In-office bleaching gel with 35% hydrogen peroxide enhanced biofilm formation of early colonizing streptococci on human enamel.

OBJECTIVES: To compare the effects of 25% and 35% hydrogen peroxide in-office bleaching systems on surface roughness and streptococcal biofilm formation on human enamel. METHODS: Enamel specimens (3mm×3mm×2mm, n=162) from human permanent teeth were randomly divided into 3 treatment groups (n=54 each): (1) control, (2) bleached with 25% hydrogen peroxide (Zoom2™), and (3) bleached with 35% hydrogen peroxide (Beyond™). The enamel surface roughness was measured by a profilometer before and after treatments. Subsequently, the treated enamel specimens were randomly placed into 3 subgroups (n=18 each) and incubated with: (1) trypticase soy broth control, (2) Streptococcus mutans culture and (3) Streptococcus sanguinis culture for 24h. Biofilm formation was quantified by crystal violet staining. The biofilm structure on three specimens from each group was visualized by scanning electron microscopy. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests with Bonferroni corrections. Significance level was set at p<0.05. RESULTS: Both bleaching systems significantly reduced enamel surface roughness comparing to the control group (p<0.001), but there was no difference between the two treatment groups. Remarkably, S. sanguinis biofilm formation was significantly higher on enamel specimens bleached with 35% hydrogen peroxide than other treatments (p<0.001), but was lower on those bleached with 25% hydrogen peroxide (p<0.001). In contrast, no difference in S. mutans biofilm formation was observed among the three treatment groups. CONCLUSION: Both 25% and 35% hydrogen peroxide caused similar degrees of reduction in enamel surface roughness. Nevertheless, bleaching with 35% hydrogen peroxide appeared to markedly promote S. sanguinis biofilm formation. CLINICAL SIGNIFICANCE: The increase of early colonizer biofilm raised concerns over adverse effects of in-office bleaching on plaque formation. This should be further investigated in vivo and efficient plaque control should be emphasized after bleaching with high concentrations of hydrogen peroxide.

Dimensions for midline and paramidline andibulotomy: a radiographic study in the dentate Thai population.

BACKGROUND: Mandibulotomy is an important surgical approach of the oral cavity, oropharynx, and parapharyngeal space. OBJECTIVE: To provide dimensions for placement of bone cuts for midline (between two central incisors) and paramidline (between lateral incisor and canine) mandibulotomy. MATERIAL AND METHOD: Two hundred and sixteen periapical radiographs with the mandibular anterior teeth of 72 healthy Thai dental patients (30 males, 42 females) were selected. The angles between the long axes of the two central incisors (M) and between the lateral incisor and canine (PM) were bilaterally measured using computerized imaging. The horizontal distances (at crestal, middle, and apical levels) between the roots and the alveolar bone heights of the aforementioned teeth were also measured. RESULTS: The angles between the PM (0.00-9.26 degrees) were less convergent than those between the M (0.00-11.66 degrees) (p < 0.05). The distances between the PM were 0.60-8.03 mm, whereas those between the M were 0.47-6.63 mm (p < 0.05). Mean alveolar bone height is 15.88 +/- 1.72 mm in the canine. CONCLUSION: The paramidline mandibulotomy is done in a wider space than the midline cut and could have a better chance to avoid the extraction of a central incisor and preserve the origin of the genioglossus, geniohyoid, and digastric muscles.