Effect of bleaching agents containing fluoride or calcium on enamel microhardness, roughness and permeability

Aim: To evaluate the effect of different in-office bleaching agents on the permeability, roughness and surface microhardness of human enamel. Methods: For evaluation of roughness and microhardness, 40 hemi-faces of 20 premolars were subjected to initial roughness (Ra parameter) and microhardness (VHN) measurements. Thirty-two premolar’s crowns were used for permeability test. Then, all specimens were randomly divided into four groups: C - without bleaching (control), HP35 - bleaching with 35% hydrogen peroxide (HP), HPF38 - 38% HP+fluoride, HPC35 - 35% HP+calcium. Final roughness (FR) and microhardness (FM) measurements were evaluated. For permeability, the 32 crowns were immersed in 1% sodium hypochlorite (20 min) and silver nitrate solutions (2 h) and subjected to developing solution under fluorescent light (16 h). Three sections from the crowns were analyzed in light microscope (100x) to evaluate the scores of permeability: Score 0 - no tracer agent penetration; Score 1 - less than half the thickness of enamel penetration; Score 2 - tracer agent reaching half the enamel thickness; Score 3 - entire enamel depth penetration, without reaching dentin and Score 4 - tracer agent reaching dentin. For roughness and microhardness evaluation were used one-way ANOVA and Dunnet post-test for independent samples, and t test for paired samples. For permeability, the data were analyzed by Kruskal Wallis and Dunn tests. Results: A significantly higher permeability and surface roughness were observed in groups HP35, HPF38 and HPC35 compared to the C group, as well as decreased microhardness (p<0.05). Conclusions: All bleaching agents increased permeability and surface roughness, and decreased microhardness of human enamel; thus, the addition of fluoride or calcium was not beneficial.

Stapedotomy and its effect on hearing – our experience with 54 cases.

Introduction: This study reviews the cases of stapedotomy and evaluates its effectiveness at improving hearing loss in patients with otosclerosis. Materials and methods: Retrospective review of patients’ records who had clinical and audiometric diagnosis of otosclerosis from January to December 2012. Results: A total of 54 stapedotomy surgeries (52 unilateral and 1 bilateral surgeries) were received. Average post-operative ABG for 0.5, 1, 2 and 4 KHz showed that 61.1% had complete closure of ABG (ABG < 10 dB) compared with 1.6% preoperatively and 85.2% had closure of ABG to within 20dB compared with 4.7% preoperatively (t – 13.89, p = 0.000). More than 94% had hearing improvement and 81.5% had ABG closure greater than 10 dB postoperatively (mean gain 23.38 ± 12.37, t = 13.89, p = 0.000). A total of 13% complications were recorded with TM perforation (5.6%) being the commonest complication. Conclusion: Stapedotomy is an effective surgical procedure for the treatment of otosclerosis which leads to improvement in patients’ quality of life. A favorable hearing outcome can be obtained by the combination of experienced hands with minimal surgical trauma and appropriate surgical technique.