Influence of atmospheric pressure low-temperature plasma treatment on the shear bond strength between zirconia and resin cement.

PURPOSE: Zirconia exhibits excellent strength and high biocompatibility in technological applications and it is has therefore been investigated for clinical applications and research. Before setting prostheses, a crown prosthesis inner surface is sandblasted with alumina to remove contaminants and form small cavities. This alumina sandblasting causes stress-induced phase transition of zirconia. Atmospheric-pressure low-temperature plasma has been applied in the dental industry, particularly for adhesives, as a surface treatment to activate the surface energy and remove contaminants. The purpose of this study was to examine the influence of atmospheric-pressure low-temperature plasma treatment on the shear bond strength between zirconia and adhesive resin cement. METHODS: The surface treatment method was classified into three groups: untreated (Cont group), alumina sandblast treatment (Sb group), and atmospheric-pressure low-temperature plasma treatment (Ps group). Adhesive resin cement was applied to stainless steel and bonded to zirconia. Shear adhesion tests were performed after complete hardening of the cement. Multiple comparisons were performed using a one-way analysis of variance and the Bonferroni method. X-ray diffractometry was used to examine the change in zirconia crystal structure. RESULTS: Statistically significant differences were noted between the control and Sb groups and between the control and Ps groups. In contrast, no statistically significant differences were noted for the Ps and Sb bond strength. Atmospheric-pressure low-temperature plasma treatment did not affect the zirconia crystal structure. CONCLUSIONS: Atmospheric-pressure low-temperature plasma treatment improves the bonding strength of adhesive resin cement as effectively as alumina sandblasting, and does not alter the zirconia crystal structure.

[Comparison of shortened dental arches with complete dental arches by clinical examinations].

PURPOSE: Recently, there have been reports in favor of avoiding prosthodontic intervention as Shortened Dental Arch (SDA) in Northern Europe. However, many of these reports were conducted through interviews and questionnaires, and so the evaluation of the results lacked objectivity. Thus, this research analyzed the clinical status of SDA. METHODS: For the selection of subjects, seven patients (average age: 59.3+/-13.2 years old) who had had the free-end missing on both sides of the lower dental arches for over five years were chosen as the SDA group. As the complete dental arch (CDA) group, seven patients (average age: 61.3+/-9.6 years old) who had no clinical defects in their masticatory function, and who had no missing teeth other than the third molar, were selected. Measurement items in this study were occlusal contact areas for the mandible premolar, center of force, occlusion time, and interdentium. The Mann-Whitney U test was used for statistical analysis and the significance level was assumed to be 5%. RESULTS: The results were as follows: 1) The occlusal contact area of the mandible premolar of SDA was significantly large. 2) The center of force of SDA was significantly forward. 3) The occlusion time of SDA had a tendency of prolongation. 4) Interdentium of 3 2 | 2 3, 4 3 | 3 4 and 5 4 | 4 5 of SDA were significantly wide. CONCLUSIONS: There were differences of clinical parameters between SDA and CDA in this study.