Shear Bond Strength between Orthodontic Brackets and Monolithic 4Y-TZP: An In Vitro Study.

The aim of this study was to evaluate the effect of different surface treatments on the shear bond strength (SBS) between metal orthodontic brackets and monolithic zirconia surfaces bonded with resin composite. Fifty monolithic zirconia (4Y-TZP) disks were sintered and glazed. Specimens were divided into five groups (n = 10) for different surface treatments: control, nano second fiber laser, sandblasting, grinding and tribochemical coating (CoJet Sand 30-µm). Metal orthodontic brackets were bonded to monolithic zirconia surface by two-component orthodontic adhesive. After 500 cycles of thermocycling, shear bond strength values were measured by a universal testing machine at a cross head speed of 0.5 mm/min. The data was recorded as MPa and statistically analyzed with One-way ANOVA, Levene's LSD tests with Bonferroni corrections. The significance level was α = 0.05. The surface topography of one specimen of each group was evaluated by scanning electron microscopy (SEM). Statistically significant difference was observed among study groups (p = 0.018). The lowest shear bond strength was observed in the control group (3.92 ± 1.9). Tribochemical coating showed the highest bond strength (7.44 ± 2.9), which was statistically different from the control and nano second laser (4.3 ± 1.4) groups but not statistically different from grinding (6.15 ± 3.1) or sandblasting (6.47 ± 3.3). SEM images showed comprehensive results of each surface treatment on monolithic zirconia. All failure modes were recorded as adhesive between the composite resin and monolithic zirconia. Based on the findings of this study, it can be concluded that grinding, sandblasting and tribochemical coating techniques showed clinically acceptable bond strength within the range of 6-8 MPa. These surface treatments can be considered suitable for achieving a durable bond between metal orthodontic brackets and monolithic 4Y-TZP ceramic surfaces.

Effects of smoking on the bone alkaline phosphatase in peri-implant crevicular fluid and implant stability quotient around implants before loading.

We aimed to examine the implant stability quotient (ISQ), alveolar bone level measurements (ABL), and bone alkaline phosphatase (BALP) in peri-implant crevicular fluid (PICF) around implants in smokers and non-smokers before loading in 3 months. 44 dental implants were placed into smoker and non-smoker patients equally. ISQ was measured at baseline and 3 months after surgery. The levels of PICF BALP and alveolar bone were measured. ISQ values significantly increased in smokers and non-smokers in the 3rd month (p < 0.05). ABL measurements were lower at 3 months compared to baseline in both groups (p < 0.05). Although ISQ and ABL values were higher in non-smokers than smokers at 3 months, the difference between the groups did not show any statistical significance. The PICF BALP levels in the 3rd month changed in both groups. But, these differences were insignificant. Although some of the measurements presented differences between the groups during the assessment periods, they were not indicative of the hazardous effects of smoking on bone healing around implants after surgery till functional loading in 3 months. However, smoking is an important factor to be considered for osseo-integration outcomes. Further studies are needed to clarify the influence of smoking on osseo-integration.

Bacterial adhesion and colonization differences between zirconium oxide and titanium alloys: an in vivo human study.

PURPOSE: The purpose of this study was to compare zirconium oxide and titanium alloys with respect to their tendency to adhesion and colonization of two periodontal pathogens on both hard surfaces and on soft tissues in vivo. MATERIALS AND METHODS: The present study was designed as a prospective stratified randomized controlled clinical trial. Patients were scheduled to receive two implants with different types of abutments in the posterior mandible. Three months after implant placement, titanium and zirconium abutments were connected. Five weeks after abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsy samples were obtained. Abutments and biopsy specimens were analyzed by reverse-transcriptase polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated by sesile water drop before replacement. RESULTS: No statistically significant differences were found between probing depths or DNA copy numbers of A actinomycetemcomitans, P gingivalis, and total bacteria both for both titanium alloys and zirconium oxide surfaces and the biops specimens obtained from their buccal gingival. With respect to the surface free energy of zirconium and titanium abutments, zirconium abutments showed lower surface free energy than titanium abutments. CONCLUSION: The results of this study showed that zirconium oxide surfaces have comparable properties to titanium alloy surfaces in their tendency to adhesion and colonization of two periodontal pathogens on both hard surfaces and in soft tissues.