British Orthodontic Society national audit of temporary anchorage devices (TADs): report of the first thousand TADs placed

OBJECTIVE

To provide data from the British Orthodontic Society (BOS) national clinical audit on temporary anchorage device (TAD) use following the recommendations of the National Institute for Health and Clinical Excellence (NIHCE) Design and setting: The Audit commenced on 1 January 2008 and is still ongoing. This article reports the data for TADs placed from 1 January 2008 to 1 November 2013.

MATERIALS AND METHODS

Audit data was collected from participants using a system of both on-line data entry and hard copy forms. The criteria and standards for the audit were set following the NIHCE report in conjunction with the Development and Standards Committee of the BOS. Virtually all participants used the on-line data entry available on the BOS website. The data submitted was checked and entered manually into an Excel spreadsheet, and transferred to SPSS for analysis.

RESULTS

Written information and documented discussion of risks were provided in over 90% of TADs placed, but 17.4% were placed without a specific signed consent form. Temporary anchorage device failure rate was 24.2% overall. Among failed TADs, 93.1% were lost or removed due to excess mobility. Infection or inflammation resulting in loss or removal was reported in 6% of TADs.

CONCLUSIONS

The only audit standard that was met was failures due to infection of inflammation. The rest of the audit standards were not met. Recommendations are made to address these issues.

Interdisciplinary index of prosthodontic/substitution orthodontic treatment need for patients with missing teeth

The need for treatment in cases of missing teeth may result from aesthetic demands or functional impairment, although tooth loss itself does not necessarily constitute a need for prosthetic replacement. In selected cases, restorative treatment can be replaced by tooth autotransplantation or substitution orthodontic treatment. The authors have tried to make an index based not on missing particular teeth, but on the presence of spacing requiring restoration. An attempt has been made to categorize the restorative treatment need. Orthodontic treatment was considered, when it could completely eliminate the need for prosthetic treatment. The proposed classification could be used for assessing eligibility for public refund of restorative or substitution orthodontic treatment, as well as to motivate the patients to have restorations. It should be an individual approach-based decision, which treatment: orthodontic substitution tooth movement or prosthodontic is more cost-effective for the rest of the patient's life.

2013 survey of Australian orthodontists' procedures

AIM

This survey of Australian orthodontists was conducted to assess treatment preferences.

METHODS

Email invitations to participate in an online survey were sent to a total of 433 Australian Society of Orthodontists (ASO) members and 158 replies were received (36% response).

RESULTS

For Class II treatment, most practitioners preferred to wait and treat later but when early treatment was performed, the Twin Block was the most popular appliance. For fixed appliance treatment, the 0.022 inch slot was the most commonly used (73%) and the median treatment time was 20 months. The median extraction rate was 23% which was similar to that reported in a 2008 USA survey. Sequential plastic aligners were used by 73% of respondents and Temporary Skeletal Anchorage Devices were used by 77%. The most common research question clinicians would like answered related to retention.

CONCLUSION

The responses were similar Australia-wide but some areas of difference were revealed and discussed.

Frictional evaluations of dental typodont models using four self-ligating designs and a conventional design

Abstract: After a previous study using typodonts and three standardized archwire (AW) sizes, the frictional evaluations of four self-ligating brackets were directed toward the optimal AW-bracket system. Four participating manufacturers suggested three AWs, which were a representation of the three stages of orthodontic treatment, to be coupled with their respective self-ligating design. Four replicated typodont models were mounted with a self-ligating design, and a fifth model was mounted with a conventional design that served as a control. The first experiment evaluated the manufacturer-suggested AWs against the respective self-ligating design. Because no third-stage AWs could engage their respective designs, a second experiment was implemented to gain more detailed analyses of the designs. This experiment included any successful manufacturer-suggested AWs from the first experiment against the four self-ligating designs and the control design. All self-ligating designs performed with the efficiency and reproducibility associated with expectations. Specifically, self-ligation outperformed the conventional brackets when coupled with up to 0.020- x 0.020-inch wires. The clearance of the various AW sizes and alloys changed with malocclusion. Furthermore, the parameter that best correlated with drawing forces was the bending stiffness of the AW, which was directly associated with the nominal dimension of each wire. The best AW-bracket system can be selected, when taking into account the stiffness (elastic modulus and size of the AW) along with the amount of malocclusion present, once the treatment plan is determined.

Objective assessment of occlusal and coronal characteristics of untreated normals: A measurement study

To determine whether tooth shape and position are constant within tooth types, dental casts of 68 Indians (age range, 10-32 years; mean, 18.72 years) were analyzed. The casts were selected from a larger sample and met the following criteria: Class I molar and canine relationships; overjet and overbite within normal limits; well-related vertical, transverse, and anteroposterior relationships with pleasing profiles and well-aligned arches; and no supernumerary teeth or large restorations. None of the subjects had received orthodontic treatment, and all were in good health and exhibited normal growth. Crown angulation, inclination, offset of maxillary molar, curve of Spee, crown facial prominence, horizontal crown contour, and vertical crown contour were assessed. Means, standard deviations, and standard errors were calculated. The measurements were compared with Andrews's data on 120 nonorthodontic normal occlusion casts. The Student t test was used to determine the significance of differences between the 2 sets of data. It was found that teeth of the same tooth type have similar values of horizontal and vertical crown contours. Values for inclination, angulation, and relative prominence were also similar. Hence, we concluded that tooth shape and position are constant for each tooth type. The data from this study were comparable with Andrews's findings. However, from this study, it would be safe to presume that all teeth except the maxillary second molars require alterations in the bracket base inclination value, and that the maxillary lateral incisor, canine, second premolar, and second molar, and the mandibular canine, require alterations in angulation values.

[A study on the lingual shape and position of the teeth in Chinese with normal occlusion]

OBJECTIVE

To measure the lingual surfaces of the teeth in normal occlusion and obtain the data for lingual brackets' bonding and modifying for Chinese.

METHODS

50 casts of nonorthodontic subjects with ideal occlusion were examined using the YM-2115 3D measurement instrument. The data was calculated by the relevant software and analysed statistically.

RESULTS

The reference values of the lingual surfaces of the teeth in normal occlusion were obtained. These include crown angulation(tip), crown inclination(torque), offset angles of molars and crown facial prominence.

CONCLUSIONS

Compared with the data of foreigners, the characteristics of the lingual surface of the teeth in Chinese normal occlusion has many differences. The accurate placement of the lingual orthodontic brackets should be assisted by laboratory techniques because of the highly variable morphology of the lingual surfaces of the teeth.

Biomechanical investigation of the hybrid retraction spring

We succeeded in developing a retraction spring that shows virtually constant retracting forces up to an activation of about 4.5 mm through the use of various non-linear materials. Compared to all other known retraction springs, an actual bodily retraction is possible over a large range for the first time. The clinical application requires no more than one reactivation. The anti-tipping moment is 10 Nmm and is to be considered constant over the entire activation range. This anti-tipping moment produces an extrusive force for the canine and an intrusive force for the molar. This side-effect can be avoided by bending a sweep into the steel portion or compensated by bending a step into the steel portion of this retraction spring. The anti-rotational moment is about 3 to 5 Nmm measured over the entire activation range. In contrast to many other springs, the favorable M/F ratio for the anti-tipping movement allows an actual bodily retraction of canines. Even when the retracting force is no longer active, the moment that moves the root of the canine distally is still acting, so that the spring can also be used for the root movement. The M/F ratio for the anti-rotational movement is between 3 and 5 mm and therefore allows retraction of the canine without causing major distortions. Customary brackets with a .018" or .022" horizontal slot can be used, as the spring is designed for a .018" x .018" vertical slot. Each spring can be used for both the left and the right canines. The steel portion allows second-order and, if desired, third-order bends to be made. The additionally necessary bends have already been described. The hybrid retraction spring can also be applied for en masse retraction of incisors if a cross-tube is used for the anterior area.

Torque transmission between square wire and bracket as a function of measurement, form and hardness parameters

The aim of the study was to investigate the influence of cross section, edge geometry and structural hardness on torque transmission between square wire and bracket. For this purpose, 5 different brands of stainless steel square wire in 3 dimensions (0.016" x 0.016", 0.016" x 0.022" and 0.017" x 0.025") were inserted into edgewise brackets with a slot size of 0.018" and loaded with different torques (1 and 3 Ncm). The slot and wire geometries were analyzed by computer on ground specimens before and after loading. In addition, the Vickers hardness and micro-hardness of the unstressed and stressed metal surfaces were determined. While the slot size was very accurately maintained, the wire dimensions deviated downwards by an average of 10%. Torque transmission led to notching and bending-up phenomena on the bracket slot flanks. A torque loading of 3 Ncm increased the torque play of 0.016" x 0.022" wires by 3.6 degrees, and of 0.017" x 0.025" wires by 3.7 degrees. In the case of 0.016" x 0.016" wires, an effective torque transmission was no longer possible. The average Vickers hardness of the wires was 533 kp/mm2, and that of the brackets 145 kp/mm2. The micro-hardness in the deformation area of stressed internal slot walls increased with increasing load transmission from 204 to 338 kp/mm2. As a result of excessively small wire dimensions and plastic deformation of the brackets, a relatively large torque play occurs. Deformation and notching in the area of the internal slot walls are inconsistent with demands for recycling brackets. A standardization of bracket wire systems stating the actual torque play would be desirable.

Modified pendulum appliance including distal screw and uprighting activation for non-compliance therapy of Class-II malocclusion in children and adolescents

In present-day orthodontics there is an increasing call for therapeutic procedures and appliances allowing those delivering the treatment maximum independence from patient cooperation. This requires both the development of new therapeutic appliances and the optimization of existing ones (via modification). The present study aims to analyze the therapeutic outcomes obtained by using a pendulum appliance (distal screw and integrated molar uprighting activation), modified and independent of patient cooperation. The dentoalveolar and skeletal outcomes and secondary outcomes were observed in 50 children and adolescents. The dentoalveolar outcomes were as follows: 72.5% of the clinically visible increase in space were gained by distal molar movement and 27.5% by mesialization of the anterior segment. The molars showed slight distal tipping and extrusion, while the incisors showed slight labial tipping. In terms of time, the molars were moved distally by an average of 0.67 mm per month. Skeletal changes taking place during treatment using the pendulum appliance are negligible. Further advantages of the pendulum appliance are independence from patient cooperation and good acceptance by patients.

Evaluation of the effect of a stabilization splint on occlusal force in patients with masticatory muscle disorders

The purpose of this study was to evaluate the effect of stabilization splint therapy on occlusal force in patients with masticatory muscle disorders (MD). Six female patients with myalgia or myofascial pain participated in this study. The occlusal points and load on the dental arch in maximum clenching was measured using the computerized system with Dental Prescale(R) before and after the use of the splint. There were no significant changes in the number of occlusal points, mean occlusal pressure, and asymmetry in occlusal balance between before and after the use of the splint. However, there were significant differences in the extent of the area of occlusion and in the integrated occlusal loads. The integrated occlusal load converged to the normal level with the use of the splint. From the results of this study, it is suggested that the use of the stabilization splint has the effect of normalizing the occlusal force.

Effects and adverse events of a dental appliance for treatment of obstructive sleep apnoea

In a prospective study, 95 patients with mild to moderate obstructive sleep apnoea (OSA) were randomised to receive either surgical treatment, uvulopalatopharyngoplasty, (4-6 patients) or treatment with a nocturnal dental appliance for mandibular advancement (49 patients). Of the 49 dental appliance patients, 37 completed the 12-month follow-up. The aim of this study was to evaluate the effects and adverse events of dental appliance treatment from a one-year perspective. Somnography was employed to measure treatment effects before and 12 months post-treatment. At the 12-month control, somnography was performed twice: the first time with the dental appliance and the second time without it. Adverse events were recorded 2 weeks and 3, 6, and 12 months after treatment was initiated. The patients used the dental appliance on average 6 nights/week. After 12 months of treatment, the apnoea, apnoea/hypopnoea, oxygen desaturation, and snoring indices decreased significantly. Ninety-five per cent of the patients reduced their apnoea index by > or = 50% and 78% of the patients were normalised following treatment. At the somnographic registration without the dental appliance, the values were found comparable to what they were before treatment. Mandibular mobility and occlusion were constant throughout the study. The adverse events resulting from using the dental appliance were relatively minor and infrequent, and no serious complications were observed except for two patients who reported pain from the temporomandibular joint. In conclusion, the dental appliance has been shown to be a valuable treatment method for mild to moderate OSA with few adverse events in the stomatognathic system or other complications.

Properties of crimpable archwire hooks: a laboratory investigation

The aim of the present study was to utilize a strain gauge, which enabled the force applied to produce firmly attached crimpable hooks to rectangular stainless steel arch wires, to be measured. In vitro testing of two hooks, American Orthodontic (AO) and TP Orthodontic (TP), and two dimensions of stainless steel archwire, 0.019 x 0.025 and 0.018 x 0.025-inch, was carried out using an Instron Universal Testing machine. The results demonstrate that there was a significant difference in the behaviour of the two types of crimpable hooks, with almost twice the force needed to dislodge the TP hooks compared with the AO hooks (11.7 and 6.22 N, respectively). When using TP hooks attached to either 0.019 x 0.025 or 0.018 x 0.025-inch stainless steel wires, the archwire size makes little difference to the force required to produce movement. The clinical significance of these findings is discussed.

The influence of bracket design on frictional losses in the bracket/arch wire system

In arch guided tooth movement, the essential role played by bracket configuration with respect to sliding friction has been recognized by the manufacturers, a fact which has had an increasing impact on the design and marketing of new bracket models in recent years. The aim of the present in-vitro study was to investigate the influence of different bracket designs on sliding mechanics. Five differently shaped stainless steel brackets (Discovery: Dentaurum, Damon SL: A-Company, Synergy: Rocky Mountain Orthodontics, Viazis bracket and Omni Arch appliance: GAC) were compared in the 0.022"-slot system. The Orthodontic Measurement and Simulation System (OMSS) was used to quantify the difference between applied force (NiTi coil spring, 1.0 N) and orthodontically effective force and to determine leveling losses occurring during the sliding process in arch guided tooth movement. Simulated canine retraction was performed using continuous arch wires with the dimensions 0.019" x 0.025" (Standard Steel, Unitek) and 0.020" x 0.020" (Ideal Gold, GAC). Comparison of the brackets revealed friction-induced losses ranging from 20 to 70%, with clear-cut advantages resulting from the newly developed bracket types. However, an increased tendency towards leveling losses in terms of distal rotation (maximum 15 degrees) or buccal root torque (maximum 20 degrees) was recorded, especially with those brackets giving the arch wire increased mobility due to their shaping or lack of ligature wire.

A closer look at General Dental Service orthodontics in England and Wales. II: What determines appliance selection?

AIM

To elucidate factors that influence choice of appliance type in General Dental Service (GDS) orthodontics in England and Wales.

METHOD

Records were obtained for 1527 cases, representing a systematic 2 per cent sample of GDS cases completed during 1990-91. Evaluation involved Discriminant Analysis to find the most influential factors in appliance choice. Factors considered included patient and practitioner characteristics, and features of the malocclusion as assessed by Occlusal Indices.

RESULTS

Full data were available for 1217 cases. 24 per cent of treatments included use of dual- and 26 per cent single-arch fixed appliances. Appliance choice was predictable in 55 per cent of cases. Older patients, orthodontically qualified practitioners, high Peer Assessment Rating score at start, permanent dentition, lower grades of the Dental Health Component of the Index of Orthodontic Treatment Need at start, and practitioners with high gross earnings from orthodontics, all tended to be associated with more frequent use of fixed appliances.

CONCLUSIONS

Possession of a diploma or membership in orthodontics was associated with more frequent use of both dual- and single-arch fixed appliances. Better appliance selection, and thus more effective treatments in the GDS, may result from a greater availability of practitioners with formal postgraduate training in orthodontics.

Breakage incidence with direct-bonded lingual retainers

This study examined the effects of a number of patient and clinical variables on the breakage of bonded retainers, and consisted of a retrospective review of the survival of 200 bonded retainers. Data was collected from two clinical centres between November 1996 and February 1997. The subjects comprised 198 patients of both sexes divided into three age groups. Retainers at both centres were made in 018-inch co-axial wire with Relyabond and Helioprogress adhesives used at each respective centre. The effects on time to first breakage of adhesive, patient sex, and arch (upper/lower) were considered using Kaplan Meier survival graphs and in Log Rank Tests. Finally, a Cox Proportional Hazard Model was used to examine the joint effects of these factors and the patients' ages. Breakage over a 5-year period with Relyabond was 38.8 per cent upper, 22.1 per cent lower, and with Helioprogress 75 per cent upper and 23.2 per cent lower. Breakage appears to be unrelated to the materials used or to the age and sex of the patients. Upper retainers break more often than lowers (P = 0.016) and early breakage is more likely to occur at an adhesive pad than at a wire (9.6 versus 2.5 per cent within 6 months).

Effectiveness of intra- and extraoral aids to the bionator. A controlled study within the scope of the "Wuerzburg concept"

A bimaxillary device is effective only if the therapeutic position of the mandible is maintained for as long a period as possible by day and night, i.e. the lower jaw cannot "drop" from the construction bite position. One simple means of preventing the mandible from dropping out of the bimaxillary appliance during sleep and thus of ensuring adaptation of the muscles and of the joint structures during the night without impairing active adaptation during daytime functions (speaking, swallowing) is being used at Wuerzburg University Department of Orthodontics: In connection with anterior traction, which anchors the bimaxillary appliance to the maxilla, attachments are fixed to the mandibular canines or first premolars, so that the mandible is kept in the therapeutic position during the night by means of elastics. Besides the description of this method, the results of a clinical study on its effectiveness are presented in this paper. In the experimental group (20 Class II/1 patients) treated with the combination of bionator with anterior extraoral traction and up-and-down elastics, the increase of the SNB angle and accordingly of the ANB angle was twice as great as in a control group treated only with bionator and extraoral traction without additional securing of the mandible.

Force characteristics of nickel-titanium tension coil springs

Nickel-titanium closed coil springs are commonly used for space closure. The springs possess a high resistance to permanent deformation and the potential for relatively constant force delivery. A study was designed to determine whether relatively constant forces can be delivered and whether the force magnitudes approach the manufacturer's targeted force values. Heavy, medium, and light springs were activated 15 mm at temperatures that ranged from 15 degrees C to 60 degrees C. The forces were measured during deactivation with a specially constructed force transducer temperature chamber. Relatively constant forces can be achieved with an over-activation procedure that allows relaxation to the desired activation. The light springs delivered forces that were near the targeted force; no difference was found between the heavy and medium springs in the constant force range. The force magnitudes varied markedly depending on mouth temperature.

Biomechanical analysis of arch-guided molar distalization when employing superelastic NiTi coil springs

Two typical treatment situations (distalization of a last molar, distalization of a molar with the guiding arch fixed on the most distal abutment tooth) were simulated experimentally using the Orthodontic Measurement and Simulation System (OMSS). For this purpose an upper first molar was guided along steel arches with differing cross sections (0.016" x 0.022"/0.41 mm x 0.56 mm; 0.017" x 0.025"/0.43 mm x 0.64 mm) using a nickel-titanium (NiTi) compression spring. The 6 NiTi springs investigated differed in their design and in the type of force delivery. The force application that was eccentric with respect to the center of resistance caused a conflict situation between the tube and the guiding arch through rotations of the molar. Although the force level of the springs was almost constant, the orthodontically effective forces measured fluctuated due to frictional losses. With progressing distalization the mean frictional forces increased, reaching values between 50 and 80% of the applied force of the compression springs. Simultaneously fluctuations in the frictional losses increased. Lower frictional losses were determined with a 0.016" x 0.022", than with a 0.017" x 0.025" guiding arch. Fixing the arch on the 3rd molar resulted in higher frictional losses compared to the distalization of a last molar. There were intensive interactions of the compression springs with the guiding arch and the tube. This resulted in extreme frictional losses even in the initial phase of the movement and in a complete stop to the distalizing movement in extreme cases. After removal of the convertible, the freedom of the molar movement could be regulated by the tension of the ligature wire. The friction varied accordingly. The distalization rate was not influenced by the force delivered by the compression spring. Small forces are biologically more favorable and thus should be preferred.

Short-term and long-term results after early treatment with the Castillo Morales stimulating plate. A longitudinal study

The present study is divided into 2 parts: The first explains the concept of stimulating plate therapy at the Muenster Clinic and the second presents a longitudinal study of mouth and tongue posture in trisomy 21 children treated with this concept. 47 children underwent a pre-treatment examination (Rec1), and 38 attended a first follow-up examination (Rec2) after an average of 4 months of stimulating plate treatment. The second follow-up examination (Rec3) was on average 53 months after the end of treatment and covered 18 patients. Data acquisition was based on standardized parent questionnaires and standardized clinical examination records. Rec2 showed in part a highly significant improvement in orofacial appearance. These results were confirmed by the parent interview, according to which the mouth and tongue posture improved in 76.3% of the children during the time they were wearing the plate. Even when the plate was not in place, the result remained stable in 65.8% of the patients. Up to Rec3, further improvement was recorded in some results. The symptoms: "mouth mostly wide open" and "tongue mostly protruding way over lips" were reduced. The number of children whose tongue was "mostly in the oral cavity" increased correspondingly. At Rec3, the parents also rated the mouth posture in 88.9% and the tongue posture in 77.7% of the children as stable or further improved.

Force systems developed by six different cantilever configurations

OBJECTIVES

To describe the force systems developed by cantilevers with different configurations during incisor intrusion.

DESIGN

A two-dimensional Finite Element model. SETTING AND SAMPLE STUDIED: Laboratories of the Department of Orthodontics, Royal Dental College, Aarhus University, Denmark. The materials studied comprised cantilevers made of 0.017" x 0.025" TMA wire.

EXPERIMENTAL VARIABLE

Vertical activation of the six different modelled cantilever configurations.

OUTCOME MEASURE

Force level and direction during activation and deactivation analysed at the point of force application.

RESULTS

The force direction was dependent on the configuration of the cantilever. Only the cantilevers with a curvature produced combined retraction and intrusion forces. All other configurations resulted in combined protrusion and intrusion, which reversed into retraction and intrusion, according to the variations in deactivation.

CONCLUSION

The choice of correct cantilever configuration is important when selecting the mechanics of intrusion for a particular patient.

The influence of the spring activator on the mobility of the lower jaw in traumatically injured patients

For functional rehabilitation and improvement of mandibular mobility, 14 patients with dislocated collum or collum fracture dislocations were treated with a spring activator after surgical-conservative treatment. With an interincisal distance of < 12 mm, therapy was started with a loop spring. The average age of the patients was 26.6 years. Eight patients showed additional traumatic injuries, 2 patients were seriously polytraumatically injured. The clinical investigations referring to the maximum mouth opening and maximal interincisal distance resulted in a good to very good functional rehabilitation in all cases. The average maximal interincisal distance of 31.7 mm at the beginning of the spring activator therapy could be increased to 47.3 mm. The largest increase of the maximal interincisal distance was observed after 4 weeks of therapy. The type of reaction, however, differed interindividually. Three patients showed a spontaneous improvement of the interincisal distance within the first 2 to 3 weeks of removal of intermaxillary fixation, whereas 7 patients showed no improvement or only slightly improved values until insertion of the spring activator. An enlargement of the interincisal distance could be achieved in almost every patient within a relatively short period of time despite a drastically reduced mouth opening. Consequently, because of its mode of action in the form of a neuromuscular influence, the spring activator is especially suitable for the functional rehabilitation of patients with fractures of the condylar process.

Frictional forces when rectangular guiding arches with varying edge bevel are employed

In orthodontic treatment employing arch guided tooth movement, rectangular wires are usually used to achieve three-dimensional controlled tooth movement. In the intention to optimize sliding mechanics and to improve the comfort of patients, edge beveled rectangular orthodontic wires are offered by different manufacturers. The objective of the study presented was to investigate the influence of differing but defined wire roundings on sliding mechanics of canine retraction. Employing the 0.018" slot system, 0.016" x 0.022" standard steel wires (Remaloy and Remanium, Dentaurum Comp.) were tested. Force loss due to friction during canine retraction was determined using the Orthodontic Measurement and Simulation System (OMSS). In the arch guided distalization of canines, the average loss of force caused by friction was determined to be approximately 50%. Comparing wires with different edge bevel, the rounded wire in contrast to the wire with sharpest edge configuration results in a reduction of friction. Even a moderate wire rounding of the 0.016" x 0.022" steel wire results in about 10% reduction in frictional losses. However, dynamic analysis of tooth movement with the OMSS shows that there is no further improvement of sliding mechanics using wires with edge bevel exceeding the standard rounding of rectangular wires. In contrast, a strong edge bevel may result in a considerable loss of leveling.

In vitro testing of a measuring system for in vivo recording of orthodontically applied forces and moments in the multiband technique. Part II

The aim of this study was to measure in vivo the forces and moments acting therapeutically on the individual tooth in connection with the multiband technique. Securing and evaluating the planned in vivo measurements involves analysing the measuring accuracy of the system as a whole by means of corresponding in vitro investigations. Errors in determining the therapeutically effective force system may result from the electrical measurement of the mechanical quantities by the sensor system and from the fixing of the archwire in therapeutic position. The precision of this fixing is influenced by displacements induced by elasticities and mechanical tensions in the measuring system. Calibration test series have shown the sensor system to have a margin of error of less than 2%. The displacements influencing precision fixing of the archwire were determined by means of a laser position measuring system. For a maximum orthodontic force of 1.5 N, they are 0.06 mm in the least favourable case. The resulting measuring accuracy was determined analytically or graphically, depending on the key parameters. Successful in vivo studies of the therapeutically applied force systems are to be expected on the basis of these results.

An experimental evaluation of effects and side effects of asymmetric face-bows in the light of in vivo measurements of initial tooth movements

By using a magnetic sensing system, the translational and rotational molar movements under the application of various asymmetric face-bows were measured two-dimensionally in human subjects to evaluate their primary effects and side effects. The asymmetric face-bow designs tested were three types of power arm face-bows, swivel offset face-bow, and internal hinge face-bow. Although all face-bow designs were considered to be effective in achieving asymmetric distalizations of the molars, they generated lateral displacements that may lead to an undesirable crossbite. The swivel offset face-bow may produce unexpected results and its fabrication is complicated. The internal hinge face-bow is remarkably effective for asymmetric molar distalizations. Unfortunately, it causes a strong crossbite tendency on the molar to be more distalized. Therefore the use of the power arm face-bow is thought to be relatively recommendable because it showed an acceptable asymmetric effect and is easily fabricated from a commercially available face-bow. It is concluded that all asymmetric face-bows generate lateral forces as side effects as long as the force delivery system with a combination of an asymmetric face-bow and a neck strap or head cap is applied. The current study suggests a method whereby the side effect of asymmetric face-bows can be eliminated.

On the variability of cross-sectional dimensions and torsional properties of rectangular nickel-titanium arch wires

Twenty-five rectangular superelastic or conventional work-hardened nickel-titanium alloy wires, commonly used in the 0.018-inch edgewise technique, supplied by seven different manufacturers, along with one braided nickel-titanium and two beta-titanium wires, were studied with respect to wire dimensions, edge bevel, and mechanical properties in longitudinal torsion at 37 degrees C. The wires were twisted 25 degrees and studied in deactivation, simulating application of torque to an individual tooth. Standard Siamese brackets. with stated slot heights of 0.018 inches and measured slot heights of 0.0187 inches, were used. Most wires were within +/-0.0005 inches of the stated dimensions, but had more edge bevel than previously reported for stainless steel and chrome-cobalt alloy wires. Variations in wire dimensions and edge bevel led to variable torsional (third-order) clearance. The torsional stiffness varied among manufacturers within the various wire sizes, this being the result of differences in actual cross-sectional geometry and material properties. None of the tested wires exhibited superelastic properties under the current conditions, and only one wire had a superelastic tendency.

Evaluation of debonding characteristics of a new collapsible ceramic bracket

A new collapsible ceramic bracket designed with a metal-lined arch wire slot has been recently introduced. The bracket also incorporates a vertical slot designed to help create a consistent bracket failure mode during debonding. The new bracket is thought to combine the esthetic advantages of ceramics and the functional advantages of debonding metal brackets. The purpose of this study was to compare (1) the shear bond strength of the new collapsible bracket with a traditional ceramic bracket, (2) the compressive force required to debond the new bracket from the enamel surface with that needed to debond a traditional metal bracket, and (3) the bond failure location when debonding the new bracket and a traditional ceramic bracket when pliers are used. Sixty-one Clarity collapsible ceramic brackets, 41 Transcend 6000 brackets, and 21 Victory Series metal brackets were bonded to the teeth with the same bonding system. The Zwick Universal Test Machine was used to determine the shear bond strength of 21 teeth bonded with the new bracket and 20 teeth bonded with the Transcend brackets. The same testing device was used to determine the compression force levels needed to debond 20 collapsible brackets and 21 metal brackets. Pliers were used to debond both the new ceramic brackets and Transcend brackets to determine the mode of bond failure. After debonding, all teeth and brackets were examined under 10x magnification. Any adhesive remaining after bracket removal was assessed according to the Adhesive Remnant Index (ARI). The findings indicated that the shear bond strength of the new Clarity ceramic bracket was comparable to that of a conventional ceramic bracket. Similarly, there were no significant differences in the results of the compression tests comparing the magnitude of forces needed to deform and debond both the new ceramic and metal brackets. The ARI scores for both the shear and compression tests indicated a similar bond failure pattern when the new collapsible brackets were compared with either the conventional ceramic or metal brackets. On the other hand, the chi-square test results indicated that, when debonding pliers were used, there was a significantly greater incidence of an ARI score of 1 with the collapsible brackets. This indicated that, when debonding the new brackets with the Weingart pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the main advantage of the Clarity ceramic brackets is that they can be debonded in the same manner as metal brackets. When the new ceramic brackets are debonded with the Weingart pliers, most of the residual adhesive remained on the enamel surface, a pattern that is similar to the one observed with metal brackets. The failure at the bracket-adhesive interface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding.

Continuous arch wire closing loop design, optimization, and verification. Part II

A systematic approach to closing loop design for use in continuous arch wires was presented in Part I. The design process used Castigliano's theorem to derive equations for moment-to-force ratio (M/F) in terms of loop geometry. The equations were used to optimize designs by optimizing M/F to produce tooth movement via translation. Further refinements were performed by use of finite element simulations of designs. In Part II the predicted results are verified experimentally. The result of this process is a new design, the Opus loop, which is capable of delivering a nonvarying target M/F within the range of 8.0-9.1 mm inherently, without adding residual moments by twist or bends (commonly gable bends) anywhere in the arch wire or loop before insertion. The resulting precise force systems delivered with nonvarying M/F can move groups of teeth more accurately to achieve predetermined anteroposterior treatment goals for esthetics and/or stability. The experimental results show that the loops must be bent accurately to achieve their design potential. The negative impact on M/F of various dimensional changes to the loop design are presented. Experimental data is presented illustrating the improved performance of the new design over standard available designs. Suggested applications of the design for varying anchorage requirements are presented, along with a case report in which rigorous protraction requirements were met.

Combined intrusion and retraction generated by cantilevers with helical coils

Combined retraction and intrusion of the anterior teeth is often needed as part of orthodontic treatment. The use of a statically determinate force system has many advantages over statically indeterminate systems. In the case of the cantilevers the orthodontist can evaluate the line of action of the delivered force directly in the clinical situation. In the present paper the force system delivered by stainless steel and beta titanium cantilevers with an eccentrically placed helix was evaluated. The cantilever consisted of a straight piece of wire bent to form a helix with an external diameter of 3 mm. The wire was fixed into a bracket of sensor 1, touching sensor 2 of a test bench with a 1-point contact to. Activation was induced by rotating sensor 1 into which the wire was tightly fixed. This was done in 2 different modes, one in the direction in which the helix was bent and one in the opposite direction. With an interval of 5 degrees the force system generated with respect to sensor 1 and the direction of the force delivered to sensor 2 (the other bracket) were registered. The results were expressed graphically and the influence of material and activation mode were evaluated statistically by comparing the coefficient of regression. As expected, the influence of the material reflected the relative stiffness of the 2 alloys. As TMA is monocrystalline (i.e. consists of homogeneous crystals) the mode of activation did not reflect any significant Bauschinger effect as seen in the case of stainless steel. Analysis of the force direction confirmed that the suggested wire configuration is useful for delivery of a predetermined combination of horizontal and vertical force. This was confirmed by a finite element analysis.

Third order tooth movements with straight wire appliances. Influence of vestibular tooth crown morphology in the vertical plane

1. The labial surface in the vertical plane was investigated in 3 sections: center, mesial, and distal edge of an ideally positioned bracket. The material consisted of 28 casts taken from 14 female and male individuals with a mean age of 26.8 years. 2. After trimming each cast, the resulting surface was photocopied, enlarged 8 times, then digitized under a 2.0 mm grid (corresponding to 0.25 mm of the original size). 3. Using a statistical computer program, mean curves including standard deviations and non-linear regression curves were calculated from the individual data. In accordance with their anatomy 3 groups of teeth were formed in each jaw: front teeth, premolars, and molars. The curves, including the comparison of the squared regression curves, provide an accurate mathematical description of the labial tooth crown in the above-stated sections. 4. The angle differentials between a reference tangent and 20 other tangents were calculated. From a practical standpoint, information is obtained on the extent to which the torque of a tooth would be changed if a bracket was to be positioned vertically (in 0.5 mm increments) from its ideal position. These changes of torque fluctuate on average between 1.3 degrees (mandibular front teeth) and 3.3 degrees (mandibular molars) for every 0.5 mm of vertical deviation. 5. The calculated comparisons of the curves permitted the construction of bracket bases filling-at least in the vertical dimension-the tooth surface most accurately in the "optimal" position.

Bending and torquing accuracy of the bending art system (BAS)

With the bending art system (BAS) the computerized production of individual arch wires has become possible. The BAS consists of an intraoral camera, a computer program and a bending machine producing the archwire by consecutive bending and twisting procedures. This study examines the accuracy of the bending machine when using 0.016" x 0.016" and 0.016" x 0.022" steel wire of rectangular cross-section. Bending angles ranging from 6 degrees to 54 degrees, and torsion angles ranging from 2 degrees to 35 degrees were tested; also the minimum distance between these individual operations was determined. The bent pieces of wire were analysed in a 3D-coordinate gauging system. The 0.016" x 0.016" steel wire showed a mean measuring error of 0.62 degree in bending procedures and of 0.72 degree in torsion procedures, whereas the 0.016" x 0.022" steel wire showed an error of 0.87 degree with edgewise bendings and of 0.86 degree with torsions. To ensure this accuracy a minimum distance of 0.5 mm to 0.7 mm, depending on which kind of bending combination is used, between bending and torsion is required. The error could be reduced even further if a more constant wire material and a more accurate calibration of the bending machine were used. All in all the precision of the bending machine meets the clinical requirements.

[The development and testing of a new NiTi-SE-steel uprighting spring]

The uprighting spring presented here consists of a combination of superelastic material which is connected with a steel were by means of a crimped connector. Pseudo-elastic areas of such a spring can be used well by combining superelastic material with steel. The uprighting spring presented here yields the following advantages: 1. The uprighting moment of the molar is between 10 and 20 N with a 40 degree tipping of molar.2. The uprighting springs exhibit a large plateau in the area of 8 to 15 Nmm depending on a bending-in of an alpha-bend. 3. An intrusive force of approximately 0.5 to 1.0 N can be produced by varying the alpha-bend. The preformed uprighting spring in combination with a cross tube can be affixed without any problems, because only the alpha-activation must be bent in. 5. Practically, a reactivation during uprighting is not required. 6. An enlargement of the alpha-moment to produce an intrusive force makes great demands on the anchoring element. For this reason, one must check in each individual case, if an anchoring segment displays the required stability. 7. By lengthening the SE material at the crimped connector, the alpha and beta-moments become smaller, as does the intrusive (extrusive) force applied to molars.

[The clinical use of the new NiTi-SE-steel uprighting spring]

In clinical practice the NiTi steel uprighting spring presented in this study has been employed up until now to upright 30 molars. The advantage of this spring is that in large areas the pseudoelastic part of the spring transfers constant moments and forces to the molars. In addition, the steel part makes it possible to simply and easily adjust and fasten alpha-bends. Because of the relatively small uprighting moments of 10 up a maximum of 25 Nmm such an uptighting spring can also be applied without any modifications in cases in which the molars are tipped up to 50 degrees. Going beyond this our study determined that it is possible to exert intrusive forces of 0.4 N over the entire uprighting area by bending-in an 45 degrees alpha-bend. From a 15 degrees tipping on up the uprighting moments applied to molars remain relatively constant and they are only dependent on the bent alpha-activation. An uprighting by intrusive force on the molars can also be achieved through an alpha-activation of 0 degree (90 degrees + 40 degrees), when the vertical length of the pegs is enlarged. An on average 1.43 mm per month root mesialization of the uprighting spring with the Memory Maker, should such for whatever reason be considered desirable, take place only in the final stage. In almost every case of molar uprighting it is possible to fasten a figure eight ligature from the molar to the cross tube. The uprighting spring presented here combined with a cross tube proves to be an effective method for achieving a fast and trouble free uprighting of molars.

[The dental and skeletal changes in early Class II treatment with a Klammt open activator]

In order to evaluate the initiation of treatment of Angle class II malocclusion at an early age, seventy-six patients, 34 girls aged on average 10.1 years and 42 boys, average age 11.3 years, were selected for the study. For the treatment we used the Klammt open activator. For evaluation purposes we used casts and cephalograms taken before and after treatment. The results showed distinctive differences between Angle class II/1 and II/2. The sagittal correction in class II/1 was a result of the reduction of the SNA angle, the mandibular protrusion, and the retrusion of the upper incisors. The face high index was normalized. No labial inclination of the lower incisors was registered. In the Angle class II/2 cases the SNA angle was unchanged. The sagittal correction was brought about exclusively through mandibular translation. The deep bite and the retrusion of the upper incisors weren't markedly improved. The lower incisors showed a labial tip. The incisor angle was unchanged. Our study showed that the ANB reduction on an annual basis is highest, when treatment is initiated at an age of 10 to 11 years for girls and 12 years for boys. On the growth curve this is a point in time below the accelerated growth phase of puberty.

[How effective is asymmetrical headgear in practical use?]

The asymmetrical face bow with internal hinge was successfully employed in the treatment of all examined patients. It finds application as an individual appliance, in combination with removable appliances, and in conjunction with the fixed appliance technique. The major advantage of the face bow is that during a check-up visit, because it is already in place, it presents itself as a proven means for the treatment of asymmetries by adding a hinge on the side not to be distalized and by shortening the external arm on the same side. It is not necessary to employ a new, special face bow or even to change the orthodontic bands. In addition, in the case of an intermaxillary midline correction, no anchorage loss occurs. In the case of more extensive molar rotations, a pretreatment with a palatal archwire is recommended to rotate the molars. Because in 4% of the patients a cross bite or a cross bite tendency arises on the side distally treated, at the beginning of treatment the use of bands with attachments for palatal archwires should be considered. Relatively sizable distal forces in the range of 2:1 to 4:1 are exerted on the molar. This should be taken into account when selecting the forces of the external arm. It is recommended to apply on each of both sides a distal force of no more than 4 to 5 N. Decoupling of forces and movements through the internal hinge makes it possible for the practitioners to check the asymmetrical effect of the face bow by pulling out carefully the lingual archwire from the right or left tube. As long as the hinge still folds down, when the face bow is applied, the geometrics of the face bow should be altered. The following procedures can be recommended: 1. Further shortening of the already shortened arm; 2. outward bending of the long external arm; 3. use of an additional stop tube at the lingual archwire on the side that must be distalized. During the use of related low-pulls, the molars are subjected to diverse forces as a result of preferred sleeping positions, head bearings, and extensive friction, To avoid these non-calculable asymmetries, it is recommended to use gliding low-pulls. Because of the excellent results achieved throughout the use of the asymmetrical headgear with the lingual archwire, it can be recommended that it become a standard appliance in clinical practice.

[A functional orthodontic magnetic appliance (FOMA) after Vardimon. 1. A three-dimensional analysis of the force system of the attractive magnets]

The functional magnetic system (FMS) is a removable functional appliance which induces mandibular advance by means of mandibular and maxillary magnets in an attracting configuration. The maxillary and mandibular plates are each equipped with 2 cylindrically shaped cobalt-samarium magnets, 4 mm in diameter and 3 mm in height, which are welded into stainless steel housings. The force system of this magnetic configuration was analyzed using the orthodontic measurement and simulation system (OMSS). OMSS simulated the mandibular jaw movements by separating the installed magnets vertically, corresponding to a mouth opening of X = -10 mm, transversally (right excursion, +/left excursion, -) at Y = +/- 10 mm and sagittally (anterior displacement, +/posterior displacement, -) at Z = +/- 10 mm. The resulting 2D and 3D force/displacement diagrams elucidate the outstanding centripetal-spatial orientation characteristics of the functional magnetic appliance in reference to the full overlap brought about by the attraction of the mandibular magnet by the maxillary magnet. The maximum centripetal forces reached a value of approximately FY, max = 0.65 N for the vertical attracting force at full overlap of the mandibular and maxillary magnets (X = 0.55 mm, Y = Z = 0 mm), a value of FY, max = 0.65 N for the medial shearing force at a partial transversal overlap Z = 0, Y = +/- 2 mm and Y = +/- 6 mm), and for the sagittal shearing force a value of FZ, max = 1.2 N at a partial sagittal overlap of the magnets (Y = 0 mm, Z = +/- 2 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical experiences with the torque-segmented arch (TSA)]

The torque segmented archwire presented here led to a good torque transfer in all patients, however this transfer differed on a case by case basis. With regard to the angle 1-NA, the average monthly torque change was 2.34 degrees. The smallest torque transfer was 1 degree; the biggest 5.5 degrees per month. Because the torque segmented arch wires consist of a pseudoelastic material for the anterior teeth and a steel portion for the lateral teeth, the anterior component can be adapted to the patient's individual situation and in addition the lateral components make possible the bending of first, second and third order bends. The dimensions of the superelastic materials are 0.016 x 0.022, 0.017 x 0.025, and 0.018 x 0.025. In all 3 dimensions it is possible to select a torque of 30 degrees or 45 degrees. The use of such arch wires yields the following advantages: 1. Problem-free adaptation to the patient's individual situation. 2. Torque segmented arch wires can be applied in the case of the standard edgewise technique as well as in each case of the straight wire technique. 3. The practitioner is no longer dependent on the torque loss of the archwire and the individual axial position of the incisors. 4. With the help of the torque key it is possible at any time to control the already transferred torque with regard to the occlusal plane. 5. The torque segmented archwire can also be applied in the segmented archwire technique. 6. The torque segmented archwire with right angular or round lateral components is well suited for the retraction of the anterior area.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of molar position on the distalization behavior of indirect headgear]

The asymmetric indirect headgear is a frequently used method to achieve an unilateral distalization of a molar. Cases have been observed, however, in which the distalization does not proceed in the way or to the degree predicated by the geometry of the outer bow. Among other factors, this discrepancy can be attributed to the geometry of the inner bow. This study demonstrates quantitatively and qualitatively the influence unilateral mesial movement and/or molar rotation exerts on the force system of the indirect headgear. The study makes evident that a neutralization of the molar's sagittal asymmetrical position by means of adjusting the length of the inner bow cannot be omitted. The study recommends the use of special headgear tubes extended in an oro-vestibular direction to eliminate the asymmetrical dynamics which arise in cause of the mesial rotation of a molar.

[The dental and skeletal effects of the jumping-the-bite plate and high-pull headgear combination. A clinical study of treated patients]

While planning treatment of the 30 patients with a dental and skeletal class II anomaly on which this study is based, the primary treatment goals were correction of the dental and skeletal structures and attenuation of vertical growth by means of influencing the maxillary skeletal structures and the resultant mandibular reaction. The desired treatment results were achieved in all patients. Even so, however, the effects on individual patients in respect to skeletal influences were markedly different. It was especially helpful that during therapy simultaneously with exerting influence on the maxillary base plane, the influencing of the occlusal plane occurred in the same direction. Through the additional application of high-pull headgear, maxillary growth was clearly restrained and the inclination of the maxillary base plane inhibited. Even difficult skeletal discrepancies, sagittal as well as vertical, can be treated with the bite-jump appliance in combination with a high-pull headgear. This also makes it possible to achieve protrusive repositioning of the mandible in patients with a pronounced vertical growth pattern without causing on open bite. In retrospective the patients' treatment plans proved to be completely appropriate, however, the fact should not be overlooked that changing the occlusal plane is essential for the realization of a positive therapeutic result.

[Biomechanical testing of the new torque-segmented arch (TSA)]

New torque-segmented arch wires are presented which consist of a superelastic anterior component with 30 degrees or 45 degrees torque and which are connected to 2 steel lateral components by means of a crimped connector. When using such torque-segmented arch wires, the crimped connector rests mesially to the canine bracket and the lateral components exhibit a torque of 0 degree. The use of the torque-segmented arch wires requires the practitioner to adjust the anterior tooth segment, to bend in first order bends in the steel lateral portion as well as to bend in a sweep to avoid an anterior tooth extrusion, and, if desired, to bend in third order bends to influence premolars and molars. In some cases the simultaneous application of palatal arches can become necessary, because each torque transfer results in a transversal enlargement in the molar area. Compared to conventional steel wires with dimensions of 0.016 x 0.022 in which an anterior tooth torque is bent, the torque segmented arch wires exhibit considerably fewer side effects, but there is a larger distally rotating moment for the molars. 1. When applying torque-segmented arch wires, the extrusive force transferred to the anterior teeth is considerably smaller. 2. The protrusive force acting on the anterior teeth is also considerably smaller, which results in a reduced demand being placed on the anchorage of the molars. 3. The torque transfer to the incisors rests in a quite moderate range, even in the case of a 50 degrees torque. For this reason, the practitioner can expect diminished or no resorptions at all compared to the aforementioned steel wires. 4. The Martensite plateau of the torque-segmented arch wires exhibit constant moments in large areas so that such arch wires can be used in almost every anterior tooth position. 5. The segmented wires presented here can be applied not only in the case of the standard edgewise technique but also in each case of the straight-wire technique. 6. These new arch wires require no readjustment of torque values. 7. To control the transferred torque values it is recommended that the already transferred torque values be monitored during each check-up with the help of the described torque key. 8. When the torque values of the brackets are known, the torque key renders frequent patient X-rays superfluous. 9. When the desired torque values are attained, treatment can proceed using conventional arch wires.

[Cervical headgear with angled outer arms. A biomechanically comprehensible system?]

When applying the angulated face bow, it doesn't seem possible to avoid vertical and transversal forces which occur in addition to the distalization force as moments. By varying the length and angulation of the outer bow, it is possible to influence the force components and the moments in the sagittal plane. In the clinical analysis of the force system it is assumed that the face bow is an ideal rigid system. Only under this presupposition is the assumption valid, that the product of the force and the perpendicular distance to the molar tube is responsible for the size of the moment. Under this assumption, however, all forces and moments created by the deflection of the headgear are not taken into consideration. An experimental analysis of the forces and turning moments which occur indicates that this simplifying geometric point of view does not always correspond to reality. It was evident, e.g., that there is no linear correlation between the force and moment in mesio-distal direction due to the deflection of the outer bow. This effect becomes the more obvious the longer the outer bow of the headgear is.

[Improvement in the adhesive strength of orthodontic brackets on unit-cast and fired dental alloys by microsandblasting]

This experimental study employed an Instron test machine to measure the bond strength of metal brackets to cast test specimens made of 6 different dental alloys. An easily replicated method for testing the shear bond strength is presented, which corresponds to the international recommendations for testing bond strength of orthodontic brackets. The study found that the different methods of surface preparation, such as micro-sandblasting and the use of chemical sealants, had distinct effects on the magnitude of bond strength gauged. Also tested was whether the storage medium prior to debonding influenced the bond strength. The measured values from a series of tested bovine teeth, which were bonded by means of the conventional acid etch method and with the same adhesive, served as a control group. An extended statistical analysis showed that the use of the methods described can achieve a clinically acceptable bond of brackets to dental alloys for prosthetic restorations.

[The shearing strength of titanium brackets depending on the coating procedure]

It has long been recognized that corrosion of the metal alloys used in the different fields of dentistry can cause intra-oral problems such as allergic reactions. Titanium, a metal all but impervious to corrosion, presents an alternative to the metal alloys used in the fabrication of orthodontic brackets. The purpose of this study was to test the bonding strength between titanium brackets treated with 5 different opaque and non-opaque coatings and a 2-phase adhesive. Five coating methods were tested: N1 (Dentaurum), N2 (Dentaurum), Rocatec (Espe), Sebond (Schütze), Silicoater Standard (Kulzer). After bonding the brackets with a mix adhesive, they were thermocycled and then the shear bonding strength established. Silicoated titanium bracket bases showed clinically acceptable bonding values with the exception of those coated with Sebond without opaquer layer. While the silicoating methods N1, N2, and Rocatec demonstrated minimum bonding strength using the opaquer Visio-Gem, the bonding strength of the bracket bases coated with Sebond MKV, Silicoater Standard and the opaquer appropriate to each was significant increased. Among all the coated surfaces, methods N1, N2, and Rocatec appear to establish the optimum bonding strength values. In addition, the thin opaquer layer (Visio-Gem) used together with these methods offers a good surface adaptation of the bracket to the tooth surface.

Molar distalization with bimetric molar distalization arches

The aim of this study was to observe the clinical and cephalometric effects of intra-oral distalization with the maxillary bimetric arches. 3 girls and 1 boy with a mean age of 13.5 years with Class II skeletal and dental relationship were selected. Care was taken to select patients having a normal vertical growth pattern. Lateral cephalograms were taken at the beginning and at the end of the distalization period, which was approximately 3 months. To observe the distal movement, a metal marker was attached to the distal end of the buccal tube of the first molar. On each lateral cephalometric radiograph a reference plane perpendicular to the occlusal plane and passing through the point Sella was drawn to assess the amount of distalization. Cephalometric measurements indicated that the upper molars moved approximately 3 mm distally and that the lower incisors were proclined.