Median mandibular flexure at different mouth opening and its relation to different facial types: A prospective clinical study

Median mandibular flexure-the unique physiological phenomenon of the mandible and its clinical significance in implant restoration

Mandibular flexure, characterized by unique biomechanical behaviors such as elastic bending and torsion under functional loading, has emerged as a crucial factor in oral clinical diagnosis and treatment. This paper presents a comprehensive review of the current research status on mandibular flexure, drawing insights from relevant studies retrieved from the PubMed database (www.ncbi.nlm.nih.gov/pubmed), including research conclusions, literature reviews, case reports, and authoritative reference books. This paper thoroughly explores the physiological mechanisms underlying mandibular flexure, discussing different concurrent deformation types and the essential factors influencing this process. Moreover, it explores the profound implications of mandibular flexure on clinical aspects such as bone absorption around dental implants, the precision of prosthesis fabrication, and the selection and design of superstructure materials. Based on the empirical findings, this review provides crucial clinical recommendations. Specifically, it is recommended to exert precise control over the patients mouth opening during impression-taking. Those with a high elastic modulus or bone-tissue-like properties should be prioritized when selecting superstructure materials. Moreover, this review underscores the significance of customizing framework design to accommodate individual variations in facial morphology and occlusal habits. Future research endeavors in this field have the potential to advance clinical diagnosis and treatment approaches, providing opportunities for improvement.

Biomechanical Implications of Mandibular Flexion on Implant-Supported Full-Arch Rehabilitations: A Systematic Literature Review

BACKGROUND

Mandibular flexion (MF) is a complex biomechanical phenomenon, which involves a deformation of the mandible, due mainly to the contraction of the masticatory muscles, and it can have numerous clinical effects. The deformation of the lower jaw caused by mandibular flexion is generally very small, and it is often overlooked and considered irrelevant from a clinical point of view by many authors; however, it should be important to remember that median mandibular flexure (MMF) has a multifactorial aetiology. The main aim of the current systematic review is to highlight the different factors that can increase MF in order to help clinicians identify patients to whom they should pay more attention. As a secondary outcome, we wanted to analyse the preventive measures and suitable techniques to be adopted to minimise the negative effects of this phenomenon on oral fixed rehabilitations.

METHODS

The review, which was carried out in accordance with the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" (PRISMA) flowchart, was recorded in the "International Prospective Register of Systematic Reviews" (PROSPERO). As research questions, "Patient/Population, Intervention, Comparison and Outcomes" (PICO) questions were employed. Using the ROBINS-I technique, the risk of bias in non-randomised clinical studies was evaluated.

RESULTS

The initial electronic search identified over 1300 potential articles, of which 54 studies were included in this systematic review. Information regarding the relationship between MF and individual factors, mandibular movements, impression taking, and fixed rehabilitations were obtained.

CONCLUSIONS

The studies included in this systematic review showed that MF is greater during protrusive movements, in the posterior areas of the lower jaw, and in patients with brachial facial type, greater jaw length; small gonial angle; and less density, length, and bone surface of the symphysis. The biomechanical effects of mandibular flexion on fixed restorations are debated. Prospective clinical and radiological observational studies should be conducted to evaluate the potential short-, medium-, and long-term consequences of MF.

Mandibular Flexure and Its Significance: An In Vivo Cone Beam-Computed Tomography Proof-of-Concept Study

The aim of this study was to assess intra-arch mandibular dimensional changes that may occur during mouth opening using cone beam-computed tomography (CBCT). Fifteen patients in need of any type of treatment whose execution considered a pre- and post-CBCT assessment consented and were enrolled. CBCTs were taken with the following settings: 90 kV, 8 mA, field of view (FOV) 140 by 100 mm (height and diameter), Voxel size 0.25 mm (high resolution). The pre-CBCT was executed in the maximum mandibular opening (MO), while the post-CBCT was in the maximum intercuspation (MI). A thermoplastic stent with radiopaque fiducial markers (steel ball bearings) was fabricated for each patient. Measurements were made using radiographic markers between contralateral canines and contralateral first molars and between ipsilateral canines and first molars on both sides. Paired t-tests were performed to evaluate the difference between open and closed positions on these four measurements. In the MO position were registered a significative tightening of the mandible at the canine (-0.49 mm, SD 0.54 mm; p < 0.001) and molar points (-0.81 mm, SD 0.63 mm; p < 0.001) and a significative shortening of the mandible on the right (-0.84 mm, SD 0.80 mm; p < 0.001) and left sides (-0.87 mm, SD 0.49 mm; p < 0.001). Within the study limitations, mandibular flexure determined a significant shortening and tightening between maximum intercuspation to maximum opening positions. Mandibular dimensional changes should be considered in light of other patient factors in the treatment planning of implant positioning and long-span complete arch implant-supported fixed prostheses in order to avoid technical complications.

Clinical Influence of Mandibular Flexure on Oral Rehabilitation: Narrative Review

AIM

The current paper aims to review mandibular flexure and its clinical implications in the field of oral rehabilitation. Mandibular flexure is a deformity of the mandible, which occurs during jaw movements.

METHODS AND MATERIALS

An electronic database search was conducted using the PRISM model, with a total of 49 articles included.

RESULTS

Mandibular flexure affects various stages of oral rehabilitation treatments. Effects of mandibular flexure are more significant in periodontal patients, and in implant-supported restorations, compared to natural teeth, due to differences in the force absorption by the periodontal ligament. Various adjustments must be made to the prosthodontic framework to enable long-term survival of the restorative treatments.

CONCLUSIONS

Dental practitioners should pay attention to the following: (1) digital impressions are preferred over conventional; (2) mouth opening should be kept to a minimum (as possible, up to 10-20 mm) while also avoiding any anterior movements of the mandible (protrusion); (3) the number of abutment teeth should be kept to a minimum; (4) structures in the lower jaw should be splitted; (5) non-rigid connectors should be used to reduce the effort exerted; (6) in periodontal patients, the preference is for short-span restorations and non-rigid connectors; (7) in implant-supported restorations, it is preferable to divide the framework into two or three segments, utilizing rigid materials with a low elastic modulus. There is no agreement in the literature about the preferred location of the implants in the jaw.

The effect of mandibular flexure on the design of implant-supported fixed restorations of different facial types under two loading conditions by three-dimensional finite element analysis

Objective: Investigating the biomechanical effects of mandibular flexure (MF) on the design of implant-supported fixed restorations in edentulous jaws of different facial types.

Methods: Three-dimensional finite element models were established to analyze mandibular displacement and stress distribution of implant-supported fixed restorations (four or six implants, different implant numbers and sites, and the design of the superstructure across the dental arch in one or two or three pieces, under the loading conditions of maximum opening or right unilateral molar occlusion) in mandibular edentulous patients of three different facial types (brachyfacial, mesofacial, and dolichofacial types).

Results: The brachyfacial type presented higher mandibular flexure and stress in the overall restorative system, followed by the mesofacial and dolichofacial types. During jaw opening and occlusal movements, the one-piece framework showed the lowest bone stress values surrounding the anterior implants and gradually increased to the distal position, and the three-piece framework showed the highest stress values for peri-implant bones. Also, the split framework could greatly increase the stress on abutments and frameworks. Moreover, fixed implant prostheses with cantilevers can generate high amounts of biomechanical stress and strain on implants and surrounding bones. The bone surrounding the anterior implant increased in stress values as the most distal implants were more distally located regardless of frameworks. The zirconia framework demonstrated higher stresses than the titanium framework.

Conclusion: The design of edentulous fixed implant-supported restorations can be optimized for facial types. For patients of the brachyfacial type or with high masticatory muscle strength, the non-segmented framework without a cantilever provides an optimal biomechanical environment.

Evaluation of median mandibular flexure values in dentulous and edentulous subjects by using an intraoral digital scanner

PURPOSE

Mandibular flexure is a crucial phenomenon that may affect the success of rigid bilateral mandibular prosthetic treatment. The aim of this study was to determine the amount of median mandibular flexure (MMF) that occurs during mouth opening from anterior to posterior mandible in seven different regions, in different age and gender groups of both dentulous and edentulous subjects, using an intraoral digital scanner.

MATERIALS AND METHODS

In this study, the mandibular arch of 56 dentulous and 35 edentulous individuals were scanned with an intraoral scanner at both the minimum mouth opening (MnMO) and the maximum mouth opening (MxMO). MMF values were calculated by subtracting the distance value at the MxMO from the distance between the reference points at the MnMO at seven different mandibular regions of dentulous and edentulous subjects. In addition, the left and right side MMF values were measured. All data were analyzed statistically (α = .05).

RESULTS

MMF value increased linearly from anterior to posterior mandible in both dentulous and edentulous individuals. The differences in MMF values were not statistically significant according to side (left/right), age, or gender (P > .05). No significant differences were found between the mean MMF values of the same region in both dentulous and edentulous individuals (P > .05).

CONCLUSION

MMF was seen in different regions of the mandibles of both edentulous and dentulous individuals measured at the MxMO. Mandibular flexure should be considered for the success and prognosis of the long-span and rigid prostheses.

A new mandibular deformation index predicts amount of bone deformation in edentulous patients treated with an implant-supported fixed prosthesis

PURPOSE

The present study was performed to examine the mandibular deformation during mouth opening in edentulous patients, treated with an implant-supported fixed prosthesis using strain gauges, and identify factors affecting deformation.

METHODS

Twenty patients with a fully edentulous mandible who received either 4 or ≥6 implants were included. The distal-most implants were placed mesial to the mental foramen (premolar region) in patients with 4 implants and distal to the mental foramen (molar region) in patients with ≥6 implants. Mandibular deformation during mouth opening was measured using strain gauges in two directions: anteroposterior direction and lateral direction between the distal-most implants on the left and right sides (arch width). The mandibular anatomy was evaluated using computed tomography.

RESULTS

Arch width reduction between the left and right implants during mouth opening ranged from 47.38 to 512.80 µm; the range of deformation was 0.12 to 15.14 µm in the anteroposterior direction. Furthermore, a significant positive correlation was noted between arch width reduction in the premolar region and the ratio between the symphyseal bone height and width (P = 0.0003, r = 0.72).

CONCLUSION

The reduction in arch width was higher in the molar region than in the premolar region during mouth opening. Moreover, the reduction could be high in the mandibular symphyseal bone because of its greater height and lesser width. The ratio between the symphyseal bone height and width is defined as the mandibular deformation index (MDI) and is used to predict the rate of mandibular bone deformation.

Management of Fractured Zirconia Complete Arch Fixed Implant-Supported Prosthesis Caused by Misfit Due to Diverse Implant Components: A Case Report

Recently, monolithic zirconia complete-arch fixed implant-supported prosthesis (CAFIP) has been shown to be an effective means of managing patients with edentulism or terminal dentition. Prosthetic complications have been reported to be rare, as long as there is proper treatment planning, prosthetic space and careful attention during fabrication of the prosthesis. Few reports exist in the literature that have described the management of patients with fractured zirconia CAFIP. This case report describes the successful management of a female patient with a midline fracture of a monolithic zirconia CAFIP supported by 6 dental implants in the mandibular arch. The fractured prosthesis had adequate prosthesis thickness with no distal cantilever, and opposed a similar prosthesis in the maxilla. However, upon careful analysis, diverse implant components were identified as the primary contributory factor to prosthetic misfit, and subsequent fracture. This is a new factor that requires attention by clinicians and dental laboratory technicians due to the increased prevalence of patients with preexisting dental implants. This article describes the considerations related to diverse implant components and connections from different implant manufacturers, choice of favorable implant-abutment design, technique for mitigation, and importance of passive fit for zirconia CAFIP.

Elastic deformation of the mandibular jaw revisited-a clinical comparison between digital and conventional impressions using a reference

Objectives

Due to the partly strongly differing results in the literature, the aim of the present study was to investigate a possible deformation of the mandible during mouth opening using an intraoral scanner (IOS) and a conventional impression for comparison with a reference aid.

Materials and methods

Four steel spheres were reversibly luted in the mandibular (n = 50) with a metallic reference aid at maximum mouth opening (MMO). Two digital impressions (Trios3), at MMO and at slightly mouth opening SMO and a conventional impression (Impregum), were taken as the measuring accuracy of the reference structure was already known. Difference between MMO-SMO for digital impressions and deviations between digital and conventional (SMO) were calculated. Furthermore, the angle between the normal vectors of two constructed planes was measured. Statistical analysis was performed with SPSS25.

Results

Deviations for linear distances ranged from −1 ± 3 μm up to 17 ± 78 μm (digital impressions, MMO-SMO), from 19 ± 16 μm up to 132 ± 90 μm (digital impressions, SMO), and from 28 ± 17 μm up to 60 ± 52 μm (conventional impressions, SMO). There were no significant differences for digital impressions (MMO-SMO), and there were significant differences between the conventional and digital impressions at SMO.

Conclusions

Based on the results of the present study, no mandibular deformation could be detected during mouth opening with regard to the digital impressions. The results were rather within the measuring tolerance of the intraoral scanner.

Clinical relevance

Based on the present study, no deformation of the mandibular during mouth opening could be observed at the level previously assumed. Therewith related, dental techniques related to a possible mandibular deformation therefore should be reconsidered.

Assessment of the relationship between maximum occlusal force and median mandibular flexure in adults: A clinical trial study

Aim:

The narrowing of the mandible during opening and protrusion movements is defined as median mandibular flexure (MMF). MMF is caused by the attachment of mandibular muscles; therefore, it can be assumed that a greater amount of maximum occlusal force (MOF) may cause more flexion and could affect the survival of dental and implant restorations. The purpose of this study was to evaluate any relationship between MOF and MMF in a sample of adults.

Settings and Design:

In vivo – comparative study.

Materials and Methods:

In this descriptive, cross-sectional, nondirectional study, a sample of 90 volunteers were recruited (45 men and 45 women). MOF was measured by applying the strain gauge receptor to the first molar region, and MMF was measured by calculating the variation in the intermolar distance by a digital caliper with an accuracy of 0.01 mm using an impression and resulted in the stone cast during the maximum opening and closed-jaw positions. The body mass index (BMI) also was calculated.

Statistical Analysis:

Data were analyzed using the SPSS software (version 23) inferential and descriptive statistics, linear regression, and Pearson correlation coefficient. P < 0.05 was considered statistically significant.

Results:

There was no statistically significant relationship between MOF and MMF (P = 0.78), but there was a significant association between MOF and BMI (P < 0.001, r = 0.475) and gender.

Conclusion:

Although MOF and MMF are both important and effective factors in the success of prosthetic restorations, one cannot be expected by the other and both should be considered in the treatment plan separately.

Influence of cone beam CT volume orientation on alveolar bone measurements in patients with different facial profiles

OBJECTIVES

To evaluate the influence of cone beam CT (CBCT) volume orientation on alveolar bone measurements for dental implant planning using CBCT in patients with different facial profiles.

METHODS

74 CBCT volumes were selected from a database and classified according to the facial profile of the patient. Height and width measurements of the alveolar bone were carried out with the volume of the mandible in two different orientations: occlusal plane and mandibular base parallel to the horizontal plane. The data were subjected to the mixed model methodology for repeated measures, through the PROC MIXED procedure. Multiple comparisons were performed by Tukey Kramer test (α = 0.05).

RESULTS

Alveolar bone width was significantly greater when the CBCT volume was oriented with the mandibular base parallel to the horizontal plane, for all facial profiles (p ≤ 0.05). Alveolar bone height was significantly higher (p ≤ 0.05) for dolichofacial individuals when compared to that of mesofacial and brachyfacial individuals, who did not differ significantly between each other (p > 0.05), regardless of the CBCT volume orientations used in this study.

CONCLUSIONS

CBCT-based alveolar bone width is increased when the image volume is oriented with the mandibular base parallel to the horizontal plane and dolichofacial individuals present greater alveolar bone height.

Hominoid arcade shape: Pattern and magnitude of covariation

The shape of the dental arcade and canine size distinguish extant humans from all apes. Humans are characterized by a parabolic arcade with short postcanine tooth rows and small canines, whereas apes have long, U-shaped arcades with large canines. The evolutionary and biomechanical mechanisms underlying arcade shape differences between and within groups are not well understood. It is unclear, for example, whether evolutionary changes in the covariation among modules comprising the upper and lower jaws are the cause and/or consequence of different arcade shapes. Here we use 3D geometric morphometric methods to explore to what extent the morphological differences in arcade shape between living hominoids are related to differences in covariation of upper and lower jaws, and the premaxilla and the maxilla. We show that all extant hominoids follow a very similar covariation pattern between upper and lower dental arcades, as well as between the premaxilla and the maxilla. We find comparably high magnitudes of covariation between the premaxilla and the maxilla in all groups. Between the upper and lower jaws, levels of covariation are similar in apes (Pan, Gorilla, Pongo, and Hylobates), but overall lower in extant humans. Our results demonstrate an independence of the pattern of arcade shape covariation from dental spatial arrangements. Importantly, we show that a shared hominoid pattern of covariation between premaxilla and maxilla together with the covariation of upper and lower jaw is consistent with major evolutionary arcade shape changes in hominoids. We suggest that with the reduction of canine and diastema size in hominins, the incisors move posteriorly and the tooth row becomes more parabolic. Our study provides a framework for addressing questions about fossil hominin dentognathic diversity, including inter- and intraspecific variation and associations of upper and lower jaw morphology.

Analysis of potential dynamic concealed factors in the difficulty of lower third molar extraction

BACKGROUND

The purpose of this study was to identify potential concealed variables associated with the difficulty of lower third molar (M3) extractions.

MATERIAL AND METHODS

To address the research purpose, we implemented a prospective study and enrolled a sample of subjects presenting for M3 removal. Predictor variables were categorized into Group-I and Group-II, based on predetermined criteria. The primary outcome variable was the difficulty of extraction, measured as extraction time. Appropriate univariate and multivariate statistics were computed using ordinal logistic regression.

RESULTS

The sample comprised of 1235 subjects with a mean age of 29.49 +/- 8.92 years in Group-I and 26.20 +/- 11.55 years in Group-II subjects. The mean operating time per M3 extraction was 21.24 +/- 12.80 and 20.24 +/- 12.50 minutes for Group-I and Group-II subjects respectively. Three linear parameters including B-M2 height (distance between imaginary point B on the inferior border of mandibular body, and M2), lingual cortical thickness, bone density and one angular parameter including Rc-Cs angle (angle between ramus curvature and curve of spee), in addition to patient's age, profile type, facial type, cant of occlusal plane, and decreased overbite, were found to be statistically associated ( p < or = 0.05) with extraction difficulty under regression models.

CONCLUSIONS

In conclusion, our study indicates that the difficulty of lower M3 extractions is possibly governed by morphological and biomechanical factors with substantial influence of myofunctional factors.

PRACTICAL IMPLICATIONS

Preoperative evaluation of dynamic concealed factors may not only help in envisaging the difficulty and planning of surgical approach but might also help in better time management in clinical practice.

Clinical Measurement of Maximum Mouth Opening in Children of Kolkata and Its Relation with Different Facial Types

INTRODUCTION

Maximal opening of mouth is described as the greatest distance between incisal edge of maxillary central incisor to the incisal edge of mandibular central incisor, when the mouth is opened as wide as possible painlessly or as the inter incisal distance plus the overbite. Clinical measurement of normal range of Maximum Mouth Opening (MMO) in children is an important diagnostic criterion for evaluation of stomatognathic system, especially for those with temporomandibular and neurogenic dysfunctions.

AIM

To determine the correlation of maximal mouth opening with age, sex, height, body weight and different facial types.

MATERIALS AND METHODS

The study was a cross-sectional study which was conducted on 434 children, who were randomly divided into three groups based on their age: Group I- children of age 6 to 8 years, Group II- children of age 8.1 to 10 years, Group III- children of age 10.1 to 12 years. For each child, the examiner took three readings of MMO in millimeters (mm) and the mean of the three readings was considered. Age, sex, standing height, body weight and facial type of each child were also recorded simultaneously. Pearson correlation was used to determine the relationship between the different parameters. p-value <0.05 was the bench mark for statistical significance in the analysis. Descriptive and inferential analysis was done for the data using SPSS version 20.0. (SPSS 20, inc.; Chicago).

RESULTS

The estimated average MMO measured for girls and boys in the age range of 6-8 years, with a total sample size of 139, was 41.14 ± 4.29 mm and 42.16 ± 3.98mm respectively in euryprosopic face type. In leptoproscopic face type, it was 42.12 ± 4.54mm and 43.76 ± 3.80 mm in girls and boys respectively. In mesoproscopic face type, MMO measured was 41.77 ± 4.09mm and 42.51 ± 3.95 mm in girls and boys respectively. The estimated average MMO measured for girls and boys in the age range of 8.1-10 years, with a total sample size of 143, was 44.42+4.69mm and 43.30 ± 4.11 mm in euryprosopic face type. In leptoproscopic face type, it was 43.02 ± 3.92mm and 46.29 ±3.09mm in girls and boys respectively. In mesoproscopic face type, MMO measured was 42.50 ±4.32 and 42.80 ± 5.16 mm in girls and boys respectively. The estimated average MMO measured for girls and boys in the age range of 10.1-12 years, with a total sample size of 152, was 44.63 ± 5.28 mm and 45.80 ± 5.18 mm respectively in euryprosopic face type. In leptoproscopic face type, it was 45.76 ± 4.98 mm and 46.28 ± 4.68 mm in girls and boys respectively. In mesoproscopic face type, MMO measured was 45.32 ± 5.80 mm and 46.03 ± 5.86 mm in girls and boys respectively.

CONCLUSION

There was a significant difference in MMO between males and females; with males having higher values in all age groups. MMO is seen to increase with age in a statistically significant manner. Significantly increased value of MMO was observed in leptoproscopic face type in comparison to euryproscopic and mesoproscopic face type for each age group.

The anterior component of occlusal force revisited: direct measurement and theoretical considerations

BACKGROUND

The anterior component of occlusal force (ACF), considered to result from the mesial inclination of teeth relative to the occlusal plane, has been estimated by indirectly measuring contact point tightness (CPT) through interproximal insertion of metal strips. ACF has been observed concurrently with a posterior component, whose theoretical origin is difficult to explain.

OBJECTIVES

Evaluate ACF by measuring CPT directly, and integrate current data to propose a theoretical basis for ACF.

MATERIALS AND METHODS

The sample comprised 14 females (age: 22.3±2.8) and 16 males (age: 20.8±2.5). Our device consisted of two force sensors: one for measuring maximum bite force (MBF) (overall thickness: 4mm), and one for measuring CPT directly (0.2mm thick), inserted between the lower first molar and second premolar. ACF was computed as the difference in CPT between the biting (at 75 per cent of MBF) and non-biting conditions.

RESULTS

Averages of MBF, CPT, and ACF were 666.67 [standard deviation (SD): 36.06], 6.74 (SD: 1.17), and 20.59 (SD: 4.60) N, respectively. ACF, CPT, and MBF were higher in males by approximately 28, 18 and 7 per cent, respectively. A positive correlation was observed between ACF and MBF (R (2): 0.64). CPT was also significantly correlated to MBF (R (2): 0.40). Biomechanical analysis indicates that previously offered explanations do not unriddle the concurrent increase of CPT at anterior and posterior contact points.

CONCLUSIONS

ACF was related to bite force by a logarithmic model. We speculate that CPT increases during biting through a combination of mesial tipping of teeth and mandibular bending.

Biomechanical potential of the temporal muscle in brachyfacial and dolichofacial subjects: a study on dry mandibles

OBJECTIVES

To measure the lengths of the force and resistance arms, in order to calculate the mechanical advantage and muscular work of the human temporalis muscle (TM) in brachyfacial (BR) and dolichofacial (DO) subjects.

SETTING AND SAMPLE POPULATION

Mandibles from 49 subjects of both genders (BR n = 9; DO n = 40) from the collection of the Laboratory of Human Anatomy at Universidade de Santa Cruz do Sul, Rio Grande do Sul, Brazil, were analyzed.

MATERIAL AND METHODS

The distance between the condylar process and the coronoid process (insertion site of the TM) represented the length of the force arm (LFA ) of the TM. The distance between the condylar process and the mental protuberance represented the length of the resistance arm (LRA ). Thus, the mechanical advantage of the TM was obtained using the following ratio: LFA /LRA , while the muscular work (LRA /LFA ) of the TM was obtained using the inverse of this ratio.

RESULTS

When compared with the DO, the parameters of the BR are significantly greater, as shown by the LFA (6.0%) and mechanical advantage (8.2%; p = 0.0078). By contrast, our results show that in the DO, the LRA was 2.4% longer and the muscular work was 10.4% greater (p = 0.0087).

CONCLUSION

The mechanical advantage of the TM in BR subjects is significantly greater than in DO subjects. Moreover, this greater mechanical advantage may explain, at least in part, the higher incidence of temporomandibular dysfunctions in BR subjects.

Clinical importance of median mandibular flexure in oral rehabilitation: a review

The mandible has a property to flex inwards around the mandibular symphysis with change in shape and decrease in mandibular arch width during opening and protrusion of the mandible. The mandibular deformation may range from a few micrometres to more than 1 mm. The movement occurs because of the contraction of lateral pterygoid muscles that pulls mandibular condyles medially and causes a sagittal movement of the posterior segments. This movement of mandible can have a profound influence on prognosis and treatment outcome for various restorative, endodontics, fixed, removable and implant-related prosthesis. The review unfolds the causes, importance and clinical implications of median mandibular flexure in oral rehabilitation. This review also highlights the appropriate preventive measures and techniques that should be adopted by clinicians to minimise the effect of flexural movement of the jaw during oral rehabilitation. This would not only help clinicians to achieve a good prosthesis with accurate fit and longevity but also maintain the health of the surrounding periodontal or periimplant gingival tissues and bone.