Effects of mandibular advancement surgery on the temporomandibular joint and muscular and articular adaptive changes—a systematic review

Exploring the relationship between the number of systematic reviews and quality of evidence: an orthognathic surgery-based study

OBJECTIVE

We analyzed the quality and quantity of systematic reviews (SRs) of orthognathic surgery, the most frequently published topic in maxillofacial surgery.

STUDY DESIGN

We searched the PubMed database for SRs of orthognathic surgery with no restriction on the language of publication date. We assessed the certainty of evidence presented according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol and the Leiden Manifesto using the Grading of Recommendations Assessment, Development, and Evaluation approach. We analyzed the data using descriptive statistics, Pearson´s correlation test, and linear regression.

RESULTS

Of the 171 SRs evaluated, approximately one fifth presented evidence with a high level of certainty. The number of orthognathic surgery SRs has been increasing, and many SRs were published after very similar topics had already been published. There is no relationship between the impact factor and the certainty of evidence.

CONCLUSIONS

An excessive number of SRs of orthognathic surgery are published, and many SRs are superfluous, simply reporting previous findings. Clinicians should not base treatment decisions solely on the evidence presented in SRs, and journal editors and reviewers should evaluate these SRs more critically, particularly when they address topics that have already been covered in the literature.

Does Articular Disc Position Change Following Mandibular Setback Surgery?

BACKGROUND

Maintaining condyle position following bilateral sagittal split ramus osteotomy (BSSO) is crucial to minimizing postoperative relapse. However, the impact of BSSO on the articular disc position remains inconclusive.

PURPOSE

This study aimed to investigate the changes in articular disc position following setback BSSO surgery.

STUDY DESIGN, SETTING, AND SAMPLING

In this prospective cohort study, subjects with mandibular prognathism requiring setback BSSO were enrolled between August 2021 and June 2022 at the Oral and Maxillofacial Surgery Clinic, Faculty of Dentistry, Chiang Mai University, Thailand. Patients with surgical complications, loss of follow-up, or significant artifacts in their MR images were excluded.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLES

The predictor variable was time. The articular disc position was assessed at 3 time points, preoperatively (T0), 3 months postsurgery (T1), and 6 months postsurgery (T2).

MAIN OUTCOME

The primary and secondary outcome variables were the changes in articular disc position between T0-T2 and T0-T1, respectively. Articular disc position was coded as normal, anterior disc displacement with reduction (ADDwR), anterior disc displacement without reduction (ADDwoR), and anterior disc displacement without reduction and degenerative joint disease (ADDwoR + DJD).

COVARIATES

Covariate variables collected included age (years), sex (male or female), asymmetry (present or absent), surgical procedure (single jaw (BSSO) or bimaxillary surgery), and setback distance (millimeters).

ANALYSES

Friedman's test with 80% power and a significance level of 0.05 was employed. Pairwise comparisons were performed using the Dunn-Bonferroni posthoc test to identify statistically significant differences.

RESULTS

The study included 16 subjects, 6 females and 10 males, with a total of 32 TMJs. Subjects had a mean age of 23.75 (4.57) years. The proportion of TMJs with normal disc position postoperatively increased from 3 (9.4%) to 19 (59.4%). Statistically significant differences were found in the changes in disc position over time (P < .001).

CONCLUSIONS

Following setback BSSO, the articular discs underwent changes, with a majority of ADDwR cases transitioning to a normal position. Cases with ADDwoR also demonstrated disc reduction capability after surgery. The combined orthodontic treatment and setback BSSO appear to have an effect on articular disc position in skeleton class III patients.

Orthognathic surgery effects on temporomandibular joint compressive stresses

INTRODUCTION

This study tested orthognathic surgery effects on temporomandibular joint (TMJ) compressive stresses.

METHODS

Pre- (T1) and post-surgery (T2) cone-beam computed tomography images were collected from consenting subjects aged ≥15 years. Anatomical data were used to measure surgical changes in anteroposterior mandibular position and occlusal plane angle (FH-OP), estimate condylar loading areas (mm2 ) and calculate T1 and T2 TMJ and jaw muscle forces (N) during canine biting via numerical modelling. Analysis of covariance tested for sex and biting angle differences in T2 - T1 TMJ compressive stresses (TMJ force/loading area, MPa). Principal component analyses identified jaw muscle forces that accounted for changes in T2 - T1 TMJ loads. Regression analyses tested the correlations between surgical changes in mandibular position, FH-OP, TMJ loads and muscle forces.

RESULTS

Of 148 cases screened, 28 females and 16 males provided complete records. Condylar loading areas were significantly smaller (P = .024) for females vs males (124 ± 5 vs 144 ± 7 mm2 ). T2 - T1 differences in TMJ compressive stresses varied by surgical change, biting angle and sex. Overall, the largest increases in TMJ compressive stresses post-surgery were for females with mandibular setbacks where FH-OP angle decreased. T2 - T1 changes in jaw muscle forces had moderate (ipsilateral, λ = 4.59; η2  = 0.071) to large (contralateral, λ = 1.49; η2  = 0.31) effects on TMJ loads.

CONCLUSIONS

T2 - T1 differences in TMJ compressive stresses during canine biting were affected by surgical changes in mandibular position and occlusal plane angle, biting angle and sex. Surgical changes altered jaw muscle forces for the same biting conditions and, thus, affected TMJ loads and compressive stresses.

Condylar resorption following mandibular advancement or bimaxillary osteotomies: A systematic review of systematic reviews

Several systematic reviews have been published on the effects of mandibular surgery on condylar remodeling without reaching a consensus. The purpose of this systematic review of systematic reviews was to assess the impact of mandibular advancement or bimaxillary surgeries on condylar resorption. A literature search, using several electronic databases, was carried out by two reviewers independently. Article preselection was based on titles and abstracts, and final article selection based on full-text analysis of preselected studies. After final study selection, the quality of studies was assessed using the AMSTAR 2 tool. A decision algorithm was subsequently established to choose the best body of evidence. From an initial yield of 1'848 articles, 23 systematic reviews were identified for further analysis, with ten studies being included in the final selection. Despite the generally low quality of the reviews, certain associations could be made: young patients, female patients, and those with a high mandibular plane angle are more prone to condylar resorption following mandibular advancement osteotomies, especially if anterior rotation of the mandible is performed during surgery. Patients undergoing bimaxillary surgery also appear to have a higher risk of developing condylar resorption. In conclusion, these results confirm the multi-factorial nature of condylar resorption, stressing the need for well-controlled prospective studies with long-term follow-up to clearly identify potential risk factors associated with orthognathic surgery.

The Impact of Orthodontic Treatment on Masticatory Performance: A Literature Review

The aim of this narrative review was to evaluate the possible association between orthodontic therapy and improved masticatory function. A search strategy was conducted using the PubMed database for up to January 2020 using the keywords "mastication" and "orthodontics". Only human studies investigating mastication in orthodontics settings were selected. The search strategy resulted in 1,011 articles, out of which 57 were included in the final analysis. Investigations have generally agreed that masticatory and chewing functions improved post-orthodontic and orthognathic treatments. Studies also showed improvement in the quality of life of patients' post-orthodontic treatment. The articles examined reinforced that besides esthetic reasons, orthodontic therapy does improve the masticatory and chewing functions of individuals, ultimately enhancing their health-related quality of life.

Biomechanical Effects of Different Miniplate Thicknesses and Fixation Methods Applied in BSSO Surgery Under Two Occlusal Conditions

Purpose

Finite element analysis (FEA) was used to evaluate the effects of different thicknesses, numbers, and positions of the miniplate applied in bilateral sagittal split osteotomy (BSSO) under two occlusal conditions.

Methods

An FEA model of the mandibles was constructed and combined with different thicknesses (0.6 or 1 mm), number (one or two), positions (upper or lower) of a miniplate and was divided into six models. In addition, external forces were applied to the muscles to simulate the intercuspal position (ICP) and right unilateral molar clench. This study used the reaction force of the temporomandibular joints and the stress of the mandible as observation indexes.

Results

The results of this study show that, under ICP, the 0.6 mm lower model generated greater TMJ force reaction compared to the 0.6 mm upper model. The same trend was seen in the 1 mm lower model compared to the 1 mm upper model. Regarding the stress of the bone on the screw-implanted sites, under ICP, screw 10 showed greater stress than screw 2, and screw 11 showed greater stress than screw 3. The stress values of the miniplates showed, under ICP, point 1-c was greater than point 3-c, and point 1-b was greater than point 3-b.

Conclusion

In the case of BSSO mandibular advancement surgery, implanting the miniplate at the upper position can reduce the force on the TMJ and the stress on the distal segment of the mandible. The miniplate can also resist the tensile stress more effectively. In addition, implanting two miniplates with thinner sizes may be an alternative in clinical practice.

Incidence and management of condylar resorption after orthognathic surgery: An overview

Objective

Condylar resorption (CR) is one of the major post-surgical complications of orthognathic surgery. This systematic review (SR) aimed to evaluate epidemiological data, risk factors, and therapeutical management of CR.

Methods

Six databases were screened by two investigators until September 2020 to obtain all SRs. After reading the titles and abstracts, eligible SRs were determined and data extraction was performed. Using the latest version of A Measurement Tool to Assess Systematic Reviews, the methodological quality of the included SRs was determined.

Results

Ten SRs with low or critically-low methodological quality were included in this review. Mandibular hypoplasia on the sagittal plane and hyperdivergent growth pattern on the vertical plane were the most common skeletal alterations in which CR could occur after orthognathic surgery. Post-operative condylar changes were analyzed both on two-dimensional and three-dimensional (3D) radiographic examinations. The incidence of CR was not related to the fixation method. Based on the severity of the pathological conditions, management of CR can include conservative or surgical therapy.

Conclusions

Despite the limited evidence in literature, CR is considered a consequence of orthognathic surgery. However, an accurate diagnosis of CR and a better orthognathic surgical planning must include 3D radiographic examinations to improve pre- and post-surgical comparison. Well-designed studies with long-term follow-up and 3D data are needed to clarify the findings of this analysis..

Long-term patient satisfaction and the sense of coherence - a longitudinal study 10-15 years after orthognathic surgery

OBJECTIVE

This study focuses on evaluating the long-term treatment outcome (10-15 years) and patient satisfaction after orthognathic treatment with bisagittal split osteotomy (BSSO). Furthermore, the aim was to evaluate whether the psychosocial factor, sense of coherence (SOC) associates with long-term patient satisfaction.

MATERIALS AND METHODS

Study sample consisted of 57 patients who had orthognathic treatment with BSSO. Self-completion questionnaires were distributed approximately 1.8 years and 10-15 years after surgery to evaluate treatment outcome. SOC was evaluated with a 12-scale questionnaire 10-15 years after the surgery.

RESULTS

After 10-15 years following BSSO, 96% of patients were highly or moderately satisfied with the treatment outcome and none expressed dissatisfaction. Less educated patients were more satisfied with the treatment outcome than those with a higher educational level. Patients who felt clear improvement in their facial appearance expressed higher satisfaction than those experiencing only minor facial improvement. Furthermore, patients with improvement in orofacial pains and headaches more often expressed high satisfaction than those without improvement of these symptoms. Patients with strong SOC seemed to have somewhat higher scores for functional aspects of long-term treatment outcome.

CONCLUSIONS

Post-treatment satisfaction with orthognathic treatment appears to be long-lasting. Psychosocial factors may play a role in long-term post-treatment satisfaction. Our study strongly suggests that psychosocial factors should be taken into account in the treatment planning of orthognathic patients.

Incidence of condylar resorption after bimaxillary, Lefort I, and mandibular surgery: an overview

The aim of the present overview was to evaluate the outcomes of systematic reviews to determine the incidence of condylar resorption in patients submitted to orthognathic surgery and analyze whether the risk of developing this condition is related to a specific type of surgery. Searches were conducted in the PubMed/MEDLINE, Embase, and Cochrane electronic databases for systematic reviews with quantitative data on condylar resorption due to any type of orthognathic surgery for dentoskeletal deformities published up to May 25, 2019. The AMSTAR 2 and Glenny tools were applied for the quality appraisal. Five systematic reviews were included for analysis. Only one article was considered to have high quality. Among a total of 5128 patients, 12.32% developed condylar resorption. From those patients, 70.1% had double jaw surgery, 23.4% had mandibular surgery alone, and in 6.5% a Lefort I technique was used. Based on these findings, bimaxillary surgery could be considered a risk factor for condylar resorption. However, these results should be interpreted with caution, since other factors, such as pre-operative skeletal deformities, type of movement, and type of fixation, can contribute to the development of this condition. Further studies should consider reporting main cephalometric data, temporomandibular diagnosis, hormonal levels, and tomographic measures before and after the surgery at least every 6 months during the firsts two years to identify accurately risk factors for condylar resorption.

Does the Stomatognathic System Adapt to Changes in Occlusion? Best Evidence Consensus Statement

PURPOSE

The purpose of this Best Evidence Consensus Statement was to evaluate the existing literature on the stomatognathic system's ability to adapt to occlusal changes.

MATERIALS AND METHODS

The search term stomatognathic system was not useful as it resulted in over 400,000 results nor was the search term temporomandibular joint adaptation with 738 results due to the large number of references not related to the topic. The terms stomatognathic system adaptation to occlusal changes (186 results), teeth flexion (139 results), muscle adaptation to dental occlusion (278 results), and occlusal changes and neuroplasticity (11 results) provided the best selection of articles related to the topic. Limiting the above searches to systematic reviews and randomized controlled clinical trials resulted in multiple publications that were related to the question.9-13 Other literature reviews, data-based publications, and expert opinion resources have been included due to their relationship to the question.

RESULTS

From the extensive list of search results, 242 articles were determined to be potentially related to the focus question and were evaluated with 56 being included in this paper. It was determined that the stomatognathic system adapts to occlusal changes through the temporomandibular joint, muscles, teeth and bone. The dynamically modified periosteum on the articulator surfaces of the condyle and fossa has a unique load-bearing morphology with 3 subarticular layers of fibrocartilage that absorb and dissipate both peak (impact) and sustained loads. Adaptability of the TMJs and muscles can be documented through studies where artificially produced occlusal interferences were placed in patients and those study participants with normal temporomandibular joints (TMJs) adapted fairly well whereas those with a previous history of temporomandibular disorders (TMD) did not adapt as well.

CONCLUSIONS

Available evidence indicates patients generally adapt to the occlusal change inherent in orthodontic treatment, mandibular advancement surgery, and the use of mandibular advancement devices. The head and neck muscles also adapt to occlusal changes in patients without a history of TMD. The dentition adapts to changes through the bone and periodontal ligaments as well as the ability of teeth to undergo slight flexion under masticatory loading. This article is protected by copyright. All rights reserved.

Condylar form alteration on skeletal class II patients that underwent orthognathic surgery: An overview of systematic reviews

Background

Bilateral sagittal split osteotomy (BSSO) is commonly considered as the surgical technique of election for the treatment of skeletal class II with mandibular hypoplasia. After orthognathic surgery, condylar resorption can occur as a surgical relapse, which may affect the temporomandibular joint. Objective: This study aimed to summarise published systematic review that assess if orthognathic surgery with mandibular advancement performed on skeletal class II patients results in condylar form alteration.

Material and Methods

A literature search was performed using the electronic databases PubMed, Web of Science, Cochrane Library, Embase along with several sources of grey literature. Selection Criteria: Inclusion criteria were systematic reviews published until December 2019, of skeletal class II patients aged more than 18 years old that underwent BSSO with mandibular advancement surgery. Data collection: The electronic search identified 37 publications. Four publications fulfilled the inclusion criteria and were included in this meta-analysis. Qualitative assessment of the selected studies was performed using the Assessment of Multiple Systematic Reviews – AMSTAR 2 checklist.

Results

Four systematic reviews were included in this review. Despite its low incidence all studies reported condylar resorption. However, there were methodological limitations in all assessed articles.

Conclusions

The alteration of the condylar form may be a consequence of BSSO with mandibular advancement surgery. Additional high quality prospective research assisted by 3D-imaging technology is needed to allow more definite conclusions.

Key words:Evidence-based orthodontics, TMJ, Class II, mandibular advancement, malocclusion, Angle class II.

Quantitative appraisal of bilateral sagittal split osteotomy impact on the loading of temporomandibular joint

Bilateral sagittal split osteotomy is one of the most frequently performed operations in orthognathic surgery. The health of the temporomandibular joint (TMJ) is an important prerequisite for its functionality. The aim of this finite element study was to assess the developed stresses during mouth opening after bilateral sagittal split osteotomy. Different osteotomy gap widths and disc positions were evaluated. Computed tomography and magnetic resonance data of a dentulous cadaver head were used in order to create two finite element models simulating split distances of 5 and 10 mm, respectively. The fixation of the distal and proximal segments was made by a four- or a six-hole titanium mini plate and four monocortical screws respectively. For both models, three different situations of the articular disc were created: a physiological disc position, anterior disc displacement and posterior disc displacement. The mandible was vertically displaced in the midline in order to simulate a mouth opening of 20 mm. The simulation showed high stresses in the area of the titanium plates (up to 850 MPa), implying an increased risk of material failure. High stresses were found within the discs in the models with normal disc position and anterior disc displacement as well (up to 8 MPa), indicating a higher risk of developing craniomandibular disorders. Regarding the stresses within the fixation screws, the highest values were recorded in the area of the upper thread. The degree of mandibular advancement after a bilateral sagittal split osteotomy affects the stress balance in the mandible and the articular discs during mouth opening.

Temporomandibular disorders in Class II malocclusion patients after surgical mandibular advancement treatment as compared to non-treated patients

BACKGROUND

Severe malocclusions may cause functional and aesthetic problems and symptoms of temporomandibular disorders (TMD). Studies have investigated association between malocclusions and TMDs and shown controversial findings.

OBJECTIVE

Purpose of this investigation was to examine the prevalence of TMD sub-diagnoses, using Diagnostic Criteria for the TMD (DC/TMD), in patients with Class II malocclusion and retrognathic mandible who had undergone mandibular advancement surgery 4-8 years previously, and to compare their frequencies with non-treated patients with a similar pre-existing condition.

METHODS

Study cohort comprised 151 patients who had orthognathic treatment due to mandibular retrognathia in 2007-2011. Seventy-seven (51%) participated in the study (Group 1). Group 2 comprised 22 patients who were planned for orthognathic treatment but had not started their treatment. Patients filled in the Finnish version of the DC/TMD Symptom Questionnaire and were examined using to the DC/TMD Axis I. DC/TMD Symptom Questionnaire were inquired by phone from 24 of the 74 patients who did not participate in the study.

RESULTS

Results showed that Group 2 had more myalgia (13% vs 50%, P < 0.001) and arthralgia (18% vs 65%, P < 0.001) sub-diagnoses than Group 1. A tendency was noted that Group 2 had more pain-related TMD symptoms than Group 1. No differences were found between Groups 1 and 3 in gender and age distribution or frequency TMD symptoms.

CONCLUSION

Prevalence of especially pain-related TMD diagnoses was higher in Group 2 compared to Group 1, thus indicating a possible beneficial effect of this treatment for TMD.

Changes in the alveolar bone thickness of maxillary incisors after orthodontic treatment involving extractions - A systematic review and meta-analysis

Background

Orthodontic treatment involving en-masse retraction of incisors following premolar extractions, may induce morphological alterations of the alveolar bone surrounding the anterior teeth.

Objective

To assess changes in alveolar bone thickness around the incisors of extraction patients measured with CBCT.

Material and Methods

An electronic search was conducted in PubMed, Scopus, Embase and Cochrane Library, using search terms, with no limitation on publication date, up to April 2018. The articles selected for analysis included randomized controlled trials, case-control studies and cohort studies of patients treated with fixed appliances and premolar extractions, which had measured alveolar bone thickness with CBCT before and after treatment. Changes in bone thickness were calculated and the heterogeneity of the studies was assessed using the I2 and Cochran’s Q tests.

Results

Of the 136 articles identified in the initial search, 19 were related to the review subject. After removing a further 14 that did not meet the inclusion criteria, 5 articles were selected for analysis. All five were retrospective studies of medium quality. The main changes in alveolar bone thickness were found in the labial cervical third of the central incisor, presenting increases of 0.4-0.64 mm. On the palatal side the results varied considerably.

Conclusions

A significant increase in alveolar bone thickness occurs in the labial cervical third of the central incisor. These changes may be influenced by incisor position and inclination, the orthodontic technique and mechanics employed, the timing of the final CBCT scan and the bone remodeling capacity during en-masse retraction.

Key words:Cone-beam computed tomography, alveolar bone, orthodontics.

Condylar resorption in orthognathic patients after mandibular bilateral sagittal split osteotomy: a systematic review

Objective

To systematically search the literature and assess the available evidence regarding the incidence and quantification of condylar resorption following bilateral sagittal split osteotomy (BSSO) of the mandible in orthognathic patients.

Search methods

Electronic database searches of published and unpublished literature were performed. The reference lists of eligible studies were hand searched for additional studies.

Selection criteria

Randomized clinical trials (RCTs), prospective, and retrospective studies with patients of any age that underwent BSSO were included.

Data collection and analysis

Study selection, data extraction, and risk of bias assessment were performed individually and in duplicate.

Results

One RCT, 3 prospective, and 10 retrospective studies were included in this review. The lack of standardized protocols and the high amount of heterogeneity precluded a valid interpretation of the actual results through pooled estimates. There was a substantial consistency among studies, however, that young, female patients with mandibular deficiency and high mandibular plane angle, submitted to surgical counterclockwise rotation of mandibular segments, were more prone to a higher risk for condylar resorption after BSSO. The level of evidence was found to be low given the high/serious risk of bias in all included studies.

Conclusions

Condylar resorption should be taken into account as a potential postsurgical complication after BSSO. However, its incidence and quantification need precautious interpretation owing to the low level of evidence and the high heterogeneity of studies. Additional high-quality prospective research assisted by 3D imaging technology is needed to allow more definitive conclusions.

Registration

Study not registered.

Conflict of interest

None.

Corticotomies as a surgical procedure to accelerate tooth movement during orthodontic treatment: A systematic review

Background

One of the main aims of orthodontists is to reduce the treatment time as much as possible, particularly in view of the rise in demand for orthodontic treatment among adult patients. The objective of this systematic review was to examine the effectiveness of corticotomy as a surgical procedure that accelerates orthodontic tooth movement, together with its possible adverse effects.

Material and Methods

A systematic review of articles in 4 databases, Pubmed, Cochrane, Scopus and Embase, complemented by a manual search, identified 772 articles. The duplicates were eliminated and a critical reading of titles and abstracts led to the rejection of articles that did not meet the objectives of the review, leaving 69. After reading the full text of these articles, 49 were excluded because they did not meet the inclusion criteria. On applying the CONSORT criteria as a quality filter, a further 4 were eliminated due to low quality. Finally, 16 articles (4 systematic reviews and 12 controlled trials) were reviewed.

Results

All the studies agree that corticotomy prior to orthodontic treatment accelerates dental movement, reducing the treatment time. With regard to side-effects, no periodontal damage was found, although this was only studied in the short term.

Conclusions

The evidence regarding the results of corticotomy is limited, given the small number of quality clinical studies available. Before this procedure is included as a routine practice in dental surgeries, studies of higher methodological quality are required, studying a greater number of individuals and examining the possible long-term adverse effects and the cost/benefit of the procedure.

Key words:Corticotomy, orthodontics, adults, accelerated tooth movement, osteotomy.

[Temporo-mandibular joints and orthognathic surgery]

Temporo-Mandibular Joints (TMJ) and orthognathic surgery are closely linked. In the past, some authors have even described (with mixed results) the correction of some dysmorphosis through direct procedures on the TMJs. Nowadays, performing orthognathic surgery involves the TMJ in three different occasions: (1) TMJ disorders potentially responsible for dento-maxillary dysmorphosis, (2) effects of orthognathic surgery on TMJs, and (3) condylar positioning methods in orthognathic surgery. These three chapters are developed in order to focus on the close relationships between TMJ and orthognathic surgery. Some perspectives close this article.