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.

Quantitation of transverse maxillary dimensions using computed tomography: a methodological and reproducibility study.

The present investigation was a methodological study of a new method of quantification of a series of factors in the transverse dimension of the maxilla including the nose, maxillary bones and dental arches, based on computer tomographic (CT) scanning. The aim was to investigate a series of parameters thought to be relevant in the differential diagnosis of discrepancies in the morphology of this area and probably affected by orthodontic appliances. Based on a standardized CT scanning registration of 10 subjects, a series of points on the scans were identified and then measured in a special cephalometric computer system (linear and angular values). The quantitation was repeated by each observer and inter- and intra-observer differences were calculated. The results demonstrated that virtually all the parameters showed a high degree of reproducibility at both levels and confirmed the statistical suitability of the method described. The method will be used in a series of ongoing studies regarding the morphology and treatment of discrepancies of the midface and therefore supplement the relatively sparse information based on quantitative reports concerning this important anatomical area.

An improved transpalatal bar design. Part I. Comparison of moments and forces delivered by two bar designs for symmetrical molar derotation.

Moments and forces delivered during symmetrical derotation of upper molars by 10 Goshgarian-type (GTPB) and 10 Zachrisson-type transpalatal bars (ZTPB) were measured in laboratory experiments using a computer-based strain gauge. The bar passivity in sagittal, transverse, and vertical planes was first assessed at the measurement apparatus. Then each end of the 20 passive bars was symmetrically activated by 10 mm in the sagittal plane using a template. The activated bars were placed into lingual attachments of the measuring apparatus, and three consecutive measurement steps were done for each bar. Measurements were made when the attachments were at 0 degrees, 5 degrees, and 10 degrees of deactivation. The mesiodistal (sagittal) forces, the horizontal forces, and the moments of rotation at the right and left attachments were measured at each step. The horizontal forces and the moments of rotation of the two designs had statistically significant differences. Greater moments of rotation were produced by the GTPB. The ZTPB produced significantly lower contractive horizontal forces than did the GTPB at 5 degrees and 10 degrees of deactivation.

An improved transpalatal bar design. Part II. Clinical upper molar derotation--case report.

Bilaterally rotated upper first molars (mesial in, distal out) were derotated in two different cases by using a custom-made transpalatal bar. The bars were reactivated, if necessary, at four-week controls. The derotations were fully corrected after about three months.

The efficacy of anterior repositioning splint therapy studied by magnetic resonance imaging.

Magnetic resonance images (MRIs) were obtained of 52 temporomandibular joints (TMJs) of 30 patients with TMJ disease, before insertion of an anterior repositioning splint. Ten TMJs showed a normal disc-condyle relationship. Pathological findings were partial or complete anterior disc displacement with disc reduction (n = 18), without (n = 7), or with partial reduction (n = 4) or non-reducing joints combined with osteoarthrosis (n = 13). Associated clinical findings were joint clicking, painful TMJ movements with or without condyle limitation, deviation, or crepitus. The clinical evaluation when compared with the MRIs correlated in 75 per cent of cases. Immediate post-insertion MRIs showed recapture of discs with a protrusive splint in 15 out of 18 reducing displacements. Recapture of the disc was seen in only two out of four joints with anterior disc displacement with partial disc reduction. There was no recapture in non-reducing joints. In severe cases of internal derangement with a wide range of disc displacement combined with changes of the osseous joint surfaces, the recapturing of the articular disc with an anterior repositioning appliance was unsuccessful (0 of 13). The follow-up for pain relief after one week showed a significant reduction of symptoms, despite the fact that recapture of the dislocated disc occurred in only 17 of the 42 pathological TMJs. The possibility for disc recapture depends on the disc-condyle position and configuration, the integrity of the posterior attachment, and the degree of degenerative changes of the intra-articular structures, such as osteophytosis, condylar erosion, or flattening of the articular disc. This diagnostic information influences the method of treatment of TMJ disorders. In non-reducing joints or in the later stages of internal derangement of the TMJ, it is not possible to achieve a normal disc-condyle relationship using protrusive splints.

Short epithetic implants for orthodontic anchorage in the paramedian region of the palate. A clinical study.

Orthodontic movement of teeth often requires maximum anchorage, so that additional resistance must be added to teeth to avoid reaction to reciprocal forces. Thus, use of endosseous implants may be a valuable alternative for ensuring stable intraoral anchorage. This study was designed to evaluate the efficacy of short epithetic implants for orthodontic anchorage in the paramedian region of the palate. Twenty-one patients (15 female, 6 male; mean age 25.8+/-9.9 yrs, min 12.7, max. 48.1) were included in this study. Following adequate preoperative planning, an implant system with reduced length, which had already been used for anchorage of epitheses, was placed in the paramedian region avoiding the anterior palatine suture. After a mean period of 4 months with unloaded healing, the implants were subjected to direct or indirect orthodontic loading. Despite varying bone quality and varying vertical bone volume in this region, adequate primary stability was achieved for all of the implants. No implant was lost during the healing period. Three out of the 21 implants placed were considered as failures. Two implants loosened shortly after the start of orthodontic loading. One of these was lost at a later stage due to peri-implant inflammation, while the other one was left in place during the 9-month follow-up period because no inflammation developed and this implant is still indirectly included in the orthodontic treatment. Another implant loosening was observed after 8.5 months following direct loading with 8 N. This implant was also lost due to peri-implant inflammation. The time-related survival probability was 84.8% after 22.9 months. As yet, 4 implants have been removed due to completion of orthodontic treatment. The results of this study indicate that short epithetic implants are suitable to achieve maximum anchorage in the paramedian region of the hard palate in orthodontic treatment.

Bicortical titanium screws for critical orthodontic anchorage in the mandible: a preliminary report on clinical applications.

Critical anchorage during orthodontic treatment in the mandible needs both time and effort and patient compliance. In 8 patients, 12 bicortical titanium screws (BIS) were used as anchorage units for orthodontic molar protraction. The criteria for patient selection were: critical anchorage in the lower jaw (i.e. retraction of anterior teeth undesirable) and molar extraction sites. After insertion of the screws in local anesthesia, orthodontic forces were applied immediately. One screw worked loose and had to be removed before the end of treatment. Problems encountered included impingement of the screw head and slight inflammatory reactions of the surrounding mobile mucosa, which necessitated premature removal of two screws. After healing, a new insertion site was chosen. Further treatment was uneventful. Anchorage for orthodontic forces as described offers several advantages. The total treatment time is reduced as the screws can be loaded immediately. The line of action of the orthodontic force coincides with the level of the center of resistance of the molar resulting in a favorable translatory tooth movement. Treatment does not depend on patient cooperation.

Functional magnetic resonance imaging of temporomandibular joint disorders.

Fifty-eight temporomandibular joints (TMJs) from 40 patients with TMJ-related symptoms were examined by means of magnetic resonance scans with modified gradient echo sequences and a special double coil. This technique yielded a good spatial resolution of the intra-articular soft tissues, especially the articular disc and the bone structure of the TMJ. In combination with an incremental jaw opener, the disc-condyle complex was analysed in various closed and open mouth positions, depending on the clinical examination. Open mouth movement with differentiation of disc-condyle rotational and translation movement was demonstrated. Disturbances of TMJ motion showed interrupted condylar translation combined with mandibular deviation during open mouth movement (n = 8/58). Early phases of internal derangement of the TMJ with partial anterior disc displacement with (n = 12/58) or without (n = 2/58) reduction, total anterior disc displacement without reduction (n = 10/58), disc deformation (n = 10/58), disc adhesion (n = 2/58), condylar hypermobility (n = 6/58), condylar displacement (n = 8/58), and late phases of internal derangement of the TMJ with osteoarthrosis (n = 14/58) were clearly identified. Bilateral TMJ disorder was found in 72.5 per cent of the patients. By using motion-adapted, semi-dynamic magnetic resonance imaging (MRI), it is possible to improve the understanding of the complexity of TMJ movements.

Contemporary treatment of the resorbed avulsed tooth: a case report.

This report describes the treatment sequence after traumatic loss of a maxillary central incisor in a 15-year-old patient. Following extraoral root canal treatment and initially successful replantation, the case presented 9 years later with complete root resorption. After augmentation with an autologous mandibular corticocancellous graft, a dental implant was placed in a second stage surgery. The case highlights the challenge facing clinicians in providing the appropriate standard of care for today's treatment options.

Secular trends in malocclusion in Austrian men.

A comparison between occlusal deviations in the permanent dentition in the skulls of 94 19th century and 157 present-day Austrian males was made by means of the PAR Index. It was found that the contemporary dentitions showed significantly higher malocclusion scores than the 19th century sample (weighted PAR Index 11.79 and 6.62, respectively). The results show that secular changes in malocclusion have occurred during the last 100 years.

Initial effects of treatment of Class II malocclusion with the Herren activator, activator-headgear combination, and Jasper Jumper.

The initial effects of treatment of Class II, Division 1 malocclusion with an activator, according to Herren (27 patients), with an activator-headgear combination (20 patients), or with the Jasper Jumper appliance (25 patients) were studied on lateral cephalograms from before and after 6 to 8 months of treatment. The patients' ages ranged from 9 to 12 years. At the end of the period of observation, the correction in overjet and molar relationship was more complete in the patients with the Jasper Jumper than in the patients with the activator. Whereas all the patients with the Jasper Jumper showed neutral occlusion, this was the case in only 20 of the 47 patients with the activator. The correction of the distal occlusion occurred through a combination of skeletal and dentoalveolar adaptations. Skeletal changes accounted for 42%, 35%, and 48% of the overjet correction by the Herren-type activator, the headgear-activator, and the Jasper Jumper, respectively. The correction of the molar relationship occurred to 55%, 46%, and 38% by skeletal changes in the respective groups. Dentoalveolar compensation (distal movement of the upper molars, mesial movement of the lower molars) appeared to be inversely related to skeletal adaptation. The patients with the Jasper Jumper showed a marked intrusion of the lower incisors with a consequent reduction in overbite.

Evaluation of continuous arch and segmented arch leveling techniques in adult patients--a clinical study.

The purpose of this study was to compare the efficacy of overbite correction achieved by a conventional continuous arch wire technique and the segmented arch technique as recommended by Burstone. The sample comprised 50 adult patients (age 18 to 40 years) with deep bites. Twenty-five patients were treated with a continuous arch wire technique (CAW); in the second half of the sample, the segmented arch technique (Burstone) was used for correction of the vertical malocclusion. Lateral cephalograms and plaster cast models taken before and immediately after treatment were evaluated. Statistical analysis was performed on the collected data. The results showed that both techniques produced a highly significant overbite reduction (CAW: -3.17 mm, p < 0.001; Burstone: -3.56 mm, p < 0.001). The CAW group showed an extrusion in the molar area with subsequent posterior rotation of the mandible (6occl-ML: +1.30 mm; 6occl-NSL: +1.63 mm; ML/NSL: +1.94 degrees, all p < 0.001). The Burstone group, however, showed overbite reduction by incisor intrusion without any substantial extrusion of posterior teeth (upper 1-NSL: -1.50 mm; lower 1-ML: -1.72 mm; both p < 0.001). As a consequence, no significant posterior rotation of the mandible took place (ML/NSL: +0.52 degrees, n.s.). It is concluded that in adult patients the segmented arch technique (Burstone) can be considered as being superior to a conventional continuous arch wire technique if arch leveling by incisor intrusion is indicated.

Moments and forces delivered by transpalatal arches for symmetrical first molar rotation.

The moments and forces delivered by round transpalatal arches of steel and of beta-titanium (TMA) for symmetrical derotation of molars were studied in laboratory experiments. Three sizes of arches were tested in two series. In the first series, the degree of activation was checked for symmetry in a computer-based strain-gauge measuring system. In the second series, the activation was carried out in a way simulating clinical use. The mesio-distal and transverse forces and the derotating moments at full activation and during derotation in steps of 5 degrees were measured. At full activation, the steel arches delivered relatively large moments which, however, decreased rapidly during deactivation. The TMA arches had a larger working range. It was not possible to achieve full symmetry of the moments at the two ends of the arch. The difference of the two moments resulted in forces acting on the two anchorage teeth in a mesio-distal direction. These forces were generally small but could reach clinically relevant magnitude. The derotation resulted in a contractive force of up to 2.7 N which has to be compensated for by expansion. The mode of activation simulating clinical use resulted in reasonably constant forces and moments. The use of a vice to hold the arch during activation was found to be of great help and is recommended in the clinical setting. Because of the larger working range, TMA arches are recommended if substantial derotation is needed.

Treatment of Class II malocclusions with the Jasper Jumper appliance--a preliminary report.

The effect of the Jasper Jumper appliance (American Orthodontics, Sheboygan, Wis.) on the dentofacial complex was studied in 17 consecutive growing patients who had Class II, Division 1 malocclusions. Lateral cephalograms taken before treatment and immediately after removal of the Jumpers were analyzed according to the method of Pancherz. The following results were found: (1) Class I occlusal relationships were achieved in all patients in an average treatment time of 6 months. (2) The correction of the Class II malocclusion was a result of skeletal (40%) and dental (60%) changes. (3) Skeletal Class II correction was predominantly restricted to the mandible. (4) The dentoalveolar part of total molar relationship correction took place to the same extent in both jaws, whereas in overjet correction the maxillary dental changes outweighed the mandibular changes by far. (5) When compared with normal growth changes (Bolton standards), treatment with Jasper Jumpers distalizes the upper dentition and moves the lower teeth mesially. Mandibular growth seems to be increased to some extent. It was concluded that treatment with the Jasper Jumper appliance presents an effective method to correct Class II malocclusion in growing patients.

The centered T-loop--a new way of preactivation.

The force system of a prefabricated and preactivated T-loop used for reciprocal space closure was determined by simultaneously measuring the horizontal and vertical forces, as well as the moments using a computer controlled measuring apparatus. Interbracket distances of 21, 24, 27, and 30 mm were used to mimic typical clinical situations. At a loop activation of 7 mm, the anterior and posterior segments first underwent controlled tipping, then translation, and finally, root uprighting as the moment-to-force ratio increased with deactivation. After the loop has been deactivated to 4 mm, however, it should be exchanged to avoid root abutment.

A study of bite force, part 1: Relationship to various physical characteristics.

A new device for measuring and recording bilateral bite force in the molar/premolar region has been developed. Because this new device is elastic and conforms to the occlusal surfaces of the teeth, and because the sensing element is relatively comfortable, it is believed that experimental subjects are less reluctant to register true maximal forces than in earlier studies. Potential correlations of maximum bite force to gender, age, weight, body type, stature, previous history of orthodontic treatment, presence of TMJ symptoms (jaw motion limitation, clicking with pain, or joint pain), or missing teeth were studied in a sample of 142 dental students. The mean maximum bite force of the sample was found to be 738 N, with a standard deviation of 209 N. The mean maximum bite force as related to gender was found to be statistically significant, while the correlation coefficients for age, weight, stature, and body type were found to be low. Even so, all data scatterplots exhibited relatively positive relationships. Correlations of maximum bite force to an earlier history of orthodontic treatment or to the absence of teeth were not found. Subjects reporting TMJ symptoms did not exhibit a significantly different maximum bite force than subjects without symptoms.

A study of bite force, part 2: Relationship to various cephalometric measurements.

Maximum bilateral bite force, determined in 129 dental students, was evaluated with regard to six skeletal and eight dental measurements acquired from conventional lateral cephalometric radiographs. Statistically significant correlations for three of the skeletal measurements were found. Maximum bite force increased with regard to decreasing mandibular plane/palatal plane angle and to decreasing mandibular plane angles. Maximum bite force increased with an increasing ratio of posterior facial height to anterior facial height. Significant statistical correlation for only one of the eight dental measurements was found: maximum bite force related directly with increasing maxillary and/or mandibular dentoalveolar heights, and unexpected finding.

Force delivery from a transpalatal arch for the correction of unilateral first molar cross-bite.

The forces and moments delivered by prefabricated transpalatal arches of the makes Unitek, GAC, and Ormco were studied in laboratory experiments. The Unitek and GAC arches were made of steel, and the Ormco arch of beta-titanium alloy (TMA). Three types of activation were investigated: for bilateral expansion in a statically indeterminate system and for unilateral expansion in a statically determinate system with and without torque activation. In addition to the arch design, composition, and mode of activation, the influence of arch size and degree of activation were studied. It was found that activation for unilateral expansion with the inclusion of torque in the statically determinate system produced forces and moments suitable for the correction of a unilateral cross-bite.