Water jet as a novel technique for enamel drilling ex vivo

To investigate the usage of a water jet for enamel drilling ex vivo, 210 individual extracted molars without lesions or fillings were collected. Then, the specimens were drilled by a water jet or a high-speed dental drill. The cavities of 50 teeth were reconstructed digitally by micro-computed tomography (micro-CT) to measure the height and width. The cavities of 10 teeth were longitudinally incised and their surfaces were observed by scanning electronic microscopy (SEM). After the cavities were filled, 50 fillings were vertically incised. The bonding interface between tooth and filling was observed by SEM. 50 teeth with fillings were stained in 0.1% rhodamine B solution, and then the dye penetration between tooth and filling was observed under the stereomicroscope and confocal laser scanning microscopy (CLSM). The bonding strength between enamel and filling of 50 teeth was simulated and predicted with finite element analysis (FEA). At 140–150 MPa and for 2–3 s, cavities were made with a depth of approximately 764 μm in each tooth. SEM showed the cavity surface in the water jet group had a more irregular concave and convex structure than that in the high-speed dental drill group. There was a trend that the microleakage and bonding width was smaller in the water jet group than in the high-speed dental drill group. FEA indicated that the stress on the resin surface was greater than on the enamel surface in the water jet group. Compared with the tooth drilled by a high-speed dental drill, the tooth drilled by a water jet gained better retention of the filling material and suffered less bonding strength on the enamel surface. Water jet drilling is effective for enamel drilling.

Individual biosafety barrier in dentistry: an alternative in times of covid-19. Preliminary study

ABSTRACT The return to dental practice in pandemic times is a new challenge due to the generation and dispersion of droplets and aerosols that may contain the SARS-CoV-2 virus, the etiological agent of covid-19. In the last months some droplet and aerosol containment strategies have been circulating on the internet, however, until now there is no evidence in the literature to prove the effectiveness of such barriers. Thus, using a microbial dispersion model with the fast handpiece, the aim of this preliminary study was to compare the dispersion caused by the the dental drill (DD) alone or in association with an individual biosafety barrier (IDBD / DD), which consisted of a layer of PVC film combined to a layer of polypropylene mounted on a frame. The dental drill was activated for one minute having had the water from the reservoir been replaced with a suspension of Lactobacillus casei Shirota. Petri dishes containing MRS agar were positioned at 50, 100 and 150 cm from the headboard of the dental chair at different angles (90 and 0 degrees). At 50 cm, the mean (standard deviation) of L. casei Shirota for DD was 13,554.59 (493.48) CFU, while for IDBD / DD was 570.67 (60.54) CFU (p <0.0001), establishing a 96% reduction. Considering these preliminary results, the individual biosafety barrier proved effective in reducing dispersion from the dental drill in this study model, which suggests that this barrier may be a viable option to optimize biosafety in the dental environment.