Bone-level conical dental implants: evaluation of the predisposing factors responsible for the marginal bone loss

The aim of this study is to identify the factors that influence the MBL. The presence of peri-implant bone is of primary importance for the success of dental implants over time. The majority of peri-implant bone loss occurs between the connection of the abutment and the position of the crown, Since success criteria, a significant decrease in implant-dependent MBL has been proposed. A retrospective analytical study was conducted on a sample of 1532 patients treated between 2008 and 2019 at the Dentistry University of Granada. Data were collected for each patient such as: gender, type of edentulism, in relation to the kennedy classes, implant site, diameter and height of the same, date of each radiographic survey carried out during the follow-up, recorded at 5 years. Marginal peri-implant bone reabsorption was assessed by measuring changes at the mesial and distal levels at the time of positioning of the implant, after 1,2,3,4 and 5 years, passing through the positioning of the crown. A linear regression econometric model was used to test the significance of each variable. The F test and the confidence interval were used and in case of discrepancy, between two tests, in the estimation of variables significance the confidance interval was preferred. The most significant confidence interval is found for higher abutments (0,023). The height of the prosthetic abutment was the variable with the greatest influence on the MBL, greater around the implants with shorter abutments. Current results, show that MBL levels are scarcely relevant from the surgical positioning of the implant (T0) to T1 compared to those between T2 and T3 and become more significant in the T3-T4 period. The results indicated that are more likely to occur higher T5 rates in implants with high rates between T1 and T2. Almost all implants (96.1%) with MBL> 2 mm at 5 years shown a high rate of bone loss at T2 (defined as> 0.502 mm at 6 months). These results describe that the marginal loss immediately after the restoration can indicate a clear danger for the MBL of the implants and reach a failure in the medium or long term.