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.

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.

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.

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.

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.

Effects of design parameters on fracture resistance of glass simulated dental crowns.

OBJECTIVE: This study aimed to individually quantify the effects of various design parameters, including margin thickness, convergence angle of abutment, and bonding conditions on fracture resistance of resin bonded glass dental crown systems (namely, glass simulated crown). MATERIALS AND METHODS: An in vitro experimental test and an in silico computational eXtended Finite Element Method (XFEM) were adopted to explore crack initiation and propagation in glass simulated crown models with the margin thickness ranging from 0.8 to 1.2mm, convergence angle from 6° to 12°, and three different bonding conditions, namely non-bonded (NB), partially bonded (PB), fully bonded (FB). RESULTS: The XFEM modeling results of cracking initiation loads and subsequent growth in the glass simulated crown models were correlated with the experimental results. It was found that the margin thickness has a more significant effect on the fracture resistance than the convergence angle. The adhesively bonded state has the highest fracture resistance among these three different bonding conditions. CONCLUSION: Crowns with thicker margins, smaller convergence angle and fully bonded are recommended for increasing fracture resistance of all-ceramic crowns. This numerical modeling study, supported by the experimental tests, provides more thorough mechanical insight into the role of margin design parameters, thereby forming a novel basis for clinical guidance as to preparation of tapered abutments for all-ceramic dental crowns.

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.

Thermally induced fracture for core-veneered dental ceramic structures.

Effective and reliable clinical uses of dental ceramics necessitate an insightful analysis of the fracture behaviour under critical conditions. To better understand failure characteristics of porcelain veneered to zirconia core ceramic structures, thermally induced cracking during the cooling phase of fabrication is studied here by using the extended finite element method (XFEM). In this study, a transient thermal analysis of cooling is conducted first to determine the temperature distributions. The time-dependent temperature field is then imported to the XFEM model for viscoelastic thermomechanical analysis, which predicts thermally induced damage and cracking at different time steps. Temperature-dependent material properties are used in both transient thermal and thermomechanical analyses. Three typical ceramic structures are considered in this paper, namely bi-layered spheres, squat cylinders and dental crowns with thickness ratios of either 1:2 or 1:1. The XFEM fracture patterns exhibit good agreement with clinical observation and the in vitro experimental results obtained from scanning electron microscopy characterization. The study reveals that fast cooling can lead to thermal fracture of these different bi-layered ceramic structures, and cooling rate (in terms of heat transfer coefficient) plays a critical role in crack initiation and propagation. By exploring different cooling rates, the heat transfer coefficient thresholds of fracture are determined for different structures, which are of clear clinical implication.

Multiscale design of surface morphological gradient for osseointegration.

Rapid and stable osseointegration signifies a major concern in design of implantable prostheses, which stimulates continuous development of new implant materials and structures. This study aims to develop a graded configuration of a bead/particle coated porous surface for implants by exploring how its micromechanical features determine osseointegration through multiscale modeling and remodeling techniques. A typical dental implantation setting was exemplified for investigation by using the remodeling parameters determined from a systematic review of bone-implant-contact (BIC) ratio published in literature. The global responses of a macroscale model were obtained through 48 month remodeling simulation, which forms the basis for the 27 microscopic models created with different particle gradients ranging from 30 to 70µm. The osseointegration responses are evaluated in terms of the BIC ratio and the averaged 10% peak Tresca shear stress (PTS). Within the sampling designs considered, the configuration with 50-30-30µm particle sizes provides the best outcome, counting 20% more BIC ratio and 0.17MPa less PTS compared with the worst case scenario, also outperforming the best uniform morphology of 70µm particles. Furthermore, the response surface method (RSM) was utilized to formulate the bone remodeling responses in terms of gradient parameters across three layers. Gradient 30.0-30.0-32.1 is found an optimal gradient for BIC ratio, and 70-45.4-40.8 the best for the minimum PTS. The multiobjective optimization was finally performed to simultaneously maximize BIC ratio and minimize PTS for achieving the best possible overall outcome. Due to strong competition between these two design objectives, a Pareto front is generated. To make a proper trade-off, the minimum distance selection criterion is considered and the gradient of 37.1-70.0-67.7 appears an optimal solution. This study provides a novel surface configuration and design methodology for individual patient that allow optimizing topographical gradient for a desirable patient-specific biomechanical environment to promote osseointegration.

Finite element analysis suggests functional bone strain accounts for continuous post-eruptive emergence of teeth.

OBJECTIVE: To explore the possible role of functional stress in driving continuous post-eruptive emergence of teeth. DESIGN: A two dimensional finite element analysis model was established with a single mandibular premolar subjected to sagittal bending. Equivalent strain was charted for the inner and outer surfaces of the lamina dura, because bone deposition and resorption of this structure is confined to surface osteoblasts and osteoclasts. Bone disuse resorption was assumed to take place at equivalent strain values below 0.0008, while deposition was above 0.002. Strain in the periodontal ligament and principal stress throughout the model were also characterized. RESULTS: Strain analysis indicated bone maintenance for the lamina dura throughout most of the root length, but in both the apical and upper root regions, resorption was predicted for the outer surface, and bone deposition was predicted for the inner surface of the lamina dura. Strain in the periodontal ligament varied little with the exception of a marked increase close to the crown. Principal stress analysis revealed compression of the lower model border, with areas of increasing tension towards the upper model border. CONCLUSIONS: Strain from functional forces may continuously drive post-eruptive emergence of teeth through bony remodelling of the lamina dura, lifting teeth by both raising the apical lamina dura, and narrowing the upper root space to accommodate tapering root form. Such strain-driven bone turnover may contribute to pre-eruptive movement of teeth.

Effects of occlusal inclination and loading on mandibular bone remodeling: a finite element study.

PURPOSE: To provide a preliminary understanding of the biomechanics with respect to the effect of cusp inclination and occlusal loading on the mandibular bone remodeling. MATERIALS AND METHODS: Three different cusp inclinations (0, 10, and 30 degrees) of a ceramic crown and different occlusal loading locations (central fossa and 1- and 2-mm offsets horizontally) were taken into account to explore the stresses and strains transferred from the crown to the surrounding dental bone through the implant. A strain energy density obtained from two-dimensional plane-strain finite element analysis was used as the mechanical stimulus to drive cancellous and cortical bone remodeling in a buccolingual mandibular section. RESULTS: Different ceramic cusp inclinations had a significant effect on bone remodeling responses in terms of the change in the average peri-implant bone density and overall stability. The remodeling rate was relatively high in the first few months of loading and gradually decreased until reaching its equilibrium. A larger cusp inclination and horizontal offset (eg, 30 degrees and 2-mm offset) led to a higher bone remodeling rate and greater interfacial stress. CONCLUSIONS: The dental implant superstructure design (in terms of cusp inclination and loading location) determines the load transmission pattern and thus largely affects bone remodeling activities. Although the design with a lower cusp inclination recommended in previous studies may reduce damage and fracture failure, it could, to a certain extent, compromise bone engagement and long-term stability.

Loading of a single implant in simulated bone.

This study investigated the effect of occlusal design on the strain developed in simulated bone of implant-supported single crown models. Triaxial strain gauges were attached at the cervical area of each model. Occlusal design, load location, and magnitude were examined to determine the maximum axial principal strains (ΜÓ) of four occlusal designs: 30-degree cusp inclination with 4- and 6-mm occlusal table dimensions and a 10-degree cusp inclination with 4- and 6-mm occlusal table dimensions. Statistical differences were found for peak average maximum principal strains between each occlusal design when the applied load was directed along the central fossa and 2 mm buccal to the central fossa along the inclined plane, with strain gauges attached at the cervicobuccal (P < .001) and cervicolingual (P ⋜ .001) aspects. In all loading conditions, the 30-degree cusp inclination and 6-mm occlusal table dimension consistently presented the largest strains compared with the other occlusal designs. A reduced cusp inclination and occlusal table dimension effectively reduced experimental bone strain on implant-supported single crowns. The occlusal table dimension appeared to have a relatively more important role than cusp inclination.