majority of Japanese-Brazilian children evaluated in this study showed normal anteriorposterior relationship between dental arches, with a slightly tendency for the development of Class 3.

Crown dimensions and proximal enamel thickness of mandibular second bicuspids

To achieve proper recontouring of anterior and posterior teeth, to obtain optimal morphology during enamel stripping, it is important to be aware of dental anatomy. This study aimed at evaluating crown dimensions and proximal enamel thickness in a sample of 40 extracted sound, human, mandibular, second bicuspids (20 right and 20 left). Mesiodistal, cervico-occlusal and buccolingual crown dimensions were measured using a digital caliper, accurate to 0.01 mm. Teeth were embedded in acrylic resin and cut along their long axes through the proximal surfaces to obtain 0.7 mm-thick central sections. Enamel thickness on the cut sections was measured using a perfilometer. Comparative analyses were carried out using the Students-t test (α= 5%). The mean mesiodistal crown widths for right and left teeth were 7.79 mm (± 0.47) and 7.70 mm (± 0.51), respectively. Mean cervico-occlusal heights ranged from 8.31 mm (± 0.75) on the right to 8.38 mm (± 0.85) on the left teeth. The mean values for the buccolingual dimension were 8.67 mm (± 0.70) on the right and 8.65 mm (± 0.54) on the left teeth. The mean enamel thickness on the mesial surfaces ranged from 1.35 mm (± 0.22) to 1.40 mm (± 0.17), on the left and right sides, respectively. On the distal surfaces, the corresponding values were 1.44 mm (± 0.21) and 1.46 mm (± 0.12). No significant differences were found between measurements for right and left teeth. However, enamel thickness was significantly greater on the distal surfaces, compared with the mesial surfaces.

Estudo comparativo das dimensões transversais dos arcos dentários entre jovens com oclusão normal e má oclusão de Classe II, 1ª divisão

OBJETIVO: avaliar as possiveis diferencas nas dimensoes transversais dos arcos dentarios superiores e inferiores entre jovens com oclusao normal e ma oclusao de Classe II, 1a divisao. METODOLOGIA: foram avaliados 170 pares de modelos em gesso de jovens brasileiros leucodermas, com dentadura permanente, sendo 76 com oclusao normal (41 do genero feminino e 35 do masculino) e media de idade de 13 anos e 6 meses e 94 com ma oclusao de Classe II, 1a divisao (58 do genero feminino e 36 do masculino) e media de idade de 13 anos e 9 meses. Este grupo com ma oclusao foi dividido em duas categorias: Classe II sem apinhamento e Classe II com apinhamento. Compararam-se as distâncias intercaninos, interprimeiros pre-molares e intermolares, em ambos os arcos dentarios. RESULTADOS: em relacao ao grupo com oclusao normal, os jovens do genero masculino evidenciaram as seguintes diferencas estatisticamente significantes: 1) distância intercaninos inferiores maior para o grupo com Classe II sem apinhamento; 2) distância interprimeiros pre-molares superiores menor para o grupo com Classe II sem apinhamento e 3) distâncias interprimeiros pre-molares e intermolares, superiores e inferiores, menores para o grupo com Classe II com apinhamento. Por sua vez, o genero feminino evidenciou: 1) distâncias interprimeiros pre-molares e intermolares superiores menores para o grupo com Classe II sem apinhamento e 2) distâncias interprimeiros pre-molares e intermolares, superiores e inferiores, menores para o grupo com Classe II com apinhamento. CONCLUSAO: de um modo geral, os jovens com ma oclusao de Classe II, 1a divisao, apresentaram uma tendencia para deficiencia transversal posterior dos arcos dentarios, principalmente no grupo com apinhamento.

Mapping of proximal enamel thickness in permanent teeth

Aim: Knowledge of enamel thickness is relevant to perform stripping during orthodontic treatment. Thus, proximal enamel measurements of human permanent teeth were compared in this study. Methods: The measurements were previously obtained on cut sections of mandibular central (n = 30) and lateral (n = 30) incisors, canines (n = 20), first (n = 40) and second (n = 40) premolars; maxillary central (n = 20) and lateral (n = 20) incisors, canines (n = 20), first (n = 40) and second (n = 42) premolars. Comparisons between thicknesses by arch side and proximal surface were carried out using Student’s t-tests (α = 0.05). Teeth were compared according to the mesial and distal thicknesses by ANOVA and Tukey’s test. Results: No significant differences were found between right and left teeth. For the mesial surface, the mandibular second premolar presented the highest mean value (1.376 mm ± 0.198; p<0.001). The mandibular central incisor had the smallest thickness in relation to the other teeth (0.675 mm ± 0.144), although not significant compared with the mandibular lateral incisor and canine (0.734-0.781 mm). The mandibular second premolar also presented the higher distal thickness in relation to the others (1.450 mm ± 0.172), although not significant compared with the maxillary first premolar (1.322 mm ± 0.195). Mandibular incisors had the lowest means for distal thickness (0.872-0.879 mm), although not statistically different compared with maxillary incisors and mandibular canine (1.002-1.015 mm). Distal thickness was greater than mesial (p<0.001). Conclusions: Interproximal stripping should be less marked in incisors and mesial surfaces.