The effects of different Er: YAG laser parameters combined with dole fluorine on dentinal tubules / 口腔疾病防治

Objective@# To explore the effects of Er: YAG lasers with different pulse energies and of Er: YAG lasers combined with Duraphat on dentine surface morphology and the dentinal tubule exposure rate, thereby providing a theoretical basis and parameters for clinically treating dentine hypersensitivity with Er: YAG lasers.@*Methods @# Dentinal tubule exposure models were divided into five groups, namely, group A (single Er: YAG laser exposure), group B (Duraphat+ Er: YAG laser), and group C (Er: YAG laser+Duraphat), which were exposed to 6 levels of pulse energy (80 mJ/P- 250 mJ/P), and experimental control group D (Duraphat group) and blank control group E. Scanning electron microscopy was used to observe dentine surface morphology and dentinal tubule closure in these groups, and Image-Pro Plus 6.0 software was used for image analysis to measure the exposure rates of the five groups of dentinal tubules.@*Results@#The dentinal tubule exposure rates for the A-D groups were significantly lower than that of the E group (P < 0.001); when the Er: YAG laser pulse energy was less than 250 mJ/P, the dentinal tubule exposure rates for the A-C groups were all lower than that of the D group, but when the pulse energy was higher than 250 mJ/P, the dentinal tubule exposure rates for the A-C groups were higher than that of the D group, showing significant differences (P < 0.001); under the same handling method, when the pulse energy was 80~200 mJ/P, the dentinal tubule exposure rate decreased as the pulse energy increased. If the pulse energy reached 250 mJ/P, the exposure rate of the dentinal tubules increased instead. There were apparently no significant differences between 80 mJ/P, 100 mJ/P, 160 mJ/P and 200 mJ/P in the A and C groups or between 80 mJ/P and 100 mJ/P in the B group (P > 0.05), while significant differences existed among the other groups (P< 0.05). Under the same pulse energy, the dentinal tubule exposure rates were A group > C group >B group; under different pulse energies, there existed significant differences between the A and B groups (P < 0.05); when the pulse energy was 120~250 mJ/P, there were significant differences between the B and C groups (P < 0.05), while there were no significant differences among other groups (P＜0.05).@*Conclusion@#Er: YAG lasers can close the dentinal tubules and play a cooperative role if combined with Duraphat; the effects of laser exposure are better if fluorine is applied beforehand; and dentinal tubule closure is positively correlated with the pulse energy of Er: YAG lasers within a certain energy scope, but when the pulse energy reaches 200 mJ/P, the dentine surface is excessively fused and injured.

The effect of resin cement type and cleaning method on the shear bond strength of resin cements for recementing restorations

PURPOSE: This laboratory study assessed the effect of different dentin cleaning procedures on shear bond strength of resin cements for recementing prosthesis. MATERIALS AND METHODS: 4 × 4 flat surface was prepared on the labial surface of 52 maxillary central incisors. Metal frames (4 × 4 × 1.5 mm) were cast with nickel-chromium alloy. All specimens were randomly divided into 2 groups to be cemented with either Panavia F2.0 (P) or RelyX Ultimate (U) cement. The initial shear bond strength was recorded by Universal Testing Machine at a crosshead speed of 0.5 mm/min. Debonded specimens were randomly allocated into 2 subgroups (n = 13) according to the dentin cleaning procedures for recementation. The residual cement on bonded dentin surfaces was eliminated with either pumice slurry (p) or tungsten carbide bur (c). The restorations were rebonded with the same cement and were subjected to shear test. Data failed the normality test (P < .05), thus were analyzed with Mann Whitney U-test, Wilcoxon signed rank test, and two-way ANOVA after logarithmic transformation (α = .05). RESULTS: The initial shear bond strength of group P was significantly higher than group U (P = .001). Pc and Uc groups presented higher bond strength after recementation compared to the initial bond strength. However, it was significant only in Pc group (P = .034). CONCLUSION: The specimens recemented with Panavia F2.0 provided higher bond strength than RelyX Ultimate cement. Moreover, a tungsten carbide bur was a more efficient method in removing the residual resin cement and increased the bond strength of Panavia F2.0 cement after recementation.

Effect of dentin pretreatment and curing mode on the microtensile bond strength of self-adhesive resin cements

PURPOSE: The aim was to evaluate the effect of curing mode and different dentin surface pretreatment on microtensile bond strength (microTBS) of self-adhesive resin cements. MATERIALS AND METHODS: Thirty-six extracted human permanent molars were sectioned horizontally exposing flat dentin surface. The teeth were divided into 12 groups (3 teeth/group) according to the dentin surface pretreatment methods (control, 18% EDTA, 10% Polyacrylic acid) and curing mode (self-curing vs. light-curing) of cement. After pretreatment, composite resin blocks were cemented with the following: (a) G-CEM LinkAce; (b) RelyX U200, followed by either self-curing or light-curing. After storage, the teeth were sectioned and microTBS test was performed using a microtensile testing machine. The data was statistically analyzed using one-way ANOVA, Student T-test and Scheffe's post-hoc test at P<.05 level. RESULTS: For G-CEM LinkAce cement groups, polyacrylic acid pretreatment showed the highest microTBS in the self-cured group. In the light-cured group, no significant improvements were observed according to the dentin surface pretreatment. There were no significant differences between curing modes. Both dentin surface pretreatment methods helped to increase the microTBS of RelyX U200 resin cement significantly and degree of pretreatment effect was similar. No significant differences were found regarding curing modes except control groups. In the comparisons of two self-adhesive resin cements, all groups within the same pretreatment and curing mode were significantly different excluding self-cured control groups. CONCLUSION: Selecting RelyX U200 used in this study and application of dentin surface pretreatment with EDTA and polyacrylic acid might be recommended to enhance the bond strength of cement to dentin.

Effect of cutting instruments on the dentin bond strength of a self-etch adhesive / 대한치과보존학회지

The purpose of this study was to compare the microshear bond strength of a self-etching primer adhesive to dentin prepared with different diamond points, carbide burs and SiC papers, and also to determine which SiC paper yield similar strength to that of dentinal surface prepared with points or burs. Fifty-six human molar were sectioned to expose the occlusal dentinal surfaces of crowns and slabs of 1.2 mm thick were made. Dentinal surfaces were removed with three diamond points, two carbide burs, and three SiC papers. They were divided into one of eight equal groups (n = 7); Group 1: standard diamond point(TF-12), Group 2: fine diamond point (TF-12F), Group 3: extrafine diamond point (TF-12EF), Group 4: plain-cut carbide bur (no. 245), Group 5: cross-cut carbide bur (no. 557), Group 6 : P 120-grade SiC paper, Group 7: P 220-grade SiC paper, Group 8: P 800-grade SiC paper. Clearfil SE Bond was applied on dentinal surface and Clearfil AP-X was placed on dentinal surface using Tygon tubes. After the bonded specimens were subjected to uSBS testing, the mean uSBS (n = 20 for each group) was statistically compared using one-way ANOVA and Tukey HSD test. In conclusion, the use of extrafine diamond point is recommended for improved bonding of Clearfil SE Bond to dentin. Also the use of P 220-grade SiC paper in vitro will be yield the results closer to dentinal surface prepared with fine diamond point or carbide burs in vivo.

Effect of dentin surface wetness on tensile bond strength of self adhesive resin cements / 대한치과보존학회지

The purpose of this study was to compare the tensile bond strength of several self-adhesive resin cements bonded to dentin surfaces with different wet conditions. Three self-adhesive resin cements; Rely-X Unicem (3M ESPE, St. Paul, MN, USA), Embrace Wetbond (Pulpdent, Oakland, MA, USA), Maxcem (Kerr, Orange, CA, USA) were used. Extracted sixty human molars were used. Each self-adhesive resin cement was adhered to the dentin specimens (two rectangular sticks from each molar) in different wet conditions. Tensile bond strength were measured using universal testing machine (EZ Test, Shimadzu corporation, Kyoto, Japan) at a crosshead speed of 1.0mm/min. After the testing, bonding failures of specimens were observed by Operative microscope (OPMI pro, Carl Zeiss, Oberkochen, Germany). T-test was used to evaluate the effect of dentin surface wetness. One-way ANOVA test was used to evaluate the tensile bond strength of self-adhesive resin cements in the same condition. Scheffe's test was used for statistical analyzing at the 95% level of confidence. The result showed that wetness of dentin surface didn't affect tensile bond strength of self-adhesive resin cements and Maxcem showed the lowest tensile bond strength.

Influence of appication time of self-etching primers on dentinal microtensile bond strength / 대한치과보존학회지

This study evaluated the influence of application time of self-etching primers on microtensile bond strength (microTBS) to dentin using three self-etching primer adhesive systems. Dentin surfaces were exposed from forty-eight human molars. They were conditioned with three self-etching primers (Clearfil SE Bond [SE], Unifil Bond [UF], Tyrian SPE + One Step Plus [TY]) and different primining times (10s, 20s, 30s and 40s). Composite resins were bonded to dentin surfaces and specimens were made. microTBS was tested and statistically compared using by one-way ANOVA and Tukey's Test The results of this study presented that priming time for 10s in SE and UF groups and for 30s and 40s in TY group was highly decreased microTBS to dentin.