PURPOSE: This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. MATERIALS AND METHODS: Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (alpha=0.05). RESULTS: The postload removal torque value was high in the following order with regard to magnitude: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). CONCLUSION: The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate.
Joints* ; Torque

PURPOSE: Autoclaves and UV sterilizers have been commonly used to prevent cross-infections between dental patients and dental instruments or materials contaminated by saliva and blood. To develop a dental sterilizer which can sterilize most materials, such as metals, rubbers, and plastics, the sterilization effect of an atmospheric pressure non-thermal air plasma device was evaluated. MATERIALS AND METHODS: After inoculating E. coli and B. subtilis the diamond burs and polyvinyl siloxane materials were sterilized by exposing them to the plasma for different lengths of time (30, 60, 90, 120, 180 and, 240 seconds). The diamond burs and polyvinyl siloxane materials were immersed in PBS solutions, cultured on agar plates and quantified by counting the colony forming units. The data were analyzed using one-way ANOVA and significance was assessed by the LSD post hoc test (alpha=0.05). RESULTS: The device was effective in killing E. coli contained in the plasma device compared with the UV sterilizer. The atmospheric pressure non-thermal air plasma device contributed greatly to the sterilization of diamond burs and polyvinyl siloxane materials inoculated with E. coli and B. subtilis. Diamond burs and polyvinyl siloxane materials inoculated with E. coli was effective after 60 and 90 seconds. The diamond burs and polyvinyl siloxane materials inoculated with B. subtilis was effective after 120 and 180 seconds. CONCLUSION: The atmospheric pressure non-thermal air plasma device was effective in killing both E. coli and B. subtilis, and was more effective in killing E. coli than the UV sterilizer.
Agar ; Atmospheric Pressure ; Bacteria ; Cross Infection ; Dental Instruments ; Diamond ; Homicide ; Humans ; Lysergic Acid Diethylamide ; Metals ; Plasma ; Plasma Gases ; Plastics ; Polyvinyls ; Rubber ; Saliva ; Siloxanes ; Stem Cells ; Sterilization

PURPOSE: The purpose of this study was to analyze the effect of denture cleansers on Candida albicans biofilm formation over resilient liners and to evaluate compatibility between resilient liners and denture cleansers. MATERIALS AND METHODS: Acrylic resin (Lucitone 199(R)) and 3 resilient liners (COE-SOFT(TM), GC RELINE(TM) and SOFRELINER TOUGH TOUGH(R)) were incubated in denture cleansers (Polident(R) and Cleadent(R)) for 8 hours a day and in unstimulated saliva for 16 hours a day (n=25/gp) for 60 days. Two-way and three-way repeated measures ANOVA were performed to compare the surface roughness (Ra), pH and C. albicans binding level by radioisotope (alpha=0.05). The statistical significance of the relation between Ra and adhesion was evaluated by correlation analysis. RESULTS: The degree of Ra was significantly decreased in the following order: COE-SOFT(TM), acrylic resin, GC RELINE(TM) and SOFRELINER TOUGH(R). The immersion in denture cleansers significantly increased Ra of resilient liners, except for SOFRELINER TOUGH(R) in Cleadent(R). No significant differences in pH curves were observed among groups immersed in distilled water and denture cleansers. The binding levels of C. albicans were significantly decreased in the following order: COE-SOFT(TM), GC RELINE(TM), SOFRELINER TOUGH(R), and acrylic resin. The immersion in Cleadent(R) seemed to decrease C. albicans binding level on GC RELINE(TM) and SOFRELINER TOUGH(R). CONCLUSION: Based on the C. albicans binding levels results, it is not recommended to immerse COE-SOFT(TM) in denture cleansers, and GC RELINE(TM) and SOFRELINER TOUGH(R) should be immersed in Cleadent(R).
Biofilms* ; Candida albicans* ; Denture Cleansers* ; Hydrogen-Ion Concentration ; Immersion ; Saliva ; Water