正畸扩弓治疗中疼痛与昼夜节律相关性的研究

目的：研究按照昼夜节律进行正畸加力控制,获得昼夜节律对正畸扩弓治疗中疼痛的影响和作用,为临床上更有效地进行正畸加力治疗后的疼痛控制。方法：34例连续正畸扩弓治疗病例,男18例,女16例,年龄10.8～12.8岁,腕骨片示均处于生长发育高峰期,采用相同固定快速扩弓装置,每日加力时间按照人体昼夜节律规律分为0点、3点、6点、9点、12点、15点、18点、21点8个时段组,每组加力方式相同,利用MPQ疼痛量表进行疼痛程度的观察,通过统计学软件进行余弦拟合及多样本t检验。结果：不同性别对于疼痛的耐受力有区别,女性对于正畸扩弓治疗疼痛的耐受力低于相同情况下男性。正畸加力后疼痛量化结果显示正畸加力后疼痛基本符合昼夜节律规律。峰值出现在0点,而谷值出现在12点的时间节点。结论：人体昼夜节律可以影响正畸扩弓治疗后的疼痛程度。按照昼夜节律进行正畸扩弓矫治可以获得更好的疼痛控制效果。提示正畸扩弓加力较合适在午间进行,这样有利于控制正畸患者的疼痛。     

上颌反复快速扩缩前方牵引效果的锥形束CT观察

目的 使用锥形束CT比较上颌单次快速扩弓前方牵引和上颌反复快速扩缩前方牵引的矫治效果,以期为临床提供参考.方法 选择24例上颌后缩患者,使用随机化区组设计的方法分为对照组和反复扩缩组,每组12例.对照组上颌单次快速扩弓后行面罩前方牵引;反复扩缩组上颌反复快速扩缩后行面罩前方牵引.对每组治疗前后的锥形束CT影像进行三维重建、定点、重叠和测量分析.结果 反复扩缩组1例患者在治疗中失访.治疗后反复扩缩组上颌骨前移量[(2.5±1.0)mm]显著大于对照组[(1.6±0.8)mm](P＜0.05);反复扩缩组颅底点至上齿槽座点(Ba-A)的距离增加了(3.1±1.0) mm,显著大于对照组[(2.2±0.9)mm](P＜0.05);反复扩缩组上颌双侧第一磨牙前移量显著大于对照组(P＜0.05).结论 与上颌单次快速扩弓相比,上颌反复快速扩缩前方牵引早期治疗上颌后缩患者可能对上颌骨前移略有利.     

安氏Ⅰ类边缘型牙列拥挤非拔牙快速扩弓矫治的临床疗效研究

目的研究安氏Ⅰ类边缘型牙列拥挤病例非拔牙快速扩弓矫治的牙弓参数变化,探讨其临床疗效.方法对9例安氏Ⅰ类边缘型牙列拥挤病例采用上颌快速扩弓配合上下固定矫治技术进行非拔牙正畸治疗,分别在T1(正畸治疗前)、T2(快速扩弓三个月后)和T3(正畸治疗结束进入固定保持期)三个时间点结合模型分析对牙弓参数进行分析.结果上颌第一磨牙、第一双尖牙和尖牙间宽度在T1、T2和T3相互之间均有显著性差异.下颌第一磨牙间宽度(T1-T2,T1-T3)和下颌尖牙间宽度(T1-T2)有显著性增加.上颌牙弓周径、上颌第一磨牙及第一双尖牙颊倾度有显著性增加(T1-T2),但有少量复发(T2-T3).下颌牙弓周径、下颌第一磨牙和第一双尖牙颊倾度随治疗均有显著性增加.结论快速扩弓能够通过改变上颌牙弓宽度增加其牙弓周径,下颌舌弓配合固定矫治也能显著增加下颌牙弓周径.因此可以较好地解决边缘型牙列拥挤中牙量/骨量不调问题,并有利于建立良好的咬合关系和疗效的稳定.     

安氏Ⅰ类牙列拥挤采用非拔牙快速扩弓矫治的疗效观察

目的:观察安氏Ⅰ类轻中度牙列拥挤患者采用非拔牙快速扩弓矫治的临床疗效。方法:对9例安氏Ⅰ类轻中度牙列拥挤病例,采用上颌快速扩弓配合上下固定矫治技术进行非拔牙正畸治疗,分别在T1(正畸治疗前)、T2(快速扩弓3个月后)和T3(正畸治疗结束进入固定保持期)3个时间点进行头影测量分析。结果:鼻外侧点间距、上颌基点间距、上颌第一磨牙间距和下颌第一磨牙间距在快速扩弓前后(T1-T2)以及正畸治疗前后(T1-T3)有显著性增加,其中上颌第一磨牙间距在T2-T3时间点也有显著性变化。全面高、前上面高、腭平面倾度、Y轴角在T1-T2以及T1-T3间有显著性增大。下颌平面角的变化在3个时间点之间均有显著性差异。结论:快速扩弓能引起上颌骨横向宽度显著增加,其变化包括骨性(上颌基骨)和牙性(上颌第一磨牙)两部分。快速扩弓虽然会导致上、下颌骨的向下旋转,但由于其变化量的绝对值不超过2mm或1°,因此可认为并无临床意义。快速扩弓不会引起上下颌骨矢状向的显著改变。     

上颌铸造式Hyrax快扩后鼻上颌复合体三维形态变化的锥体束CT观察

目的 使用锥体束CT(Cone-Beam computed tomography,CBCT)评估生长期儿童快速扩弓后鼻-上颌复合体、牙槽骨和牙齿的变化.方法 30例(男13例,女17例,年龄11.0±1.5岁)上牙弓狭窄的患者,经过上颌铸造式Hyrax快速扩弓,扩弓前后拍摄CBCT,重建上颌尖牙区和第一磨牙区三维结构,分别测量颌骨、牙槽骨在不同平面的变化以及磨牙间宽度和倾斜角度的变化,进行配对样本t检验.结果 铸造式Hyrax快扩后颌骨变化明显,骨性扩弓∶牙性扩弓=1∶1,鼻腔宽度平均增加(3.88±1.92) mm,第一磨牙区牙槽骨宽度平均增加(5.72±1.86) mm,差异有统计学意义(P＜0.001),磨牙颊向倾斜度右侧平均增加(2.12±3.99)°,左侧平均增加(3.27±4.32)°,差异有统计学意义(P＜0.05).结论 上颌铸造式Hyrax快扩对生长发育期患者鼻-上颌复合体的作用主要表现为鼻腔、颌骨宽度增加和牙槽骨改建.     

单侧完全性唇腭裂术后患者牙弓间宽度不调的矫治

目的　通过对单侧完全性唇腭裂术后患者上下颌间牙弓宽度不调的研究及对患者正畸治疗的临床观察 ,总结该类患者正畸治疗的特点。方法　对 4 8例单侧完全性唇腭裂术后患者进行临床检查 ,记录其上下牙弓间的宽度关系 ;根据患者错情况制定不同的治疗方案进行临床治疗。结果　 (1)单侧完全性唇腭裂术后患者中出现上下颌牙弓宽度不调的比率为 6 0 .4 % ,双侧后牙反为 33.3% ,单侧后牙反为 16 .7%。男女之间差异无显著性。 (2 )宽度不调以双尖牙区为重 ,上尖牙区是扩弓治疗的重点。 (3)磨牙区牙弓宽度的不协调常较轻微 ,一些患者甚至上颌最后磨牙区略宽 ,对 5例患者 (占 10 4 % )进行了上颌磨牙的腭向移动。结论　单侧完全性唇腭裂患者正畸治疗中上颌多需扩弓 ,且扩弓潜力较大。对于严重拥挤的患者 ,拔牙决定应在扩弓后作出。扩弓治疗应在牙槽突植骨前进行 ,扩弓后需延长保持时间     

上颌快速扩弓联合固定矫治器治疗的稳定性研究

目的 观察患者接受上颌快速扩弓联合直丝弓矫治器治疗后覆牙合、覆盖及上牙弓宽度的变化。方法 选择2003年2月—2008年1月于青岛市口腔医院进行治疗的患者37例（男19例,女18例）,将患者分为4个不同的时期进行测量（N1:治疗前;N2:进行上颌快速扩弓后;N3:固定治疗后;N4:保持1年后）。分别测量每位患者的上颌尖牙间宽度、前磨牙间宽度、磨牙间宽度,并对前牙覆盖和覆牙合进行测量。患者的平均年龄（11.3±1.4）岁（10.2～15.3岁）。结果 治疗全部结束后、尖牙间宽度、前磨牙间宽度、磨牙间宽度、覆盖、覆牙合分别增加（2.6±2.3）mm、（3.7±2.1）mm、（5.2±2.5）mm、（0.3±0.6）mm、（-0.1±1.6）mm,患者复发率在尖牙宽度为47%,前磨牙间宽度为21％,磨牙间宽度为10%,覆盖复发率为9%,覆牙合为13%。结论 患者经过上颌快速扩弓后,在固定矫治阶段复发明显,保持阶段也有一定程度的复发。 上颌快速扩弓能够减小覆牙合,增加覆盖。     

快速扩弓和Damon技术非拔牙矫治牙列拥挤的比较研究

目的:分析比较快速扩弓(RPE)技术和Damon技术用于非拔牙矫治牙列拥挤的临床疗效.方法:选取19例骨性Ⅰ类中度牙列拥挤的青少年患者,进行非拔牙正畸治疗,其中9例采用上颌快速扩弓配合直丝弓矫治技术,10例采用Damon矫治技术.对2组患者正畸治疗前、后作模型和X线头影测量分析.使用SPSS15.0软件包作t检验,分析治疗前、后及2组间的差异.结果:治疗后,上、下颌尖牙间宽度RPE组分别增加了2.9mm和1.3mm,而Damon组没有显著变化.上、下颌后牙区牙弓宽度2组均有显著增加(P<0.05),其中,上颌第一前磨牙间宽度和下颌磨牙间宽度的增加,2组间无显著差异.上颌第一磨牙间宽度RPE组增加了5.3mm,显著大于Damon组的3.1mm;而下颌前磨牙间宽度的增加量Damon组为4.5mm,显著大于RPE组的1.5mm(P<0.05).治疗后,上、下磨牙均有显著颊向倾斜(P<0.05),Damon组和RPE组无显著差异.但上、下前磨牙的颊向倾斜量Damon组显著大于RPE组(P<0.05).RPE组上颌基骨宽距增加了2.1mm.显著大于Damon组(0.6mm)(P<0.05).h、下切牙突角U1-NA和IMPA的变化,Damon组分别为9.2°和7.5°,RPE组无显著改变,2组间有显著差异(P<0.05).结论:快速扩弓和Damon技术都能有效地通过增加牙弓宽度,成功达到非拔牙矫治中度牙列拥挤的目的.Damon技术主要以颊倾前磨牙和磨牙来增大后牙的牙弓宽度,同时伴有切牙唇向倾斜;快速扩弓能扩大上颌基骨和整个上颌牙弓宽度,并可维持前牙直立.     

改良唇挡单侧扩弓后牙槽骨高度与厚度变化的CBCT研究

目的 研究改良唇挡单侧扩弓后裂侧牙槽骨高度与厚度的变化.方法 对年龄在12～16岁应用改良唇挡完成单侧扩弓的18名单侧完全性唇腭裂患者扩弓前后的CBCT图像进行重建,测量扩弓后裂侧牙槽骨高度与厚度,对测量结果进行统计学分析.结果 裂侧尖牙、第一、第二前磨牙颊、腭侧牙槽骨的高度均降低,其中尖牙变化量最大(P<0.01),尖牙颊侧骨开裂的患者增多.第一、第二前磨牙颊侧牙槽骨在釉牙骨质界下4mm、6mm处厚度增加,尖牙颊侧在6mm处骨厚度增加(P<0.01),在4mm处骨厚度减少(P<0.05),尖牙、第一、第二前磨牙腭侧牙槽骨厚度减少.结论 唇挡扩弓后,裂侧牙齿颊侧牙槽骨的高度降低,厚度增加.对于裂侧尖牙正畸治疗前后的牙周状况应该引起重视.     

单侧完全性唇腭裂患者牙弓宽度正畸扩弓治疗后的稳定性研究

目的探讨单侧完全性唇腭裂后牙反[牙合]患者正畸扩弓矫治后牙弓宽度的稳定性。方法已经完成保持的经过四角舌弓及固定矫治器正畸治疗的手术后单侧完全性唇腭裂患者20名（男性14名，女性6名），三维测量仪对治疗前、治疗后及保持后的研究模型进行尖牙间、第一、二双尖牙、第一磨牙间宽度以及基骨和牙槽弓宽度的测量。统计方法为配对资料的方差分析，两两比较用Fishe rLSD法。结果经过四角舌弓及固定矫治器治疗后单侧完全性唇腭裂患者上颌各段宽度均增加，差异有统计学意义；下颌除第一双尖牙外各段宽度变化不具统计学意义。正畸治疗后上颌牙弓宽度的增加在尖牙和双尖牙区大于磨牙区。保持结束后牙弓各段宽度较治疗后均有减小，其中上颌尖牙间宽度减小1．34±0．82mm（P〈0．05）、第一双尖牙间宽度减小1．52±0．78mm（P〈0．05）达到显著水平。但是保持结束后上颌各段的牙弓宽度仍大于治疗前，差异有统计学意义。结论经过四角舌弓及固定矫治器系统治疗后，单侧完全性唇腭裂患者上颌牙弓各段的宽度均显著增加；保持结束后上颌牙弓各段宽度虽有复发，但是大部分矫治结果能够保持。     

Multitomographic evaluation of the dental effects of two different rapid palatal expansion appliances

Rapid palatal expansion (RPE) is widely used in the treatment of transverse maxillary deficiencies. Generally, there are two types of RPE appliances: banded and bonded expanders. The purpose of this prospective study was to compare the dental effects of banded and bonded appliances. The study consisted of 23 patients (13 females and 10 males) with a bilateral maxillary deficiency. Twelve patients (seven females and five males) with a mean age of 14.8 +/- 0.3 years were treated with banded RPE and 11 patients (six females and five males) with a mean age of 15.1 +/- 0.7 years with bonded RPE. Multitomographic radiographs were taken before (T0) and at the end (T1) of expansion while the patients were wearing an acrylic mandibular appliance in which ball bearings and bars were embedded. Statistical analyses of the measurements at T0 and T1 were undertaken with a paired t-test, and the difference between the groups assesed with a Student's t-test. In both groups, the angle between the radiographic image of the bar and the axial inclination of the upper first premolar and molar teeth was (5.34 and 2.73 degrees for the right premolars, 5.17 and 2.28 degrees for the left premolars, 11.83 and 3.73 degrees for the right molars, and 9.75 and 5.64 degrees for the left molars in the banded and bonded groups, respectively. The distance from the vestibular cortical plate to the palatal root of these teeth (1.17 and 1.23 mm for the right premolars, 2.46 and 1.09 mm for the left premolars, 2.75 and 0.64 mm for the right molars, 2.23 and 0.96 mm for the left molars in the banded and bonded groups, respectively) increased (both P < 0.01). These increases indicated buccal tipping of the teeth. Comparison of the two groups showed that tipping of the first molar and premolar teeth in the banded group was significantly more than in the bonded group (P < 0.01 and P < 0.001, respectively).     

Stability of orthopedic and surgically assisted rapid palatal expansion over time

At the present time no reports are available on the stability between orthopedic and surgically assisted rapid palatal expansion. This study was designed to examine and compare the dental and skeletal changes over time for both orthopedic maxillary expansion and surgically assisted palatal expansion. The study was divided into two groups. Group one was orthopedically expanded and consisted of 14 males and 10 females. The ages ranged from 6 years to 12 years with a mean of 8.5 years. Group two received surgically assisted rapid palatal expansion and consisted of 12 males and 16 females with ages ranging from 13 years to 35 years and a mean age of 19.25 years. All 52 subjects were white, from the same geographic area, and were treated by the same two operators. Dental models and posterior anterior cephalograms were obtained immediately before and after expansion, at removal of the expansion device, and 1 year after removal of the appliance. A repeated measures analysis of variance test was applied to assess changes over time between groups. The surgical and nonsurgical techniques displayed similar trends over time although the surgical group contained a greater quantity of expansion. Both the orthopedic and the surgical groups showed stable results. (Am J Orthod Dentofacial Orthop 1998;114:638-45)     

Sagittal airway changes: rapid palatal expansion versus Le Fort I osteotomy during maxillary protraction

The purpose of the present study was to evaluate upper airway changes related to craniofacial changes induced by a facemask (FM) combined with Le Fort I osteotomy without down-fracture in Class III maxillary retrusion subjects (group 1) when compared with a similar group of subjects treated with traditional rapid palatal expansion and FM therapy. Pre- (T1) and post- (T2) protraction cephalometric radiographs of group 1 (10 females and 6 males; mean age 12.75 ± 1.91 years) and group 2 (7 females and 9 males; mean age 12 ± 1.7 years) were traced. The treatment duration was 149 ± 14 days (approximately 5 months) and 270 ± 46 days (approximately 9 months) for groups 1 and 2, respectively. A paired t-test for intergroup comparisons of values at T1, an independent samples t-test for intragroup comparisons of values at T1 and T2, and a non-parametric Mann-Whitney U-test for intergroup comparisons were used. To evaluate the relationship between changes in upper airway dimension and craniofacial morphology, a multiple-regression analysis was performed. Significant maxillary protraction along with clockwise rotation of the mandible was achieved in both groups. Counter-clockwise maxillary rotation was significant in group 1 (P < 0.05) but not in group 2. While nasopharyngeal measurements (PNS-ad1, PNS-ad2) showed significant increases (P < 0.05) as a result of treatment in both groups, oropharyngeal measurements did not change. Maxillary protraction, which was achieved in both groups but in a shorter period of time in group 2, improved nasopharyngeal but not oropharyngeal airway dimensions.     

Skeletal and dentoalveolar changes in the transverse dimension using microimplant-assisted rapid palatal expansion (MARPE) appliances

Conventional rapid palatal expansion (RPE) has been proven to be a reliable treatment for correcting transverse maxillary deficiency in young patients. However, side effects including dental tipping and risk of periodontal problem limited its application to young patients after the pubertal growth spurt. Surgically assisted rapid palatal expansion (SARPE), a supplement to RPE, could be applied in skeletally mature patients. However, SARPE was an invasive method, and the morbidity, risks and cost related to surgical treatment might discourage many adult patients. The use of Microimplant-Assisted Rapid Palatal Expansion (MARPE) appliance, which can potentially avoid surgical intervention, is gaining popularity in treatment of maxillary transverse deficiency (MTD) in young adolescent patients. However, the literature on the skeletal and dentoalveolar changes with this appliance is scarce. To evaluate the immediate skeletal and dentoalveolar changes in the transverse dimension with the maxillary skeletal expander (MSE), a MARPE appliance with hybrid anchorage, using cone-beam computed tomography (CBCT). Twenty-two patients (11 males and 11 females, mean age 14.97 ± 6.16 years) with transverse maxillary deficiency were treated using the MSE (Biomaterials Korea, Inc., Seoul, Korea). The appliance consisted of a central expansion screw that were welded to four tubes that served as guides for microimplant placement. The microimplants were 1.8 mm in diameter and 11 mm in length. The longer length of microimplants permitted bicortical engagement of the palatal and nasal floor, reducing the force transmitted to the anchored teeth during expansion. The appliance activation varied with age and skeletal maturity of the patient. The expansion was terminated when 2–3 mm of overexpansion was achieved. CBCT scans were taken before treatment (T1) and immediately after expansion (T2). Measurements were taken to evaluate the amount of total expansion, skeletal expansion, and angular dental tipping at the first molar region. A total expansion of 5.41 ± 2.18 mm was achieved, 59.23 ± 17.75% of which was attributed to skeletal expansion (3.15 ± 1.64 mm) with the first molars exhibiting buccal tipping of 2.56 ± 2.64°. The use of MARPE appliances such as MSE can be used to correct transverse maxillary deficiency in adolescent patients with minimal dentoalveolar side effects.     

快速扩弓结合方丝弓及前方牵引矫治骨性Ⅲ类错的临床分析

目的:探讨快速扩弓结合方丝弓技术及前方牵引装置治疗骨性Ó类错的方法和特点。方法:选择15例骨性Ó类错患儿,男6例,女9例,年龄815~12岁,均为替牙期。X线片显示主要为上颌骨发育不足。左手腕骨片显示为生长发育的高峰前期。结果:15例患者经平均9月的治疗,面型均明显改善,头影测量其骨骼改变主要为 SNA角增大,A点前移。结论:三者联合治疗骨性Ó类错可取得明显的骨骼及侧貌改变。     

手术辅助快速扩弓矫治上颌横向发育不足的临床疗效分析

目的:评价手术辅助快速扩弓矫治成人上颌横向发育不足病例牙齿和基骨的变化。方法:上颌发育不足患者20例(男13例,女7例)按年龄分为扩弓组和手术组,扩弓组(平均年龄12.51±0.82岁)行矫形快速扩弓治疗;手术组(平均年龄19.07±2.54岁)行手术协助快速扩弓治疗。所有患者治疗前后摄头颅定位正侧位片和咬合片,头影测量分析、比较。结果:两组病例均有明显的扩弓效果,手术组牙弓宽度增加更为显著,扩弓组牙弓长度增加明显,但组间均无显著性差异;治疗前后,手术组B点显著后移,而扩弓组B点前移,组间有显著性差异(P<0.05);治疗前后,手术组腭平面后旋,扩弓组腭平面前旋,组间有显著性差异(P<0.01);治疗前后,两组病例上颌切牙均内倾,组间无显著性差异。结论:手术协助快速扩弓治疗成人上颌横向发育不足,可取得良好的扩弓效果;对上下颌骨、上颌切牙在矢状面的改变更有利于III类错畸形的矫正;在病例的选择上,更适用于低角病例。     

快速扩弓联合前方牵引治疗早期骨性Ⅲ类错的临床研究

目的运用支架式快速扩弓器进行前方牵引,评价其软硬组织发生的变化。方法 15例替牙期患儿,年龄9～11岁,先进行快速扩弓1～2周,然后行前方牵引,治疗前、后摄头颅定位侧位片并进行头影测量分析。结果快速扩弓后进行前牵引治疗前、后结果差异有显著性,上颌骨及上牙弓均前移,软组织侧貌明显改善。结论在替牙期前方牵引联合快速扩弓治疗早期骨性Ⅲ类错可获得较多的骨骼变化,侧貌改善明显。     

Orthodontic and orthopaedic changes associated with treatment in subjects with Class III malocclusions

The aim of this study was to determine the cephalometric changes in subjects with Class III malocclusions after rapid palatal expansion (RPE) and facemask treatment. The 30 subjects presented with developing Class III malocclusions. The treatment group comprised 15 patients (eight girls and seven boys, mean age 11 years 6 months) who had undergone RPE and facemask therapy. The control group consisted of nine girls and six boys with a mean age of 11 years 8 months. Radiographs were take at the same time intervals for both groups, and the average treatment time was 15 months. A Wilcoxon test was used to determine significant differences before and after treatment, and a Mann-Whitney U-test to analyse differences between the treatment and control groups. In the sagittal plane, significant changes were observed in both groups. In the treatment group, the following dimensions increased significantly: A perpendicular to FHp (P < 0.001), ANS-PNS (P < 0.01), 6 perpendicular to FHp (P < 0.05); in the control group Go-Gn (P < 0.05) increased significantly. In the treatment group, SN/Go-Gn and SN/ANS-PNS had higher values and this finding was significant (P < 0.05). Managing developing Class III malocclusions with RPE and maxillary protraction presents favourable results, such as vertical and sagittal displacement of point A.     

Reports of pain by children undergoing rapid palatal expansion

PURPOSE: This study described and quantified the prevalence, timing, and intensity of pain during the expansion phase of rapid palatal expansion (RPE) in children and investigated whether pain was related to age, sex, or rate of expansion. METHODS: Ninety-seven children, 38 males and 59 females, between the ages of 5 to 13 years (median 7.7 years) undergoing RPE procedures with the Hyrax, Dentaurum, Newtown, PA, appliance were surveyed. The appliance was expanded with either one or two turns (1/4 mm/turn) per day based on the provider's preference. The child's pain response was measured no more than 5 minutes after each turn for the entire period of expansion using both the Facial Pain Scale and the Color Analog Scale. RESULTS: Ninety-eight percent of the children reported at least some pain during RPE. The highest levels of pain were reported during the first 10 turns with the greatest intensity during the first 6 turns and a steadily decreasing amount of pain thereafter. Pain medication was taken after 7% of the expansion turns in the study with the majority of children taking the medication during the first 6 turns. Forty-eight percent of the children took pain medication at least once during the expansion phase of RPE. There was no difference in either reported pain or use of pain medication based on age, sex, or stage of dentition. During the first 10 turns, children whose rate of expansion was two turns/day were more likely to report pain and take pain medication than children whose rate of expansion was one turn/day, thereafter there were no differences. CONCLUSIONS: The vast majority of children undergoing the active phase of rapid palatal expansion with a Hyrax appliance report pain. The pain generally occurs during the initial phase of expansion and diminishes thereafter, with two turns/day resulting in reports of pain greater than those expanding only once/day.