Transverse Changes Determined by Rapid and Slow Maxillary Expansion (PDF)

ORIGINAL ARTICLE R. Martina Transverse changes determined by I. Cioffi rapid and slow maxillary expansion – M. Farella P. Leone a low-dose CT-based randomized P. Manzo...

ORIGINAL ARTICLE R. Martina Transverse changes determined by I. Cioffi rapid and slow maxillary expansion – M. Farella P. Leone a low-dose CT-based randomized P. Manzo controlled trial G. Matarese M. Portelli R. Nucera G. Cordasco Authors' affiliations: Martina R., Cioffi I., Farella M., Leone P., Manzo P., Matarese G., Portelli M., R. Martina, I. Cioffi, M. Farella, P. Leone, Nucera R., Cordasco G. Transverse changes determined by rapid and slow P. Manzo, Department of Oral Sciences, maxillary expansion – a low-dose CT-based randomized controlled trial Section of Orthodontics and Temporomandibular Disorders, University Orthod Craniofac Res 2012.  2012 John Wiley & Sons A ⁄ S of Naples Federico II, Naples, Italy M. Farella, Department of Oral Sciences, Structured Abstract Discipline of Orthodontics, University of Otago, Dunedin, New Zealand Objectives – To compare transverse skeletal changes produced by rapid G. Matarese, M. Portelli, R. Nucera, (RME) and slow (SME) maxillary expansion using low-dose computed G. Cordasco, University of Messina, School tomography. The null hypothesis was that SME and RME are equally of Dentistry, Messina, Italy effective in producing skeletal maxillary expansion in patients with posterior Correspondence to: crossbite. Iacopo Cioffi Setting and Sample Population – This study was carried out at the Department of Oral Sciences, Section of Department of Oral Sciences, University of Naples Federico II, Italy. Twelve Orthodontics and Temporomandibular patients (seven males, five females, mean age ± SD: 10.3 ± 2.5 years) disorders University of Naples Federico II were allocated to the SME group and 14 patients (six males, eight females, Via Pansini 5 mean age ± SD: 9.7 ± 1.5 years) to the RME group. 80131 Napoli Materials and Methods – All patients received a two-band palatal Italy E-mails: [email protected]; expander and were randomly allocated to either RME or SME. Low-dose [email protected] computed tomography was used to identify skeletal and dental landmarks and to measure transverse maxillary changes with treatment. Results – A significant increase in skeletal transverse diameters was found in both SME and RME groups (anterior expansion = 2.2 ± 1.4 mm, posterior expansion = 2.2 ± 0.9 mm, pterygoid expansion = 0.9 ±0.8 mm). No significant differences were found between groups at anterior (SME = 1.9 ± 1.3 mm; RME = 2.5 ± 1.5 mm) or posterior (SME = 1.9 ± 1.0 mm; RME = 2.4 ± 0.9 mm) locations, while a statistically significant difference was measured at the pterygoid processes (SME = 0.6 ± 0.6 mm; RME = 1.2 ± 0.9 mm, p = 0.04), which was not clinically relevant. Conclusion – Rapid maxillary expansion is not more effective than SME in expanding the maxilla in patients with posterior crossbite. Date: Accepted 13 February 2012 Key words: low-dose computed tomography; palatal expansion; DOI: 10.1111/j.1601-6343.2012.01543.x randomized controlled trial  2012 John Wiley & Sons A ⁄ S Martina et al. Rapid vs. slow maxillary expansion Introduction marks and low radiation exposure for the patient (17–19). The purpose of this study was to compare Unilateral or bilateral posterior crossbite (PXB) is the transverse skeletal changes determined by a common malocclusion in primary and early RME and SME by means of low-dose computed mixed dentition. Previous reports suggest that it tomography (CT). The null hypothesis was that occurs in 8–20% of children (1, 2). Treatment is SME and RME were equally effective in increasing recommended in growing patients to improve skeletal maxillary transverse widths in growing occlusal relationships (3, 4), to prevent the patients affected with posterior crossbite. development of mandibular skeletal asymmetries (5), and to improve jaw function (6). PXB is fre- quently associated with a maxillary transverse Material and methods deficiency (3). Thus, maxillary expansion is often advocated, which can be achieved using several The study was a randomized controlled trial. The therapeutic approaches (7–9). power analysis was based upon previous esti- In growing patients, rapid maxillary expansion mates of RME transverse skeletal effects (20) and (RME) and slow maxillary expansion (SME) are indicated that 12 patients were needed for each routinely used, whereas in adults, surgically treatment group (difference to detect ‡2.5 mm, assisted RME is the treatment of choice. SD = 2.0 mm, a = 0.05, power 80%). The biological and clinical effects of RME and Patients up to 13 years old (males) and 12 years SME have been investigated in several studies (9– old (females) who were seeking orthodontic 13). RME occurs by heavy and continuous forces, treatment were screened by a clinical instructor applied in short lapses of time, known to produce (PM) of the Postgraduate Programme in Ortho- immediate significant effects on maxillary trans- dontics at the Department of Orthodontics, Uni- verse widths. In contrast, SME occurs by more versity of Naples Federico II, Italy, between May intermittent and lower forces that are applied over 2006 and October 2007. Subjects with erupted longer periods. According to the literature, both upper permanent first molars and unilateral or expansion modalities appear to produce trans- bilateral molar full cusp PXB whose parents were verse changes of the maxilla (3, 14–16). willing to participate in the study were included. In recent decades, RME has gained preference as Patients with severe periodontal disease (peri- the treatment of choice for PXB. However, the side odontal probing >4 mm) measured at permanent effects, such as reported pain, relapse of the first upper molars, congenital syndromes, defects, expansion, tipping of the molars, bone loss, gingi- or previous orthodontic treatment were excluded. val recession, and root resorption, have lead some Enrolled subjects were allocated to the two clinicians to prefer SME. SME is commonly thought treatment groups, that is, RME or SME, by a bal- to produce less tissue resistance around the cir- anced block randomization using gender as cum-maxillary structures and, therefore, improve stratifying factor. A single operator (PL) allocated bone formation in the inter-maxillary suture, the patients by means of a custom-made Java reducing the force-related side effects of RME (15). script and was responsible for the allocation Currently, the choice among the two expansion concealment, that is, the allocation was disclosed modalities relies on clinical experience and atti- only when a new patient was enrolled in the trial. tude of the practitioner because of the lack of good The Institutional Review Board and the local scientific evidence (i.e., randomized controlled Ethics Committee approved this study. Informed trials comparing the two treatment modalities). consent was provided by the patientÕs parents. The use of novel imaging techniques in the craniofacial region as well as the availability of Clinical protocol new software for three-dimensional rendering allows for high precision and accuracy when For each patient, the medical and orthodontic measuring the distances between skeletal land- histories, intraoral and extraoral photographs, CT 2 Orthod Craniofac Res 2012  Martina et al. Rapid vs. slow maxillary expansion data, and dental casts were collected prior to per day (0.75 mm activation per day). In the SME placement of the appliance (T0 time). group, the screw was turned twice a week A two-band palatal expander was used. The (0.50 mm activation per week). During the appliance was banded to the maxillary first expansion phase, RME subjects were monitored permanent molars (TBE, Two-Band Expander, once a week, while SME patients were monitored Fig. 1A) only and did not have any extended arm. once every 2 weeks. Each patient was provided The expander jackscrew was localized very close with a custom-made diary and was instructed to to the posterior boundaries of the maxilla and as report the appliance adjustments. The diary was close as possible to the palatal vault to enable checked at each visit by the clinical examiner to the force to be delivered at the same heights as the evaluate patient compliance. centers of resistance of the maxillary first molars In both groups, the jackscrew was activated (Fig. 1B), and as close as possible to the pterygo- until a 2-mm molar transverse overcorrection was maxillary suture, to produce orthopedic effects in achieved. After the active expansion phase, the the posterior area of the maxilla. The appliance screw was locked with light-cure flow composite was placed using a glass ionometer cement (Premise Flowable; Kerr Corporation, Orange, CA, (Multi-Cure Glass ionomer Cement; Unitek, USA). Seven months after appliance positioning Monrovia, CA, USA) following the supplierÕs (T1), the palatal expander was removed, and instructions within 3 weeks from initial records. patients underwent a second CT scan using the In the RME group, the screw was initially turned same parameters and condition of the previous eight times (2.0 mm screw activation) at chair side exam. All clinical procedures were administered two hours after curing. Thereafter, the patientsÕ by a single operator (PM), who was not blinded to parents were trained to turn the screw three times patient allocation. A Computed tomography For this study, a multislice CT scanner was used (Mx 8000 IDT6 Multislice; Philips medical imaging). CT images were obtained with a low- resolution ⁄ low-dose modality (17, 21) using the following parameters: slice thickness 1.3 mm, Index 1.3, Pitch 1, Mass 28, Voltage 80 kV. The field of view was limited between the infraorbital foramina and the inferior edge of the most caudal maxillary teeth for each patient. The voxel size was set at 0.35 · 0.35 · 1.30 mm. Mean scanning B time was 10.6 s. These settings have been shown to reduce the dose absorption for patients while providing good image quality (21–23). To ensure accurate head positioning, patients were scanned in a supine position with the Frankfurt plane perpendicular to the scanning table. The head was supported by means of two bearing pillows. A gutta-percha landmark was glued on the nasal philtrum along the longitudinal CT light beam Fig. 1. (A) Two-band palatal expander. (B) The expander jackscrew was localized very close to the posterior boundaries perpendicular to the bipupillar plane to avoid of the maxilla and as close as possible to the palatal vault so head rotations. that the force could be delivered at least at the same height of the centers of resistance of the first upper molars. Dotted line: Patient data were stored as DICOM (Digital line of action of the force delivered from the screw. Imaging and COmmunications in Medicine) files. Orthod Craniofac Res 2012 3 Martina et al. Rapid vs. slow maxillary expansion Thereafter, they were imported to software axial, and sagittal CT slices (Fig. 3) by a single (Materialise Mimics 8.1, Leuven, Belgium) for operator (RN), blinded to patient allocation, as post-processing. follows: RPyP: Right piriform point. The most lateral and Measurements caudal point of the nasal piriform aperture, at the boundary with the palatal cortex. This To construct a set of reference planes, two skeletal landmark was primarily identified in coronal landmarks were primarily identified in the CT CT slices passing through the anterior edge of scans: the oval point right and left (OVPr ⁄ OVPl), the nasopalatine foramen within the palatal which were defined as the most posterior points cortex. LPyP: Analogue to RPyP, left side. of the right and left oval foramina in the cortex of RPaFoP: Right palatine foramen point. The most the sphenoid, at its middle cranio-caudal height. posterior point of the right greater palatine These points were primarily localized in the ori- foramen in the maxilla within the palatal cor- ginal coronal CT slices. A segment connecting tex. LPaFoP: Analogue to RPaFOPr, left side. OVPr and OVPl was then constructed. The original PtR. Pterygoideous right. The most caudal point axial CT slices were oriented according to the of the apex of the right pterygoid process of the segment OVpR – OVpL using the software. sphenoid. PtL. Pterygoideous left. Analogue to A set of reference planes was then constructed PtR, left side. as follows (Fig. 2): CR: Cuspid right. Mesio-palatal cusp tip of the right Sagittal reference plane (SrPL): The sagittal CT maxillary first molar. CL: Cuspid left. Mesio- slice passing through the middle point of the palatal cusp tip of the left maxillary first molar. segment OVpR-OVpL. AR: Apex right. Apex of the palatal root of the right Axial reference plane (AxrPL): The most caudal maxillary first molar. AL: Apex left. Apex of the point of the clivus sphenoidalis (Basion – Ba) palatal root of the left maxillary first molar. was localized on SrPL. The plane resulting The following distances were measured perpen- from the 45 clockwise rotation of the axial dicular to CorPL and SrPL at T0 and T1 by a single plane passing through OVpR, OVpL, and Ba examiner (RN), who was blinded to patient allo- was considered as the axial reference plane cation (i.e., the names of the patients and the (AXrPL). allocation group were not included in the dataset) Coronal reference plane (COrPL): The plane pass- by means of software (Materialise mimics 8.1, ing through OVpR-OVpL and perpendicular to Leuven, Belgium). AXrPL. Skeletal measurements (Fig. 3A–C): These reference planes were used to correct Anterior maxillary expansion: RPyP-LPyP minimal changes in head positioning. Posterior maxillary expansion: RPaFoP-LPaFoP For each patient, a set of reproducible skeletal Pterygoid expansion: PtR-PtL and dental landmarks were localized in coronal, Dentoalveolar measurements (Fig. 3D): Molar expansion: at molar cusp, CR-CL; at pal- atal root apex, AR-AL Molar tipping: difference between (AR-AL) and (CR-CL) Statistical analysis Fig. 2. Set of reference planes. Sagittal reference plane (SrPL), Paired StudentÕs t-tests were used to test differ- axial reference plane (AxrPL), coronal reference plane (COrPL). ences within groups. T1–T0 between groups 4 Orthod Craniofac Res 2012  Martina et al. Rapid vs. slow maxillary expansion A a factor. Significance level was set at p < 0.05. To calculate the method error and the intra-rater reliability, repeated measurements were collected in eight randomly selected patients (four RME and four SME) on two occasions separated by 1-week interval. The method error (ME) for all the linear dental and skeletal measurements was assessed by means of the DahlbergÕs formula ME = (Sd2 ⁄ 2n)½, where d is the difference between the two measurements and n is the number of recordings. Pearson corre- B lation coefficients were then calculated. Statistical analysis was performed by a single operator (IC), who was blinded to patient allocation (i.e., the allocation was masked to him in the dataset). Results Figure 4 demonstrates patient flow through the clinical trial. CT data of 26 patients were analyzed, 12 (seven C males, five females, mean age ± SD: 10.3 ± 2.5 years) in the SME group and 14 (six males, eight females, mean age ± SD; 9.7 ± 1.5 years) in the RME group. The error range of linear CT mea- surements was 0.5–0.7 mm. Pearson correlation coefficients ranged from 0.97 to 0.99. Table 1 reports descriptive statistics and pair- wise comparisons for T0 and T1 skeletal mea- surements. The groups were similar at baseline for all skeletal and dentoalveolar variables examined (p > 0.05). Maxillary expansion resulted in a sig- D nificant increase in skeletal transverse widths at anterior, posterior, and pterygoid locations in both RME and SME groups. No side effects were experienced during the clinical phase, with the exception of a more painful response in RME patients. No appliance removal was required. No Fig. 3. Localization of skeletal landmarks on both coronal statistically significant differences between and axial planes. (A) Assessment of the anterior expansion; (B) assessment of posterior expansion; (C) assessment of groups were found, with exception of the expan- pterygoid expansion; (D) assessment of molar expansion and sion measure at pterygoid processes, which was tipping greater in the RME group (SME = 0.6 ± 0.6 mm, RME = 1.2 ± 0.9 mm, p = 0.04). differences were evaluated with analysis of vari- Table 2 reports descriptive statistics and pair- ance. T1–T0 differences of each measurement wise comparison for T0 and T1 dental mea- were used as independent variables, and the surements. The appliance produced molar allocation group (RME vs. SME) was considered as expansion at both cusp and apex levels in both Orthod Craniofac Res 2012 5 Martina et al. Rapid vs. slow maxillary expansion Fig. 4. Diagram of patient flow through the trial. groups. In the SME group, molar tipping was modalities was possible using skeletal landmarks not statistically significant (0.3 ± 0.9 mm), while determined in three dimensions with much in the RME group, there was negligible molar improved reproducibility and accuracy in com- tipping (1.0 ± 1.2 mm, p < 0.005). The expansion parison with posteroanterior radiographs (24), measured at molar apices was significantly commonly used in previous research. lower in the RME group than in SME group A two-band palatal expander was applied to (p = 0.02). perform the expansion. This appliance has been shown to be as effective as a four-band expander in increasing the transverse widths of maxillae in Discussion the long term (25, 26) and produces less patient discomfort with easier clinical management. This study aimed to compare the skeletal and In this study, patients younger than 13 years dento-alveolar effects of two palatal expansion were recruited, because the growth activity of the procedures, RME and SME. To improve the pre- palatal suture has been reported to reduce around cision of landmark identification and reduce the 14 years of age (27). radiation exposure of the patients a low-dose CT All patients were subjected to CT imaging protocol was used for research purposes (21). before expansion and 7 months after initial acti- Thus, a comparison between the two expansion vation of the appliances. This period was chosen to 6 Orthod Craniofac Res 2012  Martina et al. Rapid vs. slow maxillary expansion Table 1. Descriptive statistics and RME (n = 14) vs. SME (n = 12) skeletal transverse changes pairwise comparisons for skeletal transverse changes measured in both Skeletal T0 T1 95% groups transverse (mean ± (mean ± Confidence measurements Group SD) SD) T1–T0 SD interval Anterior SME 4.7 ± 1.9 6.6 ± 2.1 1.9 1.3** 1.0–2.1 expansion (mm) RME 5.8 ± 3.8 8.2 ± 4.4 2.5 1.5** 1.6–3.3 Total 2.2 1.4 Posterior SME 26.3 ± 2.2 28.2 ± 2.6 1.9 1.0** 1.3–2.5 expansion (mm) RME 26.2 ± 2.3 28.6 ± 2.6 2.4 0.9** 1.8–2.9 Total 2.2 0.9 Pterygoid SME 28.0 ± 2.1 28.6 ± 2.1 0.6 0.6* 0.2–1.0 expansion (mm) RME 28.0 ± 3.7 29.2 ± 4.2 1.2 0.9** 0.7–1.7 Total 0.9 0.8 Significant T1–T0 within-group differences are reported with asterisks (Significance level: *p < 0.05, **p < 0.001). Significant differences between groups (slow maxillary expansion (SME) vs. rapid max- illary expansion (RME)). Values are in mm. Table 2. Descriptive statistics and Dental T0 T1 T1–T0 95% pairwise comparisons for dental trans- transverse (mean ± (mean ± mean Confidence verse changes measured in both measurements Group SD) SD) changes SD interval groups Cr-Cl (mm) SME 37.2 ± 3.4 43.6 ± 4.5 6.3 2.1*** 5.0–7.7 RME 37.3 ± 1.8 43.0 ± 2.4 5.7 1.6*** 4.8–6.7 Total 6.0 1.8 Ar-Al (mm) SME 28.5 ± 3.0 34.5 ± 3.5 6.0 1.7*** 4.9–7.0 RME 28.6 ± 2.3 33.4 ± 2.6 4.7 1.2*** 4.1–5.4 Total 5.3 1.5 Molar SME 8.8 ± 3.9 9.1 ± 4.1 0.3 0.9NS 0.2–0.9 tipping (mm) RME 8.6 ± 2.4 9.6 ± 2.6 1.0 1.2* 0.3–1.7 Total 0.7 1.1 Significant T1–T0 within-group differences are reported with asterisks (Significance level: *p < 0.05, **p < 0.005, ***p < 0.001, NS=not statistically significant). Values are in mm. SME, slow maxillary expansion; RME, rapid maxillary expansion. obtain proper remineralization of the mid-palatal different landmarks do not allow for direct com- suture and to reduce the risk of relapse (28, 29). parison of data between studies. In both experimental groups, posterior crossbite In a meta-analysis, Lagravere et al. examined was successfully treated, and a significant increase clinical trials using 2D cephalometric analysis to in the maxillary transverse widths of about 2.2 mm evaluate the skeletal changes produced by RME was obtained. The amount of palatal expansion did (16). A pooled increase in the intermaxillary width not differ significantly between the two investi- of 1.88 mm was reported. Some of the studies gated groups and was similar to previous findings analyzed (8, 25, 31–34) included subjects older (15, 20, 30). Nevertheless, the different imaging than 14 years, that is, with reduced sutural growth methodologies used in previously published stud- activity (27). This might affect the amount of ies (lateral radiograph and CT) as well as the use of expansion reported in the meta-analysis (35). Orthod Craniofac Res 2012 7 Martina et al. Rapid vs. slow maxillary expansion An increase in transverse widths ranging from potentially be reduced using bonded instead of 1.6 (36) up to 2.6 mm (20) was found in studies banded appliances (38, 39) because of the higher using CT. Even among these studies, the use of stiffness of bonded appliances. different landmarks and the variation of patient Many authors report external root resorption in age do not allow meaningful comparison. In the individuals undergoing RME (40–42) evaluated by current study, the average increase in skeletal scanning electron and light microscopy (41) and transverse widths between anterior and posterior cone beam CT surveys (42). This resorption is likely locations was very similar and amounted to a consequence of the great amount of cumulative approximately 2.2 mm. This suggests that forces produced by RME (28). Furthermore, higher the expansion occurred homogenously along the pain rates have been reported in subjects who mid-palatal suture and contrasts with the undergo maxillary expansion with two turns per ÔV-shapedÕ maxillary expansion occurring with day as compared to one turn per day (43). Unfor- four bands or acrylic expanders (37). A possible tunately, root resorption and pain were not quan- explanation is the more posterior TBE line of titatively assessed in the present study, but it was action as compared with other appliances. This generally observed that RME patients reported effect was more accentuated in the RME group, in higher levels of pain and discomfort than SME which a statistically significant higher transverse patients, especially during the initial activation. expansion was measured at pterygoid locations. In conclusion, this study demonstrated that Both expansion modalities produced increases SME is as effective as RME in determining skeletal in the molar transverse widths ranging from 4.7 to transverse expansion of the maxilla in patients 6.3 mm, with no significant difference between with a posterior crossbite. Slow maxillary expan- the groups. These results are in agreement with sion may be preferred to rapid maxillary expan- data concerning RME by Lagravere et al., who sion because of the reduced pain and discomfort. reported an average transverse increase of 6.7 mm The long-term stability of the palatal expansion at the crown level and 4.5 mm between molar achieved needs to be evaluated. crowns and molar apices (16). On the other hand, data from CT surveys reveal that the expansion measured at molar crowns ranged from 3.6 mm Clinical relevance (36) to 8.9 mm (20) and that transverse widths The choice between rapid versus slow maxillary measured between molar apices increased from expansion still relies on clinical experience and 2.0 mm (36) to 6.8 mm (20). attitude because of the lack of good scientific In both groups, slight molar tipping was mea- evidence (i.e. randomized controlled trials com- sured. The RME group showed a small (about paring the two treatment modalities). This study 1 mm) but statistically significant molar tipping, aimed to compare the transverse effects produced which is in agreement with previous findings (38). by the two maxillary expansion modalities to al- In contrast, the tipping determined by SME was low orthodontists to make evidence-based treat- not statistically significant. 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