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The effect of cleaner containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) for removing temporary cement remnants on dentin surface was evaluated. Flat dentin surfaces were wet-polished (Co) and HY-BOND temporary cement hard (Shofu) was applied to the surface. This temporary cement was removed using an air-scaler (Sc), brush (Br), or phosphoric acid and NaOCl (NC). A prototype cleaner containing MDP (Kuraray Noritake Dental, Tokyo, Japan) was used with agitation mode (MC+AG). KATANA Avencia block (Kuraray Noritake Dental) was luted with SA Cement Plus Automix (Kuraray Noritake Dental). Co showed significantly higher bond strength than Sc or Br (p<0.001 each). Bond strengths with NC (p=0.99) and MC+AG (p=0.38) did not differ significantly from that with Co. Transmission electron microscopy revealed sufficient interaction of MC+AG. Cleaner containing MDP can effectively remove temporary cement by agitation, and can be expected to improve the chemical bonding ability by binding more MDP to dentin.

Purpose:To analyze the causes of debonding of computer-aided design/computer-aided manufacturing (CAD/CAM) indirect resin composite premolar crowns with a focus on the morphological factors of the crown and abutment teeth. Methods: The clinical courses of 109 CAD/CAM indirect resin composite crowns were observed, and the patients' background characteristics, crown locations, luting methods, types of abutments, distal-most/non-distal-most molars, and types of resin blocks were confirmed. To investigate the influence of the morphology of the crown and abutment teeth, the 1) vertical dimension of the abutment teeth, 2) taper, and 3) thickness of the crown occlusal surface during events were measured from the three-dimensional digital data. The Kaplan-Meier method and multivariable Cox proportional hazard model were used for the statistical analyses. The nonlinearity of the effect of each comparison factor was included in the model. Results: Complications included 21 debonding cases, two crown fractures, five root fractures, and two core debondings. The cumulative no-debonding and nocrown-fracture rate over 1423 days (3 years and 11 months) was 77.4%. The multivariable Cox regression analysis revealed that the abutment teeth type of tooth (first or second premolar) (P = 0.02) and luting materials (P < 0.01) significantly influenced the debonding frequency. All morphological factors (1-3) significantly influenced the debonding. The hazard ratios and nonlinear graph indicated that the crown thickness was less effective than the vertical dimension and taper. Conclusions: The combination analysis of clinical outcomes and 3D digital data revealed that preparation of the abutment is important for avoiding crown debonding.

Coronal tooth lesions, such as caries, enamel cracking, and composite resin restoration cavities, have been observed by optical coherence tomography (OCT). This pilot study was performed to verify whether OCT could reveal details of root canals filled with resin core build-up. A dual-cure, one-step, self-etch adhesive system-bonding agent (Clearfil Bond SE ONE, Kuraray Noritake Dental) and dual-cure resin composite core material (Clearfil DC Core Automix ONE, Kuraray Noritake Dental) were used according to the manufacturer's instructions in root canals. OCT was performed at three stages of the core build-up: after the post space preparation, after bonding application, and after resin core fabrication. The cementum was removed in the cementum absent group and the root was left untreated in the cementum present group. Bubbles were observed in the resin cores and gaps formed between the resin core and dentin. In the cementum absent group, the internal structure of the root could be visualized clearly compared with the cementum present group. The root internal structure could be observed by OCT and the image became clearer when cementum was removed.

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