Critical assessment of a device to measure incisor crown inclination.

The aims of this study were to critically assess the use of a disposable device--the tooth inclination protractor (TIP)--to record incisor crown inclination and to compare its reliability and validity with that of traditional cephalometric radiographic analysis. The sample comprised 30 dental students with lateral cephalometric radiographs and dental casts. Four examiners were trained and calibrated to digitize radiographs and to use intraoral (on patients and dental casts) and extraoral (on dental casts) TIPs. The following angles were measured on the radiographs: maxillary incisor to maxillary plane, mandibular incisor to mandibular plane, maxillary incisor to occlusal plane, and mandibular incisor to occlusal plane. Measurements were also made with the TIP: maxillary incisor to occlusal plane and mandibular incisor to occlusal plane. All techniques were reliable between examiners. There were statistically significant systematic differences between the TIP and the radiographic assessments. The following differences were found. The TIP tended to record maxillary incisor crown inclination an average of 14 degrees less than maxillary incisor to maxillary plane. The TIP tended to record mandibular incisor crown inclination as similar to mandibular incisor to mandibular plane. The TIP recorded mandibular crown inclination 19 degrees less than mandibular incisor to occlusal plane. The disposable TIP was shown to be a simple, inexpensive, reliable, and valid method of assessing incisor inclination.     

Three-dimensional analysis of the occlusal plane related to the hamular-incisive-papilla occlusal plane in young adults

The planes which serve as references for cranium and face in dental clinical application included the occlusal plane, Frankfort plane, Camper's plane and hamular-incisive-papilla (HIP) plane. The HIP occlusal plane is a horizontal plane passing through the bilateral hamular notches and the incisive papilla (Dent Surv. 1975;51:60). The aim of this study was to estimate the relationship between the various occlusal planes and the HIP plane in Taiwanese young adults with approximately optimal occlusion. Study casts of 100 young adults (50 men and 50 women) were selected in this study. All market points on the maxillary casts were measured by a three-dimensional precise measuring device. The angular relationship between the four various occlusal planes and the HIP plane were investigated. The vertical distances between the cusp tips and incisal edges of maxillary teeth to the HIP plane were measured. Data were performed by the Statistic analysis software programme (JMP 4.02). The Student's t-test and Pearson's correlation test were used to test the statistical significance (P < 0.05). The results showed that the occlusal plane defined as the incisal edge of maxillary central incisor to mesiobuccal cusp tips of maxillary second molars had the smallest included angle with the HIP plane (2.61 +/- 0.81 degrees). The incisal edge of maxillary right central incisal to mesiopalatal cusp tips of maxillary first molars had the largest included angle with the HIP plane (7.72 +/- 1.60 degrees). The curve is drawn through the buccal cusp tips of maxillary teeth had better parallelism with the HIP plane.     

Anterior open bite--cephalometric evaluation of the dental pattern

The purpose of this study was to compare the dental pattern of patients with anterior open bite malocclusion to that of individuals with normal overbite by utilization of lateral cephalograms, panoramic radiographs and study casts. The findings showed that there was no significant difference in the inclination of the occlusal plane (SN.PlO) and position of the maxillary and mandibular incisors (1-NA, 1-NB) between both groups of individuals; but the angles of inclination of the maxillary and mandibular incisors (1.1, 1.NA and 1.NB) differed statistically between patients with anterior open bite of the individuals that presented normal overbite, which suggests that the anterior open bite may be of dental origin.     

Validation of a vision-based, three-dimensional facial imaging system.

OBJECTIVE: The aim of this study was to assess the accuracy of a newly developed three-dimensional (3D) imaging system in recording facial morphology. METHODS: Twenty-one infants with cleft lip each had a full-face alginate impression taken at the time of primary lip repair, and a stone cast was constructed from each impression. Five anthropometric points were marked on each cast. Each cast was digitized, and the 3D co-ordinates of the five points were obtained using a co-ordinate measuring machine (CMM, Ferranti) of documented accuracy (9.53 microm). Each cast was scanned in four positions using a computerized stereophotogrammetry (C3D) system. The five points were located on the 3D images, and their 3D co-ordinates were extracted by three operators. The co-ordinate systems produced by C3D were aligned, via translation and rotation, to match the CMM co-ordinate system using partial ordinary procrustes analysis. The displacements of the adjusted C3D co-ordinates from the reference co-ordinates were then measured. Three different types of errors were identified: operator, system, and registration errors. RESULTS: Operator error was within 0.2 mm of the true co-ordinates of the landmarks. C3D was accurate within 0.4 mm. The average displacement of points over the 21 casts at four positions for the three operators was 0.79 mm (median 0.68). CONCLUSIONS: The presented 3D imaging system is reliable in recording facial deformity and could be utilized in recording cleft deformities and measuring the changes following surgery     

Mandibular distraction osteogenesis and maxillary osteotomy in a class II division 1 patient with chronic juvenile arthritis

A patient with juvenile chronic arthritis presented with a malocclusion characterized by mandibular hypoplasia, symphysial deficiency, and an increased mandibular occlusal plane angle. Correction of the mandibular defect required both the horizontal advancement of the mandible and a counterclockwise rotation of the proximal segment to reduce the mandibular occlusal plane angle. This was achieved by a combination of distraction osteogenesis to horizontally advance the mandible (14 mm), followed by manipulation of the postdistraction regenerate to reduce the mandibular occlusal plane and increase the symphysial projection. The counterclockwise rotation of the mandibular body resulted in the creation of a posterior open bite. After a three-month period to allow consolidation of the mandibular distraction osteogenesis, secondary maxillary surgery at the Le Fort 1 level was performed to reestablish maxillary occlusal contact at the new mandibular occlusal plane. A genioplasty was also performed to improve chin projection.     

Articulator-related registration--a simple concept for minimizing eccentric occlusal errors in the articulator

PURPOSE: The purpose of this study was to develop an easy-to-use procedure for individual registration and to test its accuracy. Unlike common principles, the method should be based on a transfer of the articulator geometry to the patient. MATERIALS AND METHODS: The system consists of an articulator holding a bite plate in a standard position. The bite plate connects to an electronic recording system, which transfers the articulator's condylar points virtually to the patient's mandible by a centric relation record. The trajectories of the transferred points are recorded during mandibular protrusions and laterotrusions. From the trajectories, sagittal condylar and Bennett angles are measured and are adjusted at the articulator after mounting of the casts via the bite plate. Using a mechanical testing device, the accuracy of the measured angles was examined by comparison with preset values varying from 10 to 60 degrees (condylar angle) and from 0 to 40 degrees (Bennett angle) in 10-degree increments. RESULTS: The mean deviations of measured condylar angles from preset values ranged between 1.5 and 0 degrees. The mean deviations of the Bennett angles ranged from -0.5 to -1.3 degrees. CONCLUSION: The transfer of articulator geometry to the patient reduces the number of individual parameters necessary to imitate jaw motion to the condylar and Bennett angles. This leads to a significant simplification in registration and cast transfer. Since the required parameters are recorded with high accuracy, the method could be an alternative to traditional sophisticated instrumental registration.     

Altered jaw posture and occlusal disruption patterns following mandibular advancement therapy for sleep apnea: a preliminary study of cephalometric predictors

PURPOSE: Reports of irreversible alteration in jaw posture and destructive occlusal contact relationships in individuals using mandibular advancement devices for obstructive sleep apnea are beginning to appear. This study sought cephalometric means of identifying such individuals before commencing therapy. MATERIALS AND METHODS: Cephalograms of 34 obstructive sleep apnea sufferers who had worn mandibular advancement devices for 2 years were compared retrospectively with baseline films taken at commencement of therapy and analyzed for signs of morphologic changes in jaw position and occlusal relationship. In affected patients, two distinct morphologic species of mandibular reposturing became evident: (1) bilateral posterior open bite with destructive incisal attrition; and (2) less destructive intermediate open bite over the premolar and first molar regions. From the observed morphology patterns, gonial angle and maxillary-mandibular plane angle were analyzed as possible vertical cephalometric risk predictors, with newly defined pterygoid advancement proportion (PtAP) as a horizontal predictor. RESULTS: Three patients displayed the posterior open bite pattern and had gonial angles < or = 119 degrees and maxillary-mandibular plane angles < or = 16 degrees, with PtAP values > or = 0.48. Prediction intervals for the five intermediate open bite cases were 118 degrees < or = gonial angle < or = 128 degrees, and 23 degrees < or = maxillary-mandibular plane angle < or = 32 degrees. PtAP values were > or = 0.52. CONCLUSION: Cephalometric analysis can help practitioners identify which apnea patients might be likely to develop irreversible mandibular postural changes from wearing a jaw-repositioning device.     

Importance of occlusal plane reproduction on the semi-adjustable articulator in planning maxillary impactions for orthognathic surgery

Introduction

The aim of this study was to evaluate whether a 6° counterclockwise change in occlusal plane inclination would produce significant modifications on the final result of a maxillary impaction and mandible advancement model surgery.

Materials and methods

Four groups were used in this study, with ten identical maxillary casts and one mandibular cast mounted on the same semi-adjustable articulator, with the same malocclusion. The occlusal plane of the two control and study groups had an inclination of 13° and 7°, respectively. Preoperative and postoperative measures were performed using the Erickson platform and impactions of 6 and 10 mm were tested. To control these movements during model surgery, two splints were fabricated using another two maxillary and mandibular casts mounted with occlusal plane of 13°, simulating the proposed movement.

Results

The results were compared using the t test. Only the antero-posterior movement of the upper incisor was statistically significant for both study groups (p?<?0.05), with a mean of 0.48 and 0.94 mm in the 10 and 6 mm impaction groups, respectively.

Discussion

This information means that if an error in the occlusal plane transference occur, it will not be clinically significant, because differences smaller than 1 mm does not have influence on soft and hard tissue final result.     

骨性Ⅱ类高角型开[牙合]拔除上颌第一前磨牙及下颌第二磨牙矫治的临床研究

目的用回顾分析方法,评价拔除上颌第一前磨牙及下颌第二磨牙矫治骨性Ⅱ类高角型开[牙合]的临床疗效。方法选取12例骨性Ⅱ类开[牙合]病例,男4例,女8例,平均年龄15.6岁,拔除上颌第一前磨牙及下颌第二磨牙后,使用直丝弓矫治技术对其进行矫正治疗。治疗前后拍摄X线头颅侧位片,并对其进行头影测量分析。结果矫正治疗结束后,12例患者均取得了满意的治疗效果,侧貌明显改善,覆[牙合]覆盖正常,[牙合]平面发生逆时针旋转,下颌平面角变小。结论拔除上颌第一前磨牙及下颌第二磨牙矫治骨性Ⅱ类开[牙合]临床疗效可靠,效果较稳定。     

Computer-assisted morphological analysis of dental casts with maxillary prognathism and reversed occlusion

The morphologic characteristics of the dentition with maxillary prognathism and reversed occlusion were examined by a computer-assisted dental cast analysing system. Dental casts with normal occlusion, maxillary prognathism and reversed occlusion were selected and measured by a 3D shape measuring system. The dental arches and anteroposterior occlusal curves were approximated numerically by the polynomial expression with a fourth order and second order coefficients, respectively. The coefficients were analysed statistically. Maxillary dental arches with mandibular prognathism showed a more acuminate shape (V-shape) with a significant larger second order coefficient, while arches with reversed occlusion showed more angulate shapes (U-shape) with significantly smaller second order coefficients compared with arches with normal occlusions. However, a notable difference in the shape of the mandibular dental arches was not observed. The mandibular dental arches with maxillary prognathism were positioned backward relative to maxillary dental arches, while the arches with reversed occlusion were positioned forward. The anteroposterior occlusal curves with maxillary prognathism showed larger curvatures in maxilla and mandible, while the curves with reversed occlusion showed smaller curvatures in mandible comparing with the curves with normal occlusion. These results suggest that the present method could offer a useful and objective examination technique for the diagnosis of malocclusion.     

Maxillomandibular relationship in TMD patients before and after short-term flat plane bite plate therapy

This study assessed the maxillomandibular relationship in temporomandibular disorders (TMD) patients, before and after short-term, flat plane bite plate therapy. It was of interest to determine the incidence and degree of mandibular deviation in a group of TMD patients and whether the mandible would shift to the midline and consequently affect reported symptoms. Seventeen female and three male subjects (age range 19-60) were included in the study. Thirteen subjects were diagnosed with myofascial pain while seven were diagnosed as exhibiting disk displacement with reduction (Research Diagnostic Criteria). After taking impressions for these subjects, casts were fabricated and mounted. Maxillomandibular relationship was evaluated by the Denar Centric Check system (Anaheim, CA). The maxillary and mandibular labial frena were used as a reference to evaluate mandibular shift. Symptom questionnaires were used to assess temporomandibular joint pain and clicking. All subjects exhibited deviation (12 subjects to the right and 8 subjects to the left) prior to bite plate therapy. After flat plane bite plate therapy, the mandibular position of all subjects shifted toward the labial frenum midline position. Based on the Binomial test, the shift was significant (p < 0.001). Measurements on the Centric Check system showed a significant movement of both condyles in the anterio-posterior plane as well as the vertical plane. There was also significant reduction in TMJ pain and clicking (p < 0.01). The results support the hypothesis that the balanced position of the mandible is with frena aligned. When occlusal obstructions are eliminated, the mandible will drift to this position.     

基于口内扫描的三维数字化牙列模型咬合匹配评价分析

目的    通过评价咬合接触面积及咬合接触点的分布,分析3个品牌口内扫描仪扫描牙列模型颊侧部分获取数字化咬合记录的可靠性。方法    使用3个品牌口内扫描仪（TRIOS、CS3600、CEREC Omnicam）分别扫描10副上下颌牙列模型后,通过扫描颊侧部分获得具有牙尖交错位三维空间位置关系的上下颌牙列数字化模型,以口外扫描仓获得的数字化模型为对照组,应用逆向工程软件的偏差分析功能显示下颌牙列模型上的咬合接触图像,测量上下颌间的咬合接触面积、咬合接触点的分布,并运用SAS统计学软件比较3个品牌口内扫描仪的咬合关系精确度。结果　全牙列咬合接触面积：TRIOS组为（15.160 ± 8.145）mm2,CEREC组为（13.153 ± 5.080）mm2,CS3600组为（27.509 ± 20.847）mm2,对照组为（23.194 ± 18.194）mm2;3个口内扫描仪组分别与对照组比较,差异均无统计学意义（P > 0.05）;CS3600组分别与TRIOS组和CEREC组比较,差异均有统计学意义（均P < 0.05）;而TRIOS组与CEREC组之间的差异无统计学意义（P > 0.05）。咬合接触面积分布统计图显示,3个品牌口内扫描仪所得的面积分布趋势基本相同,咬合接触面积磨牙区＞前磨牙区＞前牙区。咬合接触点分布统计图显示,3个品牌口内扫描仪全牙列咬合接触点分布呈左右对称,接触点数少于对照组;位于中央窝和边缘嵴处的接触点在口内扫描仪与对照组之间出现的重复率较高。结论    3个品牌口内扫描仪通过颊侧扫描记录上下颌位置关系,得到数字化咬合记录。在全牙列咬合接触面积方面,3个口内扫描仪均与口外扫描仓无明显差异;咬合接触面积的主要差异在于磨牙区,TRIOS和CEREC Omnicam 相比CS3600的磨牙区咬合接触面积更接近口外扫描仓。咬合接触点位于中央窝和边缘嵴处记录的准确性要高于颊舌尖斜面。     

Application of occlusal splint for the patient with temporomandibular joint dysfunction. An application of silane coupling treatment: a case report

The bite plane therapy has been one of the most useful treatment methods for patients with temporomandibular joint (TMJ) dysfunction. But the bite plane usually causes esthetic and articulation disturbances and it is occasionally difficult to use during mastication. The authors have fabricated a new type of bite plane, named occlusal splints, which covers each side of the premolars and molars. The occlusal splint was constructed by a hard-resin for the occlusal part and cast clasps for the retentive part and these parts were adhered after a pre-treatment of metal by the use of a silane coupling agent (Silicoater system). The patient was a 35 year-old man, with a chief complaint of left side reciprocal TMJ clicking. The anterior repositioning type of bite plane was applied for the treatment with the diagnosis of anterior disk displacement with reduction. But he complained of esthetic and articulation disturbances especially during working and eating. After four months we fabricated an occlusal splint that can be used for a long period of time. The patient was satisfied to use this occlusal splint and no symptoms of TMJ dysfunction were found with this appliance. It is suggested that the occlusal splint consisting of a hard-resin and cast clasps is a useful appliance especially for the purpose of use during working and eating, and for evaluating the properness of mandibular position.     

Accuracy of three-dimensional dental resin models created by fused deposition modeling,stereolithography, and Polyjet prototype technologies: A comparative study

Objectives: The aim of this study was to assess the dimensional accuracy of fused deposition modeling (FDM)–, Polyjet-, and stereolithography (SLA)–produced models by comparing them to traditional plaster casts.Materials andMethods: A total of 12 maxillary and mandibular posttreatment orthodontic plaster casts were selected from the archives of the Orthodontic Department at the Indiana University School of Dentistry. Plaster models were scanned, saved as stereolithography files, and printed as physical models using three different three-dimensional (3D) printers: Makerbot Replicator (FDM), 3D Systems SLA 6000 (SLA), and Objet Eden500V (Polyjet). A digital caliper was used to obtain measurements on the original plaster models as well as on the printed resin models.Results: Comparison between the 3D printed models and the plaster casts showed no statistically significant differences in most of the parameters. However, FDM was significantly higher on average than were plaster casts in maxillary left mixed plane (MxL-MP) and mandibular intermolar width (Md-IMW). Polyjet was significantly higher on average than were plaster casts in maxillary intercanine width (Mx-ICW), mandibular intercanine width (Md-ICW), and mandibular left mixed plane (MdL-MP). Polyjet was significantly lower on average than were plaster casts in maxillary right vertical plane (MxR-vertical), maxillary left vertical plane (MxL-vertical), mandibular right anteroposterior plane (MdR-AP), mandibular right vertical plane (MdR-vertical), and mandibular left vertical plane (MdL-vertical). SLA was significantly higher on average than were plaster casts in MxL-MP, Md-ICW, and overbite. SLA was significantly lower on average than were plaster casts in MdR-vertical and MdL-vertical.Conclusions: Dental models reconstructed by FDM technology had the fewest dimensional measurement differences compared to plaster models.     

3D morphological measurements of dental casts with occlusal relationship using microfocus X-ray CT

In the diagnosis of dental occlusion, it is necessary to quantitatively measure interocclusal contacts and transfer them to a computer model. In this aspect, three-dimensional computer models of upper and lower dental casts play a significant role. In this study, we proposed a new method to measure occlusal interaction by using a microfocus X-ray CT technique. Measurement accuracy was determined as +/-0.03 mm in comparison with a coordinate measuring machine. A superimposition procedure for two sets of three-dimensional dental cast models was also established. Using the same dental cast, the standard deviation between the two sets of models was +/-0.015 mm - which was defined as measurement precision. Between an optical laser scanner and the microfocus X-ray CT system, the standard deviation measured between the two models was +/-0.05 mm. Data were acquired when upper and lower dental casts mounted on the bite impression were scanned, and then occlusal interaction, contacts, and distance distribution between the casts were visualized by a colored map on the cast models. Within the limitations of the current study, it was successfully demonstrated that microfocus Xray CT was well poised for quantitative measurement of occlusal interaction.     

3D morphological assessment of occlusal treatment by measuring dental casts with a micro-focus X-ray CT

Summary  The analysis of occlusal relationship is important for the success of dental treatment. Three-dimensional (3D) computer models of upper and lower dental casts can play a significant role. In this study, we proposed and applied a new method in actual clinical assessment to measure dental casts with occlusal relationship by using a micro-focus X-ray CT system. We examined the modelling accuracy by comparing multiple 3D images taken by shifting the dental cast position. Modelling accuracy was confirmed as 0·03 mm. One occlusal treatment in clinical practice was selected as a case example. The dental casts and bite impression, taken before treatment, were scanned and the occlusal contacts and distance distribution between the upper and lower casts were visualized by a coloured map and overlaid on the computer models. Distances between the upper and lower casts of selected points were compared before and after the treatment. Initially, the subject had early contact on the anterior teeth, where distance was measured as 0·04 mm, and only one area measured less than 0·15 mm. After treatment, five areas measured less than 0·15 mm. Also, by comparing the dental cast models taken before and after occlusal adjustment of the tooth, the position and amount of adjustment were visualized. We successfully demonstrated the quantitative clinical assessment of occlusal treatment.     

Inclination of the occlusal plane is associated with the direction of the masticatory movement path

Using lateral cephalograms and a jaw movement-recording system, the relationship between the masticatory movement path and dentofacial morphology was investigated in 17 subjects (9 males and 8 females, mean age 23.5 years) without a history of orthodontic treatment. The masticatory movement path was measured at the right and left lower first molar while the subjects chewed gum. The angle between the Frankfort horizontal plane and the masticatory axis (FH-masticatory angle), defined as the axis passing the opening and closing turning point on the sagittal masticatory path, was also measured. The correlation between the angular measurements derived from the lateral cephalogram and the FH-masticatory angle was then investigated. A positive correlation was observed in the FH-masticatory, occlusal plane (P < 0.05), and mandibular plane (P < 0.01) angles. Furthermore, it was found that the angle between the masticatory axis and the occlusal plane (69.1 +/- 4.2 degrees) remained constant even as the masticatory axis showed a tendency to incline forward as the mandibular plane angle became steeper; the rates of change of the FH-masticatory and the occlusal plane angles were approximately 1:1. This finding suggests that the masticatory movement path is closely associated with the occlusal plane.     

Treatment of occlusal plane canting using miniscrew anchorage

Two patient therapies introduce the use of miniscrew anchorage in adult patients for the correction of mild to moderate occlusal plane canting without severe facial asymmetries. A miniscrew implanted in the infrazygomatic buttress was used as anchorage for intruding the overerupted maxillary quadrant. As unilateral intrusion of maxillary posterior teeth will develop a posterior unilateral open bite, box elastics were subsequently used to extrude the opposing teeth in the mandibular arch. These treatments show that miniscrew anchorage offers a simple, efficient method of correcting occlusal plane canting and mild facial asymmetries.     

Angle between occlusal plane and horizontal plane of articulators with quick mounting face bow

Correct determination of the occlusal plane is important for estetic, phonetic and masticatory function of the denture. As many different criterias are used in clinical practice to determine the occlusal plane on the wax rims, the aim of this study was to find the angle between the occlusal plane and the horizontal plane in the articulators with the quick mounting face bow. The measurements were made on the casts of 30 eugnath individuals with at least 28 natural teeth, mounted in S.A.M. articulator through the transfer with the Quick mounting face bow, in the position of maximum intercuspation. Measurements were made with a precise caliper and were transferred to the calibrated paper. The angles were measured between the occlusal plane and the horizontal plane. The angle is 9.42 degrees +/- 4.1 degrees in the population of this country. This result can be helpful to determine the occlusal plane or to control if the occlusal plane, determined by the other methods is in the correct position in articulator.     

Cephalometric and clinical diagnoses of open bite tendency

Pretreatment lateral cephalometric radiographs of patients between 10 and 16 years of age were searched for persons who met criteria commonly used for identifying patients with "open bite tendencies." Results indicate that different measures of open bite tendency identify different patients. Of 50 patients with sella-nasion-mandibular plane angles greater than 40 degrees, only 11 had upper facial height/lower facial height ratios less than 0.70; of 50 patients who had occlusal plane-mandibular plane angles greater than 22 degrees, only 15 had posterior facial height/anterior facial height ratios of less than 0.58. Of the 250 patients who exhibited some well-accepted cephalometric indication for excessive vertical dimension, only 13% had actual anterior open bites. When clinicians ranked their own patients according to the difficulty in controlling excessive vertical growth during treatment, measurements such as the mandibular plane angle, upper to lower facial height ratio, and anterior to posterior facial height ratio did not predict treatment responses.