Accuracy of implant placement with computer-aided static, dynamic, and robot-assisted surgery: a systematic review and meta-analysis of clinical trials.

This systematic review explores the accuracy of computerized guided implant placement including computer-aided static, dynamic, and robot-assisted surgery. An electronic search up to February 28, 2023, was conducted using the PubMed, Embase, and Scopus databases using the search terms "surgery", "computer-assisted", "dynamic computer-assisted", "robotic surgical procedures", and "dental implants". The outcome variables were discrepancies including the implant's 3D-coronal, -apical and -angular deviations. Articles were selectively retrieved according to the inclusion and exclusion criteria, and the data were quantitatively meta-analysed to verify the study outcomes. Sixty-seven articles were finally identified and included for analysis. The accuracy comparison revealed an overall mean deviation at the entry point of 1.11 mm (95% CI: 1.02-1.19), and 1.40 mm (95% CI: 1.31-1.49) at the apex, and the angulation was 3.51˚ (95% CI: 3.27-3.75). Amongst computerized guided implant placements, the robotic system tended to show the lowest deviation (0.81 mm in coronal deviation, 0.77 mm in apical deviation, and 1.71˚ in angular deviation). No significant differences were found between the arch type and flap operation in cases of dynamic navigation. The fully-guided protocol demonstrated a significantly higher level of accuracy compared to the pilot-guided protocol, but did not show any significant difference when compared to the partially guided protocol. The use of computerized technology clinically affirms that operators can accurately place implants in three directions. Several studies agree that a fully guided protocol is the gold standard in clinical practice.

Effect of Customized and Prefabricated Healing Abutments on Peri-Implant Soft Tissue and Bone in Immediate Implant Sites: A Randomized Controlled Trial.

This study aimed to evaluate the effect of customized healing abutments compared to prefabricated healing abutments in immediate implant sites. Twelve patients requiring single immediate implant placement were divided into two groups: a prefabricated group received prefabricated titanium healing abutments, and a customized group received a polyetheretherketone (PEEK) customized healing abutments fabricated based on the individuals' digital impressions. Outcomes, including peri-implant horizontal and vertical soft tissue alteration, bone level change, volume change, pain score, and pink esthetic score (PES) change, were evaluated at the 1-, 4-, and 6-month follow-ups compared to pre-extraction teeth. At the 1- and 4-month follow-ups, the customized group had a significantly lower buccal volume variation (BVv). At the 6-month follow-up, neither group showed any significant difference in the marginal bone change; however, the customized group had a significantly lower PES change and a lower pain score. In the anterior and premolar regions, the customized group showed the preservation of peri-implant buccal horizontal soft tissue and buccal volume, while in the molar regions, the preservation of papilla height and midfacial height was observed. The morphology of the customized healing abutment demonstrated a better trend in preservation of peri-implant soft tissue, esthetic outcomes, and lower patient discomfort in immediate implant sites.

Effects of bone type and occlusal loading pattern on bone remodeling in implant-supported single crown: A finite element study.

PURPOSE: To assess the influence of bone types and loading patterns on the remodeling process over 12 months according to the variations in stress, strain, strain energy density (SED), and density allocation in the bone of implant-supported single crown. MATERIALS AND METHODS: A three-dimensional finite element of a single crown implant was modeled in five different bone types (D1-D4, and grafted bone). A 200 N load was applied on an implant crown with three occlusal loading patterns (nonfunctional contact, functional contact at center, and at 2-mm offset loading). During the first 12 months after implant placement, the SED was employed as a mechanical stimulus to simulate cortical and cancellous bone remodeling. RESULTS: Functional contact at 2-mm offset loading led to a higher bone remodeling rate and stress compared to functional contact at center and nonfunctional contact. Under 2-mm offset loading, the greatest remodeling rate after 12 months was achieved with D3 and D4, D2, grafted, and D1 cortical bone with an average peri-implant density of 1.95, 1.77, 1.56, and 1.50 g/cm3 , respectively. Meanwhile, the highest von Mises stresses were found in D4 (22.2 MPa) and D3 (21.9 MPa) bones. CONCLUSIONS: A greater stress concentration and remodeling rate were found when an off-axial load was applied on an implant placed in low bone density. Although the fastest remodeling processes resulting in increased bone density and strength were found in D3 and D4 bone types with greater off-axial loading that may provide greater bone engagement, it could increase stress concentrations that are susceptible to inducing implant failure.

Biomaterials and Clinical Application of Dental Implants in Relation to Bone Density-A Narrative Review.

Titanium has been the material of choice for dental implant fixtures due to its exceptional qualities, such as its excellent balance of rigidity and stiffness. Since zirconia is a soft-tissue-friendly material and caters to esthetic demands, it is an alternative to titanium for use in implants. Nevertheless, bone density plays a vital role in determining the material and design of implants. Compromised bone density leads to both early and late implant failures due to a lack of implant stability. Therefore, this narrative review aims to investigate the influence of implant material/design and surgical technique on bone density from both biomechanical and biological standpoints. Relevant articles were included for analysis. Dental implant materials can be fabricated from titanium, zirconia, and PEEK. In terms of mechanical and biological aspects, titanium is still the gold standard for dental implant materials. Additionally, the macro- and microgeometry of dental implants play a role in determining and planning the appropriate treatment because it can enhance the mechanical stress transmitted to the bone tissue. Under low-density conditions, a conical titanium implant design, longer length, large diameter, reverse buttress with self-tapping, small thread pitch, and deep thread depth are recommended. Implant material, implant design, surgical techniques, and bone density are pivotal factors affecting the success rates of dental implant placement in low-density bone. Further study is required to find the optimal implant material for a clinical setting's bone state.

Effect of customized abutment taper configuration on bone remodeling and peri-implant tissue around implant-supported single crown: A 3D nonlinear finite element study.

PURPOSE: The optimal configuration of a customized implant abutment plays a crucial role in promoting bone remodeling and maintaining the peri-implant gingival contour. However, the biomechanical effects of abutment configuration on bone remodeling and peri-implant tissue remain unclear. This study aimed to evaluate the influence of abutment taper configurations on bone remodeling and peri-implant tissue. MATERIALS AND METHODS: Five models with different abutment taper configurations (10°, 20°, 30°, 40°, and 50°) were analyzed using finite element analysis (FEA) to evaluate the biomechanical responses in peri-implant bone and the hydrostatic pressure in peri-implant tissue. RESULTS: The results demonstrated that the rate of increase in bone density was similar in all models. On the other hand, the hydrostatic pressure in peri-implant gingiva revealed significantly different results. Model 10° showed the highest maximum and volume-averaged hydrostatic pressures (69.31 and 4.5 mmHg), whereas Model 30° demonstrated the lowest values (57.83 and 3.88 mmHg) with the lowest excessive pressure area. The area of excessive hydrostatic pressure decreased in all models as the degree of abutment taper increased from 10° to 30°. In contrast, Models 40° and 50° exhibited greater hydrostatic pressure concentration at the cervical region. CONCLUSION: In conclusion, the abutment taper configuration had a slight effect on bone remodeling but exerted a significant effect on the peri-implant gingiva above the implant platform via hydrostatic pressure. Significant decreases in greatest and average hydrostatic pressures were observed in the peri-implant tissues of Model 30°. However, the results indicate that implant abutment tapering wider than 40° could result in a larger area of excessive hydrostatic pressure in peri-implant tissue, which could induce gingival recession.

Effect of gingival height of a titanium base on the biomechanical behavior of 2-piece custom implant abutments: A 3-dimensional nonlinear finite element study.

STATEMENT OF PROBLEM: Titanium base (TiBase) abutments to restore an implant-supported single crown are available in different gingival heights, but information on the biomechanical effects of the gingival heights is lacking. PURPOSE: The purpose of this nonlinear finite element analysis study was to evaluate the effects of TiBase gingival heights on the biomechanical behavior of custom zirconia (CustomZir) abutments and TiBase, including von Mises stress and maximum and minimum principal stress. MATERIAL AND METHODS: TiBases with different gingival heights (0.5 mm, 1 mm, 1.5 mm, and 2 mm) with internal hexagon Morse taper connections were simulated in 3-dimensional models. The simulations (ANSYS Workbench 2020; ANSYS Inc) included the OsseoSpeed EV implant (Ø5.4 mm) (AstraTech; Dentsply Sirona), restoration, and surrounding bone in the mandibular first molar region. An occlusal force of 200 N was applied with a 2-mm horizontal offset toward the buccal side and a 30-degree inclination from the vertical axis. RESULTS: High-stress concentration was observed in the uppermost internal connection area on the buccal side and the antirotational part of the titanium abutment on the lingual side in all models. CustomZir abutments with a shorter gingival height exhibited larger concentrated areas of volume average stress von Mises stress and higher magnitude of maximum and minimum principal stress compared with a taller gingival height. CONCLUSIONS: A TiBase abutment with a taller gingival height reduced the fracture risk of a CustomZir abutment without increasing any mechanical risk.

Effect of implant placement depth on bone remodeling on implant-supported single zirconia abutment crown: A 3D finite element study.

PURPOSE: This study aimed to evaluate the influence of subcrestal implant placement depth on bone remodeling using time-dependent finite element analysis (FEA) with a bone-remodeling algorithm over 12 months. METHODS: Seven models of different subcrestal implant placement depths (0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm) were analyzed using FEA to evaluate the biomechanical responses in the bone and implant, including von Mises equivalent stress, strain energy density (SED), and overloading elements. SED was used as a mechanical stimulus to simulate cortical and cancellous bone remodeling over the first 12 months after final prosthesis delivery. RESULTS: The highest increase in cortical bone density was observed at Depth 1.5, whereas the lowest increase was observed at Depth 3.0. In contrast, the highest increase in bone density was observed at Depth 3.0 in the cancellous bone, whereas the lowest increase was observed at Depth 0. The highest peak von Mises stress in the cortical bone occurred at Depth 2.5 (107.24 MPa), while that in the cancellous bone was at Depth 2.5 (34.55 MPa). Notably, the maximum von Mises stress values in the cancellous bone exceeded the natural limit of the bony material, as indicated by the overloading elements observed at the depths of 2.0, 2.5, and 3.0 mm. CONCLUSIONS: Greater bone density apposition is observed with deeper implant placement. An implant depth of more than 1.5 mm exhibited a higher maximum von Mises stress and greater overloading elements.

Biomaterials and Clinical Applications of Customized Healing Abutment-A Narrative Review.

Customized healing abutments have been introduced in clinical practice along with implant surgery to preserve or create natural-appearing hard and soft tissue around the implant. This provides the benefits of reducing the overall treatment time by eliminating the second stage and reducing the elapsed time of the fabrication of the final prostheses. This article aims to review the types and properties of materials used for the fabrication of customized healing abutments and their clinical applications. Articles published in English on customized healing abutments were searched in Google Scholar, PubMed/MEDLINE, ScienceDirect, and the Scopus databases up to August 2022. The relevant articles were selected and included in this literature review. Customized healing abutments can be fabricated from materials available for dental implants, including PEEK, PMMA, zirconia, resin composite, and titanium. All the materials can be used following both immediate and delayed implant placement. Each material provides different mechanical and biological properties that influence the peri-implant tissues. In conclusion, the studies have demonstrated promising outcomes for all the materials. However, further investigation comparing the effects of each material on peri-implant soft and hard tissues is required.

Wear of various restorative materials against 5Y-ZP zirconia.

STATEMENT OF PROBLEM: The ceramic 5-mol% yttria-stabilized zirconia (5Y-ZP) has been developed for dental use in the esthetic zone with greater translucency than 3-mol% yttria-stabilized zirconia (3Y-ZP). However, studies on the wear behavior of 5Y-ZP zirconia against clinically relevant antagonist materials are lacking. PURPOSE: The purpose of this in vitro study was to investigate the wear behavior of 5Y-ZP zirconia against the antagonists 5Y-ZP zirconia, lithium disilicate, palladium alloy, and human enamel. MATERIALS AND METHODS: Flat specimens (n=8) were fabricated from 5Y-ZP zirconia, lithium disilicate, palladium alloy, and human central incisor enamel. A custom wear-simulating device with a sliding pin-on-plate configuration was used for a total of 120 000 wear cycles at 1.6-Hz frequency under a 49-N vertical load while submerged in distilled water at room temperature. The wear volume and maximum wear depth of flat specimens were evaluated with a 3D profilometer. Scanning electron microscopy was used to analyze the characteristics of the worn surfaces. RESULTS: After wear simulation, the 5Y-ZP zirconia and palladium-silver alloy specimens exhibited the least amount of material loss, both in terms of maximum wear depth and wear volume (0.079 ±0.042 µm, 0.001 ±0.001 mm3 and 0.637 ±0.307 µm, 0.001 ±0.000 mm3, respectively). This was followed by human enamel (6.034 ±1.086 µm, 0.009 ±0.001 mm3) and by lithium disilicate, which showed excessive material loss (38.342 ±2.569 µm, 0.213 ±0.024 mm3). Scanning electron microscopy revealed variations in wear mechanisms among the materials. CONCLUSIONS: The 5Y-ZP zirconia and palladium-silver alloy exhibited the lowest wear, followed by human enamel and lithium disilicate. Slight grain dislodgement was displayed on worn 5Y-ZP surfaces, while more apparent grain dislodgement and wear grooves were found on lithium disilicate. Plastic deformation of worn palladium-silver alloy accumulated at the end of wear track. Cracks were detected in the human enamel specimens.

Effects of composite resin core level and periodontal pocket depth on crack propagation in endodontically treated teeth: An extended finite element method study.

STATEMENT OF PROBLEM: Preserving teeth with radicular cracks with or without a periodontal pocket is an alternative to extraction. However, an effective protocol for the restoration of radicular cracks is lacking. PURPOSE: The purpose of this study was to examine the composite resin core level and periodontal pocket depth effects on stress distribution, maximum von Mises stress, and crack propagation in endodontically treated teeth by using the extended finite element (FE) method. MATERIAL AND METHODS: Four 3-dimensional models of a cracked endodontically treated mandibular first molar were constructed: PP2C2 (periodontal pocket depth, 2 mm; composite resin core level, 2 mm below the canal orifice level); PP2C4 (periodontal pocket depth, 2 mm; composite resin core level, 2 mm below the crack level); PP4C2 (periodontal pocket depth, 4 mm; composite resin core level, 2 mm below the canal orifice level); and PP4C4 (periodontal pocket depth, 4 mm; composite resin core level, 2 mm below the crack level). The crack initiation was at the same level in all models. A static 700-N load was applied to the models in a vertical direction. RESULTS: The highest stress in dentin was observed in PP2C2, whereas PP2C4 exhibited the lowest stress and least crack propagation. Stress was high in the dentin and supporting bone. No reduction in crack propagation was observed in the PP4 models, regardless of the composite resin core level. CONCLUSIONS: The periodontal pocket depth (2 mm and 4 mm) and composite resin core level (2 mm below the crack level and 2 mm below the canal orifice level) affected stress concentration in dentin, resulting in different patterns of crack propagation in the FE models.

Effect of Different Customized Abutment Types on Stress Distribution in Implant-Supported Single Crown: A 3D Finite Element Analysis.

PURPOSE: The purpose was to investigate stress distribution among 4 different customized abutment types: titanium abutment (Ti), titanium hybrid-abutment-crown (Ti-Hybrid), zirconia abutment with titanium base (Zir-TiBase), and zirconia hybrid-abutment-crown with titanium base (Zir-Hybrid-TiBase). MATERIALS AND METHODS: To achieve this purpose, 4 types of abutment configurations were simulated. A static load of 200 N (vertical) and 100 N (oblique) were applied to the models. The volume average, maximum, and stress distribution of von Mises stress, including percentage difference, were analyzed with 3D finite element analysis. RESULTS: According to the volume average von Mises stress, the Ti and Zir-TiBase comparison group showed that the Zir-TiBase group dominantly generated the higher value at Ti-base (22.57 MPa) and screw (17.68 MPa). To evaluate the effect of the hybrid-abutment-crown on volume average von Mises stress by comparing the Ti-Hybrid and Zir-Hybrid-TiBase groups, it was revealed that the combination of abutment and crown in the Ti-Hybrid group generated the worst stress concentration at the screw (12.42 MPa), while in the Zir-Hybrid-TiBase group presented stress concentration at the implant (8.90 MPa). CONCLUSIONS: A titanium base improved stress distribution at implant in zirconia abutment with titanium base by absorbing stress itself. Customized titanium hybrid-abutment-crown and zirconia hybrid-abutment-crown with titanium base created concentrated stress at screw and implant; respectively. Both abutment types should be cautiously used and maintenanced regularly.

PEEK Biomaterial in Long-Term Provisional Implant Restorations: A Review.

Polyetheretherketone (PEEK) has become a useful polymeric biomaterial due to its superior properties and has been increasingly used in dentistry, especially in prosthetic dentistry and dental implantology. Promising applications of PEEK in dentistry are dental implants, temporary abutment, implant-supported provisional crowns, fixed prosthesis, removable denture framework, and finger prosthesis. PEEK as a long-term provisional implant restoration has not been studied much. Hence, this review article aims to review PEEK as a long-term provisional implant restoration for applications focusing on implant dentistry. Articles published in English on PEEK biomaterial for long-term provisional implant restoration were searched in Google Scholar, ScienceDirect, PubMed/MEDLINE, and Scopus. Then, relevant articles were selected and included in this literature review. PEEK presents suitable properties for various implant components in implant dentistry, including temporary and long-term provisional restorations. The modifications of PEEK result in wider applications in clinical dentistry. The PEEK reinforced by 30-50% carbon fibers can be a suitable material for the various implant components in dentistry.

Effect of Number and Location on Stress Distribution of Mini Dental Implant-Assisted Mandibular Kennedy Class I Removable Partial Denture: Three-Dimensional Finite Element Analysis.

Purpose: To investigate effects of number and location on patterns of von Mises stress distribution and volume average stress on abutment tooth, edentulous ridge, mini dental implant, and surrounding bone of mini dental implant-assisted mandibular Kennedy class I removable partial denture. Materials and Methods: Eight three-dimensional finite element models of mandibular Kennedy class I with different numbers and locations of mini dental implants were constructed. Mini dental implants were generated in the area of second premolar, first molar, and second molar, respectively. A static load of 400 N was applied on all models. The von Mises stress and volumetric average stress were calculated by three-dimensional finite element analysis. Result: The minimum volumetric average stress of abutment tooth was found in the model, where there was one mini dental implant at the second molar position and 2 mini dental implants at first molar and second molar positions. The model with three mini dental implants had reduced volumetric average stress of abutment tooth, which was not different from the model with two mini dental implants. However, the minimum volumetric average stress of mini dental implant and surrounding bone were found when three mini dental implants were applied, followed by two and one mini dental implants, respectively. Conclusion: Placing at least one mini dental implant at a second molar position can help reduce stress transferred to the abutment tooth. Stresses around each implant and surrounding bone reduced with increased numbers of mini dental implants.

Stress Distribution Pattern in Mini Dental Implant-Assisted RPD with Different Clasp Designs: 3D Finite Element Analysis.

Introduction: The removable partial denture (RPD) components, especially the retentive arm, play a major role in the loading characteristic on supporting structures. Objective: To evaluate and compare the effect of different clasp designs on the stress distribution pattern, maximum von Mises stress, and average hydrostatic pressure on abutment teeth, as well as edentulous ridges, mini dental implants (MDIs), and peri-implant bone between the conventional removable partial denture (CRPD) and mini dental implant-assisted distal extension removable partial denture (IARPD) using a three-dimensional finite element analysis (3D FEA). Materials and Methods: 3D FEA models of mandibular arches, with and without bilateral MDI at the second molar areas, and Kennedy class I RPD frameworks, with RPA, RPI, Akers, and no clasp component, were generated. A total of 200 N vertical load was bilaterally applied on both sides of distal extension areas, and the stress was analyzed by 3D FEA. Results: The stress concentration of IARPD with RPI clasp design was located more lingually on abutment teeth, MDI, and peri-implant bone, while the other designs were observed distally on the supporting structures. The maximum von Mises stress on the abutment root surface was decreased when the RPDs were assisted with MDIs. The CRPD and IARPD with the Akers clasp design showed the highest von Mises stress followed by the designs with RPA and RPI clasp, respectively. The average hydrostatic pressure in each group was in approximation. Conclusion: The placement of MDIs on distal extension ridges helps to reduce the stress concentration on denture supporting structures. The maximum von Mises stress is affected by the different designs of clasp components. The CRPD and the IARPD with RPI clasp provide the least stress on supporting structures.

Wear Behavior of Different Generations of Zirconia: Present Literature.

Objective: The wear behavior of the novel zirconia generation is less well understood and may be affected by compositional modifications compared to the conventional zirconia. Materials and Methods: Combinations of keywords such as "zirconia," "high translucent," and "wear" were searched in PubMed and Google Scholar databases up to May 2021. The total of 23 relevant articles was selected according to inclusion criteria. Results: Reports show comparable wear resistance of translucent zirconia to the conventional zirconia despite an increased cubic phase content and lower mean flexural strength. A meticulously polished surface creates the lowest surface roughness, producing favorable zirconia wear resistance and antagonist wear compared to a glazed surface. In comparison to other ceramic materials, zirconia produces the least wear on an enamel antagonist and almost undetectable wear when opposed by zirconia. Wear when paired against resin materials yields a favorable outcome, whereas wear behavior against a metal antagonist varies with the surface hardness of the metal. Conclusions: All zirconia generations are considered wear-friendly to all types of antagonists. Nonetheless, comparative studies on antagonist wear opposing zirconia of different compositions are still limited and further investigation is required.

Validity and Reliability of Intraoral Camera with Fluorescent Aids for Oral Potentially Malignant Disorders Screening in Teledentistry.

There is limited documentation of using fluorescence images in oral potentially malignant disorders (OPMDs) and oral cancer screening through the field of teledentistry. This study aims to develop and evaluate the validity and reliability of the intraoral camera with the combination method of autofluorescence and LED white light used for OPMDs and oral cancer screening in teledentistry. The intraoral camera with fluorescent aids, which uses a combined method of both autofluorescence and LED white light, was developed before the device was evaluated for validity and reliability as a OPMDs screening tool for teledentistry. All lesions of thirty-four OPMD patients underwent biopsy for definitive diagnosis and were examined by an oral medicine specialist. Both images under autofluorescent and LED white light mode captured from the device were sent online and interpreted for the initial diagnosis and dysplastic features in addition to being compared to the direct clinical examination and histopathological findings. The combination method was also compared with autofluorescence method alone. The device provided good image quality, which was enough for initial diagnosis. Using the combination method, sensitivity, specificity, PPV, and NPV of the device via teledentistry were 87.5%, 84.6%, 63.6%, and 95.7%, respectively, which were higher than autofluorescence method alone in every parameter. The concordance of dysplastic lesion was 85.29% and 79.41% for category of lesion. The validity and reliability results of the combination method for the screening of dysplasia in OPMDs were higher than autofluorescent method alone. The intraoral camera with fluorescent aids for the OPMDs screening can be utilized for screening via teledentistry.

Effect of the Location of Dental Mini-Implants on Strain Distribution under Mandibular Kennedy Class I Implant-Retained Removable Partial Dentures.

PURPOSE: To investigate the effect of minidental implant location on strain distributions transmitted to tooth abutments and dental minidental implants under mandibular distal extension removable partial denture. MATERIALS AND METHODS: A mandibular Kennedy Class I distal extension model missing teeth 35-37 and 45-47 was constructed. Six dental mini-implants were placed at positions A, B, and C, where position A was 6.5 mm distal to the abutment teeth with 5 mm between each position. Fourteen uniaxial strain gauges were bonded on the model at the region of dental mini-implant and abutment (first premolar). Four groups were designated according to the location of the mini-implants. A load of 150 N and 200 N was applied using an Instron testing machine. Loadings consisted of bilateral and unilateral loading. Comparisons of the mean microstrains among all strain gauges in all situations were analyzed. RESULTS: Variation in mini-implant locations induced local strains in different areas. Strains at the tooth abutment were significantly decreased in the group in which implants were placed mesially. Strains around the mini-implants showed different patterns when loaded with different loading conditions. The group in which implants were placed distally showed the lowest strains compared to other groups. CONCLUSION: Mesially placed mini-implants showed the lowest strain around abutment teeth, while a distally-placed mini-implants presented the lowest strain around mini-implants themselves. Under favorable biting force, mini-implant is an option to assist mandibular distal extension removable partial denture. Mesially placed mini-implants are recommended when the abutment has periodontally compromised conditions and a distally placed mini-implant when periodontal conditions are stable.

Comparative study of stress characteristics in surrounding bone during insertion of dental implants of three different thread designs: A three-dimensional dynamic finite element study.

The objective of this study is to evaluate the stress distribution characteristics around three different dental implant designs during insertion into bone, using dynamic finite element stress analysis. Dental implant placement was simulated using finite element models. Three implants with different thread and body designs (Model 1: root form implant with three different thread shapes; Model 2: tapered implant with a double-lead thread; and Model 3: conical tapered implant with a constant buttress thread) were assigned to insert into prepared bone cavity models until completely placed. Stress and strain distributions were descriptively analyzed. The von Mises stresses within the surrounding bone were measured. At the first 4-mm depth of implant insertion, maximum stress within cortical bone for Model 3 (175 MPa) was less than the other models (180 MPa each). Stress values and concentration area were increasing whereas insertion depth increased. At full implant insertion depth, maximum stress level in Model 1 (35 MPa) within the cancellous bone was slightly greater than in Models 2 (30 MPa) and 3 (25 MPa), respectively. Generally, for all simulations, the highest stress value and the location of the stress concentration area were mostly in cortical bone. However, the stress distribution patterns during the insertion process were different between the models depending on the different designs geometry that contacted the surrounding bone. Different implant designs affect different stress generation patterns during implant insertion. A range of stress magnitude, generated in the surrounding bone, may influence bone healing around dental implants and final implant stability.

Effects of different numbers of mini-dental implants on alveolar ridge strain distribution under mandibular implant-retained overdentures.

PURPOSE: To investigate the strains around mini-dental implants (MDIs) and retromolar edentulous areas when using different numbers of MDIs in order to retain mandibular overdentures. MATERIALS AND METHODS: Four different prosthetic situations were fabricated on an edentulous mandibular model including a complete denture (CD), and three overdentures, retained by four, three or two MDIs in the interforaminal region with retentive attachments. A static load of 200N was applied on the posterior teeth of the dentures under bilateral or unilateral loading conditions. The strains at the mesial and distal of the MDIs and the retromolar edentulous ridges were measured using twelve strain gauges. Comparisons of the mean microstrains among all strain gauges in all situations were analyzed. RESULTS: The strain distribution determined during bilateral loading experienced a symmetrical distribution; while during unilateral loading, the recorded strains tended to change from compressive strains on the loaded side to tensile strains. Overall, the number of MDIs was found to be passively correlated to the generated compressive strain. The highest strains were recorded in the four MDIs followed by three, two MDIs retained overdenture and CD situations, respectively. The highest strain was found around the terminal MDI. CONCLUSIONS: The use of a low number of MDIs tends to produce low strain values in the retromolar denture-bearing area and around the terminal MDIs during posterior loadings. However, when using a high number of MDIs, the overdenture tends to have more stability during function.

Bone's responses to different designs of implant-supported fixed partial dentures.

This paper explores the biomechanics and associated bone remodeling responses of two different abutment configurations, namely implant-implant-supported versus tooth-implant-supported fixed partial dentures. Two 3D finite element analysis models are created based upon computerized tomography data. The strain energy density induced by occlusal loading is used as a mechanical stimulus for driving the bone remodeling. To measure osseointegration and stability during healing, a resonance frequency analysis is conducted. At the second premolar peri-implant region, overloading resorption around the neck of implant is identified in both the models over the first 12 months. Stress-shielding around the edentulous region is also observed in both the models with a greater resorption rate found in the implant-implant case. The remodeling and resonance frequency analyses reveal that the tooth-implant scheme offers a higher degree of osseointegration. The remodeling procedure is expected to provide prosthodontists with a modeling tool to assess possible long-term clinical outcomes.