Search Results (150)

Background/Objectives: Dental practitioners widely use dental implants to treat traumatic cases. Titanium implants are currently the most popular choice among dental practitioners and surgeons. The discovery of newer polymeric materials is also influencing the interest of dental professionals in alternative options. A comparative study between existing titanium implants and newer polymeric materials can enhance professionals’ ability to select the most suitable implant for a patient’s treatment. This study aimed to investigate material property advantages of high-performance thermoplastic biopolymers such as PEEK and PEKK, as compared to the time-tested titanium implants, and to find the most suitable and economically fit implant material. Methods: Three distinct implant material properties were assigned—PEEK, PEKK, and commercially pure titanium (CP Ti-55)—to dental implants measuring 5.5 mm by 9 mm, along with two distinct titanium (TI6AL4V) abutments. Twelve three-dimensional (3D) models of bone blocks, representing the mandibular right molar area with Osseo-integrated implants were created. The implant, abutment, and screw were assumed to be linear; elastic, isotropic, and orthotropic properties were attributed to the cancellous and cortical bone. Twelve model sets underwent a three-dimensional finite element analysis to evaluate von Mises stress and total deformation under 250 N vertical and oblique (30 degree) loads on the top surface of each abutment. Results: The study revealed that the time-tested titanium implant outperforms PEEK and PEKK in terms of marginal bone preservation, while PEEK outperforms PEKK. Conclusions: This study will assist dental practitioners in selecting implants from a variety of available materials and will aid researchers in their future research. Full article

The design of custom abutments (CA) can affect the mechanical reliability of implant-supported restorations. The purpose of the study was to evaluate the influence of design parameters on the fatigue limit of CA and to compare optimized custom designs with the reference abutment (RA). A morse-tapered dental implant, an anatomical abutment, and a connector screw were digitalized using microcomputed tomography. A cone beam computed tomography scan was obtained from one of the authors to virtually place the implant-abutment assembly in the upper central incisor. Ten design parameters were selected according to the structural geometry of the RA and the implant planning. A reverse-engineered RA model was created in SOLIDWORKS and was modified considering a Taguchi orthogonal array to generate 36 CAs with ±20% dimensional variations. Finite element analysis was conducted in ABAQUS, and fatigue limits were estimated using Fe-safe. ANOVA (α = 0.1) identified the most influential parameters. Von Mises stress values ranged from 229 MPa to 302 MPa, and 94.4% of the CAs had a higher fatigue limit than the RA. Three parameters significantly affected the fatigue performance of the implant system. The design process of custom abutments includes critical design parameters that can be optimized for longer lifetimes of implant-abutment restorations. 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

The existing scientific literature lacks comprehensive information regarding the influence of zirconia crown height on debonding and fracture of the ceramic restorations on titanium base abutments. Additionally, there is a lack of comparative studies evaluating different types of zirconia as restorative options for screw-retained restorations. Purpose: The purpose of this study was to assess the fracture strength and the failure modes of the zirconia crown/titanium abutment complex by investigating the impact of increasing the height of zirconia crown and comparing different types of zirconia (3 mol% yttria-stabilized zirconia and translucent 5 mol% yttria-stabilized zirconia). Materials and Methods: Six groups of 10 specimens in each group were fabricated. Three groups of specimens (groups # 1, 2, and 3) were fabricated from 3Y zirconia in corresponding heights of 8, 10, and 12 mm. Three more groups (groups # 4, 5, and 6) were fabricated from 5Y zirconia in the same heights (8, 10 and 12 mm). All copings were bonded to 4 mm high titanium base abutments using dual-polymerization resin cement. The specimens underwent load cycling of 100,000 cycles with a force of 100 N. Subsequently, the specimens were loaded to compression until fracture and the failure mode was visually evaluated. Results: Statistically significant differences in fracture strength were noted among all tested groups. Conclusions: 3Y zirconia showed increased strength compared to 5Y in all heights. Ceramic copings with lower height showed increased strength compared to higher copings in both tested zirconia materials. Full article

Background: This study aimed to evaluate the influence of a screw coating on the screw preload and removal torque value (RTV) with and without the application of a cyclic load (CL) to make screws with greater untightening resistance to prevent screw loosening. Methods: Ninety complexes composed of implants, abutments, and prosthetic screws were examined and tested under CL oral conditions (n = 45) and non-CL conditions (nCL, n = 45). Each group was divided into three subgroups (n = 15): a control group (CG) without a screw coating, a GapSeal^®-coated screw group (GG), and a polytetrafluoroethylene (PTFE) tape-wrapped screw group (PG). All screws were tightened at 30 Ncm, and the preload was recorded. In the nCL group, the screws were untightened to record the RTV. In the CL group, the screws were tightened, subjected to a CL in distillated water at a temperature of 37 °C, and then untightened to record the RTV. Micro-Ct analysis was conducted on two samples from each group before CL. SEM analyses of two samples per subgroup before and after CL were also performed. Results: The preload in the PG was significantly lower under nCL (29.92 Ncm) compared with CG (30.95 Ncm) and GG (31.19 Ncm) and also under a CL (PG: 30.92 Ncm) compared with CG (31.72 Ncm) and GG (31.42 Ncm). The RTVs of the PG were significantly lower under nCL (15.30 Ncm) compared with CG (27.98 Ncm) and GG (28.46 Ncm). Under CL, the RTVs of the PG were significantly higher (31.50 Ncm) compared with CG (26.00 Ncm) and GG (27.44 Ncm). Conclusions: Wrapping the screw with PTFE tape significantly reduced the preload but resulted in a significantly greater RTV under CL conditions in the simulated oral environment, suggesting that this could be a solution to decrease the risk of screw loosening. 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

The Cone Morse (CM) implant-abutment junction is designed to improve screw mechanics and minimize bacterial leakage through a process known as “cold fusion”. This research evaluated a clinically stable self-locking CM implant that was retrieved after 30 years of functional loading, focusing on the bone–implant interface. Histological evaluation was conducted to assess the extent of bone-to-implant contact (BIC), identify any tissue reactions, and determine the overall condition of the interface. The analysis revealed a high percentage of BIC in the endosseous portion (56.9%) and at the first contact point (77.4%). Notably, the bone in direct contact with the implant showed healthy integration, indicating no signs of adverse reactions or degradation despite the long duration of functionality. Additionally, osteocyte lacunae were found to be more numerous and larger in the coronal region compared to the apical region. These findings confirmed that the CM implant design sustains a high degree of BIC in humans, even after extended functional loading. The absence of epithelial migration, inflammatory infiltrate, and fibrous tissue at the interface suggests that this type of implant can offer long-term stability and integration. 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 and Objectives: The manufacturing of single crowns using hybrid abutments is an alternative that may be interesting in clinical practice, combining the advantages of the different materials used in a personalized design for each case. The purpose of this in vitro study was to evaluate the torque loss, survival, reliability, failure mode, and strain distribution of implant-supported prostheses with zirconia (Zir) and cobalt–chromium (Co-Cr) hybrid abutments. Materials and Methods: Abutments were milled by CAD/CAM and divided into two groups according to the materials used, Zir and Co-Cr, and cemented on titanium bases screwed to dental implants. Monolithic zirconia crowns were cemented on the abutments. The implant/abutment/crown sets were subjected to thermomechanical cycling (n = 10) (2 Hz, 140 N, 1 × 10⁶ cycles, immersed in water at 5–55 °C) to evaluate the torque loss. The single load to fracture test (SLF) was performed to design the loading profiles (light, moderate, and aggressive) of the step-stress accelerated life testing (SSALT) (n = 21) to evaluate the survival and reliability. The representative fractured specimens were analyzed under optical and scanning electron microscopy. The digital image correlation (DIC) (n = 1) was performed using specimens embedded in polyurethane resin models that received static point loading, and the strain distribution was analyzed. Results: There was no difference in torque loss, survival, or reliability between zirconia and Co-Cr abutments. An analysis of the fractured surfaces showed that the abutments presented the same failure mode, where the fracture probably started in the titanium base/screw. The zirconia abutment model presented only compressive strains around the implant, while the Co-Cr abutment model showed tensile and compressive strains in the middle of the implant; however, all strains were within the clinically acceptable limits. There was a strain concentration in the titanium base close to the implant platform for both groups. Conclusions: Zirconia and Co-Cr hybrid abutments presented similar torque loss, survival, reliability, and failure modes, but the abutment material influenced the strain distribution around the implant. The titanium base screw was the weakest link in the system. Full article

The aim is to investigate the impact of retention type, implant/abutment angulation, and the presence of sealant/antimicrobial agents on screw loosening of implant-supported restorations. Fifty dental implants along with their respective abutments and screws were allocated to five groups (n = 10). The groups were categorized based on type of crown retention (screw-/cement-retained), implant/abutment angulation (0°/20°), and type of disinfectant/sealant as follows: Cem_control (cemented/0°/none), Cem_GP (cemented/0°/gutta-percha), Cem_CHX (cemented/0°/chlorhexidine), Cem_Ang (cemented/20°/none), and Screw (screwed/0°/ none). Abutment screws were tightened (20 Ncm), and CAD/CAM zirconia crowns were fabricated. Glass ionomer cement was used for crown cementation in the cemented groups. Samples were subjected to dynamic loading in a chewing simulator (1,200,000 cycles/98 N). After loading, the reverse torque values (RTVs) of the abutment screws were determined (Ncm) using an electronic screwdriver, and the reverse torque difference (RTD) was subsequently calculated. The lowest RTD was reported in group Cem_GP (−2.22 ± 1.03), whereas the highest RTD was seen in group Screw (−4.65 ± 1.79). Group Screw showed a statistically significant difference from all other groups (p < 0.05). No statistically significant difference between the cemented test groups Cem_GP, Cem_CHX, and Cem_Ang and the control group was found. Screw-retained restorations exhibited significantly greater RTD values compared to cement-retained ones. Implant/abutment angulation and the sealant/disinfectant appeared to have no notable effect on the screw stability of single-implant restorations. 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

Background: The following case report presents the treatment of a patient with severe maxillary atrophy and failing residual dentition. The patient has been diagnosed with stage IV grade C periodontitis, making this case challenging from the very beginning. Methods: The treatment plan was based on collecting and merging digital data: CBCT, a face scan, and an intraoral scan. Due to the advancement of the periodontal disease, the treatment was divided into three stages. The entire process was conducted in a digital manner, based on the concept of prosthetically driven implantology. Additionally, all prosthetic temporaries were planned via digital smile design. Stage I included extracting the residual dentition, placing four implants in the mandible, and the delivery of a 3D-printed upper removable denture. Stage II included placing two zygomatic implants, two anchored piriform rims, and one midline implant. Both arches were immediately loaded with the intraoral welding of abutments screwed to multiunit abutments and 3D-printed shells. Subsequently, in stage III, two milled ceramic superstructures combined with a titanium milled bar were delivered as a final screw-retained restoration with the application of scan flags (horizontal scan bodies) for intraoral scanning. Results: The aforementioned technologies can all be implemented and merged into one complex treatment plan combining high predictability, successful esthetics, and a reliable and accurate end result. Even though the concept of scan flags is relatively new, this case shows its potential and merit. Conclusions: This case represents the power of the digital approach as a helpful tool in the recreation of functional and esthetic smiles in compromised conditions in periodontal patients. Full article