Long-term effects of rapid maxillary expansion: a posteroanterior cephalometric evaluation.

The aim of this study was to investigate long-term effects induced by rapid maxillary expansion (RME), followed by comprehensive orthodontic treatment, in a sample of 42 patients compared with normal growth changes in a sample of 20 subjects. Treated subjects underwent Haas-type RME with 2 turns a day (0.25 mm per turn) until the expansion screw reached 10.5 mm (about 21 days). The Haas expander was kept on the teeth as a passive retainer for an average of about 2 months. Immediately after the Haas expander was removed, fixed standard edgewise appliances were placed. Posteroanterior cephalograms were analyzed for each subject in both groups at T1 (pretreatment) and at T2 (long-term observation). The mean age at T1 was 11 years 10 months for both the treated and the control groups. The mean ages at T2 also were comparable (20 years 6 months for the treated group, and 17 years 8 months for the control group). The study included transverse measurements on dentoalveolar structures, maxillary and mandibular bony bases, and other craniofacial regions (nasal, zygomatic, orbital, and cranial). RME followed by edgewise appliance therapy appears to be an effective procedure to increase transverse facial dimensions in the long term, at both the skeletal and the dentoalveolar levels. Significant pretreatment deficiencies in maxillary width, maxillary incisor apex width, and maxillary first molar width remained corrected at a mean age of about 20 years. The initial deficiency in lateroorbital width was also eliminated.     

A long-term study on the expansion effects of the cervical-pull facebow with and without rapid maxillary expansion

This study evaluates the long-term stability of maxillary expansion achieved by widening the inner bow of a facebow, with or without concurrent rapid maxillary expansion (RME) (Haas type), followed by treatment with fixed edgewise appliances. The parent sample included 154 nonextraction patients who started their orthodontic treatment during a defined time period. The exclusion criteria reduced the number of patients to 61 in the cervical-pull facebow group (CFB) and 41 in the RME-CFB group. All subjects were in the late-mixed to early-permanent dentition stage at the start of treatment. Dental casts were measured using a digital imaging system at four different times: start of treatment (T1), end of active treatment (T2), end of retention (T3), and postretention follow up (T4). The RME-CFB protocol produced a greater increase in maxillary arch width (6.1 mm) than did the CFB protocol (4 mm). The RME-CFB protocol provided greater net maxillary arch perimeter increase than did expansion with an inner bow of a cervical facebow. The RME-CFB group had three mm more arch perimeter 10 years after treatment completion than did the CFB group. The stability of expansion achieved with an inner bow of a facebow was equal to that achieved with a Haas-type RME appliance. Both expansion protocols retained 90% of the initial intermolar expansion 15 years after expansion.     

A comparison of the effects of rapid maxillary expansion and fan-type rapid maxillary expansion on dentofacial structures

The aim of this study was to evaluate and compare the sagittal, transverse, and vertical effects of rapid maxillary expansion (RME) and fan-type RME on dentofacial structures. The study group consisted of 34 patients, 14 boys and 20 girls (average age 12.5 years), selected without considering their skeletal class and sex. The fan-type RME group comprised 17 subjects, who had an anterior constricted maxilla with a normal intermolar width. The RME group comprised 17 other subjects, who had a maxillary transverse discrepancy with a posterior crossbite. The records obtained for each patient included a lateral and a frontal cephalometric film, upper plaster models, and occlusal radiograph obtained before treatment (T1), after expansion (T2), and immediately after a three-month retention period (T3). The data obtained from the evaluation of the records before and after treatment, after treatment and after retention, and before treatment and after retention were compared using paired t-test. Further comparisons between the groups were made using Student's t-test. There was significantly greater expansion in the intercanine than in the intermolar width in the fan-type RME group as compared with the RME group. Downward and forward movement of the maxilla was observed in both groups. The upper incisors were tipped palatally in the RME group, but they were tipped labially in the fan-type RME group. There was significantly greater expansion in the nasal cavity and maxillary width in the RME group as opposed to the fan-type RME group.     

Short-term effects produced by rapid maxillary expansion and facemask therapy in Class III patients with different vertical skeletal relationships

Objective:To evaluate the dentoskeletal short-term effects of rapid maxillary expansion and facemask therapy (RME/FM) in a sample of Class III patients showing different vertical skeletal relationships.Materials and Methods:Seventy-nine patients (35 females and 44 males) having Class III malocclusion were consecutively treated using RME/FM therapy with application of the protraction force in a downward and forward direction and inclination of about 30° to the occlusal plane. All patients were evaluated at the beginning (T1; mean age, 7.7 years) and at the end (T2; mean age, 9.2 years) of orthopedic therapy and divided into three groups according to their vertical skeletal relationships: normal group (NG), hypodivergent group (HypoG), and hyperdivergent group (HyperG). Statistical comparisons between the three groups were performed on the starting forms (T1), the final forms (T2), and the treatment changes (T1–T2) using the ANOVA with Tukey''s post hoc tests.Results:Favorable modification in terms of maxillary advancement (changes in SNA ranging from 1.4° to 1.8°) and intermaxillary sagittal skeletal relationships (changes in Wits appraisal ranging from 2.5 mm to 3.5 mm) were recorded in all groups. The three groups showed no statistically significant differences in changes in either sagittal or vertical skeletal variables.Conclusions:The various vertical skeletal features do not influence the short-term outcomes of RME/FM therapy.     

Treatment effects of bonded RME and vertical-pull chincup followed by fixed appliance in patients with increased vertical dimension.

INTRODUCTION: The aim of this study was to investigate the effectiveness of vertical-pull chincup (VPCC) therapy during an initial rapid maxillary expansion (RME) phase, followed by a second phase of comprehensive orthodontic therapy in growing subjects with mild-to-severe hyperdivergent facial patterns. METHODS: The records of 29 subjects treated with bonded RME combined with VPCC followed by a fixed-appliance phase with continued use of VPCC were compared with a group of 29 well-matched patients treated with bonded RME only. Lateral cephalograms were analyzed before the start of treatment (T1), before the second phase of treatment (T2), and after the second phase of treatment (T3). Mean age at T1 was approximately 9 years for both groups. Total treatment period (phase 1, interim phase, and phase 2) was 5.7 years for the VPCC group and 6.2 years for the bonded RME-only group. Statistical comparison between the 2 groups was performed by means of independent sample t tests on the T2-T1, T3-T2, and T3-T1 changes. Cervical vertebral maturation stages were assessed at T1, T2, and T3. RESULTS: The VPCC induced significantly smaller increases in mandibular plane angle of about 2 degrees , lower anterior facial height of about 2.5 mm, and total anterior facial height of about 3.5 mm, compared with the RME-only subjects. These outcomes reflect the therapeutic changes that occurred during phase 1 treatment; phase 2 treatment was not associated with any significant difference in treatment response. No statistically significant differences in vertical dentoalveolar changes were concurrent with the vertical skeletal changes in the subjects treated with the VPCC compared with the RME-only group. CONCLUSIONS: The clinical significance of VPCC wear over 2 phases of treatment (5.7 years) appears to be limited. The VPCC was most effective during the initial (RME) phase of treatment and of little benefit during the fixed appliance phase.     

Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances.

In this cephalometric investigation, we compared the long-term effects of an initial phase of rapid maxillary expansion and facemask (RME/FM) therapy followed by comprehensive edgewise therapy with the effects of growth in untreated, matched controls. The treated sample consisted of 34 patients who underwent RME/FM treatment before the pubertal growth spurt (average age, 8 years 3 months at the beginning of treatment). At the final observation period (average age, 14 years 10 months), all patients were in decelerative growth phases as determined by the cervical vertebral maturation (CVM) method. After the first 10 months of active treatment, significant favorable changes in both the maxillary and the mandibular skeletal components were noted. The forward movement of the maxilla was 1.8 mm greater than in the controls, mandibular projection was reduced by almost 3 mm, and the relative sagittal intermaxillary discrepancy improved by 4.3 mm, as measured by the Wits appraisal. During the posttreatment period, the treated and untreated Class III subjects generally grew similarly, although the skeletal relationship of the maxilla to the mandible remained unchanged in the RME/FM group, whereas the controls had an increased skeletal discrepancy of 3.0 mm. Over the long term, there was a slightly greater increase in midfacial length (1.6 mm) in the treatment group than in the controls. Similarly, the distance from Point A to nasion perpendicular decreased by 1.2 mm in the treated group. The overall increase in mandibular length was 2.4 mm less in the RME/FM group than in the controls, and mandibular projection relative to nasion perpendicular was 3.0 mm less in the treated group. The change in the Wits appraisal was substantial between groups (6.1 mm), with an improvement in the intermaxillary relationship in the treated group (3.4 mm); the Wits appraisal worsened (-2.7 mm) in the untreated controls. No clinically significant differences were observed between the groups in the vertical dimension. Overjet increased significantly in the treated group relative to the controls (4.4 mm), whereas the molar relationship decreased significantly (-3.9 mm). It appears that the favorable skeletal change observed over the long term is due almost entirely to the orthopedic correction achieved during the RME/FM protocol. During the posttreatment period that includes the pubertal growth spurt, craniofacial growth in RME/FM patients is similar to that of untreated Class III controls. Aggressive over-correction of the Class III skeletal malocclusion, even toward a Class II occlusal relationship, appears to be advisable, with the establishment of positive overbite and overjet relationships essential to the long-term stability of the treatment outcome.     

Long-term evaluation of rapid maxillary expansion and bite-block therapy in open bite growing subjects: A controlled clinical study

Objective:To evaluate the long-term effects of rapid maxillary expansion (RME) and posterior bite block (BB) in prepubertal subjects with dentoskeletal open bite.Materials and Methods:The treatment group (TG) comprised 16 subjects (14 girls, 2 boys) with dentoskeletal open bite with a mean age of 8.1 ± 1.1 years treated with RME and BB. Three consecutive lateral cephalograms were available before treatment (T1), at the end of the active treatment with the RME and BB (T2), and at a follow-up observation at least 4 years after the completion of treatment (T3). The TG was compared with a control group (CG) of 16 subjects (14 girls, 2 boys) matched for sex, age, and vertical skeletal pattern. An independent sample t-test was used to compare the T1 to T3, T1 to T2, and T2 to T3 cephalometric changes between the TG and the CG.Results:In the long term, the TG showed a significantly greater increase in overbite (+1.8 mm), reduced extrusion of maxillary and mandibular molars (−3.3 mm), and, consequently, a significant decrease in facial divergence (−2.8°) when compared with untreated subjects.Conclusions:The RME and BB protocol led to successful and stable recovery of positive overbite in 100% of the patients considered. Correction of open bite was associated with reduced extrusion of maxillary and mandibular molars with a significant improvement in vertical skeletal relationships when compared with the CG.     

Skeletal alterations associated with the use of bonded rapid maxillary expansion appliance

Bonded maxillary expansion appliances have been suggested to control increases in the vertical dimension of the face after rapid maxillary expansion (RME). However, there is still no consensus in the literature about its real skeletal effects. The purpose of this prospective study was to evaluate, longitudinally, the vertical and sagittal cephalometric alterations after RME performed with bonded maxillary expansion appliance. The sample consisted of 26 children, with a mean age of 8.7 years (range: 6.9-10.9 years), with posterior skeletal crossbite and indication for RME. After maxillary expansion, the bonded appliance was used as a fixed retention for 3.4 months, being replaced by a removable retention subsequently. The cephalometric study was performed onto lateral radiographs, taken before treatment was started, and again 6.3 months after removing the bonded appliance. Intra-group comparison was made using paired t test. The results showed that there were no significant sagittal skeletal changes at the end of treatment. There was a small vertical skeletal increase in five of the eleven evaluated cephalometric measures. The maxilla displaced downward, but it did not modify the facial growth patterns or the direction of the mandible growth. Under the specific conditions of this research, it may be concluded that RME with acrylic bonded maxillary expansion appliance did promote signifciant vertical or sagittal cephalometric alterations. The vertical changes found with the use of the bonded appliance were small and probably transitory, similar to those occurred with the use of banded expansion appliances.     

Effects of a modified acrylic bonded rapid maxillary expansion appliance and vertical chin cap on dentofacial structures

The aim of this study was to determine the sagittal, transverse, and vertical effects of a modified acrylic bonded rapid maxillary expansion (RME) device used with a vertical chin cap on dentofacial structures. The study group consisted of 34 patients (25 girls and 9 boys) who were selected without regard to their skeletal class and gender. All subjects had permanent dentition (mean age, 12.7 years) and needed maxillary expansion. Study Group I (RME only) was composed of 17 subjects, and study Group II (RME with vertical chin cap) was composed of 17 subjects. Twenty-nine measurements were made on the patients' cephalometric films and plaster models. The means and standard deviations for linear and angular cephalometric measurements were analyzed statistically, and intra-group and inter group changes were evaluated by paired and Student's t-tests using SPSS 10.1 for windows. We found that the maxilla moved anteriorly relative to the anterior cranial base. The nasal width, maxillary width, intercanine width, mandibular intermolar width, maxillary intermolar width, and overjet all increased, while the upper molars tipped buccally in both groups. In Group I, the mandible rotated posteriorly, the lower anterior facial height increased, and the overbite decreased. These effects were reduced in Group II. We conclude that the vertical chin cap is an effective appliance for preventing the adverse vertical effects of RME in patients with a crossbite and a vertical growth pattern.     

Effects of rapid maxillary expansion on nasal mucociliary clearance

Objective:To evaluate the changes in nasal mucociliary clearance in orthodontic patients after rapid maxillary expansion (RME) therapy.Materials and Methods:Forty-two children (25 boys and 17 girls) participated in this study. The RME group consisted of 21 patients (mean age, 13.8 years), who had undergone RME at the initiation of orthodontic treatment. The control group consisted of 21 subjects (mean age, 13.6 years), who were attending the department of orthodontics for active orthodontic treatment. The nasal mucociliary clearance was assessed by the saccharin test. Saccharin transit times (STTs) were measured for each treated subject before expansion (T1), after RME (T2), and after a 3-month retention period (T3). Records were obtained at the same time intervals for each group.Results:The STT decreased significantly in the RME group after expansion and retention (P < .05). A statistically significant difference was found when the STTs of the control and RME groups were compared after expansion and retention (P < .05).Conclusions:The STTs of young orthodontic patients with maxillary narrowness and without any history of nasal or systemic disease were within normal limits. However, RME increased the mucociliary clearance in patients who had maxillary narrowness, having positive effects on nasal physiology and increasing nasal cavity volume.     

Soft tissue profile changes after rapid maxillary expansion with a bonded expander

The aim of this study was to evaluate the short- and long-term treatment effects of rapid maxillary expansion (RME) on the soft tissue facial profile of subjects treated with a modified acrylic-hyrax device. The sample comprised 10 males and 10 females in the mixed dentition. Their average age was 9.3 years ± 10 months pre-treatment (T1), with a narrow maxilla and posterior crossbite, treated with a modified fixed maxillary expander with an occlusal splint. Lateral cephalometric radiographs obtained at T1, immediately post-expansion (T2), and after retention (T3) were used to determine possible changes in the soft tissue facial profile. The means and standard deviations for linear and angular cephalometric measurements were analysed statistically using analysis of variance and Tukey's test (α = 0.05). The measurements at T2 differed significantly from those at T1 and T3. However, RME did not produce any statistically significant alteration (P > 0.05) in the soft tissue profile for any of the cephalometric landmarks evaluated when compared at T1 and T3. The use of a fixed expander associated with an occlusal splint did not cause significant alterations in the soft tissue facial profile at T3. This modified device is effective for preventing the adverse vertical effects of RME such as an increase anterior face height in patients with a crossbite.     

Does rapid maxillary expansion affect the eruption of upper third molars?

OBJECTIVE: To test the hypothesis that there is no difference in the movement of the upper third molars between rapid maxillary expansion (RME) and non-RME patients. MATERIALS AND METHODS: This study was performed on 30 patients divided into two groups. The study group included 20 patients who had maxillary narrowness and bilateral maxillary third molars and who had undergone RME application. The control group of 10 patients had a bilateral crossbite, had bilateral maxillary third molars, and did not receive orthodontic treatment. The records included lateral and frontal cephalometric films and maxillary plaster models. In the study group, records were taken before expansion (T1), after expansion (T2), and at the retention period (T3). T2 records were not taken in the control group because this period was too short to observe any changes. Friedman tests were used to observe within groups, and the Mann-Whitney U-test was used to see the differences between groups on films and casts. RESULTS: Frontal films showed that vertical eruption occurred after the retention period in the RME cases. Cephalometric films revealed that the angular eruption occurred immediately after expansion. However, the results were not significant with respect to the control group. CONCLUSION: The hypothesis was rejected. Rapid maxillary expansion affects maxillary third molar movement during and after the RME procedure. RME may indicate upper third molar eruption, but the final position of third molar was not different compared to the normal growth pattern.     

Dentofacial effects of two facemask therapies for maxillary protraction: Miniscrew implants versus rapid maxillary expanders

Objective:To compare the dentofacial effects of maxillary protraction with two facemask therapies in growing Class III patients: facemask in association with miniscrew implants (MSI/FM) and facemask with rapid maxillary expanders (RME/FM).Materials and Methods:Forty-three Chinese patients with Class III malocclusion and maxillary deficiency were randomly assigned to a MSI/FM sample of 20 patients and a RME/FM sample of 23 subjects. The changes in dentofacial cephalometric variables from the beginning (T1) to the end of treatment (T2) were compared with t-test for paired samples in both groups and for independent samples between the two groups.Results:No significant cephalometric differences were observed between the two groups in active treatment effects except for maxillary dental variables. However, significant favorable changes in both maxillary and mandibular skeletal components were noted in two groups after treatment. Sagittal measurements showed the maxilla was advanced, mandibular projection was reduced, and the relative sagittal intermaxillary discrepancy improved. Patients experienced additional unfavorable outcomes of clockwise rotation of the mandible as well as retroclination of the lower incisors. The soft tissue profile was improved remarkably in both groups. Proclination of the maxillary incisors and mesialization of the maxillary dentition were significantly different between the two groups. The increases in U1-SN, U1-VR, and U6-VR were 6.41°, 2.78 mm, and 1.24 mm less in the MSI/FM group than in the RME/FM group, respectively.Conclusions:Compared with the RME/FM therapy, the MSI/FM protocol using a smaller magnitude of protraction force improves skeletal relationships and soft tissue profile and reduces the undesired dentoalveolar effects.     

Cephalometric evaluation of rapid and slow maxillary expansion in patients with BCLP: Secondary data analysis from a randomized clinical trial

Objective:To compare the dentoskeletal effects of rapid (RME) and slow (SME) maxillary expansion in patients with bilateral complete cleft lip and palate (BCLP).Materials and Methods:This was a secondary analysis of a previous randomized controlled trial (RCT). Forty-six patients (34 male, 12 female) with BCLP and posterior crossbite (mean age of 9.2 years) were randomly assigned to two study groups. Group RME comprised subjects treated with Haas/Hyrax expander. Group SME included patients treated with quad-helix appliance. Cone-beam computed tomography (CBCT) was performed before expansion (T1) and after appliance removal at the end of a 6-month retention period (T2) for a previous RCT that compared the transverse skeletal effects of RME and SME. CBCT-derived cephalometric images were generated and cephalometric analysis was performed using Dolphin Imaging Software (Chatsworth, Calif). Intergroup comparisons were performed using t tests (P < .05).Results:Baseline forms were similar between groups. No significant differences between RME and SME groups were found.Conclusions:Rapid and slow maxillary expansion produced similar sagittal and vertical changes in patients with BCLP. Both Haas/Hyrax and quad-helix appliances can be used in patients with vertical facial pattern. Clinical relevance: RME and SME can be equally indicated in the treatment of maxillary arch constriction in patients with BCLP.     

Arch width changes with a rapid maxillary expansion appliance anchored to the primary teeth

OBJECTIVE: To examine the dimensional changes after rapid maxillary expansion (RME) carried out in the transitional dentition with the primary teeth as anchorage. MATERIALS AND METHODS: Group A was composed of 31 consecutive transitional dentition patients with posterior quadrant crossbites treated with a Haas-type RME appliance anchored on the maxillary primary molars and canines. No treatment was administered after palatal expansion. Study models were made before RME (T1), at appliance removal (T2), and at least 1 year after appliance removal (T3). A control sample of 60 individuals with posterior quadrant crossbites who had had no orthodontic treatment was categorized into group B (30 individuals with an average age comparable with the treated patients at T2) and group C (30 individuals with an average age comparable with the treated patients at T3). RESULTS: Permanent molar crossbites were corrected at T2, and this correction was maintained at T3 in all patients. The mean permanent maxillary intermolar width was 42.6 +/- 2.3 mm at T1, 46.7 +/- 1.9 mm at T2 (P < .01), and 46.3 +/- 1.8 mm at T3 (P < .01) in group A; 42.9 +/- 2.7 mm (P < .01) in group B; and 44.4 +/- 3.0 (P < .01) in group C. Premolar and canine widths were slightly wider than the control at T3. CONCLUSION: To avoid undesirable treatment-induced effects on maxillary permanent molars, a stable transverse correction could be achieved with the RME appliance anchored on the primary teeth.     

Mandibular cervical headgear vs rapid maxillary expander and facemask for orthopedic treatment of Class III malocclusion

OBJECTIVE: To compare the effectiveness of the rapid maxillary expander and facemask (RME/ FM) and mandibular cervical headgear (MCH) protocols when followed by fixed appliances and evaluated at a postpubertal observation in patients with dentoskeletal Class III malocclusion. MATERIALS AND METHODS: The sample treated with the RME/FM followed by fixed appliances included 32 patients (12 boys and 20 girls). The sample treated with the MCH followed by fixed appliances included 26 patients (eight boys and 18 girls). Cephalometric analysis was performed at T(1) (before treatment) and T(2) (after the first phase of orthopedic therapy and the second phase of fixed appliances). T(1)-T(2) changes were evaluated by means of t-tests. RESULTS: Midfacial length, mandibular length, and the sagittal position of the chin all showed significantly smaller increases in the MCH group than in the RME/FM group. The amount of increase in the overjet was also significantly smaller in the MCH group, whereas the amount of molar correction was greater. The upper incisors were significantly less proclined and the lower incisors were significantly less retroclined in the MCH group when compared with the RME/FM group. CONCLUSIONS: RME/FM therapy appears to be indicated in Class III patients with a component of maxillary retrusion, whereas MCH therapy is preferable in patients with mandibular prognathism.     

Rapid maxillary expansion in growing patients. Hyrax versus transverse sagittal maxillary expander: a cephalometric investigation

The aim of this retrospective study was to cephalometrically evaluate and compare the skeletal and dental effects of a transverse sagittal maxillary expander (TSME) and a Hyrax-type expander (RME) in children with maxillary hypoplasia. Fifty subjects (26 males and 24 females), aged from 6 to 15 years, with a maxillary crossbite caused by basal apical narrowness, were divided into two equal groups. Twenty-five were treated with a TSME and the other 25 with a RME. For each patient, a lateral cephalogram was obtained before treatment (T0) and at the end of the retention period (T1). Changes in the two groups during the observation period were calculated, compared, and statistically analysed with a paired samples t?-test. In the TSME group, SNP-A, I?SN, and I?FH and in the RME group SN-SNP.SNA, N-Me, and U6.PP displayed a statistically significant increase (P < 0.05). The increase in SNP-A, I?SN, and I?FH in the TSME group was significantly greater following treatment than in the RME group. The results support the use of the TSME to produce skeletal changes and dentoalveolar modification and to correct maxillary hypoplasia. It was also demonstrated that in patients with an anterior open bite, the use of the TSME is not contraindicated as the anterior vertical dimension did not increase significantly.     

Comparison of the effects of RME and fan-type RME on nasal airway by using acoustic rhinometry

Objective:To evaluate and compare the nasal airway changes following rapid maxillary expansion (RME) and fan-type RME using acoustic rhinometry (AR).Materials and Methods:The study sample consisted of three groups. The RME group comprised 15 subjects with maxillary transverse discrepancies and posterior crossbites. The fan-type RME group comprised 15 subjects, who had an anteriorly constricted maxilla with a normal intermolar width. The third group included 15 patients who had an ideal occlusion and received no orthodontic treatment and served as the control group. AR was used to measure nasal volume and the minimal cross-sectional area (MCA) before expansion (T1), after expansion (T2), and 6 months after expansion (T3). Each AR recording was performed with and without the use of a decongestant. Two-way analysis of variance was used to determine differences among the groups and three-way analysis of variance was used for the differences between groups. If evidence of statistically significant differences was found, a Bonferroni test was used.Results:The results showed that nasal volume and MCA were significantly increased with RME and fan-type RME immediately after expansion (P < .05). At the end of retention, nasal volume and MCA values of RME showed significant differences with both expansion fan-type RME and control groups (P < .05).Conclusions:RME and fan-type RME had similar effects on the nasal airway immediately after expansion. The increase in nasal volume and MCA was more stable in the RME group than in the fan-type RME group at the end of the retention period.     

Nonextraction treatment with rapid maxillary expansion and mandibular symphyseal distraction osteogenesis and vertical skeletal dimensions

OBJECTIVE: To investigate the effects of rapid maxillary expansion (RME) and mandibular symphyseal distraction osteogenesis (MSDO) on vertical dimensions of the face. MATERIALS AND METHODS: Fourteen patients, nine girls and five boys, underwent RME and MSDO procedures. Distraction was carried out at a rate of 1 mm per 24 hours with a tooth-borne appliance. The amount of distraction was 7 mm for each patient. Standardized lateral cephalograms were taken at the following time periods: before treatment (T0), after RME (T1), at the completion of MSDO (T2), and at the end of fixed orthodontic treatment (T3). The data were evaluated by using a general linear model of repeated-measures analysis of variance and paired t-tests at the 95% confidence level. RESULTS: RME significantly increased the vertical dimensions of the face and decreased the overbite (P < .001). Although the vertical parameters of the face on the lateral cephalogram decreased after MSDO, these decreasing effects were statistically insignificant just for the distances measured from the horizontal reference line to the chin points. In other words, MSDO decreased the vertical skeletal dimensions that were increased by RME, but this neutralizing effect of MSDO was not as much as the increase caused by RME. CONCLUSION: Treatment modalities (RME, MSDO, and fixed orthodontic treatment) described in this study, in total, had little effect on the vertical skeletal measurements of the face.     

成人RME矫治后长期稳定性的初步探讨

目的　通过对 2 1例成人经上颌快速扩大 (RME)矫治后的牙关系进行了随访观察 ,旨在对成人RME矫治后的长期稳定性进行初步探讨。材料　本研究对象由 2 1例经RME矫治的成人所构成。均经Hass型扩弓器扩弓和方丝弓矫治器联合矫治。在矫治前 (T1 )和矫治结束时 (T2 )分别制取牙石膏模型 ,并戴用Hawley式保持器进行保持。保持器戴用时间最短 1年 ,最长 5年。在停止戴用保持器后至少 1年 (大部分 5年 ) ,制取随访模 (T3)。方法　对 2 1例保持前后 (T2 ,T3)的模型进行以下测量 :1 上颌第一磨牙间宽度 ;2 上颌第二前磨牙间宽度 ;3 上颌第一前磨牙间宽度 ;4 上颌尖牙间宽度 ;5 第一磨牙颊侧牙槽间宽度。对所测量数据用Sigmastate统计软件进行配对t检验。结果　观察所有样本保持前后的模型 ,未见有样本在保持后 ,其后牙咬合关系为反关系。但测量数据的统计结果显示 :除第一磨牙间宽度外其余指标的变化均有统计学意义。结论　成人经RME矫治保持后 ,虽有轻度复发 ,但未见有复发至后牙反的状况 ,故总体疗效是基本稳定的