From the perspective of prevention of secondary caries or periodontal disease, good conformance of a prosthesis is an essential condition for retaining long-term, stable function within the mouth.

The use of zirconia in crown restorations has become common in recent years for reasons such as the esthetic demands of patients and contact dermatitis (metal allergy). Advances in milling technology have led to improvements in the margin conformance accuracy of zirconia crowns, but the conformance accuracy is by no means exceptional in comparison to cast metal crowns.

The use of a microscope at all stages of the fabrication of zirconia crowns, including preparation, taking the impression, and processing, is extremely useful for producing crowns with high conformance accuracy that retain esthetics.

This paper introduces the use of a microscope by dentists and dental technicians in the fabrication of zirconia crowns with good conformance.

In root canal treatment for elderly people, it can be difficult to locate the root canal orifices because of narrowing of the pulp chamber due to calcification. However, there are cases of young people in which calcification has occurred and progressed due to stimuli, such as repeated treatment of a diseased tooth, making the root canal orifices difficult to locate. In the present case, a diseased tooth (#16) of this type was treated. A microscope and instruments essential for such treatment were required in order to properly locate the root canal orifices in order to enable root canal treatment.

The use of a microscope during implant treatment can improve the accuracy of the procedure; however, there can be drawbacks, such as difficulty in understanding the direction at the time of implantation and difficulty in taking an impression to load the prosthesis. Guided surgery in operative treatment and the taking of optical impressions using an intraoral scanner during prosthodontic treatment may compensate for these drawbacks.

Unfortunately, it is not uncommon to encounter cases of tooth fracture in everyday clinical practice. In clinical tooth fracture, the direction of the fracture depends on the site, and in tooth root fractures, the buccolingual direction is common in premolars and the mesiodistal direction is common in molars. Here, in order to investigate the probability of fracture depending upon the anatomical structure of the tooth root, we constructed models of one-third of the root on the crown side of premolars with two roots based on cone-beam computed tomography (CBCT) coronal sections, and we carried out a structural analysis using frames. The results suggest that if a dividing wall is removed in order to treat two root canals as a single canal, stress concentrates in a buccolingual direction and there is a high probability of fracture occurring from the inside toward the outside.

Rubber dam moisture control is an important measure for prevention of infection and as a precaution against medical error in root canal and other dental treatments. Here, members of the Japan Association of Microscopic Dentistry were surveyed by means of a questionnaire on the frequency of rubber dam use. The questionnaire was given to 1,148 dentists who are regular members of the Japan Association of Microscopic Dentistry and responses were received from 349, a response rate of 30.4%. Rubber dam moisture control was used in root canal treatment for “all cases” by 57% of respondents, and when “depending on the case” was included, the rate rose to 93%. A rubber dam was used for composite resin filling for “all cases” by 10% of respondents, “depending on the case” by 69%, and was “not used” by 19%. It was conjectured that rubber dam moisture control was also used in other prosthetic treatment.