Jaw Relationship Research Articles

Can orthodontic relapse be blamed on the temporomandibular joint?

There are many temporomandibular joint (TMJ) conditions that can cause orthodontic treatment instability and relapse. These conditions are often associated with dentofacial deformities, malocclusion, TMJ pain, headaches, myofascial pain, TMJ and jaw functional impairment, ear symptoms, etc., Many of these TMJ conditions can cause progressive and continuous changes in the occlusion and jaw relationships. Patients with these conditions may benefit from corrective orthodontic and surgical intervention. The difficulty for many clinicians may lie in identifying the presence of a TMJ condition, diagnosing the specific TMJ pathology, and selecting the proper treatment for that condition. This paper will discuss the most common TMJ pathologies that can adversely affect orthodontic stability and outcomes as well as present the treatment considerations to correct the specific TMJ conditions and associated jaw deformities to provide stable and predictable treatment results.

Evaluation of the accuracy of a common regional registration method for three-dimensional reconstruction of edentulous jaw relation by a 7-axis three-dimensional measuring system

This study was to design a method to quantitatively evaluate three-dimensional (3D) reconstruction accuracy of spatial relationship of dental models based on a 7-axis contact 3D measuring system, and to evaluate the accuracy of a common regional registration method for edentulous jaw relation reconstruction. 3D surface data of edentulous dental casts with 10 positioning cylinders and wax occlusion rims of five patients were obtained using a dental scanner. The jaw relation was reconstructed using the common regional registration in the Geomagic software. Measurements were obtained for line length, vertical distance and horizontal distance between centric points from two sources with upper jaw model base plane as a reference plane. The statistical description of measurement data was done. x ± s of line length, vertical distance and horizontal distance between the center points of each data set were 0.107 ± 0.354, 0.076 ± 0.576 and 0.108 ± 0.530 mm, respectively. Data was analyzed using the paired samples t-test and one-way analysis of variance. Paired t-test results of each patient and one-way analysis of variance for the five patients showed no significant differences (P>0.05). Using the Faro Edge system and standardized positioning cylinders, quantitative evaluation of the 3D reconstruction accuracy of edentulous jaw relation was workable. And results of common regional registration method met clinical requirements.

Full mouth implant rehabilitation with double scanning of provisional restoration

It is important to produce a provisional restoration reflecting the patient's jaw relation, occlusal plane, lip support, shape of teeth, and occlusion type for fully edentulous patients before making a definite prosthesis. The patient introduced in this study showed bad prognosis of remained tooth after severe periodontal diseases. Therefore, remaining teeth were extracted and replaced with dental implants. Provisional restorations were fabricated and the the patient's vertical and horizontal jaw relationship, occlusal plane, amount of overjet and overbite, size of teeth, and length of anterior tooth were recorded. Provisional restorations were scanned and CAD/CAM techniques were used to fabricate a monolithic zirconia bridge, which contour is identical with the provisional restorations. The patient was satisfied with the treatment results on functional, esthetic aspects and the prosthesis retained stable during the four-month clinical observation period. (J Korean Acad Prosthodont 2014;52:252-7)

A new technique to determine vertical dimension of occlusion from anthropometric measurement of interpupillary distance.

Background: A number of techniques are being practiced for the evaluation of VDO, but none of them is scientifically more accurate than other. Each method advocated has its own limitations. Objectives: The purpose of this study was to find correlation between vertical dimension of occlusion (VDO) and interpupillary distance (IPD). Material and Methods: A cross-sectional study was conducted on 400 dentate subjects comprising of 200 males and 200 females. Anthropometric measurement of VDO was recorded clinically using modified digital vernier caliper. Also, a standardized digital photograph of face was generated from the frontal aspect using a digital camera for the measurement of IPD in millimeters. Correlation between VDO and IPD was studied using Spearman’s coefficient. For the execution of regression command and preparation of prediction equations to estimate VDO, Statistical Package for Social Sciences (SPSS) Software Version 11.5 was used. Results: VDO and IPD was more in males compared to females. VDO was significantly and positively correlated with IPD only in males whereas females showed a weak correlation. Hence, regression equation was derived only for males. VDO estimation using regression equation for IPD had a standard error of ± 3.94 in males. Conclusions: Since the variations between VDO and IPD are within the range of 2-4 mm, VDO prediction through this method is reliable and reproducible for male patients. Also, the method is simple, economic, and non invasive; hence it could be recommended for everyday practice to determine vertical dimension of occlusion in case of male patients. Key words:Anthropometry, interpupillary distance, jaw relation, vertical dimension of occlusion.

Evaluation of relationship between cranial base angle and maxillofacial morphology in Indian population: A cephalometric study.

Objective:To investigate the role played by the cranial base flexure in influencing the sagittal and vertical position of the jaws in Indian population.Materials and Methods:Lateral cephalograms of 108 subjects were divided into three categories (Group A: NSAr > 125°, Group B: NSAr-120°-125°, Group C: NSAr < 120°) according to value of NSAr. Measurement of eight angular (SNA, SNB, NPg-FH, ANB, NAPg, SN-GoGn, Y-Axis, ArGo-SN) and seven linear (N-S, S-Ar, Ar-N, Ar–Pt A, Ar–Gn, Wits appraisal, N- Pt A) variables were taken.Results:Pearson correlation coefficient test was used to individually correlate angular and linear variables with NSAr for the whole sample as well as in individual group. Unpaired t-test was used to analyze the difference in the means of all the variables between the three groups. Significance was determined only when the confidence level was P < 0.05. Several parameters (SNB, NAPg, ANB, Y-Axis, GoGn-SN) showed significant positive correlation while others showed negative correlation (SNA, NPg-FH, N-S) with NSAr.Conclusions:This study show cranial base angle has a determinant role in influencing the mandibular position and it also affects both the mandibular plane angle and y-axis. Flattening of the cranial base angle caused a clockwise rotation of the mandible. The jaw relation tends to change from class III to class II, with progressive flattening of the cranial base and vice-versa.

Cephalometric analysis of the middle part of the face in patients with mandibular prognathism

The middle part of the face, that is the maxilla, has always been mentioned as a possible etiologic factor of skeletal Class III. However, the importance of the relationship of maxillary retroposition towards the cranial base is still unclear, although it has been examined many times. The aim of this study was to conduct cephalometric analysis of the morphology of maxilla, including the whole middle part of the face in patients with divergent and convergent facial types of mandibular prognathism, as well as to determine differences betweeen them. Lateral cephalometric teleradiograph images of 90 patients were analyzed at the Dental Clinic of the Military Medical Academy, Belgrade, Serbia. All the patients were male, aged 18-35 years, not previously treated orthodontically. On the basis of dentalskeletal relations of jaws and teeth, the patients were divided into three groups: the group P1 (patients with divergent facial type of mandibular prognathism), P2 (patients with convergent facial type of mandibular pragmathism) and the group E (control group or eugnathic patients). A total of 9 cephalometric parameters related to the middle face were measured and analyzed: the length of the hard palate--SnaSnp, the length of the maxillary corpus--AptmPP, the length of the soft palate, the angle between the hard and soft palate--SnaSnpUt, the angle of inclination of the maxillary alveolar process, the angle of inclination of the upper front teeth, the effective maxillary length--CoA, the posterior maxillary alveolar hyperplasia--U6PP and the angle of maxillary prognathism. The obtained results showed that the CoA, AptmPP and SnaSnp were significally shorter in patients with divergent facial type of mandibular prognathism compared to patients with convergent facial type of the mandibular prognathism and also in both experimental groups of patients compared to the control group. SnaSnp was significantly shorter in patients with divergent facial type of mandibular prognathism compared to the control group, whereas SnaSnp was significantly smaller in patients with convergent facial type of mandibular prognathism compared to the control group. Additionally, there was a pronounced incisor dentoalveolar compensation of skeletal discrepancy in both groups of patients with mandibular prognathism manifested in the form of a significant upper front teeth protrusion, but without significant differences among the groups, while the maxillary retrognathism was present in most patients of both experimental groups. A pronounced UGPP was found only in the patients with divergent type of mandibular prognathism. The maxilla is certainly one of the key factors which contributes to making the diagnosis, but primarily to making a plan for mandibular prognathism treatment Accurate assessment of the manifestation of abnormality, localization of skeletal problems and understanding of the biological potential are key factors of the stability of/the results of surgical-orthodontic treatment of this abnormality.

Why WITS? Why not a way beyond?

Introduction:WITS appraisal is a common parameter in cephalometrics to assess maxillo-mandibular skeletal relationship as an adjunct to angle ANB. The high variability of the WITS appraisal is attributable to difficulties or inaccuracies in identifying the occlusal plane or variations due to tooth eruption, dental development or treatment changes by vertical movement of incisors, molars, or both.Aim:An extracranial reference line common to both denture bases, instead of the occlusal plane is proposed to assess antero-posterior jaw relationships.Materials and Methods:A true vertical obtained by plumb line was recorded, while taking the cephalogram for 40 subjects. A line drawn perpendicular to this true vertical gave a stable and reproducible extracranial true horizontal (HOR) reference line. The linear distance between perpendiculars from points A and B was measured as an adjunct to angle ANB.Result:The Pearson's product moment correlation coefficient calculated for the entire sample indicated higher correlation coefficient (r = 0.8712) for the linear measurements on HOR (AH-BH) with respect to the angle ANB when compared with the WITS readings (AO-BO) (r = 0.549).Conclusion:The horizontal appraisal method proposed eliminates the demerits of the occlusal plane and has the merits of simplicity and accuracy in comparison to WITS appraisal.

Cervical vertebral anomalies in skeletal malocclusions: a cross-sectional study on orthodontic patients at the Aga Khan University Hospital, Pakistan.

Morphological deviations of the cervical vertebral column have been described in relation to craniofacial aberrations and syndromes. Furthermore, it has recently been shown that abnormal morphology of upper cervical vertebrae is associated with malformation of the jaws and occlusion. Accordingly, it is relevant to focus on similar associations in patients with skeletal malocclusions. Therefore, the objectives of this study are to: (a) Identify the anomalies of the cervical column in patients with skeletal malocclusions (b) Determine the association between cervical vertebral anomalies and skeletal malocclusions. This cross-sectional study was conducted on a total of 90 subjects at the Aga Khan University Hospital, Pakistan. The inclusion criteria were: (1) Pakistani origin; (2) standardized pretreatment profile radiograph with first six cervical vertebrae visible; and (3) accessibility of the second-profile radiograph (mid- or posttreatment). The exclusion criteria were: (1) A prior history of orthodontic treatment; (2) any craniofacial anomaly; and (3) systemic muscle or joint disorder. Lateral cephalograms of all subjects (n = 90) were traced by the principal investigator and sagittal jaw relationship was assessed. A total of 30 subjects each with skeletal Class I, Class II, and Class III malocclusions were selected and the cervical vertebral anomalies were observed on their cephalometric radiographs. The frequencies of cervical vertebral anomalies according to skeletal malocclusion categories and gender were analyzed with the Chi-square test, whereas association of cervical vertebral anomalies with skeletal malocclusions was assessed with logistic regression analysis. The level of significance (P ≤ 0.05) was used for the statistical tests. Most common anomaly observed in the three groups was fusion between C2 and C3 (P = 0.006). This anomaly was found in 20% of subjects with skeletal Class I, 50% of subjects with skeletal Class II and 53.3% with skeletal Class III malocclusions. The highest frequencies of partial cleft at the level of C1 and occipitalization were observed in subjects with skeletal Class II and III malocclusions, respectively. However, none of the subjects showed fusion between C1 and C2 or dehiscence. No statistically significant gender difference was found in the occurrence of morphological deviations of the cervical column. The association of cervical vertebral anomaly was found to be the highest with skeletal Class III and lowest with skeletal Class I malocclusions. Fusion between C2 and C3 seems to be the most commonly occurring anomaly. This anomaly seems to be more often associated with skeletal Class III than skeletal Class I or Class II malocclusions.

Management of Class III Malocclusion with Missing a Maxillary Central Incisor (A Case Report)

Aim: The present case report describes the orthodontic treatment of a patient with a missing maxillary right central incisor and a skeletal Class III jaw relationship due to a retrognathic maxilla. Materials and Methods: Treatment was conducted in two phases, with a removable appliance and Delaire’s facemask used in the first phase and a fixed appliance used in the second phase. Mesial movement of the maxillary canine, first premolar, second premolar and first molar was achieved sequentially over the two phases of treatment. After 36 months, the anterior space was closed, and good intercuspation and interproximal contacts and satisfactory root parallelism were achieved. Finally, interproximal spaces were closed orthodontically, the crown of the upper right lateral incisor was anatomically modified to imitate a central incisor, the right maxillary canine was reshaped slightly along the incisal edge, and a gingivectomy was performed in the maxillary canine area to achieve normal vertical crown proportions. Results: Post-treatment intraoral photographs show satisfactory dental alignment and acceptable overjet and overbite. The patient was satisfied with her teeth and profile. Conclusion: The combination of maxillary protractor and fixed appliance successfully corrected the skeletal Class III malocclusion and achieved forward mesial movement of the maxillary posterior teeth.

Three Dimensional Study of Upper Airway in Different Antero-posterior Jaw Relationships through Cone Beam Computed Tomography

Introduction: This study aims at examining the difference of pharyngeal airways in patients with different occlusion postures, hoping to improve diagnostic methods and provide a stable treatment plan for orthodontic patients. Materials and Methods: The data were gathered through CBCT radiographies of patients from a specialized center for radiology. In each occlusion group according to the performed pilot study, 30 people (90 people in 3 groups of class I, II and III, male and female each) were chosen as the sample. The two-dimentional cephalometric radiographs were obtained from 3D-radiographs, and the patients’ malocclusion postures were determined according overjet and ANB angle, and finally grouped. Next, airway volume and dimensions were measured in cross sectional. Results: Statistical studies showed there is a significant relationship between anteroposterior positions of mandible and the volume of pharyngeal airway. Also, the volume of pharyngeal airway in class III patients is more than those of patients in class I. The volume of pharyngeal airway in class II patients is also less than those of class1 pa ents. Conclusion: Pharyngeal airway in class III is larger and in class II smaller. Therefore, considering this subject can lead to improving diagnostic ways, especially orthognatic surgery treatments, and providing a stable treatment plan for patients who need orthodentic treatment

Significance of Facebow for Dental Restorations

An accurate determination, recording and transfer of jaw relation records from patients to the articulator is essential for the dental restoration function, facial appearance and maintenance of patient’s oral health. As unsatisfactory maxilla-mandibular relationship will eventually lead to failure of complete dentures and necessitate time consuming and costly repairs. Facebow plays an integral part of this maxilla-mandibular relationship transfer from the patient mouth to that of the articulator. Thus, this article attempts to discuss the facebow and its significance in dental restoration treatment. Maxilla is a part of the cranium and is a fixed entity. When the teeth of both jaws come in contact, maxilla becomes related to the mandible so that entire craniomaxillary complex is articulated with a moving bone, which is the mandible. The opening movement to bring the jaw from occlusal to rest position is almost a pure hinge movement. Here the mandible moves on an arc of a circle with a definite radius from the temporomandibular joint. This path of the condyle is determined by the curvature of the condylar head and the curvature of glenoid fossa. Since the radius is not constant for all the patients, it has to be determined for every individual patient, i.e., the relation of maxilla to the opening and closing axis has to be determined. The upper jaw in the human skull is positioned uniquely to the lower jaw. This position is different for every person., Also , the anatomy of maxilla and the temporomandibular joint varies from persons to persons. Thus, recording of the orientation jaw relationship is very important which is done with the help of facebow record. Certain terminologies (according To GPT-8) are important to know the importance of facebow. Hinge axis defined as an imaginary line passing through the two mandibular condyles around which the mandible rotates without translatory movement. Gnathological society defines it as imaginary line connecting the center of one condyle to the center of rotation of the other Like centric relation ,hinge axis is Stable ,Learnable, Recordable, Reproducible and Repeatable. Terminal hinge axis defined as when the condyles are in their most superior position in the articular fossa and the mouth is purely rotated open, the axis around which movement occurs is called as Terminal hinge axis.Clinical Use Of Terminal Hinge Axis is firstly is the location of the transverse hinge axis serves only to orientate the maxilla and to record the static starting point for functional mandibular movements. It does not record centric relation or condylar movements. Secondly it ,allows the transfer of the opening axis of jaws to the articulator so that occlusion would be on the same arc of closure as in the patients mouth. Therefore it is used as an important reference in mounting casts in the articulator, so that the opening axis of the articulator coincides with the terminal hinge axis of the patient. And this axis can be located when the mandible is in its most posterior unstrained position by means of a Face bow. I. Face Bow The face bow is a caliper like device that is used to record the relationship of the jaws to the temporomandibular joints or the opening axis of the jaws and to orient the casts in the same relationship to the opening axis of the articulator.The term, “face bow,” probably evolved from a statement by A.D. Grit man, who described the “implement devised by Prof. Snow. as a bow of metal (that) reaches around the face. Face bow record is used in balanced occlusion in complete denture, in edentulous Class I & II cases, Open anterior bite or end to end relationship, Single restoration on II molar not for premolar and I molar, Segmental restoration, Anterior restoration and restoration of entire quadrant Significance of Facebow for Dental Restorations www.iosrjournals.org 2 | Page II. Parts Of Face Bow It is constructed in 3 bars, 1 anterior, 2 lateral. TABLE-1 PARTS OF FACEBOW

Comparison of condylar displacement between three biotypological facial groups by using mounted models and a mandibular position indicator.

ObjectiveFacial-type-associated variations in diagnostic features have several implications in orthodontics. For example, in hyperdivergent craniofacial types, growth imbalances are compensated by displacement of the condyle. When diagnosis and treatment planning involves centric relation (CR), detailed knowledge of the condylar position is desirable. The present study aimed to measure condylar displacement (CD) between CR and maximum intercuspation in three facial types of an asymptomatic orthodontic population.MethodsThe study was conducted in 108 patients classified into three groups of 36 individuals each (27 women and 9 men; mean age, 20.5 years), based on the following facial patterns: hyperdivergent, hypodivergent, and intermediate. To quantify CD along the horizontal and vertical axes, the condylar position was analyzed using mounted casts on a semi-adjustable articulator and a mandibular position indicator. The Student t-test was used to compare CD between the groups.ResultsVertical displacement was found to be significantly different between the hyperdivergent and hypodivergent groups (p < 0.0002) and between the hyperdivergent and intermediate groups (p < 0.0006). The differences in horizontal displacement were not significant between the groups. In each group, vertical CD was more evident than horizontal displacement was.ConclusionsAll facial types, especially the hyperdivergent type, carried a significantly high risk of CD. Therefore, the possibility of CD should be carefully evaluated and considered in the assessment of all orthodontic cases in order to accurately assess jaw relationships and avoid possible misdiagnosis.

Evaluation of dental maturation in children according to sagittal jaw relationship.

Objective:The aims of this retrospective study were to determine compliance with dental and chronological ages and to analyze the relationships between dental age and orthodontic sagittal anomalies.Materials and Methods:A total of 221 subjects between the ages of 7 and 15.9 years (165 girls and 156 boys) were included in the study. The dental age of seven left mandibular teeth was assessed according to the Demirjian method. The maxillary protrusion, mandibular protrusion, maxillo-mandibular and vertical plane angles were measured from cephalometric films.Results:The mean difference between the chronological age and dental age in female patients was 0.94 years and 0.33 years in male patients (P < 0.01). No differences between the sagittal classification groups were found. There was no relationship between dental age and the SNA° or the GoGn-SN°. A statistically significant negative relationship was found between dental age and the SNB° and there was a significant linear relationship between dental age and the ANB°.Conclusion:Dental age in girls and boys has been estimated to be more advanced than chronological age in all classes and dental maturation advanced in cases with a tendency to develop Class II malocclusions.

Class II division 1 malocclusions treated with fixed lingual mandibular growth modificator (FLMGM): The mechanism of sagittal occlusal correction

Objectives: The objective of this study is to assess skeletal and dental changes contributing to sagittal correction of Class II malocclusion with fixed lingual mandibular growth modificator (FLMGM). Materials and Methods: A total of 38 patients with dental Class II division 1 malocclusion and retrognathic mandible comprised the study sample. All were in the pubertal growth spurt. While FLMGM was applied to the treatment group ( n = 21, 13.2 years), no treatment was performed on the control group ( n = 17, 12.5 years). Digital lateral cephalograms obtained at the beginning and end of treatment/observation period of 8 months were evaluated using sagittal occlusal analysis. Paired and independent t -tests were used to assess the differences within and between groups. Results: Fixed lingual mandibular growth modificator treatment resulted in the following significant changes: (1) Total mandibular length increased; (2) sagittal jaw relation enhanced due to chin advancement; (3) overjet reduced (4.06 mm) mainly as a result of skeletal mandibular advancement (83%) in combination with maxillary incisor retraction (17%); (4) Class II molar relation improved (5.56 mm) by a contribution of mandibular advancement (61%) and maxillary molar distalization (39%). Conclusions: Sagittal occlusal relationships efficiently improved by greater skeletal than dental changes. Stable horizontal position of lower molars and incisors was a benefit of FLMGM treatment.

Rehabilitation of Non-Syndromic Oligodontia of Primary and Permanent Dentition in Young patient-A Rare Case Report

Background: Oligodontia is a genetic disorder which represents the congenital absence of more than six teeth in primary, permanent or both dentitions. It is usually a part of a syndrome and seldom occurs as an isolated entity. Genes responsible for non syndromic oligodontia are found to be MSX1 and PAX9 genes. Methods: Karyotyping was done taking sample from peripheral blood. Cytogenetic chromosome analysis revealed a normal male karyotype (46, XY) without any structural or numerical chromosome abnormalities. Hand wrists, clavicles, vertebral skeleton, skull and chest were found to be normal on radiological examination. After excluding other possible differential factors, the final diagnosis of non-syndromic Oligodontia was made. Preliminary impressions were made using impression compound and was molded on the edentulous ridge. Custom trays were fabricated and border molding was done using green stick impression compound and secondary impressions were made using zinc oxide eugenol impression paste. After maxillo-mandibular jaw relations, dentures were processed through compression molding technique. Dentures were inserted and the patient was taught about the insertion and removal of the dentures. Post insertion instructions regarding denture wear, functions of speech, mastication, hygiene and maintenance were given to the patient and the parent. Results: The patient was using prosthesis and happy with it during one year follow up. The rehabilitation with removable dentures at current age and later with osseo-integrated implants served as a satisfactory treatment outcome in such patients. Conclusion: This case report presents prosthodontic rehabilitation of a rare case of non-syndromic oligodontia in a 7-year old male patient with agenesis of all permanent teeth except the maxillary central incisors.

The role of virtual articulator in prosthetic and restorative dentistry.

Virtual reality is a computer based technology linked with the future of dentistry and dental practice. The virtual articulator is one such application in prosthetic and restorative dentistry based on virtual reality that will significantly reduce the limitations of the mechanical articulator, and by simulation of real patient data, allow analyses with regard to static and dynamic occlusion as well as to jaw relation. It is the purpose of this article to present the concepts and strategies for a future replacement of the mechanical articulator by a virtual one. Also, a brief note on virtual reality haptic system has been highlighted along with newly developed touch enabled virtual articulator.

치주인대의 비선형성을 고려한 치아 교정용 호선의 굽힘 최적화

Orthodontics is a branch of dentistry that is concerned with the study and treatment of malocclusion, which may result from tooth irregularities, disproportionate jaw relationships, or both. Orthodontic devices consist of brackets, archwire connected to each bracket, and bends and hooks for auxiliary functions. Basically, orthodontics involves the interaction of brackets and archwire. It should be noted that uncontrolled tipping can occur due to unwanted movement of the teeth. The bending of an archwire can control the angle of an archwire and the rotation of a tooth. In this study, we predict the relationship between the bending angle of an archwire and the rotation of a tooth using the Kriging interpolation method. Also, we calculate the angle of an archwire that occurs at the minimum value of tooth rotation.

Reproducibility of habitual intercuspation in vivo

ObjectivesThe aim of this in vivo study was to investigate how reproducible individuals find their habitual intercuspation. MethodsA new type of highly accurate measuring procedure was involved using an intraoral optical scanning device (Cerec Bluecam). First, a pilot test investigated the accuracy of the procedure within a standardized setting. With regard to the in vivo study, fifteen participants with full dentition were selected. For each of these individuals, eight scans were taken both in the morning and in the afternoon. Furthermore, during each session, scans were taken both in horizontal and upright position. In order to compare this to ubiquitous used processes, plaster replicas of five individuals were investigated as well. The scans were analysed, and the differences in the position of the lower jaw were calculated by a specialized superimposition program (n=570 comparisons/OraCheck). ResultsThe results showed that there was no significant difference between the time of day and the position of the patient. The overall mean±SD value for locating the habitual intercuspation was 42±34μm, however ranging from 22±9μm to 77±58μm for single individuals. On the other hand, the differences in positioning plaster replicas reached a mean of 135±77μm. ConclusionsThe reproducibility of the habitual intercuspation can be obtained under in vivo conditions by a newly developed and highly accurate measuring procedure. Individuals with full dentition show values in average of 42μm. Clinical significanceDetermining the occlusal jaw relation is an important precondition in restorative dentistry and many methods are proposed for a proper occlusal registration. Although much is known about in vitro accuracy of these techniques, little is known how reproducible the habitual occlusal position itself is found between individuals.

Systematic Analysis of Clinical Outcomes of Anterior Maxillary and Mandibular Subapical Osteotomy With Preoperative Modeling in the Treatment of Bimaxillary Protrusion

The purpose of this study was to determine the changes in teeth and hard tissues after preoperative modeling and bimaxillary anterior subapical osteotomy for the treatment of bimaxillary protrusion. Cephalometric analysis was used to evaluate the aesthetic effects and occlusal relationships obtained. The subjects included 19 women and 1 man (aged 19-41 years; average, 29 years) with bimaxillary protrusion who underwent anterior subapical osteotomy of both the maxilla and mandible, with simultaneous genioplasty, if required. Based on a preoperative computer-aided manufacturing/design-assisted and model surgical design and an occlusal guide plate, new occlusal relationships were established for the patients. In addition, the preoperative and postoperative cephalometric radiographs were systematically analyzed. In all patients, the surgical incisions underwent primary healing, with no infection or osteonecrosis. Significant differences were observed in the preoperative and postoperative values of all hard tissue and teeth parameters, except for SGn-FH degrees and Co-MP. The most obvious significant differences were seen in L1-OP°, Id-Pog-Go°, IIA°, U1E-Apog, L1E-Apog, U1E-NA, and L1-NA° (P < 0.001). Postoperative follow-up lasted for 12 to 36 months. All patients eventually achieved normal jaw relationships, tooth arch forms, and Spee curves. No evident irregularities of teeth arrangement or abnormal occlusal relationships were observed. All patients were satisfied with their postoperative facial appearance, except for 1 patient, who underwent repeat surgery because of relapse. With the use of a precise preoperative model surgical design, orthognathic surgery, a simple and time-saving technique, can be used to correct bimaxillary protrusion with satisfactory postoperative occlusal relationship and facial aesthetic appearance and minimal postoperative complications.

Facial Symmetry: An Illusion?

Objective: To investigate the laterality of the normal asymmetry of the human face, examining differences in laterality in relation to sex, and skeletal classification. Materials and methods: A sample of 120 patients (60 males and 60 females; mean age, 15 years; range, 16-22 years) who had received orthodontic clinical examination at AME’s Dental College and Hospital were selected. Selection was made in such a way that following malocclusions with equal sexual distribution was possible from the patient database. Patients selected were classified into skeletal Class I (25 males and 25 females), Class II (25 males and 25 females) and Class III (10 males and 10 females) based on ANB angle. The number was predecided to be the same and also was based on the number of patients with following malocclusions reported to the department. Differences in length between distances from the points at which ear rods were inserted to the facial midline and the perpendicular distance from the softtissue menton to the facial midline were measured on a frontofacial photograph. Subjects with a discrepancy of more than three standard deviations of the measurement error were categorized as having left- or right-sided laterality. Results: Of subjects with facial asymmetry, 74.1% had a wider right hemiface, and 51.6% of those with chin deviation had left-sided laterality. These tendencies were independent of sex or skeletal jaw relationships. Conclusion: These results suggest that laterality in the normal asymmetry of the face, which is consistently found in humans, is likely to be a hereditary rather than an acquired trait.