Non-invasive intravital observation of lingual surface features using sliding oral mucoscopy techniques in clinically healthy subjects.

To investigate intravital morphological features of the broader area of the lingual mucosa in clinically healthy subjects, and to attempt to evaluate subclinical conditions, we evaluated detailed intravital morphological features of the lingual mucosa using our newly developed oral contact mucoscopy techniques. Clinically healthy subjects (female: 19-22 years, average age: 20.27 years, and n = 28) were enrolled. A position indicator stain was placed on the lingual mucosal surface, and sliding images were captured and then reconstructed. In addition, the lingual mucosa was divided into six areas, and morphometry of the fungiform and filiform papillae was performed. The results were statistically analyzed. There were two morphological features among clinically healthy subjects involving the filiform papillae: the length of the papillae and the degree of biofilm (tongue coat) deposition. We defined a modified tongue coat index (mTCI) with scores ranging from 0 (tongue coating not visible) to 0.5, 1, 1.5, and 2 (thick tongue coating) for six sections of the tongue dorsum. No subjects received a score of 2. Significant differences were found in the mTCI between the six sections of the tongue dorsum, especially between the posterior areas and the lingual apex. The fungiform papillae of some subjects exhibited elongated morphological changes. Our findings suggest that magnified lingual dorsum examination of a broader area is especially important in accurate screening for subclinical or transient conditions of potential lingual mucosal diseases. For this purpose, our new oral mucoscopy and non-invasive intravital observational techniques were especially effective.

Intraoral electric potential via oral bacterial power generation -A novel mechanism of biofilm formation.

In the early stages of biofilm accumulation, the electric charge of the dental enamel and pellicle surfaces is known to be involved. We therefore investigated the relationship between oral hygiene and intraoral electric potential (IoP) in 45 male participants using a double-blind study. IoP, but not body surface electric potential, was loosely correlated with oral hygiene condition (Oral Hygiene Index; OHI). IoP was also loosely correlated with smartphone use; however, there was no significant correlation between smartphone use and OHI. IoP elevation might be caused by OHI elevation resulting from biofilm formation as an internal factor, with smartphone use as an external factor. This in vitro study revealed the generating capacity of Streptococcus mutans accompanied by biofilm accumulation using a microbial fuel cell. These results suggest that IoP elevation is caused by biofilm accumulation induced by power generation of oral bacteria, resulting in elevation of OHI.

Effects of air polishing on the resin composite-dentin interface.

The aim of this study was to examine defect depths and volumes at the resin composite-dentin (R/D) interface after air polishing with different particles and spray angles. Samples were 54 dentin specimens that were formed in saucer-shaped cavities filled with resin composite. Each specimen was air polished with either sodium bicarbonate (NaHCO3) or one of two glycine (Gly) powders. The air polisher was set at angles of 90° to the interface and at 45° to the interface from both the dentin and resin composite sides. Air polishing with Gly powder produced defects with less depth and volume than NaHCO3 powder (p < 0.05). Air polishing with a spray angle of 45° to the interface from the resin composite side produced fewer defects (p < 0.05) than polishing from the dentin side. Air polishing to the R/D interface from the resin composite side produced fewer defects to the interface because the hardness of the resin composite was higher than that of dentin.