Obtaining artificially caries-affected dentin for in vitro studies.

AIM: This study evaluated and improved a protocol for obtaining standard caries-affected dentin (CAD) by Streptococcus mutans biofilm demineralization process. MATERIALS AND METHODS: Forty-eight human molars were divided in six experimental groups, according to: period of cariogenic challenge (7, 14 or 21 days) and type of dentin (erupted or unerupted teeth). After complete cariogenic challenge sound and CAD dentin were evaluated by: visual inspection (VI), digital radiography (DR), optical coherence tomography (OCT) and laser fluorescence (LF). RESULTS: Visual inspection confirmed the formation of CAD based on tissue yellowing and loss of surface gloss. Digital radiography detected the presence of radiolucent images, suggesting caries. Three calibrated examiners viewed all images obtained by VI and DR and were able to distinguish healthy from CAD. Fisher's exact statistical test (p < 0.05) confirmed no difference between groups by VI (G1/G4: p = 0.6; G2/G5: p = 1; G3/G6: p = 1) or DR (G1/G4: p = 1; G2/G5: p = 1; G3/G6: p = 1). Both LF values and demineralization depth, as determined by OCT, were subjected to ANOVA (p < 0.05). For LF, a statistically significant difference was observed for the type of substrate (p = 0.001). For OCT, no statistically significant differences in the type of substrate (p = 0.163), length of cariogenic challenge (p = 0.512) or interaction between factors (p = 0.148) were observed. Scanning electron micrographs confirmed the presence of CAD; a more uniform demineralization surface was observed in the dentin of unerupted teeth. CONCLUSION: This protocol suggests that standard CAD can be obtained in 7 days of cariogenic challenge using unerupted teeth. Clinical significance: With the new perspective on the clinical treatment of caries lesions, bonding is increasingly performed to demineralize CAD, which is susceptible to remineralization. A useful protocol to standardize the production of CAD, by microbiological cariogenic challenge, would be an important contribution to laboratorial test in the field of operative dentistry.

Comparison of chemical aging and water immersion time on durability of resin-dentin interface produced by an etch-and-rinse adhesive.

AIM: The aim of this study was to analyze and compare the influence of short-term NaOCl-storage and long-term water storage on the microtensile bond strength (µTBS) of etch-and-rinse adhesive system to human dentin. MATERIALS AND METHODS: Thirty-six third human molars were randomly divided into 6 groups (n = 6) according to the aging protocol: G1 (water, 24 hours); G2 (water, 6 months); G3 (water, 12 months); G4 (10% sodium hypochlorite--NaOCl, 1 hour); G5 (10% NaOCl, 3 hours) and G6 (10% NaOCl, 5 hours). A two-step etch-and-rinse adhesive (Adper Single Bond 2) was applied according to the manufacturers' instructions. A composite (Filtek Z250) was applied in four horizontal increments and was individually cured. Specimens were cut following the microtensile test technique, submitted to the different aging protocols, and tested in tension. The fracture pattern was observed in a stereomicroscope (40* magnification) and in a scanning electron microscope. The µTBS data were analyzed by ANOVA and Tukey's test (α = 0.05). RESULTS: The effect of storage in 10% NaOCl for 1 or 3 hours was not significantly different from that of aging in distilled water (DW) for 6 or 12 months (p > 0.05). Beams immersed in DW for 24 hours and in 10% NaOCl for 5 hours showed the highest and lowest µTBS values respectively. CONCLUSION: The aging protocols negatively influenced dentin bond strength. Aging specimens in 10% NaOCl for 1 or 3 hours can be an alternative method for long-term water storage (6 or 12 months) bond strength studies. CLINICAL SIGNIFICANCE: This aging protocol allows a quick achievement of longitudinal bond strength data, so that results are available to the professionals in this area while the materials are yet present at the dental market.

Er,Cr:YSGG laser dentine conditioning improves adhesion of a glass ionomer cement.

OBJECTIVE: The purpose of this study was to evaluate the bond strength (BS) of different surface treatments, including laser irradiation, between conventional glass ionomer cement (GIC) and dentine. METHODS: Eighty-five human third molars were divided into five groups with one of the following treatments: G1- control group, had no treatment; G2, G3, and G4 were treated with Er,Cr:YSGG laser irradiation at 0.5 W, 20 Hz, 25 mJ, 9 J/cm(2) (G2); 1.0 W, 20 Hz, 50 mJ, 18 J/cm(2)(G3); and 1.5 W, 20 Hz, 75 mJ, 27 J/cm(2) (G4); and G5 was treated with GIC liquid, which contains polyacrylic acid. Scanning electron microscopy (SEM) evaluation (n=2) and micro-shear bond strength test (n=15) using the GIC bonded to dentine were performed after 24 h of water immersion. The data were analyzed by one way analysis of variance (ANOVA), according to irradiation protocol (p<0.001). RESULTS: G2 specimens presented the highest BS results (in MPa) (10.50±0.84), followed by G1 (4.77±0.59) and G5 (4.26±1.02), which were statistically similar. G3 (3.32±0.39) and G4 (2.94±0.50) demonstrated the lowest BS values, and the difference between these groups was not statistically significant (p>0.001). SEM analysis of G1 revealed that the smear layer covered the entire dentine surface, whereas in G2, G3, and G4, irregular dentine was detected with open dentinal tubules and protruded peritubular dentine. Laser pulses could easily be distinguished in G2 but not in G3 and G4. G5 revealed a thin smear layer with dentinal tubule apertures clearly detectable. CONCLUSIONS: Dentine treatment with an Er,Cr:YSGG laser irradiation at a power of 0.5 W increased the BS of conventional GIC.

Adhesion to eroded dentin submitted to different surface treatments / Adesão a dentina erodida submetida a diferentes tratamentos de superfícies

Objective: This in vitro study measured the microshear bond strength (μSBS) of a composite resin to sound and artificially eroded dentin, submitted to surface treatment with diamond bur (DB) or Er,Cr:YSGG laser (L). Material and Methods: Bovine radicular dentin samples were randomly divided into six groups (n = 11): G1- positive control (sound dentin), G2- negative control (eroded dentin), G3-eroded dentin treated with Er,Cr:YSGG laser at 1.5 W, G4-eroded dentin treated with Er,Cr:YSGG laser at 2.0 W, G5-eroded dentin treated with Er,Cr:YSGG laser at 2.5 W and G6-eroded dentin treated with diamond bur. Erosive cycling was performed by immersion in 0.05M citric acid (pH 2.3; 10 min; 6x/day) and in remineralizing solution (pH 7.0, 1 h, between acid attacks), for 5 days. Three composite resin cylinders were bonded to the samples with etchand-rinse adhesive system and after 24 h storage in distilled/deionized water (37 ºC), samples were submitted to microshear bond strength test and mean values (MPa) were analyzed by one-way ANOVA and Tukey tests (α = 0.05). Results: G1 (19.9 ± 7.6A) presented the highest μSBS mean followed by G6 (12.2 ± 3.8B), which showed no statistically significant difference compared with the other groups, except from G4. The lowest μSBS value was found for G4 (7.1±1.5C), which did not differ statistically from G2 (7.5 ± 1.8B,C), G3 (8.4 ± 1.8B,C) and G5 (8.6 ± 3.2B,C). Analysis of the fracture pattern revealed a higher incidence of adhesive fractures for all experimental groups. Conclusion: The results indicate none of the surface treatments (diamond bur and Er,Cr:YSGG laser irradiation at the parameters used in this in vitro study), associated with the etch-and-rinse adhesive system, did not enhance composite resin bonding to eroded dentin...

Objetivo: O presente estudo in vitro visou avaliar a resistência de união (RU) de uma resina composta à dentina hígida e dentina erodida artificialmente, submetidas a diferentes tratamentos de superfície: ponta diamantada (DB) ou Er, Cr: YSGG (L) em diferentes parâmetros. Material e Métodos: Amostras de dentina radicular bovina foram aleatoriamente divididas em seis grupos (n =11): G1- controle positivo (dentina hígida sem tratamento); G2 – controle negativo (dentina erodida sem tratamento); G3 - dentina erodida condicionada com laser de Er,Cr:YSGG (L) em 1,5W; G4 – dentina erodida condicionada com Er,Cr:YSGG em 2,0 W; G5 - dentina erodida condicionada com Er,Cr:YSGG em 2,5 W e G6 - dentina erodida tratada com ponta diamantada. A formação da lesão de erosão foi realizada através de 5 dias de ciclagem por imersão alternada em solução desmineralizadora (ácido cítrico 0,05 M; pH 2,3; 10 min; 6x/dia) e em solução remineralizadora (pH 7,0; 1 h, entre os ataques de ácido). Três cilindros de resina composta foram confeccionados na superficie plana das amostras com o auxílio de um sistema adesivo tipo “condicione e lave”. Após o armazenamento em água destilada/ deionizada por 24 h a 37 ºC, os corpos de prova foram submetidos ao ensaio de microcisalhamento e a media dos valores de RU (MPa) obtidos foram analisados pelo teste ANOVA e teste de Tukey (α = 0,05). Resultados: Os resultados mostraram que G1 (19,9 ± 7,6A) apresentou os maiores valores de RU seguido do grupo G6 (12,2 ± 3,8B), que não apresentou diferença estatisticamente significativa em comparação com os outros grupos, com exceção do G4. O menor valor de RU foi encontrado no grupo G4 (7,1 ± 1,5C), que não diferiu estatisticamente do G2 (7,5 ± 1,8B,C), G3 (8,4 ± 1,8B,C) e G5 (8,6 ± 3,2B,C). A análise do padrão de fratura revelou uma maior incidência de fraturas adesivas para todos os grupos experimentais...

Ensaio de resistência adesiva por microtração: revisão de literatura / Microtensile bond strengh test: a literature review

Atualmente, a fim de se avaliar a resistência de união entre substrato e material restaurador, o teste mais utilizado é o ensaio por microtração. Todavia, na literatura encontram-se diversas maneiras de se realizar esse teste, desde a seleção da amostra até a análise dos resultados obtidos. Nesta revisão de literatura serão apresentados os principais métodos para realização do teste de microtração, bem como os fatores que podem afetar nos resultados obtidos por este ensaio

Currently, in order to evaluate the bond strength between the dental substrate and the restorative material, microtensile bond strength is the most used test. The purpose of this review is to describe all of the various modifications of the microtensile bond test in one paper. In the literature there are several ways to perform this test, since the selection of the sample to the analysis of the results. In this literature review will be presented the main methods for microtensile testing, as well as factors that may affect the results obtained by this test. The microtensile test methods offer versatility that cannot be achieved by conventional methods, It is up to the researcher to choose the test characteristics that best suits your needs

Influência do condicionamento da dentina na resistência de união de cimento de ionômero de vidro / Er, Cr: YSGG Laser Dentin Conditioning Influence on Glass Ionomer Cement Bond Strength

Objetivos: avaliar o efeito de 3 parâmetros de condicionamento da dentina utilizando o laser de Er,Cr;YSGG (2,78m) na resistência de união (RU) de cimento de ionômero de vidro convencional (CIV). Materiais e métodos: Foram utilizados neste estudo 68 terceiros molares humanos, divididos aleatoriamente em 4 grupos (n=17/ grupo): G1 (grupo controle): nenhum tipo de condicionamento; G2: condicionamento com laser de Er,Cr;YSGG 0,5W, 25mJ, 20Hz ou G3: 1,0W, 50mJ, 20Hz e G4: 1,5W, 75mJ, 20Hz. Dois dentes em cada um dos grupos foram observados em microscopia eletrônica de varredura (MEV) para identificar as características morfológicas dos diferentes condicionamentos de superfície realizados. Os outros 15 dentes/grupo, foram preparados para ensaio de RU, obtendo uma superfície plana de dentina onde foram construídos 3 (n=45/grupo) corpos de prova em forma de cilindro (1mm de diâmetro X 0,5mm de altura) utilizando o ionômero de vidro Ketac Molar Easymix- 3M ESPE. Após o armazenamento em água destilada por 24h a 37oC os espécimes foram ensaiados pelo teste de microcisalhamento. Os valores finais de resistência adesiva foram calculados e expressos em Mega Pascal (MPa). Os dados foram coletados e analisados por ANOVA (p<0,001). Resultados: Os espécimes do G2 apresentaram os maiores resultados de RU (10,50MPa ±0,84), seguido pelo G1 (4.77MPa ±0.59), G3 (3.32MPa ±0.39) e G4 (2,94MPa ±0,50) que não apresentaram diferença estatisticamente significante quanto comparados entre si

A análise em MEV do G1 mostrou camada de smear ao longo de toda a superfície de dentina, enquanto nos outros grupos observou-se túbulos dentinários abertos, característicos na irradiação com laser de Er,Cr:YSGG. Os pulsos do laser no G2 eram facilmente distinguidos, o que não acontecia nos grupos G3 e G4, sugerindo que parâmetros de energia maiores podem causar efeitos mais extensos à estrutura da dentina. Na análise do padrão de fratura, todos os grupos apresentaram maior porcentagem de fratura adesiva G1:73,3%, G2:48,9% G3:66,7% e G4:64,4%. O tipo de fratura mista foi proporcional ao aumento da RU (G1:24,4%, G2:46,7%, G3:20,0% e G4:17,8%). Conclusão: O condicionamento da dentina com o laser de Er,Cr:YSGG na potência de 0,5W aumentou significativamente a RU do CIV à dentina, enquanto os demais parâmetros testados reduziram a RU.

Objective: To evaluate the effect of 3 dentin conditioning parameters of Er,Cr:YSGG laser (2,78 m) on the bond strength (BS) of conventional glass ionomer cement (CGIC). Methods: A total of 68 third molars were divided into four groups and was subjected to one of the following pretreatments: G1- the control group, no pretreatment was realized; G2, G3 and G4 were pretreated with Er,Cr:YSGG laser irradiation at 0.5 W, 25 mJ, 9 J/cm2, and 20 Hz (G2); 1.0 W, 50 mJ, 18 J/cm2, and 20 Hz (G3); and at 1.5 W, 75 mJ, 27 J/cm2, and 20 Hz (G4). A scanning electron microscopy (SEM) evaluation (n=2) of pretreated dentine and a microshear bond strength test (n=15) were performed after 24h of water immersion. To build the specimens (each of which was 1 mm in diameter) for the microshear test, CGIC (Ketac Molar Easy Mix) was used. The data were analysed by one-way ANOVA (p<0.001). Results: The G2 specimens presented the highest BS results (10.50 MPa ± 0.84), and G1 had the next highest average BS values (4.77 MPa ± 0.59). G3 (3.32 MPa ± 0.39) and G4 (2.94 MPa ± 0.50) demonstrated the lowest BS values, although the BS difference between these groups was not statistically significant (p>0.001).

The SEM analysis of G1 revealed that the smear layer covered the entire dentine surface, whereas in groups G2, G3, and G4, irregular dentine was detected that possessed the open dentinal tubules and protruded peritubular dentine that are the characteristic results of laser irradiation. Laser pulses could easily be distinguished in G2 but not in G3 and G4, suggesting that higher energy parameters can broadly disrupt dentine structure and thereby affect the bonding of dentine to GIC. Conclusion: Dentine pretreatment with an Er,Cr:YSGG laser at a power of 0.5 W increased the BS of conventional GIC.