Three-dimensional analysis of posterior tooth inclinations in transverse and sagittal relationships: A cross-sectional study.

OBJECTIVE: To compare tooth inclinations in different sagittal skeletal patterns and transverse maxillary relationships three-dimensionally. METHODS: A cross-sectional study carried out with 132 three-dimensional digital models in the complete permanent dentition divided into six groups (n=22); three groups with maxillary atresia: G1- skeletal class I, G2- skeletal class II and G3-skeletal class III; three groups without maxillary atresia: G4- skeletal class I; G5- skeletal class II and G6- skeletal class III. The comparison between the skeletal pattern was performed by the non-parametric tests of Kruskal Wallis and Dunn and between the groups by the non-parametric test of Mann Whitney. RESULTS: Subjects with skeletal class II and maxillary atresia had a greater lingual inclination of the maxillary teeth than those with class I and III; Subjects with skeletal class II without atresia had a less lingual inclination of the mandibular molars than the other classes (p<0.05). The maxillary premolars showed no variation in dental inclination with atresia, independent of the skeletal class in G1, G2, and G3 (p>0.05). The mandibular premolars showed that the groups without atresia G4, G5, and G6 presented no significant difference (p>0.05). Lower premolars in skeletal class III malocclusion individuals with atresia had a more negative inclination than the others. CONCLUSION: There is a difference in the inclination of posterior teeth between individuals with and without maxillary atresia and skeletal classes I, II, and III.

Comparison of the shear bond strength between metal brackets and Transbond™ XT, Filtek™ Z250 and Filtek™ Z350 before and after gastroesophageal reflux: An in vitro study.

PURPOSE: To evaluate in vitro the effect of gastroesophageal reflux, before and after bonding of metal brackets on composite resin surface. MATERIALS AND METHODS: Two hundred and ten resin discs were divided into 5 groups (n=42), according to the time and medium of storage: 24h, 7- and -30 days in artificial saliva (AS) and hydrochloric acid (HCL). Twelve samples from each group were submitted to surface roughness analysis (n=60). The other one hundred and fifty samples were divided into 3 groups (n=50) according to the bonding material: Transbond™ XT (TXT), 3M™ Filtek™ Z250 (Z250) and 3M™ Filtek™ Z350 XT (Z350). After bonding, the samples were subdivided, one more time, into 5 groups (n=10) according to the time (24h, 7, and 30 days) and medium storage (AS, HCL). Following, the shear bond strength (SBS) analysis was accomplished. Erosive challenge was performed for 7 or 30 days, before and after bonding of orthodontic brackets, for 1min, 4 times a day. SBS was performed in a universal testing machine (Instron) at 0.5mm/min. SBS data were subjected to two-way ANOVA and Tukey's test (α=0.05). RESULTS: TXT showed higher SBS values in all conditions (AS - 10.9±2.0 (24h); 10.5±4.9 (7 days); 9.4±2.2 (30 days); HCL - 11.5±3.7 (7 days); 8.0±2.1 (30 days)) - (P<0.0001). No statistical difference was detected in SBS between Z250 and Z350 composite resins (Z250 SBS: AS - 7.1±1.9 (24h), 5.2±1.8 (7 days), 4.5±1.5 (30 days); HCL - 5.2±2.3 (7 days), 5.0±2.5 (30 days)) - (P<=0.063)/Z350 SBS: AS - 7.4±1.0 (24h); 3.7±1.7 (7 days); 3.4±1.7 (30 days); HCL - 3.5±3.3 (7 days); 4.4±1.2 (30 days)) - (P<=0.167), respectively). Storage times and media did not statistically influence the SBS of TXT and Z250 composite resins (P>0.05), but did influence the Z350 SBS (P<0.05). CONCLUSION: Regardless of time and storage medium, TXT was the best composite resin for bonding brackets. Furthermore, the erosive challenge did not lead to surface changes in the Z250 resin at 7 and 30 days, unlike the Z350 resin.

Flexural strength and surface microhardness of materials used for temporary dental disocclusion submitted to thermal cycling: An in vitro study.

OBJECTIVE: The objective of this study was to evaluate the effect of temperature variation on surface microhardness and resistance to flexion of different materials used for making a temporary dental disocclusion. METHODS: One hundred specimens were made of the following materials (n=20): glass ionomer cement (GIC); compomer (CP); composite resin (CR); Blue colour resin composite for temporary dental disocclusion (BTDD); ultraviolet colour resin composite for temporary dental disocclusion (UVTDD). They were stored in distilled water for 24hours and, subsequently, half of the specimens in each group were subjected to thermal cycling (n=10). All samples were subjected to the microhardness test (HMV-2000) and the flexural strength analysis (INSTRON). The data were submitted to parametric statistical analysis (ANOVA) and Tukey's complementary test with a significance level of 5%. In the mechanical tests, all materials except the GIC showed a statistically significant difference between the groups subjected to thermal cycling and not submitted, and thermal cycling (P<0.05) was responsible for the reduction of the values found, except for GIC. RESULTS: In the mechanical tests, all materials except the GIC showed a statistically significant difference between the groups subjected to thermal cycling and not submitted, and thermal cycling (P<0.05) was responsible for the reduction of the values found, except for GIC. For microhardness, the highest average was found for BTDD and UVTDD (P≤0.05). As for the resistance, the flexion was found that in the groups not submitted to thermal cycling there was no statistically significant difference for all materials, except for GIC, for the groups with thermal cycling the materials BTDD and UVTDD showed a statistically significant difference from GIC, however, they did not differ statistically from the CP and CR groups. CONCLUSION: BTDD and UVTDD presented higher average results of surface microhardness and, in the resistance test, the flexion of these materials behaved similarly to the CP and the CR studied. The temperature variation has an effect on the properties of these materials.

Comparison of force delivery of thermally activated aesthetic and non-aesthetic Ni-Ti wires: An in-vitro study.

OBJECTIVE: The present study aimed to compare the force of aesthetic wires and their non-aesthetic equivalents from two commercial brands at different displacement points, during the unloading phase at 36°C. MATERIALS AND METHODS: Forty samples (n=10) were assessed, which were presented in two groups of aesthetic wires and two groups of non-aesthetic wires from the brands GAC® (Dentsply GAC® International, NY, USA) and Aditek®(Cravinhos, SP, Brazil), with 0.016-inch gauge. The orthodontic wires were maintained at a temperature of 36°C throughout the experiment and they were subjected to the three-point bending test at a speed of 1mm/min. The unloading values were recorded as 0.5, 1.5, and 2.5mm of displacement. The data were subjected to Student's t-test and unequal variance t test, at 5% significance level. RESULTS: During the unloading phase, the mean force was significantly higher for aesthetic wires than non-aesthetic ones, in the deflection of 2.5mm, presenting values means of 2.25N (P=.0213). In deflections of 0.5mm and 1.5mm, the orthodontic archwires did not show significant differences in force between the thermally activated wires with aesthetic coating and their non-aesthetic equivalents (P≥0.05). CONCLUSION: It is concluded that during the unloading phase at a temperature of 36°C, the orthodontic archwires analyzed did not show significant difference in force between thermally activated wires with aesthetic coating and their non-aesthetic equivalents at most displacement points analysed, except for the deflection of 2.5mm, which showed higher values.

Efecto de diferentes técnicas de pulido y refrigeración en la rugosidad superficial de una resina nanohíbrida / Effect of different techniques of cooling and polishing the surface roughness of a composite resin nanohíbrida

El objetivo de este trabajo in vitro fue evaluar la rugosidad superficial de una resina compuesta nanohíbrida (Tetric N Ceram®) utilizando 3 técnicas de acabado superficial, con y sin refrigeración. Materiales y método: Fueron confeccionados 60 especimenes (n=10), obtenidos por medio de una matríz metálica (10 x 2 mm). Los especímenes fueron almacenados durante 24 horas en agua destilada a temperatura ambiente, siendo posteriormente divididos en 6 grupos: G1- astropol + refrigeración, G2-astrobrush + refrigeración, G3- astropol + astrobrush + refrigeración, G4-astropol sin refrigeración, G5-astrobrush sin refrigeración, G6- astropol + astrobrush sin refrigeración. La lectura de la rugosidad superficial (Ra) fue realizada 24 horas luego de los respectivos tratamientos por medio de un rugosímetro marca Mitutoyo, tipo SJ - 201P (Japón). Resultados: Los datos fueron sometidos al test de ANOVA (p?0,05) y demostraron que no existe diferencias estadísticamente significantes entre las diferentes técnicas de pulido y refrigeración. Conclusión: La técnica de pulido y refrigeración no interfiere en la rugosidad superficial, por tanto se debe tener en consideración las demás propiedades físicas de las resinas compuestas y el aspecto biológico del diente

The study evaluated in vitro the surface roughness in a nanohibrid composite resin (Tetric N Ceram®) polished with the use three polishing techniques with and without refrigeration. Materials and Methods: Sixty discs (n=10), was made with aid of a metal matrix measuring 10 x 2 mm. The specimens were stored in artificial saliva in an oven at 37oC (±1 oC), for 24 hours. After this time the specimens were submitted to action of astropol + refrigeration (G1), astrobrush + refrigeration (G2), astropol + astrobrush + refrigeration(G3), astropol whithout refrigeration (G4), astrobrush whithout refrigeration (G5), astropol + astrobrush whithout refrigeration (G6). The surface roughness (Ra) of the specimens was avaliated after 24 hours using profilometer (Mitutoyo SJ - 201P - Japon). Results: the data were submitted to Analysis of Variance ANOVA (p?0,05) and were no statistically significant differences detected for each technique. Conclusion: The effect polishing techniques and refrigeration not interferance in the surface roughness, but needed consideration of others properties