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Effect of Cyclic Loading on Screw Joint Stability of Implants with Angled Screw Channel Crowns

Mulla, Salah
http://rave.ohiolink.edu/etdc/view?acc_num=osu1593090425010651

Abstract Details

2020, Master of Science, Ohio State University, Dentistry.
Statement of problem. With the introduction of the angled screw channel concept in 2004 by a manufacturer (Dynamic Abutment; Talladium International Implantology) followed by the emergence of similar solutions from several other manufacturers in the succeeding years, it has become possible to restore axially-inclined implants with screw-retained crowns without the need for an intermediary angle-correcting abutment. Research is lacking as to how the non-axially tightened implant crowns perform under mechanical cyclic loading and as to how their Reverse Torque Values compare with axially tightened cement-retained crowns restored on angle-correcting abutments. Purpose. The purposes of this study were to evaluate the ability of different 25° angled screw channel hexalobular systems to apply the target torque value on their screws, the effect of cyclic loading on their Reverse Torque Values, and their survival compared to crowns cemented on conventional 0° screw channel angled abutments. Materials and Methods. The ISO 14801:2007 fatigue test for endosseous dental implants requirements were taken into consideration when designing the study. A total of 28 implants (Nobel Replace Conical Connection) were divided into four different groups: DY (Dynamic Tibase®, Dynamic Abutment Solutions), DE (AngleBase®, Dess Dental Smart Solutions), ASC (Angulated Screw Channel Solutions, Nobel BioCare) and UB (Universal Base, Nobel BioCare) (n=7). Using each manufacturer’s specific angulated Ti-base solution, twenty-one angulated screw channel crowns were fabricated at 25° angle correction for groups ASC, DY and DE. The fourth group (UB) served as control consisting of seven cement-retained crowns with 25° custom-milled angled zirconia abutments that were cemented onto their respective Universal Bases. With the aid of CAD-CAM technology, the digital design of the angulated screw channel crown was generated from a scanned analogue model (Kilgore D95SDP-200-GSF). Crowns from all groups and abutments from the UB (control group) were milled from 3Y-TZP zirconia. An autopolymerizing composite resin cement (Ivoclar vivadent Multilink® Hybrid abutment) was used to cement the crowns and abutments onto their respective Ti-bases. An autopolymerizing composite resin cement (RelyX Unicem 2; 3M) was used to cement the UB crowns onto their respective custom-milled abutments. A special pressure device was used to standardize the cementation pressure applied at 24 N. All implants were then cemented into G10 fiberglass blocks using a chemical set composite resin (Rock Core; Zest dental solutions) to mimic osseointegration. Using a torque limiting device (Nobel BioCare), all crowns were torqued to manufacturers’ recommended torque values: 35 Ncm for groups ASC, UB, DE, and 25 Ncm for DY. Initial Torque Values (ITV1) were recorded. A 24-hour settling time was allowed, following which the screws’ Reverse Torque Values (24hr-RTV1) were measured using a digital torque device (Chatillon Model DFS2-R-ND). A new set of screws was then delivered to each group at the same recommended torque values and the Initial Torque Values (ITV2) were recorded. Then, the specimens were subjected to mechanical cyclic loading at room temperature at 2 Hz for 5 million cycles and under a load of 200 N simulating 5 years of functional loading. Reverse Torque Values (RTV2) were then recorded for the surviving implants using a digital torque device. ANOVA statistical analysis was used to compare differences in the means of deviation of Initial Torque Values from the target torque, and in the means of Reverse Torque Values among groups, followed by a Tukey-Kramer post hoc analysis to determine what specific means were significantly different from each other. Preload efficiency of each system was calculated by comparing the resulting torque values following loading to those recommended by the manufacturer (RTV2/ ITV2). A Kaplan–Meier survival analysis was performed to determine if there was a statistically significant difference in the survival rates among the groups. Results. ANOVA type III tests showed a statistically significant difference in the means of deviation of Initial Torque Values (ITV1 & ITV2) from target torque value of the groups with 25° torque application (DY, DE, and ASC) when compared to the means of deviation of Initial Torque Values of the control group (UB) with 0° torque application. The pairwise comparison analysis to the control group (UB) showed a statistically significant difference in two groups (ASC & DE) (P<.0001 & P=.0033 for ASC ITV1 & ITV2, P<.0001 & P=.0059 for DE ITV1 & ITV2). A statistically significant difference in the mean Reverse Torque Values was found after the 24-hour settling period (24hr-RTV1) and following cyclic loading (RTV2) among groups (P<.0001). Furthermore, the Tukey-Kramer test showed a statistically significant difference in the DY group compared with other groups (P<.0001) over the sequences studied. The test also showed a statistically significant difference in mean Reverse Torque Values before and after cyclic loading (24hr-RTV1 and RTV2) over all groups studied (P<.0001). Calculations of the preload efficiency yielded 43.78% for DY, 46.83% for DE, 54.16% for ASC, 48.46% for UB. During cyclic loading, 3 specimens from ASC, 1 specimen from DY and 1 specimen from DE sustained catastrophic fractures and were not usable in reversal torque measurements. Kaplan–Meier analysis showed no statistically significant difference in the survival rates among groups. Conclusion. At 25° the hexalobular system of DY was able to deliver Initial Torque Values that were not significantly deviated from manufacturer’s target value when compared to the deviation in Initial Torque Values delivered by the control group (UB) at 0°. The hexalobular systems (25°) of ASC and DE had significant deviations in their Initial Torque Values from manufacturers’ target values when compared to the deviation in Initial Torque Values delivered by control group (UB) (0°). The DY group with a 25° angled screw channel which had lower manufacturer’s recommended torque value scored lower Reverse Torque Values compared to other groups after 24 hours and after cyclic loading. Two groups with 25° angled screw channel correction (DE, ASC) had comparable Reverse Torque Values between each other, and compared to 0° control group (UB) after 24 hours and after cyclic loading.
Burak Yilmaz, DDS, PhD (Advisor)
Robert Seghi, DDS, MS (Committee Member)
William Johnston, MS, PhD (Committee Member)
75 p.
Dentistry
angled screw channel; cyclic loading; non-axial tightening; reverse torque values; initial torque values; angulated screw channel; implant crowns; hexalobular; angulation correction; salah mulla

Recommended Citations

Citations

  • Mulla, S. (2020). Effect of Cyclic Loading on Screw Joint Stability of Implants with Angled Screw Channel Crowns [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1593090425010651

    APA Style (7th edition)

  • Mulla, Salah. Effect of Cyclic Loading on Screw Joint Stability of Implants with Angled Screw Channel Crowns. 2020. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1593090425010651.

    MLA Style (8th edition)

  • Mulla, Salah. "Effect of Cyclic Loading on Screw Joint Stability of Implants with Angled Screw Channel Crowns." Master's thesis, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1593090425010651

    Chicago Manual of Style (17th edition)

osu1593090425010651
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