An In Vitro Evaluation of Human Enamel Surfaces Subjected to Erosive Challenge After Bleaching.

OBJECTIVES: This study aimed to evaluate whether tooth enamel bleached with hydrogen peroxide (H2 O2 ) is more susceptible to erosion when compared with unbleached tooth enamel; and whether the presence of calcium (Ca) in the bleaching gel influenced this process. MATERIALS AND METHODS: Enamel blocks were prepared from human molars, and submitted to surface microhardness analysis (baseline). Blocks were prepared and randomly divided into four treatment groups (n = 20): G1 and G2-bleached with 7.5% H2 O2 , with and without Ca, respectively; G3 and G4-bleached with 35% H2 O2 , with and without Ca, respectively. After bleaching, these groups were submitted to an erosive challenge with 1% citric acid. G5 and G6 (n = 20, each) were the negative (without bleaching) and positive controls (without bleaching, but with erosion), respectively. The percentage of surface hardness loss (%SHL), the 3D non-contact profilometry and Scanning Electron Microscopy (SEM) analyses were performed. RESULTS: G2 showed the highest %SHL after bleaching. G1 presented the lowest %SHL in comparison with G2, G3, G4, and G6 after erosion (p < 0.05), which was confirmed only by the SEM analysis. CONCLUSION: It is suggested that low concentration of H2 O2 with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge. CLINICAL SIGNIFICANCE: Low concentration of H2 02 with calcium can be recommended for at-home bleaching agents, which may avoid the mineral loss of bleached enamel after an erosive challenge. (J Esthet Restor Dent 29:128-136, 2017).

Oral bacteria adherence to suture threads: an in vitro study.

PURPOSE: This study investigated the adherence of oral microorganisms to different types of suture threads. METHODS: Pieces of thread were distributed on 24-well plates, according to the following groups: (G1) nylon, (G2) silk, (G3) polyglactin 910, (G4) polyglactin 910 with triclosan. Blank control (G5) consisted of one thread from each group. Adherence to thread tests was performed to observe adhesion of total microorganisms from saliva or two isolates of Prevotella intermedia (ATCC49046) and Fusobacterium nucleatum (ATCC51190). Brain-heart infusion (BHI) medium with or without bacterial inoculum (1.8 × 10(7) CFU/mL) was added to each well of microplates. The microplates were incubated in an anaerobic chamber at 37 °C, for 5 days for biofilm formation. RESULTS: There was no difference between the groups as regard to adhesion of F. nucleatum (p > 0.05). For P. intermedia, the threads in G1 and G4 showed a lower level of adhesion (p < 0.05), with no difference between them. Against total microorganisms, G1 presented a lower level of adherence (p < 0.05), followed by G4; and no difference was observed between G2 and G3. CONCLUSIONS: Total microorganisms and P. intermedia have different affinities to the tested suture threads, whereas F. nucleatum presented a similar adherence level. Among the threads, nylon (G1), followed by polyglactin 910 with triclosan (G4) presented the lowest microbial adherence level.