Abstract
The aim of this study was to assess the effect of application of a recently developed bio-adhesive (Impladhesive) to abutment screw threads on the removal torque value and rotational misfit at the implant–abutment junction. This in vitro study evaluated 20 implant fixtures and 20 straight abutments. Specimens were randomly divided into two groups (n = 10) with/without adhesive application. In the adhesive group, the abutment was dipped in Impladhesive before torquing. In the control group, the abutment was torqued conventionally without adhesive application. The removal torque value was recorded after completion of the cyclic loading of 500,000 cycles with 2 Hz frequency and 75 N load. Rotational misfit was recorded using a video measuring machine. After applying the torque, the change in the bisector angle on the abutment hex was recorded for each implant. The biocompatibility of Impladhesive was evaluated using a MTT cell vitality assay. Normal distribution of data was assessed using the Kolmogorov–Smirnov test. Data were analyzed using a t-test and Pearson’s correlation coefficient The application of Impladhesive at the implant–abutment interface resulted in significantly greater mean removal torque value compared to the control group (p = 0.008). In addition, the mean rotational misfit at the implant–abutment interface was significantly lower in the use of Impladhesive compared to the control group (p = 0.001). In addition, the cell vitality was found to be greater than 80% at all evaluated time points. It can be concluded that the application of Impladhesive on the abutment screw significantly decreased rotational misfit and increased the removal torque value. Future studies are needed to evaluate the efficacy of this bio-adhesive an in vivo setting.
Highlights
Replacement of the missing teeth by implant-supported restorations is a predictable treatment modality [1,2]
Several variables can affect the magnitude of this load, such as the torque applied for abutment tightening, type and design of the implant–abutment junction, screw design, screw material properties, microstructure and microscopic irregularities of the implant–abutment interface, the magnitude of applied load, presence of lubricants, and contamination with saliva and oral debris [10]
The removal torque values and rotational misfit values for test and control groups are presented in the Table 1
Summary
Replacement of the missing teeth by implant-supported restorations is a predictable treatment modality [1,2]. Any deformation or wear of prosthetic restoration due to misfit can compromise the long-term stability of this junction and lead to technical complications, such as abutment screw loosening [5]. Preload is a tensile load that is generated when tightening the abutment screw into the implant fixture and is required to maintain the assembly of the components [7]. The removal torque value is the magnitude of rotational force required for the retrieval of the abutment screw from the implant fixture. The removal torque value and the preload would decrease following the occurrence of microleakage as a result of misfit between different implant components [13]. Our group has previously showed that the application of an industrial adhesive material around the screw of the abutments can significantly increase the removal torque value and reduce screw loosening [17]. Engineering a biocompatible adhesive can be a viable option to reduce the chance of the screw loosening
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