Effects of directions of maxillary protraction forces on biomechanical changes in craniofacial complex

Comparison of stress distribution and displacement pattern of maxillary expansion in craniomaxillary complex using rapid maxillary expander and maxillary skeletal expander: A finite element model analysis

INTRODUCTION

A combination of miniscrews and the maxillary skeletal expander (MSE) was created to address potential issues with the traditional rapid maxillary expander (RME). This study was conducted to assess and compare stress distribution and displacement patterns in the craniomaxillary complex during maxillary expansion using Rapid Maxillary Expander (RME) and Maxillary Skeletal Expander (MSE) using 3D Finite Element model.

METHODS

A 3D Finite Element model of the craniomaxillary complex, including the maxilla and maxillary dentition, was generated using computer aided design software. Stress distribution and displacement patterns were analysed for both RME and MSE treatments.

RESULTS

The results showed that MSE had greater bone displacement, bone stress, teeth displacement, teeth stress, and periodontal displacement and stress compared to RME. In terms of suture displacement, MSE had higher frontonasal suture displacement compared to RME. Teeth displacement showed that central and lateral incisors showed palatal displacement with RME and buccal displacement with MSE, while canine, premolars, and molars all showed greater buccal displacement with MSE compared to RME along the transverse axis. Central incisor displacement was observed in the extrusion direction with RME, while it was in the intrusion direction with MSE. In terms of teeth stress, MSE treatment resulted in higher stress on the central incisor, lateral incisor, canine, premolars, and molars compared to RME treatment.

DISCUSSION

Overall, MSE exhibited greater bone displacement, stress, and suture displacement/stress compared to RME. Additionally, MSE induced different tooth displacement patterns with higher stress on teeth compared to RME. These findings suggest differences in treatment outcomes and biomechanical effects between the two expansion methods.

Enhancing sports mouthguards with PLA + and PC: stress reduction, energy absorption, and topology optimization

OBJECTIVES

The objective of this paper was to compare the effectiveness of different materials for mouthguards in preventing oral and maxillofacial injuries during sports activities. The present study compares the stress-reduction and energy absorption capabilities of two other fused filament materials - poly(lactic-acid plus) (PLA+) and polycarbonate (PC), with Ethylene-vinyl acetate (EVA), which is the most commonly used material for mouthguard fabrication.

MATERIALS AND METHODS

Two human skulls were modelled, and a boxing glove simulated punches along the x, y, and z-axes with 5 mm displacement with 1 kN force. Firstly, the maximum principal stress curve in the skull was compared for forces along the three perpendicular directions. Furthermore, the present study examines materials energy absorption properties, including their specific energy absorption characteristics and initial peak von Mises stresses. Additionally, a topology optimization approach is used to create an alternative design for a mouthguard to improve specific energy absorption.

RESULTS

The model without a mouthguard showed the highest stress concentration of 32.298 MPa in the teeth, followed by the EVA material, which resulted in a maximum principal stress of 28.525 MPa. Fused filament 3D materials, such as PLA + and PC, on the other hand, showed better mechanical effectiveness in both lower jaw dislocation and lower maximum principal stress by 30.82% and 51.25% in the mandibular and maxillary teeth. Though EVA comparatively shows better specific energy absorption capability at 2.24 kJ/kg post-optimization than PLA + and PC, the peak principal stress experienced in the mandibular region was comparatively higher. The topology optimization, however, improved the energy-absorbing capabilities of PLA + by 4.5 times, reaching 1.37 kJ/kg and PC from 0.165 kJ/kg to 0.38 kJ/kg.

CONCLUSIONS

This study demonstrates that PLA + and PC have better stress reduction capabilities than EVA and could be promising materials for the fabrication of mouthguards in sports activities. This study highlights the importance of topology optimization in dental materials science and engineering to develop safer and more effective mouthguard designs.

A finite element analysis of stress distribution with various directions of intermaxillary fixation using orthodontic mini-implants and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy

OBJECTIVE

This finite element analysis (FEA) aimed to assess the stress distribution in the mandible and fixation system with various directions of the intermaxillary fixation (IMF) using mini-implants (MIs) and elastics following mandibular advancement with a bilateral sagittal split ramus osteotomy (BSSRO).

MATERIALS AND METHODS

A total of nine mandibular advancement models were set according to the position of the MIs (1.6 mm in diameter, 8 mm in length) and direction of the IMF elastics (1/4 inch, 5 oz). Major and minor principal stresses in the cortical and cancellous bones, von Mises stresses in the fixation system (miniplate and monocortical screws), and bending angles of the miniplate were analysed.

RESULTS

Compressive and tensile stress distributions in the mandible and von Mises stress distributions in the fixation system were greater in models with a Class III IMF elastic direction and a higher IMF elastic force than in models with a Class II IMF elastic direction and a lower IMF elastic force. The bending angle of the miniplate was negligible.

CONCLUSIONS

Stress distributions in the bone and fixation system varied depending on the direction, amount of force, and position of IMF elastics and MIs. Conclusively, IMF elastics in the Class II direction with minimal load in the area close to the osteotomy site should be recommended.

Influence of the hyrax expander screw position on displacement and stress distribution in teeth: A study with finite elements

INTRODUCTION

This study aimed to simulate the different positions of the hyrax appliance expander screw and evaluate tooth displacement and the stress distribution standard on the periodontal ligament using the finite element method.

METHODS

Part of the maxilla with anchorage teeth, periodontal ligament, midpalatal suture, and the hyrax appliance was modeled, and finite element method models were created to simulate 6 different screw positions. There were 2 vertical positions at distances of 20 mm and 15 mm from the occlusal plane. Another position was anteroposterior, the center of the screw placed between and equidistant from the mesial face of the first molar and the distal face of the first premolar, aligned to the center of the crown of the first molar, with the anterior edge of the screw aligned to the distal face of the first molar. A 1 mm activation of the expander screw was simulated. The displacement (total, vertical, and buccolingual) and the stress distribution on the periodontal ligament of supporting teeth in each model were registered.

RESULTS

The model simulating the expander screw in a more occlusal and anterior position presented higher displacement values and higher stress concentration, followed by the model with the screw in a more posterior but same vertical position. With the exception of the first premolar, the teeth presented cervical-apical displacement in the vestibular face and apical-cervical displacement in palatal faces. This displacement is compatible with the vestibular inclination associated with the activation of the expander screw. The first premolar presented an atypical tendency for the mesial and lingual displacement of the vestibular surface and counterclockwise rotation.

CONCLUSIONS

The supporting teeth presented a tendency for vestibular crown displacement and lingual root displacement associated with compression areas in the vestibular-cervical region and tensile strength in the linguoapical region. Placing the expander screw in a more occlusal and anterior position generated more mechanical stress transfer, resulting in greater dental displacement.

Relative effectiveness of facemask therapy with alternate maxillary expansion and constriction in the early treatment of Class III malocclusion

INTRODUCTION

This study aimed to investigate the relative efficacy of maxillary protraction combined with a modified alternate rapid maxillary expansion and constriction (Alt-RAMEC) protocol compared with conventional protocols in the early orthopedic treatment of skeletal Class III malocclusion.

METHODS

A sample of 39 patients was divided into 3 groups on the basis of different interventions. Conventional facemask (FM) with splint-type intraoral devices was performed in the FM group (7 males and 5 females; mean age, 9.53 ± 1.37 years). Maxillary expansion with an activation rate of 0.5 mm/d (twice a day) followed by FM therapy was applied in the rapid maxillary expansion group (RME/FM) (6 males and 6 females; mean age, 9.31 ± 1.60 years). In the Alt-RAMEC/FM group (7 males and 8 females; mean age, 10.01 ± 1.31 years), Alt-RAMEC was started simultaneously and throughout the entire course of maxillary protraction, with repetitive alternations between activation and deactivation of expanders (0.5 mm/d for 7 days). The patients in all groups were instructed to wear FMs for a minimum of 12 h/d. Pretreatment and posttreatment lateral cephalograms were all traced and measured.

RESULTS

The Alt-RAMEC group showed statistically more significant maxillary advancement than other groups (A-VRP, 3.87 mm vs 3.04 mm [RME/FM], vs 2.04 mm [FM]; P <0.05). Analysis of variance did not reveal significant intergroup differences in palatal plane angulation changes (P >0.05). No pronounced mandibular clockwise rotations were noted in the Alt-RAMEC/FM group with distinct intergroup differences (P <0.05). There were more skeletal effects (88.7%) during overjet correction in the Alt-RAMEC/FM protocol.

CONCLUSIONS

A combination of the modified Alt-RAMEC protocol with FM revealed more favorable skeletal effects compared with FM and RME/FM protocols in treating prepubertal patients with maxillary deficiency.

Displacement and stress distribution of the maxilla under different surgical conditions in three typical models with bone-borne distraction: a three-dimensional finite element analysis

OBJECTIVE

The present study compared the skeletal effects of surgically assisted rapid maxillary expansion (SARME) with different surgeries in three representative finite element (FE) models.

STUDY DESIGN

According to the ossification level of midpalatal suture, three FE models, with different elasticity moduli of sutures (E = 1 MPa, 500 MPa, and 13,700 MPa) were constructed, to represent three age groups of patients. Within each model, four groups were set up according to different surgeries: group I (control group without surgery), II (paramedian osteotomy), III (pterygomaxillary separation), and IV (paramedian osteotomy and pterygomaxillary separation). An expansion force of 100 N and 1 mm displacement were applied via a bone-borne distraction to simulate the expansion process.

RESULTS

By analyzing these models, the maximum displacement of maxilla was observed in group IV, with E = 1 MPa model exhibiting the most displacement (28.5 × 10^-6 mm), followed by group II (21.4 × 10^-6 mm). Group IV showed a unique backward-downward rotation with minimum stress distributions in three models (9 MPa, 131 MPa, and 140 MPa, respectively), and group II exhibited comparable low stress distributions (12 MPa, 151 MPa, and 230 MPa, respectively). Lowest stress was found in E = 1 MPa model, compared with the other two models.

CONCLUSION

There is no need to perform surgeries when the midpalatal suture is open, and surgery guidelines are the same for partial and complete fusion sutures. Furthermore, exclusive use of partial paramedian osteotomy is sufficient enough to reduce stress and expand the posterior part of maxilla, and it is less invasive.

Three-dimensional finite element analysis of initial displacement and stress on the craniofacial structures of unilateral cleft lip and palate model during protraction therapy with variable forces and directions

Maxillary protraction and expansion is recommended to treat midfacial deficiency in patients with cleft lip and palate (CLP), where amount and direction of forces can change displacement and stress. This study assessed the initial displacement and stresses using Facemask and Maxgym forces with and without RME at +20^∘, 0^∘, and -20^∘ angulation using a finite element (FE) model of unilateral cleft lip and palate (UCCLP). The Initial displacement and stress were more for protraction with expansion as compared to only protraction. Asymmetric displacement was observed with more on cleft than on noncleft side and more on dental than skeletal structures. Palatal plane rotated less upward, increased arch width and decreased arch length was observed with protraction with expansion.

Management of skeletal Class III with facial asymmetry using skeletal anchorage: 4-year follow-up

Introduction:

Skeletal Class III malocclusion with asymmetry is one of the most difficult problems to correct in orthodontics. A functional shift of the mandible in growing patients may occur accompanying a Class III, due to constricted maxillary arch and occlusal interferences. Studies have indicated that posterior unilateral crossbite develops early and has a low rate of spontaneous correction. It may further lead to development of mandibular and facial asymmetry by growth and displacement of mandible if left untreated in growing patients.

Objective:

This article reports the clinical case of a thirteen-year-old female patient in CVMI transition stage that had maxillary hypoplasia with a developing facial asymmetry. Results: The case was successfully managed with bone-anchored facemask therapy and with elimination of occlusal interferences with guided occlusion. Reverse twin block in the retention phase maintained the results achieved.

Conclusion:

A four-year follow-up evaluation revealed successful maintenance of the treatment results.

Soft tissue facial profile in Class III malocclusion: long-term post-pubertal effects produced by the Face Mask Protocol

Objectives

The objective of this study was to analyze soft tissue changes produced by rapid maxillary expansion and facial mask therapy in growing Class III patients.

Materials

The treated group consisted of 32 Caucasian patients (15 females and 17 males) with dentoskeletal Class III malocclusion treated with the Face Mask Protocol (FMP, rapid maxillary expander, facial mask, and removable lower bite-block). All patients were evaluated before treatment (T1; mean age, 8.4 years), at the end of active treatment (T2; mean age, 10.7 years), and at a post-pubertal follow-up observation (T3; mean age, 15.8 years). The treated group was compared with a matched control group of 20 untreated subjects (10 females and 10 males) with dentoskeletal Class III malocclusion. Statistical comparisons between two groups were performed with the independent samples t-test (P < 0.05).

Results

Significant improvements were found during the long-term T1–T3 interval for profile facial angle (–5.8°), nasolabial angle (–4.4°), mandibular sulcus (–10.3°), upper lip protrusion (+0.7 mm), and lower lip protrusion (–1.1 mm) in the treated group. No significant post-pubertal effects were found in terms of lower face percentage between two groups.

Limitations

This study has a retrospective design and it used a historical control sample.

Conclusion

The FMP induced positive effects on soft tissue facial profile with a good long-term post-pubertal stability.

Influence of custom-made and stock mouthguard thickness on biomechanical response to a simulated impact

BACKGROUND/AIMS

Mouthguards (MGs) are devices that can reduce the risks of facial trauma. However, the large variety of MG types and thicknesses raises the question of which type is the most effective and beneficial for the athletes. The aim of this study was to evaluate stress distribution in the skull, teeth, and jaws as a consequence of a direct impact.

MATERIAL AND METHODS

Using modeling software, a human skull was modeled and a human jaw was created with all teeth inserted into the respective alveolus. The models were divided according to the MG type (custom-made or stock) and thickness (1, 2, and 4 mm). Two models without MG were evaluated with and without teeth contact. The geometries were exported to analysis software and the materials were considered ideal. Fixation occurred at the base of the foramen magnum. The load (500 N) was applied on the canine tooth with a ball. Maximum principal (MPa) and Von-Mises results were obtained.

RESULTS

Without any protection, the generated tensile stress was of greater magnitude causing more damage in the absence of teeth contact. The presence of a MG significantly reduced the generated stress in all structures, and the customized/individualized type was more efficient than stock MGs.

CONCLUSIONS

In extreme situations when it is impossible to use a MG, keeping the teeth in maximum intercuspal position is less harmful. Despite this, the use of any MG is beneficial and assists in dampening the generated stress. The thicker the device, the greater the capacity for decreasing the damage in all structures. The use of individual protectors for each patient is even more beneficial for preventing trauma during at-risk activities of impact.

Effect of Long-Term Use of Facemask With Miniplate on Maxillary Protraction in Patients With Cleft Lip and Palate

The purpose of this retrospective study was to investigate the effect of a long-term use of facemask with miniplate (FM-MP) on maxillary protraction in cleft lip and palate (CLP) patients. The subjects were 21 CLP patients (16 unilateral CLP and 5 bilateral CLP patients), who were treated with identical lip and palate surgical method and FM-MP therapy performed by single surgeon and single orthodontist. Lateral cephalogram was taken before (T1; mean age, 11.1 years) and after maxillary protraction (T2; mean age, 16.9 years). The mean duration of FM-MP was 68.0 months. After 17 cephalometric variables were measured, statistical analysis was performed. During T1-T2, the maxilla showed significant forward movement (ΔA-vertical reference plane, 4.8 mm, P < 0.001; ΔSNA, 1.9 degree, P < 0.001; ΔA-N perp, 1.9 mm, P < 0.05), although the mandible exhibited a forward growth (ΔSNB, 1.2 degree, P < 0.05). Despite downward movement of the posterior maxilla with counterclockwise rotation (Δpalatal plane angle, -1.5 degree, P < 0.05), the mandible did not exhibit clockwise rotation but counterclockwise rotation (ΔSN to mandibular plane angle, -1.4 degree, ΔBjork sum, -1.4 degree, Δocclusal plane to SN plane angle, -1.5 degree, ΔFMA, -1.0 degree, all P < 0.05) and showed decrease in Gonial angle (-1.2 degree, P < 0.01). Although there was labioversion of the maxillary incisor (ΔU1 to SN, 4.1 degree, P < 0.05), the mandibular incisor did not exhibit significant linguoversion (ΔIMPA, -1.3 degree, P > 0.05). Long-term use of FM-MP is effective on maxillary protraction in adolescent CLP patients without clockwise rotation of the mandible, the main drawback of conventional facemask with tooth-borne anchorage.

Facemask performance during maxillary protraction: a finite element analysis (FEA) evaluation of load and stress distribution on Delaire facemask

BACKGROUND

To evaluate load and stress distribution on Delaire facemask (FM) during maxillary protraction in class III growing patients by means of finite element analysis (FEA). A three-dimensional geometry of a Delaire FM was reconstructed from the original CAD 3D prototype, using software package (ANSYS 5.7). FM presented forehead and chin supports and stainless steel framework characterized by two lateral vertical bars connected to a crossbar with two pawls for elastic attachment. Two traction intensities (7.8 and 9.8 N) were applied on the FM pawls along three different downward inclined directions with respect to the occlusal plane (0°, 30°, or 50°, respectively). Resulting stresses and deformations were then tested through the von Mises yield criterion in order to underline the FM wear performance.

RESULTS

The analysis showed that higher stresses and deformations are mostly related to axial forces of 9.8 N rather than 7.8 N. Stresses also progressively increased with increasing downward force inclinations (0°, 30°, and 50° with respect to the occlusal plane). The overall tensions were inferior to the limit of the elastic behavior (yield point) characterizing the material they are applied on. Thus, the FM structure absorbed the load applied with an elastic deformation of the lateral and horizontal bars.

CONCLUSIONS

Resulting stresses and deformations were directly proportional to protraction load amounts and to increasing downward inclination of forces. In all tested conditions, protraction forces were not able to determine plastic deformation on FM structure compromising its performance and efficiency.

Evaluation of the effects of miniscrew incorporation in palatal expanders for young adults using finite element analysis

Objective

The aim of this study was to evaluate the stress distribution and displacement of various craniofacial structures after nonsurgical rapid palatal expansion (RPE) with conventional (C-RPE), bone-borne (B-RPE), and miniscrew-assisted (MARPE) expanders for young adults using three-dimensional finite element analysis (3D FEA).

Methods

Conventional, bone-borne, and miniscrew-assisted palatal expanders were designed to simulate expansion in a 3D FE model created from a 20-year-old human dry skull. Stress distribution and the displacement pattern for each circumaxillary suture and anchor tooth were calculated.

Results

The results showed that C-RPE induced the greatest stress along the frontal process of the maxilla and around the anchor teeth, followed by the suture area, whereas B-RPE generated the greatest stress around the miniscrew, although the area was limited within the suture. Compared with the other appliances, MARPE caused relatively even stress distribution, decreased the stress on the buccal plate of the anchor teeth, and reduced tipping of the anchor teeth.

Conclusions

The findings of this study suggest that the incorporation of miniscrews in RPE devices may contribute to force delivery to the sutures and a decrease in excessive stress on the buccal plate. Thus, MARPE may serve as an effective modality for the nonsurgical treatment of transverse maxillary deficiency in young adults.

Evaluation of the Effects of the Dental and Skeletal Anchored Face Mask Therapies on the Craniofacial System by Using Nonlinear Finite Element Analysis

Aims

The aim of this study was to evaluate the biomechanical effects on the craniofacial complex of skeletal anchorage and dental anchorage during face mask therapy.

Subjects and Methods

Two nonlinear finite element (FE) simulations were performed using a three-dimensional FE model. Face mask therapy with dental anchorage in the upper canines and face mask therapy with skeletal anchorage in the piriform apertures of the maxilla were simulated. In both simulations, the magnitude of the applied force was 750 g per side, and the force direction was 30° forward and downward relative to the occlusal plane.

Results

The circummaxillary sutures showed greater and more uniform stresses in the skeletal anchorage model than the dental anchorage model. This is the result of the more parallel forward movement of the maxilla in the skeletal anchorage model.

Conclusions

In Class III malocclusions with maxillary deficiency, for improved effects on the maxilla, choosing skeletal anchorage may be more effective in face mask therapies

Stress generation in mandibular anterior teeth restored with different types of post-and-core at various levels of ferrule

STATEMENT OF PROBLEM

Pertinent evidence regarding the mechanical integrity of mandibular anterior teeth restored with a post-and-core is limited.

PURPOSE

The purpose of this finite element analysis study was to compare the impact of the post type (glass fiber post-and-resin core or cast post-and-core) along with the ferrule effect on the stress fields generated in endodontically treated mandibular lateral incisors and canines.

MATERIAL AND METHODS

Three-dimensional models of the segmented mandible were developed. Mandibular incisors and canines with or without a 2-mm circular ferrule and restored with a cast post-and-core or glass fiber post-and-resin core were simulated and subjected to linear elastic static analysis. The principal stress values were calculated. von Mises equivalent stresses were used to evaluate the stress.

RESULTS

Maximum principal stresses in dentin were highest in incisors, with a ferrule. Stress parameters in composite resin core in both incisors and canines were critically close to the tensile failure limit of the core material. Cast post-and-cores cemented in incisors without a ferrule accumulated the highest stresses, exceeding the tensile failure limit of resin-modified glass ionomer cement.

CONCLUSIONS

Tooth preparation with a ferrule led to a remarkable rise in stress in the dentin of mandibular incisors but favored the mechanical integrity of the restoration.

Stress and displacement patterns in the craniofacial skeleton with rapid maxillary expansion-a finite element method study

Background

Rapid maxillary expansion (RME), indicated in the treatment of maxillary deficiency directs high forces to maxillary basal bone and to other adjacent skeletal bones. The aim of this study is to (i) evaluate stress distribution along craniofacial sutures and (ii) study the displacement of various craniofacial structures with rapid maxillary expansion therapy by using a Finite Element model.

Methods

An analytical model was developed from a dried human skull of a 12 year old male. CT scan images of the skull were taken in axial direction parallel to the F-H plane at 1 mm interval, processed using Mimics software, required portion of the skull was exported into stereo-lithography model. ANSYS software was used to solve the mathematical equation. Contour plots of the displacement and stresses were obtained from the results of the analysis performed.

Results

At Node 47005, maximum X-displacement was 5.073 mm corresponding to the incisal edge of the upper central incisor. At Node 3971, maximum negative Y-displacement was -0.86 mm which corresponds to the anterior zygomatic arch, indicating posterior movement of craniofacial complex. At Node 32324, maximum negative Z-displacement was -0.92 mm representing the anterior and deepest convex portion of the nasal septum; indicating downward displacement of structures medial to the area of force application.

Conclusions

Pyramidal displacement of maxilla was evident. Apex of pyramid faced the nasal bone and base was located on the oral side. Posterosuperior part of nasal cavity moved minimally in lateral direction and width of nasal cavity at the floor of the nose increased, there was downward and forward movement of maxilla with a tendency toward posterior rotation. Maximum von Mises stresses were found along midpalatal, pterygomaxillary, nasomaxillary and frontomaxillary sutures.

Displacement and stress distribution by different bone-borne palatal expanders with facemask: A 3-dimensional finite element analysis

INTRODUCTION

The purpose of this study was to analyze displacement and stress distribution in the maxilla during maxillary expansion followed by protraction using bone-borne and conventional tooth-borne palatal expanders and a facemask via 3-dimensional finite element analysis.

METHODS

A finite element model of an adolescent skull was created, and 4 different types of appliances were integrated into it: facemask (type A); facemask with paramedian bone-borne expander (type B), facemask with palatal-slope bone-borne expander (type C), and facemask with conventional expander (type D). Expansion of 0.25 mm followed by 500 g of force per side was applied.

RESULTS

Type A showed anterior displacement of the dentition combined with downward displacement of posterior teeth and upward displacement of anterior teeth. The combination of protraction and expansion in type D showed the greatest anterior displacement. In types B and C, the expansion forces resulted in posterior displacement decreasing the net displacement of the combination. Stresses concentrated around the miniscrews in types B and C. In types A and D, stresses concentrated at the first premolar and first molar. Type B had the highest stresses followed by type C and then D.

CONCLUSIONS

The conventional tooth-borne expander (type D) enhanced the effect of maxillary protraction. Facemask alone (type A) resulted in more anterior displacement of the maxilla than the combination of facemask and bone-borne expanders (types B and C). The clinician should be aware of the initial stresses and movements from different expanders with facemask found in this study and confirm the movements in future clinical Class III studies.

A comparative evaluation of skeletal, dental, and soft tissue changes with skeletal anchored and conventional facemask protraction therapy

OBJECTIVE

To cephalometrically evaluate and compare the skeletal, dentoalveolar, and soft tissue changes after maxillary protraction with skeletally anchored and conventional facemask.

METHODS

The data for the study were collected from the pre- and post-treatment records of patients of maxillary retrusion treated with skeletally anchored and conventional facemask therapy. Twenty subjects were included in the study and were categorized into two groups, namely skeletal anchored maxillary protraction (SAMP) group with the mean age of 10.10 ± 1.1 years and conventional facemask maxillary protraction (CFMP) group with the mean age of 9.90 ± 1.1 years. Pre and post-treatment lateral cephalograms were assessed.

RESULTS

The data were analyzed by Mann-Whitney test and Wilcoxon signed-rank test. The mean duration of treatment in SAMP group and CFMP group was 5.8 months and 10 months, respectively. The mean forward displacement of the maxilla (vertical point A) was 3.40 ± 1.07 mm in SAMP group and 2.80 ± 0.79 mm in CFMP group. The mandible showed downward and backward rotation in both the groups with more rotation in CFMP group. A significant increase in maxillary incisor inclination was seen in CFMP group as compared to SAMP group. A significant decrease was found in mandibular incisor inclination in both the treatment groups. The soft tissue changes corresponded to underlying skeletal tissue.

CONCLUSIONS

SAMP is proven to be a better treatment modality as compared to CFMP for achieving true skeletal changes and minimal dental changes in cases with developing skeletal Class III with maxillary retrusion.

Management of skeletal Class III malocclusion with face mask therapy and comprehensive orthodontic treatment

Orthopedic correction of skeletal Class III malocclusion in a growing patient is crucial as it can circumvent future surgical procedures. Further, as surgery is done only at a later stage, early treatment helps to avoid the detrimental effects produced by the facial disfigurement on the patient's social life. This case report describes the treatment of a child aged 9 years 6 months who had a skeletal Class III malocclusion. The treatment plan involved the use of a reverse pull headgear (facemask) and multibracket appliance therapy resulting in successful correction of the malocclusion. The treatment results were highly satisfactory resulting in improved facial esthetics, a skeletal Class I with a Dental Class I molar and canine relationship, an ideal overjet and overbite. Thus, dentoalveolar camouflage, if done in properly selected cases, alleviates the need for surgical intervention. The patient is being monitored until the end of growth to ensure the stability of treatment results.

Short-term effects produced by rapid maxillary expansion and facemask therapy in Class III patients with different vertical skeletal relationships

OBJECTIVE

To evaluate the dentoskeletal short-term effects of rapid maxillary expansion and facemask therapy (RME/FM) in a sample of Class III patients showing different vertical skeletal relationships.

MATERIALS AND METHODS

Seventy-nine patients (35 females and 44 males) having Class III malocclusion were consecutively treated using RME/FM therapy with application of the protraction force in a downward and forward direction and inclination of about 30° to the occlusal plane. All patients were evaluated at the beginning (T1; mean age, 7.7 years) and at the end (T2; mean age, 9.2 years) of orthopedic therapy and divided into three groups according to their vertical skeletal relationships: normal group (NG), hypodivergent group (HypoG), and hyperdivergent group (HyperG). Statistical comparisons between the three groups were performed on the starting forms (T1), the final forms (T2), and the treatment changes (T1-T2) using the ANOVA with Tukey's post hoc tests.

RESULTS

Favorable modification in terms of maxillary advancement (changes in SNA ranging from 1.4° to 1.8°) and intermaxillary sagittal skeletal relationships (changes in Wits appraisal ranging from 2.5 mm to 3.5 mm) were recorded in all groups. The three groups showed no statistically significant differences in changes in either sagittal or vertical skeletal variables.

CONCLUSIONS

The various vertical skeletal features do not influence the short-term outcomes of RME/FM therapy.

Displacement and stress distribution of the maxillofacial complex during maxillary protraction with buccal versus palatal plates: finite element analysis

OBJECTIVES

The aim of this study was to analyse the displacement and stress distribution in the maxillofacial complex during maxillary protraction with buccal and palatal plates using three-dimensional finite element analysis.

MATERIALS AND METHODS

Three anchorage appliance models-palatal plate (Type A), miniplate at the infrazygomatic crest (Type B), and conventional tooth-borne appliance (Type C)-were designed and integrated into a skull model. Protraction force was 500 g per side and force direction was forward and 30 degree downward to the maxillary occlusal plane. The stress distribution around the circum-maxillary sutures and the displacement of the surface landmarks were analysed.

RESULTS

All models showed forward and upward displacement at anterior nasal spine, Point A, and prosthion and forward and downward displacement at posterior nasal spine resulting in a counter-clockwise rotation. This anterior displacement was greatest in Type A. At the maxillary process of the zygoma, upward movement was shown only in Type A, whereas downward movement was observed in Types B and C. The greatest stresses in Type A were at the pterygomaxillary and the zygomaticotemporal sutures. Type B showed the greatest stress at the frontomaxillary suture.

LIMITATIONS

Type A showed asymmetric results; however, it was not of clinical significance.

CONCLUSION

The palatal plate resulted in wider stress distribution and more forward displacement compared to miniplate at the infrazygomatic crest area and conventional tooth-borne appliances. It might be recommended to consider the application of the palatal plate for maxillary protraction in Class III patients.

Stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall: a 3-dimensional finite element analysis

INTRODUCTION

The purpose of this study was to compare the pattern and amount of stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall.

METHODS

Three-dimensional finite element models for the skull and the curvilinear type of miniplate were constructed. After a protraction force (500 g/side) was applied to the distal end of the miniplate with a forward and 30° downward vector to the maxillary occlusal plane, stress distributions in the circummaxillary sutures and displacements of the surface landmarks were analyzed.

RESULTS

There was a difference in the maximum stress distribution area according to the site of the miniplate: infrazygomatic crest and middle part of the maxilla in the infrazygomatic crest and paranasal area adjacent to the pyriform aperture in the lateral nasal wall. Stress values of the frontonasal, frontomaxillary, zygomaticomaxillary, and pterygomaxillary sutures were greater in the infrazygomatic crest than in the lateral nasal wall. The site of the miniplate produced differences in the major displacement areas: infrazygomatic crest, maxillary dentition, anterior maxilla, and upper part of the maxillary tuberosity in the infrazygomatic crest and the lateral nasal wall, maxillary dentition, anterior maxilla, and lower part of the maxillary tuberosity in the lateral nasal wall. The lateral nasal wall exhibited forward, downward, and outward displacements of ANS, Point A, and prosthion. However, the infrazygomatic crest showed forward and upward displacements of ANS, Point A, and prosthion, and outward displacement of the zygomatic process of the maxilla and the maxillary process of the zygomatic bone.

CONCLUSIONS

The site of miniplate placement should be considered to obtain proper stress and displacement values in different areas with maxillary hypoplasia.

Stability of rapid maxillary expansion and facemask therapy: a long-term controlled study

INTRODUCTION

The aim of this prospective controlled study was to evaluate the long-term effects of rapid maxillary expansion and facemask therapy in Class III subjects.

METHODS

Twenty-two subjects (9 boys, 13 girls; mean age, 9.2 years ± 1.6) with Class III disharmony were treated consecutively with rapid maxillary expansion and facemask therapy followed by fixed appliances. The patients were reevaluated at the end of the 2-phase treatment (mean age, 14.5 years ± 1.9) and then recalled about 8.5 years after the end of rapid maxillary expansion and facemask treatment (mean age, 18.7 years ± 2.1). Two groups of controls with untreated Class III malocclusion were used for statistical comparisons of the short-term and long-term intervals. Statistical comparisons were performed with the Mann-Whitney U test.

RESULTS

In the long term, no significant differences in maxillary changes were recorded, whereas the treatment group showed significantly smaller increases in mandibular protrusion. The sagittal maxillomandibular skeletal variables maintained significant improvements in the treatment group vs the control groups.

CONCLUSIONS

In the long term, rapid maxillary expansion and facemask therapy led to successful outcomes in about 73% of the Class III patients. Favorable skeletal changes were mainly due to significant improvements in the sagittal position of the mandible.

Effects of facemask treatment anchored with miniplates after alternate rapid maxillary expansions and constrictions; a pilot study

OBJECTIVE

To describe the dentoskeletal and soft tissue effects of facemask treatment anchored with miniplates after alternate rapid maxillary expansions and constrictions (Alt-RAMEC) in maxillary retrusion patients.

MATERIALS AND METHODS

The sample consisted of 15 patients with a mean skeletal age of 11.6 ± 1.59 years undergoing 8 weeks of Alt-RAMEC followed by maxillary protraction. Three hundred fifty to 400 g of force per side was applied to the facemask from the titanium miniplates inserted on the lateral nasal wall of the maxilla. Total treatment time was 9.9 ± 2.63 months. Treatment changes were evaluated cephalometrically and analyzed by means of the dependent t-test and the Wilcoxon signed rank test.

RESULTS

The miniplates withstood the orthopedic forces exerted during the treatment. Cephalometric findings showed that the maxilla moved forward by 2 mm, with an 0.8° counterclockwise rotation and without maxillary incisor movement. The mandible moved slightly in a downward and backward direction (1.2°). The inclinations of the mandibular incisors decreased significantly (2°). Statistically significant increases were observed in the vertical dimension (1°-1.3°). Soft tissue changes were more marked in the upper lip and soft tissue pogonion than in the lower lip.

CONCLUSIONS

This treatment approach can offer an advantage for correcting mild/moderate maxillary retrusion in Class III patients.

Comparative evaluation of maxillary protraction with or without skeletal anchorage

INTRODUCTION

The aim of this prospective clinical study was to evaluate the skeletal, dentoalveolar, and soft-tissue effects of maxillary protraction with miniplates compared with conventional facemask therapy and an untreated Class III control group.

METHODS

Forty-five subjects who were in prepubertal or pubertal skeletal growth periods were included in the study and divided into 3 groups of 15 patients each. All subjects had skeletal and dental Class III malocclusions with maxillary deficiency, vertically normal growth pattern, anterior crossbite, Angle Class III molar relationship, normal or increased overbite, and retrusive nasomaxillary complex. Before maxillary protraction, rapid maxillary expansion with a bonded appliance was performed in both treatment groups. In the first group (MP+FM), consisting of 5 girls and 10 boys (mean age, 10.91 years), facemasks were applied from 2 titanium miniplates surgically placed laterally to the apertura piriformis regions of the maxilla. The second group (FM) of 7 girls and 8 boys (mean age, 10.31 years) received maxillary protraction therapy with conventional facemasks applied from hooks of the rapid maxillary expansion appliance. The third group of 8 girls and 7 boys (mean age, 10.05 years) was the untreated control group. Lateral cephalometric films were obtained at the beginning and end of treatment or observation in all groups and analyzed according to a structural superimposition method. Measurements were evaulated statistically with Wilcoxon and Kruskal-Wallis tests.

RESULTS

Treatment periods were 6.78 and 9.45 months in the MP+FM and FM groups, respectively, and the observation period in the control group was 7.59 months. The differences were significant between the 3 groups (P <0.05) and the MP+FM and FM groups (P <0.001). The maxilla moved forward for 2.3 mm in the MP+FM group and 1.83 mm in the FM group with maxillary protraction. The difference was significant between 2 groups (P <0.001). The protraction rates were 0.45 mm per month in the MP+FM group and 0.24 mm per month in the FM group (P <0.001). The maxilla showed anterior rotation after facemask therapy in the FM group (P <0.01); there was no significant rotation in the MP+FM group. Posterior rotation of the mandible and increased facial height were more evident in the FM group compared with the MP+FM group (P <0.01). Both the maxilla and the mandible moved forward significantly in the control group. Protrusion and mesialization of the maxillary teeth in the FM group were eliminated in the MP+FM group. The maxillomandibular relationships and the soft-tissue profile were improved remarkably in both treatment groups.

CONCLUSIONS

The undesired effects of conventional facemask therapy were reduced or eliminated with miniplate anchorage, and efficient maxillary protraction was achieved in a shorter treatment period.

Effect of varying the vertical dimension of connectors of cantilever cross-arch fixed dental prostheses in patients with severely reduced osseous support: a three-dimensional finite element analysis

STATEMENT OF PROBLEM

Inadequate dimensioning of the connectors in a cantilever cross-arch fixed dental prosthesis (FDP) in perioprosthetic patients jeopardizes the prognosis of the restoration.

PURPOSE

The purpose of this study was to investigate the effect of increasing the vertical dimension (VD) on the maximum stress developed within the connectors during the static loading of a cross-arch FDP extended as a 1- and 2-unit cantilever.

MATERIAL AND METHODS

Six digital models were developed, derived from a 3-dimensional (3-D) initial model. In the initial model, the teeth were prepared for metal ceramic restorations and splinted with a cross-arch FDP, extended as a 1- or 2-unit cantilever. The VDs of the connectors proximal to the retaining abutment were 3, 4, or 5 mm. A 3-D finite element analysis (FEA) was performed.

RESULTS

The VD increase, from 3 to 4 mm and from 3 to 5 mm, of the connector distal to the retaining abutment, for each FDP, presented a maximum stress value decrease of approximately 25% and 48%, respectively. The similar VD increase of the connector mesial to the retaining abutment, for each FDP, resulted in relatively smaller stress changes. For the 2-unit cantilever restoration, the stress decreases were approximately 9% and 15%, respectively, whereas in the 1-unit cantilever restoration, the decrease was about 10% for the 4-mm connector. Further increase of the VD to 5 mm did not relieve the peak stress. The highest stress value was measured on the 3-mm connector distal to the retaining abutment in the 2-unit cantilever restoration. Despite the VD increase, the connectors proximal to the retaining abutment still developed the highest stress values of all the connectors for every model.

CONCLUSIONS

The connector with the highest risk of failure is the 3-mm connector distal to the retaining abutment of the 2-unit cantilever restoration. Increasing the vertical dimension is beneficial for the connector distal to the retaining abutment, while the resultant stress changes are not substantial for the connectors mesial to the retaining abutment. (J Prosthet Dent 2010;103:91-100).

Maxillary protraction with and without maxillary expansion: a finite element analysis of sutural stresses

INTRODUCTION

In this finite element study, we compared the stress patterns along the various craniofacial sutures with maxillary protraction with and without expansion.

METHODS

Two 3-dimensional analytic models were developed, 1 simulating maxillary protraction and the other simulating maxillary protraction with expansion. The model consisted of 108799 10 node solid 92 elements (tetrahedron), 193633 nodes, and 580899 degrees of freedom.

RESULTS

The overall stresses after maxillary protraction with maxillary expansion were significantly higher than with a facemask alone. The magnitude of stress on the craniofacial sutures with maxillary protraction alone was in the range of a few millinewtons per square millimeter, whereas, with maxillary protraction with maxillary expansion, the stresses ranged from a few newtons per square millimeter to a few hundred newtons per square millimeter. The pattern of stress distribution also differed with the 2 treatment modalities as did the sutures experiencing maximum and minimum stresses.

CONCLUSIONS

The osteogenic potential of such low stresses after maxillary protraction can be questioned. High stresses generated in various craniofacial sutures after maxillary protraction with expansion are responsible for disrupting the circummaxillary sutural system and presumably facilitating the orthopedic effect of the facemask.

Skeletal response to maxillary protraction with and without maxillary expansion: a finite element study

INTRODUCTION

The purpose of this finite element study was to evaluate biomechanically 2 treatment modalities-maxillary protraction alone and in combination with maxillary expansion-by comparing the displacement of various craniofacial structures.

METHODS

Two 3-dimensional analytical models were developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry young skull. AutoCAD software (2004 version, Autodesk, San Rafael, Calif) and ANSYS software (version 10, Belcan Engineering Group, Cincinnati, Ohio) were used. The model consisted of 108,799 solid 10 node 92 elements, 193,633 nodes, and 580,899 degrees of freedom. In the first model, maxillary protraction forces were simulated by applying 1 kg of anterior force 30 degrees downward to the palatal plane. In the second model, a 4-mm midpalatal suture opening and maxillary protraction were simulated.

RESULTS

Forward displacement of the nasomaxillary complex with upward and forward rotation was observed with maxillary protraction alone. No rotational tendency was noted when protraction was carried out with 4 mm of transverse expansion. A tendency for anterior maxillary constriction after maxillary protraction was evident. The amounts of displacement in the frontal, vertical, and lateral directions with midpalatal suture opening were greater compared with no opening of the midpalatal suture. The forward and downward displacements of the nasomaxillary complex with maxillary protraction and maxillary expansion more closely approximated the natural growth direction of the maxilla.

CONCLUSIONS

Displacements of craniofacial structures were more favorable for the treatment of skeletal Class III maxillary retrognathia when maxillary protraction was used with maxillary expansion. Hence, biomechanically, maxillary protraction combined with maxillary expansion appears to be a superior treatment modality for the treatment of maxillary retrognathia than maxillary protraction alone.

Evaluation of craniofacial effects during rapid maxillary expansion through combined in vivo/in vitro and finite element studies

It is well documented in the literature that a contracted maxilla is commonly associated with nasal obstruction. Midpalatal splitting using the rapid maxillary expansion (RME) technique produces separation of the maxillary halves with consequent widening of the nasal cavity. Although clinicians agree about many of the indications for and outcomes of RME, some disagreements persist in relation to the biomechanical effects induced. The present research was based on the parametric analysis of a finite element model (FEM) of a dry human skull with the RME appliance cemented in place in order to evaluate these effects on the overall craniofacial complex with different suture ossification. The behaviour of the FEM was compared with the findings of a clinical study and to an in vitro experiment of the same dry skull. Comparisons refer to the opening pattern and associated displacements of four anatomical points located at the left and right maxilla (MI, UM, EM, CN). It was found that the maxillolacrymal, the frontomaxillary, the nasomaxillary, the transverse midpalatal sutures, and the suture between the maxilla and pterygoid process of the sphenoid bone did not influence the outcome of RME, while the zygomatico-maxillary suture influenced the response of the craniofacial complex to the expansion forces. Moreover, the sagittal suture at the level of the frontal part of the midpalatal suture plays an important role in the degree and manner of maxillary separation. Maximum displacements were observed in the area of maxilla below the hard palate, from the central incisors to second premolars, which dissipated at the frontal and parietal bone and nullified at the occipital bone.

Analysis of Sutural Strain in Maxillary Protraction Therapy

Objective: The goal of the study was to examine the strain in the sutures of the midface and the cranial base with maxillary protraction therapy and to clarify whether such stretching suggests a skeletal effect of the apparatus employed for that purpose.

Materials and Methods: Using a finite elements model, a maxillary protraction therapy was simulated with various force levels and vectors, and the strains appearing at the sutures (in μstrain) were measured at the midface and the cranial base. The simulation model we employed consisted of 53,555 individual elements; the simulated forces were 2 × 3 N and 2 × 5 N, while the vectors of the applied forces were in the anterior and anterior caudal direction.

Results: The maximum measured strains were on average below 10 μstrain, while higher values were measured only at the nasal bone and at the cranial base at the oval and spinous foramina with anterior directed force vectors (26.4 μstrain). With an anterior-caudal force vector, the measured values were usually lower.

Discussion: The measured strains were on average about hundredfold lower than the Frost thresholds (2000 μstrain). It does not seem probable that the strains occurring upon maxillary protraction therapy suffice to stimulate any additional bone growth.

Conclusion: The good clinical efficacy of maxillary protraction therapy is apparently based, for the most part, on dental effects, while its skeletal effects still remain doubtful.

Stress and displacement patterns in the craniofacial skeleton with rapid maxillary expansion: A finite element method study

INTRODUCTION

The purpose of this finite element study was to evaluate stress distribution along craniofacial sutures and displacement of various craniofacial structures with rapid maxillary expansion (RME) therapy.

METHODS

The analytic model for this study was developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry young human skull. Subsequently, a finite element method model was developed from computed tomography images by using AutoCAD software (2004 version, Autodesk, Inc, San Rafael, Calif) and ANSYS software (version 10, Belcan Engineering Group, Downers Grove, Ill).

RESULTS

The maxilla moved anteriorly and downward and rotated clockwise in response to RME. The pterygoid plates were displaced laterally. The distant structures of the craniofacial skeleton--zygomatic bone, temporal bone, and frontal bone--were also affected by transverse orthopedic forces. The center of rotation of the maxilla in the X direction was somewhere between the lateral and the medial pterygoid plates. In the frontal plane, the center of rotation of the maxilla was approximately at the superior orbital fissure. The maximum von Mises stresses were found along the frontomaxillary, nasomaxillary, and frontonasal sutures. Both tensile and compressive stresses could be demonstrated along the same suture.

CONCLUSIONS

RME facilitates expansion of the maxilla in both the molar and the canine regions. It also causes downward and forward displacement of the maxilla and thus can contribute to the correction of mild Class III malocclusion. The downward displacement and backward rotation of the maxilla could be a concern in patients with excessive lower anterior facial height. High stresses along the deep structures and the various sutures of the craniofacial skeleton signify the role of the circummaxillary sutural system in downward and forward displacement of the maxilla after RME.

On the FEM modeling of craniofacial changes during rapid maxillary expansion

This paper discusses several aspects related to the development of a reliable finite element model to simulate the craniofacial changes during rapid maxillary expansion treatment. The mechanical model concerns the entire human skull (bony structure and sutures) as well as the jackscrew device; the latter transforms the manual openings into orthodontic forces usually applied to the two maxillary halves through the first premolars and first permanent molars, which are the support points of the appliance. A sensitivity analysis of an approximate finite element model is performed in order to investigate the influence of the model size, the influence of the degree of sutural ossification by assigning different mechanical properties to the sutures and the influence of bone relaxation concerning the effects of dentofacial orthopaedics. Moreover, a more accurate model including the aforementioned teeth and their periodontal ligament as solid elastic structures was analysed in order to evaluate the orthodontic effects induced. Results refer to the opening pattern and associated stresses/displacements/strains on the cranium, the maxillae and the periodontal ligament.

Biomechanical Analysis of Maxillary Expansion in CLP Patients

OBJECTIVE

To carry out a comparative biomechanical analysis of maxillary low force expansion using the quadhelix appliance in cleft and noncleft patients. We also intended to determine whether a sufficient transverse skeletal effect could be achieved among cleft patients using the quadhelix appliance.

MATERIALS AND METHODS

Three finite element models of the viscerocranium and neurocranium were established in which a transverse expansion of the maxilla using a quadhelix (transverse force of 2 N) was simulated.

RESULTS

The skeletal effects at the anatomic structures of the midface and the cranial base were far more marked in the simulation models with clefts compared to the morphologically normal state. The highest expansions were measured for bilateral cleft palates. Thus, the expansion measured at the supraorbital margin was 4.7 mustrain with a bilateral cleft, 2.1 mustrain with a unilateral cleft, and only 0.2 mustrain with the morphologically normal state. For bilateral and also for unilateral bone clefts, the skeletal effect of a maxillary low force expansion with a quadhelix on the anatomical structures of the viscerocranium and neurocranium is very much larger than is the case for individuals without clefts.

CONCLUSION

In the presence of a continuous cleft in the jaw and palate area, orthodontic forces (quadhelix) are apparently already sufficient to allow a skeletal expansion of the maxilla. Maxillary expansion using the quadhelix appliance represents a reasonable alternative to using conventional rapid maxillary expansion appliances among cleft patients.

In vitro validated finite element method model for a human skull and related craniofacial effects during rapid maxillary expansion

This paper presents the biomechanical effects on the craniofacial complex during rapid maxillary expansions (RME), by using an in vitro experiment compared with a three-dimensional (3D) finite element model of a human skull. For this purpose, a dry human skull with artificially constructed teeth was used. In addition, a 3D finite element model including the craniofacial sutures was developed based on computed tomography (CT) scans. Initially, two types of models were analysed. In the first model, the total activation of the jackscrew device was applied in one step. In the second model, more steps were applied, taking into account the phenomenon of stress relaxation during RME treatment. Afterwards, a parametric analysis of the finite element method model was performed using three more models in order to evaluate the influence of craniofacial sutures. Both in vitro and finite element results refer to the openings of four critical points (MI, UM, EM, and CN) on the left and right maxilla. Results show that the maxillae open in a pyramidal shape and that the degree of sutures ossification influences the displacement distribution on the craniofacial complex much more than the phenomenon of stress relaxation. The areas of the maximum stresses and displacements were also determined.

An evaluation of the influence of orthodontic adhesive on the stresses generated in a bonded bracket finite element model

The objective of this study was to evaluate the stresses generated in the bracket-cement-tooth continuum by a tensile load case when the physical and geometric properties of cement are varied. A 2-stage approach was used. In the first stage, a validated 3-dimensional finite element model of the bracket-cement-tooth system was constructed that consisted of 15,324 nodes and 2971 finite elements. Bracket base geometry was held constant; the physical properties (elastic modulus; Poisson's ratio) and geometry (lute thickness) of the cement varied. A simplified 2-dimensional model was then developed to investigate the localized effects of the cement lute thickness and the shape of the lute periphery on the stress distribution in the system. Small increases in stress were recorded under load within the cement as the rigidity of the cement increased. Similarly, Poisson's ratio values above 0.4 appeared to have a small influence on the major principal stresses in the impregnated wire mesh layer when a tensile force was applied. Variation in lute thickness was shown to have an influence on the distribution of major principal stresses within the cement lute. Increased stresses were recorded at the lute periphery as the lute dimensions increased. The morphologic features of the lute periphery also appeared to have had a significant effect on the performance of an orthodontic adhesive. Acute cement-enamel angles resulted in an increased chance of singularity development and attachment failure. The physical properties and thickness of the cement lute and the shape of the cement lute periphery contribute to the stress distribution within the bracket-cement-tooth continuum and, therefore, the quality of orthodontic attachment provided.