A 3D cone beam computed tomography (CBCT) investigation of mandibular condyle morphometry: Gender determination,disparities, asymmetry assessment and relationship with mandibular size

ObjectiveCBCT (cone beam computed tomography) analysis of condyle morphometry, to investigate the gender differences, symmetry and relationship with mandibular size.Materials and methodsThis is a retrospective study. 800 CBCT scan obtained for the measurement of condyle in anterior-posterior and medio-lateral aspect using OnDemand 3D software. Participants were Saudi nationals of age above 18 years. 395 Males and 405 Females with the mean age of 38.2 ± 10.5 years. Right and left anterior-posterior width and medio-lateral width of the condyle were measured. Condyles were not isolated on the CBCT for volume measurement.ResultsMean right and anterior-posterior condyle width was 9.02 mm and 8.74 mm in males whereas in females it was 9.01 mm 8.69 mm respectively. For males mean medio-lateral width of the condyle in right and left side was 17.40 mm and 16.95 mm. For females, mean medio-lateral width of the condyle in right and left side was 17.14 mm and 16.93 mm. The prediction rate of gender was 57.2% for males and 53.3% for females. Statistically significant differences (p < 0.05) were found in the anterior–posterior and medio-lateral width of right and left condyles among males and females. Left anterior-posterior and medio-lateral width of average vs small mandible shows statistically significant difference (p < 0.05).ConclusionCondyle morphometry is a weak predictor for gender. Irrespective of gender, right and left condyle are asymmetrical in relation to condyle morphometry of anterior-posterior and medio-lateral aspect. Left mandibular condyle morphometry is different in relation to the mandible size.     

Fluctuating asymmetry of the permanent mandibular molars in a Japanese population

The purpose of the present study is to investigate the pattern of fluctuating odontometric asymmetry of permanent mandibular first and second molars in a Japanese population. Dental plaster casts of 112 (57 males and 55 females) Japanese undergraduate dental students were used. The mesiodistal and buccolingual diameters of the whole crown and trigonid and talonid crown components were taken on the left and right sides of the mandibular permanent first and second molars. Crown areas were also calculated. The fluctuating asymmetry (FA) value was obtained by dividing the absolute side difference by the absolute mean size of the left and right teeth: FA = abs (R?L)/((R + L)/2). Fluctuating asymmetry between mandibular first and second molars was significantly different with the mandibular second molar showing higher asymmetry in both males and females. Meanwhile, fluctuating asymmetry between males and females in the first and second molars was not significantly different in all measured dimensions. With regard to trigonid and talonid components, fluctuating asymmetry of the distal talonid area was significantly larger than the mesial trigonid area in the mandibular permanent first molar of males (P < 0.01), and asymmetry of buccolingual diameter of the talonid was also larger than that of the trigonid in the mandibular permanent second molar of males (P < 0.05). In conclusion, these findings suggest that the crown dimensions of later developing teeth in the mandibular molar tooth class and crown component in the same molar tooth show more asymmetry and, therefore, are more affected by external factors.     

骨性Ⅲ类偏颌患者髁突与(牙合)平面特征的CBCT研究

目的 利用锥形束CT(CBCT)测量分析骨性Ⅲ类偏颌患者髁突及(牙合)平面特征。方法 选取符合纳入标准的骨性Ⅲ类成年患者40例,所有个体按照颏下点偏离正中矢状面距离进行分组,分别测量各组左右两侧(牙合)平面角、髁突位置及形态,并对数据进行统计学分析。结果 骨性Ⅲ类偏颌患者的偏侧与对侧相比,(牙合)平面角、关节前间隙、关节上间隙、关节外间隙及髁突内外径差异有统计学意义(P<0.05),偏侧关节后位所占比例较大,下颌骨偏移量与偏侧髁突前间隙及对侧(牙合)平面角均呈正相关(P<0.01)。骨性Ⅲ类非偏颌患者的左右两侧(牙合)平面角、髁突位置及形态指标之间差异均无统计学意义(P>0.05),关节以前位、中位为主。结论 骨性Ⅲ类偏颌患者左右两侧(牙合)平面角、髁突位置及形态不对称,偏侧(牙合)平面角及髁突内外径较小,髁突向后下内方移位,且偏颌程度与(牙合)平面角及髁突位置之间存在相关性。     

The angle of the articular eminence in modern dentate African-Americans and European-Americans

The purpose of this study was to determine if there were differences in the angle of eminentia of two 20th century populations based on race, age, gender, and number of teeth and whether there was asymmetry of the angles of eminentia. The sample included dry skulls from the Hamann-Todd Osteological collection as follows: 80 African-Americans (AA, 53 males and 27 females) and 62 European-Americans (EA, 49 males and 13 females), ranging in age from 16-77 years. The lateral, central, and medial aspects of the right and left slopes of the articular eminence were measured in a parasagittal plane. Independent t-tests, paired t-tests, and Pearson correlation coefficients were computed. For the AA population, the right central, lateral, and medial angles of eminentia were steeper than the corresponding left angles (paired t-test, p<0.05); for the AE males only the right lateral and medial angles were significantly steeper than the corresponding left angles (paired t-test, p<0.05). There were no significant relationships between age or number of teeth and the angle of eminentia measurements, nor were there differences in angle of eminentia by gender. There were two differences by race: the EA males had steeper left central and left medial angles than the AA males (independent t-test, p<0.05). The central angle of eminentia was consistently steeper than the medial angle (paired t-test, p<0.01), and the lateral was generally steeper than the medial.     

Asymmetry of mandibular dimensions in European skulls.

Eighteen mandibular dimensions (mm) in sex-determined, 10th-12th-century European skulls from burial sites in South-Eastern Hungary were examined to discover whether differences exist between the right and left sides. There was a statistically significant difference in only one dimension, the smallest sagittal diameter of the mandibular neck, in both males and females. The frequencies with which the various 18 dimensions were identical between right and left sides ranged from 39.9% to 82.0% in males, and from 45.9% to 83.2% in females. The examined individual dimensions appeared to be smaller on the right side in 7.0% to 33.7% (mean 19.1%) of the male cases, and in 7.1% to 29.9% (mean 17.9%) of the females, while the right side was larger in 7.7% to 50.9% (mean 22.3%) of the males and in 7.9% to 54.3% (mean 22.5%) of the females. In conclusion, asymmetry of the left and right sides was found between the measured individual mandibular dimensions on average in 41.4% of the males and 40.4% of the females.     

Considerations in correction of mandibular protrusion by intra-oral vertical ramus osteotomy

This case report presents a case that underwent orthognathic treatment with intra-oral vertical ramus osteotomy (IVRO). The patient was a 19-year-old female with mandibular protrusion and severe maxillary anterior crowding. The overbite was +0.5 mm and the overjet −1.5 mm. She had orofacial pain and tenderness of the temporomandibular joints (TMJ) and surrounding muscles. The pre-surgical orthodontic treatment included the extraction of the maxillary right lateral incisor, maxillary right second premolar, maxillary left canine, mandibular left second molar and mandibular right second premolar. After 18 months of pre-surgical orthodontic treatment, the left and right sides of the mandible were set back 8 and 6 mm, respectively, via IVRO to improve mandibular protrusion. The total treatment period was 26 months. The patient showed the backward reaction of the mandible, which occurred after release of the maxillo-mandibular fixation. The usage of the Class II elastics during the post-surgical phase to maintain the overjet made the inclination of the maxillary incisors more lingual.     

Craniofacial growth after a period of unilateral masticatory function in young rabbits

Changes in craniofacial growth after a period of unilateral masticatory function were studied in rabbits. 10-day-old animals were divided into 3 groups. In Group I, mandibular and maxillary molars were ground down 2 X a week on the right side under general anesthesis until age 50 days, and were thereafter left to grow without grinding. In Group II, the right-dide molars were ground left dide. The animals were thereafter left to grow. Group III consisted of unoperated control animals. All of the animals were fed whole pellets and water ad libitum, and were sacrificed at age 100 days. There were measurable differences in growth after periods of unilateral masticatory function. The mandibular ramus was higher, the condylar processus was larger sagittally, and angles between the anterior or posterior bordrs of the condylar process and inferior border of mandible were smaller in the treated than in the control animals, and there were differences between right and left dides of the same animal in themazilla and mandible. The inclination of the articular surface of the glenoid fossa was steeper anteriorly on both sides in the treated than in the controls. It was concluded that growth after a period of unilateral masticatory function in young rabbits does not rectify all of the asymmetric changes in the maxilla, mandible and glenoid fossa resulting from the asymmetric function.     

An evaluation of asymmetry in TMJ radiographs.

The asymmetry of the mandibular fossae and condyles were measured to determine if there was a significant difference when comparing one side with the other. After all measurements were taken the test groups were separated into 70 acute TMJ patients and 70 control patients from general practice. It was found that the average differences between the right and left fossae of the TMJ and control groups were 0.17 mm and 0.16 mm respectively. Similarly the average difference between the right and left mandibular condyles of the two groups was approximately 0.2 mm. The differences in symmetry, obtained by comparing one side with the other, were clinically insignificant.There does not seem to be any reasonable possibility that the high incidence of TMJ dysfunctionpain syndrome reported in association with condylar displacement^{8–11, 14–16} is a result of fossae asymmetry or condylar asymmetry between the right and left sides. The controversy may be partially resolved in that only the superior portion of the fossa and a proportionally smaller part of the condyle are used to determine condylar position in the fossa. Marked asymmetry in the extreme anterior and posterior portions of the two mandibular condyles would not necessarily produce a significant difference in shape in that small part of the superior portion used to determine condylar position in the fossae.Based on this and previous research, the conclusion can be drawn that condylar displacement in the fossacannot be attributed to distortion in the radiographs, changes in head position, a lack of accuracy, or asymmetry of the mandibular condyles and fossa relative to the cranium or from one side to the other.     

Three-dimensional evaluation of craniofacial asymmetry: an analysis using computed tomography

3D image technology provides a very effective tool for evaluating, characterising, and drawing up the surgical treatment plan for potential orthognathic surgery patients. Patients with dysmorphic syndromes or incorrect jaw positions frequently show facial asymmetry. The objective of this cross-sectional survey is to evaluate facial asymmetry by means of three-dimensional computed tomography (CT) reconstructions. Twenty one consecutive patients were diagnosed using a CT scan. 3D reconstructions of the patients' skulls were made and then measurements taken of different craniometric landmarks and of the various structures presenting asymmetry. The gonion emerged as the most asymmetrical point in all subjects, and the anterior nasal spine showed least deviation. The t test produced statistically significant differences (p < 0.05) between symmetric and asymmetric patients at all landmarks. The lateral inclination of the mandibular ramus was shown to present the greatest asymmetrical deviation, followed by the frontal inclination of the mandibular ramus. The angulation of the mandibular ramus, on both frontal and lateral planes, determines apparent facial asymmetry, as well as conditioning the surgical treatment plan for patients with craniofacial asymmetry.     

Tooth axis and skeletal structures in mandibular molar vertical sections in jaw deformity with facial asymmetry using MPR images

The objective of the present study was to investigate frontal morphological asymmetry in the mandibular molar region in terms of tooth axis and skeletal structures using vertical MPR sections in jaw deformity accompanied by facial asymmetry. Subjects consisted of 15 patients with jaw deformity accompanied by facial asymmetry aged 17.4 years to 37.8 years. There were four men and eleven women. Based on X-ray computed tomography (CT) scans, DICOM viewer software was used to prepare multiplanar reconstruction (MPR) sections. The mandible was then positioned on a reference plane based on the menton and left and right gonions, and a vertical MPR section passing through the mesial root of the first mandibular molar was prepared. The following measurements were made on both the shifted and non-shifted sides: maximum buccolingual width of the mandibular body; height of the mandibular body; inclination angle of the mandibular body; degree of buccal protrusion of the mandibular body; and inclination angle of the buccolingual tooth axis of the first molar. Furthermore, degree of median deviation in the menton was measured using frontal cephalograms. Differences in morphological parameters between the shifted and non-shifted sides were assessed. Furthermore, the relationship between median deviation and asymmetry were statistically analyzed. There was no significant asymmetry in the maximum buccolingual width of the mandibular body, the height of the mandibular body or the degree of buccal protrusion of the mandibular body. However, when compared to the shifted side, the inclination angle of the buccolingual tooth axis of the first molar for the non-shifted side was significantly greater. There was a relatively strong correlation between median deviation and inclination angle of the mandibular body. The above findings clarified that, in orthognathic surgery for jaw deformity accompanied by facial asymmetry, actively improving asymmetry in the buccolingual inclination of the tooth axis of the molar region during presurgical orthodontic treatment is important in achieving favorable post-treatment occlusal stability and facial symmetry.     

青年人群正常颞下颌关节窝顶厚度CBCT测量分析

目的 获得青年人群正常颞下颌关节窝顶厚度锥形束计算机体层摄影术(CBCT)测量值,为颞下颌关节强直导航手术进行关节窝成形提供理论支持。方法 对132名青年志愿者264侧正常颞下颌关节行CBCT大视野扫描,利用图像处理软件进行三维重建后,在冠状视图和矢状视图中分别寻找并测量双侧颞下颌关节窝顶最薄处的骨质厚度,根据性别、侧别、年龄等分组进行统计学分析。结果 冠状视图中,总人群的测量值为0.940(0.748,1.311)mm,男性的测量值为1.040(0.731,1.675)mm,女性的测量值为0.883(0.753,1.199)mm;矢状视图中,总人群的测量值为0.903(0.720,1.331)mm,男性的测量值为1.073(0.755,1.585)mm,女性的测量值为0.865(0.706,1.090)mm;每个个体获得四组关节窝顶厚度测量值;四组测量值在男性和女性分组之间对比,右侧冠状视图和矢状视图中,男性关节窝顶厚度大于女性,差异有统计学意义(P<0.05),而左侧男性和女性关节窝顶厚度差异无统计学意义(P>0.05);所有个体左右双侧测量值对比,冠状视图中左侧关节窝...     

Buccolingual inclination of first molars in untreated adults: A CBCT study

Objective:To evaluate the buccolingual inclinations of maxillary and mandibular first molars in untreated adults.Materials and Methods:Fifty-nine subjects (14 males and 45 females; mean age, 41.2 years) with no missing teeth, no crossbite, and minimal crowding were included. For each subject, a CBCT was taken. The long axis of each first molar was determined, and the inclination of each molar was measured using the long axis and the floor.Results:One hundred seventeen out of 118 mandibular first molars measured had a lingual inclination, with a mean of 12.59° ± 5.47°. For the maxillary first molars, 107 out of 118 had a buccal inclination, with a mean of 4.85° ± 4.22°.Conclusions:There is a curvature to the inclinations of first molars in untreated adults, where the maxillary molars have a slight buccal inclination and mandibular molars have a slight lingual inclination.     

Morphological differences in the temporomandibular joints in asymmetrical prognathism patients

OBJECTIVE: To investigate the morphology of the temporomandibular joints (TMJ) in skeletal asymmetry with prognathism. DESIGN: Three-group observational clinical study. SETTING AND SAMPLE POPULATION: University setting. Thirty-five patients undergoing orthognathic surgery without signs and symptoms of TMJ disorder were assigned to three groups (right deviation, n = 11; left deviation, n = 14; and non-deviation; n = 10) based on anteroposterior cephalometric analysis. OUTCOME MEASURE: Positional and morphological differences of the TMJs were evaluated using a total of 70 bilateral sagittal TMJ magnetic resonance images. RESULTS: In both the right and left deviation groups, the TMJ on the deviated side showed a significantly steeper eminence than that on the non-deviated side (p < 0.05). The anterior joint space was narrower on the deviated side than on the non-deviated side whereas the posterior joint space did not differ markedly, indicating an anterior position of the condyle in the glenoid fossa of the TMJ on the deviated side. Disk displacement comparisons revealed no significant differences between left and right sides in the symmetry or asymmetry group. CONCLUSION: Asymmetrical prognathism patients exhibit significant morphological differences between the right and left TMJs concerning the slope of the articular eminence, which correspond to facial asymmetry.     

Alveolar bone level is not associated with vitamin D receptor gene polymorphism and bone density in mandible

The objective of this study was to determine, using digital panoramic radiographs, whether the bone level at the alveolar crest is related to the mandibular bone density and/or to vitamin D receptor (VDR) gene polymorphisms. We analyzed 319 digital panoramic radiographs from the same number of patients. Alveolar bone level was expressed as percentage of root length. The mandibular cortical width index was calculated as a measure of mandibular bone density, and, in 72 randomly selected cases, the haplotype of the VDR gene (BsmL) was determined by polymerase chain reaction. Alveolar bone level was not related to the mandibular cortical width index (p = 0.568) or VDR gene expression (p = 0.575). Bone loss was greater in smokers than in non-smokers (p = 0.036), and the mandibular cortical width index was higher in males (p = 0.04), the older age group (p = 0.032), and in those with more teeth (p = 0.01). Multivariate analysis confirmed the association between these variables and alveolar bone loss. Alveolar bone loss showed no significant relationship with the mandibular bone density evaluated on digital panoramic radiographs or with VDR genotype (BsmL) in Caucasian females and males aged under 47 years.     

Radiographic examination of the mandibular (glenoid) fossa in ancient and modern man

OBJECTIVE: To compare the morphology of the mandibular (glenoid) fossa between ancient and modern Japanese. METHODS: There were 221 specimens from the ancient period and 206 specimens from the modern period. Radiographs of the mandibular fossa were obtained using a modified Schuller technique and were studied. The length, depth, and area of the mandibular fossa and angulation of the frontal slope of the mandibular fossa on the radiographs were automatically computed. In addition, morphological changes of the mandibular fossa in the ancient or modern periods on radiographs were evaluated in order to assess tendency of temporomandibular joint disorder (TMD). RESULT: The ratio of mandibular fossa having morphological alternation in the modern period was greater than that in the Yayoi. Differences in the length and area between the right and left sides became progressively larger from the Yayoi to modern periods. The angulation of the anterior slope of the mandibular fossa in the modern period was smaller than that in other periods. CONCLUSION: The morphology of the mandibular fossa was shown to have changed and asymmetry has increased from the Yayoi to modern periods. It can be speculated that this change in morphology of the mandibular fossa in the modern period is the result of an increase of TMD.     

A computerized photographic assessment of the relationship between skeletal discrepancy and mandibular outline asymmetry

The aim of this study was to investigate the relationship between mandibular outline asymmetry and skeletal discrepancy in a sample of orthodontic patients (33 females, 33 males) aged from 8 to 19 years. Skeletal discrepancy was assessed in both the anteroposterior and vertical planes, using standard cephalometric analyses. All were photographed under standardized conditions and the photographs were then digitized for analysis using a computerized system to assess differences in four variables (area, perimeter, compactness and moment-ratio) between the right and left sides of the mandibular outline. The results showed good repeatability of the photographic, cephalometric and digitization methods. A statistically significant relationship was found between mandibular outline asymmetry and both anteroposterior and vertical skeletal discrepancy in this sample, when compared with patients with an average skeletal pattern. There appeared to be a statistically significant relationship between a reduced ANB angle (< 3 degrees) and mandibular outline asymmetry (P = 0.051), as well as between an increase in lower face height and mandibular asymmetry (P = 0.023).     

Effects of anterior cruciate ligament (ACL) injury on muscle activity of head, neck and trunk muscles: a cross-sectional evaluation

This study evaluated the that effects a pathology of the knee, due to an anterior cruciate ligament (ACL) injury, has on muscular activity of neck, head, and trunk muscles. Twenty-five (25) subjects (mean age 28+/-9 years) with ACL injury of the left knee were compared with a control no-pathology group. Surface electromyography (sEMG) at mandibular rest position and maximal voluntary clenching (MVC) wasused to evaluate muscular activity of the areas: masseter, anterior temporalis, posterior cervicals, sternocleidomastoid (SCM), and upper and lower trapezius. The sEMG activity of each muscle, as well as the asymmetry index between the right and the left sides, were compared between the two groups. Subjects in the study group showed a significant increase in the asymmetry index of the sEMG activity of the anterior temporalis at mandibular rest position (p<0.05). At rest, the areas of anterior temporalis and masseter in the control group showed a significantly lower sEMG activity compared with subjects in the study group, both in the right and the left sides (p<0.05). The same was found for the sEMG activity of the areas of SCM and lower trapezius. At MVC, the right areas of anterior temporalis and masseter in the study subjects showed a significantly lower sEMG activity compared with the control group. The same was observed for the lower trapezius area, both in the right and the left sides. In general, ACL injury appears to provide a change in the sEMG activity of head, neck and trunk muscles.     

Factors associated with mandibular third molar eruption and impaction

A retrospective study, using panoramic radiographs, was conducted on 152 Taiwanese (72 males and 80 females) to investigate mandibular third molar eruption and impaction. The following measurements were made: inclinations and mesiodistal crown widths of the mandibular molars, vertical and horizontal spaces between the distal surface of the second molar and the anterior surface of the ramus, lengths and widths of the mandibular ramus and body, the ramus inclination, the mandibular plane angle, and the mandibular gonial angle. Differences between non-impaction and impaction groups were studied, and the variables were analyzed with multivariate discriminatory analysis. Significant differences between the two groups were found; variables describing spaces between the anterior of the ramus and the distal of the mandibular second molar and tooth size appeared to be the primary contributors to the differences observed.     

Effect of unilateral masticatory function on craniofacial growth in the rabbit

In this study the main purpose was to investigate the effect of altered masticatory function on the shape and inclination of the articular surface of the glenoid fossa, and on the growth of the mandible in the rabbit. The maxillary and mandibular molars of 14, 10-d-old rabbits were ground down to the gingiva on the right side twice a week; 9 were controls. At age SO d all rabbits were killed, soft tissue of the heads was removed, and the measurements were made. The inclination of the articular surface of the glenoid fossa was shallower on both sides in the experimental group than in the controls; the difference was greater on the right side. There were dimensional and angular differences between right and left sides of the mandible and maxilla in the experimental animals. In conclusion, unilateral masticatory function was found to cause an asymmetric craniofacial growth. Furthermore, function has an effect on the shape of the glenoid fossa, especially on the balancing side, in conjunction with asymmetric function.     

The effect of mandibular protrusive (activator) appliances on articular eminence morphology

In studying the response of the glenoid fossa to mandibular protrusive appliances, apart from the condyle, much attention has been focused on what happens to the posterior wall of the fossa (post-glenoid process). Remarkably, the articular eminence has been overlooked, although it is the most adaptive area of the temporomandibular joint. The purpose of this study was to explore the type of response of the articular eminence morphology to the use of mandibular propulsive appliances (activators). The study material consisted of individually corrected pre- and posttreatment lateral tomograms of 35 patients (18 boys and 17 girls) who had been diagnosed as suitable for treatment with a mandibular protrusive appliance (activator). The tomograms were scanned and digitized on screen, and points located on each tomogram and linear measurements were used to evaluate any change in glenoid fossa morphology. Paired t-tests were applied separately for the left and right sides to compare pre- and posttreatment measurements. Paired t-tests were also applied to test any difference between the left and right sides. The results of this study show that there is no statistically significant change in articular eminence morphology (height and inclination) as a result of using mandibular protrusive appliances.