Preheating of dental composite resins: A scoping review.

OBJECTIVE: The aim of this scoping review was to analyze the available evidence on the preheating process and its effects on physicochemical properties of composite resins. MATERIALS AND METHODS: A systematic search was performed in August 2021 using PubMed/Medline, Embase, Scopus, and ISI Web of Science databases and gray literature without language or date restriction. Inclusion criteria were in vitro studies that assessed the physicochemical properties and marginal adaptation of preheated composite. Exclusion criteria were studies with experimental composite, literature reviews, clinical studies. Data from selected studies were qualitatively analyzed. RESULTS: In total, 104 studies were found from which 39 were included. The most used composite resin was Filtek Z350 XT (3 M/ESPE), preheated at 68°C in a Calset device (AdDent Inc., Danbury, CT, USA) for 5 or 15 min. Most studies showed decreased viscosity, increased conversion degree and microhardness of composite resins, and better marginal adaptation of direct and indirect restorations. Also, flexural strength was not affected, and data about bond strength were inconclusive due to heterogeneity among studies. CONCLUSION: The parameters used for preheating composite resins are heterogeneous. Preheating decreased viscosity, increased the conversion degree and microhardness of composite resins, and improved the marginal adaptation of direct and indirect restorations. CLINICAL SIGNIFICANCE: The analysis of evidence showed a high heterogeneity among preheating protocols. Preheating may benefit the handling and physicochemical properties of composite resins.

Effect of surface treatments on the adhesive properties of metallic brackets on fluorotic enamel

ABSTRACT Objective: To compare the effectiveness of the pretreatment with sandblasting and deproteinization with NaOCl on bond strength (SBS), in situ conversion degree (CD) of brackets in fluorotic enamel, and enamel etching pattern. Methods: A total of 90 non-carious maxillary premolars were used. The teeth were then assigned to six experimental groups according to: enamel surface (sound and fluorotic enamel); surface treatment (Regular etch with 37% phosphoric acid [RE]; 5.2% sodium hypochlorite + phosphoric acid [NaOCl + RE]; sandblasting + phosphoric acid [sandblasting + RE]). After storage in distilled water (37°C/24h), the specimens were tested at 1 mm/min until failure (SBS). Enamel-resin cement interfaces were evaluated for CD using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data from SBS and in situ CD values were analyzed using ANOVA two-away and Tukey test (α=0.05). The enamel etching pattern was evaluated only qualitatively. Results: For sound enamel, RE showed the highest SBS values, when compared to NaOCl + RE and Sandblasting + RE groups (p< 0.01). Regarding CD, only NaOCl + RE significantly compromised the mean DC, in comparison with other groups (p= 0.002). For fluorotic enamel, the Sandblasting + RE group significantly increased the mean SBS values, in comparison with RE group (p= 0.01) and no significant change was observed for CD (p> 0.52). Conclusions: The application of NaOCl or sandblasting associated to phosphoric acid improved the SBS of the brackets in fluorotic enamel without compromising the CD of the resin cement, with improving of enamel interprismatic conditioning.

RESUMO Objetivo: Comparar a efetividade do pré-tratamento com jateamento e desproteinização com NaOCl na resistência de união (SBS), grau de conversão in situ (GC) dos braquetes metálicos ao esmalte fluorótico e o padrão de condicionamento do esmalte. Métodos: Foi utilizado um total de 90 pré-molares superiores livres de cárie. Os dentes foram divididos em seis grupos experimentais, de acordo com: superfície do esmalte (Esmalte Sadio e Fluorótico); tratamento de superfície (Condicionamento com ácido fosfórico a 37% [ER]; Hipoclorito de sódio a 5,2% + ácido fosfórico [NaOCl + ER]; e jateamento + ácido fosfórico [Jateamento + ER]). Após armazenamento em água destilada (37oC/24 h), os espécimes foram testados a 1 mm/min até a falha (SBS). As interfaces esmalte-cimento foram avaliadas para GC usando espectroscopia micro-Raman. O padrão do condicionamento do esmalte foi avaliado sob microscopia eletrônica de varredura. Os dados da SBS e GC foram analisados utilizando ANOVA dois fatores e teste de Tukey (α= 0,05). O padrão de condicionamento do esmalte foi avaliado apenas qualitativamente. Resultados: Para o esmalte sadio, o ER apresentou os maiores valores de SBS, quando comparado aos grupos NaOCl + ER e Jateamento + ER (p< 0,01). Em relação ao GC, apenas a média do grupo NaOCl + ER foi comprometida significativamente em comparação aos outros grupos (p= 0,002). Para o esmalte fluorótico, Jateamento + ER aumentou significativamente a média dos valores de SBS, em comparação com o grupo ER (p= 0,01) e nenhuma mudança significativa foi observada no GC (p> 0,52). Conclusões: A aplicação de NaOCl ou jateamento associado ao ácido fosfórico melhorou a SBS dos braquetes no esmalte fluorótico sem comprometer o GC do cimento resinoso, com a melhoria do condicionamento interprismático do esmalte.

Dureza e grau de conversão de resinas polimerizadas por halógeno e LED / Hardness and degree of conversion of composite polymerized with halogen and LED

Este estudo objetivou determinar a dureza Vickers e o grau de conversão de uma resina composta polimerizadas por halógeno e LED em diferentes profundidades (2,0 e 3,0 mm). Foram utilizados os aparelhos XL3000 (halógeno - 3M) e Bright Lec (LED - MM Optics). Os corpos de prova mediam 2 e 3 mm de altura e foram divididos em 4 grupos (n=8). G1: 2 mmhalógeno; G2: 2 mm-LED; G3: 3 mm-halógeno e G4: 3 mm-LED. Os corpos de prova foram submetidos ao teste de dureza Vickers, sendo que cada amostra recebeu cinco indentações (200 g durante 6 segundos), e foi medido o grau de conversão com o espectrômetro de infravermelho (Fourier). A média dos resultados da dureza Vickers (G1: 33,64; G2: 26,60; G3: 22,71; e G4: 15,46) foi submetida à análise estatística (ANOVA), e não apresentaram diferença estatisticamente significante na profundidade de 2 mm. Na profundidade de 3 mm a tecnologia halógena apresentou resultado estatisticamente superior à tecnologia LED (p<0,05). Os dados obtidos no espectrômetro de infravermelho foram submetidos à análise estatística (testes T). Os resultados do grau de conversão não diferiram estatisticamente. As médias de grau de conversão foram: G1: 65,9%; G2: 66,0%; G3: 68,4% e G4: 67,5%. Assim, conclui-se que a dureza diminuiu com o aumento da profundidade para as diferentes tecnologias emissoras de luz, e na profundidade de 3,0 mm o aparelho halógeno apresentou resultado superior ao aparelho LED. O grau de conversão não foi afetado pela profundidade e pela emissão de luz (AU).

This study aimed to evaluate the Vickers hardness and the degree of conversion of a resin composite cured by two polymerized with different technology of emission of light (halogen and LED) in different depth (2 and 3 mm). Devices were used XL3000 (halogen - 3M​) and Bright Lec (LED - MM Optics). The specimens measured 2 and 3 mm in height and were divided into 4 groups (n = 8). G1: 2 mm-halogen; G2: 2 mm-LED; G3: 3 mm-halogen; and G4: 3 mm-LED. The samples were submitted to Vickers hardness test, each sample received five indentations (200 g for 6 seconds), and measured the degree of conversion with the infrared spectrometer (Fourier). The average of the results of Vickers hardness (G1: 33.64; G2: 26.60; G3: 22.71; and G4: 15.46) was subjected to statistical analysis (ANOVA) and showed no statistically significant difference at a depth of 2 mm. In the depth of 3 mm halogen technology presented was statistically superior to LED (p <0.05). Data from the infrared spectrometer have been subjected to statistical analysis (T test). The results of the degree of conversion did not differ statistically. The average degree of conversion was: G1: 65.9%; G2: 66.0%; G3: 68.4%; and G4: 67.5%. It was concluded that the hardness decreased with increasing depth for the different technologies emitting light, and 3.0 mm in depth of the halogen unit provides results superior to the LED device. The degree of conversion was not affected by the depth and light emission (AU).