Purpose This in-vitro study was designed from a clinical case and investigated how mechanical and chemical modifications on implant abutment surfaces would result in different tensile strengths between computer-aided design/computer-aided manufactured lithium disilicate crowns and implant abutments cemented with polycarboxylate cement. Material & Methods A master cast of a maxillary right central incisor single implant restoration from a clinical case was utilized to fabricate five samples of each of five unique abutment types: titanium smooth surface (Ts), titanium with retentive grooves (Tr), titanium smooth surface with titanium nitride coating (Gs), titanium with retentive grooves and titanium nitride coating (Gr), and zirconia (Z). A total of 25 lithium disilicate crowns were fabricated and randomly paired with a test abutment. Each crown was cemented to its respective implant abutment with polycarboxylate cement. After a week of polymerization, the maximum tensile strength of each abutment-crown assembly was measured using a universal testing machine until the interface failed. Results In order of greatest retention to least retention were titanium smooth surface (Ts), titanium with retentive grooves (Tr), titanium smooth surface with titanium nitride coating (Gs), zirconia (Z), and titanium with retentive grooves and titanium nitride coating (Gr). Retentive grooves did not affect the retention of the restoration (P=.218) and neither did the titanium nitride coating (P=.108); however, Kruskal-Wallis test found a significant decrease in retentiveness of the titanium abutment group with both retentive grooves and a titanium nitride coating compared to all other groups (P<.05). A significant difference was also found in the retentiveness of Ts compared to Z (P<.05). No other statistically significant differences in regards to retentiveness were found between groups. Conclusion Retentive grooves on titanium abutments and titanium nitride coating on titanium abutments do not significantly affect the retention of the restoration; however, when retentive grooves and titanium nitride coatings are used together on an abutment, there is a synergistic effect that decreased the retention of lithium disilicate crowns cemented with polycarboxylate cement. The results of this study may help clinicians make educated decisions when evaluating the use of polycarboxylate cement with lithium disilicate crowns on implant-supported abutments.
University of Minnesota M.S. thesis. June 2018. Major: Dentistry. Advisor: Heather Conrad. 1 computer file (PDF); vii, 43 pages.
The comparison of tensile strength of polycarboxylate cement among different surfaces of implant custom abutments.
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