Purpose: Root canal sealers consisting mainly of zinc oxide powder and eugenol liquid exhibit eugenol-related cytotoxicity. However, paste-type sealers with appropriate mixing ratios have been developed to reduce eugenol cytotoxicity. In this study, we aimed to compare the in vitro characteristics and in vivo biocompatibility (in rat subcutaneous tissue implantation) of three sealers: paste-type eugenol-based sealers (CANALS-PASTE (CaNP), NISHIKA CANAL SEALER Eugenol Normal E-N (NS)), and a powder-liquid-type eugenol-based sealer (CANALS (CaN)).

 Method: After the sealers were mixed and hardened, compressive strength and diameter change tests were performed. The amount of eugenol released over time for each sealer (hardening conditions: 0 (immediately after mixing), 3 hours, and 72 hours after mixing) was measured. Antibacterial tests were performed by incubating the hardened sealers with Streptococcus mutans and Enterococcus faecalis, and the turbidity was measured after 24 hours of incubation. Cytocompatibility testing was performed by culturing NIH-3T3 fibroblast cells with the sealers, and water-soluble tetrazolium salt (WST) -8 activity was measured after 24 hours of incubation. In addition, NIH-3T3 cells around the sealers were immunostained with vinculin/F-actin and observed under a fluorescence microscope. Biocompatibility of the sealers was determined by implanting the hardened sealers into the dorsal subcutaneous tissues of rats, with CD68 expression measured 10 days post-implantation. Histological observations and scoring of the degree of inflammatory cell infiltration were performed at 10 and 35 days post-implantation.

 Results: The CaNP group exhibited a significantly higher compressive strength than the others. No differences in the diameter change test were observed in all samples. Eugenol release increased time-dependently in all samples, with the CaNP and NS groups releasing similar amounts, and the CaN group releasing significantly more. The turbidity of the bacteria cultured with the sealers decreased in all groups, with the turbidity in the CaN group decreasing the most. The CaNP group showed significantly higher WST-8 activity, cell adhesion and spreading close to the CaNP. The intensity of CD68 expression was significantly higher in the NS group than in the other groups. Moreover, the inflammatory cell infiltration score of the NS group was higher than those of the other groups at 35 days postoperatively.

 Conclusion: The CaNP sealer exhibited greater biocompatibility than the NS and CaN sealers. In addition, CaNP produced a smaller inflammatory response than NS.

 Purpose: Thorough supragingival and subgingival plaque control is essential for the successful treatment of periodontitis. Recently, wide-flocked toothbrushes have become popular for effective plaque control. However, the appropriate method of using wide-flocked toothbrushes has not yet been determined. Therefore, in this study, the optimal method of effective scrubbing with wide-flocked toothbrushes was examined using artificial plaque on a tooth model.

 Materials and methods: For the experiment, a wide-flocked toothbrush with tapered bristles and a wide-flocked toothbrush with flat bristles were used. The removal of supragingival and subgingival plaque was evaluated by measuring the area of artificial plaque remaining on the tooth models after scrubbing. The brushing conditions, which included a load of 200 gf and stroke frequency of 30 times, were kept constant, and all experiments were conducted using a brushing machine (brushing stroke width: 5 mm and 15 mm, head speed: 180 and 300 strokes/min). The resulting data were statistically analyzed using the Mann-Whitney U test and Steel-Dwass test to compare the removal rate of artificial plaque.

 Results: The findings showed that the plaque removal with wide-flocked toothbrushes was associated with the brushing stroke width and head speed. The supragingival artificial plaque removal rate was significantly higher with a 15-mm stroke width and 180 strokes/min compared with other conditions (removal rate: 18.6% with 5-mm stroke width and 180 strokes/min, 33.5% with 15-mm stroke width and 180 strokes/min). Moreover, the subgingival plaque removal rate was significantly higher using tapered-bristle wide-flocked toothbrushes compared with flat-bristle wide-flocked toothbrushes.

 Conclusion: The findings of this study suggest that optimal brushing can be achieved using wide-flocked toothbrushes with a stroke width of 15 mm and stroke rate of 180 strokes/min (i.e., a speed of -30 reciprocations/10 s).

 Purpose: Osteogenesis imperfecta (OI) is a congenital disease which occurs in approximately one in 20,000 people. The dental characteristics of OI are dentinogenesis imperfecta and following root canal obliteration. We report a case of endodontic retreatment of an OI patient with good prognosis by using cone-beam computed tomography (CBCT) and a dental operating microscope on the mandibular central incisor with chronic apical periodontitis.

 Case: A 12-year-old female with OI had teeth mobility and biting pain in her lower front teeth after eating a snack at the end of February 2020. Fixation of the lower front teeth and observation were performed at the pediatric dentistry department of Osaka University Dental Hospital. An apical lesion of #41 was observed after a few days, however, the tooth continued to be observed under fixation due to obliteration of the root canal and the difficulty of its treatment. She was referred to a conservative dentistry clinic in June 2020. From dental radiography and CBCT of #41, a radiolucent area at the apex and obliteration of the root canal from the incisal edge to the middle of the root were observed. Based on a diagnosis of chronic apical periodontitis, root canal treatment was performed on #41. However, although root canal treatment was performed under a microscope several times, the orifice of the root canal could not be found. To check the positional relationship between the searching point and the original root canal, the CBCT was retaken. The CBCT images showed that the searching point was off distally and lingually from the original one. After modification, the original canal was found and the root canal treatment was performed. In December 2020, all symptoms had disappeared. The root canal was obturated, and restored with composite resin after one month. At one year after the root canal obturation, the radiolucent area had disappeared and there were no clinical symptoms on #41.

 Discussion and conclusion: Patients with OI often suffer from tooth crown fracture, and their dental management requires attention. In the present case, we obtained good healing through proper root canal treatment of the apical periodontitis of the OI patient, whose teeth are considered difficult to treat. Even in the extremely stenosed tooth, we could perform root canal treatment by CBCT imaging at the proper timing and by using a dental operating microscope.

 Objective: Periodontal surgery for drug-induced gingival hyperplasia resulting in pseudopockets is generally performed by gingivectomy through an external oblique incision, but in the present case the patient also presented with true pockets due to extensive chronic periodontitis, so modified Widmann flap surgery was performed while also considering esthetic aspects. However, a slight fibrotic gingival swelling remained on the labial aspect of the maxillary anterior teeth after the operation, so we used a CO₂ laser as a corrective treatment and report good results.

 Case: The patient, a 57-year-old woman, presented to the clinic with a chief complaint of severe periodontal disease, of which she had been informed by a local doctor. She had a history of hypertension and had been taking amlodipine tablets 5 mg for 8 years. She had been aware of gingival swelling since the beginning of taking the medication, and visited a nearby doctor because the gingiva of her upper right bicuspid had swollen since one month ago, and after removal of a ceramic-fired metal crown and scaling, no improvement was observed, so she was referred to our clinic. At the initial examination, redness and fibrotic swelling of the gingiva were observed in the whole jaw, especially, fibrotic swelling in the anterior teeth of the upper and lower jaws was remarkable. Radiographs showed mild to moderate horizontal bone resorption in both jaws. Based on the above, a diagnosis of extensive chronic periodontitis and drug-induced gingival hyperplasia was made.

 After basic periodontal treatment and re-evaluation, modified Widmann flap surgery was performed on both jaws due to residual true pockets. Subsequently, significant improvement of the true pockets was observed, but fibrotic gingival swelling remained on the labial aspect of the maxillary anterior teeth, so gingivectomy with a CO₂ laser was performed as a corrective treatment for esthetic and cleanability reasons, and after follow-up, a final restoration was placed.

 Conclusion: In this case, periodontal surgery was performed for drug-induced gingival hyperplasia with true pockets, while taking esthetic considerations into account, and the prognosis is good. It is suggested that the use of a laser may expand the treatment options in the future.

 Purpose: To describe the long-term outcomes of a case of severe gingival melanin removal using an erbium-doped yttrium aluminum garnet laser (Er: YAG) laser (Dentlite, HOYA ConBio) under the microscope.

 Methods: The patient provided informed consent prior to the presentation of this case report. A 29-year-old male, with a smoking habit of nearly 10 cigarettes per day, presented with a chief complaint of esthetic disorder in the mandibular anterior gingiva. Extensive melanin deposition was observed on the attached gingiva of the mandibular anterior teeth. Before the melanin removal procedure, he was first advised to quit smoking to prevent recurrence. Then, we planned gingival ablation of the melanin pigmentation area using an Er: YAG laser under a microscope.

 Results: The advice to quit smoking was successful. Local anesthesia was administered to the mandibular anterior teeth, and gingival ablation of melanin pigmentation sites was performed using the Er: YAG laser at 10-30 Hz and 80 mJ (panel display), using contact tips under water spray. By performing the microsurgery, the remaining subtle pigmented areas were easily visible, allowing for a more precise procedure. The magnified view facilitated careful tissue ablation in areas susceptible to postoperative gingival recession, such as the gingival margin and interdental papillary area. There was no obvious coagulation or carbonization on the laser-irradiated surface, and connective tissue exposure was observed after epithelial tissue ablation. Postoperative analgesia or antibacterial medication was not administered because invasion was minimal. Epithelialization was completed 7 days postoperatively. Melanin removal on the buccal side of the mandibular anterior teeth was divided into three sessions to complete the treatment. At 1 year and 6 months postoperatively, the improved gingival esthetics were well maintained. Mild to moderate recurrence was observed 16 years later.

 Conclusion: Minimally invasive removal of severe melanin pigmentation of the gingiva under a microscope using an Er: YAG laser resulted in a favorable healing outcome. This case suggests that microsurgical depigmentation using an Er: YAG laser could achieve and maintain medium-term sound outcomes for the treatment of gingival esthetic disorders.