Biomechanical Evaluation of Stress Distribution in a Natural Tooth Adjacent to a Dental Implant Using Finite Element Modeling

Abstract

Objective Emerging evidence suggests an increased incidence of mechanical complications in natural teeth, particularly maxillary premolars, adjacent to dental implants. This study aimed to investigate and compare the maximum von Mises stress induced in a natural tooth adjacent to either a natural tooth or a dental implant under different occlusal loading and interproximal space conditions.

Materials and Methods Three-dimensional finite element models of maxillary first and second premolars were generated for both control (two natural teeth) and experimental (first premolar dental implant and natural second premolar) groups to analyze stress levels and distributions. Occlusal forces were applied to the second premolar, and the resulting maximum von Mises stress was compared between groups. The influence of dental implant presence, interproximal space, and occlusal load contact position and direction on the stress level and distribution in the loaded tooth was investigated.

Results Compared with the control group, the experimental group exhibited higher stress levels in the natural second premolar under occlusal forces, although the stress distribution remained similar. The presence of interproximal spaces, either between natural teeth or between a tooth and an implant, exacerbated stress in the loaded teeth due to reduced proximal contact area and increased stress concentration. Additionally, the position and direction of occlusal force contact differentially affected the stress level, although not the stress distribution, within the experimental tooth group.

Conclusion Dental implants increase stress on adjacent natural teeth, particularly when interproximal space exists. Occlusal force direction and position influence stress in loaded natural teeth, whether adjacent to other natural teeth or implants. The results underscore the critical importance of comprehensive patient evaluation, meticulous treatment planning, and consistent maintenance in dental implant restorations to mitigate potential complications affecting adjacent natural teeth.

Keywords

adjacent natural tooth - dental implants - finite element analysis - stress distribution - tooth displacement

Introduction

Dental implants offer a reliable and aesthetically pleasing replacement for missing teeth, mimicking natural tooth structure and function.[1] [2] Typically composed of a titanium screw inserted into the jawbone, an abutment connecting the implant to the restoration, and a custom-made crown, dental implants provide superior stability and prevent jawbone deterioration compared with traditional alternatives. However, the implant placement process is more complex and costly. A mapping review by Sadowsky and Brunski[3] compared the advantages and disadvantages of dental implants and natural teeth. While implants excel in withstanding compressive forces without inducing bone resorption, natural teeth demonstrate superior biological resistance. The periodontal ligament (PDL) of natural teeth provides a robust defense against biological challenges due to its rich vascularity, stem cell population, and inflammatory response capacity. Its shock-absorbing properties also mitigate the impact of masticatory forces. The absence of PDL in dental implant systems may alter the mechanical forces experienced by adjacent natural teeth under occlusal loading.

A growing body of evidence highlights the potential for mechanical complications in natural teeth adjacent to dental implants. Rosen et al[4] reported a series of cases involving severe vertical root fractures in endodontically treated teeth located near implants. Notably, these teeth were restored with crowns and posts supported by adequate root canal fillings. Similarly, a study involving 18 cases of cracked teeth in nonendodontically treated teeth following implant restoration was reported.[5] This study primarily affected premolars in women over 50, with crack development often occurring more than a year postimplant placement. Another study[6] validated these findings, identifying multiple cracked premolars with amalgam restorations in patients with multiple implants. Duqum et al[7] conducted a retrospective chart review to assess the impact of single posterior dental implants on the health of adjacent natural teeth. The study revealed a significantly higher rate of restorative treatments for teeth adjacent to implants compared with a control group. Han et al[8] further supported these findings through a retrospective study, linking implant-tooth root proximity or direct contact to increased complications in adjacent teeth. It is imperative to investigate the potential influence of adjacent dental implants on stress levels within natural teeth. Elevated stress may increase the risk of mechanical complications, particularly in premolars, as previously documented in clinical studies. A thorough evaluation of the level and distribution of stress in natural teeth adjacent to dental implants is currently lacking.

Finite element analysis (FEA) is a widely adopted engineering tool in dental applications.[9] [10] [11] It facilitates the analysis of stress, strain, and deformation in complex dental structures and restorative materials,[12] [13] [14] [15] which are often challenging to measure experimentally. Unlike in vitro studies, which are limited by factors such as material properties and experimental conditions, the finite element method allows for precise control and manipulation of variables, providing a deeper understanding of biomechanical phenomena. Moreover, finite element models can simulate complex stress circumstances and material behaviors that are difficult or impossible to duplicate in clinical settings. Additionally, FEA has been employed to analyze stress distribution in dental devices such as rotary files[16] and other medical instruments.[17] [18] [19] In addition to retrospective studies, FEA has been utilized to assess stress distribution in implant-related contexts. Falcinelli et al[20] conducted a literature review examining the applications of finite element modeling in implant restoration. Their study outlined the technique's key features, identified current limitations, and proposed directions for future research. Most finite element studies have focused on stress analysis within dental implants[21] [22] [23] or the surrounding bone.[24] [25] Tsouknidas et al[26] investigated the mechanical behavior of tooth-implant fixed partial dentures, demonstrating that stress and displacement are influenced by bone quality and implant-tooth connection stiffness. Wang et al[27] employed FEA to assess the biomechanical response of implants and adjacent teeth under varying bone quality conditions. Their findings indicated that bone density significantly impacts stress, strain, and displacement patterns in both dental components. Lencioni et al[28] utilized FEA to evaluate stress distribution within teeth, implants, and surrounding bone in tooth-implant fixed partial dentures. Their study examined the impact of various implant types on biomechanical responses. Additionally, FEA was employed to investigate stress distribution and maximum von Mises stress in cortical bone under different bone conditions and osseointegration levels.[29] A comprehensive analysis of the mechanical influence of a dental implant on the adjacent tooth and supporting tissues is undeniably crucial for preventing mechanical complications in the natural teeth following implant placement.

This study employed a finite element method to examine the maximum von Mises stress induced in a natural tooth adjacent to a natural tooth or a dental implant under different occlusal loading and interproximal space conditions. A maxillary second premolar adjacent to a natural first premolar (control group) or a first premolar dental implant (experimental group) were simulated and subjected to constant compressive forces, and the resulting von Mises stresses in the second premolar and surrounding bone were assessed.

Materials and Methods

This study employed FEA to investigate the mechanical behavior of a second premolar adjacent to either a natural first premolar or an implant. The maxillary first and second premolars served as the study model. The second premolar was subjected to various occlusal loading patterns to simulate chewing forces. To assess the impact of implant placement, two groups were defined: a control group with two natural premolars and an experimental group with a natural second premolar and an implant replacing the first premolar. Applied compressive forces were exclusively applied to the second premolar, and its resulting responses were analyzed. [Fig. 1A and B] illustrates the solid models for both study groups. Natural premolars within the jawbone for both the experimental and control groups were reconstructed from computed tomography (CT) scan images acquired using a three-dimensional cone-beam CT unit (J. Morita Mfg. Corp., Kyoto, Japan). Ethical approval for the use of tooth samples was obtained from the Human Research Ethics Committee of Thammasat University No. 3 (COE No. 074/2560). The simulated jawbone and a natural tooth, which comprises enamel, dentin, pulp, and the PDL, are shown in [Fig. 1C]. Mechanical responses of the second maxillary premolar in both the control and experimental groups were evaluated. The experimental group's first premolar was replaced with an implant consisting of a titanium fixture and a zirconia crown, as depicted in [Fig. 1D]. The solid model of a zirconia crown was created based on the enamel morphology of the natural first premolar, while the titanium fixture was designed using computer-aided design software, CATIA v.5 (Dassault Systèmes, Vélizy-Villacoublay, France). The zirconia crown's exterior replicated the natural first premolar's surface, ensuring identical tooth-to-tooth contacts in both groups. The titanium fixture, a 10 mm-long, tapered, screw-shaped post with diameters ranging from 5.5 mm to 3.0 mm, was designed to support the zirconia crown and integrate with the jawbone. Notably, unlike natural teeth, implants lack PDLs and directly osseointegrate with the surrounding bone.

Fig. 1 Solid model of (A) control group, (B) experimental groups, (C) natural tooth, and (D) implant.

Mesh Sensitivity Study

Solid models of the premolar pair were converted into finite element models using the commercial software Ansys (ANSYS v.2022 R1; ANSYS Inc., Canonsburg, Pennsylvania, United States). Tetrahedral elements were employed for mesh generation. A convergence study was performed to ensure that the solutions obtained were accurate and used reasonable computational resources. The study was performed by varying the mesh sizes in the analysis until the obtained solution negligibly changed from the previous analysis. Mesh sizes were defined as follows: jawbone, 5 mm; first premolar, 1 mm; second premolar, 0.3 mm; and contact area between premolars, 0.1 mm. The experimental and control groups comprised 617,657 nodes and 444,160 elements, and 598,089 nodes and 429,476 elements, respectively.

Contacts and Boundary Conditions

Interfaces between components of natural teeth (dentin–enamel) and implant (fixture–crown) were modeled as bonded contacts. A frictional contact, with a coefficient of 0.2, was applied to the interface between the first and second premolars.[30] [Fig. 2] illustrates the meshed models of the control specimen and associated boundary conditions. A finer mesh was utilized for the second premolar compared with the first to facilitate detailed analysis of the target tooth. Applied compressive forces were applied to the second premolar, and subsequent mechanical responses were observed. As illustrated in [Fig. 2], the specimen was fixed along both vertical cross-sections and the base of the jawbone. Specifically, with these boundary conditions, the jawbone was constrained from expanding or contracting in the distal–mesial direction but was allowed to deform in the buccal–lingual direction. The lower portions of the natural premolar and the implant were embedded in the jawbone, while the upper portions of the premolars were unconstrained and free to move under applied load. Additionally, the mesh was refined on the mesial surface of the second premolar and the distal surface of the first premolar for enhanced accuracy. This nonuniform meshing optimized computational efficiency while maintaining precision in critical regions. There were two types of models used in this study: one with an interproximal gap and one without. The interproximal gap between premolars was set at 50 µm.[31] [32] [33] In the gap-free model, premolars were positioned on the jawbone such that the first premolar's distal surface contacted the second premolar's mesial surface.

Fig. 2 Meshed model and boundary conditions of the control group. The specimen was fixed along both vertical cross-sections and the base of the jawbone, denoted as “fixed B.C.”

Applied Loads

To investigate stress in the second premolar, finite element models of both the control and experimental groups were subjected to applied compressive forces. [Fig. 3A] shows the load application points: positions 1, 2, and 3. Position 1 is on the lingual incline plane of the buccal cusp, position 2 is on the mesial marginal ridge, and position 3 is on the buccal incline plane of the palatal cusp. To mimic a physiologically relevant occlusal relationship, a 45-degree cuspal inclination, a common range observed in natural dentition,[34] was applied to the finite element model. Three positions of occlusal contacts were set according to a previous study.[35] To cover almost every event of occlusal contacts, the position was set in one, two, or combination of three points. In this study, various occlusal load combinations were applied to the second premolar. The first three cases involved applying a force of 200 N to each designated position individually.[36] [37] The next three cases involved applying two forces of 100 N each simultaneously at position 1 and position 2, position 1 and position 3, and position 2 and position 3. The final case involved applying a force of 66.67 N to all three positions simultaneously. We maintained a total combined force of 200 N for the loading cases on two or three positions to ensure that the loading conditions were comparable to those on a single position. Since this study investigated the adjacent implant's effect on second premolar failure, applied compressive forces aimed to deform the second premolar toward the implant. Load positions 1, 2, and 3 were subjected to forces with orientations θ and β ([Fig. 3B]). Line OA is the projection of force F onto the horizontal x-y plane. The orientation of line OA is represented by angle θ, while force F itself was rotated β degrees from the horizontal x-y plane. Therefore, using these geometric descriptions, we can represent the direction of force F with two parameters: θ and β. The applied force was also simulated on the occlusal angulation that was reported in nearly normal occlusion. The range of all angles corresponded to the potential events that could occur in clinical conditions.[34] [38] [39] [Table 1] lists the mechanical properties used in the FEA. Young's modulus and Poisson's ratio for tooth components and the implant are included. Enamel and dentin strengths were also used to assess second premolar safety. All model components were assumed to be homogeneous, isotropic, and linearly elastic.

Table 1 Mechanical properties of tooth's structures and dental materials

Components	Modulus (GPa)	Poisson's ratio	Flexural strength (MPa)
Enamel[47] [48]	84.1	0.2	400
Dentin[49] [50]	18.6	0.31	200
Pulp[51]	0.002	0.45	−
PDL[49]	0.0689	0.4	−
Cortical bone[49]	13.7	0.3	−
Cancellous bone[49]	1.37	0.3	−
Titanium[52]	110	0.35	−
Zirconia[53]	210	0.3	−

Abbreviation: PDL, periodontal ligament.

Fig. 3 The (A) positions and (B) direction of applied forces on the second premolar. In (A), position 1 is on the lingual incline plane of the buccal cusp, position 2 is on the mesial marginal ridge, and position 3 is on the buccal incline plane of the palatal cusp. In (B), force F refers to applied compressive force. Point O is the position of applied force, which can be position 1, 2, or 3. Line OA is the projection of force F onto the horizontal x-y plane. The orientation of line OA is represented by angle θ, while force F itself was rotated β degrees from the horizontal x-y plane.

Mechanical Responses

In addition to von Mises stress on the second premolar, we investigated the safety factor, displacement, and reaction force. As each component of the tooth exhibits varying strengths, the safety factor indicates proximity to failure of each component. Based on the von Mises failure criterion,[40] the safety factor is the ratio of the material's yield strength to the maximum von Mises stress. The safety factor below one suggests potential component failure. Components with lower safety factors are more prone to failure. A high safety factor implies that a component can withstand additional loading without failing. Maximum displacement of the second premolar was also determined and compared between the control and experimental groups. The linear displacement of each node on the finite element models of the second premolar can be determined during the FEA. Then, the displacement of each node was compared, and the maximum displacement was determined and compared. Another parameter of interest was the reaction force exerted on the second premolar by either the natural first premolar or the implant during contact. This reaction force, considered an applied load on the second premolar, was determined through FEA based on the hypothesis that the magnitude of the contact force between two surfaces prevents penetration between both surfaces.[41]

Results

To assess the implant's effect on adjacent tooth failure, we performed stress analysis on the second premolar. [Fig. 4] shows von Mises stress distribution for both groups under 200 N loads at positions 1, 2, and 3. Force directions, defined by angles θ and β, were θ = 30 degrees and β = 45 degrees for positions 1 and 2, and θ = –30 degrees and β = 135 degrees for position 3. Although the force direction for loadings at positions 1 and 2 were not numerically identical to those at position 3, they were deemed comparable given that position 3 was situated on the opposite side of the tooth's central groove. Maximum von Mises stress consistently occurred at the interproximal contact between both premolars in all cases. [Fig. 4] illustrates von Mises stress distribution on an x-z plane cross-section at the second premolar's maximum stress point. Additionally, the figure shows stress distribution on the second premolar's mesial surface. While stress distribution patterns were comparable between the control and experimental groups under identical loading, the experimental group consistently exhibited higher maximum von Mises stress values, as listed in the figure.

Fig. 4 Distribution of von Mises stress on the models subjected to a force of 200 N at (A) position 1, (B) position 2, and (C) position 3.

Direction of Force

The maximum von Mises stress, observed on the second premolar's mesial surface in both groups, indicates the severity of the force applied to the tooth. This section plots the second premolar's maximum von Mises stress against the applied force direction at positions 2 and 3. With β fixed at 45 and 135 degrees for positions 2 and 3, respectively, forces were compressive, directed 45 degrees to the horizontal plane, targeting the buccal and lingual cusps. [Fig. 5A] shows how maximum von Mises stress varies with force direction θ. The effect of force direction with respect to the horizontal plane (angle β) on the maximum von Mises stress was also examined. The force angle θ was fixed at 30 degrees for position 2 and –30 degrees for position 3. [Fig. 5B] shows the maximum von Mises stress for forces directed by angle β, ranging from 0 to 90 degrees at position 2 and 180 to 90 degrees at position 3.

Fig. 5 Maximum von Mises stress on the second premolar with a compressive force at position 2 (Pos. 2) and 3 (Pos. 3) in the direction of (A) β = 45 and 135 degrees and (B) θ of 30 and –30 degrees, respectively

Maximum von Mises Stress

This section investigated maximum von Mises stress in the second premolar for both the control and experimental groups, with and without interproximal gaps. Forces at positions 1 and 2 were set at θ = 30 degrees, β = 45 degrees, while position 3 used θ = –30 degrees, β = 135 degrees. Applied compressive forces were applied individually at positions 1, 2, or 3, or in combination of two or three positions according to the details described above. Maximum von Mises stress consistently occurred at the interproximal contact in all cases of loading. [Fig. 6] shows maximum von Mises stress values in the second premolar for various load conditions.

Fig. 6 Maximum von Mises stress (MPa) of the second premolar under a total compressive force of 200 N in the control and experimental groups as a function of the presence or absence of the interproximal gap and the positions of applied force.

Safety Factor

The von Mises criterion was employed to assess the likelihood of failure in dentin and enamel by comparing calculated von Mises stresses to material strengths. This study calculated safety factors for dentin and enamel in both the control and experimental groups. Enamel consistently exhibited the lowest safety factors. [Fig. 7] presents safety factor distributions for second premolars, revealing higher values in control groups compared with experimental groups. Additionally, models without interproximal gaps demonstrated higher safety factors than those with gaps.

Fig. 7 Safety factor of the second premolar under a total compressive force of 200 N in the control and experimental groups as a function of the presence or absence of the interproximal gap and the positions of applied force.

Displacement

FEA also enables the determination of displacement at any point within the model. This section of the study focused on the displacement of the second premolar as an indicator of tooth movement. [Fig. 8] presents the maximum displacement observed at the buccal cusp apex for all cases. Control groups exhibited greater maximum displacement compared with their experimental counterparts. Additionally, models without interproximal gaps demonstrated lower displacements than those with gaps.

Fig. 8 Maximum displacement of the second premolar under a total compressive force of 200 N in the control and experimental groups as a function of the presence or absence of the interproximal gap and the positions of applied force.

Reaction Force and Contact Area

Contact between the second premolar and either the natural first premolar or the implant generates reaction forces on the second premolar, which act as loads applied to the second premolar. The reaction forces for both models under various loading conditions are illustrated in [Fig. 9]. In all loading scenarios, total reaction forces were higher in the experimental group compared with the control group. Similarly, reaction forces were greater in models without an interproximal gap than in those with a gap. In addition to reaction force, the total contact area between both teeth can be determined from the FEA, which is presented in [Table 2].

Table 2 Contact area in mm² between the teeth of the models with and without an interproximal gap

Loading position	With gap		Without gap
	Control group	Experimental group	Control group	Experimental group
1	0.186	0.260	1.275	1.686
2	0.222	0.332	1.668	2.089
3	0.208	0.286	1.261	1.276
1 + 2	0.208	0.295	1.448	2.132
1 + 3	0.231	0.311	1.904	2.144
2 + 3	0.245	0.340	1.925	1.805
1 + 2 + 3	0.236	0.328	1.851	2.238

Fig. 9 Reaction force on the second premolar under a total compressive force of 200 N in the control and experimental groups as a function of the presence or absence of the interproximal gap and the positions of applied force.

Stress in the Bone

The presence of an implant influenced stress distribution not only in the adjacent tooth but also in the surrounding jawbone. [Fig. 10] illustrates stress distribution in the alveolar bone surrounding both natural premolars (control group) and the second premolar and the implant (experimental group) under loading at positions 1, 2, and 3. Yellow arrows indicate regions of maximum von Mises stress in the alveolar bone around premolars and the implant, with corresponding stress values. The experimental group exhibited lower alveolar bone stresses compared with the control group.

Fig. 10 Distribution of von Mises stress within the alveolar bone with a force of 200 N applied on the second premolar at (A) position 1, (B) position 2, and (C) position 3.

Discussions

Previous studies have reported increased mechanical complications and treatment rates for natural teeth adjacent to a dental implant.[4] [5] [6] [7] This study employed FEA and included two groups of teeth: a control group with two natural premolars and an experimental group with a natural second premolar and an implant replacing the first premolar. The first part of the study investigated the effect of force direction by applying forces in various directions to the second premolar in both the control (coded as Control in [Fig. 5]) and experimental (coded as Exp. in [Fig. 5]) groups, with a 50-µm interproximal gap. Maximum von Mises stress in the second premolar was observed, as shown in [Fig. 5]. The second premolar did not contact the first premolar or the implant when the force was applied at an angle θ greater than 75 degrees or less than –75 degrees (for forces applied at position 3). Similarly, forces applied vertically, β = 90 degrees, resulted in no contact between the teeth, and the maximum stress in the second premolar was equal for both groups, as shown in [Fig. 5B]. Therefore, contact between adjacent teeth affected the stress experienced by the second premolar. For the case of fixed β in [Fig. 5A], stress was maximum if the force was applied in the direction of θ = 0 since the second premolar was directly compressed toward the first premolar. The von Mises stress in the second premolar was consistently higher in the experimental groups compared with the control groups when tooth contact occurred. However, the stress distribution pattern in the second premolar was similar for both the experimental and control groups, as shown in [Fig. 4]. The maximum von Mises stress was observed on the contact surface of the enamel of the second premolar. This suggests that the presence of a dental implant could increase the risk of cracked or fractured adjacent natural teeth, as previously reported in patients undergoing dental implant therapy.[4] [5] [6] [7] Additional research is required to validate this hypothesis.

Next, maximum von Mises stress was compared between models with and without an interproximal gap, subjected to loading at various positions on the occlusal surface of the second premolar. Stress levels were higher in models with a gap compared with those without a gap in all cases, as shown in [Fig. 6]. This observation is likely influenced by the size of the contact area between the teeth. As illustrated in [Fig. 8], models with a gap exhibited greater movement compared with those without a gap, with maximum displacement occurring at the buccal cusp tip. Consequently, models with a gap tended to rotate until the mesial surface of the second premolar crown contacted the crown of the natural or implanted teeth. This movement likely resulted in a smaller contact area between the natural teeth in models with a gap compared with those without a gap, where full contact existed prior to loading. This hypothesis is supported by the contact area data presented in [Table 2] from the FEA analysis. Safety factor values, as illustrated in [Fig. 7], indicate that all models without a gap maintained an acceptable safety margin under the 200 N load, while all experimental groups with a gap, except for the case of loading at position 3, failed at this load level. This indicated that, compared with natural teeth, the presence of interproximal space between a dental implant and adjacent natural teeth significantly increased the maximum von Mises stress experienced by the natural teeth. It is possible that this heightened stress level exceeding the tooth structures' yield strengths could increase the risk of crack formation and propagation,[42] underscoring the importance of diligent postimplant monitoring. Further studies are needed to confirm this hypothesis.

Maximum von Mises stress in all the experimental groups consistently exceeded those of the control groups, as illustrated in [Fig. 6]. Models subjected to buccal loading (positions 1, 2, and 1 and 2) exhibited similar maximum stress values. In contrast, lingual loading (position 3) resulted in lower maximum stress on the second premolar compared with buccal loading. This reduction in stress is likely due to the buccal tooth contact and the lingual application of force at position 3. This force orientation minimizes direct force transmission to the second premolar, leading to lower stress values for the position 3 loading condition. When loading was applied to both sides of the central groove (positions 1 and 3, 2 and 3, or 1, 2, and 3), the maximum stress values were highly comparable. Moreover, maximum stress in the experimental group closely approximated that of the control group for models without an interproximal gap. Safety factors for these conditions were approximately 2. Therefore, except for models without a gap subjected to loading on both sides of the central groove, stress levels in the experimental groups were significantly higher than those in the control groups. The results demonstrated that the direction of occlusal loading affected the stress levels experienced by natural teeth adjacent to dental implants. The results highlighted the importance of thorough patient evaluation, treatment planning, and maintenance for dental implant restoration to prevent potential mechanical complications to surrounding natural teeth, such as tooth fracture and restoration dislodgement.

The reduced displacement ([Fig. 8]) and higher reaction forces ([Fig. 9]) of the second premolar in the experimental group compared with the control group are likely attributable to the greater rigidity of the implant relative to the natural first premolar. In the control group, the natural first premolar is supported by the PDL, a compliant connective tissue with a lower elastic modulus. This allows for greater tooth mobility and reduced resistance to force compared with the rigidly fixed implant in the experimental group. Consequently, when loaded, the second premolar in the experimental group exhibited less displacement and increased reaction force relative to the control group.

A comparative analysis of the stress distribution in the alveolar bone surrounding the natural teeth and the dental implant was conducted for both the control and experimental groups ([Fig. 10]). The results indicated lower von Mises stress levels in the bone at both positions in the experimental group. This lower bone stress can be attributed to the distinct characteristics of the implant–bone interface. A dental implant exhibits significantly less mobility when subjected to occlusal forces, resulting in reduced bone displacement and a corresponding decrease in stress concentration. However, the PDL houses proprioceptors, which facilitate movement and positional awareness, as well as mechanoreceptors responsible for tactile, pain, and pressure sensations. These sensory receptors collectively contribute to the regulation of muscular activity and occlusal forces, thereby safeguarding the teeth and alveolar bone from excessive loading and subsequent bone damage.[43] It is thus possible that alveolar bone resorption at the natural tooth adjacent to a dental implant might be associated with the biological cause, not the mechanical cause. Additional research is, however, required to validate this hypothesis.

Previous studies on the biomechanics of simulated dental implants and adjacent natural teeth using the finite element method have provided insight into our understanding of the biomechanics of dental implants and surrounding bone[20] and have contributed to the development of more effective restoration of the teeth adjacent to dental implants.[44] [45] Using FEA, it has been shown that lateral contact forces between a dental implant and its adjacent teeth did not significantly affect the dental implant.[46] Still, such forces' effect on the adjacent natural teeth is not fully understood. Dai and Lu[45] examined the impact of the contact area between a first molar implant and its adjacent teeth. Their findings revealed that a larger contact area effectively dispersed the implant's load, particularly mitigating the stress induced by lateral forces when the contact area was smaller. The impact of applied forces to implant prostheses on the supporting bone of the implant and adjacent teeth, which depends on bone quality,[27] has also been shown. However, very little is known about the biomechanical influence of a dental implant on the adjacent natural teeth. FEA used in the present study has shown for the first time that compared with a natural tooth, a dental implant differentially increases stress on the adjacent natural teeth, depending on the occlusal force direction and position applied and the presence of interproximal space. The findings underscore the importance of comprehensive intraoral and dental examinations, along with meticulous treatment planning prior to dental implant therapy. Particular attention should be directed toward the orientation and positioning of occlusal forces on natural teeth adjacent to the edentulous ridge intended for implant placement. Postimplant restoration maintenance is recommended to ensure proper interproximal contact between dental implants and natural teeth, thereby minimizing stress within the adjacent natural dentition and mitigating potential mechanical complications.

Despite the capability of FEA to simulate and analyze complex biomechanical processes, it is essential to acknowledge the limitations of this analytical technique used in the present study. Dental tissues like enamel, dentin, and PDL exhibit varying degrees of heterogeneity and anisotropy. Accurately determining and inputting these properties into FEA models can be challenging. In addition, simplified simulated models may not fully capture the complex mechanical behavior of dental tissues under certain loading conditions. This can impact the accuracy of the results, especially when analyzing complex structures like the periodontium. While FEA can provide valuable insights into stress distribution and deformation patterns, it is crucial to validate these computational findings with rigorous, well-powered clinical studies to establish a strong correlation between simulated and actual clinical outcomes. Moreover, a simplified implant fixture design with a single diameter and length, as well as a single maxillary premolar type, was employed for this study. While these findings provide valuable insights, further research is necessary to evaluate the applicability of these results to a broader range of implant fixture designs and tooth types. In addition, given the individual nature of occlusal relationships, the selected range of occlusal schemes and parameters for normal occlusion used in the present study may not directly apply to malocclusion or parafunctional habits. Therefore, the interpretation of these results should be made with caution, acknowledging this limitation.

Conclusion

Based on the study's findings and limitations, the following conclusions can be drawn:

1. When a dental implant is present, the stress in the adjacent natural teeth is increased.

2. The presence of interproximal space between a natural tooth and a dental implant intensifies stress in the natural tooth.

3. The position and direction of occlusal force contact applied to a natural tooth adjacent to a natural tooth or a dental implant influence the stress in the loaded tooth.

4. The results emphasize the importance of careful patient evaluation, treatment planning, and maintenance for dental implant restoration to minimize potential complications to the surrounding natural teeth.

Conflict of Interest

None declared.

Acknowledgment

The study was supported by the Thammasat University Research Unit in Mineralized Tissue Reconstruction, Thailand.

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Artikel online veröffentlicht:
20. Januar 2025