External Hexagon Connection Research Articles

Clinical study with sandblasted dental implants: a 17-year retrospective follow up

Sandblasting is a standard procedure used for treating dental implant (DI) surfaces to enhance the osseointegration with known clinical success. This clinical study aimed to evaluate the long-term clinical outcomes of DIs with external hexagon connections and a surface sandblasted with calcium phosphate. Two hundred and seventy-five Mg-osseous™ (Mozo-Grau™) screw DIs were placed in 86 patients using a two-stage surgical technique and conventional loading protocol (at three months). Dental implants and prosthetic clinical findings were evaluated during a 17-year follow up. Four DIs were lost during the healing period, and 108 prostheses were placed over the 271 DIs left: 58 unitary implant-supported prosthesis (ISP), 31 partially ISP, 14 full-arch ISP, and five overdentures. Fourteen DIs were lost during the follow-up period. Clinical results indicated a DI survival rate of 93.50%. A total of 11.80% of DIs showed peri-implantitis as the primary biological complication. The mean (SD) marginal bone loss was 1.78 (0.40) mm, ranging from 0.90 to 2.80 mm. The most frequent complication was mechanical prosthodontic complications (24.40%). Sandblasted surface DIs inserted in both maxillary and mandibular areas produce favourable long-term (17-year follow up) outcomes and stable tissue conditions when a delayed loading protocol is followed.

Influencia del ácido ascórbico en pruebas biomecánicas deimplantes dentales. Estudio experimental en conejos

Objective: To compare, through biomechanical torque tests and resonance frequency analysis, Oxalife surface titanium implants, without and with vitamin C, placed in rabbit femurs.Methods: 17 Tree-Oss Rapid surface Oxalife implants of 7 mm in length and 3.3 mm in diameter with external hexagon connection were used, placed in the femur of 8 hybrid breed rabbits.Following the drilling sequence indicated by the manufacturer. Insertion torque and resonance frequency analysis were recorded to measure the initial stability coefficient. Euthanasia was performed at 60 days; then the implants were exposed to measure the final or biological stability coefficient through resonance frequency analysis (Osstell) and removal torque (Mark-10 Gauge). The data were subjectedto parametric contrast Student test.Results in Ncm: Mean insertion torque value for the experimental group 16.5 ± 3.7 and for the control group 23.3 ± 4.2, with a significant difference (p<0.01). Mean removal torque for the experimental group 69.3 ± 17.4, and control group 87.2 ± 24.9 without significant differences (p=0.14). Average initial ISQ for the experimental group 40.2 ± 7.8 and for the control group 44.7 ± 6.9 (p=0.24). Final ISQ average for the experimental group 50.8 ± 1.1 and for the control 50.5 ± 2.0 (p=0.77) without differences in both measurements.Conclusion: The addition of vitamin C on the surface of the implant would not have a significant effect regarding the stability values during osseointegration

Biomechanical Analysis of Titanium Dental Implants in the All-on-4 Treatment with Different Implant-Abutment Connections: A Three-Dimensional Finite Element Study.

The type of implant-abutment connection is one of the factors influencing the distribution of occlusal forces. This study aims to investigate the biomechanical performance of the mandibular all-on-4 treatment with different implant-abutment connections. Two connection types with 30° abutments and 18-mm implant fixtures were chosen for the posterior implants of the all-on-4 assembly. For the external hexagon connection (EHC) group, the implants with 4 mm in diameter were used. For the internal hexagon connection (IHC) group, we selected implants with 4.3 mm in diameter. A vertical force of 190 N was applied to the cantilever region. The FEA results indicated that the most stressed region in the two groups was prosthetic screws, followed by multi-unit abutments (MUAs). The lowest values of von Mises stress were both observed on the bone. The peak stress value of the implant screw and implant fixture in the EHC group were 37.75% and 33.03% lower than the IHC group, respectively. For stress distribution patterns, the load force tended to be concentrated at locations where components were interconnected. The EHC and IHC are clinically durable under the tested loading conditions, but the prosthetic screws and MUAs can be the weak point on the posterior implant within the mandibular all-on-four assembly. The peak stress values of implant screw and implant fixture in the EHC groups were lower than the IHC group.

A Nonlinear Three-Dimensional Finite Element Analysis of Stress Distribution and Microstrain Evaluation in Short Dental Implants with Three Different Implant-Abutment Connections in Single and Splinted Conditions in the Posterior Mandible.

Stress distribution plays a vital role in the longevity and success of implant-supported prosthesis. This study evaluated the von Mises stress and microstrain in the peri-implant bone and the implant-abutment junction of short dental implants with three different implant-abutment connections in splinted and unsplinted conditions using finite element analysis (FEA). In this experimental study, nine transversely isotropic finite element models were developed, and randomly divided into three equal groups (n = 3): control, (Group AC) single-standard 4.3 × 10 mm bone level implant-supported restorations with external hexagonal (EH) connection, internal conical (IC) and internal trichannel (ITC) connection, single short implant-supported restorations (Group AT), and splinted short implant-supported restorations (Group B) for each of the three implant-abutment connections, respectively. A 200 N load was applied along the long axis of the implants and a 100 N (45°) oblique load was applied and von Mises stress and microstrain values were evaluated. Single standard implants demonstrated the highest von Mises stress and microstrain values followed by single short implants and splinted short implants, respectively. Among the implant-abutment connections, the IC connection showed the highest values and the ITC connection showed the least values. Within the limitations of this study, it was concluded that splinting of short dental implants demonstrated lesser and more homogeneous stress and microstrain, especially on oblique loading. The microstrain values for all connections evaluated were within the physiological loading limit (200-2,500 N) and were hence considered safe for clinical use.

Bacterial Detection, Deformation, and Torque Loss on Dental Implants with Different Tapered Connections Compared with External Hexagon Connection after Thermomechanical Cycling.

The relationship between bacterial infiltration and internal conical Implant-Abutment Interfaces (IAIs) with different conicities still requires investigations that can offer valuable information in the clinical understanding of peri-implant health. The present study aimed to verify the bacterial infiltration of two internal conical connections with an angulation of 11.5° and 16° with the external hexagonal connection as a comparative after thermomechanical cycling using saliva as a contaminant. Test (n = 10) and control (n = 3) groups were set up. Evaluations were made on torque loss, Scanning Electron Microscopy (SEM), and Micro Computerized Tomography (MicroCT) after performing 2 × 106 mechanical cycles (120 N) and 600 thermal cycles (5°-55° C) with 2 mm lateral displacement. The contents of the IAI were collected for microbiological analysis. There was a difference (p < 0.05) in torque loss of the groups tested; groups from the 16° IAI obtained a lower percentage of torque loss. All groups presented contamination and the analysis of the results shows that the microbiological profile of the IAI differs qualitatively from the profile found in the saliva used for contamination. The mechanical loading affects the microbiological profile found in the IAIs (p < 0.05). In conclusion, the IAI environment may favor a microbiological profile different from that of saliva and the thermocycling condition may alter the microbial profile found in the IAI.

Anaerobic adhesives effect on counter-torque of abutment screws on implants with external hexagon and conical connections: An in vitro study.

Abutment screw loosening is a common complication of implant supported prostheses, especially for single crowns. In engineering, anaerobic adhesives (AA) are used to provide chemical locking between screw surfaces, but their application in implantology remains unclear. The purpose of this article is to evaluate, in vitro, the effect of AA on counter-torque of abutment screws for cemented prosthesis on dental implants with external hexagon connection (EHC) and conical connection (CC). Sample was composed by 60 specimens, 30 dental implants with EHC and 30 with CC. Abutments (transmucosal 3 mm straight universal abutment) were installed without AA (control group) or with application of AA with two different adhesive strength: medium strength (LOCTITE® 242) and high strength (LOCTITE® 277). The specimens were subjected to mechanical cycling at 37°C, with a load setting of 133 N, a 1.3 Hz frequency, and 1 200 000 cycles. The abutments were removed, and the counter-torque values were registered. Screws and implants were inspected using a stereomicroscope to verify the presence of residual adhesive and damage the internal structures. The data were analyzed using descriptive statistics and comparison tests (p < 0.05). Comparing to the torque of installation, the medium strength AA kept the counter-torque values for CC implants and the high strength AA kept the counter-torque for EHC implants and increased for CC implants. In the intergroup comparisons, control group presented significantly lower counter-torque values than other groups, both for EHC and CC implants. High strength AA presented similar results to medium strength AA in the EHC implants, but in the CC implants presented higher counter-torque values. Damage in threads was more frequent in the groups that received high strength AA. The use of AA increased the counter-torque of abutment screws, both in implants with EHC and CC.

Comparative analysis of the mechanical limits of resistance in implant/abutment set of a new implant design: An in vitro study.

The aim of the present in vitro study was to evaluate the resistance on quasi-static forces and in the fatigue mechanical cycling of a new implant design compared to two other conventional implant designs. Eighty-eight implants with their respective abutments were tested and distributed into four groups (n = 22 per group): Morse taper connection implant (MT group), conventional external hexagon implant (EH con group), new Collo implant of external hexagon with the smooth portion out of the bone insertion (EH out group), and new Collo implant of external hexagon with the implant platform inserted to the bone level (EH bl group). All the sets were subjected to quasi-static loading in a universal testing machine, and we measured the maximum resistance force supported by each sample. Another 12 samples from each group were submitted to the cyclic fatigue test at 4 intensities of forces (n = 3 per force): 80%, 60%, 40%, and 20%. The number of cycles supported by each sample at each force intensity was evaluated. The three groups of implants with external hexagon connection had similar maximum strength values of the sets (p > 0.05). Meanwhile, samples from the MT group showed the highest resistance values in comparison to the other three groups (p < 0.05). In the fatigue test, the Collo out group supported a smaller number of cycles that led to the fracture than the other 3 groups proposed at loads of 80%, 60%, and 40%, and only at the load value of 20% all groups had the same performance. Within the limitations of the present in vitro study, the results showed that the new Collo implant performs better when installed at bone level.

Influence of Platform-Switched Restoration on Bone Resorption in Patients Treated with Wide-Diameter, External-Hex-Connection Dental Implants: A 10-Year Follow-up Study.

Purpose: To investigate and assess the differences in crestal bone loss (CBL) between wide-diameter, external-hexagon-connection implants restored with platform-switching (PS) and platform-matching (PM) restorations with a follow-up of 10 years. Materials and Methods: This study retrospectively analyzed the updated and enlarged dataset of a 5-year prospective clinical study at 10-year follow-up. The data concerns 182 healthy adult subjects treated in a private dental practice who received a single wide-diameter implant with an external hexagon connection in the molar area, restored with either a PS restoration (test) or PM restoration (control). The amount of CBL was radiographically measured at each annual follow-up, as well as after 5 and 10 years of implant loading. In evaluating the association between the two types of abutments and bone loss (including change over time), a linear mixed effects model was run for longitudinal data. Results: Implants connected with PS restorations exhibited significantly lower reduction (0.25 mm) in CBL than those joined to PM restorations (P < .001; 95% CI from 0.22 to 0.29). However, both groups presented a higher increase in bone loss during the first year (0.58 mm in PS and 0.83 mm in PM) and a linear increment thereafter until the 10-year follow-up (0.046 mm/year; P < .001; 95% CI from .042 to .049). Conclusion: Notwithstanding the limitations of this study, it can be concluded that after 10 years of follow-up, the implant with a wide diameter and external-hexagon connection restored with a PS abutment seems to be more effective in reducing bone loss compared with the PM abutment.

An in vitro evaluation of 2 methods for retrieving fractured abutment screw fragments from the intaglio of 4 different implant systems

Statement of problemWhen an abutment screw fractures, there is no standardized technique for retrieving it from the intaglio of the dental implant. PurposeThe purpose of this in vitro study was to assess the relative efficacy of a commercially available screw fragment retrieval kit with a range of standard dental instruments in regard to success and retrieval time. In addition, the effects of other variables on the success rate of screw fragment retrieval and the retrieval time required were also investigated. Finally, the integrity of the intaglio screw channel of the dental implant was also assessed following retrieval. Material and methodsThe abutment screws from 4 dental implant systems: Osseotite Certain, Ø4.1 mm (Zimmer Biomet); Osseotite External hexagonal connection micromini, Ø3.25 mm (Zimmer Biomet); Standard Plus Tissue Level, Ø4.8 mm (Institut Straumann AG); and Brånemark Mark III TiUnite, Ø4.1 mm (Nobel Biocare) had notches placed between the first and second coronal threads before being placed in their respective abutments, positioned in the dental implants (n=128), and tightened until the screws fractured. The dental implant specimens were placed in maxillary and mandibular casts at the lateral incisor and first molar sites on both sides. The casts were placed in mannequin heads on a dental chair and assigned to 2 experienced and 2 inexperienced operators who used 2 different retrieval kits to retrieve the screw fragments.Chisquared tests were used to determine the association between the success rate of screw fragment retrieval and the other factors recorded (α=.05), and a binary logistic regression was used to determine the association between the retrieval event and all of the independent variables. Regression models were developed to determine the factors effecting retrieval time. ResultsAn overall success rate of 88.3% was achieved for screw fragment retrieval. No statistically significant difference (P>.999) was found in the relative efficacy of the retrieval kits. Univariate analysis identified a statistically significant association (P<.01) in the success of abutment screw fragment retrieval between the Osseotite Certain and the Osseotite External hexagonal connection micromini implant systems. Gamma regression analysis identified significant differences between the time taken to retrieve the screw fragments and the type of dental implant (P<.001), (P<.01). The time taken to retrieve screw fragments in the maxillary arch was significantly longer than for the mandibular arch (P<.05). ConclusionsThe commercially available screw fragment retrieval kit and the standard dental instruments were equally effective in retrieving the screw fragments. Less time was required to retrieve screw fragments in the mandibular arch than the maxillary arch. The level of experience of the operator had no effect on the ability to successfully retrieve fractured abutment screws.

Effects of Marginal Bone Loss Progression on Stress Distribution in Different Implant–Abutment Connections and Abutment Materials: A 3D Finite Element Analysis Study

Peri-implantitis is a common implant-supported prosthesis complication, and marginal bone loss affects the stress distribution in implant systems. This three-dimensional finite element analysis study investigated how bone loss affects the implant assembly; in particular, models including two implant systems with different connection systems (external or internal hexagon), abutment materials (titanium or zirconia), and bone loss levels (0, 1.5, 3, or 5 mm) were created. We observed that the maximum von Mises stress distinctly increased in the groups with bone loss over 1.5 mm compared to the group without bone loss, regardless of the connection system or abutment material used. Moreover, the screw stress patterns with bone loss progression were determined more by the connection systems than by the abutment materials, and the magnitude of the stress on the fixture was affected by the connection systems with a similar pattern. The highest stress on the screw with the external hexagon connection system increased over 25% when bone loss increased from 3 to 5 mm, exceeding the yield strength of the titanium alloy (Ti–6Al–4V) when 5 mm bone loss exists; clinically, this situation may result in screw loosening or fracture. The highest stress on the fixture, exceeding the yield strength of pure titanium, was noted with the internal hexagon connection system and 1.5 mm bone loss. Titanium and zirconia abutments—both of which are clinically durable—presented similar screw and fixture stress patterns. Therefore, clinicians should pay more attention to maintaining the peri-implant bone to achieve the long-term stability of the implant-supported prosthesis.

The effect of implantoplasty on dental implant fracture resistance: a systematic review

An increase in dental implant placements in recent years has seen a growth in the reported cases of post-operative complications such as peri-implantitis. One of the available treatment modalities to overcome such complications is implantoplasty. Although this procedure is not new, the long-term effect of implantoplasty has not been addressed extensively. The aim of this systematic review was to investigate the change in fracture resistance of dental implants after implantoplasty. Three electronic databases and reference lists of included studies were searched to assess the potential effect of implantoplasty on implant fracture resistance. Titles and abstracts were screened by two reviewers in parallel. The extracted information regarding implant fracture resistance was reported based on the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. A total of 56 studies were identified, of which, nine studies were included. Narrow platform implants (&lt;3.75 mm) were more susceptible to fracture following implantoplasty compared to wider platforms (?5 mm). Implants with internal hexagon connection may have a higher risk of fracture after implantoplasty compared to other connection designs such as external hexagon and conical connections. Other potential factors which may affect implant fracture resistance after implantoplasty include crown to implant ratio, implant material, and the amount of peri-implant bone loss. Within the limitation of in vitro studies, there is no clear evidence to demonstrate the effect of implantoplasty on implant fracture resistance. Methodological differences between the available studies did not allow for clear comparison between them. Furthermore, the limited amount of clinical reports of this resective procedure, in combination with patient and operator variability, affect the clinical assessment of this treatment modality.

Management of Fixed Rehabilitation of Single Implants in the Aesthetic Sector: A Systematic Review

Introduction When dental implants are installed and subjected to functional loads, marginal bone resorption is frequent, also in sites not affected by peri-implantitis, and it can be a critical factor that will affect the aesthetics and longevity of the implant because it is associated with an increased risk of peri-implantitis and soft tissue collapse. Objective To assess the peri-implant marginal bone loss and the survival percentage of implant restorations that present internal and external prosthetic connections. Material and methods A systematic review of the literature was carried out. Various information sources were consulted such as PubMed, Embase, Ovid, Scopus databases. For the search process, the methodology approved by the PRISMA Guide was followed. Results 5 articles were found that met the established criteria. In these articles, 2,866 patients rehabilitated by means of 6,455 implants were registered, of which 3,057 were restored with an external hexagonal prosthetic connection and 3,398 with an internal connection of the hexagonal or conometric type. The 3,057 implants prosthetized by connection to an external hexagon showed a mean peri-implant marginal bone loss of 0.986 ± 0.58mm. The 3,398 implants prosthetized by means of an internal hexagon or conometric type connection highlighted a mean peri-implant marginal bone loss of 0.86 + - 0.43mm. Conclusion Taking into consideration the individual characteristics of each patient and each situation, the literature seems to indicate that on the intensity of the mechanical stress and the tensions emitted to the peri-implant region, the conical connection and the cylindrical design of the implant transmit less stress to the cortical bone. Bone with respect to the external hexagonal connection and the conical design of the implant, which transmit less stress and tension to the trabecular bone and more to the cortical bone.

Screw removal torque evaluation in implants with cone morse and external hexagon platforms in anterior cantilever

This study aims to evaluate the screw removal torque on prosthetic platforms of Cone Morse (CM) and External Hexagon (EH) implants in crowns with anterior cantilever. Materials and Methods: in vitro study with a sample consisting of 20 test specimens of 2 elements (21 and 22), with n = 40; load is simulated on element 21 or on cantilever of 22. Samples were divided into 4 groups consisting of 10 test specimens on CM implants (groups 1 and 2), and 10 test specimens on EH implants (groups 3 and 4). The test specimens were manufactured using cylindrical PVC pipes measuring 22 x 19.05 mm filled with acrylic resin. The implants were fixed with a centralization device. Components used were EUCLAs and UCLAs with a chrome-cobalt alloy molten base. The metal bases were scanned, the crowns were digitally waxed, made on CAD/CAM system, and cemented on the metal bases with Panavia cement. Torque was applied using 20N for CM and 32N for EH, according to the manufacturers’ instructions. The test specimens were then subjected to a cycling process consisting of 1,000,000 cycles at a frequency of 2 Hz. The cyclic process applied axial forces to the surface (palate face of 21 and 22). Two cycling processes were carried on, the first on the palate face of 21 and the second on the palate face of 22. Between the two, screws were removed and replaced by new ones. The screw removal torque was measured using a digital torque meter. Results were analyzed with Student’s t test and variance analysis. Statistical calculations were conducted in SPSS 23 using 5% of significance. Results: Student’s t test showed significantly lower removal torque values in comparison with initial torque for both CM and EH connection implants and force applied to elements 21 and 22 (p &lt; 0.001) or 22 (p &lt; 0.001). Considering torque loss, there was no significant effect of the interaction between type of implant connection and site of force application (p = 0.094). Removal torque was significantly lower than initial torque for both implants (CM and EH). Conclusion: Torque loss occurred both in CM and EH. There was no significant effect of the interaction between connections and site of force application.

A temporospatial histomorphometric analysis of bone density adjacent to acid-etched self-tapping dental implants with an external hexagon connection in the female baboon.

To characterize osseointegration as the percent of bone-implant contact (%BIC) along the surface (0.0mm) as well as at surface profiles 0.5mm and 1.0mm lateral to the implant, determining any differences between early occlusally loaded and non-loaded implants. In ten adult female baboons, 120 dental implants were randomly placed in opposing mandibular and maxillary locations. Eighty sites had two groups of healing (no load) of either 1 (n = 40) or 2 (n = 40) months leading to 3months of functional loading. These sites received full acid-etched surface implants. The 40 control implants represented healing only periods (no load) for 1 (n = 10), 2 (n = 10), 4 (n = 10), and 5 (n = 10) months. These implants were of a vertically split surface texture design (acid-etched and machined). Block sections and photomicrographs were obtained. Blinded histometric analyses determined the %BIC via a superimposed template. The unloaded groups (1, 2, and 4months) had higher %BIC compared to the 5-month group (p < 0.0001). The loaded groups exhibited mean bone densities of 59.2% and 55.5% (1-month healing at 0.5mm and 1.0mm, respectively) and 61.0% and 57.1% (2-month healing at 0.5mm and 1.0mm, respectively) with no significant difference between healing time (p = 0.4118). There was a lateral increase in %BIC in the loaded compared to unloaded groups. The decrease in bone densities at the 5-month unloaded group suggests that there is a critical earlier time period when dental implants should be placed into functional load.

Evaluation of internal and external hexagon connections in immediately loaded full-arch rehabilitations: A within-person randomized split-mouth controlled trial with a 3-year follow-up.

BackgroundAlthough full‐arch immediately loaded rehabilitations are widely used nowadays, little information is available on which implant/abutment connection is the most suitable in this type of treatment.PurposeThe aim of the present multicentric split‐mouth clinical trial was to compare the clinical outcomes of two different implant‐abutment connections applied in full‐arch immediate loading rehabilitations: external hexagon connection (EHC) versus internal hexagon connection (IHC).Materials and methodsTwenty patients were rehabilitated with immediately loaded fixed full‐arch rehabilitations. All the implants presented the same macro‐ and micro‐topography but different implant/abutment connection. IHC were used in one randomly selected side of the jaw and EHC in the other side.Outcome measures were implant survival rate, peri‐implant marginal bone loss (MBL), plaque index (PI), probing depth (PD), and bleeding on probing (BoP) evaluated at 3, 6, 12, and 36‐month post‐loading. Any technical and biological complication was recorded. Kaplan–Meier procedure and linear mixed model were used to perform statistical analysis.ResultsForty‐three EHC and 40 IHC implants were inserted. No patients dropped out and two implants failed in the first 6 months. The CSR was 97.7% for EHC and 97.5% for IHC implants. No statistically significant differences were found among the two groups for any of the parameters at any time point. At the 36‐month follow‐up visit a slight difference was found in MBL with a mean value of 1.7 mm in the EHC and of 1.9 mm in the IHC group (p = 0.355).No biologic complications were identified. Seven loosed abutment screws were identified in the entire follow‐up period, two in the EHC, and five in the IHC group without a statistically significant difference (p = 0.394).ConclusionsAfter 36 months in function, both internal and external hexagon connections provided good clinical outcomes and were not associated with any significant difference.

Influence of Implant-Abutment Contact Surfaces and Prosthetic Screw Tightening on the Stress Concentration, Fatigue Life and Microgap Formation: A Finite Element Analysis

The purpose of this in silico study was to investigate the effect of abutment screw torque and implant-abutment contact surfaces on the stress generation, microgap formation and simulated fatigue life of an external hexagon connection under oblique loading. Three-dimensional numerical models of the external hexagon implant were modeled containing two different implant-abutment contact surfaces (with and without contacting the hexagon axial walls) as well as using screw torques of 20 Ncm or 30 Ncm. Following the ISO 14801, an oblique load of 100 N was applied to the prosthesis. The von Mises stress, microgap formation, safety factor and fatigue life were obtained. The stresses in the abutment screw and implant were minimally influenced by the screw torque. However, this minimal stress in the screw with a 30 Ncm torque reduced the calculated fatigue life in comparison with 20 Ncm when the external hexagon axial walls were not in contact at the implant-abutment interface. The safety factor for the implant was higher when using minimal surfaces at the abutment-interfaces; however, it compromised the screw safety factor increasing its failure probability. The higher the screw torque, the lower was the microgap formation at the implant-abutment interface. However, the calculated residual stress is proportional to the applied torque, reducing the fatigue life in the screw. This effect can be attenuated using an implant-abutment system with more contacting surfaces.

New Generation of Fixture-Abutment Connection Combining Soft Tissue Design and Vertical Screw-Retained Restoration: 1-Year Clinical, Aesthetics and Radiographic Preliminary Evaluation.

Implant design factors and the abutment connection are correlated with crestal bone stability. The aim of the present study was to evaluate a new type of screw-retained prostheses delivered on tissue-level implants with conical external vertical seal and internal hexagon connection. Implants 4.25 mm in diameter and 10 mm in length (Prama, Sweden and Martina) were placed in partially edentulous patients needing at least one implant in the healed site, having sufficient bone volume. The implant neck was positioned above the bone crest. A healing abutment was placed according to a one-stage approach. Outcome measures were implant and prosthesis survival rate, any complications, marginal bone loss (MBL), periodontal parameters, and pink esthetic score (PES). Overall, 13 patients (4 women and 9 men; mean age 50 ± 22 years) with the same number of implants were treated and followed for one year after loading. At the 12-month follow up, no implant and no prosthesis failed, and no complications were experienced. The mean MBL experienced at the one year follow-up was 0.65 ± 0.48 mm. One year after loading, 2 out of 13 implants present bleeding on probing (15.4%), 4 out of 13 patients presented with plaque at the one year of follow-up (30.8%) and the PES was 10.5 ± 2.3 mm. Within the limitations of the present study, the analyzed implants seem to be a viable treatment option for the rehabilitation of a single tooth gap.

Effect of Different Retightening Procedures on Screw Stability in External-Hex and Internal Trichannel Connections: An In Vitro Study.

To evaluate the effect of different abutment screw retightening procedures on the screw stability between the abutment and implant. External hexagon connection (EHC) and internal trichannel connection (ITC) implants were employed in this study. Each abutment screw was used for the following specific applications (n = 5 for each group): group 0 = abutment was tightened and retightened with a 10-minute interval; group 1 = abutment was tightened and retightened with a 10-minute interval, then loaded for 500,000 cycles; group 2 = abutment was loaded for 83,000 cycles during tightening and retightening, then loaded for 500,000 cycles; group 3 = abutment was loaded for 167,000 cycles during tightening and retightening, then loaded for 500,000 cycles; and group 4 = abutment was loaded for 250,000 cycles during tightening and retightening, then loaded for 500,000 cycles. Both tightening and retightening torques were set at 35 Ncm, and dynamic oblique loading between 0 N and 200 N was applied on the abutment in all groups. The settling values of the abutments after retightening and the abutment removal torque values (RTVs) after testing were measured. No significant differences in settling values were found between EHC and ITC. There were significant differences in the RTVs of EHC implants, but ITC implants showed no difference in RTV with different prosthetic retightening applications. The retightening application affected the joint stability of EHC implants but did not affect the settlement and joint stability of ITC implants. Int J Prosthodont 2023;36:181-188. doi: 10.11607/ijp.6863.

Mechanical testing of four-unit implant-supported prostheses with extensive pink gingiva porcelain: The dentogingival prostheses proof of concept.

To investigate the probability of survival and failure modes of four-unit implant-supported porcelain fused to metal (PFM) dentogingival prostheses subjected to step-stress accelerated life testing (SSALT). Eighteen implant-supported PFM dentogingival prostheses with thin metallic infrastructures, which provided minimal ceramic support and improved esthetics were fabricated over external hexagonal connection UCLA abutments. SSALT was performed until specimen failure. Use level probability Weibull curve and reliability were calculated and plotted. Weibull modulus (m) and characteristic strength (η) were also calculated. Polarized light microscope and scanning electron microscope were used to characterize fractures. Failures were dictated by material strength rather than fatigue damage accumulation. The probability of survival for loads reaching 100 and 150 N in 100,000 cycles was 92 and 61%, respectively. No cracks or fractures were identified in the veneered porcelain, whereas abutment fixation screw fracture was the chief failure mode. Implant-supported PFM four-unit dentogingival prostheses with minimum metal framework dimensions presented favorable lifetime prediction under fatigue testing. Fractures were restricted to fixation screws. In-vitro fatigue testing and failure mode analyses evidenced favorable lifetime prediction for 4-unit implant-supported dentogingival prostheses with minimum metal frameworks. Abutment fixation screw fracture might be the most frequent clinical complication. Since this proof of concept has been tested in-vitro, further studies including different restorative materials, as well as long-term clinical trials are warranted.

Implantoplasty: Carbide burs vs diamond sonic tips. An in vitro study

Implantoplasty (IP) is a treatment option for peri-implantitis. Mechanical concerns were raised on fracture resistance of implants subjected to this procedure. This study aimed to compare two methods of IP in terms of implant wear and fracture resistance, and of surface topography. Eighteen cylindrical screw-shaped dental implants (4mm diameter, 13mm length) with an external hexagonal connection were used. IP was performed on the first 6-mm implant surface with a sequence of burs or diamond sonic tips, both followed by an Arkansas finishing. IP duration and implant weight variation were recorded. Micro-computed tomography (micro-CT) was used to evaluate material loss. Implant fracture resistance was assessed by static compression test. Surface topography analysis was performed with a stylus profilometer. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) was applied for implant surface morphology and elemental characterization. Micro-CT showed less material loss in sonic compared to burs. No statistically significant difference was found between the mean fracture resistance values reached in bur and sonic, both followed by Arkansas, and with respect to control. IP performed with burs led to a smoother surface compared to sonic. Equivalent final surface roughness was found after Arkansas in both IP procedures. SEM-EDS showed a deburring effect associated to sonic and revealed carbon and aluminum peaks attributable to contamination with sonic diamond tips and Arkansas bur, respectively. IP with sonic diamond tips was found to be more conservative in terms of structure loss. This could have a clinical relevance in case of narrow-diameter implants.