Effect of Er:YAG laser and sandblasting in recycling of ceramic brackets

Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet [Er:YAG] laser or sandblasting

Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars. The shear bond strength of all specimens was determined with a universal testing machine at a crosshead speed of 0.5 mm/min until bond failure occurred. The recycled bracket base surfaces were observed under a scanning electron microscope [SEM]. Analysis of variance [ANOVA] and Tukey tests were used to compare the shear bond strength of the 3 groups. Fisher exact test was used to evaluate the differences in adhesive remnant index [ARI] scores

Results: The highest bond strength belonged to brackets recycled by Sandblasting [16.83 MPa]. There was no significant difference between the shear bond strength of laser and control groups. SEM photographs showed differences in 2 recycling methods. The laser recycled bracket appeared to have as well-cleaned base as the new bracket. Although the sandblasted bracket photographs showed no remnant adhesives, remarkable micro-roughening of the base of the bracket was apparent

Conclusion: According to the results of this study, both Er:YAG laser and sandblasting were efficient to mechanically recondition retentive ceramic brackets. Also, Er:YAG laser did not change the design of bracket base while removing the remnant adhesives which might encourage its application in clinical practice

[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.