Minimal alterations on the enamel surface by micro-abrasion: in vitro roughness and wear assessments

Objective: To evaluate the in vitro changes on the enamel surface after a micro-abrasion treatment promoted by different products. Material and Methods: Fifty (50) fragments of bovine enamel (15 mm × 5 mm) were randomly assigned to five groups (n=10) according to the product utilized: G1 (control)= silicone polisher (TDV), G2= 37% phosphoric acid (3M/ESPE) + pumice stone (SS White), G3= Micropol (DMC Equipment), G4= Opalustre (Ultradent) and G5= Whiteness RM (FGM Dental Products). Roughness and wear were the responsible variables used to analyze these surfaces in four stages: baseline, 60 s and 120 s after the micro-abrasion and after polishing, using a Hommel Tester T1000 device. After the tests, a normal distribution of data was verified, with repeated ANOVA analyses (p?0.05) which were used to compare each product in different stages. One-way ANOVA and Tukey tests were applied for individual comparisons between the products in each stage (p?0.05). Results: Means and standard deviations of roughness and wear (µm) after all the promoted stages were: G1=7.26(1.81)/13.16(2.67), G2=2.02(0.62)/37.44(3.33), G3=1.81(0.91)/34.93(6.92), G4=1.92(0.29)/38.42(0.65) and G5=1.98(0.53)/33.45(2.66). At 60 seconds, all products tended to produce less surface roughness with a variable gradual decrease over time. After polishing, there were no statistically significant differences between the groups, except for G1. Independent of the product utilized, the enamel wear occurred after the micro-abrasion. Conclusions: In this in vitro study, enamel micro-abrasion presented itself as a conservative approach, regardless of the type of the paste compound utilized. These products promoted minor roughness alterations and minimal wear. The use of phosphoric acid and pumice stone showed similar results to commercial products for the micro-abrasion with regard to the surface roughness and wear

Impact of filler size and distribution on roughness and wear of composite resin after simulated toothbrushing

Objectives: Nanofilled composite resins are claimed to provide superior mechanical properties compared with microhybrid resins. Thus, the aim of this study was to compare nanofilled with microhybrid composite resins. The null hypothesis was that the size and the distribution of fillers do not influence the mechanical properties of surface roughness and wear after simulated toothbrushing test. Material and methods: Ten rectangular specimens (15 mm x 5 mm x 4 mm) of Filtek Z250 (FZ2), Admira (A), TPH3 (T), Esthet-X (EX), Estelite Sigma (ES), Concept Advanced (C), Grandio (G) and Filtek Z350 (F) were prepared according to manufacturer's instructions. Half of each top surface was protected with nail polish as control surface (not brushed) while the other half was assessed with five random readings using a roughness tester (Ra). Following, the specimens were abraded by simulated toothbrushing with soft toothbrushes and slurry comprised of 2: 1 water and dentifrice (w/w). 100,000 strokes were performed and the brushed surfaces were re-analyzed. Nail polish layers were removed from the specimens so that the roughness (Ra) and the wear could be assessed with three random readings (mu m). Data were analyzed by ANOVA and Tukey's multiple-comparison test (alpha = 0.05). Results: Overall outcomes indicated that composite resins showed a significant increase in roughness after simulated toothbrushing, except for Grandio, which presented a smoother surface. Generally, wear of nanofilled resins was significantly lower compared with microhybrid resins. Conclusions: As restorative materials suffer alterations under mechanical challenges, such as toothbrushing, the use of nanofilled materials seem to be more resistant than microhybrid composite resins, being less prone to be rougher and worn.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), BrazilCNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico), Brazil [136375/2006-5

Orthodontic movement of a maxillary incisor through the midpalatal suture A case report

Orthodontic space closure is a treatment alternative when a maxillary central incisor is missing. The objective of this report was to present an unusual treatment in which a right maxillary central incisor was moved through the midpalatal suture to replace the absent contralateral tooth. The biologic aspects and clinical appearance of the recontoured lateral and central incisors were analyzed. The position of the examined teeth and the appearance of the surrounding soft tissues were satisfactory; however, the upper midline frenulum deviated to the left. The incisor was successfully moved with no obvious detrimental effects as observed on the final radiographs. In the radiographic and tomographic examinations, the midline suture seemed to have followed the tooth movement. The patient expressed satisfaction with the results. It was concluded that orthodontic movement of the central incisor to replace a missing contralateral tooth is a valid treatment option, and the achievement of an esthetic result requires an interdisciplinary approach, including restorative dentistry and periodontics. (Angle Orthod. 2012;82:370-379.

Wear and surface roughness alteration evaluation of different composite resins after toothbrushing and pH cycling

O presente estudo teve como objetivo avaliar quantitativamente a alteração na rugosidade superficial e o desgaste de resinas compostas com diferentes características de matriz orgânica e de carga inorgânica frente ao teste de escovação simulada e ciclagem de pH. Foram testadas três resinas compostas: Filtek Z250 (Bis-GMA, microhíbrida), Filtek Z350 (Bis-GMA, nanoparticulada) e Filtek P90 (silorano, microhíbrida)(3M-ESPE). Para cada resina foram confeccionados dois grupos (n=10) de corpos de prova retangulares (15mmx5mmx4mm). Após a polimerização e polimento adequado dos espécimes, a rugosidade inicial (Ra) foi obtida pela média de três leituras com o Rugosímetro Hommel T1000. Metade de cada corpo de prova foi protegida com esmalte de unha e um dos grupos de cada resina foi submetido a um protocolo de ciclagem de pH (desmineralização-pH 4,3 e remineralização-pH 7,0). Para o teste de abrasão foram realizados 100.000 ciclos de escovação simulada, permanecendo a metade protegida como grupo controle. Na metade escovada foi verificada a rugosidade final, seguindo os mesmos parâmetros iniciais, e o desgaste (µm) foi quantificado pela média de 3 leituras do perfil real abrangendo as duas superfícies (controle e escovada). Os resultados obtidos (ANOVA, teste t Student e Tukey, p<0.05) mostraram diferenças significantes para o desgaste e alteração de rugosidade entre as resinas testadas. A maior média de desgaste foi apresentada pela Filtek P90 (11,505µm±5,690) com diferença significante para a Filtek Z250 (4,191µm±1,725) e para a Filtek Z350 (4,163µm±0,947), sendo que a ciclagem de pH afetou apenas o desgaste da resina Filtek P90 (15,305µm±5,409). Verificou-se aumento da média de rugosidade superficial para as resinas Filtek Z250 e Z350 após escovação simulada, enquanto que a resina Filtek P90 apresentou comportamento contrário, com diferenças estatisticamente significantes (p<0,05). As imagens de microscopia eletrônica de varredura apresentaram-se coerentes com os resultados quantitativos obtidos.The present study aimed to quantitatively evaluate the surface roughness alteration and wear of resin composites with different characteristics of organic matrix and inorganic filler when submitted to simulated toothbrushing abrasion and pH cycling. Three different resin composites were evaluated: Filtek Z250 (Bis-GMA, microhybrid), Filtek Z350 (Bis-GMA, nanofilled) and Filtek P90 (silorane based, microhybrid) (3M-ESPE). For each resin two groups (n=10) of rectangular specimens (15mmX5mmX4mm) were made. After polymerization and polishing, the initial roughness (Ra) was evaluated by the average of three tracings using a roughness tester Hommel T1000 basic. Half of each specimen was protect with nail varnish and one group of each resin was submitted to pH cycling (demineralization-pH 4,3 and remineralization-pH 7,0). For the abrasion test 100.000 strokes of simulated toothbrushing was processed. The protected side was maintained as control. Over the brushed side the final roughness was measured with the same initial parameters and wear was quantified by the average of 3 readings of the real profile between the two surfaces (control and brushed side). The obtained results (ANOVA, Student t test and Tukey, p<0.05) showed significant differences of wear and surface roughness alteration between the tested materials. Filtek P90 presented the highest average wear rate (11.505 ± 5.690µm) compared to Z250 (4.191 ± 1.725µm) and Z350 (4.163 ± 0.947µm) and the pH cycling significantly affected the wear of Filtek P90(15.305 ± 5.409 mM). The surface roughness evaluation revealed an increasing on surface roughness for Filtek Z250 and Filtek Z350 after toothbrushing, while Filtek P90 showed an opposite behavior, with statistically significant differences (p<0.05). The scanning electron microscope images were in accordance to the quantitative results obtained