Haruka Kusakari

Bactericidal efficacy of carbon dioxide laser against bacteria-contaminated titanium implant and subsequent cellular adhesion to irradiated area

The aim of this study was to assess CO2 laser ability to eliminate bacteria from titanium implant surfaces. The changes of the surface structure, the rise in temperature, and the damage of connective tissue cells after laser irradiation were also considered.

Long‐term changes of hydroxyapatite‐coated dental implants

There are many controversies about the long-term prognosis of hydroxyapatite (HA)-coated implants. Failure may be related to compositional and structural changes of the coating occurring during implantation. Two retrieved and two unused HA-coated blade-type implants were examined by stereomicroscopy, secondary electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electron probe microanalysis. The objective was to investigate the HA morphology, composition, and structure, and to characterize the changes that occurred in the retrieved implant coatings. Retrieved implants presented partial loss of the coating, especially at the apical and mesiodistal edges. Remaining HA was thick and flattened in the cervical and central areas and gradually thinner and rougher towards the apical and mesiodistal edges. Increase of Cl and Mg, decrease of OH, and X-ray diffraction peak broadening were found in the retrieved implant coatings, in comparison with the unused implants. Morphological changes of the retrieved implants seem to depend on stress values in the surrounding bone and on implant mobility. Compositional changes and increased amount of lattice imperfections appeared in the retrieved implant coatings, as a result of ion substitutions in the apatite lattice. However, the present study could not confirm the influence of these changes on implant failure.

Stability of zirconia-toughened bioactive glass-ceramics: in vivo study using dogs

The strength of zirconia-toughened glass-ceramic composite was measured after subcutaneous implantation in dogs. The bending strength was not degraded at all 12 weeks after implantation. Scanning electron microscopy revealed that the composite reacted very slowly with body fluid. The thickness of the reaction layer was about 10 μm in depth after 12 weeks, and was less than the critical flaw size (approximately 30 μm) estimated from the bending strength and the fracture toughness. We found that the zirconia-toughened glass-ceramic composite exhibited high strength in living body fluid for a long period.

Retention and failure mode after cyclic loading in two post and core systems.

Retention of a prefabricated post and composite resin core system was compared with that of a cast post and core restoration in anterior maxillary teeth on which root canal preparations, enlarged in the coronal part, were performed. The effect of cyclic loading on restoration retention was also investigated. Retention of restorations not subjected to cyclic loading was not influenced by post type, but loaded prefabricated post restorations showed lower retention than both loaded cast post and core restorations and nonloaded prefabricated post restorations. After dislodgement, the failure mode was also determined. The results of this study suggest that if a canal requires extensive preparation, a well-adapted cast post and core restoration may be more retentive than a prefabricated post restoration that does not match the canal shape.

The Influence of Nonworking Side's Contacts to the Response of the Jaw Closing Muscles.

The influence of nonworking sides contacts was investigated in vivo in the eccentric position to the response of the jaw closing muscles during clenching. This study was performed by changing the degree of clenching and the distance between upper and lower canines on the working side. Furthermore, the distance between the lower second molar and a splint inserted on the upper molars was changed using various thicknesses of metal plates. The thickness of the plate which allowed the first occlusal contact on the nonworking side during clenching was called D0.At 100% maximum voluntary clenching (MVC) and a distance of 1.5 mm between the upper and lower canines on the working side, the nonworking sides temporal muscle activity at D0 showed the lowest value. At the edge-to-edge contact of the working sides canines, the same results were obtained. However, at 50% MVC and the distance of 1.5 mm between the upper and lower canines, the activity, when no contact on the nonworking side was allowed, showed the lowest value.These findings indicate that nonworking sides contacts like that at D0 protect physiologically the temporomandibular joint from hypermobility during clenching in the eccentric position, and this protection is related with the degree of clenching.

Effect of Low Power Laser in Bone Histomorphometry

There are some reports concerning the effect of low power laser upon bone regeneration(1, 2). And in dentistry, improved postsurgical wound healing after tooth extraction, alveoplasty, implantation and so on, has been examined on the clinical bases.

[Follow-up study of periodontal tissues around the abutment teeth in Konus telescope denture].

The purpose of this study was to evaluate the periodontal tissues around the 47 abutment teeth in patients with advanced periodontitis for 5 years maintenance periods. The periodontal and prosthetic treatment were carried out and 16 Konus telescope dentures were applied for 11 patients. During 5 years maintenance therapy, periodontal conditions were observed once a year assessing probing depth, attachment level, tooth mobility index, gingival index, marginal alveolar bone height, width of periodontal ligament and loss of lamina dura. The results showed that increase of probing depth in 0.61 mm and attachment loss in 0.78 mm were observed for 5 years. A slight gingival inflammation occurred and tooth mobility increased in some extent. Enlargement of periodontal ligament space and loss of lamina dura in 40% of abutment teeth were observed for 5 years. There were six decayed teeth, six teeth, from which a intracoronal crown was removed, and two extracted teeth in 47 abutment teeth. In conclusion, the periodontal tissues around abutment teeth in Konus telescope denture changed slightly at one year after denture placement, after which, the periodontal tissues were well maintained.

[Buccal and lingual crown contours. The influences of the self-cleansing effect of food and mechanical cleansing].

I studied the difference of coronal bucco-lingual contours influenced self-cleansing effect by food and easiness in mecanical cleansing, using the teeth coloring matter, and got the following conclusion.About self-cleansing effect by food.1. From the bucco-lingual side point of view, the rate of removing the coloring matter was higher in functional cusp side than in non-functional cusp side.2. From the form variety point of view, in functional cusp side, according to high of contour decreasing, the rate of removing the coloring matter was higher. On the other hand, in non-functional cusp side, the evident defference was not observed. And the coloring matter remained at the cervical part in every form.3. Form the food variety point of view, the evident difference was observed; the rate of removing the coloring matter was highest in boiled pork, next raw cucumber, and was lower in kamaboko and bread.About easiness in mechanical cleasing. From the form variety point of view, according to height of contour increasing, the rate of remaining the coloring matter was higher.