Load response of the natural tooth and dental implant: A comparative biomechanics study

Abstract

Purpose: While dental implants have displayed high success rates, poor mechanical fixation is a common complication, and their biomechanical response to occlusal loading remains poorly understood. This study aimed to develop and validate a computational model of a natural first premolar and a dental implant with matching crown morphology, and quantify their mechanical response to loading at the occlusal surface.

Materials and methods: A finite-element model of the stomatognathic system comprising the mandible, first premolar and periodontal ligament (PDL) was developed based on a natural human tooth, and a model of a dental implant of identical occlusal geometry was also created. Occlusal loading was simulated using point forces applied at seven landmarks on each crown. Model predictions were validated using strain gauge measurements acquired during loading of matched physical models of the tooth and implant assemblies.

Results: For the natural tooth, the maximum vonMises stress (6.4 MPa) and maximal principal strains at the mandible (1.8 mε, -1.7 mε) were lower than those observed at the prosthetic tooth (12.5 MPa, 3.2 mε, and -4.4 mε, respectively). As occlusal load was applied more bucally relative to the tooth central axis, stress and strain magnitudes increased.

Conclusion: Occlusal loading of the natural tooth results in lower stress-strain magnitudes in the underlying alveolar bone than those associated with a dental implant of matched occlusal anatomy. The PDL may function to mitigate axial and bending stress intensities resulting from off-centered occlusal loads. The findings may be useful in dental implant design, restoration material selection, and surgical planning.

Keywords: Biomechanical model; Dental occlusion; Finite element analysis; Periodontal ligament; Premolar.

Fig. 1. Schematic diagram of tooth-loading experiment (A) and the coordinate system employed in modelling and experiments (B). During testing, a flat-ended end-effector indenter applied compressive load to the highest point of the buccal cusp. Two triaxial strain gauges rosettes were positioned on the mandible immediately below the tooth on both the buccal and lingual sides. The mandible was potted in a fixture using dental cement and further secured with two stainless steel screws. For the tooth assembly coordinate system, the x-y plane (dashed red line) was coincident with the four corner points at the base of the mandible. The x-axis pointed laterally in a direction parallel to the centreline of the mandible base, the y-axis pointed anteriorly, and the z-axis was perpendicular to the x- and y-axes and directed toward the highest point on the buccal cusp.

Fig. 2. Position of point loads applied to the landmarks on the occlusal surface in finite element model simulations, including the buccal cusp (yellow), cuspal inclination (green), central groove (pink), mesial marginal ridge (black), distal marginal ridge (red), mesial fossa (brown), distal fossa (purple) shown on the lingual side of tooth (A), right view (B) and left view (C).

Fig. 3. Force-displacement curves measured experimentally and predicted by the finite element models for the natural and implant tooth assemblies (A), principal strains measured experimentally for the natural tooth on the lingual and buccal sides of the mandible compared to strains calculated using the finite element model (B), and principal strains measured experimentally for the dental implant on the lingual and buccal sides of the mandible compared to strains calculated using the finite element model (C).

Fig. 4. Contour plots of von Mises stress distributions predicted for the natural tooth (A) and dental implant (B). Data are given for occlusal loading applied at the mesial fossa, distal fossa, buccal cusp, central groove, cuspal inclination, mesial marginal ridge, and distal marginal ridge.

Fig. 5. Maximum von Mises stresses (A), maximum principal strains (B) and minimum principal strains (C) predicted at the mandible for the natural tooth and dental implant assembly. Data are shown for occlusal loading applied at the mesial fossa, distal fossa, buccal cusp, central groove, cuspal inclination, mesial marginal ridge, and distal marginal ridge.

Fig. 6. Micro-CT image of natural tooth from a cadaveric specimen (A), 3-dimensional reconstruction of entire rightside of the mandible from micro-CT images (B), and resulting density map for the natural tooth (C) and prosthetic tooth (D).