Natural and synthetic photosensitizers activated by photodynamic therapy on enamel reconditioning rebonded to metallic brackets: an in vitro study.

OBJECTIVE: To evaluate the bond efficacy and failure rates of rebonded metallic brackets after enamel reconditioning with chemical 37% phosphoric acid (PA) and natural and synthetic photosensitizers activated by PDT. MATERIALS AND METHODS: A total of 50 non-cavitated, and cautiously extracted human premolars were congregated after sample size calculation. The enamel exterior was etched, washed, dried for adhesive application, and cured. Metallic brackets were then oriented and adapted to enamel surface using composite. Later, brackets were debonded from the surface via a Weingart plier. Enamel was finished for ensuing surface reconditioning. Ultimately, specimens were randomly distributed into five groups (n=10). Enamel surface before rebonding was reconditioned with curcumin photosensitizer (CP), riboflavin photosensitizer (RP), rose bengal photosensitizer (RBP), methylene blue photosensitizer (MBP), and 37% PA (control) respectively. After following reconditioning protocol, brackets were rebonded to the enamel exterior employing a composite adhesive system. Then, specimens were subjected to the universal testing machine for analyzing shear bond strength (SBS), and bond failures were predicted using an ARI index. One-way ANOVA and Tukey multiple comparison tests were used for statistical analysis at a variance value of p < 0.05. RESULTS: Enamel reconditioned with 37% PA demonstrated the highest SBS for bracket rebonding, and the lowest SBS was presented by CP actuated by PDT. Enamel reconditioned with RP and RBP corroborated the analogous SBS outcome to 37% PA. Likewise, enamel surface treatment with MBP revealed a statistically significant result to CP for metallic bracket rebonding. The most prevalent failure scores anticipated among groups were 0 and 1 indicating an adhesive failure with the exemption of group 5 (control) that encountered more score 2 cohesive failure on debonding metallic brackets from enamel exterior. CONCLUSIONS: Rose bengal and riboflavin photosensitizers activated by photodynamic therapy with low ARI scores have the potential to be used as viable enamel reconditioning alternatives to 37% phosphoric acid for rebonding metallic brackets.

Saturation of the biological response to orthodontic forces and its effect on the rate of tooth movement.

OBJECTIVES: Investigate the expression and activity of inflammatory markers in response to different magnitudes of orthodontic forces and correlate this response with other molecular and cellular events during orthodontic tooth movement. SETTING AND SAMPLE POPULATION: CTOR Laboratory; 245 Sprague Dawley male rats. METHODS AND MATERIALS: Control, sham, and 5 different experimental groups received different magnitudes of force on the right maxillary first molar using a coil spring. In the sham group, the spring was not activated. Control group did not receive any appliance. At days 1, 3, 7, 14, and 28, the maxillae were collected for RNA and protein analysis, immunohistochemistry, and micro-CT. RESULTS: There was a linear relation between the force and the level of cytokine expression at lower magnitudes of force. Higher magnitudes of force did not increase the expression of cytokines. Activity of CCL2, CCL5, IL-1, TNF-α, RANKL, and number of osteoclasts reached a saturation point in response to higher magnitudes of force, with unchanged rate of tooth movement. CONCLUSION: After a certain magnitude of force, there is a saturation in the biological response, and higher forces do not increase inflammatory markers, osteoclasts, nor the amount of tooth movement. Therefore, higher forces to accelerate the rate of tooth movement are not justified.