Maximum bite force following unilateral implant‐supported prosthetic treatment: within‐subject comparison to opposite dentate side

Bite force is a significant component of chewing and masticatory function. The literature lacks studies that compare bite force values of implant‐supported fixed bridges to natural dentition within same subjects. The objective of the study was to assess maximum occlusal bite force (MBF) among patients with an implant‐supported fixed prosthesis and compare it to their opposite dentate side and also to determine the effect of gender, age and Body Mass Index (BMI) on maximum occlusal bite force. Forty patients (20 males and 20 females, mean age = 42·7 ± 9·6 years) with an implant‐supported fixed prosthetic rehabilitation on one side and dentate on the other side were recruited into this study. Participants' MBF were measured bilaterally at the first molar region using a digital hydraulic occlusal force gauge (GM10). The measurements were repeated three times (with 45 s intervals between times) for each side, and the highest value of the bite force (MBF) was recorded for each side. The mean MBF was 577·9 N at the implant‐supported prosthesis side and 595·1 N at the dentate side. The average MBF was higher at the dentulous side (P < 0·05). Maximum occlusal bite force was higher in males and participants with higher weight and height. However, BMI was not significantly related to MBF values. Maximum occlusal bite force values at the dentate side were slightly (3%) but significantly higher than MBF at implant‐supported prosthesis side. Males, taller patients and patients with higher weights had higher MBF values. Body mass index was not significantly related to MBF values.     

Effect of implant‐supported prosthesis on the bite force and masticatory efficiency in subjects with shortened dental arches

The aim of the study was to assess changes in bite force and masticatory efficiency in shortened dental arch (SDA) subjects rehabilitated with implant‐supported restoration for 1st molar. Ten SDA subjects with bilaterally missing mandibular molars (experimental group) were recruited. In each subject, one tapered threaded implant was placed bilaterally in 1st mandibular molar region and restored. Masticatory efficiency was evaluated objectively by measuring the released dye from chewed raw carrots, with a ‘spectrophotometer’ at 530 nm preoperatively and at 3 months after restoration. Bite force was evaluated using ‘bite force measuring appliance’ preoperatively, at 6 weeks and at 3 months after restoration. Ten completely dentate‐matched subjects (in terms of age, sex, height and weight) acted as control. The results revealed that as compared with the control group, the experimental group showed significantly less (P < 0·05) mean maximum bite force at pre‐restoration and at 6 weeks after restoration. Although at 3 months the mean maximum bite force value was less than the control group but the mean difference was statistically insignificant. The mean difference of masticatory efficiency between control and experimental group was statistically significant (P < 0·05) before restoration, but was statistically insignificant at 3 months after restoration. Thus it was concluded that after the restoration of mandibular arch with implant‐supported prosthesis, both bite force and masticatory efficiency of all SDA subjects increased and were comparable to that of matched completely dentate subjects after 3 months.     

A preliminary study to find a possible association between occlusal wear and maximum bite force in humans

Abstract

Objective. The objective of the study was to investigate whether moderate-to-severe attrition is associated with maximum bite force in the first molar region. Methodology. Maximum bite force in the first molar region was measured for a total of 60 subjects having moderate-to-severe attrition of occlusal surface (experimental group) using a specially-designed piezoelectric sensor based bite force measuring device. An equal number of age, gender, height and weight matched controls (control group) were also subjected to bite force measurement for comparison. Results. The maximum bite force was found to be significantly lower (p < 0.05) in the experimental group [480.32 (153.40)] as compared to the controls [640.63 (148.90)]. While analyzing the possible etiology for occlusal wear mainly two reasons were elicited, i.e. history of parafunctional habits like use of known abrasive tooth powder (sub-group A) and Bruxism (sub-group B). However, there were many subjects in which no known definite etiological factors be attributed to occlusal wear (sub-group C). On analysing further with respect to the possibly correlated etiological factors with maximum bite force, no significant difference was found within the experimental sub-group. However, all three experimental sub-groups had significantly lower maximum bite force as compared to age, gender and BMI matched controls. Conclusion. A significantly lower maximum bite force was found to be associated with moderate-to-severe attrition as compared to subjects without attrition. However, no specific relation could be found between bite force and possible etiological factors like history of parafunctional habits, history of use of known abrasive tooth powder, etc.     

Assessment of masticatory function in patients with non‐sagittal occlusal discrepancies

Non‐sagittal occlusal discrepancies such as posterior cross‐bite and anterior openbite are common types of malocclusion, but studies on masticatory function related to those malocclusions have been scarce. The aim of this study was to quantify the masticatory performance in patients with non‐sagittal discrepancies compared to those with normal occlusion, using both objective and subjective measures. Maximum bite force and contact area using Dental Prescale^® system as a static objective assessment, Mixing Ability Index (MAI) as a dynamic objective evaluation and food intake ability (FIA) as a subjective assessment were analysed from 21 people in normal occlusion (Group N) and 64 patients with posterior cross‐bite (Group C), anterior openbite (Group O) or both (Group B). The differences of the maximum bite force, the contact area, the MAI and the FIA were compared, and their correlations were figured out. The non‐sagittal malocclusion groups showed lower values in the maximum bite force, the contact area, the MAI and the FIA compared to those in the normal group (P < 0·0001). Compared to Group N, Groups C, O and B showed 61·5%, 42·1% and 40·1% of the maximum bite force, and 84%, 84% and 76% of hard food FIA, respectively. However, there were no significant differences among Groups C, O and B. The MAI showed higher correlation with the FIA (r = 0·38, P < 0·01), than with the maximum bite force and the contact area (both r = 0·24, P < 0·5). These results revealed that masticatory function in patients with non‐sagittal discrepancies is significantly reduced both objectively and subjectively.     

Bite force measurements with hard and soft bite surfaces

Bite force has been measured by different methods and over a wide variety of designs. In several instruments, the fact that bite surface has been manufactured with stiff materials might interfere in obtaining reliable data, by a more prompt activation of inhibitory reflex mechanisms. The purpose of this study was to compare the maximum voluntary bite force measured by a digital occlusal force gauge (GM10 Nagano Keiki, Japan) between different opponent teeth, employing semi‐hard or soft bite surfaces. A sample of 34 young adults with complete natural dentition was studied. The original semi‐hard bite surface was exchanged by a soft one, made of leather and rubber. Maximum voluntary bite force recordings were made for each tooth group and for both bite surfaces. Statistical analyses (Student's t‐test) revealed significant differences, with higher scores while using the soft surface across sexes and tooth groups (P < 0·05). Differential activation of periodontal mechanoreceptors of a specific tooth group is mainly conditioned by the hardness of the bite surface; a soft surface induces greater activation of elevator musculature, while a hard one induces inhibition more promptly. Thus, soft bite surfaces are recommended for higher reliability in maximum voluntary bite force recordings.     

The Effect of Removable Partial Dentures on Alveolar Bone Resorption: A Retrospective Study with Cone‐Beam Computed Tomography

Purpose: The aim of this study was to compare vertical and horizontal mandibular alveolar bone resorption by measuring bone morphological variation in Kennedy Class II removable partial denture (RPD) wearers and non‐wearers using cone‐beam computed tomography (CBCT). Materials and Methods: In total, 124 sites in the CBCT scans of 62 (29 RPD non‐wearers, 33 RPD wearers) Kennedy Class II patients were analyzed retrospectively. Three‐dimensional representations of the mandible with superimposed cross‐sectional slices were developed with the CBCT scans to evaluate the mandibular alveolar height and width by measuring distances between the mandibular canal, mylohyoid ridge, alveolar crest, and lower border of the mandible in four regions (eight sites) of Kennedy Class II non‐wearers and wearers of RPDs. Results: Mandibular alveolar bone height and width were significantly lower in edentulous sites when compared with dentate sites in both Kennedy Class II non‐wearers and wearers of RPDs (p < 0.05). Additionally, mean vertical and horizontal mandibular bone resorption was significantly higher in RPD wearers than in non‐wearers (p < 0.05). Conclusions: Vertical and horizontal alveolar bone resorption was found to be higher in the RPD wearing patients when comparing the dentate and edentulous sites.     

Effect of Single and Contiguous Teeth Extractions on Alveolar Bone Remodeling: A Study in Dogs

Background: Tooth extraction is associated with dimensional changes in the alveolar ridge. The aim was to examine the effect of single versus contiguous teeth extractions on the alveolar ridge remodeling. Material and Methods: Five female beagle dogs were randomly divided into three groups on the basis of location (anterior or posterior) and number of teeth extracted – exctraction socket classification: group 1 (one dog): single‐tooth extraction; group 2 (two dogs): extraction of two teeth; and group 3 (two dogs): extraction of three teeth in four anterior sites and four posterior sites in both jaws. The dogs were sacrificed after 4 months. Sagittal sectioning of each extraction site was performed and evaluated using microcomputed tomography. Results: Buccolingual or palatal bone loss was observed 4 months after extraction in all three groups. The mean of the alveolar ridge width loss in group 1 (single‐tooth extraction) was significantly less than those in groups 2 and 3 (p < .001) (multiple teeth extraction). Three‐teeth extraction (group 3) had significantly more alveolar bone loss than two‐teeth extraction (group 2) (p < .001). The three‐teeth extraction group in the upper and lower showed more obvious resorption on the palatal/lingual side especially in the lower group posterior locations. Conclusion: Contiguous teeth extraction caused significantly more alveolar ridge bone loss as compared with when a single tooth is extracted.     

Effect of gender, facial dimensions, body mass index and type of functional occlusion on bite force

Objective

Some factors such as gender, age, craniofacial morphology, body structure, occlusal contact patterns may affect the maximum bite force. Thus, the purposes of this study were to determine the mean maximum bite force in individuals with normal occlusion, and to examine the effect of gender, facial dimensions, body mass index (BMI), type of functional occlusion (canine guidance and group function occlusion) and balancing side interferences on it.

Material and Methods

Thirty-four individuals aged 19-20 years-old were selected for this study. Maximum bite force was measured with strain-gauge transducers at first molar region. Facial dimensions were defined by standardized frontal photographs as follows: anterior total facial height (ATFH), bizygomathic facial width (BFW) and intergonial width (IGW). BMI was calculated using the equation weight/height². The type of functional occlusion and the balancing side interferences of the subjects were identified by clinical examination.

Results

Bite force was found to be significantly higher in men than women (p<0.05). While there was a negative correlation between the bite force and ATFH/BFW, ATFH/IGW ratios in men (p<0.05), women did not show any statistically significant correlation (p>0.05). BMI and bite force correlation was not statistically significant (p>0.05). The average bite force did not differ in subjects with canine guidance or group function occlusion and in the presence of balancing side interferences (p>0.05).

Conclusions

Data suggest that bite force is affected by gender. However, BMI, type of functional occlusion and the presence of balancing side interferences did not exert a meaningful influence on bite force. In addition, transverse facial dimensions showed correlation with bite force in only men.     

Standardized Rat Model Testing Effects of Inflammation and Grafting on Extraction Healing

Background: Loss of alveolar ridge width and height after tooth extraction is well documented, but models to evaluate ridge preservation are neither standardized nor cost‐effective. This rat model characterizes the pattern of bone turnover and inflammation after extraction and bone grafting with or without local simvastatin (SIM). Methods: Fifty retired‐breeder rats underwent extraction of the maxillary right first molar and standard surgical defect creation under inhalation/local anesthesia. The left side of each animal served as unmanipulated control. Untreated groups (n = 8 to 9 per group) were compared (analysis of variance, t test) at days 0, 7, 14, and 28 for alveolar ridge height and width and for markers of inflammation and bone turnover by microcomputed tomography, histology, and enzyme‐linked immunosorbent assay. Seventeen additional specimens had defects grafted with either bone mineralized matrix (BMM) or a BMM+SIM conjugate. Results: Extraction‐induced bone loss (BL) was noted on buccal, palatal, and interproximal height (P <0.05) and ridge width (P <0.01). Week 1 inflammation positively correlated with ridge height; thereafter, a more intense inflammatory reaction corresponded to reduction in alveolar bone height and density (r = 0.74; P <0.05; Spearman). BMM+SIM preserved the most interproximal bone height (P <0.01), increased ridge width and bone density (P <0.01), enhanced 7‐day prostaglandin E2 (P <0.01), and reduced 28‐day inflammation density (P <0.05). Conclusions: The standard defect used in the current study paralleled human postextraction alveolar BL. Defect grafting, especially BMM+SIM, reduced inflammation and preserved bone.     

Microcomputed Tomographic Analysis of the Alveolar Ridge Alteration around Extraction Sites with and without Immediate Implants Placement: In Vivo Study

Background: The aim was to assess the alveolar ridge alteration around extraction sites with and without immediate implants according to extraction socket classification (ESC) using microcomputed tomography (micro‐CT). Material and Methods: Ten beagle dogs (mean age and weight: 24 ± 0.83 months and 13.8 ± 0.49 kg, respectively) were randomly divided into three groups according to the ESC. In Group 1 (ESC‐I), bilateral first and third premolars were extracted and replaced with immediate implants. In Group 2 (ESC‐II), two adjacent premolars were extracted with one immediate implant placement in the mesial socket in the maxilla and in the distal socket in the mandible. In Group 3 (ESC‐III), three adjacent teeth were extracted and an immediate implant was placed in the central socket. Primary closure was achieved using resorbable sutures. Buccal sites with dehiscence defects were excluded. After 4 months, subjects were sacrificed and alveolar ridge widths were measured at 1 mm interval in axial and sagittal views, using micro‐CT in sites with and without immediate implants. Results: In sites without immediate implant placement, alveolar ridge width was significantly higher in Group 1(6.1 ± 1.35 mm) than Group 3 (4.14 ± 1.53 mm) (p < .05). In sites with immediate implant placement, the alveolar ridge width was higher among sites in Group 1 (6.4 ± 3.8 mm) than Group 2 (4.8 ± 0.46 mm) (p < .05) and Group 3 (5.02 ± 0.84 mm) (p < .05). Overall, between each corresponding group in both sites with and without immediate implant placement at 1 mm thickness, there was no significant difference in the alveolar ridge widths. Conclusion: With the exception of Group 1 (ESC‐I), immediate implant placement did not prevent or minimize bone remodeling in extraction sites according to ESC.     

单根牙牙槽骨吸收度与最大（牙合）力关系的研究

目的研究单根牙牙槽骨吸收程度与最大（牙合）力的关系.方法选择37例牙周病患者,710个单根牙,记录其前牙超覆（牙合）情况,拍摄牙片,测量每个受试牙的牙槽骨吸收程度和最大（牙合）力.结果最大牙合力值因个体间和牙位不同存在明显差异.当左右同名牙牙槽骨高度相近时,最大（牙合）力值相近.最大（牙合）力值与牙槽骨吸收程度有着明显的相关性,牙槽骨吸收程度增加,最大（牙合）力降低.牙周病易于导致前牙覆（牙合）深、超（牙合）大的（牙合）型.结论牙槽骨高度影响最大（牙合）力,牙周病将导致牙合的异常及咀嚼功能受到损害.     

Accelerated Bone Formation in Distracted Alveolar Bone After Injection of Recombinant Human Bone Morphogenetic Protein‐2

Background: This study evaluates the effect of recombinant human bone morphogenetic protein‐2 (rhBMP‐2) on the quality and quantity of regenerated bone when injected into distracted alveolar bone. Methods: Sixteen adult beagle dogs were assigned to either the control or rhBMP‐2 group. After distraction was completed, an rhBMP‐2 dose of 330 μg in 0.33 mL was injected slowly into the distracted alveolar crest of the mesial, middle, and distal parts of the alveolar bone in the experimental group. Histologic and microcomputed tomography analyses of regenerated bone were done after 2 and 6 weeks of consolidation. Results: After 6 weeks of consolidation, the vertical defect height in the middle of the regenerated bone was significantly lower in the rhBMP‐2 group (2.2 mm) than in the control group (3.4 mm) (P <0.05). Additionally, the width of the regenerated bone was significantly greater in the rhBMP‐2 group (4.3 mm) than in the control group (2.8 mm) (P <0.05). The bone density and volume of regenerated bone in the rhBMP‐2 group were greater than in the control group after 6 weeks of consolidation (P <0.001). Conclusion: Injection of rhBMP‐2 into regenerated bone after a distraction osteogenesis procedure significantly increased bone volume in the dentoalveolar distraction site and improved both the width and height of the alveolar ridge and increased the bone density.     

Correlation of mandibular bone quality with neurosensory disturbance after sagittal split ramus osteotomy

Our aim was to find out whether the quality of bone around the inferior alveolar nerve is correlated with neurosensory disturbance to the nerve after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Computed tomograms (CT) were taken of 35 patients with mandibular prognathism and 35 without. To assess the density of bone around the inferior alveolar nerve, the width of the buccal cortical bone in the mandibular second molar regions was measured on CT. The Hounsfield units (HU) in the same regions were also measured. The number of HU in the mandible around the second molar regions was significantly higher (p < 0.01) in those with neurosensory disturbance (p < 0.01). The quality of bone measured by HU is associated with an increased risk of neurosensory disturbance, but the width of buccal bone is not.     

Regenerative potential and healing dynamics of the periodontium: a critical‐size supra‐alveolar periodontal defect study

Objectives: The nature and characteristics of the newly formed periodontium obtained following regenerative procedures remain a matter of controversy. The objective of this study was to evaluate the regenerative potential of the periodontal attachment and healing dynamics as observed from the spatial distribution of newly formed cementum, periodontal ligament (PDL) and alveolar bone following optimal circumstances for wound healing/regeneration in a discriminating animal model. Material and Methods: Critical‐size, 6‐mm, supra‐alveolar, periodontal defects were surgically created in six young adult Beagle dogs. Space‐providing ePTFE devices with 300‐μm laser‐drilled pores were implanted to support wound stability and space provision in one jaw quadrant/animal. Treatments were alternated between left and right jaw quadrants in subsequent animals. The gingival flaps were advanced to submerge the defect sites for primary intention healing. Histometric analysis followed an 8‐week healing interval. Results: Healing was uneventful in all animals. The histometric analysis showed that cementum regeneration (2.99 ± 0.22 mm) was significantly greater than PDL (2.54 ± 0.18 mm, p=0.03) and bone regeneration (2.46 ± 0.26 mm, p=0.03). The wound area showed significant positive non‐linear effect on cementum (log β=1.25, p<0.001), PDL (log β=1.24, p<0.001) and new bone formation (log β=1.36, p<0.001). A high degree of concordance and significant linear relationship was observed between cementum, PDL and bone regeneration indicating that their formation virtually occurred in parallel. Conclusions: Cementum, PDL and alveolar bone virtually regenerate in parallel under optimal circumstances for periodontal wound healing/regeneration. Moreover, space provision positively influences the extent of periodontal regeneration.     

The influence of altered functional loading and posterior bite-blocks on the periodontal ligament space and alveolar bone thickness in rats

Objectives: Posterior bite-blocks are resin-based structures elevating the occlusion and creating intrusive force on the posterior teeth. Bite-blocks were applied to the molars of growing rats and a hard and soft diet was used to create altered functional masticatory forces. The aim of the present investigation was to study the effect of this appliance on the periodontal ligament space and alveolar bone thickness when combined with altered masticatory forces.

Material and methods: Fifty-two four-week-old rats were divided into two groups, hard and soft diet. Two weeks later, half of them received a bite-block appliance, creating four groups: control hard (CH), control soft (CS), bite-block hard (BH) and bite-block soft (BS). All were sacrificed at age of 10 weeks. Their heads were scanned by micro-CT and periodontal ligament space (PDL) width, cross-sectional alveolar socket surface and alveolar bone thickness were measured. Analysis of variance (ANOVA) was used to compare the groups.

Results: The PDL was 9.2% thinner in the CS group (p?p p?=?0.018) in the CS group, 10.7% in the BH group (p?p?Conclusions: Young rats wearing posterior bite-blocks have narrower PDL space and thinner alveolar bone compared to controls. When fed a soft diet, the alveolar bone is even thinner but the PDL showed no difference.     

咬合力增强对大鼠牙周组织白细胞介素-6表达影响的研究

目的：检测咬合力在正常及增强状态下,大鼠牙周细胞ＩＬ－６的动态表达,初探ＩＬ－６在牙周组织改建中作用的分子机别。方法：采用免疫组化的方法,观察牙周形态变化以及牙周组织中ＩＬ－６蛋白表达。结果：咬合力增强引起牙周膜增宽、牙槽骨新骨形成。牙周细胞中ＩＬ－６表达较正常咬合力时明显增强。结论：咬合力增强,促使牙周组织产生ＩＬ－６明显增多,诱发了破骨功能;同时,还激活了成骨功能。     

Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats

Liu Y‐F, Wu L‐A, Wang J, Wen L‐Y, Wang X‐J. Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats. J Periodont Res 2010; 45: 714–719. © 2010 John Wiley & Sons A/S Background and Objective: Nicotine reportedly is a risk factor for periodontitis, but accurate data regarding nicotine‐induced alveolar bone loss is lacking. The aim of this study was to quantitatively assess alveolar bone loss in ligature‐ and nicotine‐induced periodontitis in rats using micro‐computerized tomography (micro‐CT). Material and Methods: Thirty‐six adult male rats were treated by placing silk ligatures around the cervixes of the right second maxillary molar; the contralateral tooth was untreated. After ligation, the animals were randomly divided into three groups: group A received intraperitoneal injections of saline solution, group B received 0.83 mg of nicotine/kg/d, and group C received 1.67 mg of nicotine/kg/d. Six animals in each group were killed on days 14 and 28 after ligature placement, and then micro‐CT examinations were conducted. Results: In all groups, bone mineral density (BMD), bone volume fraction (BVF), trabecular number (Tb.N) and trabecular thickness (Tb.Th) values of the ligated sides were significantly lower than those of the unligated sides (p < 0.001), whereas alveolar bone height loss (ABHL) and trabecular separation (Tb.Sp) of the ligated sides were significantly higher than those of the unligated sides (p < 0.001). Compared with the control group, nicotine administration increased the ABHL value and decreased the BMD, BVF and Tb.Th values of both sides in a dose‐dependent manner (p < 0.05). Conclusion: Our results confirmed that ligature could cause significant loss in the trabecula of alveolar bone, and daily administration of nicotine resulted in further bone loss and microstructure deterioration.     

Posterior scissors‐bite: masticatory jaw movement and muscle activity

Scissors‐bite is a malocclusion characterised by buccal inclination or buccoversion of the maxillary posterior tooth and/or linguoclination or linguoversion of the mandibular posterior tooth. This type of malocclusion causes reduced contact of the occlusal surfaces and can cause excessive vertical overlapping of the posterior teeth. This case–control study is the first to evaluate both masticatory jaw movement and masseter and temporalis muscle activity in patients with unilateral posterior scissors‐bite. Jaw movement variables and surface electromyography data were recorded in 30 adult patients with unilateral posterior scissors‐bite malocclusion and 18 subjects with normal occlusion in a case–control study. The chewing pattern on the scissors‐bite side significantly differed from that of the non‐scissors‐bite side in the patients and of the right side in the normal subjects. These differences included a narrower chewing pattern (closing angle, P < 0·01; cycle width, P < 0·01), a longer closing duration (P < 0·05), a slower closing velocity (P < 0·01) and lower activities of both the temporalis (P < 0·05) and the masseter (P < 0·05) muscles on the working side. In 96% of the patients with unilateral posterior scissors‐bite, the preferred chewing side was the non‐scissors‐bite side (P = 0·005). These findings suggest that scissors‐bite malocclusion is associated with the masticatory chewing pattern and muscle activity, involving the choice of the preferred chewing side in patients with unilateral posterior scissors‐bite.     

Are maximum bite forces of subjects 7 to 17 years of age related to malocclusion?

Objective:To determine the effects of occlusion on maximum bite force of growing subjects.Materials and Methods:Incisor and first molar bite force of children and adolescents was evaluated. Four cohorts were measured annually for 3 years, starting at approximately 7, 9, 12, and 15 years of age, respectively. The initial sample included 182 females and 198 males; there were 130 subjects with normal occlusion, 111 with Class I malocclusion, and 139 with Class II malocclusion. Multilevel analyses were performed to model the growth changes and compare groups.Results:Maximum bite force increased significantly (P < .05) over time. Incisal forces peaked at 14.3 and 15.3 years of age for females and males, respectively. Maximum molar bite force peaked at 16 years for both males and females. Subjects with normal occlusion had significantly higher bite force than subjects with malocclusion. Maximum molar bite force exhibited a significant testing effect, with forces increasing 2.6 kg each year that the tests were repeated.Conclusions:Malocclusion has a detrimental effect on bite force. Changes in maximum bite force are also due to age, sex, and repeated testing.     

Simplified stress analysis on the temporomandibular joint in Class III patients with and without mandibular asymmetry using a rigid body spring model

Authors – Ueki K, Takeuchi N, Nakagawa K, Yamamoto E Objective – Aim of this study was to investigate the differences in stress on the temporomandibular joint (TMJ) between Class III patients with and without mandibular asymmetry using a rigid body spring model (RBSM). Design – Menton (Me), the centre point of occlusal force on the line that connected the bilateral buccal cusps of the second molars and the most lateral, superior and medial points of the condyle were plotted on frontal cephalograms, and stress on the condyles was calculated with the 2‐dimensional RBSM program of fortran . Setting and Sample Population – Eighty Japanese patients with diagnosed mandibular prognathism were divided into two groups, a symmetry group and asymmetry group on the basis of the Mx‐Md midline position. Outcome measure – The degree (force partition) of the resultant force, the direction (angulation) and displacement (X, Y) of each condyle were calculated. The horizontal displacement vector (u), the vertical displacement vector (v) and rotation angle (θ) of the mandibular body at Menton were also calculated. Results – There were significant differences between the deviated and non‐deviated sides of both groups regarding resultant force (symmetry group: p = 0.0372, asymmetry group: p = 0.0054), X (symmetry group: p < 0.0001, asymmetry group: p = 0.0001) and Y (symmetry group: p = 0.0354, asymmetry group: p = 0.0043). For angulation, there was a significant difference between the deviated and non‐deviated sides in the asymmetry group (p = 0.0095). Conclusion – The results of this study suggest that difference in stress angulation on the condyles could be associated with asymmetry in mandibular prognathism.