Inclination Of Teeth Research Articles

High efficiency gears synthesis by avoid the interferences

The paper presents an original method to determine the efficiency of the gear, the forces of the gearing, the velocities and the powers. It is analyzing the influence of a few parameters concerning gear efficiency.These parameters are:z1 - the number of teeth for the primary wheel of gear; z2 - the number of teeth of the secondary wheel of gear; alpha0 - the normal pressure angle on the divided circle; beta - the inclination angle. With the relations presented in this paper, it can synthesize the gear’s mechanisms. Today, the gears are present everywhere, in the mechanical’s world (In vehicle’s industries, in electronics and electro-technique equipments, in energetically industries, etc). Optimizing this mechanism (the gears mechanism), we can improve the functionality of the transmissions with gears. At the gear mechanisms an important problem is the interference of the teeth. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta), and in function of the transmission ratio (i).

Comparison of virtual and manual tooth setups with digital and plaster models in extraction cases

The aim of this study was to compare the virtual and manual tooth setups with digital and plaster models in extraction cases by measuring various occlusal parameters and applying the American Board of Orthodontics objective grading system. Linear intra-arch and interarch dimensions (arch width and length, perimeter, overjet, and overbite), angular variables (tip, torque, and rotation), and American Board of Orthodontics objective grading system scores obtained from a digital virtual setup model were compared with those from a plaster model setup. The digital virtual setup model resulted in smaller arch perimeters than did the plaster setup model by 2.20 mm in the maxillary arch (P<0.01) and 1.30 mm in the mandibular arch (P<0.05). The digital virtual setup also exhibited significantly lower values for overbite and overjet (P<0.01). The digital virtual setup had tendencies toward mesial angulation of the anterior teeth, labial inclination of the maxillary anterior teeth (P<0.05), and distal in-rotation of the mandibular teeth (P<0.05). The resulting American Board of Orthodontics objective grading system evaluation showed that larger deductions for overjet, occlusal contact, and total score (P<0.01) were required for the digital than for the manual setup model. Digital and manual setups lead to similar measurements for intra-arch and interarch occlusal variables. However, because of the possibility of collision on proximal and occlusal contact, delicate adjustments in proximal and occlusal contacts are required.

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.

GEAR DESIGN

The paper presents an original method to determine the efficiency of the gear, the forces of the gearing, the velocities and the powers. The originality of this method relies on the eliminated friction modulus. The first chapters are analyzing the influence of a few parameters concerning gear efficiency. These parameters are: z1 - the number of teeth for the primary wheel of gear; z2 - the number of teeth of the secondary wheel of gear; alpha0 - the normal pressure angle on the divided circle; beta - the inclination angle. With the relations presented in this paper, it can synthesize the gear’s mechanisms. Today, the gears are present everywhere, in the mechanical’s world (In vehicle’s industries, in electronics and electro-technique equipments, in energetically industries, etc.). Optimizing this mechanism (the gears mechanism), we can improve the functionality of the transmissions with gears. At the gear mechanisms an important problem is the interference of the teeth. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta), and in function transmission ratio (i). The last chapter presents an original method to make the geometric synthesis of the gear, having in view the minimum number of teeth of the driving wheel. The classical methods use many different relations to determine the minimum number of teeth of the driving wheel. By this paper we want to give a unitary method to determine the minimum number of teeth of the driving wheel 1, to avoid the interference between the teeth of the two wheels (of the gear).

A normative study to evaluate inclination and angulation of teeth in North Indian population and comparision of expression of torque in preadjusted appliances.

Aim:The aim of this study was to evaluate angulation and inclination of teeth from the study models of individuals with normal occlusion and evaluation of actual expression of torque expressed by three different bracket systems.Materials and Methods:In this study, the inclination and angulation were measured on 30 study models of North Indian individuals. A self-developed instrument (torque angle gauge) was used for the measurement. Fifteen study models were duplicated for the evaluation of torque expression in the bracket of three different manufacturers with different shape and size of bases.Results:The results give the mean, minimum and maximum, standard deviation of the normative data individually for each tooth. A significant correlation was noted in the angulation of maxillary canine and first premolar, and between premolars; and between mandibular central incisor with lateral incisor and canine, and between premolars.Conclusions:There was a highly significant correlation of teeth angulation and inclination in the maxillary and mandibular arch. Though the error in expression of torque was not significant, but it showed a large range, indicating the need to vary the position of brackets in different bracket systems for achieving optimum torque.

Possibility of determining relations between translatory movement and inclination of agonist teeth after extraction of first permanent molars

Introduction. Tooth extractions, particularly of the permanent teeth, lead to different and numerous consequences. It is known that the incidence of caries and the incidence of premature extractions are the highest with the first permanent molars. The aims of this study were to examine the possibility of determining the relations between the translatory movement and the agonist teeth inclination depending on the time of the performed extraction, as well as on the temporal distance from the moment of extracting the first permanent molar to the moment of analyzing the changes. Material and Methods. The study was performed on the sample of 185 subjects, their age ranging from 11 to 26 years (X=14) with early (by the age of 11 years) and late performed extraction of the first permanent molars in the maxilla and mandible and determined class I of occlusal relationship. Results. The relation, expressed by the mathematical expression, between the translatory movement and tooth inclination has been confirmed, but only in case of late extractions. As for early extractions, the obtained results of the correlation coefficient value showed no relations between translatory movement and tooth inclination. Conclusion. The relation between translatory movement and teeth inclination (the second premolars and the second permanent molars) expressed by the mathematical expression has been confirmed by the given values of the correlation coefficient, but only in case of late performed extractions. The biggest changes of the analyzed teeth position (the second premolars and the second permanent molars) occur in the first year after late extractions of the first permanent molars.

Effects of a hinged expansion screw for median mandibular distraction treatment on the lower first molars regarding tooth inclination and intermolar transverse distance

The goal of this study was to assess the extent to which median mandibular distraction via a cemented and screw-retained full-coverage splint appliance employing a hinged expansion screw causes inclination changes in the lower first molars and widens the dental arch. Our study included 17 patients (12 females and 5 males; average age 16 years and 3 months) who presented with transverse space deficits and pronounced dental crowding. Baseline and final mandibular casts reflecting the situations before and after 6 weeks of median distraction therapy were created, scanned, and matched via their coordinate systems. Perpendiculars were drawn at the geometric centers between the cusp tips of teeth 36 and 46 and projected against the frontal plane. The intersection angles yielded single-tooth and total inclination values for both molars, and the difference between the intermolar distances measured at the geometric centers of both teeth provided the amount of transverse expansion. An intraclass correlation coefficient (ICC) of >0.99 was obtained in a series of three measurements. After distraction treatment, the total inclination values between teeth 36 and 46 changed by +2.93 ± 9.14°. The corresponding single-tooth inclinations changed by +0.68 ± 6.32° and -2.25 ± 4.33°, respectively. Both molars underwent similar degrees of buccal or lingual tipping. Compared to a mean expansion of +6.9 ± 1.83 mm at the distraction screw, a distance increase of only +3.77 ± 1.27 mm along the transversal connecting teeth 36 and 46 was recorded. Pearson's correlation coefficient was 0.336 between total tipping and intermolar expansion (p=0.187) and -0.426 between total tipping and patient age (p=0.088). Expansion amounts were approximately twice as long at the expansion screw as between the first molars. This V-shaped expansion pattern was due to the hinged connections between each expansion screw and the full-coverage splints. The buccal and lingual tipping of molars measured may be due to varying heights of the posterior alveolar ridge during mixed dentition or to anatomy-related differences in the expansion-screw position. In all cases we observed a mainly parallel opening of the distraction gap on the vertical plane.

Dentoskeletal effects of Class II malocclusion treatment with the Twin Block appliance in a Brazilian sample: A prospective study

ObjectiveThe aim of this study was to assess the dentoskeletal effects of Class II malocclusion treatment performed with the Twin Block appliance. MethodsThe experimental group comprised 20 individuals with initial mean age of 11.76 years and was treated for a period of 1.13 years. The control group comprised 25 individuals with initial mean age of 11.39 years and a follow-up period of 1.07 years. Lateral cephalograms were taken at treatment onset and completion to assess treatment outcomes. Intergroup comparison was performed by means of the chi-square and independent t tests. ResultsThe Twin Block appliance did not show significant effects on the maxillary component. The mandibular component showed a statistically significant increase in the effective mandibular length (Co-Gn) and significant improvement in the maxillomandibular relationship. The maxillary and mandibular dentoalveolar components presented a significant inclination of anterior teeth in both arches. The maxillary incisors were lingually tipped and retruded, while the mandibular incisors were labially tipped and protruded. ConclusionsThe Twin Block appliance has great effectiveness for correction of skeletal Class II malocclusion in individuals with growth potential. Most changes are of dentoalveolar nature with a large component of tooth inclination associated with a significant skeletal effect on the mandible.

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.

Extraction and non-extraction therapy in class II/1 patients

Introduction: Class II malocclusion is characterized by distoclusion and is divided into two divisions depending on the inclination of the upper front teeth. The first division is characterized by protrusion of the upper front teeth. Treatment possibilities of class II/1 malocclusion depend on the skeletal form. Therapy of dentoalveolar types of class II/1 malocclusion is exclusively orthodontic. More emphasized skeletal forms of class II/1 malocclusion may require surgery apart from orthodontic therapy. Casse raport: In this paper, the extraction and nonextraction treatment of 13 years old patients - M.P.(boy) and I.T. (girl) was shown, respectively. The diagnosis was based on clinical and functional intraoral findings, analysis of dental casts, face photos, orthopatomogram and profile x-ray. Nonextraction therapy was suggested for a boy and extraction therapy for a girl, combined with the use of upper and lower fixed appliances. In the treatment, technique of straight arch, Dentaurum brackets, root prescriptions, slot 22 were used. In the male patient, there was a slight maxillary prognathism, mandibular retrognathism, anterior type of growth, protrusion of the upper incisors and retrusion of the lower ones. The body of maxilla was shorter by 4 mm with regard to the cranial base. In the female patient the extraction of the upper first premolars was performed because of maxillary prognathism, mandibular retrognathism, increased length of the body of maxilla, decreased length of the body of maxilla and severe protrusion of the upper frontal teeth. After the treatment, functional occlusion and improvement in facial aesthetics was achieved in both patients. Facial changes were more apparent in the patient who underwent the extraction treatment. After completion of treatment, it is necessary to maintain the obtained results.

Comparative study of dentascan and radiography for radiological evaluation of impacted teeth.

Impacted teeth present a very common problem in dentistry due to the variable numbers of problems they cause. They have previously been imaged by radiography which is very inaccurate. Dental CT is an upcoming modality which very accurately images the teeth. The aim of our study was to compare the efficacy of Dental CT with radiography in assessing the morphology of the impacted tooth and its relation to adjacent structures. We conducted a hospital based prospective study in which all patients with impacted teeth who underwent Dental CT and Radiographic evaluation were evaluated. The morphology of all the teeth was well visualized on CT. Resorption of adjacent tooth was missed in 7 teeth by radiography. In a significant number of cases (10/30) the relation of the impacted tooth with the mandibular canal could not be visualized on the radiographs. We concluded that Dental CT yields markedly better information than radiographs regarding impacted teeth with respect to divergence of the roots, relation of the impacted tooth with the adjacent tooth, nasal floor, maxillary sinus and mandibular canal. However, Dental CT was found to be only marginally better than Radiographs for assessment of number of roots, inclination of the impacted tooth and relation of the tooth with alveolar crest. Dental CT was also proved to be an indispensable diagnostic tool for the determination of the buccolingual inclination and relationsof the impacted tooth.

Tooth Inclination Protractor: Validity and Reliability

Adequate incisor inclination influences aesthetics, patient’s self-perception, function, stability and phonetics. Incisor inclination was traditionally assessed by lateral cephalogram, prone to digitising errors. Techniques utilising dental casts evolved, but none is routinely used because of unreliability, cost, time consumption or requirement of experienced personnel to record and process the data. The aim of this study was to critically assess the validity and reliability of tooth inclination protractor (TIP) in recording incisor crown inclination and to compare it with traditional lateral cephalograms. TIP and lateral cephalograms were used for recording the following angles: maxillary incisor to palatal plane, maxillary incisor to occlusal plane, mandibular incisor to mandibular plane and mandibular incisor to occlusal plane of 30 subjects with class I malocclusion. TIP recorded maxillary incisor crown inclination 18° less and mandibular crown inclination 10° less than cephalogram. The TIP was not reliable, yet it is a valuable tool for replacing mid-treatment and post-treatment cephalogram.

뇌성마비환자에서 가철성장치를 이용한 상악 전치부 돌출 완화 : 증례보고

14세 남환이 정기검진을 위해 내원하여 임상 구강검사 결과 상악 전치의 돌출과 상악궁 협착이 관찰되었다. 환아는 뇌성마비를 가지고 있었으나 간단한 설명을 이해하고 쉬운 지시를 수행할 수 있었으므로 가철성 장치를 이용한 교정치료를 시도하였다. 단계적이고 주의 깊은 접근을 통해 상악궁 협착 해소 및 상악 전치의 돌출을 완화할 수 있었다. 뇌성마비 환아의 경우 특징적으로 상악 전치의 돌출이 흔히 나타나는데, 이는외상의 위험에 쉽게 노출된다. 하지만 뇌성마비 환아에서 나타나는 특징적인 반사, 침 흘리기 습관, 행동조절의 어려움 등을 이유로 많은 임상의들이 교정 치료를 포기하게 된다. 적절한 환자 선정과 수행 가능한 치료목표를 세운다면, 뇌성마비 환아에서도 단계적이고 반복적인 행동조절과 약물을 이용하여 치료가 가능하다. 교정 치료를 통해 얻어진 상악 전치의 돌출 완화는 외상의 위험성을 줄이고 더 나은 심미성을 제공하는 긍정적인 효과를 가져오게 된다. 따라서 임상의들은 뇌성마비 환아의 치료에 대한 인식 변화 및 개선을 위한 적극적인 노력이 필요할 것이며, 뇌성마비 환아들은 더 나은 구강 건강을 영위할 수 있을 것이다. Cerebral palsy is one of the primary handicapping conditions of childhood. The prevalence of malocclusions in patients with cerebral palsy is approximately twice than in general population. Even though these high rates of malocclusions, most clinicians may feel uncomfortable about treating such problems to reduce inclination of anterior teeth because to reduce of protrusion makes to decrease risk of trauma. This is the case report about mitigation of maxillary anterior teeth protrusion in patient with cerebral palsy. A 14 year old boy who had cerebral palsy visited our dental hospital. He had severe protrusive maxillary anterior teeth and narrow arch form. He was experienced at using Castillo morales appliance in early childhood. He had mild mental retardation and was able to learn simple skills. He and his parents had willing to improve his dental problems. A gentle impression taking on maxilla was done. Removable appliance was made including median screw and labial bow. We provide a period of adaption for 3 weeks. After of anterior teeth through activation of labial bow was done once a month by dentist. The treatment carried out for 10 months and we could observe reduced labial inclination of maxillary right central incisor and more wide arch form. Hawley type retainer was set at maxilla for retention. In conclusion, accompanying careful case selection and treatment, patient with cerebral palsy can be treated and should not be ignored their orthodontic needs.

20대 여성 정상교합자에서 임상치관의 순·설측 경사도와 근·원심 경사도에 관한 연구

Purpose: This study is to present a standard value for clinical crown angulation and inclination required in laboratory process and see if the value can be used for actual laboratory process. Methods: In order to find out a standard value for clinical crown angulation and inclination, this study made a study model of normal occlusion of 21 females in twenties. The clinical crown angulation and inclination of both six-maxillary and six-mandibular anterior teeth are measured by Set-up Model Checker. From the measured value above, the mean and standard deviation of the twelve teeth are obtained, and then the mean of the teeth between right and left side is calculated. Results: Each clinical crown angulation of maxillary central incisor, lateral incisor, and canine is like this; <TEX>$1.0^{\circ}{\pm}1.3^{\circ}$</TEX>, <TEX>$3.0^{\circ}{\pm}1.3^{\circ}$</TEX>, and <TEX>$5.0^{\circ}{\pm}1.4^{\circ}$</TEX>. In case of mandibular, each degree is like this; <TEX>$0.6^{\circ}{\pm}1.1^{\circ}$</TEX>, <TEX>$1.5^{\circ}{\pm}1.1^{\circ}$</TEX>, and <TEX>$4.1^{\circ}{\pm}1.1^{\circ}$</TEX>. Each clinical crown inclination of maxillary central incisor, lateral incisor, and canine is like this; <TEX>$6.1^{\circ}{\pm}1.8^{\circ}$</TEX>, <TEX>$4.5^{\circ}{\pm}1.9^{\circ}$</TEX>, and <TEX>$-6.2^{\circ}{\pm}1.4^{\circ}$</TEX>. In case of mandibular, each degree is like this; <TEX>$0.3^{\circ}{\pm}1.5^{\circ}$</TEX>, <TEX>$0.3^{\circ}{\pm}1.8^{\circ}$</TEX>, and <TEX>$-7.5^{\circ}{\pm}1.8^{\circ}$</TEX>. Conclusion: As the result, the mean value for clinical crown angulation and inclination can be referred to actual laboratory process. However, the mean value is different from those of the precedent study and an unsatisfied one for adopting the standard value.

Measured Comparison of Leakage and Rotordynamic Characteristics for a Slanted-Tooth and a Straight-Tooth Labyrinth Seal

Measured results are presented to compare rotordynamic coefficients and leakage of a slanted-tooth labyrinth seal and a straight-tooth labyrinth seal. Both seals had identical pitch, depth, and number of teeth. The teeth inclination angle of the teeth on the slanted-tooth labyrinth was 65 deg from the normal axis. Experiments were carried out at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10.2, 15.35, and 20.2 krpm, and a radial clearance of 0.2 mm (8 mils). One zero and two positive inlet preswirl ratios were used. The results show only minute difference in the rotordynamic coefficients between the two seals. The slanted-tooth labyrinth seal consistently leaked approximately 10% less at all conditions. Predictions were made using a one control volume bulk-flow model (1CVM) which was developed for a straight-tooth labyrinth seal design. 1CVM under-predicted the rotordynamic coefficients and the leakage.

Cone beam computed tomography anaylsis of pharyngeal airway space changes in patients undergoing orthognathic surgery

Maxillary transversal deficiency is characterized by unilateral or bilateral posterior cross-bite, crammed and rotated teeth, and narrow palate, and its treatment is surgically assisted maxillary expansion for adult patients. This procedure affects not only bones, but also the teeth (especially the post of the expander device), nasal cavity and air space, lips and surrounding soft tissues. The aim of the present study was to evaluate dento-skeletal alterations of patients presenting atrophic maxilla who underwent surgically assisted maxillary expansion using cone beam computed tomography (CBCT). For this, 14 patients underwent CBCT before and after (15, 60 and 180 post-operative days) surgically assisted maxillary expansion by subtotal Le Fort I osteotomy, and the thickness of buccal and palatal cortical bones and the angulation of the long axis of the upper posterior teeth (1 M, 2 M, 1 PM and 2 PM) were measured. Data were statistically analyzed. Results showed changes in thickness of buccal and palatal cortical areas analyzed, which allowed us to conclude that EMCA, even though using surgical techniques, teeth can be translated by displacement and buccal inclination. Furthermore, it was concluded that when the shift occurred and buccal tooth inclination, these seem to have been accompanied by buccal cortical bone resorption and bone formation in the cortical palate.

Association of dentoskeletal morphology with incisor inclination in angle class II patients: a retrospective cephalometric study

IntroductionThe purpose of this study was to identify possible dentoskeletal parameters associated with variation of anterior tooth inclination in Angle Class II subdivisions.MethodsPre-treatment lateral radiographs of 144 Class II patients (68 males, 76 females) aged 9 to 17 years were classified for upper incisor inclination into three groups (proclined, normally inclined, retroclined) homogeneous for gender and skeletal jaw relationship. The effect of age on the 22 cephalometric variables was controlled by covariance analysis.ResultsMultivariate analysis of the cephalometric parameters indicated significant inter-group differences. Systematic associations with incisor inclination were revealed using rank correlation: Lower incisor proclination, Wits appraisal and gonial angle significantly decreased (0.04 ≥ p ≥ 0.002), while intercisal angle, mandibular total and corpus length and nasolabial angle increased (0.04 ≥ p ≥ 0.001) with decreasing incisor proclination.ConclusionsClear-cut classification criteria and control of confounding effects may clarify conflicting previous findings on dentoskeletal differences between Class II subdivisions in the mixed dentition. Only minor dentoskeletal differences appear to be associated with incisor inclination. The increased interincisal and nasolabial angle in Class II division 2 subjects are due to reclination of both upper and lower incisors. Jaw positions and chin prominence are not significantly different between the subdivisions. However, Wits appraisal is decreased in Class II division 2. The increased mandibular length observed in Class II division 2 requires further scrutinization.

Related factors and effectiveness of rapid teeth movement through reducing resistance and distraction

To investigate the role of reducing resistance and distraction in rapid teeth movement and its reliability by establishing the Beagle dogs' experimental model. The left or right sides in mandibles of 20 beagles were randomly operated with different treatments: distraction twice a day through reducing resistance; distraction 6 times a day through reducing resistance; conventional distraction through reducing resistance; and conventional distraction (the control group). Each treatment was carried out in 10 sides. The pulp vitality, tooth mobility and distance of teeth transportation were evaluated at different time points: before the distraction, distraction after 15 days, retaining 30 days after 15 days of distraction. The degree of inclination, root resorption and alveolar bone density of the compressive areas were evaluated by cone-beam computed tomography images. The distance of teeth transportation was similar in groups distraction twice daily and 6 times a day through reducing resistance (P>0.05), but their speed of transportation was significantly higher than that of conventional distraction through reducing resistance. The conventional distraction group had the lowest speed of transportation. The pulp vitality of distracted teeth was normal, and no root comprehensive resorption and periodontal defect were found. Distracted teeth in the reduced resistance and distraction groups (13.9°±3.5°) tipped more that in the conventional distraction group (6.6°±1.3°) (P<0.05). Reducing resistance and distraction are inseparable factors to realize fast teeth moving. The rate of orthodontic tooth movement can be accelerated through resistance reduction and periodontal distraction without obvious unfavorable effects but at minimal acceptable teeth inclination.

Design of an Orthodontic Torque Simulator for Measurement of Bracket Deformation

The design and testing of an orthodontic torque simulator that reproduces the effect of archwire rotation on orthodontic brackets is described. This unique device is capable of simultaneously measuring the deformation and loads applied to an orthodontic bracket due to archwire rotation. Archwire rotation is used by orthodontists to correct the inclination of teeth within the mouth. This orthodontic torque simulator will provide knowledge of the deformation and loads applied to orthodontic bracket that will aide clinicians by describing the effect of archwire rotation on brackets. This will also impact that design on new archwire\bracket systems by providing an assessment of performance. Deformation of the orthodontic bracket tie wings is measured using a digital image correlation process to measure elastic and plastic deformation. The magnitude of force and moments applied to the bracket though the archwire is also measured using a six-axis load cell. Initial tests have been performed on two orthodontic brackets of varying geometry to demonstrate the measurement capability of the orthodontic torque simulator. The demonstration experiment shows that a Damon Q bracket had a final plastic deformation after a single loading of 0.022 mm while the Speed bracket deformed 0.071 mm. This indicates that the Speed bracket plastically deforms 3.2 times more than the Damon Q bracket for similar magnitude of applied moment. The demonstration experiment demonstrates that bracket geometry affect the deformation of orthodontic brackets and this difference can be detected using the orthodontic torque simulator.

Three-dimensional deformation of orthodontic brackets

Braces are used by orthodontists to correct the misalignment of teeth in the mouth. Archwire rotation is a particular procedure used to correct tooth inclination. Wire rotation can result in deformation to the orthodontic brackets, and an orthodontic torque simulator has been designed to examine this wire–bracket interaction. An optical technique has been employed to measure the deformation due to size and geometric constraints of the orthodontic brackets. Images of orthodontic brackets are collected using a stereo microscope and two charge-coupled device cameras, and deformation of orthodontic brackets is measured using a three-dimensional digital image correlation technique. The three-dimensional deformation of orthodontic brackets will be evaluated. The repeatability of the three-dimensional digital image correlation measurement method was evaluated by performing 30 archwire rotation tests using the same bracket and archwire. Finally, five Damon 3MX and five In-Ovation R self-ligating brackets will be compared using this technique to demonstrate the effect of archwire rotation on bracket design.