A three-dimensional finite element study on anterior laminate veneers with different incisal preparations

Stress distribution on teeth restored with veneers using various incisal preparation designs: A 3D finite element analysis study

STATEMENT OF PROBLEM

The type of veneer preparation is often chosen according to the patient's tooth structure and occlusion. Taking biomechanics into account in this decision-making process provides the clinician with more technical information on how to improve the clinical longevity of restorations. However, biomechanical analyses of veneer preparation designs are sparse.

PURPOSE

The purpose of this 3-dimensional (3D) finite element analysis with microcomputed tomography (µCT) data obtained from realistic models was to assess the influence of different preparations for ceramic and composite resin veneers on restoration and resin layer stress distribution.

MATERIAL AND METHODS

Four replicas of a central incisor were printed and prepared for laminate veneers with 4 different incisal edge designs: shoulder (SH), palatal chamfer (PC), palatal chamfer and oblique fracture involving the distal angle (OF-PC), and palatal chamfer involving horizontal incisal fracture (IF-PC). After fabrication and cementation of the veneers, the restored replicas were assessed with µCT, and 3D finite element models were built. A 100-N load was applied on the palatal surface at 60 and 125 degrees relative to the longitudinal axis. Maximum principal stress and stress distribution on the veneers, cement layer, and tooth structure were calculated and analyzed.

RESULTS

The SH preparation exhibited better stress distribution than the PC preparation, and the cement layer and the veneer were subjected to lower stress. The IF-PC preparation had better stress distribution than the OF-PC. The shoulder and IF-PC showed higher stress on laminate veneers, but lower stress on the cement layer. Ceramic veneers exhibited lower stress than composite resin veneers.

CONCLUSIONS

The different incisal preparations for laminate veneers influenced stress distribution on restorations and on the resin cement layer. The shoulder type preparation showed better stress distribution and the composite resin veneers showed unfavorable results compared with the ceramic veneers.

Effect of incisal preparation design on the fracture strength of monolithic zirconia-reinforced lithium silicate laminate veneers

PURPOSE

This study aimed to assess the fracture resistance of monolithic zirconia-reinforced lithium silicate laminate veneers (LVs) fabricated on various incisal preparation designs.

MATERIALS AND METHODS

Sixty maxillary central incisors with various preparation designs were 3D-printed, 15 each, including preparation for: (1) LV with feathered-edge design; (2) LV with butt-joint design; (3) LV with palatal chamfer; and (4) full-coverage crown. Restorations were then designed and manufactured from zirconia-reinforced lithium silicate (ZLS) following the contour of a pre-operation scan. Restorations were bonded to the assigned preparation using resin cement and following the manufacturer's instructions. Specimens were then subjected to 10,000 thermocycles at 5 to 55°C with a dwell time of 30 s. The fracture strength of specimens was then assessed using a universal testing machine at a crosshead speed of 1.0 mm/min. One-way ANOVA and Bonferroni correction multiple comparisons were used to assess the fracture strength differences between the test groups (α = 0.001). Descriptive fractographic analysis of specimens was carried out with scanning electron microscopy images.

RESULTS

Complete coverage crown and LV with palatal chamfer design had the highest fracture resistance values (781.4 ± 151.4 and 618.2 ± 112.6 N, respectively). Single crown and LV with palatal chamfer had no significant difference in fracture strength (p > 05). LV with feathered-edge and butt-joint designs provided significantly (p < 05) lower fracture resistance than complete coverage crown and LV with palatal chamfer design.

CONCLUSION

The fracture resistance of chairside milled ZLS veneers was significantly influenced by the incisal preparation designs tested. Within the limitation of this study, when excessive occlusal forces are expected, LV with palatal chamfer display is the most conservative method of fabricating an indirect restoration.

The Influence of a Novel, Crenelated Design of CAD-CAM Ceramic Veneers on the Debonding Strength

(1) Background: Aesthetic dentistry has become one of the most dynamic fields in modern dental medicine. Ceramic veneers represent the most appropriate prosthetic restorations for smile enhancement, due to their minimal invasiveness and highly natural appearance. For long-term clinical success, accurate design of both tooth preparation and ceramic veneers is of paramount importance. The aims of this in vitro study were to assess the stress in anterior teeth restored with Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) ceramic veneers and compare the resistance to detachment and the fracture of ceramic veneers prepared using two different designs. (2) Methods: Sixteen lithium disilicate ceramic veneers were designed and milled using the CAD-CAM technology and divided into two groups according to the preparations (n = 8): Group 1, conventional (CO), with linear marginal contour and Group 2, crenelated (CR), the latter with our novel (patented) sinusoidal marginal design. All samples were bonded to anterior natural teeth. The mechanical resistance to detachment and fracture was investigated by applying bending forces on the incisal margin of the veneers in order to determine which type of preparation leads to better adhesion. An analytic method was employed, as well, and the results of the two approaches were compared. (3) Results: The mean values of the maximum force recorded at the veneer detachment were 78.82 ± 16.55 N for the CO group and 90.20 ± 29.81 N for the CR group. The relative increase, equal to 14.43%, demonstrated that the novel CR tooth preparation provided higher adhesive joints. In order to determine the stress distribution within the adhesive layer, a finite element analysis (FEA) was performed. The statistical t-test showed that the mean value of the maximum normal stresses is higher for the CR-type preparations. (4) Conclusions: The patented CR veneers represent a practical solution to augment the adhesion and mechanical properties of ceramic veneers. The obtained results demonstrated that CR adhesive joints triggered higher mechanical and adhesive forces, which subsequently led to a higher resistance to detachment and fracture.

Biomechanical Behavior Evaluation of Resin Cement with Different Elastic Modulus on Porcelain Laminate Veneer Restorations Using Micro-CT-Based Finite Element Analysis

The aim of this study is to evaluate the biomechanical behavior of the porcelain laminate veneer restorations (PLV) of the maxillary central incisor luted with two types of resin cements having different incisal preparations: butt joint and palatal chamfer. Biomechanical analyses were performed using the micro-CT-based finite element models, and von Mises stress and strain values of the PLV, resin cement, adhesive layer, and tooth structure were computed. The PLV with butt joint preparation showed larger stress values than those of restored with palatal chamfer preparation, regardless of the elasticity of the cement and loading conditions. An increase in the elasticity modulus of the resin cement induced slightly larger stresses on the adhesive layer, tooth tissues, and restorative materials. Overall, this study demonstrates the role of the preparation design and luting materials on the mechanical behavior of the PLV restorations and discusses the potential failure mechanisms of the PLV restorations under different loading mechanisms.

Comparison of Two Types of Preparation for Laminate Veneer with Three Types of All-Ceramic Materials

OBJECTIVE

 The objective of this study was to compare types of veneer preparations and their combination with three materials.

MATERIALS AND METHODS

 Two finite element models were specially prepared used representing window and wrap around preparation for veneers. The "central incisor" tooth geometry was acquired using a laser scanner, and then its surface was adjusted to form a solid model prior to the removal of each preparation separately. Three materials (Lava Ultimate, IPS e-max, and Celtra) were tested in combination with the preparation type. Bone geometry was simplified as two coaxial cylinders in all models. Each model was subjected to two loading conditions of occlusion (edge-to-edge bite and normal bite).

STATISTICAL ANALYSIS AND RESULTS

 It was observed that cortical, cancellous bone, and periodontal ligament are insensitive to preparation or materials. Their stresses and deformation were within physiological limits. Significant changes appeared on the central incisor tooth structure, cement layer, and veneer layer stresses and deformations under loading cases.

CONCLUSIONS

 Edge-to-edge bite stresses are severe with window-type preparation, and normal bite did not show any critical values on tooth structure, cement layer, or veneer layer. Veneer layer finish line and its contact with the cement layer and tooth structure play a role in the loading transfer mechanism. Preparation type alters the values of stresses on tooth structure, cement, and veneer layers. With window preparation, extreme stresses appear at finish line, while stresses appear under the loading site with wrap around preparation. Veneer and cement layers withstand the load energy with wrap around preparation and reduce tooth structure stresses. Thus, the lifetime of veneer and cement layers might be longer with window preparation.

Marginal discrepancy and load to fracture of monolithic zirconia laminate veneers: The effect of preparation design and sintering protocol

To investigate and analyze the impact of teeth preparation designs and sintering protocol on marginal fit and fracture resistance of monolithic translucent zirconia laminate veneers. A total of 40 extracted intact human maxillary central incisors were assigned into 4 groups (n=10/each group) to investigate 2 variables: (1) the design of tooth preparation (a 1.5 mm incisal reduction with or without palatal chamfer) and (2) the two different sintering programs used for translucent zirconia restoration (standard or speed sintering procedure). Marginal discrepancy was evaluated using a digital microscope. The specimens were loaded to failure in the compression mode, using a universal testing machine with a crosshead speed of 0.5 mm/min. Marginal adaptation of monolithic translucent zirconia laminates are affected by both tooth preparation design and sintering protocol. However, resistance to fracture of translucent zirconia laminates has affected mainly by sintering procedure regardless the teeth preparation design used.

Comparison of conventional ceramic laminate veneers, partial laminate veneers and direct composite resin restorations in fracture strength after aging

OBJECTIVES

The objectives of this study were to test the fracture strength in vitro of laminate veneers, partial laminate veneers and composite restorations after aging and analyze the failure mode.

METHODS

Forty extracted, sound human teeth were selected and divided into four groups: 1) Control group (CG); 2) Conventional Laminate Veneer (CLV); 3) Partial Laminate Veneer (PLV); 4) Direct Composite Resin (DCR). Laminate veneer preparations with incisal overlap were made in group CLV whereas only incisal preparations were made with a 1 mm bevel in group PLV and DCR. The indirect restorations were luted with a resin composite and the DCR group was restored with a direct resin composite restoration. The restored teeth were subsequently aged by thermocycling (20.000 cycles, 5-55 degrees C). Subsequently, the fracture strength was tested by a load to failure test at 135° on the incisal edge. A failure analysis was performed using light microscopy. The results were analyzed using Shapiro-Wilk and Kruska-Wallis test.

RESULTS

After thermocycling, one sample from group CLV presented a premature adhesive failure and was excluded. Three restorations from groups PLV and DCR presented small cracks but were taken to the fracture test. After aging mean fracture load + SD (N) were: Group DCR (n = 10): 385 ± 225; Group CG (n = 10): 271 ± 100; Group PLV (n = 10): 266 ± 69; Group CLV (n = 9): 264 ± 66. Fracture strength means from groups CLV and PLV did not differ statistically from each other nor from control (p = 0.05). In the group CLV the root fracture was the most occurring fracture. In groups PLV and DCR, material cohesive failures and a mix (adhesive, tooth and material cohesive) failures were most observed.

SIGNIFICANCE

This in vitro study showed for the first time that partial laminate veneers can exhibit fracture strength values similar to direct composite restorations or conventional ceramic laminate veneers. All three restorative procedures presented clinically acceptable values of fracture strength. Even though three samples from groups PLV and three from DCR presented small cracks after thermocycling, these cracks do not appear to have a negative effect on the fracture strength.

Stress distribution within the ceramic veneer-tooth system with butt joint and feathered edge incisal preparation designs

OBJECTIVE

This in-vitro study aims to study the stress distribution within the ceramic veneer-tooth system with two incisal preparation designs-butt joint (BJ) and feathered edge (FE), and to correlate these findings to the results of our previous published load-to-failure study.

METHODS

Six photoelastic models were fabricated with an epoxy resin material (West System 105 Epoxy Resin/205 Fast Hardener, West System) to represent BJ and FE preparation configurations at 0° and 20° loading angulations. Lithium disilicate ceramic veneers (IPS e.max CAD, Ivoclar Vivadent) were bonded to the BJ and FE photoelastic models using resin cement (IPS Variolink Esthetic, Ivoclar Vivadent). Each model was loaded using an Instron Universal Testing Machine at the incisal edge at a cross-head speed of 0.25 mm/min till 100 N.

RESULTS

BJ photoelastic model had more uniform distribution compared with FE photoelastic models under 0° and 20° loading angulations.

CONCLUSION

Parallel to the results of our earlier load-to-failure published study, both incisal preparation designs affect stress distribution within the ceramic veneer-tooth system. BJ photoelastic model demonstrated a more uniform distribution compared with FE photoelastic model.

CLINICAL SIGNIFICANCE

BJ incisal preparation design has more uniform stress distribution than FE preparation design within the ceramic veneer-tooth system.

Is the assumption of linear elasticity within prosthodontics valid for polymers? -An exemplary study of possible problems

As shown in previous studies within other scientific fields, the material behavior of polymethyl methacrylate (PMMA) is viscoelastic-viscoplastic. However, in dental biomaterial science it is mostly considered as linear elastic or elastic-plastic. The aim of the present study was to evaluate, whether the assumption of elastic or elastic-plastic material behavior for PMMA is a practicable simplification or a potential source of error, especially considering clinical loading conditions. Telio-CAD was tested in three-point bending tests with different test velocities to examine the material behavior at different initial loading rates. Additionally, a dynamic-mechanical-thermal-analysis at different frequencies and temperatures was used. Here, a significant influence of loading rate and temperature as well as stress relaxation and creep were observed. To describe the rate-dependency of the elastic modulus, a new model was created, from which the elastic modulus can be calculated with a given strain rate. This model was validated using linear elastic finite element analysis.

Effect of luting materials, presence of tooth preparation, and functional loading on stress distribution on ceramic laminate veneers: A finite element analysis

STATEMENT OF PROBLEM

How the polymerization shrinkage, loading, and mechanical properties of luting materials affect the shrinkage and functional stresses in ceramic laminate veneers (CLVs) with and without tooth preparation is unclear.

PURPOSE

The purpose of this finite element analysis (FEA) study was to evaluate the effect of the polymerization shrinkage, functional loading, and mechanical properties of different luting materials on the stresses in ultrathin 0.3-mm CLVs with and without tooth preparation.

MATERIAL AND METHODS

Three resin cements, RelyX Veneer (RV), Allcem Veneer APS (AV), Variolink Esthetic LC (VE), and 1 flowable composite resin, Tetric N-Flow (TF), were tested for post-gel shrinkage (Shr), Knoop hardness (KHN), elastic modulus (E), compressive strength (CS), and diametral tensile strength (DTS). IPS e.max CAD disks of 0.3-mm thickness were made for simulating the effects of light attenuation. Eight 2-dimensional finite element models (Marc-Mentat) of a maxillary central incisor were generated to evaluate the polymerization shrinkage stress of different materials for luting 0.3-mm CLVs with or without tooth preparation and the stress during functional loading by using a modified von Mises criterion (mvm). Collected data from Shr, KHN, and E were submitted to 2-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

Light attenuation by the 0.3-mm ceramic disk did not significantly affect the E values, but Shr was significantly lower in VE (26%) and TF (35%). TF had lower volumetric Shr (%) when interposing a ceramic disk (0.31%). Both tested tooth preparation options showed similar stress distributions from polymerization shrinkage or functional loading, with higher stress concentration on the incisal edge and also on the cervical surface. The model featuring tooth preparation and RV resin cement had the highest and VE the lowest stress levels.

CONCLUSIONS

The flowable composite resin had similar mechanical properties as the resin cements. The stress distribution from shrinkage and functional loading was similar for both techniques with or without tooth preparation.

Influence of Preparation Depth and Design on Stress Distribution in Maxillary Central Incisors Restored with Ceramic Veneers: A 3D Finite Element Analysis

PURPOSE

To evaluate the influence of different preparation designs and depths on the stress field developed in maxillary central incisors restored with veneers made with different ceramic materials using finite element analysis (FEA).

MATERIALS AND METHODS

A linear static three-dimensional finite element analysis model was used with the aid of reverse engineering to develop digital models of maxillary central incisors restored with ceramic veneers, according to two different preparation depths (thin vs deep) and two different preparation designs (feather edge vs butt joint). Three ceramic systems were tested: (i) feldspathic porcelain, (ii) heat pressed glass ceramic IPS Empress 2 (Ivoclar Vivadent AG), and (iii) heat pressed glass ceramic IPS e.max-Press (Ivoclar Vivadent AG). Each model was subjected to a compressive force of 200N applied to the palatal surface 2 mm below the incisal edge. The longitudinal axis of the restored tooth formed an angle of 130^o with the direction of the force. The biomechanical behavior of the different models was examined according to the von Mises stress criterion. Statistical analysis was performed using nonparametric confidence interval estimation using bootstrapping.

RESULTS

The maximum observed stress values were calculated and found to be similar between prepared and intact teeth. The cervical margin of the veneers displayed the highest von Mises stress values. Irrespectively of the depth and preparation design, the biggest von Mises stress values were observed at the veneer structures with the following order: (i) IPS Empress 2, (ii) IPS e.max-Press, (iii) feldspathic (p = 0.001). Preparation depth resulted in statistically significant differences (p = 0.001) in the stress distribution in the majority of tested structures. As the preparation depth was increased, the stresses within the veneer structure and the tooth structures were decreased. No statistically significant differences were detected in the stresses among the different restored models, when the preparation design was considered.

CONCLUSIONS

This FEA study suggests that ceramic veneers could restore the biomechanical behavior of prepared central incisors and made it similar of that of an intact tooth. Regardless of the preparation depth and design and the ceramic system used, the cervical margin of ceramic veneers presents the highest von Mises stress values. When feldspathic porcelain was compared with lithium disilicate (IPS e.max Press), the latter displayed the lowest transfer of stresses to dental tissues. An increase in preparation depth resulted in a statistically significant stress decrease in both the veneer and the tooth.

Incisal preparation design for ceramic veneers: A critical review

BACKGROUND

The authors reviewed and identified the evidence for the various incisal preparation designs for ceramic veneers.

TYPES OF STUDIES REVIEWED

The authors searched MEDLINE with PubMed and Ovid to identify any articles in the English language related to the topic up through March 2017 using a combination of key words: "porcelain veneer or ceramic veneer or dental veneer or labial veneer" AND "preparation," NOT "composite veneer," NOT "crown," NOT "implant," NOT "fixed partial denture or bridge or denture," NOT "porcelain-fused-to-metal," NOT "marginal gap or fit."

RESULTS

In vitro studies showed that the palatal chamfer preparation design increases the risk of developing ceramic fractures. The butt joint preparation design had the least effect on the strength of the tooth.

CONCLUSIONS

Surveys show the 2 most common incisal preparation designs provided are butt joint and feathered-edge. Clinical studies have identified that incisal ceramic is the most common location of ceramic fracture. In addition, there is a lack in standardization of the modeling structures and type of finite element analysis.

PRACTICAL IMPLICATIONS

The evidence seems to support the use of butt joint over palatal chamfer incisal preparation design. Fracture or chipping is the most frequent complication and the risk increases with time. Incisal ceramic is the most common location of ceramic fracture.

Evaluation of fracture resistance of ceramic veneers with different preparation designs and loading conditions: An in vitro study

Purpose:

The purpose of this study was to evaluate the effect of incisal butt joint and incisal overlap design on the fracture resistance of ceramic veneers under two different loading conditions, i.e., 125° and 60° representing protrusive and intercuspal movements, respectively.

Materials and Methods:

Thirty-two maxillary central incisors were divided into two groups of sixteen specimens each and were prepared with incisal butt joint and incisal overlap design. Ceramic veneers were fabricated and cemented. Both the groups were further divided and mechanical testing to evaluate the fracture resistance were done using the universal testing machine. The values were recorded in Newton along with the assessment of the failure mode of both veneer and the tooth.

Results:

Unpaired t-test showed a significant difference (P < 0.05) with butt joint design having higher fracture resistance than palatal overlap design with the mean value of 409.50N at 60° angle and 473.37N at 125° angle. Paired t-test depicted a significant difference for both the designs at 125° than at 60° angle (P < 0.05). Chi-square analysis showed more number of intact veneers with butt joint design; however, there was no significant difference (P > 0.05). Failure mode of teeth showed more number of coronal fracture followed by cervical fracture and root fracture, but there was no significant difference between the two groups (P > 0.05).

Conclusion:

Butt joint design had higher fracture resistance than palatal overlap design. Under functional loads for both designs, fracture resistance was higher at 125° than at 60° angle.

Effect of Preparation Designs on the Prognosis of Porcelain Laminate Veneers: A Systematic Review and Meta-Analysis

Objective:

To investigate the association between preparation designs and prognosis of porcelain laminate veneers (PLVs).

Methods:

Electronic and manual literature searches were performed in Medline, Embase, CENTRAL, and Scopus databases for randomized controlled trials and retrospective and prospective cohort studies comparing any two of three preparation designs. The quality of the included studies was assessed using the Newcastle-Ottawa scale. Pooled hazard ratios and risk ratios were used to evaluate the difference between two preparation designs. Subgroup analyses, sensitivity analysis, and evaluation of publication bias were performed if possible.

Results:

Of 415 screened articles, 10 studies with moderate to high quality were included in the meta-analysis. Comparison of preparations with incisal coverage to preparations without coverage revealed a significant result based on time-to-event data (hazard ratio=1.81, 95% confidence interval [CI]=1.18-2.78, I2=12.5%), but the result was insignificant based on dichotomous data (risk ratio=1.04, 95% CI=0.59-1.83, I2=42.3%). The other comparisons between any two of overlap, butt-joint, and window types revealed no statistically significant difference. Subgroup analyses regarding the porcelain materials, location of prosthesis, and tooth vitality could account for only part of the heterogeneity. No evidence of publication bias was observed.

Conclusions:

Within the limitation of the present study, it can be concluded that preparation design with incisal coverage for PLVs exhibits an increased failure risk compared to those without incisal coverage. The failure risk of the overlap type may be higher than the butt-joint type but must be validated in further studies.

The Effect of Polymerization and Preparation Techniques on the Microleakage of Composite Laminate Veneers

BACKGROUND

Marginal leakage is the important factor influencing the maintenance of dental esthetic.

AIM

The purpose of this study was to evaluate the relationship between the preparation techniques and type of polymerization techniques on microleakage of composite laminate veneers.

MATERIALS AND METHODS

Ninety-one same sized, caries-free human maxillary central incisors were randomly assigned to 13 groups (n = 7) and were designed with four different preparation techniques (window type, feather type, bevel type, and incisal overlap type). One group determined as control group and any preparation was applied. Nanohybrid resin composite was used for restoration. Composite laminate veneers polymerized with three different techniques (direct light curing, indirect polymerization with a combination of pressure, light and heat using a light cup and heat cup, direct polymerization, and additionally heat cured in an oven). The specimens were thermocycled, and then immersed in 5% basic fuchsine solution. Following 24 h, all specimens were immersed in 65% nitric acid solutions for volumetric dye extraction test. Samples diluted with distilled water and centrifuged and microleakage determined by a spectrophotometer.

STATISTICAL ANALYSIS USED

Data were analyzed with two-way ANOVA and Tukey honest significant difference post hoc multiple comparisons test (P < 0.05).

RESULTS

For comparing the microleakage value of preparation and polymerization techniques, Window type preparation showed a significant difference in direct polymerization + additional cured group (P < 0.05). Control group was statistically different from the other groups (P < 0.05).

CONCLUSIONS

Window type laminate preparation can be preferred in indirect polymerization technique because it caused less leakage in this present study.

Thermal-stress analysis of ceramic laminate veneer restorations with different incisal preparations using micro-computed tomography-based 3D finite element models

Main objective of this study is to investigate the thermal behavior of ceramic laminate veneer restorations of the maxillary central incisor with different incisal preparations such as butt joint and palatinal chamfer using finite element method. In addition, it is also aimed to understand the effect of different thermal loads which simulates hot and cold liquid imbibing in the mouth. Three-dimensional solid models of the sound tooth and prepared veneer restorations were obtained using micro-computed tomography images. Each ceramic veneer restoration was made up of ceramic, luting resin cement and adhesive layer which were generated based on the scanned images using computer-aided design software. Our solid model also included the remaining dental tissues such as periodontal ligament and surrounding cortical and spongy bones. Time-dependent linear thermal analyses were carried out to compare temperature changes and stress distributions of the sound and restored tooth models. The liquid is firstly in contact with the crown area where the maximum stresses were obtained. For the restorations, stresses on palatinal surfaces were found larger than buccal surfaces. Through interior tissues, the effect of thermal load diminished and smaller stress distributions were obtained near pulp and root-dentin regions. We found that the palatinal chamfer restoration presents comparatively larger stresses than the butt joint preparation. In addition, cold thermal loading showed larger temperature changes and stress distributions than those of hot thermal loading independent from the restoration technique.

Finite element method analysis of the periodontal ligament in mandibular canine movement with transparent tooth correction treatment

Background

This study used the 3D finite element method to investigate canine’s displacements and stresses in the canine’s periodontal ligament (PDL) during canine’s translation, inclination, and rotation with transparent tooth correction treatment.

Methods

Finite element models were developed to simulate dynamic orthodontic treatments of the translation, inclination, and rotation of the left mandibular canine with transparent tooth correction system. Piecewise static simulations were performed to replicate the dynamic process of orthodontic treatments. The distribution and change trends of canine’s displacements and stresses in the canine’s PDL during the three types of tooth movements were obtained.

Results

Maximum displacements were observed at the crown and middle part in the translation case, at the crown in the inclination case, and at the crown and root part in the rotation case. The relative maximum von Mises and principal stresses were mainly found at the cervix of the PDL in the translation and inclination cases. In the translation case, tensile stress was mainly observed on the mesial and distal surfaces near the lingual side and compressive stress was located at the bottom of the labial surface. In the inclination case, tensile stress was mainly observed at the labial cervix and lingual apex and compressive stress was located at the lingual cervix and labial apex. In the rotation case, von Mises stress was mainly located at the cervix and inside the lingual surface, tensile stress was located on the distal surface, and compressive stress was detected on the mesial surface. The stress and displacement value rapidly decreased in the first few steps and then reached a plateau.

Conclusions

Canine’s movement type significantly influences the distribution of canine’s displacement and stresses in the canine’s PDL. Changes in canine’s displacement and stresses in the canine’s PDL were exponential in transparent tooth correction treatment.