Biomechanics of a modified Pendulum appliance--theoretical considerations and in vitro analysis of the force systems

The aim of this study was to analyse the acting forces and moments induced by a special orthodontic appliance, the Pendulum K, for molar distalization in the transverse and sagittal planes. The purpose-designed test set-up (artificial maxilla with anchorage unit and two electrothermodynamic molars, an electronic measuring unit, a unit with force-moment sensor, an analogue/digital converter, and a data read-out unit) allowed simulation of in vivo conditions on the one hand and precise determination of the force systems on the other. The appliances investigated were three specimens of the Pendulum K. In vitro measurement of the resulting force systems revealed that the forces and moments in the transverse and sagittal planes remained almost constant over a 3 mm measuring increment when the distal screw was continuously activated (10 activations/mm). Without reactivation of the incorporated distal screw, however, a marked decline in the force systems was recorded. The Pendulum K allows translatory distalization of the upper molars and thus dental arch expansion, dispensing with the need for permanent teeth to be extracted, subject to a corresponding indication. This is achieved by continuous adjustment of an incorporated distal screw and by specific pre-activations of the Pendulum springs.     

Molar Distalization with Different Pendulum Appliances: In Vitro Registration of Orthodontic Forces and Moments in the Initial Phase

Abstract. Aim: Registration of the orthodontic forces and moments acting with different types of pendulum appliance for non-compliance upper molar distalization in an in vitro study. Material and Methods: The purpose-designed test set-up comprised the following components: artificial maxilla with anchorage unit and two electrothermodynamic (ETD) molars, electronic measuring unit for temperature control and regulation, and a sensor unit with force-moment sensor, analog/digital converter and data readout unit. This set-up permitted virtually authentic simulation of in vivo conditions on the one hand and precise determination of the force systems on the other.The appliances investigated were the standard pendulum appliance with U-loop activation according to Hilgers and with uprighting activation according to Byloff, the M-pendulum with U-loop activation according to Scuzzo, and the Pendulum K with initial uprighting activation, toe-in bend and incorporated distal screw according to Kinzinger. Results and Conclusions: The effects shown by the standard pendulum appliance and the M-pendulum over a 3 mm simulated distalization increment were a marked decrease in the distally directed forces, and an increase in the intrusive and palatally directed forces as well as in the distoinclinatory, mesially inward, and palatally rotating moments.Activations in the U-loop region of the pendulum springs induced an increase in distally and buccally directed forces and in uprighting and buccally rotating moments as well as a marked rise in extrusive forces. Whereas the activation described by Hilgers led to mesially outward rotating moments, activation according to Scuzzo resulted in a further increase in the mesially inward rotating moments.In the measured standard pendulum appliances, uprighting activation at the end of the pendulum according to Byloff led to an increase in distally and buccally directed as well as in mildly intrusive forces, and to an increase in uprighting as well as in buccally and mesially outward rotating moments.With the Pendulum K according to Kinzinger, the initial toe-in bend and uprighting activation in the region of the end of the pendulum spring together with regular adjustment of the incorporated distal screw permitted virtually translatory molar distalization: constantly distalizing forces with slight intrusive, buccally directed, and rotating side effects.     

摆形矫治器远移磨牙的矢状方向分析

目的本研究在矢状方向上分析摆形矫治器远移上磨牙的效果及对支抗前磨牙、切牙的交互作用。方法选择14例安氏Ⅱ类错、上牙弓I-Ⅱ°拥挤患者,应用摆形矫治器远移上颌第一磨牙,每一病例治疗前后进行头影测量分析比较。结果14例患者在17.5±7周内上第一磨牙远移3.18±1.62mm,伴有前磨牙1.42±1.16mm、切牙0.97±0.45mm的近中移动,同时注意到上磨牙的远移、第二前磨牙与切牙的近移均是倾斜移动,统计分析显示各评估对象在治疗前后具有显著性差异。结论摆形矫治器是一种简便、对患者依赖少的上磨牙远移装置,可在临床中广泛应用。     

Pendulum and modified pendulum appliances for maxillary molar distalization in Class II malocclusion – a systematic review

Objective: The main purpose of the present systematic review was to evaluate the quantitative effects of the pendulum appliance and modified pendulum appliances for maxillary molar distalization in Class II malocclusion.

Materials and methods: Our systematic search included MEDLINE, EMBASE, CINAHL, PsychINFO, Scopus and key journals and review articles; the date of the last search was 30 January 2017. We graded the methodological quality of the studies by means of the Quality Assessment Tool for Quantitative Studies, developed for the Effective Public Health Practice Project (EPHPP).

Results: In total, 203 studies were identified for screening, and 25 studies were eligible. The quality assessment rated four (16%) of the study as being of strong quality and 21 (84%) of these studies as being of moderate quality. The pendulum appliances showed mean molar distalization of 2–6.4?mm, distal tipping of molars from 6.67° to 14.50° and anchorage loss with mean premolar and incisor mesial movement of 1.63–3.6?mm and 0.9–6.5?mm, respectively. The bone anchored pendulum appliances (BAPAs) showed mean molar distalization of 4.8–6.4?mm, distal tipping of molars from 9° to 11.3° and mean premolar distalization of 2.7–5.4?mm.

Conclusions: Pendulum and modified pendulum appliances are effective in molar distalization. Pendulum appliance with K-loop modification, implant supported pendulum appliance and BAPA significantly reduced anchorage loss of the anterior teeth and distal tipping of the molar teeth.     

Anchorage quality of deciduous molars versus premolars for molar distalization with a pendulum appliance.

PURPOSE: The aim of this study was to assess dental anchorage qualities when the pendulum appliance is used for distal molar movement. MATERIAL: Thirty adolescents in various dentition stages received a modified pendulum appliance with a distal screw and a specially preactivated pendulum spring for bilateral molar distalization in the maxilla. The subjects were subcategorized into 3 groups of 10 according to the dental anchorage used: deciduous molars, premolars and deciduous molars, or only premolars. Dentoalveolar effects and side effects in the anchorage unit and in the molar area were determined by cephalometric analysis. RESULTS: Statistical analysis of the measurements showed significant differences between groups in the extent of molar distalization and the resulting incisor protrusion. Distal tipping of the 6-year molars was significantly less severe (2.3 degrees +/- 1.58 degrees to the palatal plane and 2.55 degrees +/- 1.52 degrees to the anterior cranial base) in patients with premolar anchorage than in those with deciduous molar anchorage (6.15 degrees +/- 3.42 degrees and 6.35 degrees +/- 3.46 degrees ). Incisor protrusion was significantly more pronounced in patients with deciduous molar anchorage (2.75 +/- 1.4 mm) than in the other 2 groups (1.65 +/- 0.82 mm, mixed deciduous molar and premolar anchorage, and 1.75 +/- 0.75 mm, premolar anchorage). Additionally, incisor protrusion was translatory compared with controlled tipping in subjects with deciduous molar anchorage or premolar and deciduous molar anchorage. CONCLUSIONS: Deciduous molars and premolars can be used for anchorage for molar distalization with a pendulum appliance; however, anchorage with premolars only results in the least pronounced dentoalveolar side effects. The anchorage quality of deciduous molar and mixed deciduous molar/premolar anchorage is limited.     

Biomechanics of a Distal Jet appliance. Theoretical considerations and in vitro analysis of force systems

OBJECTIVE: To analyze the forces and moments acting in the first molar region, induced by the Distal Jet appliance for maxillary molar distalization. MATERIALS AND METHODS: Over a working section of 3 mm with reactivation of the loaded spring systems, the force systems of three laboratory-fabricated appliances of identical design were analyzed with a 3D metering device. RESULTS: The force systems registered in vitro exhibited complex biomechanics. Regular reactivation of the loaded coils resulted in consistent distalizing forces and uprighting moments, in forces and moments toward buccal as well as slightly intrusive forces, and mesial-inwardly rotating moments. In the sagittal dimension, the Distal Jet appliance allows almost translatory molar distalization. Accordingly, applying uprighting activation is not necessary for treatment. Because of the application of the force palatal to the center of resistance of the molars, the teeth experience undesired mesial-palatal and distal-facial rotation. CONCLUSIONS: The Distal Jet appliance allows almost translatory distal molar movement, and uprighting activation is not necessary for treatment. The force applied palatal to the center of resistance of the molars produces an undesired mesial-palatal and distal-facial rotation. Regular intraoral coil spring reactivation is needed.     

Bipendulum and Quad Pendulum for Non-Compliance Molar Distalization in Adult Patients

BACKGROUND: Pendulum appliances are often used for compliance-independent molar distalization in the upper arch. However, the treatment of adult patients entails specific modifications to the pendulum appliance. Since both first and second molars have to be distalized in adult patients with a sagittal maxillary arch length discrepancy, it is appropriate to distalize the molars consecutively. TWO CASE REPORTS: The two case reports presented below show the clinical procedure using the bipendulum as well as the quad pendulum for unilateral and bilateral distalization of the second followed by the first molars. The treatment is compliance-independent.     

改良摆型矫治器的制作和临床应用

目的 评价各种摆型矫治器的临床应用效果。方法 本文介绍了三种摆型矫治器的改良型,对其适应证、制作方法、临床应用原则、临床操作方法、优缺点等加以论述。结果 ①46带环摆型矫治器适用于所有磨牙需要远中移动的患者。②26带环摆型矫治器适用于前牙段拥挤,尤其尖牙唇向错位的患者;AngleⅡ类2分类前牙舌倾或直立的错He患者。③36带环结合上颌螺旋扩弓改良摆型矫治器适用于前牙段拥护的患者,尤其尖牙唇向错位,并伴有牙弓狭窄者,需要远中移动磨牙,为唇向错位的尖牙提供间隙,同时扩大上颌牙弓,矫正牙弓狭窄。向错位,并伴有牙弓狭窄者,需要远中称移动磨牙,为唇向错位的尖牙提供间隙,同时扩大上颌牙弓,正牙弓狭窄。结论 改良摆型矫治器可以用于不同的患者,有铲地远中移动上颌磨牙,并能同时扩大上颌牙弓、排齐牙列。     

Maxillary molar distalization: Pendulum and Fast-Back, comparison between two approaches for Class II malocclusion

Objectives

To compare the dento-alveolar and skeletal effects produced by two different molar intraoral distalization appliances, Pendulum and Fast-Back, both followed by fixed appliances, in the treatment of Class II malocclusion.

Materials and methods

41 patients for Pendulum (18 males and 23 females) and 35 for Fast-Back (14 males and 21 females) were selected, with a mean age at the start of treatment of 12.11 years in the Pendulum group and 13.3 for in the Fast-Back group. The durations of the distalization phase were 8 months in the Pendulum group and 9 months in the Fast-Back group, and the durations of the second phase of treatment with fixed appliances were 19 months in the Pendulum group and 20 months in the Fast-Back group. Lateral cephalograms were analyzed at 3 observation times: before treatment, after distalization and after comprehensive orthodontic treatment.

Results

During molar distalization the Pendulum subjects showed greater distal molar movement and less anchorage loss at both the premolars and maxillary incisors than the Fast-Back subjects. Pendulum and Fast-Back produced similar amounts of distal molar movement and overcorrection of molar relationship at the end of distalization though the Fast-Back induced a more bodily movement. Very little change occurred in the inclination of the mandibular plane at the end of the 2-phase treatment in both groups. At the end of treatment the maxillary first molars were on average 1 mm more distal in the Pendulum group compared to the Fast-Back group, while the total molar correction was 3.2 mm with 3.9° of distal inclination for the Pendulum and 2 mm with 1.1° of mesial inclination for the Fast-Back. Both appliance were equally effective in inducing a satisfactory Class I relationship in 97.2% of the cases.

Conclusion

The Pendulum and the Fast-Back induce similar dentoskeletal effects. The use of the two distalization devices, therefore, can be considered clinically equivalent.     

A comparison of two intraoral molar distalization appliances: distal jet versus pendulum.

INTRODUCTION: This study compared the dentoalveolar and skeletal effects on Class II malocclusions of the distal jet with concurrent full fixed appliances and the pendulum appliance both followed by fixed appliances. METHODS: The 2 samples each consisted of 32 subjects (19 girls and 13 boys) with mean ages at the start of treatment of 12 years 3 months in the distal jet group and 12 years 6 months in the pendulum group. The durations of the distalization phase of treatment were 10 months in the distal jet group and 7 months in the pendulum group, and the durations of the second phase of treatment with fixed appliances were 18 months in the distal jet group and 24 months in the pendulum group. Lateral cephalograms were analyzed at 3 observation times: before treatment, after distalization, and after orthodontic treatment. RESULTS: During molar distalization, the pendulum subjects showed significantly more distal molar movement and significantly less anchorage loss at both the premolars and the maxillary incisors than the distal jet subjects. The distal jet used simultaneously with fixed appliances and the pendulum were equal in their ability to move the molars bodily. Very little change occurred in the inclination of the mandibular plane at the end of the 2-phase treatment (less than 1 degrees ) in both groups. At the end of comprehensive treatment, the maxillary first molars were 0.6 mm mesial to their original positions in the distal jet group and 0.5 mm distal in the pendulum group. Nevertheless, total molar correction was identical in the 2 groups (3.0 mm), and both appliances were equally effective in achieving a Class I molar relationship. Simultaneous edgewise orthodontic treatment during molar distalization in the distal jet group shortened the overall treatment time but produced significant flaring of both maxillary and mandibular incisors at the end of treatment. The impact on the soft tissue profile was minimal with both appliances.     

上颌第二磨牙萌出对“摆”式矫治器远中移动上颌磨牙疗效的影响

目的研究上颌第二磨牙不同萌出阶段对”摆”式矫治器远中移动上颌磨牙疗效的影响。方法选择上颌牙列轻中度拥挤，磨牙远中关系的病例25例。根据上颌第二磨牙萌出情况分为未萌组（15例）和萌出组（10例）。采用“摆”式矫治器远中移动上颌磨牙。以X线头影测量分析为测定手段。结果①两组的磨牙远中移动距离无显著差异。②未萌组的上颌第一磨牙远中倾斜要大于萌出组，但未萌组的上颌第二磨牙远中倾斜要小于萌出组。③萌出组的上颌第一磨牙相对伸长较多。④上颌中切牙唇向倾斜移动量和前牙覆盖增加量在萌出组较大。结论①萌出的上颌第二磨牙对上颌磨牙远中移动无明显影响。②上颌第二磨牙萌出与否对磨牙远中倾斜有较大影响。③萌出的上颌第二磨牙造成较多支抗丧失。④上颌第二磨牙萌出者在治疗后其上颌第一磨牙伸长较多。     

Dentoalveolar and skeletal changes associated with the pendulum appliance.

The purpose of the study was to examine the dentoalveolar and skeletal effects of the pendulum appliance in Class II patients at varying stages of dental development and with varying facial patterns (high, neutral, and low mandibular plane angles). Specifically, the amount and nature of the "distalization" of the maxillary first molars and the reciprocal effects on the anchoring maxillary first premolars and incisors were studied, as were skeletal changes in the sagittal and vertical dimensions of the face. Pretreatment and posttreatment cephalometric radiographs obtained from 13 practitioners were used to document the treatment of 101 patients (45 boys and 56 girls). The average maxillary first molar distalization was 5.7 mm, with a distal tipping of 10.6 degrees. The anchoring anterior teeth moved mesially, as indicated by the 1.8-mm anterior movement of the upper first premolars, with a mesial tipping of 1.5 degrees. The maxillary first molars intruded 0.7 mm, and the first premolars extruded 1.0 mm. Lower anterior facial height increased 2.2 mm; there was no significant difference in lower anterior facial height increase between patients of high, neutral, or low mandibular plane angles. In patients with erupted maxillary second molars, there was a slightly greater increase in lower anterior face height and in the mandibular plane angle and a slightly greater decrease in overbite in comparison to patients with unerupted second molars. Similar findings were observed in patients with second premolar anchorage versus those with second deciduous molar anchorage. The results of this study suggest that the pendulum appliance is effective in moving maxillary molars posteriorly during orthodontic treatment. For maximum maxillary first molar distalization with minimal increase in lower anterior facial height, this appliance is used most effectively in patients with deciduous maxillary second molars for anchorage and unerupted permanent maxillary second molars, although significant bite opening was not a concern in any patient in this study.     

Efficiency of a pendulum appliance for molar distalization related to second and third molar eruption stage.

A modified pendulum appliance, including a distal screw and special preactivated pendulum springs (built-in straightening activation and toe-in bending), was used for bilateral maxillary molar distalization in 36 adolescent patients in various stages of the molar dentition. The patients were divided into 3 groups (PG 1-3) according to the stage of eruption of their second and third molars. In PG 1 (18 patients), eruption of the second molars had either not yet taken place or was not complete. In PG 2 (15 patients), the second molars had already developed as far as the occlusal plane, with the third molars at the budding stage. In PG 3 (3 patients), germectomy of the wisdom teeth had been carried out, and the first and second molars on both sides had completely erupted. Analysis of cephalograms to identify any changes in the sagittal plane showed that, in the direction of distalization, a tooth bud acts on the mesial neighboring tooth like a fulcrum, and that tipping of the first molars in patients in whom the second molar was still at the budding stage was thus greater. In patients whose second molars had erupted completely, the degree of tipping was greater again when a third molar bud was located in the direction of movement. After previously completed germectomy of the wisdom teeth, almost exclusively bodily distalization of both molars is possible, even without bands being applied to the second molars. However, if the first and second molars are distalized simultaneously with a pendulum appliance, the duration of therapy will be longer, greater forces will have to be applied, and more anchorage will be lost. Statistical analysis of the results of dental-angular measurements showed significant differences in the degree of molar tipping and reciprocal incisor protrusion. The degree of distal tipping of first molars was less in patients with erupted second molars (PG 2 and PG 3) than in those whose second molars were not yet erupted (PG 1). For instance, the measured angles were 0.9 degrees +/- 3.43 degrees (to the palatal plane) and 0.8 degrees +/- 3.4 degrees (to the anterior cranium floor) in PG 2, and -0.33 degrees +/- 0.58 degrees and 0.67 degrees +/- 2.08 degrees, respectively, in PG 3, contrasting with respective values of 5.89 degrees +/- 3.74 degrees and 5.36 degrees +/- 3.49 degrees in PG 1. Tipping of erupted second molars was much more marked in PG 2 (7.92 degrees +/- 5.83 degrees to the palatal plane and 7.55 degrees +/- 5.28 degrees to the anterior cranium floor), but much less pronounced in PG 3 (2 degrees +/- 1.73 degrees to the palatal plane and 2 degrees +/- 2 degrees to the anterior cranium floor) than the corresponding movement of the second budding-stage molars in PG 1 (4.06 degrees +/- 2.15 degrees and 3.97 degrees +/- 2.27 degrees, respectively). The degree of incisor protrusion occurring reciprocally with molar distalization was much less in these patients (measured angles of 3.28 degrees +/- 1.97 degrees and 2.89 degrees +/- 2.17 degrees to the palatal plane and anterior cranium floor, respectively) than in the patients presenting different stages of the dentition (angles of 5.5 degrees +/- 3.33 degrees and 6.03 degrees +/- 4.29 degrees, respectively, in PG 2, and angles of 5.5 degrees +/- 3.28 degrees and 6.67 degrees +/- 3.09 degrees, respectively, in PG 3). Moreover, measurement of dental casts in the horizontal plane showed not only the targeted mesiobuccal rotation of both maxillary molars, but also a vestibular drift of the unbanded second molars.     

GMD矫治器与钟摆矫治器远移上颌磨牙效果对比研究

目的：通过对GMD矫治器与钟摆矫治器的对比研究探讨该矫治器应用的可行性、优越性及其适应症.方法：对58例因上颌磨牙前移所导致的安氏Ⅱ类错[牙合]患者,分别使用GMD矫治器与钟摆矫治器进行推上颌磨牙向远中移动的非拔牙矫治,通过矫治前及磨牙远移到位后的X线头影测量及模型测量分析进行对比研究.结果：两种方法最终都实现了推磨牙远移的目的,但是GMD矫治器的磨牙移动更接近于整体移动,支抗控制也强于钟摆矫治器.结论：GMD矫治器能够有效、快速地远移磨牙,是一种新的有效远移磨牙的矫治器.     

改良式摆型矫治器远中移动上颌磨牙的疗效分析

目的 评价改良式摆型矫治器远中移动上颌磨牙的疗效。方法 选择14例牙性安氏Ⅱ类错的患者,应用改良式摆型矫治器远移上颌第一磨牙,通过矫治前和磨牙远移到位后的X线头影测量分析评价其疗效。结果 磨牙平均向远中移动3.85mm,牙冠远中倾斜3.22°;切牙近中倾斜移动2.08mm,覆盖增加1.68mm。结论 改良式摆型矫治器能有效地整体远中移动上颌磨牙,快速矫正磨牙关系,但也会引起少量的支抗丧失和切牙唇向移动。     

Maxillary molar distalization with a bone-anchored pendulum appliance

To obtain an effective and compliance-free molar distalization without an anchorage loss, we designed the bone-anchored pendulum appliance (BAPA). The aim of this study was to evaluate the stability of the anchoring screw, distalization of the maxillary molars, and the movement of teeth anterior to maxillary first molars. The study group comprised 10 patients (mean age 13.5 +/- 1.8 years) with Class II molar relationship. A conventional pendulum appliance was modified to obtain anchorage from an intraosseous screw instead of the premolars. The screw was placed in the anterior paramedian region of the median palatal suture. Skeletal and dental changes were measured on cephalograms, and dental casts were obtained before and after distalization. A super Class I molar relationship was achieved in a mean period of 7.0 +/- 1.8 months. The maxillary first molars distalized an average of 6.4 +/- 1.3 mm in the region of the dental crown by tipping distally an average of 10.9 degrees +/- 2.8 degrees . Also, the maxillary second premolar and first premolar moved distally an average of 5.4 +/- 1.3 mm and 3.8 +/- 1.1 mm, respectively. The premolars tipped significantly distally. No anterior incisor movement was detected. The BAPA was found to be an effective, minimally invasive, and compliance-free intraoral distalization appliance for achieving both molar and premolar distalization without any anchorage loss.     

A new approach in maxillary molar distalization: intraoral bodily molar distalizer.

The objectives of our study were to achieve bodily molar distalization, avoid distal tipping of molars, eliminate the need for patient cooperation (no headgear, no elastics, and no esthetic and social concern), and finally to minimize the treatment period and maximize the treatment efficiency. The study was carried out on 5 males and 10 females, a total of 15 patients. Mean age for the study group was 13.53 years. Dentally, all the patients had Class II molar relationship on both sides. The patients were in permanent dentition, second molars were erupted, and the lower dental arch was well aligned. Patients showed normal or sagittally directed growth pattern. Lateral cephalograms and study models were taken and analyzed before and after molar distalization. In the present study, in order to achieve maxillary molar distalization, a new intraoral appliance was developed. The intraoral bodily molar distalizer (IBMB) was composed of 2 parts: the anchorage unit and the distalizing unit. The anchorage unit was a wide Nance button, and the active unit consisted of distalizing springs. The springs had 2 components: the distalizer section of the spring applied a crown tipping force, while the uprighting section of the spring applied a root uprighting force on the first molars. A total of 230 g of distalizing force was used on both sides. After the distal movement of the first molars, the cephalometric results of 15 patients showed the following. Maxillary first molars were moved distally by an average of 5.23 mm (P <.001) without tipping or extrusion. Maxillary first premolars were moved 4.33 mm mesially (P <.001), tipped 2.73 degrees distally (P <.05), and extruded by 3.33 mm (P <.001). Maxillary central incisors were proclined by an average of 4.7 mm (P <.001) and tipped 6.73 degrees labially (P <.01). Model analysis showed that maxillary first molars were not rotated, and intermolar distance did not change after distal movement of molars. In conclusion, unlike most of the other molar distalization mechanics, this newly developed device achieved (1) bodily distal movement of maxillary molars and (2) eliminated dependence on patient cooperation and did not require headgear wear for molar root uprighting.     

Comparative evaluation of molar distalization therapy with erupted second molar: Segmented versus Quad Pendulum appliance

Background

There are controversial opinions about the effect of erupted second molars on distalization of the first molars. Most of the distalizing devices are anchored on the first molars, without including second molars; so, differences between sequentially distalize maxillary molars (second molar followed by the first molar) or distalize second and first molars together are not clear. The aim of the study was to compare sequential versus simultaneous molar distalization therapy with erupted second molar using two different modified Pendulum appliances followed by fixed appliances.

Methods

The treatment sample consisted of 35 class II malocclusion subjects, divided in two groups: group 1 consisted of 24 patients (13 males and 11 females) with a mean pre-treatment age of 12.9 years, treated with the Segmented Pendulum (SP) and fixed appliances; group 2 consisted of 11 patients (6 males and 5 females) with a mean pre-treatment age of 13.2 years, treated with the Quad Pendulum (QP) and fixed appliances. Lateral cephalograms were obtained before treatment (T1), at the end of distalization (T2), and at the end of orthodontic fixed appliance therapy (T3). A Student t test was used to identify significant between-group differences between T1 to T2, T2 to T3, and T1 to T3.

Results

QP and SP were equally effective in distalizing maxillary molars (3.5 and 4 mm, respectively) between T1 and T2; however, the maxillary first molar showed less distal tipping (4.6° vs. 9.6°) and more extrusion (1.1 vs. 0.2 mm) in the QP group than in the SP group, as well as the vertical facial dimension, which increased more in the QP group (1.2°) than in the SP group (0.7°). At T3, the QP group maintained greater increase in lower anterior facial height and molar extrusion and decrease in overbite than the SP group.

Conclusion

Quad Pendulum seems to have greater increase in vertical dimension and molar extrusion than the Segmented Pendulum.     

钟摆矫治器远中移动磨牙的疗效分析

目的:评价钟摆矫治器远中移动磨牙的疗效。方法:测量10例应用该矫治器推磨牙向远中患者的术前术后模型,观察磨牙远中移动的距离及磨牙间宽度、覆覆盖的变化。结果:钟摆矫治器使磨牙每月平均远中移动117 mm,磨牙间宽度平均减小019 mm,覆平均减小115 mm,覆盖基本无变化。结论:钟摆矫治器是一种快速有效的推磨牙向远中的矫治器,对第二磨牙已萌的成人患者也有效。但它有打开咬合的作用,不适用于高角病例。     

摆形矫治器矫治不同垂直骨面型安氏Ⅱ类错的疗效评价

目的　探讨摆形矫治器矫治不同垂直骨面型安氏Ⅱ类错的疗效及对牙颌面的影响。方法　对30例样 本(低角组、均角组、高角组各10例)治疗前后的24项X线头影测量指标进行测量和比较分析。结果　上颌磨牙在 不同的垂直骨面型中远中移动的距离不同,低角组移动最小,高角组移动最大;上颌磨牙在3组中均被压低,但差 别无统计学意义;各组样本第一双尖牙向近中移动量和前牙覆盖增加量不同,低角组最多,高角组最少。结论　摆 形矫治器可有效远中移动磨牙,在不同的垂直骨面型磨牙均被压低,为摆形矫治器用于矫治AngleⅡ类高角患者提 供了理论依据。