Browsing by Subject "Implants"

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    Comparison of the Dimensional Stability of Splinting Material with Different Polymerization Times
    (2016-05) Kiangsoontra, Jason
    Purpose: The purpose of this study was to evaluate the effects of polymerization time and sectioning on the dimensional changes of auto-polymerizing acrylic resin used in splinting impression copings and the resulting fit of the prosthesis. Materials and Methods: Open-tray impression copings were connected to a master cast containing 5 external-hex implants. Auto-polymerizing acrylic resin was allowed to polymerize in a heavy-body polyvinyl siloxane matrix according to 3 different time groups (8 minutes (8MN), 1 hour (1HR), and 24 hours (24HR)), with 20 sets of splinted impression copings per time group. Each time group was further divided into non- sectioned (NS) and sectioned (S) groups (10 samples per group). A total of 60 gypsum bases were fabricated from implant analogs connected to the impression copings. A milled titanium bar fabricated from the master cast was used to verify the fit of the bar to the implant analogs. The casts were viewed using loupes (2.5x magnification) and a microscope (12.8x magnification) to visually detect any gap. The gap sizes were evaluated with a measuring gauge with pre-determined thickness in microns (μm). Results: Of the 30 casts tested in the sectioned groups (8MN-S, 1HR-S, and 24HR-S), all of the casts displayed clinical fit when evaluated with magnification loupes and a dental explorer. From this evaluation, only the 8MN-S group showed statistical significant difference (p < 0.05) when compared to its non-sectioned counterpart (8MN- NS). When evaluated with a microscope, no significant differences were found between the different time groups or sectioned samples. The microscope was able to detect gaps that were not detectable with magnification loupes and a dental explorer. Conclusion: Overall, difference in polymerization time and sectioning did not have an effect on the accuracy of fit. Sectioning for the 8-minute time group did show an improvement in the fit when compared to the non-sectioned samples. Although clinical fit appeared to be present, it did not always indicate the presence of absolute fit.
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    Risk factors associated with implant failure
    (2013-04) Schmalz, Emily Marie
    Objective and Background: Implants have become a predictable treatment for the replacement of missing teeth. However, they are not without problems. It is important to understand the relationship between implant failure and patient- and implant-level factors. Therefore, the purpose of this retrospective chart review was to explore patient- and implant-level factors associated with implant failure, defined here as the loss, removal, or scheduled removal of the implant. Methods: Data were abstracted from charts of patients at the University of Minnesota School of Dentistry. Patient-level variables included current smoking status, gender, age, self-reported diabetes, and history of bisphosphonate use. Implant-level variables included implant brand, location, whether sinus or bone augmentation was done, immediate or delayed implant placement and restoration type. Data were entered into a custom, web-based data file. Implant failure was defined as the loss or planned removal of the fixture. Descriptive statistics were computed for patient- and implant-level variables. Hazard ratios (HR) and p-values were calculated using Cox proportional hazards regression. The relationship between the variables and implant failures were explored in both univariable and multivariable analyses. We analyzed data for all implants and separately for implants placed in the posterior maxilla. Results: Smoking was the only patient-level variable associated with implant failure in the univariable analyses (P=0.0109, HR=2.13). Sinus grafting material significantly affected implant failure in both univariable and multivariable analyses (P=<0.0001). Implant-level variables such as length, jaw region, alveolar ridge grafting, and sinus grafting both prior to and at the time of implant placement were not significantly associated with failures (P=>0.05) in the univariable analysis. In the multivariable analysis, overdentures had a failure rate 2.95 times greater than single crowns. In addition, sinus grafting material (P=<0.0001) and bone grafting material (P=0.006) were also significant in the multivariable analysis for all sites. When limiting the multivariable analysis to posterior maxillary sites only bone grafting material was no longer significant, while both restoration type and sinus grafting material remained statistically significant. Interestingly, timing of ridge augmentation, either prior to or at the time of implant placement did not affect implant failure (HR=0.97). Conclusions: Overall, implants are a predictable treatment option. Smoking negatively affects implant success. Implants supporting overdentures have higher failure rates when compared to those supporting single or multiple fixed restorations and fixed-detachable appliances. Self-reported diabetes, use of bisphosphonates and timing of ridge augmentation were not associated with implant failure.