Effect of double chain method on the closure of orthodontic teeth / 解剖学报

Objective To study the safety and effectiveness of the double chain method on the closure of the space of the teeth. Methods Totally 72 cases of different maxillary and mandible dentition space were included in the study. The pulp vitality was measured before and after treatment, the maxillary and mandible first molar teeth. All values were compared to assess the safety of dental pulp vitality. There were 36 cases in tooth extraction group and non-tooth extraction group.The observation period was 4 weeks, the changes of the alveolar space between maxillary and mandible teeth in adult and minor groups were measured before and after treatment. The difference of the total groove spacing before and after treatment were calculated and compared, to assess the effectiveness of space closure. Results In all 72 patients, there was no significant difference in the vitality of the pulp before and after treatment (P>0. 05). Compared to before treatment, the sum of the distance between the upper and lower mandibular groove using the double chain method was significantly reduced for both adult and juvenile patients in the four week tooth extraction group and the nontooth extraction group,the difference was statistically significant (P<0. 05). Conclusion Double chain closed teeth space does not cause pulp degeneration and necrosis. It is safe in clinical practice. Double chain method is effective, and can simplify the clinical operation.

Comparison between transmission technique and MBT straight wire technique in correction of protruding in adults / 中华医学美学美容杂志

Objective To evaluate the curative effect by using transmission straight wire appliance in treatment of adult patients with protruding,to compare with MBT straight wire technique,and to discuss their similarities and differences.Methods Totally 40 protruding patients were assigned into two groups randomly:the transmission straight wire technique group were treated with transmission straight wire appliance,and the MBT straight wire technique group were treated with MBT appliance together with extraoral arch or screw implant anchorage.Cephalometric measurements were compared before and after treatment.Results Average period of treatment was (19 ±4) months for transmission group and (23 ± 4) months for MBT group.The difference was statistically significant (P＜0.05).After treatment,U1/SN,U1/NA,U1-NA,L1/NB,L1-NB,U1-AP,L1-AP,UL-EP,LL-EP were significantly reduced for both patients groups (P＜0.01).U1/L1,nasolabial angle and z angle were increased for both groups (P＜0.05).MP/SN increased by 1.93°(P＜0.05)for transmission group vs.0.81° (P＞0.05) for MBT group.There was no statistically significant difference between the two groups (P＞0.05) except MP/SN (P＜0.05).However,the retraction of anterior teeth in transmission group was greater than that of MBT group,and U1/NA changed (-20.95±8.79)° in transmission group vs.(-16.00 ± 6.52)° in MBT group.Conclusions Both techniques can achieve satisfactory results for protruding cases.The transmission technology can improve soft tissue profile quicker,but anterior teeth have excessive vertical trend,where attention should be paid to control torque on anterior teeth.

Twin Block appliance combined with straight wire appliance used in cor-recting Angle Ⅱmalocclusion / 中国现代医生

Objective To investigate the efficacy of Twin Block appliance combined with straight wire appliance in the correction of AngleⅡ malocclusion. Methods Sixteen patients with Angel Ⅱ malocclusion were selected. Twin Block appliance combined with straight wire appliance was used for correction without tooth extraction. The lateral films of head were shot before and after treatment in order to conduct X-ray cephalometric analysis. Results All patients com-pleted active corrective treatment within (18±2.0) months. After treatment, the lower jaw moved forward and the classⅠ molar-canine relationship was established. Normal overbite and cover was obtained. The patients with lower mandible retrusion achieved obvious corrective effects and their appearance improved. After treatment, X-ray cephalo-metric analysis showed that SNB increased by 3.25° on average, SNA remained the same, ANB reduced by 6.50° on av-erage, IMPA reduced by 6.95° on average, FMIA increased by 3.61° on average, FMA increased by 2.53° on average, Po-Co increased by 5.12 mm on average, and Vits reduced by 1.29 mm on average(P<0.05). Conclusion In the correc-tion of early Angle Ⅱ malocclusion, Twin Block functional appliance combined with straight wire appliance shows evi-dent effects and patient satisfaction, thereby worthy of clinical promotion.

A clinical study on the effect of maxillary incisor torque with controlling root auxiliary arch / 实用口腔医学杂志

Objective:To explore the torque effect of controlling root auxiliary arch on the straight wire appliance on maxillary anterior teeth.Methods:22 patients with class Ⅱ1 extraction treatment,treated with straightwire appliance,at the detailing treatment stage were treated with controlling root auxiliary arch over the erect or introverted maxillary incisors for positive torque.The main arch wire of 0.46 mm ×0.64 mm stainless steel edge wire was used in 14 cases,the main arch wire of 0.46 mm stainless steel round wire was used in 8 cases.Cephalometric results before and after maxillary incisor torque were analyzed by t test.Results:After maxillary incisor torque in the 22 cases 1-SN and UIa-NA value increased(P ＜0.01),positive torque was achieved by controlling root auxiliary arch on the upper incisors;the round wire maxillary incisor torque worked faster than the edge wire(P ＜0.05).Conclusion:At the detailing stage of treatment straight wire appliance on front teeth,controlling root auxiliary arch is simple and effective in the treatment of exces-sive erect or lingual inclination of maxillary incisor.

Biomechanical modeling of dentulous mandible-straight wire appliance / 医用生物力学

Objective To establish the model of dentulous mandible and straight wire appliance and investigate the stress and displacement distributions of the roots and periodontal tissues under en masse space closure with sliding mechanics. Methods The three-dimensional finite element model of mandible and teeth was developed from CT images, which consisted of the dentin, enamel, dental pulp, PDL (periodontal ligament), cortical and cancellous bone. The models of Roth straight wire brackets with actual data were also constructed. The dental adhesives were used to stick the brackets on the corresponding teeth. Contact elements were used to simulate the interaction between the stainless steel arch wire and the brackets. Moreover, spring elements were used to connect the brackets and the arch wire. The load with the value of 1 N was applied on the model to close the space. Results The lingual tipping of lateral and central incisors was found, corresponding with the clinical observation of en masse space closure with sliding mechanics. High stress in the teeth and periodontal tissue appeared at the incisors and the distal roots of the first molars. The maximum von Mises stresses in PDL of the central incisors and the distal roots of the first molars were 3.97 kPa and 5.75 kPa, respectively. Conclusions In order to avoid root resorption of incisors, the torque of the brackets could be increased. Less orthodontic forces or orthodontic implant could be used to avoid distal roots of first molars.

Labial and buccal surface contours of Korean normal occlusion in a three-dimensional digital model / 대한치과교정학회지

OBJECTVIE: This study was performed to investigate the labio/buccal clinical crown curvatures of Korean permanent teeth and to obtain the curve-ratio data in an attempt to fabricate bracket bases fit for each individual Korean permanent tooth. METHODS: Three-dimensional digital models were made from 30 sets of dental casts with normal anatomic structures. According to the FA points, horizontal and vertical reference planes were established and lines were drawn on the tooth surfaces in reference to these planes. The curvature was expressed as the coefficient of a quadratic equation. Lines mesial, distal, gingival and occlusal to the horizontal, vertical reference planes and the FA point were drawn. RESULTS: The curvature measured for each line revealed that there are no significant differences between male and female, except for maxillary canines and maxillary second bicuspids (p > 0.05). There were notable differences in the mesio-distal or gingivo-occlusal curvatures among the mandibular lateral incisors, maxillary canines, maxillary and mandibular first and second bicuspids and first molars (p < 0.05). CONCLUSIONS: The labial & buccal crown curvatures of teeth in Korean normal occlusion were measured on the mesial and distal, gingival and occlusal sides respectively in this study. Based on these data, a SWA can be developed to fit the individual features of Korean tooth crowns.

Transmission straight wire appliance treats Angle Ⅱ 1 malocclusion:report of 13 cases / 第三军医大学学报

Objective To observe the clinical effects of transmission straight wire appliance on the treatment of AngleⅡ1 malocclusion and explore its mechanism.Methods Thirteen AngleⅡ1 malocclusion patients (6 males and 7 females) were treated with the appliance by extracting 4 first premolars or 2 first maxillary premolars.The results of cephalometric measurements before and after treatment were statistically analyzed.Results The average treatment time of 13 cases was 15.6 months.The overbite's treatment cost 4.2 months averagely.Overbite,overjet and molar relationship were turned to normal (only one adult case had complete distal in the molar relationship by extracting 2 first maxillary premolar) and lateral appearances were improved after treatment.The results of cephalometric analysis showed that the changes of SNB,ANB,U1-NA angle,L1-NB angle,U1-LI angle,U1-NA length,L1-NB length,L6-MP length,L1C-MP length,overbite,and overjet were of high statistical significance (P0.05).Conclusion Transmission straight wire appliance can quickly and efficiently correct AngleⅡ1 malocclusion.

A study for the development of the Korean orthodontic bracket / 대한치과교정학회지

The aim of this study was development of the Straight-Wire Appliance(SWA) suitable for the treatment of Korean. To accomplish the object of this study, Korean adult with normal occlusion were selected with following criteria: 1) no functional abnormality in the craniofacial area, 2) good dental arch form and posterior occlusal relationship, 3) Angle Class I occlusal relationship, 4) no experience of orthodontic, nor prosthodontic treatment, especially, no dental treatment on labial and buccal surfaces of teeth, 5) good facial profile. Impression were taken for upper and lower dental arches of the selected normal occlusion samples and the orthodontic dental stone models were fabricated. 5 well-trained orthodontists had examined the acquired dental stone models to select study samples which satisfy the Six keys to optimal occlusion of Andrews. 155 pairs of dental stone models (92 pairs of Male, 63 of Female) were finally selected. 3 dimensional digitization were performed with the Coordinate Measuring Machine(CMM, MPC802, WEGU-Messtechnik, Germany) and measuring of Angulation, Inclination, In-and-Out, Molar offset angle and Arch form were accomplished with a measuring software to achieve data for the development of SWA. Before the measurement, error study was performed on the 3 dimensional digitization with CMM, and the analysis of reliability of computerized measuring method adapted in this study and conventional manual method presented by Andrews was performed. Results of this study were as follows: 1. Equi-distance digitization with mesh size 0.25 mm, 0.5 mm and 1.0 mm were acceptable in 3 dimensional digitization of dental stone model with the CMM, and the digitization with 1.0 mm mesh size was recommendable in terms of efficiency. 2. Computerized measuring method with 3 dimensional digitization was more reliable than manual measuring method of Andrews. 3. Data were collected for the development of SWA suitable for the morphological characteristics of Korean with the computerized measuring method with 3 dimensional digitization.

Crown angulations of posterior teeth of normal occlusion measured from marginal ridge plane / 대한치과교정학회지

In the previous studies about prescription of preadjusted appliance, occlusal plane was used as a reference plane for crwon angulation (tip) measurement But this reference plane is not parallel to the he connecting the facial axis points at which the centers of brackets are positioned (Andrews' plane), due to the curve of Spee. Therefore, we developed a new reference plane unaffected by the curve of Spee and more parallel to the Andrews' plane. It is an imaginary line connecting mesial and distal marginal ridges of each posterior tooth, and we named it 'marginal ridge plane'. In this study, crown angulations of posterior teeth of 29 normal occlusion samples were measured and measurements from both reference planes were compared. Crown angulation measurements measured from occlusal plane were different from crown angulation measurements from marginal ridge plane in the upper and lower 2nd molars (p<0.01), and 1st premolars (p<0.05). These results were analyzed as the crown angulation measurements from occlusal plane were affected by the curve of Spee. Crown angulations should be vaned according to the amount of curve of Spee to maintain- the continuity of marginal ridges. To solve this problem, determining bracket angulation as the bracket slot is parallel to the marginal ridge plane of each posterior teeth is recommended.

Clinical consideration on using the elastic "tie backs" during space closure / 대한치과교정학회지

Preadjusted appliance, following the original concept of the Andrews Straight-Wire appliance, became increasingly common in the 1980s. In six phases of treatment, anchorage control, leveling and aligning, overbite control, overjet reduction, space closure, and finishing are very effective with using the preadjusted appliances. Space closure is the phase of treatment in which the difference between standard edgewise and preadjusted mechanics is most noticeable. Orthodontists have been able to reduce the use of closing loops and, because of the level slot lineup, enjoy the advantages of sliding mechanics. In 1990, Dr. John C. Bennett and Richard P. McLaughlin introduced the new space closure system, namely, elastic "tiebacks". They found an .019"X.025" working archwire most effective in an .022"-slot system. Hooks of .024" stainless steel or .028" brass wire are soldered to the upper and lower archwires. The force required for space closure is delivered by elastic "tiebacks". An elastic module stretched by 2-3mm(to twice its normal length) usually delivers 0.5-1.5mm of space closure per month. Group movement and sliding mechanics are combined for gentle, controlled space closure, so that about 0.5mm of incisor retraction and 0.5mm of mesial molar movement can be seen each month. The tiebacks are replaced every four to six weeks. By using the elastic "tiebacks", the next two cases were treated during space closure. Even though we found some clinical problems of this mechanics, long treatment time, hard to control of vertical dimension and anchorage, the application method of this system is so simple that orthodontists can manage many patients during short chair time. But we must apply this mechanics after perfect understanding of the biomechanics in tooth movement.