Search Results (194)

Advanced dental implant systems are clinically successful when their material properties, surface topography, abutment geometry and implant–abutment connection design support both mechanical stability and biological integration. In Morse-tapered implant–abutment systems and conometric prosthetic retention systems, the precision of conical interfaces has traditionally been discussed mainly in biomechanical terms; however, their clinical performance also depends on the formation and maintenance of a stable peri-implant soft tissue seal. This review examines micro-computed tomography (µCT), with emphasis on synchrotron radiation-based phase-contrast micro-computed tomography (SR-PhC-µCT), as an advanced characterization strategy for evaluating how implant and abutment design influence the three-dimensional architecture of peri-implant connective tissues. The review summarizes the biological organization of the peri-implant mucosa, the technical basis of absorption- and phase-contrast microtomography, sample preparation protocols, segmentation workflows, artificial intelligence-assisted image analysis and quantitative morphometric descriptors of collagen organization. Particular attention is given to human retrieval and biopsy studies of Morse-tapered/conometric systems, where three-dimensional imaging has revealed interwoven circumferential and longitudinal collagen bundles around the transmucosal implant component. These microarchitectural features have been directly visualized by SR-PhC-µCT and histology and may represent a biomechanically plausible basis for mucosal sealing and force distribution. However, their direct relationship with marginal bone preservation and long-term clinical outcomes remains to be demonstrated in longitudinal studies. Within the scope of advanced dental materials, the novelty of this review lies in framing SR-PhC-µCT, correlative histology and AI-assisted segmentation as enabling tools within a materials-design framework for implant–abutment optimization. In this framework, peri-implant collagen architecture is interpreted as an exploratory structural readout of the interaction among connection design, abutment geometry, surface topography and biological response. This approach does not yet establish validated clinical biomarkers, but it may generate testable hypotheses for future studies aimed at improving peri-implant soft tissue stability and implant–abutment system design. Full article

This study evaluated the biomechanical performance of different abutment types, superstructure materials, prosthetic designs, and loading conditions in the implant-supported rehabilitation of three consecutive missing teeth in the mandibular posterior region using three-dimensional finite element analysis (3D-FEA). Twenty FEA models were constructed, simulating two-implant (pontic, mesial, and distal cantilever) and three-implant (splinted and unsplinted) configurations using multi-unit and Ti-base abutments composed of titanium alloy (Grade 5, Ti-6Al-4V), with monolithic zirconia and zirconia-supported feldspathic porcelain superstructures. Functional and parafunctional (bruxism) vertical and oblique loads were applied to analyze von Mises stresses in the components and principal stresses in the peri-implant bone. The results indicated that two-implant models generated higher stress concentrations than three-implant models, and unsplinted or cantilevered designs produced elevated stresses compared to splinted or pontic designs. Ti-base abutments resulted in greater stress accumulation in the connection complex compared to multi-unit systems. Under vertical and oblique parafunctional forces, stress values on the abutments in distal cantilever models—particularly in unsplinted Ti-base designs under oblique loading—exceeded the yield strength of the Ti-6Al-4V alloy (890 MPa), indicating a substantial risk of plastic deformation. To optimize biomechanical stability, three-implant-supported, splinted designs utilizing Multi-unit abutments should be prioritized. Avoiding distal cantilevers and unsplinted designs is critical in patients with bruxism to minimize the risk of mechanical failure in the Ti-6Al-4V components. Full article

Peri-implantitis, a biofilm-driven inflammatory disease that causes progressive loss of the bone supporting dental implants, is common and difficult to treat: mechanical debridement cannot fully decontaminate the implant surface, and antibiotic adjuncts act non-selectively while promoting resistance. Antimicrobial peptides (AMPs) have emerged as a promising preventive strategy. As cationic, membrane-disrupting molecules they kill a broad spectrum of organisms with a low propensity to select for resistance, and as host-defense peptides they additionally modulate inflammation and promote epithelial and connective-tissue repair. This review examines AMP-functionalized titanium as a prospective strategy against peri-implantitis through a dermatological lens, drawing on the established roles of the cathelicidin LL-37 and the β-defensins in cutaneous and oral wound healing. We argue that the peri-implant transmucosal interface behaves as a healing epithelial barrier, so that a single class of host-defense peptides can address two goals usually pursued separately—suppressing the peri-implant biofilm and reinforcing the soft-tissue seal. Because peri-implant disease initiates at the transmucosal region, we give particular attention to the abutment or transmucosal collar as the primary sealing target, and we consider how the concept extends to zirconia and hybrid components. The evidence assembled here, however, is predominantly preclinical, derived from in vitro and animal studies, and does not yet demonstrate clinical prevention of peri-implantitis in patients. After surveying peri-implant epidemiology, microbiology, AMP biology, surface-engineering strategies, and the in vivo evidence, we appraise the translational barriers—stability, cytotoxicity, cost, regulation, and the absence of human trials—that remain. We conclude that biologically intelligent, multifunctional peptide coatings represent a rational direction for next-generation implant surfaces. Full article

Objectives: To evaluate the influence of implant–abutment connection design, implant diameter, and simulated marginal bone loss on fracture resistance and failure patterns of dental implant systems. Materials and Methods: A total of 180 implant–abutment assemblies were tested, including Morse taper (MT) and internal hex (IH) connections with diameters of 3.5, 4.0, and 5.0 mm. Implants were embedded at two simulated bone levels (0 and 3 mm) and loaded at 30° until failure, in accordance with ISO 14801:2015. Fracture resistance (N) was analyzed using three-way ANOVA. Results: Connection type, implant diameter, bone level, and their interactions significantly affected fracture resistance (p < 0.001). Internal hex implants showed a marked diameter-dependent increase in resistance and greater reduction under simulated bone loss, particularly in reduced diameters. In contrast, Morse taper implants demonstrated similar resistance values regardless of implant diameter or bone level. Failure patterns also differed between systems: internal hex implants exhibited cervical implant fractures in reduced diameters, whereas Morse taper implants showed progressive abutment deformation and/or abutment fracture without implant body fracture. Conclusions: Implant fracture resistance is strongly influenced by implant–abutment connection geometry. Within the limitations of this static in vitro study, MT systems demonstrated diameter-independent mechanical stability and prosthetic-controlled failure patterns, whereas IH systems were highly sensitive to diameter reduction and simulated bone loss. Full article

Marginal bone preservation around osseointegrated dental implants continues to represent a critical challenge in modern implant dentistry. To address this issue, subcrestal implant placement along the apico-coronal axis has been proposed as a reliable clinical strategy aimed at reducing the risk of implant thread exposure within the oral environment. In the present study, 38 healthy patients were treated with either bone-level implants (BLG-Control) or implants positioned 2 mm subcrestally (SCG-Test). All implants featured an internal conical connection and a platform-switching design. In addition, implants in the test group were restored using an immediate tissue-level abutment following the one-time abutment (OTA) protocol. Marginal bone modifications (MBMs) were evaluated through standardized radiographic examinations performed at surgery (T0), implant loading (T1), and after 6 (T2), 12 (T3), 24 (T4), and 36 (T5) months of functional loading. MBMs, meaning the overall changes in the radiographic bone structure over time, were categorized as bone loss (BL) when occurring apical to the implant neck, and as bone remodeling (BR) when detected coronally to the implant neck. Clinical parameters, including probing pocket depth (PPD), bleeding on probing (BoP), and plaque index (PI), were also recorded and analyzed throughout the follow-up period. At the 36-month evaluation, mean MBM values were 0.61 mm for the test group and 0.58 mm for the control group. After three years of follow-up, the test group demonstrated a mean PPD of 2.03 mm, compared with 2.78 mm in the control group. Bleeding on probing was recorded at 13% in the test group and 11% in the control group, while plaque index values were 11% and 5%, respectively. Within the limitations of the present investigation, implants placed 2 mm subcrestally and characterized by an internal conical connection combined with platform switching demonstrated favorable clinical and radiographic outcomes over a short- to medium-term observation period of three years. When compared with equicrestally positioned implants, the subcrestal approach seemed to favor the peri-implant hard tissue conditions while reducing the possibility of marginal bone loss below the implant neck. However, one should bear in mind that this clinical behavior applies specifically to the investigated implant design and should be interpreted within the limitations of the present study. Full article

Background: Stabilization of surgical guides in fully edentulous patients remains a clinical challenge due to mucosal resilience and potential micromovement, even when fixation pins are used. Guide instability may affect drilling accuracy and overall workflow predictability. This proof-of-concept case series describes a stabilization approach based on pre-placed tripod reference implants with multi-unit coupling, designed to create a mechanically defined prosthetic docking platform for fully guided implant surgery. Methods: Three fully edentulous patients requiring implant-supported rehabilitation were treated using a two-stage protocol. Three temporary reference implants were inserted in a tripod configuration 7–10 days prior to definitive surgery. Multi-unit abutments were mounted on the reference implants, and intraoral scanning was performed to design a surgical guide indexed to the prosthetic interfaces. During implant placement, the guide was screw-retained to the reference implants via the multi-unit connections. Postoperative implant positions were evaluated radiographically by superimposing postoperative datasets onto the preoperative planning model. Intraoperative guide stability, surgical events, and early postoperative outcomes were recorded. Results: Stable guide fixation was achieved in all three cases without detectable intraoperative displacement. Implant placement was completed as planned in each patient, and removal of the temporary reference implants was uneventful. No intraoperative or early postoperative complications were observed. Mean coronal, apical, and angular deviations between planned and achieved implant positions were 0.70 ± 0.16 mm, 0.39 ± 0.13 mm, and 3.30 ± 0.59°, respectively. These preliminary findings, derived from four treated arches, were comparable to ranges reported in selected studies on fully guided implant surgery; however, no direct statistical comparison with previously published datasets was performed. Conclusions: Within the limitations of this proof-of-concept case series, temporary reference implants arranged in a tripod configuration provided a stable and reproducible prosthetic indexing platform for guided implant surgery in fully edentulous patients. Further prospective studies involving larger patient cohorts and controlled comparative designs with conventional mucosa-supported or fixation-pin-supported surgical guides are required to evaluate the reproducibility, clinical performance, and long-term applicability of this stabilization concept. Full article

Implant screw loosening remains among the most frequently reported technical complications in implant-supported prostheses and may compromise prosthetic stability, maintenance requirements, and long-term clinical outcomes. Etiology is multifactorial and involves biomechanical, prosthetic, occlusal, and patient-related factors. This narrative review aimed to synthesize medium- and long-term clinical evidence (>5 years whenever available) regarding mechanisms, prevalence, and risk factors associated with screw loosening in implant-supported restorations. A structured literature search was conducted in PubMed, Web of Science, Cochrane Library, and EBSCOhost to identify clinical studies, randomized controlled trials, systematic reviews, and meta-analyses. Evidence regarding preload, implant–abutment connection design, retention type, implant splinting, framework fit, abutment angulation, implant dimensions, occlusal loading, parafunction, full-arch restorations, and torque protocols was critically interpreted. Current evidence indicates that screw loosening is influenced by inadequate preload, unfavorable occlusal forces, cantilevers, angulated abutments, framework misfit, and parafunctional habits. Single-unit and screw-retained restorations appear to exhibit higher complication rates in several studies, although findings remain inconsistent. Internal connections and splinting may improve mechanical stability; however, superiority has not been conclusively demonstrated. Most screw loosening events occur during the early functional period, emphasizing the importance of preload optimization, occlusal control, maintenance, and follow-up. High-quality long-term comparative studies remain limited. Full article

Background/Objectives: Peri-implantitis is a common complication affecting approximately 24% of dental implants and is characterized by progressive bone loss and reduced implant stability. Implantoplasty, an intraoral procedure used to remove biofilm by machining the titanium implant surface, has become increasingly common in clinical practice. However, this procedure may compromise the mechanical integrity of implants, especially when combined with peri-implant bone loss, potentially leading to premature fatigue failure. This study evaluated the effect of different marginal bone resection depths, with and without implantoplasty, on the cyclic mechanical behavior of dental implants. Methods: A total of 200 commercially pure grade 4 titanium implants were embedded in resin simulating human bone at depths of 3, 4, and 5 mm. A subset of implants underwent implantoplasty with a 0.4 mm surface reduction corresponding to the thread width. Finite element analysis was performed to evaluate von Mises stress distribution and predict fatigue behavior. Numerical results were experimentally validated using a servo-hydraulic MTS Bionix system under ISO 14801:2016 conditions. Fatigue limits were determined from the asymptotic region of the load–cycles-to-failure (S–N) curves, and fracture surfaces were examined by scanning electron microscopy. Results: Maximum von Mises stresses were concentrated at the thread–body transition and increased with greater marginal resection depth, with additional stress amplification observed after implantoplasty. Fatigue limits for untreated implants were approximately 351 N, 285 N, and 210 N for 3-, 4-, and 5 mm resections, respectively. Implants subjected to 0.4 mm implantoplasty showed fatigue limits of 311 N, 270 N, and 90 N, respectively. Failure patterns were load-dependent: higher loads produced coronal fractures, whereas lower loads resulted in failure at the implant–abutment connection. Finite element predictions showed strong agreement with the experimental results. Conclusions: Excessive marginal resection significantly decreases the fatigue resistance and long-term mechanical reliability of dental implants, particularly when combined with implantoplasty. The main limitations of this study include is in vitro design, the assumptions inherent to the numerical models, and the variability associated with implantoplasty procedures. Full article

Background/Objectives: This narrative review aimed to critically assess the role of multi-unit abutments in implant dentistry, focusing on mechanical reliability and biological stability at the implant–abutment interface. Methods: A literature search was performed in PubMed/MEDLINE, Scopus, Web of Science and Google Scholar to identify clinical studies and experimental research from the past 20 years addressing implant–abutment connections, mechanical complications and biological integration of multi-unit abutments. Results: Dental implants demonstrate survival rates above 95%, yet complications, up to 35%, are primarily linked to the implant–abutment interface. Mechanical issues, especially screw loosening, may be mitigated with conical connections and adherence to evidence-based protocols. Biologically, multi-unit abutments with sufficient transmucosal height contribute to stable supracrestal tissue and preservation of marginal bone. Advances such as nanostructured surfaces and the concept of mucointegration represent a shift toward biologically active interfaces, enhancing peri-implant soft tissue health. Conclusions: Multi-unit abutments have evolved from simple angulation-correction tools to essential components across a wide range of clinical applications. Their success relies on strategic, protocol-driven use that integrates mechanical strength with biological harmony, enabling potentially favorable outcomes in modern implant dentistry, particularly in well-selected clinical scenarios. Full article

A clinically unresolved question in full-arch implant rehabilitation is whether early peri-implant bone adaptation is primarily a local (implant-level) phenomenon, a shared within-arch response, or a patient-level characteristic—information is unavailable from conventional mean-based outcome reporting. This prospective secondary analysis quantified the hierarchical distribution of peri-implant marginal bone level change (ΔMBL) in monolithic zirconia full-arch prostheses directly connected to multi-unit abutments during the first year of function. Unlike mean-based endpoints, this approach identifies whether early bone adaptation variability originates primarily at the implant, prosthetic-arch, or patient level. Of 308 implants placed in 40 completely edentulous patients rehabilitated with 49 prostheses, 2 implants failed before delivery of the definitive prosthesis and were excluded from radiographic analysis, leaving 306 implants available for multilevel analysis. Implant-level ΔMBL was analyzed using an unconditional three-level linear mixed-effects model. Implant survival was 99.2%, prosthetic survival was 100%, and mean ΔMBL at 12 months was 0.38 ± 0.27 mm. Variance partitioning showed that 60.8% of total variability occurred at the implant level, 28.4% occurred at the patient level, and 10.8% occurred at the prosthetic-arch level, providing a framework for identifying at which level of the restorative system future clinical interventions may have the greatest impact. Findings should be interpreted within the context of a secondary analysis with a 12-month follow-up and no explanatory covariates; longer-term comparative studies with explanatory multilevel designs are required to confirm and extend these observations. Full article

This study evaluated how abutment screw preload affects peri-implant bone under vertical dynamic loading using an in vivo rabbit tibia model. Eight Japanese white rabbits received two implants in each tibia. After 8 weeks of healing, implants were assigned to a control group without abutment connection or to abutment-connected groups tightened to 35 Ncm or 70 Ncm. The abutment groups were further divided into loading and non-loading subgroups. In the loading groups, vertical dynamic loading (50 N, 3 Hz, 1800 cycles) was applied twice weekly for 4 weeks. Peri-implant bone responses were assessed by micro-computed tomography, histology, and histomorphometry. Under loading conditions, the 35 Ncm group showed significantly higher bone volume, bone-to-implant contact, and bone area fraction than the 70 Ncm group (p < 0.05). Histologically, the 35 Ncm group exhibited more continuous cortical bone and new bone formation, whereas the 70 Ncm group more frequently showed cortical discontinuity and enlarged marrow spaces. Within the limitations of this animal study, abutment screw preload influenced peri-implant bone adaptation under repeated loading, and the manufacturer-recommended torque of 35 Ncm was associated with more favorable bone parameters than the 70 Ncm condition. Full article

Microleakage at the implant–abutment interface represents a potential pathway for bacterial penetration and may contribute to peri-implant inflammation, marginal bone loss, and mechanical complications such as screw loosening. The increasing clinical use of compatible prosthetic abutments as cost-effective alternatives to original components has raised concerns regarding their fit, sealing capacity, and mechanical stability at this interface. The aim of this in vitro study was to evaluate differences in sealing capacity and torque loss between original and non-original abutments in a mixed internal connection implant system and to investigate the applicability of a novel quantitative approach for assessing microleakage based on a hydraulic conductance perfusion system. Nine abutments, including four multi-unit and five screw-retained cementable abutments, were connected to Straumann Bone Level implants at two tightening torques (5 N·cm and 35 N·cm). Microleakage was quantified by measuring fluid transport across the implant–abutment interface using the perfusion system, and removal torque values were recorded after testing. Non-original abutments exhibited significantly greater microleakage than original abutments at both torque levels. Microleakage increased significantly when the installation torque was reduced to 5 N·cm. At the manufacturer-recommended torque, screw-retained cementable abutments demonstrated higher microleakage than multi-unit abutments. Non-original abutments also showed significantly greater torque loss. These findings suggest that original abutments provide improved sealing capacity and mechanical stability at the implant–abutment interface, while the hydraulic conductance perfusion system represents a promising quantitative tool for investigating microleakage. Full article

The increasing prevalence of peri-implantitis has led to a growing clinical use of implantoplasty, a procedure involving intraoral machining of the dental implant surface to remove biofilm. The absence of standardized clinical protocols may contribute to premature fatigue failure of dental implants. The present study aimed to evaluate the influence of machining depth on the cyclic mechanical behavior of dental implants. A total of 250 commercially pure grade 4 titanium dental implants were distributed into four groups according to machining depth: untreated (original), 0.2 mm, 0.4 mm, and 0.6 mm wall reduction. The implant system featured an internal connection with a thread height of 0.4 mm. Finite element analysis was performed for each machining depth to evaluate von Mises stress distribution and simulate fatigue behavior. The numerical models were validated through experimental fatigue testing using a servo-hydraulic MTS Bionix testing machine under ISO 14801:2016 conditions, showing a high correlation between simulated and experimental results (correlation coefficients > 0.9). The results indicated that maximum von Mises stresses were concentrated at the junction between the implant thread and the implant body. The fatigue limit of the untreated implants was approximately 351 N. Implants subjected to 0.4 mm machining exhibited a fatigue limit of 301 N, whereas lower fatigue limits were observed for 0.2 mm (255 N) and 0.6 mm (185 N) reductions. These findings suggest a significant mechanical effect of thread removal: 0.4 mm implantoplasty may provide improved fatigue performance compared to 0.2 mm, potentially due to reduced stress concentration at the thread–body junction. At high applied loads, fracture occurred in the coronal region of the implant, whereas at lower loads failure shifted to the implant–abutment connection. Although a good agreement between numerical and experimental results was observed, these findings should be interpreted with caution due to the in vitro testing conditions and the assumptions inherent to the finite element simulations. Therefore, while the results suggest that implantoplasty depth should not exceed the original thread height, further validation under clinically relevant conditions is required to confirm its impact on long-term mechanical reliability. Full article

The lack of integrity at the implant–abutment junction (IAJ) contributes to problems such as micromovements and microbial colonisation. This study aimed to (1) design a protocol for assessing microleakage at the IAJ using chromophore analysis not previously reported for this specific application, (2) compare gas and dye leakage between titanium (Ti) and cobalt chrome (CoCr) abutments, and (3) assess the effect of gold (Au) gilding on sealing. Forty abutments were divided into five groups: milled Ti (MTi); cast CoCr (CCoCr); milled CoCr (MCoCr); cast CoCr with Au gilding (CCoCrG); and milled CoCr with Au gilding (MCoCrG). Samples were subjected to internal pressure within a gas and dye reservoir. Chromophore analysis via UV-Vis spectrometer was used to calculate crystal violet leakage concentrations. Scanning electron microscopy (SEM) revealed close adaptation in the MTi and MCoCr groups, contrasting with irregularities in the CCoCr groups. Correspondingly, gas leakage and dye leakage were most prevalent in the CCoCr group. Fisher exact test demonstrated a statistically significant difference (p = 0.026) between the MCoCr and CCoCr abutments. While CCoCr exhibited the highest failure rate (62.5%), Au gilding demonstrated a trend toward reduced leakage (25% failure rate), though this did not reach statistical significance (p = 0.315). This chromophore analysis represents a viable and objective assessment of IAJ integrity. Full article

The accuracy of digital impressions in fully edentulous cases is limited by the lack of anatomical reference structures, potentially affecting passive fit. The effects of scanner type, impression level, and scan body splinting on accuracy remain insufficiently elucidated. This in vitro study aimed to evaluate the effects of different intraoral scanners, scanning levels, and scan body splinting methods on digital impression accuracy. A fully edentulous mandibular model with four implants (All-on-4) was fabricated, and scan bodies were connected at either the implant or multi-unit abutment level. Five splinting methods (nonsplinted, floss, orthodontic elastomeric, chain attachments, and single attachments) were applied, creating 10 experimental groups. Each group was scanned using three intraoral scanners: iTero Lumina (Align Technology, Tempe, AZ, USA), TRIOS 3 (3Shape A/S, Copenhagen, Denmark), and Medit i700 (Medit Corp, Seoul, Republic of Korea), with four repeated scans per scanner (120 scans total). Trueness and precision were assessed based on linear and angular deviations using Geomagic Control X (3D Systems, Rock Hill, SC, USA). Scanner type and scanning level significantly affected accuracy (p < 0.05), with TRIOS 3 showing higher deviations, while multi-unit abutments reduced deviations. Splinting methods showed no significant effect on accuracy, and precision did not differ among groups. Scanner type and scanning level significantly influenced digital impression accuracy; however, splinting methods yielded no significant effect. Precision remained comparable among groups. Full article