RESUMO
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
RESUMO
Statement of Problem: Tooth caries is influenced by different biochemical characteristics of saliva. As hydroxyapatite is the main component of enamel, salivary ion activity product for hydroxyapatite [IPHA] as well as alkaline phosphatase may be attributed to dental caries
Purpose: The aim of the present study was to compare salivary buffering capacity, alkaline phosphatase and IPHA of adults according to the dental caries and age
Materials and Method: One hundred and twenty 19 to 44 years old male individuals were divided into four groups according to the dental caries rate and age: group 1: 19-35 years old low dental caries [DMFT <5]; group 2: 19-35 years old high dental caries [DMFT 5<]; group 3: 35-44 years old low dental caries [DMFT <11] and 35-44 years old high dental caries [DMFT 11<]. Five milliliter of unstimulated saliva was collected, and then buffering capacity, the level of alkaline phosphatase activity and IPHA was determined for each sample. Data was analyzed by soft ware SPSS using two way ANOVA, Friedman and Mann-Whitney tests
Results: Mean and standard deviation of buffering capacity of group 1 to 4 was 2.66 +/- 0.54, 2.64 +/- 0.56, 2.70 +/- 0.70 and 2.26 +/- 0.82, respectively. The difference was not significance [p= 0. 305]. Mean and standard deviation of alkaline phosphatase activity of group 1 to 4 was 5.82 +/- 2.91, 5.30 +/- 1.52, 4.77 +/- 1.82 and 4.55 +/- 1.61, respectively. There was no significant difference [p= 0.692]. Mean and standard deviation of IPHA of group 1 to 4 was 29.39 +/- 0.61, 29.51 +/- 0.76, 29.14 +/- 0.56 and 29.75 +/- 0.75, respectively. The difference was significant [p= 0.049]
Conclusion: Based on the results of the present study, buffering capacity and the level of alkaline phosphatase couldn't affect dental caries, independently. However, the higher value of IPHA may be attributed to the higher dental caries rate. Ageing decreases alkaline phosphatase activity
RESUMO
Statement of Problem: Free surface energy of substrate is an important factor for adhesion. High free surface energy results in increased wetness and better adhesion
Purpose: The aim of the present study was to evaluate the effect of different rinsing times after cutting with a suggested coolant on the free surface energy of the dentin
Methods and Material: In this in-vitro experimental study, 75 intact human premolar were randomly assigned into 5 groups: 1] Cut with water coolant, 5 seconds of rinse with water. 2] Cut with water coolant, 5 seconds of rinse with water, etch, rinse. 3] Cut with a suggested coolant [0.5 surfactant/HLB=7], 5 seconds of rinse with water. 4] Cut with a suggested coolant, 10 seconds of rinse with water, and 5] Cut with suggested coolant, 15 seconds of rinse with water. Free surface energy was measured by estimating the contact angle. The statistical analyses were performed using one-way ANOVA and Tukey tests
Results: The surface energy means [dynes/cm] of groups 1 to 5 were 75.87, 46.00, 74.86, 72.64 and 70.05, respectively. The results of one-way ANOVA showed a significant difference among the five groups [p =0.000]. The Tukey test showed that except groups 1 and 3 [p =0.678], there was a significant difference in all the other groups [p <0.05]
Conclusion: Etching reduces the dentin surface energy. The surface free energy of the cut dentin with a surfactant as a coolant and then rinsing with water for 5 seconds is equal to dentin which is not etched. Rinsing for more than 5 seconds [10 or 15 seconds] reduces the dentin surface energy