This case report describes non-surgical micro-endodontic treatment of a mandibular second molar that had a disto-lingually rotated crown fused with another single-rooted tooth at the central buccal aspect. Cone-beam computed tomography (CBCT) demonstrated C-shaped root configuration with two ribbon-shaped canals, and the distal canal joined to the open-apex canal of the "extra" tooth. Under a dental operating microscope, selective ultrasonic instrumentation of the fin-like canal areas and placement of an apical plug with mineral trioxide aggregate were performed, resulting in complete radiographic healing. This report highlights that dental operating microscopic magnification, aided with CBCT, is an absolute prerequisite for implementing contemporary treatment strategies according to given anomalous morphology, and thereby for overcoming endodontic challenges associated with fused teeth.

In this study, we investigated whether it is possible to remove the smear layer using hydroxyl radicals (•OH) generated by photochemical reactions. Hydrogen peroxide (H₂O₂) was irradiated with a 405-nm light-emitting diode device to generate •OH. The amounts of •OH generated during irradiation for 10, 20, and 30 s were measured using the electron spin resonance spin-trapping method, and the amounts were compared between the H₂O₂ group (H₂O₂ without irradiation) and •OH group (H₂O₂ with irradiation). In addition, 14 smear specimens were prepared from seven roots; the specimens were treated with the H₂O₂ group, •OH group and control group (PBS only) for 3 min, then the root canal surfaces were observed by scanning electron microscopy.

In the •OH-group, the amount of •OH generated was increased by the irradiation in a time-dependent manner; the smear layer was partially removed, and a few dentin tubules were observed. In contrast, almost no •OH was generated in the H₂O₂ group. The root canal surfaces of the control and H₂O₂ groups were densely covered with a smear layer, and no dentin tubules were observed.

These results suggested that the •OH generated by the photochemical reaction can remove the smear layer.

Only a small number of reports are available on the treatment of peri-implantitis using an operative microscope. This article reports a clinical case of peri-implantitis that was successfully treated using a modified procedure of minimally invasive periodontal surgery, which is a surgical procedure reported by Nagao (2015) for treating periodontal diseases of the natural teeth.

It is well known that root canal treatment of maxillary molars is made difficult by root fusion and complicated root morphology. In addition, the root apices of maxillary molars are in close proximity to the maxillary sinus, often causing odontogenic maxillary sinusitis. Two cases of this type of molar, in which a microscope and cone-beam computed tomography (CBCT) were needed for proper root canal treatment, are reported. Satisfactory results were obtained in both cases.

A patient was referred for endodontic retreatment of a mandibular molar. A diagnosis of Previously Initiated Endodontic Treatment with Asymptomatic Periradicular Periodontitis was confirmed. Preoperative digital imaging revealed a complex root canal anatomy as well as moderate peri-radicular pathosis.

Endodontic treatment was recommended and completed in conjunction with advanced adjunctive therapy.

Gum retractors, spoon excavators, and explorers are used to secure the view in the periodontal pocket. However, they are inadequate for sustained visualization of the operative field during a procedure. The author devised a technique to open the periodontal pocket using an absorbent paper point. This technique is referred to as micro-retraction. It is performed under a microscope and allows for widening of the treatment area, maintenance of clarity, biological debridement, and reduction of invasion.