Estudio clínico de las complicaciones biológicas y mecánicas en prótesis unitarias con o sin pilar intermedio

Abstract

Introduction: Dental implants are an attractive option for restoring missing teeth, offering a predictable solution without the need to modify adjacent teeth. However, complications such as marginal bone loss, screw loosening, and material fractures have been reported. Despite advancements in implant technology and techniques, there is ongoing debate about the ideal design of implant-supported restorations and its impact on long-term outcomes. This study aims to explore these factors further, particularly the mechanical and biological implications of different restorative approaches in implant-supported single crowns. Materials and Methods: To achieve the study objectives, two approaches were employed: a pilot study using finite element analysis (FEÁ) and a randomized clinical trial. The pilot study aimed to evaluate the fatigue behaviour of single-implant restorations by comparing the use of a transepithelial component versus a direct implant-supported restoration. The randomized clinical trial investigated biological and mechanical complications in single-implant restorations, comparing the outcomes with and without the use of a transepithelial component. Pilot Study: Á 4.5 mm diameter and 13 mm length IIPSCÁ4513 Interna Plus implant (BTI® Biotechnology Institute, Min ano, Spain) was selected. Two implants were placed in juxtacrestal cortical bone, with the implant-abutment interface level with the bone. In one case, an INPPTU44 abutment was mounted and fixed with an INTTUH screw tightened to 35 Ncm. In the other case, a transepithelial INTMIPU20 abutment was mounted and tightened to 35 Ncm, with a CPMIUPU abutment attached using a prosthetic screw tightened to 20 Ncm. Finite element analysis was performed using Ánsys Workbench® 19R1, simulating a cyclic masticatory force inclined at 30° to the vertical, following ISO 14801 standards. Clinical Study: This randomized clinical trial analyzed biological and mechanical complications in single-implant restorations. The study included adults (>18 years) with one or more osseointegrated single implants. The implants were randomly assigned to one of three groups: (Á) restorations with a UNIT intermediate abutment and CÁD/CÁM structure, (B) direct implant-supported CÁD/CÁM restorations, or (C) direct implant-supported cast restorations. Á total of 60 BTI Core IIPECÁ implants were placed in 18 patients. The main variable analyzed was marginal bone loss at 3 and 6 months, measured using standardized radiographic techniques. Secondary variables included implant and restoration survival, as well as common prosthetic complications like screw loosening or chipping/fracture of the porcelain. Statistical analyses were performed using Rstudio (Version 2023.12.1+402). Descriptive statistics were used for categorical and quantitative variables. Normality tests (Kolmogorov-Smirnov, Q-Q plots, skewness, and kurtosis) were conducted. Inferential analyses were performed using Chi-square tests for categorical variables and Kruskal-Wallis tests for non-normally distributed numerical variables, with post-hoc Dunn tests where applicable. The study was approved by the Ethics Committee of the University of Leo n (ETICÁ-ULE-002-2020). Áll participants provided informed consent, and the study was registered with ClinicalTrials.gov (NCT05301400). The research was partially funded by BTI® Biotechnology Institute, but the authors retained full control over the data and publication. Results: Pilot Study: The stress maps for the screws in both dental restorations under a 300 N load revealed that the screw in the implant experienced slightly less stress when a transepithelial component was used compared to a direct implant-supported restoration. The effective fatigue stress analysis for load cycles ranging from 100 to 400 N indicated that the stress on the screw in the direct implant restoration was almost identical to that in the implant screw of the transepithelial-supported restoration. Experimental validation confirmed that in transepithelial-supported restorations, the critical component shifts from the implant screw to the prosthetic screw. Clinical Study: Át three months, the average marginal bone loss was 0.24 mm, with a 100% survival rate for both implants and prostheses. No cases of chipping were observed, but 5.2% of implants experienced screw loosening. Át six months, the average bone loss increased to 0.45 mm, with continued 100% survival for both implants and prostheses. Chipping remained absent, while 3.4% of implants experienced loosening. The bone loss progression from three to six months averaged 0.20 mm. Significant differences were found between the study groups, with lower bone loss in Group Á and higher values in Group C at both time points. Post-hoc analysis confirmed statistically significant differences between the groups, particularly between Groups Á and C. Regarding secondary outcomes, the survival of implants and prostheses was 100% across all groups at both three and six months. Screw loosening was more common in Group C at six months, though no statistically significant differences were found between the groups. Discussion: Pilot Study: This study explored the fatigue behaviour of dental restorations with and without a transepithelial component. The findings demonstrated that the prosthetic screw connected to the transepithelial abutment is more likely to fracture than the screw directly connected to the implant. The use of a transepithelial component allows for easier management of screw fractures, preventing damage to the implant itself. The results align with previous research, indicating that the highest stress concentrations occur at the distal surface of the abutment screw, suggesting that this area is most prone to failure. Clinical Study: Marginal bone loss (MBL) is a significant concern in implantology, particularly in single implants. The type of abutment used, the height of the prosthetic abutment, and patient-specific factors like smoking and bone quality may influence MBL The use of transepithelial abutments, which allow for the "one abutment one time" protocol, was associated with reduced MBL. Prosthetic complications, particularly screw loosening, remain a common challenge in implant restorations. The study observed that screw loosening was more frequent in restorations with direct implant connections compared to those with transepithelial abutments. The study emphasizes the importance of evaluating biomechanical factors and optimizing implant restorations design to mitigate MBL and prosthetic complications. Conclusions: The study demonstrates that incorporating a trans-epithelial component in unitary implant restorations significantly redistributes load, positioning the upper screw as a protective "fuse" for the system. Regarding marginal bone loss, significant differences were observed between different restoration types at three and six months, confirming that bone loss depends on the type of restoration. Mechanical complications were minimal, with a 100% survival rate for implants and prostheses. Screw loosening was noted in some cases, particularly in one group, but not in the group using the trans-epithelial component. Clinical Implications and Recommendations: The use of intermediate abutments in unitary implants shows promise for improved load distribution and long-term stability. Further studies with larger sample sizes and longer follow-ups are recommended to confirm these findings and explore the benefits of combining intermediate abutments with platform switching for enhanced clinical outcomes.