Search Results (167)

Background: The implant–abutment joint is important for the long-term marginal tissue integrity in terms of biomimetic design that replicates the natural dentition under mastication forces. This study aimed to evaluate conical implant–abutment joints coupled at different tightening torque values through a mechanical fatigue test. Methods: Eighty conic implants (Ø: 3.8 mm L: 10 mm) with a 6° cone morse joint were embedded in resin blocks with an inclination of 30° ± 2°. The samples were divided into 8 groups (4 Test and 4 Control). The implant–abutment joints were coupled with different tightening torques: 25 Ncm (Group I), 30 Ncm (Group II), 35 Ncm (Group III) and 40 Ncm (Group IV). An in vitro cyclic loading test (1 × 10⁴ loads) was performed for 4 Test groups, while 4 Control groups did not receive any forces. All the samples were assessed with Scanning Electron Microscopy to compare the microfractures and microgaps on flexion and extension points. Results: Microscopy observation results showed significant differences among torque groups. We found that 30 Ncm had the best stability with less microgap. Conclusions: Tightening torque plays an important role in the distortion of the cone morse joint under mechanical forces. However, further studies should be conducted to validate the results using different implant–abutment joints for comparison. Full article

Achieving accurate fit in implant-supported prostheses is critical for avoiding mechanical complications; however, the influence of digital manufacturing techniques and abutment designs on misfit and preload remains unclear. This study evaluated the impact of different manufacturing techniques (CAD-cast and 3D printing) and abutment connection types (engaging [E], non-engaging [NE]) on the misfit and preload of implant-supported cantilevered fixed dental prostheses (ICFDPs). Misfit was measured at six points using scanning electron microscopy, and preload was assessed via eight strain gauges placed buccally and lingually on four implants. Frameworks were torqued to 35 Ncm, retorqued after 10 min, and subjected to 200,000 cycles of loading. Mean preload values ranged from 173.4 ± 79.5 Ncm (PF) to 330 ± 253.2 Ncm (3DP). Preload trends varied depending on the abutment type and manufacturing technique, with the 3DP group showing higher preload in engaging (E) abutments, whereas the CAD-cast group showed the opposite pattern. Although preload values varied numerically, these differences were not statistically significant (p = 0.5). In terms of misfit, significant differences were observed between groups (p < 0.05), except between CAD-cast E (86.4 ± 17.8 μm) and 3DP E (84.1 ± 19.2 μm). Additionally, E and NE abutments showed significant differences in misfit within both CAD-cast and 3DP groups. Overall, 3DP frameworks showed superior fit over CAD-cast. These findings suggest that 3DP may offer improved clinical outcomes in terms of implant–abutment fit. Full article

Background: Modification of diameter stability after the abutment retention can result in a decrease in the applied torque or affect the peri-implant tissue, compromising the longevity of the treatment. Therefore, this study aimed to investigate how different connection angles (11.5° and 16.0°) at the implant–abutment interface influence implant diameter stability under the manufacturer’s recommended torque. Methods: Eighty Morse cone-type implant specimens were divided into two groups, with different internal conicity angles: 11.5° (n = 40) and 16.0° (n = 40). Implants varied in diameter (mm): 3.5, 3.8, 4.5, and 5.0. Initial measurements of the implants’ external diameter were carried out. After these measurements, all implants received the abutment installation, and a final measurement of the external implant diameter was performed. Results: Considering the comparative analysis between the final and initial diameters, a non-significant increase in diameter, in the cervical implant region, after torque on the abutment, was observed. The torque applied to the abutments did not produce deformations in the cervical area of Morse taper implants. Conclusions: The torque applied to the abutment screw in implants with a Morse taper connection does not cause deformation in the cervical area of the implant body in implant with 11.5° and 16.0° conicity angles. Full article

Background/Objectives: Dental implants represent a viable solution for replacing missing teeth; however, multiple disconnections and reconnections of intermediate abutments contribute to the apical displacement of the peri-implant connective tissue barrier, resulting in additional marginal bone loss. To the best of our knowledge, no definitive customized abutments currently exist that are specifically designed according to the morphology of the tooth to be replaced and its position within the dental arch, allowing for digital planning within the prosthetic implant design and insertion during the surgical procedure without subsequent disconnection. Methods: The First Biological Respect (FR) technique, described in this case report, enables the digital planning not only of the implant but also of the patented FR customized-shaped, definitive abutment and associated FR prosthetic components. The FR technique was applied to a case involving an immediate post-extraction implant in position 12. Results: With the limitations of a case report, the application of the FR protocol demonstrated stable crestal bone levels at the 1-year follow-up. Additionally, soft tissue volume was maintained at 6 months, reflecting the accuracy of the customized prosthetic components in supporting, guiding, and protecting peri-implant soft tissues. At the 1-year follow-up, an increase in soft tissue volume was observed, likely attributable to tissue maturation and the further customization of the definitive prosthetic elements. Conclusions: The FR technique represents a viable therapeutic alternative that, through its patented, fully customized components, allows for the digital planning of the implant, as well as the customized definitive abutment, coping, provisional, and final prosthetic framework. This facilitates a single-stage surgical and prosthetic approach. By eliminating the need for repeated abutment disconnections, this method supports the long-term stability of both hard and soft peri-implant tissues while also reducing overall treatment time for both clinician and patient. Further studies involving larger patient cohorts are necessary to validate this protocol. Full article

Background and Objectives: This study aimed to evaluate marginal bone level (MBL) changes in implant-supported rehabilitation based on patient demographics, implant location, transmucosal abutment height, and crown emergence profile. Materials and Methods: A total of 50 patients (28 females and 22 males), with 111 implant–abutment (IA) sets, were analyzed. The mean age was 65.2 ± 10.9 years (range: 33–81). Implants were placed in the maxilla (68.5%) and mandible (31.5%), with an average evaluation period of 12.7 ± 4.1 months. MBL changes at mesial (MBLm) and distal (MBLd) sites were recorded and analyzed based on sex, age, implant location, abutment transmucosal height, and crown emergence profile. Statistical comparisons were performed using Bonferroni’s multiple comparison test and one-way ANOVA with Tukey’s post hoc test. Results: MBL changes did not show significant differences based on sex (p > 0.05) or age group (p > 0.05). However, maxillary implants exhibited greater bone loss than mandibular implants, though this difference was not statistically significant. Transmucosal abutment height (TMh) significantly influenced MBL, with taller abutments (TMh3: −1.07 ± 0.93 mm) showing less bone loss than shorter abutments (TMh1: −2.11 ± 1.82 mm) (p < 0.05). Crown emergence profile also affected MBL, particularly in the distal emergence profile, where design 1 exhibited the least bone loss compared to designs 2 and 3 (p = 0.0176). Conclusions: The study findings suggest that transmucosal abutment height and crown emergence profile significantly influence peri-implant bone stability. Transmucosal abutment height (> 2.5 mm) was associated with reduced bone loss. Further research is recommended to evaluate the long-term effects on peri-implant bone maintenance. Full article

Purpose: The aim of this study was to evaluate the long-term clinical results of two different implant–abutment connection types (screw-retained/Morse locking taper), marginal bone loss, and complications in prosthetic restorations. Materials and Methods: In 2017–2018, 579 implants and 242 implant-supported restorations applied to 137 patients were included in the study. Patients were recalled every six months, clinical evaluations were accomplished, and complications were recorded. When examining the distribution of prosthetic restorations by type, it was determined that 38 (15.70%) were single crowns, 136 (56.19%) were fixed partial cement-retained bridge restorations, 53 (21.90%) were fixed partial screw-retained bridge restorations, and 15 (6.19%) were overdenture prostheses. Findings: Overall, complications included eighteen (21.68%) retention losses, nineteen (22.89%) instances of screw loosening, twenty-one (25.30%) veneer ceramic fractures, three (3.61%) acrylic base fractures, fourteen (16.87%) cases of peri-implantitis, and eight (9.64%) implant losses. Conclusions: Differences in complication rates were observed between implants with different implant–abutment connection designs. While no significant differences were found regarding annual mesial and distal marginal bone loss for implants with conical locking connections, a significant difference was detected in those with screw-retained connections. In both implant groups, mesial and distal marginal bone loss progressed gradually over the follow-up period. Full article

Objectives: This study aimed to histologically evaluate, in humans, the orientation of collagen fibers around screw-less, Morse taper, hemispherical base abutments. Methods: This study was designed as an observational, case–control, clinical trial to evaluate the histological orientation of collagen fibers around implants. Biopsies of the peri-implant tissue were performed 8 (group A, control) or 16 (group B, test) weeks of implant uncovering, and histologically analyzed under optical microscope using Hematoxylin and Eosin, Masson, and Picro Sirius histochemical staining and a scanning electron microscope. Results: Eight patients were enrolled in this study and 16 biopsies were performed. All the biopsies were correctly analyzed. The histological examination of cross-sectional portions of the tissue taken 8 weeks after implant uncovering showed the almost complete absence of epithelial lining, while the connective tissue bundles in the superficial portion showed a lower circular pattern. The histochemical cross-section examination of the tissue taken 16 weeks after implant uncovering showed the partial presence of non-keratinizing epithelial lining at the implant site and the collagen bundles showed a greater organization, with a circumferential course around the abutment. At 8 weeks, the final histological analysis showed an average height of 1.01 mm for the keratinized epithelium, 0.83 mm for the non-keratinized epithelium, and 1.39 mm for the connective tissue. While, at 16 weeks, the values were 1.20 mm, 0.48 mm, and 1.11 mm, respectively. No statistically significant differences were found between the groups (p > 0.05). Conclusions: Histologically, there were not any differences in the height and profile of the gingiva between 8 and 16 weeks of healing after prosthesis delivery. Greater organization of the collagen fibers with a circumferential course around the abutment was found in the test group (16 weeks) compared with the control group (8 weeks). Full article

Background: In dental implants, micro-gaps at the fixation–abutment interface can cause peri-implantitis and/or loosening or loss of the fixation screw; therefore, three-dimensional imaging is widely used to examine different types of connections. In the present study, we focus on the analysis on biconometric connections to detect and (possibly) measure the presence of micro-gaps in the as-positioned state and after repeated loading and unloading. Methods: Seven biconometric dental implants were characterized using micro-computed tomography (micro-CT). In two specimens (group 1), the cap was inserted, and only the apical portion was imaged, to evaluate the cap–abutment connection; in the remaining five specimens (group 2), the fixture–abutment connection was analyzed. Two implants in group 2 were also subjected to load tests to verify whether stresses could induce the formation of micro-gaps as a consequence of preload loss. Results: Micro-CT analysis showed the absence of micro-gaps greater than 10 µm in both cap–abutment and abutment–fixture connections. This was verified, in the fixture–abutment connection, even after mechanical loading and unloading. The results were reproducible in all the investigated samples in the different experimental conditions. Conclusions: In the human force range during chewing, the conical connection showed a high level of resistance to micro-gap formation at the implant–abutment interface. The absence of micro-gaps, as demonstrated here, provides encouraging preliminary data regarding the stability of the biconometric connections, which will be further verified in follow-up studies on a larger sample size. Full article

Dental implants rely on precise prosthetic design and biomechanical stability to ensure long-term success. This study evaluates the mechanical performance of non-engaging abutments in multi-unit combined screw- and cement-retained prostheses (CSCRP) using two internal implant systems: the BlueDiamond (BD) and AnyOne (AO) systems. Unlike conventional implant systems that utilize the same type of screw for both engaging and non-engaging abutments, the BD system employs a distinct screw design for non-engaging abutments. A total of 80 implants were tested, with 40 in each group. Mechanical testing included static compressive load and fatigue tests following ISO 14801 standards. The BD system demonstrated significantly higher compressive strength (326.32 kgf vs. 231.82 kgf, p < 0.001) and 23.4% greater fatigue strength compared to the AO system. Precision fit analysis confirmed no significant deformation, microcracks, or fractures after 5 million loading cycles. These findings suggest that the BD system’s unique screw design for non-engaging abutments contributes to improved mechanical performance and durability. Further clinical studies are needed to assess the long-term implications of this design on prosthetic stability and implant longevity. Full article

Aims: This in silico study aimed to investigate the effect of implant–abutment contact surfaces on the stress generation of Morse taper implants under oblique loading. Materials and methods: Three-dimensional finite element models of Bone-Level and Tissue-Level implants were simulated with Standard and Partial contacts between the abutment and implant. The dimensional parameters followed the ISO 14801 guidelines, and an oblique load of 300 N was applied to the implants. The von Mises stress was acquired. Results: The Tissue-Level design showed a significant difference in the stress level when the connection with the implant, abutment, and screw was Partial. For the implant fixture, abutment, and screw, the Tissue-Level design showed 13% more stress in the implant, abutment, and screw when the connection was Partial. The Bone-Level design did not affect the connection and showed an overall 42% lower stress than the Tissue-Level design for the implant fixture. However, in the screw, there was a difference between the Bone-Level implants with a Standard and Partial connection. In contrast, for the Tissue-Level implant, this difference was less evident with higher stress peaks in the entire set. Conclusion: To achieve optimal outcomes, it is highly recommended to use original abutments, as they provide a more precise fit. The stress peaks were notably lower in Bone-Level implants compared to Tissue-Level implants. Furthermore, an implant–abutment connection with more contacting areas significantly reduced stress concentration, especially in Tissue-Level implant designs. By choosing well-fitting abutments, one can ensure more stable and durable implant performance with less stress. Full article

Background/Objectives: Internal implant–abutment connection has been proposed to increase interface stability and reduce biological and prosthetic issues. The aim of the present investigation was to evaluate the influence of the implant abutment conical angle on marginal bone loss and mechanical complications. Methods: The literature screening was performed by considering Pubmed/MEDLINE, EMBASE, and Google Scholar sources. The eligibility process was conducted in order to perform a descriptive synthesis, determine the risk of bias, and carry out network meta-analyses. The following categories were considered for pairwise comparisons: external hexagon (EI), internal hexagon (HI), cone morse (CM) (<8° contact angle), and conometric joint (>8° contact angle). For the descriptive data synthesis, the following parameters were considered: sample size, implant manufacturer, prosthetic joint type, prosthetic complications, marginal bone loss, and study outcomes. Results: A total of 4457 articles were screened, reducing the output to the 133 studies included in the descriptive synthesis, while 12 articles were included in the statistical analysis. No significant differences in marginal bone loss were reported when comparing a cone angle of <8° and a cone angle of >8; Conclusions: Within the limits of the present investigation, the cone interface seems to produce lower marginal bone loss compared to external and internal hexagon connection. No differences were found when comparing a cone angle of <8° and a cone angle of >8°. Full article

This study aimed to evaluate the retrievability and potential damage to implant–abutment connections caused by fractured abutment screw removal using conventional and drilling techniques. A total of forty abutment screws were randomly inserted into forty dental implants, and then they were fractured and extracted using different removal methods: Group A employed a conventional approach utilizing an exploration probe and an ultrasonic device without irrigation (n = 10) (conventional); Group B used the Phibo drilling removal system without irrigation (n = 10) (Phibo); Group C utilized the Rhein83^® drilling removal system without irrigation (n = 10) (Rhein83); and Group D implemented the Sanhigia^® drilling removal system without irrigation (n = 10) (Sanhigia). Pre- and postoperative micro-computed tomography (micro-CT) scans were performed on the dental implants, and Standard Tessellation Language (STL) digital files were generated for morphometric analysis to measure the wear volume. ANOVA was used to assess the volumetric differences (mm³) and percentage ratios of the internal thread volumes of the implant–abutment connections before and after the procedures. Results: This study found no statistically significant differences in the volumetric and percentage ratios of internal threads among the implant groups (Phibo, Rhein83, Sanhigia, and conventional). However, the success rate for retrieving fractured abutment screws was higher (90%) with the drilling systems compared to the conventional technique (50%). These results suggest that drilling systems are more effective for the retrieval of damaged screws. Although drilling techniques without irrigation demonstrated higher removal efficiency compared to the conventional method, both approaches resulted in similar wear volumes at the implant–abutment connections when used to extract fractured screws. Full article

Introduction: This preliminary in vitro study aims to evaluate the application of micro-CT in analyzing the microstructural coupling between dental implant fixtures and prosthetic abutments, with an emphasis on understanding the effectiveness and limitations of this technique in dental implantology. Materials and Methods: A search of PubMed, MEDLINE, and the Cochrane Library up to May 2024 identified eight relevant studies that examined different facets of dental implantology, such as osseointegration, implant stability, and the comparative accuracy of micro-CT versus other imaging techniques. A comparative micro-CT radiographic analysis was performed on five different implant fixtures with respective prosthetic and healing abutments, by using SkyScan1174 micro-CT. Results: The reviewed studies demonstrated that micro-CT is reliable for assessing bone quality, implant stability, and the microstructural integrity of dental implants. Micro-computed tomography (micro-CT) studies reveal bone–implant contact (BIC) ratios of 40–80%, bone volume per total volume (BV/TV) values of 20–60%, and detect microgaps as small as 0.3 µm, highlighting its high-resolution capability (5–10 µm) for detailed implant analysis. The comparative analysis of the implant fixtures analyzed the implant–abutment connection, highlighting the relevance of implant design for ensuring stability. Conclusions: Micro-CT analysis has proven to be a valuable tool for evaluating the intricate microstructural properties of dental implants, offering insights into implant stability, bone quality, and osseointegration. The literature reviewed highlights consistent findings that underscore micro-CT’s accuracy and reliability in capturing high-resolution data, suggesting its potential as a standard imaging modality in implant research and clinical assessment. Full article

This study investigates the impact of tightening torque (preload) and the friction coefficient on stress generation and fatigue resistance of a Ti-6Al-4V abutment screw with an internal hexagonal connection under dynamic multi-axial masticatory loads in high-cycle fatigue (HCF) conditions. A three-dimensional model of the implant–abutment assembly was simulated using ANSYS Workbench 16.2 computer aided engineering software with chewing forces ranging from 300 N to 1000 N, evaluated over 1.35 × 10⁷ cycles, simulating 15 years of service. Results indicate that the healthy range of normal to maximal mastication forces (300–550 N) preserved the screw’s structural integrity, while higher loads (≥800 N) exceeded the Ti-6Al-4V alloy’s yield strength, indicating a risk of plastic deformation under extreme conditions. Stress peaked near the end of the occluding phase (206.5 ms), marking a critical temporal point for fatigue accumulation. Optimizing the friction coefficient (0.5 µ) and preload management improved stress distribution, minimized fatigue damage, and ensured joint stability. Masticatory forces up to 550 N were well within the abutment screw’s capacity to sustain extended service life and maintain its elastic behavior. Full article

The geometry of implants plays a crucial role in the success of All-on-Four treatments for the lower jaw. This study builds upon prior research by evaluating the biomechanical performance of implant-supported prostheses in full-arch fixed dental restorations, specifically focusing on different implant lengths and connection types in cases of mild atrophic resorption of the mandible. Four groups were analyzed using finite element analysis (FEA): We utilized 13 or 18 mm posterior 17-degree tilting implants, each paired with two kinds of abutment connections. The external hexagon connection (EHC) group utilized 4 mm diameter implants, while the internal hexagon connection (IHC) group employed 4.3 mm diameter implants. A vertical force was applied to the cantilever region located at the distal side of the posterior implant. The maximum stress regions were observed in prosthetic screws and multi-unit abutments (MUAs) across all groups, with the lowest von Mises stress values noted in the bone. Stress peaks for implant screws and fixtures in the 13 mm group were 19.98% and 11.42% lower, respectively, compared to the IHC group. Similarly, in the 18 mm group, stress peaks were reduced by 33.16% and 39.70% for the EHC group compared to the IHC group. The stress levels on all components remained below the ultimate strength of the titanium alloy. For the same implant lengths, the stress in the prosthetic screw, MUAs, implant screw, and implant fixture positions was lower in the EHC group. When implant length was increased, a decrease in stress levels was observed in the implant screw and fixture of the EHC group and only in the implant screw of the IHC group. However, an increase in stress was noted in the prosthetic screw and MUAs for both groups. Full article