Objective: To identify the influence of prosthetic features through a comprehensive analysis with other known risk factors. Materials and methods:A total of 169 patients (n = implants: 349) was retrospectively included in the present study. Peri-implantitis was diagnosed based on periimplant bone loss and probing depth. Using radiographs taken 1 and 5 years following prosthesis insertion, the following features were determined: peri-implant marginal bone loss (MBL), emergence angle (EA), emergence profile (EP) and crown/implant ratio (CIR). The splinted position of prosthesis was also recorded. Multivariable generalized estimating equation was used to analyse the influence of each feature on the prevalence of peri-implantitis. The final prediction model was constructed by Cox proportional hazard regression analysis. Results:The EA showed a significant correlation with MBL. A statistically greater prevalence of peri-implantitis was observed if EA ≥ 30 degrees, when EP is convex and in middle implant splinted with both mesial and distal adjacent implants in bonelevel implant. A similar correlation was not observed in tissue-level implants. CIR had no significant effect on the prevalence of peri-implantitis. Conclusion:Over-contoured implant prosthesis is a critical local confounder for peri-implantitis. The implant splinted to both mesial and distal adjacent implant has a higher risk of peri-implantitis. K E Y W O R D Semergence angle, emergence profile, Peri-implantitis, restoration contour, splinted

PURPOSEThe aim of this study was to compare the fracture of implant component behavior of external and internal type of implants to suggest directions for successful implant treatment.MATERIALS AND METHODSData were collected from the clinical records of all patients who received WARANTEC implants at Seoul National University Dental Hospital from February 2002 to January 2014 for 12 years. Total number of implants was 1,289 and an average of 3.2 implants was installed per patient. Information about abutment connection type, implant locations, platform sizes was collected with presence of implant component fractures and their managements. SPSS statistics software (version 24.0, IBM) was used for the statistical analysis.RESULTSOverall fracture was significantly more frequent in internal type. The most frequently fractured component was abutment in internal type implants, and screw fracture occurred most frequently in external type. Analyzing by fractured components, screw fracture was the most frequent in the maxillary anterior region and the most abutment fracture occurred in the maxillary posterior region and screw fractures occurred more frequently in NP (narrow platform) and abutment fractures occurred more frequently in RP (regular platform).CONCLUSIONIn external type, screw fracture occurred most frequently, especially in the maxillary anterior region, and in internal type, abutment fracture occurred frequently in the posterior region. placement of an external type implant rather than an internal type is recommended for the posterior region where abutment fractures frequently occur.

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PURPOSEThe purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading.MATERIALS AND METHODSThe study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (106 cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces.RESULTSThere was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant.CONCLUSIONThe use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

PURPOSE To compare the clinical outcomes of two types of implant restoration for posterior edentulous area, 3-unit bridge supported by 2 implants and 3 implant-supported splinted crowns. MATERIALS AND METHODS The data included 127 implant-supported fixed restorations in 85 patients: 37 restorations of 3-unit bridge supported by 2 implants (2-IB), 37 restorations of 3 implant-supported splinted crowns (3-IC), and 53 single restorations (S) as controls. Peri-implantitis and mechanical complications that occurred for 14 years were analyzed by multivariable Cox regression model. Kaplan-Meier curves and the multivariable Cox regression model were used to analyze the success and survival of implants. RESULTS Peri-implantitis occurred in 28.4% of 2-IB group, 37.8% of 3-IC group, and 28.3% of S control group with no significant difference. According to the implant position, middle implants (P2) of the 3-IC group had the highest risk of peri-implantitis. The 3-IC group showed a lower mechanical complication rate (7.2%) than the 2-IB (16.2%) and S control group (20.8%). The cumulative success rate was 52.8% in S (control) group, 62.2% in 2-IB group, and 60.4% in 3-IC group. The cumulative survival rate was 98.1% in S (control) group, 98.6% in 2-IB group, and 95.5% in 3-IC group. There was no significant difference in the success and survival rate according to the restoration type. CONCLUSION The restoration type was not associated with the success and survival of implants. The risk of mechanical complications was reduced in 3 implant-supported splinted crowns. However, the middle implants of the 3 implant-supported splinted crowns had a higher risk of peri-implantitis.