Maxillary and mandibular overdentures retained by two unsplinted narrow-diameter titanium-zirconium implants - A clinical pilot study.

OBJECTIVES: To evaluate the survival rates and marginal bone loss of narrow-diameter titanium-zirconium implants supporting complete maxillary and mandibular overdentures up to 3 years after loading. MATERIALS AND METHODS: Ten completely edentulous patients who were dissatisfied with their complete dentures were enrolled. Two narrow-diameter implants were placed in the canine region of the maxilla and mandible. After second-stage surgery, implant-supported overdentures (palatal-free) attached by parallel alignable stud-attachments were placed. Patients were followed periodically for up to 36 months. Standardized radiographs were taken at baseline, 12 and 36 months to analyze mean marginal bone level changes around the implants. RESULTS: The Kaplan-Meier survival rates were 100% for mandibular and 68.0% (SE ± 10.9%) for maxillary implants at 36 months (p = .008). Six maxillary implants failed after loading; no mandibular implants were lost. Five implants failed due to loss of osseointegration. One implant fractured. The mean marginal bone level changes around the analyzed implants (n = 28, 9 patients) were -0.71 ± 0.82 mm in the mandible and -2.08 ± 1.52 mm in the maxilla at the 36-month follow-up. The difference in marginal bone level changes between the maxilla and mandible was significant (p = .019) at the 12- and 36-month follow-ups. CONCLUSION: Two narrow-diameter titanium-zirconium implants with stud-attachments showed a highly satisfactory outcome in the mandible. The maxillary implants showed a high failure rate and significantly more bone loss over time than the mandibular implants. The minimal concept of two implants and an overdenture should be limited to the edentulous mandible.

In vitro assessment of cementation of CAD/CAM fabricated prostheses over titanium bases. A systematic review.

OBJECTIVES: The objective of this study is to investigate the outcomes of clinically relevant laboratory studies regarding the cementation of implant-supported restorations over ti-bases. MATERIALS AND METHODS: The present study has been conducted according to PRISMA statement. An electronic search was performed, including publications up to March 2024, to identify studies investigating the parameters affecting the cementation between ti-bases and CAD/CAM prostheses. An assessment of the internal validity was performed, using a custom-made risk of bias tool (QUIN). RESULTS: From the included studies, 40.1% were reported on luting systems, 25% on ti-base surface treatment, 25% on restoration surface, 21.8% on restoration material, and 18.7% on ti-base height. The majority of the included studies were associated with a medium risk of bias. In the absence of micro-retentive features, air-abrasion of ti-bases with a minimum height of 3.5 mm can be beneficial for restoration's retention. The bonding performance can vary not only between different bonding systems but also for different applications within the same system, based on a restoration's material and surface treatment as well as on ti-base height and surface treatment. CONCLUSIONS: The height of the ti-base seems to be the prevailing factor as it constitutes the prerequisite for other modifications of the bonding surfaces to have an advantageous effect. Since the parameters that can affect bonding performance between ti-base and restoration can interact with each other, it is important for the clinician to focus on verified bonding protocols.

An overview of artificial intelligence based applications for assisting digital data acquisition and implant planning procedures.

OBJECTIVES: To provide an overview of the current artificial intelligence (AI) based applications for assisting digital data acquisition and implant planning procedures. OVERVIEW: A review of the main AI-based applications integrated into digital data acquisitions technologies (facial scanners (FS), intraoral scanners (IOSs), cone beam computed tomography (CBCT) devices, and jaw trackers) and computer-aided static implant planning programs are provided. CONCLUSIONS: The main AI-based application integrated in some FS's programs involves the automatic alignment of facial and intraoral scans for virtual patient integration. The AI-based applications integrated into IOSs programs include scan cleaning, assist scanning, and automatic alignment between the implant scan body with its corresponding CAD object while scanning. The more frequently AI-based applications integrated into the programs of CBCT units involve positioning assistant, noise and artifacts reduction, structures identification and segmentation, airway analysis, and alignment of facial, intraoral, and CBCT scans. Some computer-aided static implant planning programs include patient's digital files, identification, labeling, and segmentation of anatomical structures, mandibular nerve tracing, automatic implant placement, and surgical implant guide design.

A retrospective study of occlusal reconstruction in patients with old jaw fractures and dentition defects.

PURPOSE: This study evaluated the methods and clinical effects of multidisciplinary collaborative treatment for occlusal reconstruction in patients with old jaw fractures and dentition defects. METHODS: Patients with old jaw fractures and dentition defects who underwent occlusal reconstruction at the Third Affiliated Hospital of Air Force Military Medical University from January 2018 to December 2022 were enrolled. Clinical treatment was classified into 3 phases. In phase I, techniques such as orthognathic surgery, microsurgery, and distraction osteogenesis were employed to reconstruct the correct 3-dimensional (3D) jaw position relationship. In phase II, bone augmentation and soft tissue management techniques were utilized to address insufficient alveolar bone mass and poor gingival soft tissue conditions. In phase III, implant-supported overdentures or fixed dentures were used for occlusal reconstruction. A summary of treatment methods, clinical efficacy evaluation, comparative analysis of imageological examinations, and satisfaction questionnaire survey were utilized to evaluate the therapeutic efficacy in patients with traumatic old jaw fractures and dentition defects. All data are summarized using the arithmetic mean ± standard deviation and compared using independent sample t-tests. RESULTS: In 15 patients with old jaw fractures and dentition defects (an average age of 32 years, ranging from 18 to 53 years), there were 7 cases of malocclusion of single maxillary fracture, 6 of malocclusion of single mandible fracture, and 2 of malocclusion of both maxillary and mandible fractures. There were 5 patients with single maxillary dentition defects, 2 with single mandibular dentition defects, and 8 with both maxillary and mandibular dentition defects. To reconstruct the correct 3D jaw positional relationship, 5 patients underwent Le Fort I osteotomy of the maxilla, 3 underwent bilateral sagittal split ramus osteotomy of the mandible, 4 underwent open reduction and internal fixation for old jaw fractures, 3 underwent temporomandibular joint surgery, and 4 underwent distraction osteogenesis. All patients underwent jawbone augmentation, of whom 4 patients underwent a free composite vascularized bone flap (26.66%) and the remaining patients underwent local alveolar bone augmentation. Free gingival graft and connective tissue graft were the main methods for soft tissue augmentation (73.33%). The 15 patients received 81 implants, of whom 11 patients received implant-supported fixed dentures and 4 received implant-supported removable dentures. The survival rate of all implants was 93.82%. The final imageological examination of 15 patients confirmed that the malocclusion was corrected, and the clinical treatment ultimately achieved occlusal function reconstruction. The patient satisfaction questionnaire survey showed that they were satisfied with the efficacy, phonetics, aesthetics, and comfort after treatment. CONCLUSION: Occlusal reconstruction of old jaw fractures and dentition defects requires a phased sequential comprehensive treatment, consisting of 3D spatial jaw correction, alveolar bone augmentation and soft tissue augmentation, and implant-supported occlusal reconstruction, achieving satisfactory clinical therapeutic efficacy.

The distribution of marginal excess cement of implant-supported vented and non-vented zirconia crowns with and without cleaning procedures.

PURPOSE: To investigate the distribution of marginal excess cement in vented and non-vented crowns and evaluate the effect of clinical cleaning procedures on the reduction of excess cement. MATERIALS AND METHODS: Forty models with implant analogs in the position of the right maxillary first molar were divided into four groups (n = 10/group, vented/non-vented crowns with or without cleaning procedures). The abutment finish lines were placed 1 mm below the artificial gingiva buccally, mesially, and distally and at the gingival level palatally. A standardized amount (20 mg) of resin cement was applied in a thin layer to the intaglio surface of zirconia vented and non-vented crowns. The excess cement was removed by a dental explorer in groups with cleaning procedures. The distribution (area and depth) of the marginal excess cement was measured at each quadrant (buccal, mesial, palatal, and distal) for all study samples. The data were analyzed using descriptive and analytical statistics (ɑ = 0.05). RESULTS: The area and depth values of the excess cement in each quadrant in the vented group were significantly smaller than that in the non-vented group, both with and without cleaning (p < 0.001). Cleaning procedures significantly reduced the area of excess cement in both vented and non-vented groups (all, p < 0.001 except for p < 0.05 at the buccal aspect of the vented group). The depth of excess cement in the vented group was significantly decreased with cleaning in the buccal quadrant compared with that without cleaning (p < 0.01). However, the depth of excess cement of the non-vented group was significantly increased with cleaning in all quadrants compared with that without cleaning (all, p < 0.001 except for p < 0.05 at the distal aspect). CONCLUSIONS: Crown venting significantly reduced the area and depth of the marginal excess cement in vitro. Cleaning procedure with a dental explorer significantly reduced the area of marginal excess cement in vitro; however, the excess cement can be pushed deeper in the non-vented group.

Technique for cementing screwmentable implant crowns to prevent misalignment.

The purpose of this article is to describe a technique to accurately cement implant crowns on an abutment extraorally and prevent misalignment that might change the desired position of the crown on the abutment when delivered. An implant-retained crown was tried-in and occlusal and interproximal contacts were adjusted for delivery. The cementation verification aid was fabricated using a polyvinylsiloxane bite registration material (Blu Mousse) to cement the crown onto the abutment extraorally to ensure proper alignment of the crown on the abutment. Cementation of the prosthesis occurred with no adjustments required to the interproximal or occlusal contacts during final delivery. This article provides a technique that aims to increase accuracy in the placement of the crown on the abutment when cementing screwmentable crowns.

Impact of color temperature and illuminance of ambient light conditions on the accuracy of complete-arch digital implant scans.

OBJECTIVE: The purpose of the present study was to assess the influence of color temperature and illuminance of ambient light on the accuracy of different intraoral scanners (IOSs) in complete-arch implant scans. METHODS: An edentulous model with six implants and scan bodies was digitized by using a laboratory scanner (DW-7-140; Dental Wings) to obtain a reference mesh. Fifteen scans were performed employing two intraoral scanners (Trios 4;3Shape A/S and i700; Medit Co) at two illuminances (500 and 1000 lux) and three color temperatures (3200, 4400, and 5600 K). Scanning accuracy was measured by using a 3D metrology software program (Geomagic Control X). Kruskal-Wallis, one-way ANOVA, and pairwise comparison tests were used to analyze the data (α = .05). RESULTS: Significant differences in trueness and precision values were found among the different IOSs under the same ambient lighting condition and among the different lighting conditions for a given IOS (p < .05) except for trueness in i700 groups (p > .05). CONCLUSIONS: The influence on the accuracy of color temperature and illuminance varied depending on the intraoral scanner. An optimal ambient scanning light condition was not found; this should be adjusted based on the specific IOS system used. 3200 K of ambient light influences the precision of i700 when performed at 1000 lux, decreasing the accuracy. The variation of color temperature at the same illuminance does not affect the scanning accuracy of TRIOS 4, which obtained better accuracy in all scans at 1000 lux.

Printed abutment model to limit residual cement: A dental technique.

Preventing retained cement around implant-retained crowns is crucial for the long-term health and success of the implant. Residual subgingival cement is strongly associated with peri-mucositis and can lead to peri-implantitis. This clinical technique utilizes a 3D printed model of a custom abutment to seat the implant crown on before cementing intra-orally to extrude excess cement. The technique aims to limit the amount of retained cement at the crown-abutment margin and also takes into consideration the cement space already designed into the crown-abutment complex.

Effect of Vent Hole and Cement Type on Fracture Resistance of CAD-CAM Monolithic Zirconia Crowns.

PURPOSE: To assess the fracture resistance of monolithic zirconia crowns cemented with different types of cement on cement-retained implant abutments. MATERIALS AND METHODS: Forty implant analogs were positioned in acrylic resin blocks, and cement-retained straight implant abutments were fastened to the analogs. Crowns were designed with/without occlusal vent holes and produced from monolithic zirconia blocks by the CAD-CAM technique. The two crown types were divided into two groups and cemented with resin and zinc-polycarboxylate cement under 5 kg weight. A universal testing machine applied compressive forces to the crowns until fracture. Fracture resistance values were analyzed using two-way ANOVA and the independent samples t-test with statistical significance set at p < 0.05. RESULTS: According to the two-way ANOVA results, although the crown design did not have a significant effect on fracture resistance (1417.65 ± 337.39 N, 1565.16 ± 517.12 N; crowns with and without vent holes, respectively), the main effect of the cement variable on the fracture resistance was significant. Zinc-polycarboxylate cement (1680.1 ± 375.23 N) showed higher fracture resistance than resin cement (1302.71 ± 420.64 N) in the crowns designed with vent holes (p < 0.005). CONCLUSION: The use of cement-retained implant-supported monolithic zirconia crowns with an occlusal vent hole is safe, and zinc-polycarboxylate cement use may be an appropriate choice for cementation of these crowns.

Influence of interproximal peri-implant tissue and prosthesis contours on food impaction, tissue health and patients' quality of life.

PURPOSE: To investigate tissue features and interproximal contour of posterior implant-supported single crowns (ISSC), which correlate with food impaction. 2) To evaluate the influence of food impaction on the health of the adjacent peri-implant tissue and patients' oral health-related quality of life (OHRQoL). MATERIALS AND METHODS: Patients with posterior ISSC under maintenance between July 2019 and July 2020 were recruited. OHRQoL of patients who self-reported food impaction between ISSC and teeth was evaluated by Oral Impacts on Daily Performance questionnaire and reported at patient level. Interproximal prosthesis contours and periodontal/peri-implant tissue conditions were assessed by clinical and radiographic examination. Differences between food impaction (FI) and non-food impaction (NFI) sites were analysed. RESULTS: Totally, 178 patients (286 ISSC and 410 interproximal spaces) were included. Among 119 patients who self-reported food impaction, 84 (70.6%) reported their OHRQoL to be affected with minor-to-severe intensity. The most commonly affected daily performance was the ability to clean the teeth. Plaque accumulation at ISSC, deeper probing depth, complete interdental papilla fill, loose contact, longer contact length, lower contact point level, closer distance between ISSC and tooth, lesser embrasure surface area, tissue-level implant and cement-retained restoration were found significantly more in the FI group than the NFI group (p < .05). CONCLUSION: Interproximal features of the implant prosthesis were associated with food impaction between the ISSC and the adjacent tooth, which might affect periodontal and/or peri-implant tissue health conditions. Patients' OHRQoL was commonly affected by food impaction, but the intensity was low.

Evaluation of the marginal excess cement and retention force of implant-supported zirconia crowns with various vent designs under different cement application patterns.

OBJECTIVE: To investigate the effects of implant-supported zirconia crowns with various vent designs on the marginal excess cement (MEC) and retention values under different cement application patterns. MATERIALS AND METHODS: Cercon zirconia crowns (n = 36) were divided into the following groups: no venting (NV group), a small occlusal vent hole (SOV group), a large occlusal vent hole (LOV group), and a small palatal-occlusal vent hole (SPV group). The cement was applied to the crowns with different methods: occlusally half axial walls (OH), cervically half axial walls (CH) and all axial walls (AA), and different amounts of cement were applied with a chosen method. The weight of the MEC was calculated, and the retention force was recorded. ANOVA was used to analyze the MEC weights and retention values. RESULTS: In all vented groups, the OH application method resulted in no MEC and the least retention force, and the AA method expressed significantly less MEC (p < 0.01) than the CH method without retention force reduction. At each amount of cement (5, 10, 20, 30 mg), all three venting designs significantly reduced the MEC by the AA method, and the mean MEC of the LOV group was lower than that of any other group. CONCLUSIONS: Applying a thin layer of cement evenly to all axial walls of vented zirconia crowns showed excellent clinical effects regarding the MEC and the retention force. CLINICAL SIGNIFICANCE: Residual excess cement was identified as a possible risk indicator for peri-implant diseases. Simply and effectively minimizing marginal extrusions without reducing the retention force has clinical value. The results of this study indicate that applying a thin layer of cement evenly to all axial walls of vented zirconia crowns is an acceptable method.

[Experimental design of the lower jaw functional loading for implant-supported restoration in unfavorable clinical conditions]. / Eksperimental'noe modelirovanie funktsional'noi nagruzki nizhnei chelyusti pri protezirovanii s oporoi na implantaty v neblagopriyatnykh klinicheskikh usloviyakh.

THE AIM OF THE STUDY: Was to create a finite element design to evaluate the masticatory stress distribution on the full fixed prosthesis with three supporting implants and the mandibular bone in the conditions most closely resembling the real ones. MATERIALS AND METHODS: The geometric design was created with the results of a CBCT of a real patient. The transfer of the DICOM into STL format was carried out in the Mimics Medical 21 program, in which the author's splinting device for the implant was designed. The actual thicknesses of the patient's compact and cancellous bone layers were measured with Romexis ver. 4.5.1. Scanning of the artificial dentition was performed with the iTero Element 2 Version 1.7 which created an object in STL format. Design was performed in the package for finite element analysis Ansys 19.3. Tetrahedral elements of the second order were used for calculation. The structural elements were connected in the model by a rigid «Bonded¼ contact. RESULTS: A finite element model has been created for the experimental load design on the lower jaw for immediate implant restoration with few supports in combination with a device for stabilizing the implant in unfavorable clinical conditions. It is shown that the designed finite element model takes into account the biomechanics of the prosthesis with few supports. When calculating, the entire model was fixed to the mandibular process at its base, and was loaded with a force of 500 N, distributed over the teeth. The values of the maximum stresses obtained in the elements were 51.8 MPa for the compact layer and 245 MPa for titanium elements. CONCLUSION: Thus, we created personalized geometric and finite element models for calculating the distribution of functional load on a long full fixed implant-supported prosthesis with few artificial supports, which makes the experimental results more accurate and correct.

A simplified digital workflow for the prosthetic finishing of implant rehabilitations: a case report.

The aim of this article is to describe how, during the provisional and definitive prosthetic phases, using new digital technologies, it is possible to improve the ergonomics of the prosthetist's work and reduce the discomfort of patients, subjecting them to the fewest possible appointments at the dentist. The proposal of a full digital protocol, described by the following case report, for the realization of a definitive prosthetic rehabilitation supported by a reduced number of implants, in fact, allows to considerably reduce the number of appointments and reduce any bias. A 67-year-old male patient presents for the first visit to the Department of Dentistry of the San Raffaele Hospital, wearing a removable upper prosthesis and with the request to heal the aesthetic and functional situation through prosthetics fixed. An initial panoramic radiograph was performed, intra and extra oral photos were taken and also intraoral impressions. A stereo-lithographic models are obtained from intraoral scans, and two total prostheses, upper and lower, were packaged for the provisional post-surgical phase was performed. In accordance with the All-on-4 method 8 implant fixtures were placed. For the final prosthetic phase, the patient underwent only two operative sessions. In the first session, scans were taken with the provisionals in situ, of the patient's mucous membranes and with the Scan-abutments in place. In the second session using specific CADSoftware the matching of the STL files of the three scans were created, the opposing arches of the patient were related on a digital articulator, and the milled titanium bars were immediately constructed and finished with the resin. Finally, the definitive prostheses were delivered to the patient without any other test. Digital technology has allowed a clear reduction in working times and costs and has allowed the reduction of stress for patients who undergo invasive and extensive treatments to recover aesthetics and function, and for clinicians who must manage complex cases with fewer appointments possible.

A Novel Approach for Converting a Mandibular Complete Denture to a Fixed Interim, Screw-Retained Implant Prostheses: A Case Report.

For most of the last century, conventional complete dentures have been the standard of care and the most common treatment for edentulous patients. Technological advancements in fabrication techniques may significantly reduce the number of office visits required to fabricate complete dentures. Immediate occlusal loading with mandibular full arch prostheses has been extensively researched and is now one of the standards of care for edentulous patients. A clinical technique for converting a mandibular immediate complete denture to an interim full arch, screw-retained fixed prosthesis with novel implant restorative components for immediate loading on four implants is described.

Influence of Flat Occlusal Splint on Stresses Induced on Implants for Different Fixed Prosthetic Systems.

OBJECTIVE: The flat occlusal plate has been recommended to reduce stress concentration in implant prosthesis treatments. The purpose was to investigate the influence of the occlusal splint on three-element implant-supported fixed prosthesis. MATERIALS AND METHODS: A three-dimensional virtual model was created consisting of a cortical and spongy bone block simulating the region from first premolar to the maxillary first molar using two HE or MT implants (4 x 11mm) with Ti and/or Y-TZP abutments. The second premolar was the pontic of the prosthesis. The three-element fixed prosthesis with a zirconia infrastructure and Y-TZP coating were cemented, in addition to using a flat occlusal splint made of acrylic resin in the region. Combined axial and oblique loads of 100N and 300N were applied. RESULTS: The tensile stresses on MT implant bone tissue produced values of 4-19% lower than those of HE implants. The lowest differences were observed for oblique loading with an occlusal splint, with a 4% (Ti-Y-TZP) and 9% (Ti-Ti) decrease. When the compressive stresses were evaluated, HE implants produced lower values than MT implants. CONCLUSION: A significant increase was observed in the oblique loading stresses in the absence of occlusal splints, regardless of the applied load.

Convergent implant transmucosal collar and healing abutment: aesthetics influence on soft tissues. A clinical study.

Two conditions are necessary for a correct and functional prosthetic implant rehabilitation: maintaining pre-implant soft tissue health and stability of bone tissue, in terms of implant osseous-integration and maintenance of optimal crestal attachment levels. In addition to these parameters - necessary for the longevity of the restoration - one of the main aspects of therapy is the achievement of a final aesthetic that reproduces as faithfully as possible the natural anatomy of the lost tooth and the associated soft tissues. To achieve this last objective, an implant system was designed and used by our group. This implant is characterized by a convergent trans-mucosal emergence fixture associated with a progressive closing system of trans-mucosa healing pillars (healing abutment). This guarantee, together with the micro and macrostructure of the implant, an immediate and highly aesthetic condition of the peri-implant soft tissues, and in the same time an optimal seal on the convergent neck of the implant itself.

Complete Arch Monolithic Zirconia Prosthesis Supported By Cobalt Chromium Metal Bar: A Clinical Report.

Complete arch fixed implant supported prosthesis made of monolithic zirconia is a popular treatment option with minimal complications, as documented in the literature over a 5-year period. One of the limitations of this material is its inability to be used when the span between adjacent implants is excessively long. A potential solution to mitigate this problem is to support the zirconia prosthesis with a metal substructure, which intrinsically has higher tensile strength. This clinical report describes the successful use of this prosthetic design in a male patient with bruxism and history of multiple implant failures in the maxilla. This resulted in a large anterior-posterior span between the anterior implants in the maxillary lateral incisor region and the distal implants in the pterygoid region. This article also describes the use of a split file digital workflow to scan the prototype prosthesis and then digitally design and mill the screw-retained cobalt chromium bar, as well as the overlaying of zirconia prosthesis which was retained by separate screws. This novel approach offers promise for management of the atrophic maxilla where implants with remote anchorage are used resulting in broader distribution of implants.

Comparison of Stress Distribution and Deformation of Four Prosthetic Materials in Full-mouth Rehabilitation with Implants: A Three-dimensional Finite Element Study.

AIM: This study aimed to compare the von Mises stress distribution and deformation on the implant, abutment, and abutment screw using metal-ceramic, zirconia, polyether ether ketone (PEEK), and Trinia as prosthetic materials for full-mouth cement-retained implant prosthesis using finite element analysis. MATERIALS AND METHODS: Four, 3-dimensional mandibular models were designed using Solidworks software. Six conical implants of 4.5 × 11.5 mm, with an internal hexagonal abutment, were fabricated and placed. The physical properties of the implant components, bone, and crowns were simulated to mesh the three-dimensional finite element models. The bite was recorded, and various contact points were marked, on which 50 N loads were applied. The von Mises stress distribution and resultant deformation were analyzed using the finite element method. RESULTS: Higher stress distribution was recorded on the implants, abutments, and abutment screws when zirconia and PEEK prosthesis were used in comparison to metal-ceramic and Trinia. In consideration of deformation, zirconia and Trinia resulted in higher deformation of the implant assembly, abutment, and abutment screw when compared to metal-ceramic and PEEK prosthesis. Anterior implants showed a higher deformation and stress distribution when compared to posterior implants for all four prosthetic materials. CONCLUSION: Within the limitations of the study, metal-ceramic and Trinia showed less stress distribution, while metal-ceramic and PEEK exhibited less deformation on implant and its components. Hence in future, Trinia and PEEK along with metal-ceramic can be promising prosthetic materials of choice in full-mouth rehabilitation with implants. CLINICAL SIGNIFICANCE: Considering the deformation and stress distribution on the implant and its components, the selection of prosthetic material in full-mouth rehabilitation has always been a challenge. Findings of the abovementioned cross-sectional observational study could give an overall insight into materials such as metal-ceramic and Trinia as materials of choice, which can provide a basis for future clinical trials.

Effect of Implant Position and Attachment Type on the Biomechanical Behavior of Mandibular Single Implant Prostheses.

This study aimed at evaluating different implant positions and attachment systems for mandibular single implant prostheses (MSIP) with respect to loading of bone and prosthesis displacement. A model with three interforaminal implants served as a basis. Four prostheses differing in the attachment type used (ball anchor, locator, rigid telescopic crown, non-rigid telescopic crown) were fabricated. During occlusal loading, the prostheses were either supported by a midline implant, the left canine implant or the two canine implants. Strain and displacement measurements conducted during loading were quantitatively compared. In general, molar loading led to high levels of prosthesis displacement while loading in the incisor area caused higher strains at the supporting implants and unilateral loading led to an unequal distribution of strains. Using the canine implant instead of the midline implant for support resulted in greater magnitude and disparity of loading while the use of two implants had no clear advantage. The use of telescopic crowns led to inconsistent results. None of the attachments seems to be ideal as they all transferred strain to the supporting implant. In particular, the unequal distribution of strain indicative of moment loading is of concern. An alternative attachment system with a consistent cushioning effect seems desirable.

Manufacturing of Metal Frameworks for Full-Arch Dental Restoration on Implants: A Comparison between Milling and a Novel Hybrid Technology.

PURPOSE: To determine the trueness and precision of frameworks manufactured with a selective laser melting/milling hybrid technique (SLM/m) and conventional milling by comparing the implant-platform/framework interface with those of the original computer-aided design (CAD). MATERIALS AND METHODS: Using a virtual 6-implant-supported full-arch framework CAD drawing, 27 titanium replicas were manufactured by 3 independent manufacturing centers (n = 9/center) using a hybrid SLM/m technology (labs 1 and 2) or the conventional milling technique (lab 3). Using an opto-mechanical coordinate measuring machine, the frameworks' misfit distribution and patterns were analyzed, and the position error between paired platform positions within each framework was evaluated to calculate the misfit tendency for each group. A multilevel analysis using a mixed-effects model was conducted (α = 0.05). The trueness was evaluated as the dimensional difference from the original, while the precision as the dimensional difference from a repeated scan. RESULTS: The 3 dimensional misfits differed significantly among the 3 groups, with the milled group exhibiting the least accurate outcome (p = 0.005). The mean 3D positioning errors ranged from 8 to 16 µm and from 9 to 22 µm for the SLM/m technique (labs 1 and 2, respectively), and from 20 to 35 µm for conventional milling (lab 3). Regarding the misfit distribution pattern, the misfit increased with the distance between paired platform positions in all groups. CONCLUSIONS: All groups had 3D misfits well within the error limits reported in the literature. The 3D misfits of new hybrid (SLM/milling) and conventional (milling) procedures differed significantly among them, with the milling technique the less accurate and precise. The largest errors in all groups were found between the most distant implants, resulting in a correlation between the framework span and the inaccuracies.