Comparison of skeletal maxillary transverse deficiency treated by microimplant-assisted rapid palatal expansion and tooth-borne expansion during the post-pubertal growth spurt stage:: A prospective cone beam computed tomography study

ObjectiveTo investigate the efficacy of microimplant-assisted rapid palatal expansion (MARPE) to treat skeletal maxillary discrepancies during the post-pubertal growth spurt stage.Materials and MethodsSixty patients with skeletal maxillary transverse deficiency during the post-pubertal growth spurt stage were randomly divided into MARPE and Hyrax groups. Thirty patients (mean age: 15.1 ± 1.6 years) were treated using the four-point MARPE appliance; 30 patients (mean age, 14.8 ± 1.5 years) were treated using the Hyrax expander. Cone beam computed tomography scans and dental casts were obtained before and after expansion. The data were analyzed using paired t-tests and independent t-tests.ResultsThe success rates of midpalatal suture separation were 100% and 86.7% for MARPE and Hyrax groups, respectively. Palatal expansion and skeletal to dental ratio at the first molar level were greater in the MARPE group (3.82 mm and 61.4%, respectively) than in the Hyrax group (2.20 mm and 32.3%, respectively) (P < .01). Reductions in buccal alveolar bone height and buccal tipping of the first molars were less in the MARPE group than in the Hyrax group (P < .01).ConclusionsMARPE enabled more predictable and greater skeletal expansion, as well as less buccal tipping and alveolar height loss on anchorage teeth. Thus, MARPE is a better alternative for patients with skeletal maxillary deficiency during the post-pubertal growth spurt stage.     

Hyrax快速与慢速扩弓矫治替牙晚期上颌狭窄疗效对比研究

目的 比较Hyrax快速与慢速扩弓矫治替牙晚期上颌狭窄的疗效。 方法 选取2011年1月至2012年12月来大连市口腔医院正畸科就诊的替牙晚期上颌基骨狭窄患者60例,随机分成2组,分别采用Hyrax快速扩弓与Hyrax慢速扩弓进行矫治,扩弓前后拍摄锥形束CT（cone beam computerized tomography ,CBCT）,通过Invivo5牙科软件三维重建,分别测量扩弓前后上颌第一磨牙、第一前磨牙冠状位硬腭水平基骨宽度、颊侧牙弓宽度、双侧牙槽骨倾斜角度的交角、双侧牙齿倾斜角度的交角,轴位颊、舌侧骨质厚度。扩弓前后数据采用SPSS 17.0统计软件进行分析。结果 冠状位：Hyrax快速扩弓与Hyrax慢速扩弓在骨性开展和牙弓总宽度变化上无差别,扩弓后牙弓总宽度增加,第一前磨牙平面的骨开展量大于第一磨牙平面,牙齿和牙槽嵴颊向倾斜,牙槽嵴倾斜的角度慢速扩弓组大于快速扩弓组,牙齿倾斜的角度快速扩弓组大于慢速扩弓组;轴位：颊侧骨质厚度减少,舌侧骨质厚度增加,但Hyrax慢速扩弓组颊侧的减少量小于Hyrax快速扩弓组,两组差异有统计学意义（P＜0.05）。结论 对于替牙晚期患者,与Hyrax快速扩弓相比,Hyrax慢速扩弓慢速轻力的特点更符合生理特性,并且对颊侧的骨质厚度影响小,是一种有效的扩弓方式。     

快速腭扩展对牙颌横向矫治作用的研究

目的：探讨快速腭扩展对牙颌各结构的横向矫正作用。方法：对12例恒牙期上颌狭窄病例用Hyrax扩弓器行快速腭扩展矫治。通过矫治前后研究模型分析,头颅后前位定位X线片头影测量分析评价腭扩展效果。结果：快速腭扩展使上腭中缝打开,上颌牙齿及牙槽基骨颊向移动,支抗磨牙位移最大,平均4.84mm。牙槽突点（alm）侧移大于上颌点（mx）。全鼻高侧移过程中以鼻高中1/2水平（bn50）侧移量最大,平均2.74mm。上颌中线两侧牙齿,牙槽骨及颌骨位移值的变化无统计学差异。结论：上颌快速腭扩展在打开腭中缝解除上牙弓狭窄时,上颌牙齿、牙槽基骨发生了颊向移动,基骨位移量大于牙齿位移量,上颌牙槽突发生了形变。鼻上颌复合体整体位移效果呈三角形,中线两侧基本对称。     

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目的 比较Hyrax快速与慢速扩弓矫治替牙晚期上颌狭窄的疗效。方法 选取2011年1月至2012年12月来大连市口腔医院正畸科就诊的替牙晚期上颌基骨狭窄患者60例,随机分成2组,分别采用Hyrax快速扩弓与Hyrax慢速扩弓进行矫治,扩弓前后拍摄锥形束CT(cone beam computerized tomography,CBCT),通过Invivo5牙科软件三维重建,分别测量扩弓前后上颌第一磨牙、第一前磨牙冠状位硬腭水平基骨宽度、颊侧牙弓宽度、双侧牙槽骨倾斜角度的交角、双侧牙齿倾斜角度的交角,轴位颊、舌侧骨质厚度。扩弓前后数据采用SPSS 17.0统计软件进行分析。结果 冠状位:Hyrax快速扩弓与Hyrax慢速扩弓在骨性开展和牙弓总宽度变化上无差别,扩弓后牙弓总宽度增加,第一前磨牙平面的骨开展量大于第一磨牙平面,牙齿和牙槽嵴颊向倾斜,牙槽嵴倾斜的角度慢速扩弓组大于快速扩弓组,牙齿倾斜的角度快速扩弓组大于慢速扩弓组;轴位:颊侧骨质厚度减少,舌侧骨质厚度增加,但Hyrax慢速扩弓组颊侧的减少量小于Hyrax快速扩弓组,两组差异有统计学意义(P<0.05)。结论 对于替牙晚期患者,与Hyrax快速扩弓相比,Hyrax慢速扩弓慢速轻力的特点更符合生理特性,并且对颊侧的骨质厚度影响小,是一种有效的扩弓方式。     

传统与改良Hyrax扩弓器对牙弓、牙槽骨、基骨影响的CBCT对比研究

目的应用CBCT比较传统Hyrax扩弓器与改良Hyrax扩弓器对牙弓、牙槽骨及基骨的影响。方法将30例上颌牙弓狭窄的患者随机分为2组,传统Hyrax扩弓器组15例患者,8男7女,平均年龄(14.1±2.5)岁,改良Hyrax扩弓器组15例患者,9男6女,平均年龄(13.9±2.6)岁。收集2组患者扩弓前及扩弓3个月后的CBCT扫描数据,重建三维影像并测量牙弓、牙槽骨及基骨的相应指标,应用配对样本的t检验分析2组扩弓后测量指标的变化,应用独立样本的t检验分析2组测量指标之间的差异。结果 2组都存在基骨的改变及牙弓宽度的增加,2组之间的比较显示传统Hyrax组的第一、二前磨牙牙弓宽度大于改良Hyrax组,第一磨牙颊侧及腭侧牙槽骨厚度的变化2组并无统计学的差异,而第一前磨牙颊侧及腭侧牙槽骨的厚度变化2组有统计学差异,此外,2组之间绝对牙倾斜度比较也并无统计学差异。结论两种快速扩弓方法对于纠正上颌牙弓狭窄都有较为明显的效果,传统Hyrax扩弓器对第一前磨牙牙弓宽度及颊腭侧牙槽骨厚度的影响更大。     

Rapid maxillary expansion--tooth tissue-borne versus tooth-borne expanders: a computed tomography evaluation of dentoskeletal effects

This study evaluated rapid maxillary expansion (RME) dentoskeletal effects by means of computed tomography (CT), comparing tooth tissue-borne and tooth-borne expanders. The sample comprised eight girls aged 11 to 14 years presenting Class I or II malocclusions with posterior unilateral or bilateral crossbite that were randomly divided into two treatment groups, palatal acrylic (Haas-type) and hygienic (Hyrax) expanders. All appliances were activated up to the full seven mm capacity of the expansion screw. The patients were subjected to a spiral CT scan before expansion and after a three-month retention period when the expander was removed. One-millimeter-thick axial sections were scanned parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure maxillary transverse dimensions and posterior teeth inclination by means of a computerized method. The results showed that RME produced a significant increase in all measured transverse linear dimensions, decreasing in magnitude from dental arch to basal bone. The transverse increase at the level of the nasal floor corresponded to one-third of the amount of screw activation. Tooth-borne (Hyrax) and tooth tissue-borne (Haas-type) expanders tended to produce similar orthopedic effects. In both methods, RME led to buccal movement of the maxillary posterior teeth, by tipping and bodily translation. The second premolars displayed more buccal tipping than the appliance-supporting teeth. The tooth tissue-borne expander produced a greater change in the axial inclination of appliance-supporting teeth, especially first premolars, compared with the tooth-borne expander.     

改良式Hyrax扩弓器矫治上颌牙弓狭窄的临床观察

目的观察改良式Hyrax扩弓器对生长发育期上颌牙弓狭窄的矫治作用。方法选择14例恒牙早期上颌牙弓狭窄病例,应用改良式Hyrax扩弓器进行扩弓。通过测量扩弓前后X线头颅定位侧位片和模型,进行统计学分析。结果14例上颌牙弓狭窄患者经2~3周扩弓后,后牙反全部解除并过矫治2~3mm,■间出现间隙2~4mm。上颌正中咬合片显示:腭中缝打开,低密度阴影出现。结论改良式Hyrax扩弓器是一种快速、有效、安全、经济实惠的扩弓装置。     

Dental arch size and shape after maxillary expansion in bilateral complete cleft palate: A comparison of three expander designs

Objective:The objective of this study was to compare the effects on upper dental arch size and shape after maxillary expansion with Hyrax, Quad-helix, and a differential opening expander in bilateral cleft lip and palate (BCLP) patients.Materials and Methods:Seventy-five BCLP patients were divided into three groups: Hyrax (H), Quad-helix (QH), and Expander with differential opening (EDO). Digital models were obtained before (T1) and after 6 months (T2) of maxillary expansion. Twelve landmarks were placed by one investigator on T1 and T2 dental models of each group, and x,y coordinates for each landmark were collected. For dental arch size analysis, centroid size of each dental arch at T1 and T2 was calculated from raw coordinates and was used as the measure of size. Procrustes Analysis was performed for dental arch shape analysis. Analysis of variance was used to compare the groups for size and shape differences (P < .05).Results:There were no significant dental arch size differences among the expanders at T1 or T2. Differences in arch shape were found between all groups at T2. Intragroup arch shape showed a significant variation for the QH and EDO groups. while it remained stable in the H group.Conclusions:Both the QH and the EDO create dental arch shape changes with greater intercanine than intermolar increase. The H does not change the dental arch shape.     

Short-term skeletal and dentoalveolar effects of overexpansion:: A pilot randomized controlled trial

ObjectivesTo evaluate whether the amount of rapid maxillary expansion differentially affects the skeletal and dentoalveolar changes that occur.Materials and MethodsThis randomized controlled trial included 23 patients who had rapid maxillary expansion (RME). Subjects were randomly assigned to a conventional expansion control group (n = 12) or an overexpansion group (n = 11), who started treatment at 13.2 ± 1.5 and 13.8 ± 1 years of age, respectively. Cone beam computed tomography scans (11 cm) were obtained prior to rapid maxillary expander (RME) delivery and approximately 3.7 months later. Initial hand-wrist radiographs were used to determine the participants'' skeletal maturity.ResultsThe RME screws were activated 5.6 ± 1.2 mm and 10.1 ± 0.6 mm in the conventional and overexpansion groups, respectively. Overexpansion produced significantly greater expansion of the nasal cavity (2.1X–2.5X), maxillary base (2.3X), buccal alveolar crest (1.4X), and greater palatine foramina (1.9X). Significantly greater intermolar width increases (1.8X) and molar inclination (2.8X) changes were also produced. The nasal cavity and maxillary base expanded 23%–32% as much as the screws were activated. Skeletal expansion was positively correlated with RME screw activation (R = 0.61 to 0.70) and negatively correlated (R = −0.56 to −0.64) with the patients'' skeletal maturation indicators (SMIs). Together, screw activation and the patients'' SMI scores explained 48%–66% of the variation in skeletal expansion.ConclusionsThis pilot study shows that overexpansion produces greater changes than conventional expansion, with greater skeletal effects among less mature patients.     

Upper airway assessment using four different maxillary expanders in cleft patients: A cone-beam computed tomography study

Objective:To evaluate the anterior and posterior maxillary width, the nasal passage volume, the oropharyngeal minimum axial area, and volume changes in unilateral cleft lip and palate patients treated with one of the following four expanders: Hyrax, Fan-Type, inverted mini-hyrax supported on the first permanent molars (iMini-M), or inverted mini-hyrax supported on the first premolars (iMini-B).Materials and Methods:A total of 40 patients with transverse maxillary deficiency who were submitted for rapid maxillary expansion were divided in four groups according to type of expander used. Cone-beam computed tomography images were taken before and 3 months after expansion. One-way analysis of variance was used to analyze the differences among the groups, and paired t-tests were used to evaluate the changes in each group.Results:All groups showed a significant increase in the anterior maxillary width, with no intergroup differences. The iMini-B was the only group that did not show a significant increase in the posterior maxillary width. The intergroup comparison demonstrated differences among all groups except between Hyrax and iMini-M, which showed the greatest posterior expansions. The intragroup analysis showed a significant increase in the nasal passage volume in hyrax and inverted mini-hyrax on the molar groups, but the intergroup comparison revealed a significant difference only between Fan-Type and inverted mini-hyrax on the molars. None of the expanders caused significant changes in the oropharyngeal measurements.Conclusions:Only the Hyrax and inverted mini-hyrax on the molar expanders effectively increased the nasal passage volume, and none of the expanders evaluated in this study modified the oropharyngeal airway.     

Evaluation of miniscrew-supported rapid maxillary expansion in adolescents: A prospective randomized clinical trial

Objectives:To evaluate and compare the dental and skeletal changes with conventional and miniscrew-supported maxillary expansion appliances in adolescents.Materials and Methods:Forty patients were divided into two groups, with one group receiving a tooth-borne expander and the other group receiving an expander supported by four miniscrews (bone-borne). Multiplanar coronal and axial slices obtained from cone-beam computed tomography images were used to measure the changes in transverse skeletal widths, buccal bone thickness, tooth inclination, and root length. Paired t-tests and independent-sample t-tests were used to compare the two expansion methods.Results:Bone-borne expansion increased the maxillary suture opening more than 2.5 times than tooth-borne expansion both anteriorly and posteriorly. Between the maxillary first premolars, sutural expansion accounted for 28% and 70% of the total transverse width increase in the tooth-borne and bone-borne expander groups, respectively. Similarly, 26% and 68% of the total expansion was of skeletal nature in the tooth-borne and bone-borne expander groups between the maxillary first molars. The pattern of expansion was variable, with most of the patients in both groups demonstrating a triangular-shaped sutural opening that was wider anteriorly. Subjects in the conventional group experienced significantly more buccal bone reduction and greater buccal inclination of the teeth. No significant differences were observed for root length measurements between the two groups.Conclusion:Use of bone-borne expansion in the adolescent population increased the extent of skeletal changes in the range of 1.5 to 2.8 times that of tooth-borne expansion and did not result in any dental side effects.     

Three-dimensional evaluation of upper airway following rapid maxillary expansion: A CBCT study

Objectives:To evaluate, by using cone beam computed tomography, the skeletal, dental, oropharyngeal (OP) airway volume, and nasal passage (NP) volume changes that occur after rapid maxillary expansion (RME).Materials and Methods:Two groups were selected, each with 35 patients (15 males, 20 females), an RME group (mean age, 14.02 ± 1.46 years) and a control group (mean age, 14.10 ± 1.44 years). The RME group consisted of patients with maxillary constriction who were treated with Hyrax palatal expanders, and the control group comprised age- and sex-matched patients who underwent comprehensive orthodontic treatment without the use of a rapid maxillary expander.Results:All of the transverse skeletal (medial orbital width, lateral nasal width, maxillary width, and mandibular width) and interdental (intermolar, interpremolar, and intercanine) parameters were significantly enlarged in the RME group. A statistically significant increase in airway variables was seen in both groups between pretreatment (T0) and final records (T1). The mean increase of NP airway volume for the RME group (1719.9 ± 1510.7 mm³) was twofold compared with the control group (813.6 ± 1006.7 mm³), and no intergroup significant difference was found for the OP volume.Conclusions:Rapid maxillary expansion creates a significant increase in nasal passage airway volume but no significant change in the oropharyngeal airway volume.     

自锁托槽对唇腭裂腭扩展短期效果的研究

目的：探讨自锁托槽对单侧完全性唇腭裂患者上颌腭扩展的短期治疗效果。方法选取5例恒牙期单侧完全性唇腭裂（UCLP）患者,未行牙槽突裂骨移植手术,上颌牙齿粘贴自锁托槽（AO, Time2）,放置高弹性镍钛弓丝,采集患者治疗前和腭扩展6~17个月后的牙颌模型、头颅定位后前位片进行测量,分析上颌腭扩展前后患者的牙弓、牙槽骨、腭穹窿以及颌骨的形态变化。结果牙颌模型测量结果提示：第一前磨牙区牙弓宽度明显增大,其次为尖牙区牙弓宽度,第一磨牙区牙弓宽度增加最少,第二磨牙区宽度减小。牙弓长度变化不明显。第一磨牙近中颊向扭转。腭部宽度增加,深度减小。头影测量结果提示：鼻腔宽度、上颌基骨宽度和上颌磨牙宽度稍有增加。结论唇腭裂自锁托槽腭扩展后上颌牙颌形态在横向宽度的变化较矢状向的变化明显。短期腭扩展治疗效果以牙齿移动和牙槽改建为主。     

Transverse effects of surgically assisted rapid maxillary expansion: a comparative study using Haas and Hyrax

BACKGROUND: Surgically assisted rapid maxillary expansion is the treatment of choice for correcting transverse maxillary deficiency in patients with skeletal maturity, although the influence of the expander type on these alterations has not been elucidated yet. OBJECTIVE: Determine the skeletal and dental transverse effects on the maxilla after completion of surgically assisted rapid maxillary expansion, with Haas and Hyrax expanders. METHODS: Thirty-eight patients (aged between 18 and 39 years) were submitted to subtotal Le Fort I osteotomy and divided into Hass and Hyrax groups (19 patients each). Measurements of maxillary width, upper intermolar width, and its inclination on the posteroanterior cephalometric radiographs were obtained in the preoperatory period (T1), after the completion of the expansion (T2), and 4 months after the completion of the expansion (T3). The intercusp and intergingival distances measured on the plaster models were obtained from the first premolars and molars, before expander cementation (M1) and after the expander removal (M2). RESULTS: Both groups revealed statistically significant increase in the maxillary width, upper intermolar width, and inclination of the molars in T2 (P<0.001); T3 showed a statistically significant decrease in the maxillary width and inclination of the molars (P<0.001). The expansion presented an increment on the maxillary width of 71% from the upper intermolar width (T1-T3), and molars had vestibular inclination (P<0.05). The ratio of width increase of maxilla by the amount of device activation was of 69% for Haas and 74.5% for Hyrax. CONCLUSION: Clinically, the transversal effects were similar for both groups.     

Molar Inclination and Surrounding Alveolar Bone Change Relative To the Design of Bone-borne Maxillary Expanders: A Cbct study

ObjectiveTo evaluate the molar inclination and skeletal and alveolar bone changes when comparing tooth bone-borne (MSE) and tissue bone-borne type maxillary expanders (C-expander) using cone-beam computed tomography (CBCT) in late adolescence.Materials and MethodsA sample of 48 late-adolescent patients were divided into two groups according to the type of expander: MSE group (n = 24, age = 19.2 ± 5.9 years) and C-expander group (n = 24, age = 18.1 ± 4.5 years). CBCT scans were taken before treatment and 3 months after expansion. Transverse skeletal and dental expansion, alveolar inclination, tooth axis, buccal alveolar bone height, thickness, dehiscence, and fenestration were evaluated on the maxillary first molar. Paired t-test, independent t-test, Pearson''s chi-square test, and Spearman correlation analysis were performed.ResultsThe MSE group produced greater dental expansion (P < .05), whereas skeletal expansion was similar in both groups (P = .859). The C expander group had more alveolar bone inclination change (P < .01), and the MSE group had more buccal tipping of the anchorage teeth (P < .01 or .001). Buccal alveolar bone height loss and thickness changes were greater in the MSE group (P < .01 or <.001). Formation of dehiscences was more frequent in the MSE group (P < .001), whereas for fenestrations, there were no significant differences between the two groups. Buccal bone height loss in the MSE group had a negative correlation with initial buccal bone thickness.ConclusionsThe incorporation of teeth into bone-borne expanders resulted in an increase in the severity of side effects. For patients in late adolescence, tissue bone-borne expanders offer comparable skeletal effects to tooth bone-borne expanders, with fewer dentoalveolar side effects.     

Arch perimeter changes on rapid palatal expansion

Relationships between changes in arch perimeter and arch width resulting from rapid palatal expansion with the Hyrax appliance were analyzed with the use of dental study casts of 21 adolescent patients. Photographs and measurements from the dental casts obtained before treatment and approximately 3 months after stabilization were used. Regression analysis indicated that changes in premolar width were highly predictive of changes in arch perimeter (r2 = 0.69) at approximately 0.7 times the premolar expansion. Without any orthodontic appliances attached to the mandibular teeth in 16 of the 21 patients, buccal uprighting of the posterior teeth was observed because of the redirection of occlusal forces. In addition, posterior movement of the maxillary incisors and buccal tipping of the anchor teeth were quantified. The prediction of arch perimeter change for a given amount of expansion is helpful in the treatment planning of rapid palatal expansion cases and may facilitate nonextraction orthodontic treatment.     

A comparison of dentoalveolar inclination treated by two palatal expanders

The objective of the present study was to evaluate buccal dentoalveolar inclinations in subjects treated with a Hyrax (tooth-borne) or acrylic-bonded (tooth-tissue borne) palatal expander. The sample comprised 39 patients (10 males and 29 females) aged between 11 and 16 years randomly assigned to two groups. Rapid maxillary expansion (RME) was carried out with a Hyrax appliance in one group (n = 21) and with an acrylic-bonded appliance in the other (n = 18). Their mean ages were 13 years 9 months and 13 years 6 months, respectively. Orthodontic study models were obtained before RME (T1) and approximately 1 week after completion of maxillary expansion (T2). A line of barium sulphate solution was drawn between the upper first molars on the models, and radiographs were taken. The radiographic images of the models were transferred to digital medium, and buccal tipping of the molar crowns and alveolar processes were evaluated by means of a software program. The data were analysed by paired and Student's t-tests. Both RME appliances produced significant (P < 0.001) dentoalveolar tipping during RME, but this was greater in the Hyrax group (P < 0.05).     

Perceived pain during rapid maxillary expansion in children with different expanders:: A prospective study

ObjectivesTo evaluate and compare the intensity of pain caused by rapid maxillary expansion (RME) with two expanders: Hyrax and Haas type, in growing patients.Materials and MethodsThirty-nine patients (23 girls and 16 boys) with an average age of 9.3 years (SD = 1.39 years) were randomized into two groups and treated with Hyrax- and Haas-type expanders. In both groups, initial activation of the expander screw was one full turn on the first day followed by 2/4 of a turn two times a day (morning and night) for 7 days. Inclusion criteria were patients presenting with a posterior crossbite or maxillary atresia between 7 and 12 years old. To evaluate the intensity of pain during the active phase of the treatment, a combination of the Numerical Rating Scale and Wong-Baker Faces Pain Scale was used. Mann-Whitney test was used to compare the two treatment groups.ResultsThere was significant inverse correlation between days following insertion and pain. During the expansion period, 100% of the children reported some pain. Hyrax expander subjects reported greater pain than those treated with the Haas-type expander only on the first day. The level of pain remained greater in girls throughout treatment.ConclusionsPain was reported regardless of the type of expander and was higher in the Hyrax group only on the first day of activation.     

Evaluation of maxillary buccal alveolar bone before and after orthodontic alignment without extractions: A cone beam computed tomographic study

Objectives:To assess the changes in the maxillary buccal alveolar bone during alignment without extractions. Secondarily, to evaluate the changes in arch dimensions and buccolingual inclinations of teeth and to identify risk factors for bone loss.Materials and Methods:Twenty-two adolescents with crowded permanent dentitions were treated without extractions with Damon 3MX brackets. Cone beam computed tomographic scans were taken before treatment (T0) and after alignment (T1). Bone thickness (BT) and height from the cementoenamel junction to the alveolar crest (BH) were evaluated at the maxillary central incisors, second premolars, and buccal roots of first molars. Changes in all variables from T0 to T1 were assessed. Correlations between bone changes and initial bone thickness, initial arch widths, initial crowding, amount of expansion, amount of tipping, and amount of molar rotation were calculated.Results:BT decreased and BH increased significantly for the incisors and mesiobuccal root of the first molars. Arch dimensions generally increased together with tipping. Bone loss was correlated with crowding and amount of expansion in the premolar region. Initially thinner BT was correlated with greater apical migration of bone for the incisors.Conclusions:Nonextraction alignment with self-ligating brackets led to arch expansion associated with tipping of teeth. Expansion related to alignment resulted in horizontal and vertical bone loss at the incisors and mesiobuccal root of the first molars. Thinner BTs and more severe crowding before treatment increased the risk for buccal bone loss.     

Longitudinal clinical study on the effect of slow maxillary expansion with removable appliances

The aim of this clinical study was to evaluate the longitudinal changes in dental arches in patients treated with a slow maxillary expansion appliance in primary dentition or early mixed dentitionMethodsThe sample consisted of 19 children (13 girls and 6 boys) with a narrowing of the maxillary arch. The mean ages at the start, at the end of expansion, and at the final follow-up (1 year 7 months after the retention) were 7 years 10 months, 8 years 10 months and 12 years 4 months, respectively. The mean expansion period was 1 year and the mean retention period after the expansion was 1 year 11 months. The control group consisted of 28 Japanese persons with untreated normal occlusion.ResultsThe results were as follows. (1) At the end of the expansion, the maxillary dental arch width increased remarkably, and there was no significant difference in comparison with the control group. (2) At the follow-up after the retention, although the maxillary intercanine width was significantly smaller than the control group, the maxillary intermolar width stabilized during retention and there was no significant difference in comparison with the control group. (3) The mandibular intermolar width gradually increased during the maxillary expansion.ConclusionThis clinical study demonstrated that this type of treatment using a slow maxillary expansion appliance in primary dentition or early mixed dentition is effective and stable in the long term for the maxillary molar regions. Furthermore, it was suggested that the lateral development of the mandibular dental arch could be promoted by expanding the maxillary dental arch width.