An examination of the effects of levelingwith nickel titanium rectangular arch wires combined with torqued incisor brackets

Leveling the curve of Spee with sequential round cross-section arch wires characteristically results in incisor proclination. To prevent this, the use of low modulus, rectangular cross-section arch wires combined with torqued incisor brackets has been recommended by some clinicians. Clinical data were analyzed to determine whether this is the case. It showed that proclination does occur at a lesser angle and at a mean center of rotation more apical to that of the mean center of rotation resulting from leveling with successive round arch wires. A probability calculation suggests that in a random selection of 2 patients, in which patient 1 was treated by round wire leveling and patient 2 was treated by rectangular wire/torqued bracket leveling, the odds are approximately 2 to 1 in favor of patient 2 having more labial bone stressed than patient 1. This is primarily caused by the incisors' centers of rotation being displaced more apically. This negative effect is reduced somewhat by increase intercuspid canine width, a characteristic of low modulus nickel titanium rectangular arch wire forms. It should be noted, however, that earlier studies have shown that increased canine cross-arch widths potentiate posttreatment instability.     

Commentary: Biomechanical considerations in maxillary protraction therapy

Leveling the curve of Spee with sequential round cross-section arch wires characteristically results in incisor proclination. To prevent this, the use of low modulus, rectangular cross-section arch wires combined with torqued incisor brackets has been recommended by some clinicians. Clinical data were analyzed to determine whether this is the case. It showed that proclination does occur at a lesser angle and at a mean center of rotation more apical to that of the mean center of rotation resulting from leveling with successive round arch wires. A probability calculation suggests that in a random selection of 2 patients, in which patient 1 was treated by round wire leveling and patient 2 was treated by rectangular wire/torqued bracket leveling, the odds are approximately 2 to 1 in favor of patient 2 having more labial bone stressed than patient 1. This is primarily caused by the incisors' centers of rotation being displaced more apically. This negative effect is reduced somewhat by increase intercuspid canine width, a characteristic of low modulus nickel titanium rectangular arch wire forms. It should be noted, however, that earlier studies have shown that increased canine cross-arch widths potentiate posttreatment instability.     

Stability of mandibular incisors following excessive proclination: a study in adults with surgically treated mandibular prognathism

The purpose of this study was to determine if mandibular incisors could be proclined markedly without increasing the potential for relapse of crowding. Patients with surgically treated mandibular prognathism were selected. In 29 patients the mandibular incisors were proclined more than 10 degrees during the presurgical orthodontic phase. The remaining 33 patients had only minimal change in incisor inclination. A long-term follow-up examination was performed 10.0 (SD 2.3) and 11.1 (SD 3.1) years postoperatively in 26 and 24 patients, respectively. Study casts were measured before and after treatment, three years after surgery, and long-term. Cephalograms were evaluated before and after treatment, immediately before and after surgery, and three years after surgery. Prior to therapy the patients treated with presurgical proclination had less dental arch length and more retroclined and crowded mandibular incisors than the patients in the other group. No differences in parameters were observed at later intervals. Dental arch length and intercanine width decreased and incisor irregularity increased in both groups during the follow-up periods. No intergroup differences in changes were observed. Indications for proclination of mandibular incisors are discussed.     

A randomized clinical trial comparing mandibular incisor proclination produced by fixed labial appliances and clear aligners

Objective:To compare the mandibular incisor proclination produced by fixed labial appliances and third generation clear aligners.Materials and Methods:Patients underwent a course of orthodontic treatment using either fixed labial appliances or clear aligners (Invisalign). Mandibular incisor proclination was measured by comparing pretreatment and near-end treatment lateral cephalograms. Eligibility criteria included adult patients with mild mandibular incisor crowding (<4 mm) and Class I skeletal bases (ANB, 1–4°). The main outcome was the cephalometric change in mandibular incisor inclination to the mandibular plane at the end of treatment. Eligible patients picking a sealed opaque envelope, which indicated their group allocation, was used to achieve randomization. Data was analyzed using a Welch two-sample t-test.Results:Forty-four patients (mean age, 26.4 ± 7.7 years) were randomized in a 1:1 ratio to either the fixed labial appliance or the clear aligner group. Baseline characteristics were similar for both groups: Fixed appliance mean crowding was 2.1 ± 1.3 mm vs clear aligner mean crowding, 2.5 ± 1.3 mm; pretreatment mean mandibular incisor inclination for the fixed appliance group was 90.8 ± 5.4° vs 91.6 ± 6.4° for the clear aligner group. Fixed appliances produced 5.3 ± 4.3° of mandibular incisor proclination. Clear aligners proclined the mandibular incisors by 3.4 ± 3.2°. The difference between the two groups was not statistically significant (P > .05).Conclusion:There was no difference in the amount of mandibular incisor proclination produced by clear aligners and fixed labial appliances in mild crowding cases.     

Reduced mandibular cast splints an alternative in Herbst therapy? A prospective multicentre study

The aim of this study was to analyse anchorage loss with reduced, in comparison with total mandibular cast splints during Herbst treatment. Lateral head films of 32 Class II division 1 patients (15 females, 17 males) aged 13.0 years with reduced mandibular cast splints (RMS: second premolar to second premolar) and of 34 Class II division 1 patients (19 females, 15 males) aged 13.9 years with total mandibular cast splints (TMS: molar to molar) were analysed before (T1) and directly after (T2) Herbst treatment. Anchorage loss was assessed considering mandibular incisor proclination, changes of lower incisor edge position, and changes of occlusal plane inclination. To assess possible group differences, Student's t-tests were applied. The lower incisors proclined more in the RMS (11.8 degrees) than in the TMS (9.3 degrees) group. However, the amount of incisal edge advancement was less in the RMS (2.9 mm) than in the TMS (3.7 mm) group. The occlusal plane tilted insignificantly less in the RMS (5.7 degrees) than in the TMS (6.3 degrees) group. Reduced and total mandibular casted splint anchorage seemed to be similarly effective. Anchorage loss, measured by mandibular incisor proclination, was greater in the reduced anchorage group, whereas measured by lower incisor edge advancement, it was larger in the total anchorage group. Therefore, RMS can be recommended for Herbst treatment since they are less expensive than total splints.     

Efficiency of root torquing auxiliaries

In an experimental typodont study simulating the third stage of Tip-Edge treatment, the effect of five torquing auxiliaries on upper four incisors was assessed using the method of laser reflection. The auxiliaries analysed were: (1) Two-Spurs 0.016", (2) Four-Spurs 0.016", (3) Reciprocal Lateral Torque 0.016", (4) Torque Bar 0.022x0.018", 20 degrees, and (5) Torque Bar 0.022x0.018, 30 degrees. When comparing the wires, the efficiency (amount and speed of root tipping) varied considerably: (1) The Two-Spurs wire was the most efficient auxiliary of the five tested and showed good torque effect on the central incisors. (2) The Four-Spurs wire acting on all four incisors was less efficient than the Two-Spurs wire. (3) The Reciprocal Lateral Torque wire exhibited good palatal root torque on the central incisors and labial root torque on the lateral incisors. (4) The Torque Bars (20 degrees and 30 degrees ) were the least efficient wires of the auxiliaries tested and showed only small torque effects on the central and lateral incisor teeth. In clinical work using the Tip-Edge technique, the Two-Spurs torquing auxiliary should be the wire of choice for an efficient palatal root torque of the upper central incisors.     

Lower incisor torque: the effects of rectangular archwires with a reverse curve of Spee

The relationship between the Curve of Spee in a rectangular archwire and torque in the lower labial segment is discussed. It is concluded that introducing a reverse curve in the archwire does not necessarily have any adverse effects on final lower incisor inclination.     

Correlation between mandibular central incisor proclination and gingival recession during fixed appliance therapy

The purpose of this study was to determine whether proclination of mandibular central incisors during fixed appliance therapy results in gingival recession. Complete records of 67 patients (39 female and 28 male patients; mean age, 16.4 years; age range, 10-45 years) were used in this retrospective case-control study. Using pretreatment and posttreatment lateral cephalograms, the change in mandibular central incisor inclination was measured to divide the patients into an experimental group (proclination) and a control group (no proclination). Changes in clinical crown length were determined from pretreatment and posttreatment study models, and changes in gingival recession were determined from intraoral slides. Eight of the 67 patients exhibited a measurable increase in gingival recession of at least 0.5 mm, and 27 patients had an increase in clinical crown length of at least 0.5 mm. Statistical analyses showed no correlation between mandibular central incisor proclination and gingival recession or clinical crown length. A t-test analysis showed no statistically significant difference in gingival recession or change in clinical crown length between patients whose mandibular central incisors were proclined and those whose incisors were not proclined. Multiple regression analysis demonstrated that age, sex, race, treatment duration, extraction, treatment type, Angle classification, and proclination were not related to gingival recession or change in clinical crown length of mandibular central incisors. We conclude that the degree of proclination of mandibular central incisors during fixed appliance therapy was not correlated to gingival recession in this sample.     

Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics.

The aim of this study was to evaluate cephalometrically the effects of open bite treatment with NiTi arch wires and anterior elastics. The study group comprised of 17 patients who displayed a high angle skeletal pattern, along with an anterior open bite. After initial leveling, 0.016 x 0.022 inch upper accentuated-curve and lower reverse-curve arch wires were placed, with anterior elastics applied in the canine regions. Cephalometric assessment was carried out on lateral head films taken at the beginning of treatment and on average 2.8 months after open bite closure was obtained. The results of this study indicated that open bite closure had been achieved mainly by extrusion of the lower incisors and uprighting of the upper incisors. The functional occlusal plane was leveled by extrusion of lower premolars and uprighting of lower molars. Lateral cephalograms obtained from 10 patients who had been available after 1 year postretention were used to evaluate relapse changes. During the follow-up period, position of the upper and lower incisors and the inclination of the occlusal plane were maintained. However, extrusion of upper and lower molar teeth resulted in a reduction in overbite.     

Predictors of outcome among patients with class II division 1 malocclusion treated with fixed appliances in the permanent dentition.

This retrospective study investigated the outcomes achieved in 212 consecutively completed patients with Class II Division 1 malocclusion (overjet > 6 mm). All patients were treated in the permanent dentition with upper and lower fixed appliances. A composite outcome measure was used to identify those cases with an excellent outcome (posttreatment PAR 相似文献   

Lower Incisor Torque: The Effects of Rectangular Archwires with a Reverse Curve of Spee

Abstract

The relationship between the Curve of Spee in a rectangular archwire and torque in the lower labial segment is discussed. It is concluded that introducing a reverse curve in the archwire does not necessarily have any adverse effects on final lower incisor inclination.     

A comparative study between the effect of reverse curve of Spee archwires and anterior bite turbos in the treatment of deep overbite cases:: A randomized clinical trial

ObjectivesTo compare deep overbite treatment using 0.016 × 0.022 nickel-titanium lower reverse curve of Spee archwire (LRCA) or metal anterior bite turbos (ABTs).Materials and Methods48 patients with deep overbite malocclusion were randomly allocated into two groups. Group I (age = 18.4 ± 2.8 years, overbite = 5.8 ± 0.6 mm) was treated with LRCA, while Group II (age = 18.2 ± 3.1 years, overbite = 5.2 ± 0.4 mm) was treated with ABTs bonded to the palatal surface of the upper central incisors. Two cephalograms were taken for each patient, at post-alignment stage (T1) and post-leveling stage (T2). The primary outcomes were the anteroposterior and vertical changes of the lower teeth. The secondary outcomes were the effect on upper incisor inclination and the vertical linear changes of upper teeth, to assess the sagittal and vertical skeletal changes, and to compare the duration of overbite correction.Results42 of the 48 patients recruited completed the study (21 in each group). At T2, the lower incisors proclined more in Group I (P ≤ .001). Both lower second molars (P ≤ .001) and lower first molars (P = .001) tipped more distally, while the lower first premolar tipped more mesially, in Group I (P < .05). All cusps of both lower molars showed more extrusion in Group II (P < .05) except for the mesial cusp of lower second molars (P = .095). The duration of overbite correction was shorter using the ABTs by 1.7 months (4.85 ± 1.56 and 3.15 ± 0.93 months for Group I and Group II, respectively).ConclusionsLRCA causes lower incisor proclination with distal tipping of lower molars, while ABTs result in lower posterior tooth extrusion.     

Eruptive changes in the axial inclination of lower incisor teeth--a longitudinal study

A longitudinal cephalometric study investigated the change in lower incisor inclination in a group of 32 subjects over a period from 5-10 years of age, with yearly cephalometric radiographs and 6 monthly study models. In a previous study, it was shown that in all of these subjects, the lower incisors became more proclined over this 5 year period. Changes in the rate of proclination of the lower incisors over this period were studied, and this was related to events such as eruption, and contact with the upper incisors or palatal mucosa where this occurred. The association between the inclination of lower incisors before and just after eruption, and their "final" inclination was investigated, and the possible explanations and implications of the findings are discussed.     

Factors that influence the proclination or retroclination of the lower incisors in children with prolonged thumb-sucking habits

In some children with a prolonged finger-sucking habit, the lower incisors are retroclined, however, proclination of the lower incisors has been frequently observed. The purpose of this study was to determine how such differences develop in the child with a digit-sucking habit. Children with a prolonged thumb-sucking habit and proclination of the lower incisors (Ili/ML > 97 degrees) were cephalometrically and clinically compared to persistent thumb-suckers with retroclined lower incisors (Ili/ML < 89 degrees). In the group with retroclined lower incisors the angle between the thumb and the lower incisors was significantly smaller and the thickness of the lower lip significantly thinner than in the group with proclined incisors. A higher frequency of early loss of deciduous molars was also observed in the group with retroclined incisors. The tightness of the lower lip, early loss of deciduous molars and the angle between the teeth and the thumb are factors which have been identified to influence the inclination of the lower incisors in persistent digit suckers. The majority of children with prolonged thumb-sucking have proclined lower incisors rather than retroclined lower incisors.     

Herbst treatment with mandibular cast splints—revisited

Objective:The objective of this study was to reassess the dento-skeletal treatment effects and the amount of anchorage loss during reduced mandibular splint (RMS) Herbst treatment.Materials and Methods:One hundred consecutive Class II patients treated with a RMS-Herbst appliance were analyzed. The mean pretreatment age of the patients was 14.5 years, and the mean treatment time with the Herbst appliance was 8.1 months. Both before (T1) and after (T2) Herbst treatment a cephalometric measurement of lower incisor inclination, a sagittal occlusion analysis, and a dental cast analysis were performed. A comparison was performed with a historic Herbst control group treated with total mandibular cast splints (TMS).Results:During treatment the lower incisors proclined markedly (12.9° ± 4.6°). The amount of incisor proclination in the RMS group was, on average, 3.6° larger (P < .001) than in the TMS group. The lower incisor proclination increased from 11.9° (prepeak) to 14.3° (young adult). The level of professional experience of the practitioners performing the treatment did not influence the amount of incisor proclination significantly. The total available space in the lower arch increased by an average of 1.8 mm, and a space opened between the lower second premolars and lower permanent first molars in 62% of the present RMS-Herbst (average of 0.4 mm per side).Conclusions:Treatment with RMS-Herbst appliances leads to higher proclination of the lower incisors than does treatment with TMS-Herbst appliances; it also leads to an overall larger amount of anchorage loss.     

The orthodontic management of vertical deficiencies in the Alexander discipline

Although there are several different approaches to treating vertical deficiencies,the Alexander Discipline is an efficient and effective technique to manage this group of malocclusions. Patient compliance is important because most of these treatments will require orthopedic appliances. Appropriate bracket selection and placement for maxillary arch development is essential. Specific arch wire designs incorporating a curve of Spee are used. The mandibular arch is then treated, focusing on torque control of the lower incisors while using a reverse curve of Spee in the tied-back arch wires and a bite plate if necessary. The ideal arches are then coordinated with various elastics as needed. Retention is then instituted.     

Long-term effect of the chincap on hard and soft tissues.

The short- and long-term effects of the chincap used in combination with a removable appliance to procline upper incisors were analysed cephalometrically in 23 patients with Class III malocclusions. The overall changes were compared with growth changes in a closely matched control sample of untreated Class III patients. There was no evidence that the chincap retarded growth of the mandible. During treatment, there was an increase in mandibular length and facial height. The lower incisors retroclined and the upper incisors proclined. The incisor relationship was corrected. Soft tissue changes included an increase in nasolabial angle and improvement in soft-tissue profile, including the nose. Skeletal post-treatment changes included further mandibular growth associated with an increase in angle SNB and Wits measurement. Facial height also increased significantly. The Class I overjet was maintained, although slightly diminished. The soft tissue nose, upper and lower lip, and chin moved anteriorly, and the nasal tip and chin moved inferiorly. At the end of the study period there were no significant skeletal or soft tissue differences between the treated and control groups. The only significant contrasts were in the overjet and the overbite. Chincap therapy combined with an upper removable appliance to procline the upper incisors is effective in producing long-term correction of the incisor relationship by retroclination of lower incisors, proclination of upper incisors, and redirection of mandibular growth in a downward direction. The direction of growth at the chin is maintained subsequent to treatment, as are the changes in incisor inclination, although in diminished form. There are corresponding improvements in the soft tissue profile.     

Vertical forces in labial and lingual orthodontics applied on maxillary incisors--a theoretical approach

Theoretical and experimental biomechanical analyses explain most labial orthodontics (LaO); however, lingual orthodontic (LiO) biomechanical principles are rarely introduced. The objective of this study was to apply basic biomechanical considerations in understanding the influence of maxillary incisor inclination and to compare the effect of labial vs lingual intrusive/extrusive forces on tooth movement. Basic anatomic and geometric hypotheses were assumed, ie, tooth length (crown and root), location of the center of resistance, and crown thickness. Incisor inclination as related to a perpendicular line to the occlusal plane (OP) varied between -35 degrees (retroclination) and 45 degrees (proclination). A 0 degrees inclination was defined as a tooth position with its long axis perpendicular to the OP. The buccolingual moment for characterizing root movement was calculated for an applied force perpendicular to the OP. The results showed that when using LaO, an extrusion force resulted in labial root movement from a retroclination of 20 degrees up to a proclination of 45 degrees. In LiO, labial root movement occurred only when the tooth was proclined more than 20 degrees. In all other tooth inclinations, lingual root movement occurred. The opposite tooth movement occurred when an intrusive force was applied. Application of a vertical force has different clinical effects on tooth movement with labial and lingual appliances. Application of a lingual force is more complicated, and its effect on tooth movement depends on bracket position and initial tooth inclination.     

直丝弓排齐与整平阶段切牙唇倾和支抗的研究

目的 直丝弓拔牙矫治技术在排齐与整平阶段牙齿易出现切牙唇倾,临床上常采取尖牙向后８字结扎和末端弓丝回弯的措施来预防,对其效果进行实验研究。方法 ２６例拔除４颗第一双尖牙的病例,使用国产Ｒｏｔｈ数据直丝弓矫治器进行矫治,采取上述措施并且上颌加横腭杆,进行Ｘ片头影测量和统计分析。结果 上切牙牙轴无明显变化,下切牙直立,切牙水平位置没有明显移动;上下磨牙平均约前移１ｍｍ,但是相对于Ｂｅｇｇ和方丝弓矫治器     

固定矫治器中切牙转矩的控制

目的　探讨切牙转矩定量的控制规律。方法　使用转矩测量仪 ,对横截面积为 0 4 6mm× 0 6 3mm的平直不锈钢丝与钛镍丝 ,7 0mm高垂直曲不锈钢丝 ,3 0mm长和 6 0mm长L形水平曲不锈钢丝 ,在单个 0 5 6mm中切牙托槽内的转矩力矩与扭转角度进行测量与分析。结果　(1)这些弓丝的抗扭刚度分别为 4 90 9、1 32 5、4 137、3 4 4 8和 3 0 2 4N·mm/度 ;(2 )转矩力矩达到2 0N·mm时 ,上述弓丝将分别扭转 19 14 3、36 832、19 85 1、2 1 812和 2 2 4 18度 ;(3)不锈钢丝和钛镍丝的转矩余隙角分别为 15 0 7度和 2 1 73度 ;(4)曲能起到降低不锈钢丝的抗扭刚度、增加弓丝弹性范围的作用 ,其中以水平曲的效用更优。结论　平直不锈钢丝不是控制切牙转矩的理想选择。曲 ,特别是水平曲 ,能显著降低弓丝的转矩刚度、增加弓丝弹性范围