Dimensional changes of dental arches produced by fixed and removable palatal cribs: A prospective, randomized, controlled study
Objective: To evaluate the dimensional changes of dental arches on digital models of open bite treatment with fixed and removable palatal cribs.
Materials and Methods: The sample comprised 41 patients of both sexes who were white, aged 7–10 years, and who had mixed dentition, Angle Class I molar relationship, and a negative overbite of at least 1 mm. The sample was randomly divided into two groups: G1, fixed palatal crib; and G2, removable palatal crib. Cast models, obtained initially (T1) and after 1 year of treatment (T2), were scanned by a three-dimensional (3D) scanner, 3Shape R700, producing a 3D image. Measurements were performed by a calibrated examiner using OrthoAnalyzer™ 3D software.
Results: At T2–T1, differences were observed between the groups regarding vertical dentoalveolar development and overjet. There was more mandibular incisor extrusion for G1 (−1.66 mm) than for G2 (−0.54 mm). An overjet increase was observed in G1 (0.56 mm), in contrast to a reduction in G2 (−0.40 mm). There was a similar overbite increase for both groups (3.51 mm for fixed palatal crib and 3.88 mm for removable palatal crib).
Conclusions: Both the treatment protocols are similarly effective for anterior open bite correction, providing an overbite increase with dentoalveolar arch changes, especially in the anterior region.ABSTRACT
INTRODUCTION
Anterior open bite (AOB) may be defined as the absence of overbite between the incisal edges of the upper and lower incisors when the posterior teeth are in occlusion.1 Its prevalence varies from 11.2% to 18.5%,2 and it occurs in approximately 17% of individuals during mixed dentition. Several factors are involved in AOB etiology, and in most cases, it results from deleterious habits, such as thumb and pacifier sucking, mouth breathing, and tongue or lip interposition.3 A vertical facial growth pattern has also been implicated.4
Although many therapeutic interventions for American Board of Orthodontics have been presented in the literature,5,6 there seem to be no data describing the three-dimensional (3D) changes in maxilla and mandible caused by the application of these methods during the mixed dentition stage. It is important to intercept deleterious oral habits, and fixed and removable palatal cribs (RPCs) may be used as recall devices in the mixed dentition stage.4–6
Several studies4,7–13 have been performed to assess the effectiveness of both fixed palatal crib (FPC) and RPC, reporting their posttreatment effects through measurements performed on cephalograms or manually on cast models. Villa and Cisneros7 observed, in cast models, the dental changes in patients with digital sucking managed with a palatal crib. However, the limitations of these manual measurements preclude a detailed and accurate analysis. Digital models may prove to be superior to cephalograms and cast models because of improved measurements obtained through tridimensional evaluation.14
Therefore, this prospective, randomized, controlled study aimed to evaluate the dimensional changes in dental arches with digital models, before and after 1 year of AOB treatment with FPCs and RPCs.
MATERIALS AND METHODS
The sample size was calculated based on an alpha of 5% and a power of 80%. This would allow detection of a mean difference in overbite of 2.1 mm, with a standard deviation of 1 mm between the groups.15 Therefore, at least 16 patients were required in each group. Study approval from the ethics committee at the University of North Paraná was obtained.
The initial sample size comprised 50 patients, and 41 completed the study. Nine patients dropped out during the study: four declined to participate, and five did not show up for follow-up appointments (Figure 1).
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
Patients were enrolled in the study if they met the following inclusion criteria: children between 7 and 10 years of age with Angle Class I malocclusions, AOB equal to or greater than 1 mm, and erupted maxillary and mandibular permanent central incisors. All patients presented nonnutritive sucking habits and/or tongue thrusting. The size of the adenoids and tonsils and the tongue volume were not evaluated for their possible etiological role in airway obstruction. Exclusion criteria included craniofacial anomalies; congenitally missing permanent teeth, with the exception of third molars; severe crowding; maxillary constriction or posterior crossbites; and extracted permanent teeth.
Patients were randomly assigned to two groups. G1 was composed of 23 patients treated with FPC, with initial mean AOB of −2.95 (standard deviation [SD] = 1.60 mm) and mean age of 8.4 years (SD = 0.8). Seventeen of the children were girls (8.39 years, SD 0.83) and six were boys (8.51 years, SD 1.06). They were treated for a mean period of 12 months (minimum 11.76 months, maximum 13.2 months). G2 was composed of 18 individuals treated with RPC, with initial mean AOB of −3.00 (SD 1.43 mm) and mean age of 8.4 years (SD 0.7). Eight of the children were girls (8.26 years, SD 0.91), and 10 were boys (8.56 years, SD 0.64). They were also treated for a mean period of 12 months (minimum 11.76 months, maximum 14.52 months). A computer-generated randomization list was created using Excel (2007, Microsoft Windows).
Blinding was performed during allocation of the groups and during the dental arch analysis; however, there was no blinding as to the treatment modality, because it was apparent which appliance each patient had received. The same two clinicians treated all of the patients, and the patients were evaluated monthly to monitor progress of the treatment. Instructions were provided to assist the patients in discontinuing the sucking habit.
G1 was treated using an FPC, which included bands on the first permanent molars. The bands were transferred to plaster models to allow welding of a palatal stainless-steel arch measuring 0.9 mm, and all were constructed by the same professional. Palatal bars constructed of stainless steel and measuring 0.7 mm were added, extending the length of the cervical lingual aspect of the lower incisors (Figure 2).
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
G2 was treated with a removable appliance composed of a palatal crib, Adams' clasps on the maxillary permanent first molars, a labial archwire, and acrylic coverage on the palatal region, which contacted the lingual aspect of all teeth. Patients were instructed to wear the RPC full-time except during meals and oral hygiene. Positive-negative reinforcement was provided every month (Figure 3).
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
Dental Cast Analysis
To evaluate dimensional changes in the dental arches of the 41 patients, initial and final cast models were compared. These were scanned by a 3D scanner (3Shape R700, 3Shape A/S, Copenhagen, Denmark) designed for high-precision scanning, producing a 3D image on which measurements were performed. After scanning, the initial models (T1) and the models created after 1 year of treatment (T2) were evaluated by a previously calibrated examiner using OrthoAnalyzer™ 3D software, 2013 version (3Shape A/S). The following variables were measured at T1 and T2: upper and lower dental arch perimeter16,18 and length19,20 (Figure 4), inclination of the upper incisors,7,21 upper and lower vertical dentoalveolar development22 (Figure 5), height of the upper incisors,19 overjet,14,20,23 overbite2,14,20,23 (Figure 6), and transverse distances of the inter–first permanent molars.18,24 Transverse distances between the first permanent molars were calculated from three separate linear measurements, obtained by joining two points on the upper and lower first permanent molars: right and left mesiobuccal cusp points, right and left distobuccal cusp points, and lingual cervicals or right and left palatine.18,24
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
Citation: The Angle Orthodontist 87, 2; 10.2319/060116-438.1
Cephalometric Analysis
Cephalometric data were collected from lateral cephalograms obtained prior to treatment (T1) to evaluate the groups. The customized cephalometric analysis included nine variables for each tracing. Dolphin (11.0 Imaging Program, Chatsworth, Calif) was used for data collection and generation. A magnification factor of 9.5% was applied.
Error of Method
All measurements were repeated after 30 days by one operator to assess error in methodology. Intraclass correlation and Bland-Altman tests were used to evaluate the intraobserver reliability.
Statistical Analysis
The preliminary data assessment revealed a normal distribution (Kolmogorov-Smirnov test) for all of the variables. Intragroup comparisons were performed by paired t-tests, and comparisons between groups were performed by an independent t-test using Statistica software 7.0 (Statistica for Windows; Statsoft, Tulsa, Okla), with a confidence interval of 95%.
RESULTS
None of the 26 variables analyzed presented a statistically significant systematic error. The error for linear measurements ranged from 0.06 mm for the right upper incisor to 0.28 mm for LMCP 46-36. For the angular measurement, the error was 0.38° (UI inclination). There were no significant differences between G1 and G2 with respect to age, treatment/follow-up period, sex distribution, and severity of AOB. There were no significant intergroup differences in relation to cephalometric variables SNA, Co-A, SNB, Co-Gn, ANB, SN.GoGn, AFAI, H.NB, and FMA (Table 1) at baseline (P > .05).
The G1 displayed a reduction in lower arch perimeter, an increase in upper right and left central incisor height, and a significant change in lower vertical development. Overbite correction was evident, reducing AOB from −2.95 mm to +0.57 mm, as well as a significant increase in the transverse distances between the upper first permanent molars (Table 2).
The G2 displayed a reduction in the upper and lower arch perimeter and in length. Extrusion with upper vertical development was noted, as was an increase in the height of the upper right and left central incisors. An overbite correction of 3.84 mm was evident. There was a significant increase in the transverse distance between the upper first permanent molars (Table 3).
Comparing the changes (T2–T1) between the groups, there was a statistically significant reduction in the lower vertical development for G1 and a decrease in overjet for G2 (Table 4).
DISCUSSION
Although there are several reports documenting the treatment effects of palatal cribs,5 the literature lacks prospective studies comparing FPC and RPC used alone with no additional appliances. Most of the reports5,6 measured AOB on lateral cephalograms; in this method, difficulties might be encountered when marking the points as a result of overlap of the incisors. Thus, the use of 3D digital models for evaluation of dental changes might be considered a superior method.
The results of this study show that both groups resulted in a similar decrease in AOB, with no statistically significant difference between the groups. There was a mean decrease in AOB of 3.52 mm for G1 (Table 2) and a decrease of 3.84 mm for G2 (Table 3). These values are similar to the ones found in the literature.7,13 In a study25 that questioned the effectiveness of crib therapy in patients with AOB, the authors treated eight patients with a mean age of 12 years for a period of only 6 months, which is not the ideal duration for AOB treatment. According to the literature, crib therapy should be performed in the early mixed dentition stage25–27; this may have accounted for the poor outcomes in that study.25
If one considers end-to-end incisor relationship as an indicator of treatment success, AOB was successfully corrected in 17 individuals with FPC (74%) and 14 (78%) with RPC. Recently, studies comparing the AOB treatment effects of FPC28 and RPC29 with those of other devices concluded that both therapies provided an increase in overbite. It was observed that FPC was effective in AOB treatment in 100% of patients,28 and RPC was effective in 97.5% of the patients.29 Overbite correction likely failed in some of the patients in this study as a result of persistent sucking habits or interposition of the tongue. This outcome might be the consequence of the short-term follow-up, which might not have afforded a sufficient length of time to detect full correction of AOB in some patients. This might also have resulted from the different measurement methods used in this study (cast models).
In addition to reducing AOB, approximately 1-mm extrusions of the upper incisors and a significant counterclockwise vertical development of the lower dentoalveolar processes (Table 2) were found for the FPC group. Likewise, the RPC group demonstrated an upper incisor extrusion of approximately 1 mm, in addition to a clockwise development of the upper dentoalveolar processes (Table 3). These values are similar to those of Cozza et al.,13 who observed extrusion of the upper incisors in cephalograms of about 1.4 mm, and they are also in agreement with other reports from the literature5 regarding the use of palatal cribs.
There was a significant difference between the groups at T2–T1, showing a higher counterclockwise development of the lower dentoalveolar processes for the FPC group (−1.66 mm) compared to the RPC group (−0.54 mm) (Table 4). Although studies by Torres et al.10 and Giuntini et al.8 showed no statistically significant difference between the groups at T2–T1, Pedrin et al.9 reported a difference in the lower anterior counterclockwise development of 1.08 mm, and Cozza et al.13 reported a difference of 1.0 mm. It should be mentioned that some vertical movement of the incisors might be expected as a result of normal growth. As a result of the lack of a control group, we cannot differentiate how much incisor extrusion occurred as a result of normal growth and how much as a consequence of the appliances.
Significant changes were also observed in arch perimeter, with a decrease of 0.92 mm for the upper arch in the RPC group and a reduction of 1.6 mm and 1.41 mm in lower arch perimeter for FPC and RPC, respectively (Tables 2 and 3). Our results are similar to those of Villa and Cisneros,7 who verified an average reduction in maxillary arch perimeter of 2.6 mm and a reduction in mandibular arch perimeter of 1.9 mm.
A significant decrease in maxillary and mandibular arch length was observed. The FPC group displayed a reduction of 0.91 mm in the lower arch, and the RPC group displayed a reduction of 1.34 mm and 0.88 mm in the upper and lower arches, respectively (Tables 2 and 3). These results contradict those of Larsson,30 who showed no significant changes in arch length, but are similar to those of Villa and Cisneros7 (reduction of 1.4 mm in the upper arch and of 1.2 mm in the lower arch).
An increase in transverse distances was observed for all the variables measured. This result may be explained by the reeducation of tongue posture with the cribs and the expected normal transverse arch development. There was a statistically significant difference in the upper arch for the G1 (0.51 mm and 0.45 mm for distances between the mesiobuccal and distobuccal cusps, respectively) and for the G2 in the upper arch (0.53 mm, 0.47 mm, and 0.48 mm for distances between the mesiobuccal cusps, distobuccal cusps, and palatal cervical points, respectively) and the lower arch (0.35 mm for distances between the mesiobuccal cusps) (Tables 2 and 3). When comparing the groups at T2–T1 (Table 4) there were no significant changes in transverse distances, upper incisor height, or their inclinations.
Finally, a lack of change in overjet at T1 and T2 was noted between the groups, which was in agreement with the findings of other investigators.7,13,30 However, comparison of differences between groups (T2–T1) reveals a statistically significant difference in overjet, by a reduction for the RPC (−0.40 mm) and an increase for the FPC (0.56 mm). Torres et al.4 obtained similar results when comparing overjet between RPC (−0.75 mm) and FPC (0.40 mm). The differences found in overjet between the two groups may be related to a modification in the perioral and lingual muscle balance and appliance design, as the RPC had a labial arch over the upper incisors that could contact these teeth.
In summary, our results reveal that AOB was corrected in 74% of patients with FPC and in 78% of the patients with RPC. Clinically, either appliance can be a good treatment option when treating AOB in patients with mixed dentition. The limitation of this study was that treatment was confined to a 1-year period. Additional studies are recommended to evaluate the long-term stability.
CONCLUSIONS
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Both treatment protocols were similarly effective for AOB correction, providing a reduction of 3.52 mm for the FPC and 3.84 mm for the RPC.
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There was more mandibular incisor extrusion for G1 compared to G2.
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An overjet increase was observed in G1 (0.56 mm), in contrast to an overjet reduction in G2 (−0.40 mm).
CONSORT flow diagram.
Model of FPC.
Model of RPC.
Upper dental arch length. Linear measurement between the contact points of the central incisors, or the midpoint between them on the gingival margin, and an intersection point perpendicular to a transverse line.
Upper dentoalveolar vertical development. Linear measurement between the contact points of the central incisors, or the midpoint between them, and an intersection point perpendicular to the horizontal plane.
Overbite and overjet.
Contributor Notes