Geometric morphometric evaluations of a randomized prospective split-mouth study on modes of ligation and reverse-curve mechanics.

OBJECTIVES: To evaluate tooth position after six and 9 months of orthodontics with conventional brackets on one side of the dentition and ligature-less brackets on the other. SETTING AND SAMPLE POPULATION: Orthodontic Division, Vienna Medical University. Twenty patients aged 22.5 ± 5.7 years, symmetrical malocclusion and arch form, no premolar extraction. MATERIAL AND METHODS: Prospective split-mouth study, 0.022-inch SmartClip self-ligating brackets assigned randomly to the left or right dentition, conventional 0.018-inch brackets on the other side. 52 dental landmarks, digitized on plaster casts, represented dental arches at baseline (t0), 6 months and 9 months (t1, t2). During t0-t1, we used 0.016 and 0.014 x 0.025 inch superelastic wires, during t1-t2 connected reverse-curve hemiarch wires: 0.017 x 0.025 inch ß-titanium on the ligature-less side, and 0.016 x 0.022 inch Elgiloy multiloop wires on conventional brackets. Morphometric analyses were used to assess differences in dental arch shapes. RESULTS: Neither initial alignment nor the reverse-curve phase showed statistically significant differences between ligature-less and conventional brackets in moving teeth. CONCLUSION: Morphometric shape analyses corroborated current evidence that self-ligating brackets were no more effective than conventional brackets with steel ligatures after 6-month initial alignment. From months 6-9 treatment with ß-titanium reverse-curve wires on 0.022-inch ligature-less brackets resulted in similar tooth positions as accomplished by Elgiloy multiloop wires on 0.018-inch steel-ligature-tied brackets.

The reproducibility of condylar hinge axis positions in patients, by different operators, using the electronic mandibular position indicator.

Three operators each made five recordings from 15 symptomatic patients using the electronic mandibular position indicator. The method consisted of measuring bilateral spatial changes of the hinge axis recalculated by the computer to an intercondylar distance of 110 mm and a third position, calculated from the rotation of the hinge axis, at the incisal guidance table. All individual patient recordings were related to the origin of the same coordinate system. This origin is designated and defined as the reference position, with purposeful elimination of any stated joint position for this definition. The measurements were in all planes of space at 10-millimicron increments, including the rotation of the transverse hinge axis in hundredths of degrees. These data showed that the reproducibility of hinge axis positions, ie, reference positions, to hinge axis condylar positions dictated by the maximum intercuspation of teeth was in average less than 0.2 mm for each record from all operators and patients.

Computerized axiography: principles and methods.

This paper reviews earlier methods for the analysis of mandibular movement and gives a detailed account of state-of-the-art procedures. Special emphasis is given to computerized axiography and the application of this method to the diagnostics of the temporomandibular joint (TMJ). The article discusses the advantages of computerized axiography over the mechanical device and points out the limitations of the axiographic method. One major advantage of the computerized system is having the enlarged diagram of tracings on the computer screen. This means that small changes such as initial disk displacements can be diagnosed more readily than with the mechanical device.

Cephalometric differentiation between vertical and horizontal malocclusions in 122 Europeans using the Denture Frame Analysis and standard measurements. Differentiation between vertical and horizontal malocclusion.

This study evaluated the ability of some cephalometric measurements to differentiate between horizontal and vertical malocclusions and normal occlusion. Based upon the Angle classification and the vertical incisor overbite, 122 randomly selected subjects were assigned to 3 horizontal and 3 vertical groups: neutrocclusion, distocclusion, mesiocclusion as well as open bite, normal overbite, and deep bite. Evaluation of the lateral cephalograms was based on Denture Frame Analysis and cephalometric standard measurements (SNA, SNB, ANB, Wits appraisal, Björk polygon, overbite depth indicator, incisor inclination, incisor protrusion, facial height ratio). The statistical evaluation assessed the ability of the measurements to show significant differences between the individual horizontal and vertical groups. Using Denture Frame Analysis, all vertical groups could be differentiated by the occlusomandibular angle (OP-MP) and all horizontal groups by the angle between the A-B plane and the mandibular plane as well as by the inclination of the upper incisors to the A-B plane with statistical significance (p < 0.05). Among the standard measurements, the Wits appraisal was the only one to show differences between all horizontal groups with statistical significance. None of the standard measurements could fully differentiate the vertical groups. The above measurements from the Denture Frame Analysis distinguished the types of malocclusion in anteroposterior and vertical direction including significant distinction between the neutrocclusion group and the malocclusion groups. Therefore a cephalometric classification was feasible in terms of hyper- and hypodivergence as well as of a mesial or distal dentofacial relationship.

Accuracy of recording horizontal condylar inclination and Bennett angle with the Cadiax compact.

This study assessed the accuracy of an electronic hinge axis tracing device (Cadiax compact) in measuring the horizontal condylar inclination (HCI) and the Bennett angle. The hinge axis movements were simulated with an articulator to which the hinge axis tracer was attached. On the articulator the pre-set HCI values were 20 degrees, 40 degrees and 60 degrees, the pre-set Bennett angles were 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees. The maximum measuring errors ranged from 0 to 3.4 degrees (in average 1.2 degrees ) and yielded statistically significant differences between articulator setting and Cadiax compact measurement (P < 0.05) except the HCI of 40 degrees and the Bennett angle of 0 degrees. Because of the small range of the maximum measuring error the Cadiax compact represented reasonable accuracy for clinical application in anterior guidance restorations.

Overbite depth and anteroposterior dysplasia indicators: the relationship between occlusal and skeletal patterns using the receiver operating characteristic (ROC) analysis.

This study was carried out to investigate the validity of the overbite depth indicator (ODI) and the anteroposterior dysplasia indicator (APDI), based on the cephalometric analysis of 122 Caucasians selected at random for assessment of vertical and sagittal relationships. Considering the occlusion, the sample was divided into three classifications in the sagittal component: 36 cases of neutrocclusion, 54 cases of distocclusion, and 34 cases of mesiocclusion. The sample was also categorized according to the overbite relationship: 54 cases of normal overbite, 34 cases of open bite, and 34 cases of deep overbite. In the sagittal component analysis, the APDI measurement resulted in significant differences between the neutrocclusion, distocclusion, and mesiocclusion groups. In the vertical component analysis, the ODI significantly distinguished between the normal and deep overbite groups, and the open bite and deep overbite groups, but not between the normal overbite and the open bite groups. A receiver operating characteristic (ROC) analysis showed that the APDI matched the anteroposterior molar relationship in 88 per cent, and the ODI matched the amount of incisor overbite in 81 per cent.

Reproduction of excursive tooth contact in an articulator with computerized axiography data.

PURPOSE: This study assessed the reproduction of excursive tooth contacts with a SAM2 "P" articulator set up with the aid of computerized axiography. MATERIAL AND METHODS: Articulator excursive tooth contacts were compared with intraoral excursive contacts identified with occlusogram wax. The maxillary casts were mounted with a kinematic face-bow, and the mandibular cast was oriented to the intercuspal position. The articulator was set using information obtained from computerized axiography. Protrusion and laterotrusion to the left and right sides were examined. The first 4 mm of excursive tooth contacts in the occlusogram were compared with the 4 mm of excursive tooth contacts in the articulator. RESULTS: The articulator reproduced 82% of the teeth with protrusive tooth contacts and 90% of the teeth with laterotrusive tooth contacts. The exact locations of excursive tooth contacts were reproduced in 66% of protrusive contacts and 81% of laterotrusive contacts. The articulator also created additional eccentric dental contacts that were not originally present in the occlusogram. Twenty percent of the subjects showed these additional contacts during protrusion; in lateral movement of the articulator these additional contacts were present in 27% to the left side and 20% to the right. Clinically, these findings suggest that there are limits to the ability of the articulator to reproduce excursive tooth contacts. These limitations should be kept in mind when an articulator is used for diagnostic and restorative dental procedures.

Guided versus unguided mandibular movement for duplicating intraoral eccentric tooth contacts in the articulator.

STATEMENT OF PROBLEM: The extent to which intraoral excursive tooth contacts are duplicated correctly in the articulator is constantly being investigated. PURPOSE: This study evaluated whether data from unguided or guided hinge axis movement are superior in duplicating excursive tooth contacts. MATERIAL AND METHODS: Intraoral records of tooth contacts from intercuspal position to 4 mm protrusion and laterotrusion were obtained from 50 subjects by using occlusogram wax. These movements were simulated in a SAM2 "P" articulator using horizontal condylar inclination and Bennett angle from recorded guided and unguided mandibular movements. Occlusograms were compared with contacts generated by the articulator. RESULTS: On average, the articulator duplicated approximately 73% of intraoral protrusive and 81% of intraoral laterotrusive contacts for up to 4 mm of movement, using either data from unguided or guided movements. Both movements yielded identical means and no significant difference of duplicated contacts. However, individual differences scattered within approximately +/-32%. CONCLUSION: Exclusive recommendation of guided movement can be questioned for accurate imitation of dynamic tooth contacts. In addition to the type of movement, other factors must be detected to enhance articulator adjustment and workings.

Mandibular position at chin-point guided closure, intercuspation and final deglutition in asymptomatic and temporomandibular dysfunction subjects.

This study compared the mandibular position at chin-point guided jaw closure, intercuspation and final deglutition (position at the end of swallowing) in 159 asymptomatic subjects and 142 subjects with symptoms in the craniomandibular system. The symptomatic subjects were assigned to four groups showing an adapted centric posture, pain, luxation with reduction of the temporomandibular joint and pain with luxation and reduction. Computer equipment aided recording of hinge axis movements in three dimensions. While the three positions differed significantly in anterior-posterior direction on both sides and in inferior-superior direction on the right, a significant difference between asymptomatic and symptomatic subjects existed only in final deglutition on the left side and in the anterior-posterior location of the guided closure. Final deglutition did not coincide with the guided closure or the intercuspation in approximately 89%. A proportionally large standard deviation gave evidence against a strict relationship of the three positions in asymptomatic and symptomatic subjects. Because of this variability, final deglutition was not recommended for verification of centric relation or the intercuspal position.

Correlation between elevator muscle activity and direction of sagittal closing pathway during unilateral chewing.

The closing pathway of masticatory movement in the vicinity of the intercuspal position (ICP) is considered as a functional movement in reconstructing the occlusal guidance. The purpose of this study was to examine a correlation between elevator muscle activity and direction of the closing pathway in the vicinity of the ICP during mastication. Fifty subjects (18 male and 32 female subjects aged from 21 to 34 years) were selected randomly from the students of the Kanagawa Dental College. The measurements of jaw movement during mastication were recorded using a Sirognathograph instrument and surface electromyography (EMG) of the anterior temporalis and masseter muscles simultaneously. The muscle activity and the direction of the closing pathway were calculated on the working and non-working sides during unilateral chewing and analysed at the sections of ICP-2 mm and 2-4 mm in sagittal view. The direction of the closing pathway was expressed by the angle to a vertical reference axis. The direction of the closing pathway correlated significantly with the activity of the anterior temporalis muscles on the non-working side and the masseter muscles on the working side at ICP-2 mm. From the results of this study, it was suggested that the elevator muscle activity may be associated with the direction of the closing pathway during mastication.

The Denture Frame Analysis: an additional diagnostic tool.

The purpose of this study was to evaluate the Denture Frame Analysis. This adjunctive cephalometric analysis of the lateral headfilm was introduced in Japan, but no data exist for the Caucasian population at present. One-hundred-and-six Caucasians were randomly selected and assigned to one of four groups, according to their malocclusion: Angle Classes I, II, and III, and anterior open bite. Statistical testing showed significant differences among the four groups for most of the measurements investigated. The Denture Frame Analysis distinguished the different types of malocclusion, and evaluated skeletal and dental relationships. The occlusal plane aids in the determination of the objectives and limits of orthodontic therapy.