Effect of implant abutment screw materials and tightening protocols on reverse tightening values: An in vitro study

Abdullah H Alnasser; Chandur P K Wadhwani; Esra Y Alsarraf; Mathew T Kattadiyil; Jaime Lozada

doi:10.1016/j.prosdent.2023.05.018

Effect of implant abutment screw materials and tightening protocols on reverse tightening values: An in vitro study

J Prosthet Dent. 2023 Jul 8:S0022-3913(23)00368-2. doi: 10.1016/j.prosdent.2023.05.018. Online ahead of print.

Authors

Abdullah H Alnasser¹, Chandur P K Wadhwani², Esra Y Alsarraf³, Mathew T Kattadiyil⁴, Jaime Lozada⁵

Affiliations

¹ Fellow, Advanced Digital Prosthodontics and Implant Dentistry Program, Loma Linda University, Loma Linda, Calif; Teaching Assistant, Department of Prosthodontics, School of Dentistry, Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia. Electronic address: aalnasser00@gmail.com.
² Adjunct Assistant Professor, Advanced Education Program in Prosthodontics, Loma Linda University, Loma Linda, Calif.
³ Fellow, Advanced Digital Prosthodontics and Implant Dentistry Program, Loma Linda University, Loma Linda, Calif; Teaching assistant, Faculty of Dentistry, Kuwait University, Kuwait City, Kuwait.
⁴ Professor and Director, Advanced Education Program in Prosthodontics, Loma Linda University, Loma Linda, Calif.
⁵ Professor and Director, Advanced Education Program in Implant Dentistry, Loma Linda University, Loma Linda, Calif.

PMID: 37429754
DOI: 10.1016/j.prosdent.2023.05.018

Abstract

STATEMENT OF PROBLEM: Implant abutment screw loosening is the most common prosthetic complication of implant-supported single crowns. However, few studies have objectively evaluated the effectiveness of different tightening protocols on reverse tightening values (RTVs).

Purpose: The purpose of this in vitro study was to determine the optimal tightening protocol for implant abutment screws with different screw materials.

Material and methods: Sixty implants from 2 implant systems (Keystone and Nobel Biocare) with different definitive screw materials were selected. One group used diamond-like carbon (DLC) coated screws (DLC Group), and the other used titanium nitride (TiN) screws (TiN Group). Each group consisted of 30 implants. The implants in each group were distributed randomly into 3 subgroups (n=10). The implants from both manufacturers were mounted in resin blocks by following a clinical component connection protocol: a cover screw was placed, then an impression coping, and finally an original manufacturer prefabricated abutment. The abutment screws were tightened to the manufacturer's recommended tightening value using 3 different protocols: tighten the screw once (1T); tighten the abutment screw to the recommended tightening value, wait 10 minutes, and then retighten (2T); and tighten the abutment screw to the recommended tightening value, countertighten, tighten, countertighten, and then tighten (3TC). RTVs were measured after 3 hours. The Shapiro-Wilk test was performed to test for normal distribution of the data. The Kruskal-Wallis test was applied to each system's group that was not normally distributed (P<.05). Where differences existed, a post hoc analysis using the Dwass-Steel-Critchlow-Flinger (DSCF) pairwise comparisons test was conducted.

Results: No significant differences were found among the 3 different tightening groups in the TiN group (P>.05). However, significant differences were found among the 3 different tightening protocols in the DLC group (P<.05).

Conclusions: Abutment screw systems from different manufacturers behave differently with respect to how they are tightened. For the TiN screw group, statistically similar RTVs were found for the 3 tightening protocols. The most efficient tightening protocol for the DLC-coated screw was the 3TC-DLC.