[Evaluation of shear bond strength of composite to feldspathic porcelain after porcelain surface treatment with CO2 and Er:YAG lasers]

Fractured ceramic crowns can sometimes be repaired with composite resin. The aim of the current study was to determine the shear bond strength of composite to Feld spathic porcelain after CO[2] and Er:YAG laser porcelain surface preparation. In this in-vitro study, 36 Feldspathic porcelain blocksmeasuring 1*10*10 mm were divided into 3 groups of 12. Porcelain surfaces in the first and second groups were treated with 1.8W CO[2] laser and 5W Er:YAG laser irradiation, respectively. Third group specimens were subjected to 9.5% hydrofluoric acid surface conditioning. All groups received application of silane and adhesive after wards. A composite cylinder with 3.5 mm diameter and 5 mm height was bonded to specimens. In order to evaluate the shear bond strength, a Universal Testing Machine with crosshead speed of 1 mm/min was used. Statistical analysis was performed using one-way ANOVA and Tukey's HSD test and P<0.05 was considered statistically significant. The mean shear bond strength values [MPa] were 13.03 +/- 2.57%, 12.02 +/- 3.4 and 19.23 +/- 4.62, for the first, second and third groups respectively. One-way ANOVA revealed a statistically significant difference in this respect between the three groups [P< 0.001]. Tukey's HSD test demonstrated significant differences between the first and third groups [P= 0.000] as well as the second and third groups [P=0.000]. However, no significant difference was detected between the first and second groups [P =0.778]. Considering the study results, CO[2] or Er:YAG laser irradiation is not suggested as an appropriate alternative to hydrofluoric acid for surface preparation of Feld spathic porcelain

Comparison between shear bond strength of composite resin following surface conditioning with Er Cr YSGG laser and acid etch on the enamel surface in primary canines

In recent years with the introduction of laser in dentistry, numerous researches have been conducted to evaluate its efficacy for improving resin material bond on the enamel and dentin. Based on the available literature, no research has been performed on resin shearing bond strength by preparing the tooth surface with YSGG laser on the enamel of the primary teeth. The present study seeks to determine and compare resin shearing bond strength between two groups of surface preparation with acid etch and laser. Twenty primary canine teeth which were extracted for orthodontic purposes were collected and were halved with a diamond disc. Each of the halves was mounted in transparent acrylic resin. The teeth were then randomly divided into two groups; in group 1, surface preparation was done with YSGG laser and in group 2, the teeth were prepared with acid etching. Next, the composite was put on the tooth surface by a plastic matrix and cured. The shearing bond strength was measured with instron. The collected data were analyzed using Student's t-test and Kolmogorov-Smirnov statistical methods. The average bond strength was 27.87 +/- 6.136 mpa in the laser group [group 1] and 21.55 +/- 5.62 mpa in the acid etch group [group 2] demonstrating a statistically significant difference between the two groups [p<0/05]. It may be concluded that resin bond strength is significantly higher in group 1 [YSGG group] compared with Group 2 [acid etch group]

[Effect of Er,Cr:YSGG laser on fissure sealant retention: Comparative in-vitro study]

Use of pit and fissure sealants are safe and effective preventive procedures for occlusal caries. Long term retention of pit and fissure sealants is essential for their success and depends partly on the method of fissure preparation. Recently, new technologies such as laser and air abrasion have been used to increase bond of sealants. This in vitro study compared the effect of laser with other methods [air abrasion and conventional] on retention of sealants by measuring micro shear bond strength. This experimental in-vitro study used sound premolar teeth. They were sectioned mesiodistally in order to use the buccal and lingual surfaces. Samples were randomly divided into 3 groups. Group I samples were prepared with 37% acid phosphoric. Group II samples were exposed to air abrasion and then acid etching. Group III specimens were exposed to Er,Cr:YSGG [2W power] and then acid etching. Bonding was applied on all samples and sealants in microbore tygon tube [0.7 mm in diameter and 1mm height] were cured. Data on micro shear bond strength was measured and analyzed statistically by One-Way ANOVA and Tukey tests. Mean micro shear bond strength for group I, II, III, were 23.51[ +/- 6.9], 39.09[ +/- 15.11], 21.44[ +/- 6.18] MPa respectively. A significant statistical difference [P<0.01] was detected in group II [air abrasion with etching] compared with other groups. Considering the smooth surface enamel used in this study, it can be concluded that irradiation of the laser before etching can not increase fissure sealant retention. However, air abrasion technique before etching showed greater sealant retentions