Abstract : This study aimed to identify the root and root canal morphology of maxillary first (P1) and second (P2) premolars in Japanese patients using computed tomography (CT). The subjects were 200 Japanese individuals (100 males, 100 females) who had undergone CT for investigation of oral pathologies in the Department of Radiology at our hospital. For all subjects, one root was present in about 80% of P1 and >90% of P2. Using Turner's classification, one root and one apex were observed in about 50% of P1 and >90% of P2 in both sexes. P2 never showed a complex root in females, but two complex roots were observed in males. P1 predominantly (about 83%) showed two root canals, however, P2 predominantly (about 70%) showed one root canal. In addition, two root canals were more frequent in P1 than in P2 in both sexes (p<0.01). Using Vertucci's classification of the anatomy of one root in P1 and P2, two root canals in P1 were mostly Type Ⅳ (two root canals did not join in the morphology of two root canals and two apical foramina) or Type Ⅱ (two root canals joined in the morphology of one root canal and one apical foramen).

Abstract : Disinfection of the root canal system is essential in endodontic therapy. However, due to the complex anatomical morphology, it is impossible to completely eliminate infecting microorganisms. We have reported that electromagnetic stimulation has an activating effect on osteoblastic cells as well as a bactericidal effect and suggested that direct electromagnetic stimulation may be applicable for refractory apical periodontitis. Consequently, we developed Electro-Magnetic Apical Treatment (EMAT), with the aim of promoting rapid healing of periodontal tissue. The purpose of this study was to assess the efficacy of EMAT for apical periodontitis.

 Methods : 74 maxillary anterior teeth with periapical lesions (>5.0 mm in diameter) were treated. 37 teeth were stimulated by the EMAT device, and 37 teeth were not stimulated. Radiographic follow-up was performed to evaluate the healing effect at 12 months postoperatively.

 Results : The success rate (97.3%) in the EMAT group was statistically higher (p<0.01) than that in the non-stimulated group (73.0%). In the successful cases, the average reduction rate of periapical lesions was 9.7±5.2%/month in the EMAT group, which was significantly higher (p<0.01) compared with the non-stimulated group (4.9±1.7%/month).

 Conclusions : These results suggest that EMAT accelerates the healing process of periodontal tissue.

Abstract : Objective : The antimicrobial effect of iontophoresis was investigated comparing the uses of sodium fluoride solution (NaF), ammonia silver solution (ASH), iodine-zinc iodine solution (IZI), and diamine silver fluoride solution (DSF), using different methods of applying electric current.

 Methods : E. faecalis ATCC 19433 was used as the test strain. After incubation of the test strain, the medium was adjusted to 10⁶ CFU/mL. A lacuna was made at the apex of the apical lesion simulated in each periapical lesion model using a root canal model. Then, 30 μL of sterile saline agar, 30 μL of defibrinated sheep blood agar containing the test microorganism, and 70 μL of sterile saline agar were overlaid in each lacuna in order.

 Different agents, i. e. NaF, ASH, IZI, and DSF, were delivered with anodic and cathodic currents of 1 mA applied for a certain length of time.

 After iontophoresis was completed, the drugs were removed from the root canal of the models. Subsequently, the agar containing the test microorganism was collected from the lacunae and diluted appropriately to count the number of colonies (log CFU/mL).

 Results and conclusion : The antimicrobial effect varied depending on the current application method for iontophoresis and the choice of medication. The cathodic current applied to NaF showed the most pronounced antimicrobial effect, achieving a killing rate of 99.99% in 25 minutes and a level below detection limit in 50 minutes, which was followed by the cathodic current applied to ASH. At 25 minutes and thereafter, the cathodic currents applied to NaF, ASH and IZI showed significant differences compared to the control. The anodic current with neither ASH nor IZI applied exhibited a significant difference compared to the control, showing no antimicrobial activity. While no black discoloration was observed in the models treated with NaF and IZI, the models treated with ASH and DSF showed black discoloration.

Abstract : Purpose : Our aim was to assess maxillary molar root and root canal morphology in a Japanese population using dental cone-beam computed tomography (CBCT). Materials and methods : We analyzed CBCT images of 484 maxillary molars (240 first molars and 244 second molars) from 124 patients. The number of roots and their morphology, the number of canals per tooth and the root canal configurations according to Vertucci's classification were evaluated. Types of root fusion and their prevalence were also evaluated. Results : Most of the maxillary first and second molars had three roots (99.6% of first molars and 85.7% of second molars). Four roots were present in 0.4% of maxillary first molars and 2.0% of maxillary second molars. The first molars had a higher prevalence of two root canals in the mesiobuccal root than the second molars. The most common canal configurations in the mesiobuccal root of both molars were typesⅠ and Ⅳ. The frequency of root fusion was higher in the second molars than the first molars ; fusion of the mesiobuccal and distobuccal roots was most common. Conclusion : In the case of unclear or complex root and root canal morphology in the maxillary molars, CBCT imaging can assist clinicians in making an accurate diagnosis and in planning treatment.