Effects of 810nm diode laser irradiation on flexural strength of dentin: an in vitro study

Thermal changes in laser assisted root canal therapy with the use of diode laser can predispose tooth structure to the fracture. This study evaluated the changes in flexural strength of dentin blocks after diode laser irradiations [810 nm]. A total of 60 dentinal blocks were prepared from freshly extracted teeth in three different thicknesses [300, 500 and 1000 micro m] and 20 sections in each of these thicknesses were divided randomly to the test and control groups. Samples in the test groups were irradiated at 2W power setting by scanning movement of 2mm/s of diode laser, and the controls were stored in normal saline. The flexural strength of samples was evaluated by UTM [Universal Testing Machine]. Data analysis was done with the SPSS Software 11.5. Samples of 300 micro had the lowest flexural strength [mean: 71/65 mpa] followed by 500 [116.64 mpa] and 1000 micro [217.56 mpa]. Statistical analyses showed that after laser irradiation, the flextural strength in the samples of 300 micro was significantly lower than that in the other groups [500 micro, 1000 micro] [P= 0.017]. Within the limits of this study, diode laser irradiation in laser assisted root canal therapy has no significant effect on flexural strength of root dentinal walls with the thickness of more than 500 micro. Although in areas with critical dentinal width [

[Effect of pulp tester probe placement site on the response of maxillary anterior teeth]

Electric pulp testing is used for diagnosis of the pulp status. This test is technique sensitive and hence may elicit positive or negative false response in case of inaccurate use. The optimal site for placement of the probe tip has not been determined. The aim of this study was to evaluate the effect of pulp tester probe placement site on the response of maxillary teeth. A total of 378 teeth [126 central incisors, 126 lateral incisors and 126 canines] in 67 voluntary 20-35 year-old patients were selected. Three sites on each tooth [incisal edge, labial and lingual surfaces] were tested with an electrical pulp tester and responses were recorded. Data were analyzed by Repeated Measure ANOVA test. The central incisor teeth showed significantly lower sensation threshold than lateral incisor and canine teeth [P<0.001]. The incisal edge of tooth were significantly more sensitive compared to labial and lingual surfaces [P=0.008]. This study showed that the optimum site for placement of pulp tester probe was incisal edge.