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.

Guided and unguided mandibular reference positions in asymptomatic individuals.

OBJECTIVES: To determine the difference between guided and unguided mandibular reference positions assessed by articulator simulation. SETTING AND SAMPLE POPULATION: This study was carried out at the Division of Orthodontics at Vienna Medical University. The sample population consisted of 19 men and 18 women aged 23-32 years and without temporomandibular disorder. MATERIALS AND METHODS: Three examiners used bimanual operator guidance and unguided mandibular stationary hinging at final jaw closure before occlusal contact and made occlusal wax recordings. The examiners repeated both techniques after 8 and 17 days on the same subjects. Condylar positions were assessed using articulator-mounted casts and a three-dimensional electronic condylar position indicator. RESULTS: Bimanual guidance positioned the condylar spheres, on average, 0.1 mm more right and 0.6 mm more posterior and superior to unguided hinging (p < 0.04). The repeatability of bimanual guidance by three operators and on 3 days resulted in inter-repetition standard deviations ranging from 0.19 to 0.4 mm and from 0.41 to 0.76 mm for unguided hinging. The highest fraction of the total variance came from the individuals, followed by days, then intra-operator and interoperator variability. Both methods showed considerable overlap of condylar sphere positions at the 95% confidence level. CONCLUSION: Within the limits of an articulator study, the spatial variability of condylar sphere positions suggested a statistically but not clinically relevant methodological difference between bimanual guidance and unguided stationary hinging.

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.

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.

Multidimensional osteodistraction for correction of implant malposition in edentulous segments.

This study examined multidimensional osteodistraction as a treatment method for correction of implant malposition and as an alternative to augmentation procedures. The prosthetically unfavourable implant positions were due to growth-related implant malposition (in the context of treatment of young patients with oligodontia) or primary bone-driven implant insertions. The radiographical and clinical findings obtained with this osteodistraction technique are presented and discussed. A tooth-supported osteodistractor for multidimensional distraction with custom-fabricated distraction abutments was used for treatment of 8 patients with a total of 9 maxillary and mandibular edentulous segments including single-tooth gaps. All patients underwent an osteotomy at a minimum distance of 1 mm from the implant surface. Following primary wound healing, distraction was carried out by 1 mm in vertical direction and 0.5 mm in the demanded transverse direction daily until the prosthetically optimized position was achieved. During and after the 12-week retention phase, the patients were evaluated clinically and radiographically. Multidimensional osteodistraction was carried out successfully in all 8 patients. The distraction distances were 3 to 11 mm in vertical direction and a maximum of 5 mm in buccolingual/buccopalatal direction. The malpositioned implants were brought into a prosthetically optimized position in all cases. The results of this study show that this multidimensional osteodistraction technique allows both augmentation of edentulous segments with a clearly compromised implant host site and correction of unfavourable implant positions.

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.

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.

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.

Implant-surgical and prosthetic rehabilitation of patients with multiple dental aplasia: a clinical report.

The expanded experience with oral implants and supplementary augmentation techniques has opened new possibilities for treating patients with oligodontia or anodontia with fixed prostheses. A problem in treating such patients is the need to place implants in growing maxillae or mandibles, as many of these patients are children or adolescents. When implant treatment is postponed until the patient is full grown, dysfunctions become manifest, which necessitates extensive surgical measures to achieve a fixed prosthetic restoration. This report illustrates the problems associated with different concepts for the treatment of multiple aplasia with implants. The results are based on the findings of 22 patients with oligodontia who underwent surgical treatment and were followed over a period of 5 years. Two controversially treated cases are presented.

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.

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.

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.

Mandibular reference position: chin-point guided closure vs. final deglutition.

The study investigated two mandibular positions based upon computerized axiography recordings of hinge axis movements of 262 subjects. Next to the well-known guided closure position RP (reference position by chin-point guidance), the position of final deglutition (FD) was quantified. FD represented the hinge axis position at the end of the swallowing movement. The results elicited average linear distances of 0.32 +/- 0.43 mm on the right and 0.33 +/- 0.40 mm on the left side between both positions in the sagittal plane. The average distance in the frontal plane was 0.02 mm (right) and 0.04 mm (left). Approximately 46 per cent of FD recordings were found anterior and inferior to RP, and showed significant difference to posterior and anterior-superior FD recordings. The replicability of both positions was tested on 53 subjects and averaged 0.04 mm (FD) and 0.09 mm (RP). Average deviations of repeated recordings within the subject ranged from 0.07 to 0.47 mm (FD) and 0.07 to 0.57 mm (RP) for each spatial direction. The results of this study showed a relative coincidence of an average FD and RP Variation of FD in anterior inferior direction questioned the clinical reliability of FD to reassure the guided closure position.

An analysis of hinge axis translation and rotation during opening and closing in dentulous and edentulous subjects.

In order to evaluate the influence of interocclusal environment, condylar movement was investigated by computerized axiography. The sample consisted of 50 dentulous and 50 edentulous Caucasians. The mean length of translation at maximum opening in dentulous subjects was 16 mm, while edentulous subjects showed an average of 11 mm. The mean angle of hinge axis rotation at maximum opening was 30 degrees in dentulous subjects and 17 degrees in edentulous subjects. The mean length of translation and the rotation of hinge axis in opening and closing movements was smaller in edentulous subjects than in dentulous ones. In opening and closing movement of edentulous subjects, the length of translation and the rotation value revealed no significant correlation with age or duration of upper and lower prosthesis. No significant difference was shown between edentulous and dentulous subjects on translative quantity in protrusive movement.

Comparison of magnetic resonance tomography with computerized axiography in diagnosis of temporomandibular joint disorders.

This study compared the accuracy of two noninvasive methods, computerized axiography and magnetic resonance tomography (MRT), in diagnosing temporomandibular joint (TMJ) disorders. Forty-seven subjects underwent axiography and subsequent assessment of the TMJ by MRT. The statistical analysis referred to the correlations of the most relevant clinical diagnoses, i.e., no appreciable disease, disk displacement with reposition, disk displacement without reposition, morphologic alterations, and hypermobility of the condyle. In 70% of the disk-displacement-with-reposition and disk-displacement-without-reposition patient groups, axiography and MRT gave the same information. In other patient groups, the axiography findings agreed with the MRT findings in 45% of the cases. It was concluded that although a large percentage of morphologic alterations could be detected by MRT, axiography determined the dysfunctional dynamics more clearly.

The effect of occlusal splint therapy on different curve parameters of axiographic TMJ tracings.

Computerized axiography was used as an objective instrumental method of evaluating the response of patients with temporomandibular joint (TMJ) symptomatology to occlusal splint therapy. Diagnosis was performed in a standardized manner by systematically analyzing TMJ path tracings obtained by computerized axiography. Thirty-six patients were axiographed before and after therapy with full-arch occlusal stabilizing appliances, followed by assessing the effect of therapy on various path curve parameters. The data obtained for the patient group treated with splints was compared to that of six patients also axiographed, but left untreated for a period of six weeks before a second TMJ tracing was obtained. The results show that splints have a certain effect on reciprocal TMJ clicking (response rate 67%). Retral stability and path characteristics are also substantially improved (response rates 44% and 40%). Less influence was noted on hypomobile joint paths (response rate 29%), the quality of movements (response rate 28%) and Bennett angle values (response rate 23%). Patients with disk displacements without reduction were not treated with splints, they underwent surgery. Their results will be reported later. By contrast, TMJ tracings in the control group remained essentially unchanged.

Orthopedic jaw movement observations. Part V: Transversal condylar shift in protrusive and retrusive movement.

Unguided protrusive and retrusive mandibular movement was investigated in 76 asymptomatic volunteers and temporomandibular joint (TMJ) patients using computerized axiography. In 38 of these subjects, guided pro-/retrusion was also recorded. Measurements were performed in a three-dimensional Cartesian coordinate system (x = anteroposterior; y = transversal, toward the hinge axis; z = craniocaudal). Transversal shift (y) was measured and evaluated as well as the distance "s" and horizontal condylar inclination (HCl) at the point of maximum transversal deviation. The patterns of the tracings were analyzed with a view to diagnostic improvements. The objective of this study was to evaluate transversal shift and to examine the postulate of symmetrical behavior of the TMJs in pro-/retrusion. The mean mandibular shift was 0.15 mm to the left. This maximum deviation was seen in a mean distance "s" of 7.42 mm in relation to the Cartesian coordinate system in reference position. These results suggest a functional dominance of the right part of the mandible in protrusive and retrusive movement.

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.

Orthopedic jaw movement observations. Part III: The quantitation of mediotrusion.

The objective of this series is to observe and analyze movements of the temporomandibular joint (TMJ). With the information from these studies, orthopedic standards for jaw movements will be established in further investigations according to the neutral-zero method used in general orthopedics. Any restricted range of motion can thus be defined as a deviation from these standards. Direct interpretation and objective evaluation of joint functions has major practical implications. With the aid of computerized axiography, mediotrusive movements of 48 asymptomatic volunteers and 66 jaw patients were evaluated. The movements performed were either free or guided. The mean curve lengths, as well as the Bennett angles at 3 mm and at the end point were recorded. An average group was defined, containing the values of 50% of all volunteers. The interquartile range was calculated for lengths of mediotrusive movements as well as for Bennett angles. The average range of free mediotrusive movement for female volunteers was 11.06-11.98 mm (mean 11.55 mm) on the right side and 10.47-11.75 mm (mean 11.24 mm) on the left side. Male volunteers showed an average range of 10.23-11.54 mm (mean 11.1 mm) on the right side and 10.24-11.73 mm (mean 11.12 mm) on the left side. The values for female patients amounted to 9.95-1.66 mm (mean 10.8 mm) on the right side and 9.75-11.28 mm (mean 10.55 mm) on the left side. The average range for male patients was 9.06-9.71 mm (mean 9.54 mm) on the right side and 9.17-10.23 mm (mean 9.73 mm) on the left side. The average range for Bennett angles at maximum excursion in free mediotrusive movement was between 0.41 and 5.89 degrees (mean 4.43 degrees) in the volunteers on the right side and between 2.45 and 10.07 degrees (mean 6.87 degrees), respectively, on the left side. The values for patients amounted to 0.19-12.65 degrees (mean 6.93 degrees), on the right side and 1.71-14.15 degrees (mean 6.73 degrees) on the left side.

Orthopedic jaw movement observations. Part I: Determination and analysis of the length of protrusion.

An analysis and quantitation of protrusive and retrusive mandibular movement is provided. This report is one study along with four other parts analyzing the mandibular opening movement, the transversal shift during protrusion and retrusion, the mediotrusive movement and mastication. Protrusive movements of 225 individuals (180 patients, 45 volunteers) were analyzed using computerized axiography. Investigating both asymptomatic volunteers and patients with abnormal joint mobility helps to improve evaluation of these abnormalities. With the aid of diagnostic computer software, the length of the pathways was measured and the characteristics of the curves were analyzed. An average group was defined based on the values found in asymptomatic individuals, comprising 50% of our volunteers. The interquartile range for the male volunteers was 8.79-12.27 mm for the right joint and 9.43-12.93 mm for the left joint; for female volunteers it was 8.32-10.64 mm and 9.2-11.26 mm, respectively.