Abstract
Objectives
The aim of this study was to evaluate the cephalometric outcome of bone-
anchored maxillary protraction (BAMP) in individuals with unilateral complete cleft lip and palate (UCLP).
Material and methods
The experimental group (EG) comprised 23 individuals (17 males and 6 females) with UCLP and a mean age of 11.7 years. At least 6 months after secondary alveolar bone grafting, Bollard miniplates were installed in the posterior region of the maxilla and in the anterior region of the mandible. Class III elastics were recommended to be worn for 24 hours/day for a mean time of 18 months. Cone beam computed tomography (CBCT) was obtained before (T1) and after treatment (T2). The control group (CG) consisted of 23 individuals with UCLP matched by initial age and gender with the EG and without any orthopaedic or surgical intervention performed between T1 and T2. The interval between T1 and T2 observations was 18 months for both groups. Twenty-one cephalometric variables were analysed. Intra- and intergroup comparisons were performed using paired and independent t-tests, respectively (P < 0.05).
Results
BAMP caused a greater maxillary protrusion (SNA) and a greater decrease of Class III maxillomandibular discrepancy (ANB and Wits appraisal) compared with the CG. BAMP also caused a counterclockwise rotation of the occlusal plane (Occ Plane to FH) and an improvement in the molar relationship compared with controls.
Conclusions
BAMP therapy demonstrated a significant orthopaedic maxillary protraction and an improvement in the Class III skeletal pattern in UCLP.
Introduction
One of the most relevant challenges in the dental rehabilitation of complete cleft lip and palate (CLP) is the maxillary growth deficiency (1). Severe maxillary retrusion has a relevant facial aesthetical impact in school children and adolescents with CLP (2). Maxillary deficiency causes severe malocclusions with anterior crossbites besides impairing the pharyngeal airflow and speech (3,4). In our century, Le Fort I surgery is still the ideal rehabilitation procedure for patients with moderate-to-severe maxillary deficiency. However, a long waiting time until the end of facial growth might cause bullying, strain, and depression during the delicate phase of adolescence (5–7).
What the craniofacial team could do to solve the aforementioned problems? Facemask therapy leads to only slight maxillary protraction in patients with unilateral complete cleft lip and palate (UCLP) (8,9). In patients with Goslon rating 4 and 5, greater amounts of maxillary protrusion are required (10). Another limitation of facemask therapy in patients with UCLP is the long-term instability (11). Strain from scar tissues in the lip and palate is the major cause for maxillary growth deficiency and is not eliminated by the orthopaedic treatment, impairing the maxillomandibular sagittal relationship until the end of growth.
Bone-anchored maxillary protraction (BAMP) has been described by De Clerck et al. (12,13). Firstly, three cases of female patients aging 10—11 years treated with full-time Class III elastics anchored on four Bollard miniplates presented an increasing of the SNA angle of 4.5° to 7° (12). Later, a clinical study of 21 consecutive non-cleft Class III cases at a mean age of 11.1 years showed a 4-mm maxillary protrusion and a 6-mm change in the intermaxillary relationship compared with a control group (CG) (13). Cone beam computed tomography (CBCT) three-dimensional (3D) analysis of 25 consecutive cases at the same age treated with BAMP demonstrated the zygomas following the maxillary protrusion (14). In addition, a slight posterior displacement of posterior ramus, condyles, and chin was observed associated with the posterior remodelling of the glenoid fossae (15). Compared with the facemask therapy, BAMP was shown to produce a greater maxillary protraction and the absence of clockwise rotation of the mandible in non-cleft individuals (16).
Recent studies demonstrated that BAMP produced a significant maxillary protraction in patients with UCLP (17,18,19). In comparison with non-cleft individuals, BAMP produced similar maxillary and mandibular changes in UCLP (18,20). Even though a high level of individual variation was observed, the maxillomandibular discrepancy was minimized after maxillary protraction in UCLP (18). Although previous 3D studies have described overall growth changes, remodelling processes in the glenoid fossa and possible rotations of the greater and lesser segments in UCLP, 2D analysis is important for providing extra information that 3D superimposition alone have not supplied. The exact numeric data from rotations of the maxilla and palatal plane, rotations of the mandible, dentoalveolar compensations and changes in the gonial angle should be evaluated. In addition, no previous studies compared individuals with UCLP-treated and non-treated with BAMP at the same age range. Therefore, the objective of this study was to evaluate the cephalometric outcomes of BAMP in patients with UCLP. The null hypothesis was that there is no difference between BAMP-treated and non-treated individuals with UCLP.
Material and methods
Institutional research ethics committee of the Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo was obtained and consent forms were signed. The sample size calculation was based on preliminary statistics including the first 10 patients from the experimental group. Considering a standard deviation of 1.9° of SNA angle in a previous study with BAMP (13), and a minimal intergroup difference of 1.5° to be detected, a sample of 26 patients was required to provide statistical power of 80% with an alpha of 0.05.
The BAMP Group consisted of 27 individuals (19 males and 8 females) with unilateral complete cleft lip and palate from the for Rehabilitation of Craniofacial Anomalies, University of São Paulo. The inclusion criteria were the presence of moderate-to-severe maxillary deficiency (Goslon Index 3, 4, or 5); minimal age of 10 years; maximum age of 13 years; late mixed dentition or permanent dentition; mandibular permanent canines already erupted; secondary alveolar bone graft performed at least 6 months before the study onset; the absence of associated syndromes; and good oral hygiene. Wits appraisal among BAMP subjects ranged from –2 to –11.5 mm. Two miniplates (Bollard type, Tita-Link, Brussels, Belgium) were placed in the maxilla at the infrazygomatic crest bilateraly. In the mandible, two other miniplates were placed on both sides between the roots of the permanent canine and lateral incisor. Three weeks after surgery, full-time Class III intermaxillary elastics (G&H Orthodontics, Franklin, Indianapolis, USA) connecting the maxillary and mandibular miniplates were inserted (Figure 1). The traction was started with 75 g on each side, increased to 150 g in the second month, and 250 g in the third month further maintained until the end of active therapy. The elastics were changed twice a day, in the morning and in the evening. Bite plates with finger springs lingual to the maxillary incisors were used to open the bite and to ‘jump’ the bite when reaching an edge-to-edge incisor relationship. CBCT exams with 13 cm-field of view and 0.4-mm voxel size were obtained before (T1) and after treatment (T2) with a mean interval of 18 months. CBCT use followed the European Guidelines and the as low as reasonably achievable principles (21). Pre-treatment CBCT was used for planning the surgical procedure of miniplates installation. Post-treatment CBCT was performed to evaluate the temporomandibular joint soundness after Class III elastics and to plan the comprehensive orthodontic treatment. Pre- and post-treatment CBCT were previously used to analyse 3D changes of maxilla and mandible from T1 to T2 (18,20). For the current study, reformatted lateral cephalometric images were obtained using Dolphin software for comparisons with conventional cephalograms (22). During follow-up, two patients were lost because of treatment interruption; one patient was excluded due to maxillary miniplate instability; and one patient due to motion artifacts during the CBCT exam. The final sample comprised 23 patients (17 males and 6 females) with a mean age of 11.7 years.
Figure 1.
Bollard miniplates and Class III elastics used in the bone-anchored maxillary protraction group.
The control group (CG) consisted of 23 patients with UCLP paired by gender and initial age with the final BAMP group. The inclusion criterion was the presence of moderate-to-severe maxillary deficiency (Goslon Index 3, 4, or 5) and the presence of two cephalometric radiographs with a 12- to 24-month interval in the hospital database (mean interval of 18.74 months). The exclusion criteria were history of orthopaedic/orthodontic intervention between T1 and T2 or bad quality cephalometric images. Both groups had a similar primary surgery protocol including lip repair at 6 months of age with Millard technique and one-stage palate repair at 12 months with the Von Langenbeck technique. Previously to T1, patients had rapid maxillary expansion in the mixed dentition previously to secondary alveolar bone graft procedure. The final sample comprised 23 patients (17 males and 6 females) with a mean age of 11.5 years. The lateral cephalograms were digitized (MICROTEK Scan Maker, Hsinchu, Taiwan; model i800).
Cephalometric images from both groups were traced and analysed with Dolphin Imaging 11.5 software (Patterson Dental Supply, Inc, Chatsworth, California, USA). CBCT-derived cephalograms were generated using the full-face width with no magnification. The software corrected the 6% image magnification factor of the CG. A customized cephalometric analysis generated 21 variables for each tracing (Figure 2).
Figure 2.
Cephalometric variables: (A) 1, SNA; 2, SNB; 3, ANB; 4, Wits appraisal; 5, Co-A; 6, Co–Gn; 7, Co–Go; 8, NAP; 9, Occlusal Plane to Francfurt Horizontal (Occ Plane to FH); 10, mandibular plane to Francfurt Horizontal (MP–FH); 11, gonial angle (Ar–Go–Gn); 12, face height (N–Me); 13, nasolabial angle; (B) 14, maxillary incisor inclination (U1–Palatal Plane); 15, incisor to mandibular plane angle; 16, overbite; 17, overjet; 18, molar relation; 19, soft tissue convexity (G’–Sn–Po’); 20, subnasal prominence (G’–Sn) and 21, soft pogonium prominence (G’–Pg’).
Statistical analyses
Fifty percent sample was retraced by one examiner with a 30-day interval. The method error was calculated comparing the first and second measurements using Dahlberg formula and paired t-tests (P < 0.05).
Normal distribution was verified using Kolmogorov–Smirnov tests. All variables showed normal distribution. Interphase changes in both groups were evaluated using paired t-tests. Intergroup comparisons were performed using independent t-tests. The significance level regarded was 5%. Holm–Bonferroni post hoc correction for multiple tests was applied.
Results
The random error of cephalometric variables ranged from 0.29 (ANB) to 5.93 (nasolabial angle). Of 21 variables, 4 variables (NAP, Co–Gn, Co–Go, and N–Me) showed significant systematic errors ranging from 0.45 to 1.35.
The intergroup comparisons of starting forms demonstrated that the experimental group had a more severe maxillary deficiency and a greater Class III maxillomandibular discrepancy (Table 1).
Table 1.
Comparison of the starting forms (t-tests). BAMP, bone-anchored maxillary protraction; SD, standard deviation
| BAMP group (n = 23) | Control group (n = 23) | ||||
|---|---|---|---|---|---|
| Variables | Mean | SD | Mean | SD | P |
| Sagittal skeletal | |||||
| SNA | 73.68 | 3.35 | 78.04 | 4.95 | 0.003* |
| SNB | 77.57 | 4.30 | 77.89 | 4.62 | 0.829 |
| ANB | –3.88 | 2.83 | 0.15 | 3.86 | 0.001* |
| WITS | –7.53 | 3.06 | –2.65 | 4.06 | <0.001* |
| Co-A | 80.41 | 4.35 | 74.60 | 4.09 | <0.001* |
| Co–Gn | 116.52 | 5.18 | 102.37 | 6.94 | <0.001* |
| Co–Go | 57.29 | 3.60 | 49.02 | 3.86 | <0.001* |
| NA–AP | –9.54 | 6.24 | –0.83 | 9.14 | 0.001* |
| Vertical skeletal | |||||
| Occ Plane to FH | 7.56 | 3.56 | 8.38 | 4.74 | 0.553 |
| FMA (MP-FH) | 29.71 | 4.67 | 31.27 | 5.55 | 0.359 |
| Ar–Go–Gn | 130.73 | 4.62 | 129.53 | 5.21 | 0.455 |
| N–Me | 121.75 | 6.59 | 107.50 | 7.77 | 0.001* |
| Teeth | |||||
| U1–palatal plane | 108.38 | 7.40 | 102.40 | 5.97 | 0.008* |
| IMPA | 81.40 | 6.03 | 83.59 | 5.76 | 0.256 |
| Overbite | 1.76 | 3.50 | 1.06 | 2.44 | 0.466 |
| Overjet | –4.98 | 2.73 | –1.70 | 3.78 | 0.004* |
| Molar relation | –3.88 | 2.10 | –1.98 | 1.98 | 0.006* |
| Soft tissue | |||||
| Nasolabial angle | 102.46 | 14.42 | 89.08 | 19.91 | 0.024* |
| G’–Sn–Po’ | 1.40 | 6.52 | 1.47 | 7.93 | 0.977 |
| G’–Sn | –2.14 | 3.65 | –2.03 | 4.24 | 0.927 |
| G’–Pg’ | –5.02 | 9.63 | –5.02 | 8.49 | 0.999 |
*Statistically significant after Holm–Bonferroni correction for multiple comparisons.
At T2, in the BAMP group (Table 2), the maxilla was significantly protruded (SNA, Co-A, and G’-Sn’) to correct the maxillary deficiency, with a significant increase of the Wits appraisal. The gonial angle was slightly closed. The overjet and molar relationship was improved.
Table 2.
Interphase changes in the bone-anchored maxillary protraction group (paired t-tests). SD, standard deviation
| Pre-treatment | Post-treatment | ||||||
|---|---|---|---|---|---|---|---|
| Variables | Mean | SD | Mean | SD | Diff. | SD | P |
| Sagittal skeletal | |||||||
| SNA | 73.68 | 3.35 | 75.36 | 3.30 | 1.68 | 1.64 | <0.001* |
| SNB | 77.57 | 4.30 | 77.54 | 4.70 | –0.03 | 1.79 | 0.938 |
| ANB | –3.88 | 2.83 | –2.19 | 3.62 | 1.69 | 2.60 | 0.014 |
| WITS | –7.53 | 3.06 | –5.04 | 4.64 | 2.49 | 3.22 | 0.004* |
| Co-A | 80.41 | 4.35 | 83.77 | 4.77 | 3.37 | 2.21 | <0.001* |
| Co–Gn | 116.52 | 5.18 | 118.44 | 5.46 | 1.92 | 3.08 | 0.017 |
| Co–Go | 57.29 | 3.60 | 58.31 | 3.81 | 1.01 | 3.36 | 0.219 |
| NA-Apo | –9.54 | 6.24 | –6.26 | 7.68 | 3.29 | 5.69 | 0.025 |
| Vertical skeletal | |||||||
| Occ Plane to FH | 7.56 | 3.56 | 5.53 | 4.26 | –2.02 | 3.12 | 0.014 |
| FMA (MP–FH) | 29.71 | 4.67 | 28.23 | 4.13 | –1.48 | 2.81 | 0.040 |
| Ar–Go–Gn | 130.73 | 4.62 | 128.66 | 5.25 | –2.08 | 2.26 | 0.001* |
| N–Me | 121.75 | 6.59 | 124.31 | 7.46 | 2.56 | 3.77 | 0.010 |
| Teeth | |||||||
| U1–palatal plane | 108.38 | 7.40 | 109.43 | 8.89 | 1.05 | 3.72 | 0.248 |
| IMPA | 81.40 | 6.03 | 82.79 | 7.51 | 1.39 | 3.95 | 0.154 |
| Overbite | 1.76 | 3.50 | 0.22 | 1.78 | –1.54 | 3.77 | 0.102 |
| Overjet | –4.98 | 2.73 | –2.63 | 4.19 | 2.35 | 3.07 | 0.005* |
| Molar relation | –3.88 | 2.10 | –0.53 | 2.77 | 3.34 | 2.12 | <0.001* |
| Soft tissue | |||||||
| Nasolabial angle | 102.46 | 14.42 | 96.36 | 11.81 | –6.09 | 12.58 | 0.056 |
| G’–Sn–Po’ | 1.40 | 6.52 | 3.81 | 6.89 | 2.41 | 4.25 | 0.028 |
| G’–Sn’ | –2.14 | 3.65 | –0.47 | 3.23 | 1.68 | 2.00 | 0.002* |
| G’–Pg’ | –5.02 | 9.63 | –4.52 | 9.45 | 0.49 | 4.16 | 0.621 |
*Statistically significant after Holm–Bonferroni correction for multiple comparisons.
The CG demonstrated a significant increase of maxillary and mandibular length (Co-A, Co–Gn, and Co–Go) and of complete face height (N–Me) as shown in Table 3.
Table 3.
Interphase changes in the control group (paired t-tests). SD, standard deviation
| Pre-treatment | Post-treatment | ||||||
|---|---|---|---|---|---|---|---|
| Variables | Mean | SD | Mean | SD | Diff. | SD | P |
| Sagittal skeletal | |||||||
| SNA | 78.04 | 4.95 | 78.20 | 5.57 | 0.16 | 1.63 | 0.649 |
| SNB | 77.89 | 4.62 | 78.28 | 5.14 | 0.40 | 1.71 | 0.279 |
| ANB | 0.15 | 3.86 | –0.10 | 4.41 | –0.26 | 1.38 | 0.384 |
| Wits | –2.65 | 4.06 | –2.77 | 4.91 | –0.13 | 1.98 | 0.763 |
| Co-A | 74.60 | 4.09 | 76.89 | 4.28 | 2.29 | 2.35 | <0.001* |
| Co–Gn | 102.37 | 6.94 | 107.33 | 7.72 | 4.97 | 3.01 | <0.001* |
| Co–Go | 49.02 | 3.86 | 52.37 | 4.56 | 3.36 | 2.41 | <0.001* |
| NA–AP | –0.83 | 9.14 | –1.53 | 10.88 | –0.70 | 3.28 | 0.320 |
| Vertical skeletal | |||||||
| Occ Plane to FH | 8.38 | 4.74 | 8.28 | 4.39 | –0.10 | 2.65 | 0.858 |
| FMA (MP–FH) | 31.27 | 5.55 | 31.68 | 5.39 | 0.41 | 2.04 | 0.341 |
| Ar–Go–Gn | 129.53 | 5.21 | 129.22 | 4.77 | –0.31 | 2.42 | 0.546 |
| N–Me | 107.50 | 7.77 | 111.97 | 7.72 | 4.47 | 3.15 | <0.001* |
| Teeth | |||||||
| U1–palatal plane | 102.40 | 5.97 | 105.53 | 5.49 | 3.13 | 4.95 | 0.006* |
| IMPA | 83.59 | 5.76 | 83.36 | 6.27 | –0.23 | 3.53 | 0.762 |
| Overbite | 1.06 | 2.44 | 0.38 | 2.51 | –0.68 | 2.49 | 0.204 |
| Overjet | –1.70 | 3.78 | –1.15 | 4.33 | 0.56 | 1.72 | 0.134 |
| Molar relation | –1.98 | 1.98 | –2.06 | 3.04 | –0.07 | 1.89 | 0.853 |
| Soft tissue | |||||||
| Nasolabial angle | 89.08 | 19.91 | 88.02 | 19.35 | –1.06 | 9.62 | 0.604 |
| G’–Sn–Po’ | 1.47 | 7.93 | 1.47 | 9.96 | –0.00 | 4.21 | 0.996 |
| G’–Sn | –2.03 | 4.24 | –1.33 | 4.69 | 0.69 | 1.89 | 0.093 |
| G’–Pg’ | –5.02 | 8.49 | –3.76 | 9.99 | 1.26 | 3.35 | 0.085 |
*Statistically significant after Holm–Bonferroni correction for multiple comparisons.
Intergroup comparisons (Table 4) demonstrated that BAMP caused a greater maxillary protrusion (SNA) and a greater decrease of Class III maxillomandibular discrepancy (ANB and Wits appraisal) compared with the CG. BAMP produced significantly more counterclockwise rotation of the palatal plane (Occ Plane to FH) and an improvement in the molar relationship compared with controls.
Table 4.
Intergroup comparisons (independent t-tests). SD, standard deviation
| BAMP | Control Group | ||||
|---|---|---|---|---|---|
| Variables | Mean | SD | Mean | SD | P |
| Sagittal skeletal | |||||
| SNA | 1.68 | 1.64 | 0.16 | 1.63 | 0.005* |
| SNB | –0.03 | 1.79 | 0.40 | 1.71 | 0.442 |
| ANB | 1.69 | 2.60 | –0.26 | 1.38 | 0.008* |
| WITS | 2.49 | 3.22 | –0.13 | 1.98 | 0.005* |
| Co-A | 3.37 | 2.21 | 2.21 | 2.35 | 0.125 |
| Co–Gn | 1.92 | 3.08 | 4.97 | 3.01 | 0.003* |
| Co–Go | 1.01 | 3.36 | 3.36 | 2.41 | 0.018 |
| Na–AP | 3.29 | 5.69 | –0.70 | 3.28 | 0.014 |
| Vertical skeletal | |||||
| Occ Plane to FH | –2.02 | 3.12 | –0.10 | 2.65 | 0.045* |
| FMA (MP–FH) | –1.48 | 2.81 | 0.41 | 2.04 | 0.023 |
| Ar–Go–Gn | –2.08 | 2.26 | –0.31 | 2.42 | 0.021 |
| N–Me | 2.56 | 3.77 | 4.47 | 3.15 | 0.092 |
| Teeth | |||||
| U1–palatal plane | 1.05 | 3.72 | 3.13 | 4.95 | 0.132 |
| IMPA | 1.39 | 3.95 | –0.23 | 3.53 | 0.183 |
| Overbite | –1.54 | 3.77 | –0.68 | 2.49 | 0.410 |
| Overjet | 2.35 | 3.07 | 0.56 | 1.72 | 0.036 |
| Molar relation | 3.34 | 2.12 | –0.07 | 1.89 | <0.001* |
| Soft tissue | |||||
| Nasolabial angle | –6.09 | 12.58 | –1.06 | 9.62 | 0.169 |
| G’–Sn’–Po’ | 2.41 | 4.25 | –0.00 | 4.21 | 0.078 |
| G’–Sn’ | 1.68 | 2.00 | 0.69 | 1.89 | 0.117 |
| G’–Pg’ | 0.49 | 4.16 | 1.26 | 3.35 | 0.529 |
*Statistically significant after Holm–Bonferroni correction for multiple comparisons.
Discussion
Both study groups were similar regarding age, sex, and T1–T2 interval. Both groups showed a similar ethnical background and were treated following similar protocols at a single center. However, the maxillary deficiency was more severe in the experimental group (Table 1). The possible explanation is that the CG included Goslon Yardstick 1 and 2 besides index 3, 4, and 5 as facial orthopaedics history was an exclusion criterion for this group. This is not a problem because the experimental group probably had a more unfavourable maxillary growth than the CG slightly underestimating BAMP orthopaedic effects. A limitation of this study was the comparison of reformatted CBCT cephalograms from the experimental group with conventional cephalograms of the CG. The magnification of reformatted CBCT images was 0%. However, for the traditional cephalograms, the magnification for the left and the right side of the head is different. However, the 6% magnification is calculated for the midsagittal plane of the face and the cephalometric tracing considered the mean between the right and the left side of double structures in the conventional cephalograms, minimizing this limitation.
In the BAMP group, the maxilla was moved forward increasing the SNA angle by 1.5° compared with the CG (Table 4). These results are in agreement with a previous study showing a Point A 3D displacement of 2.61 mm after BAMP therapy in UCLP (18,20). Previous studies on maxillary protraction with facemask therapy in UCLP reported SNA changes varying from 0.7° to 3.0° (8,9,23,24). However, the mean sample age of these studies was smaller compared with our study. Maxillary protraction using Liou´s-Alt-RAMEC protocol showed a mean maxillary protraction of 5.7 mm in patients with UCLP at a similar age of our experimental group (25). The greater maxillary advancement compared to BAMP therapy may be related to the double-hinged expander used previously with maxillary protraction. Similarly to facemask therapy in UCLP (24), a counterclockwise rotation of the occlusal plane was observed after BAMP therapy (Tables 2 and 4). The application of force beneath the centre of resistance of the maxilla and in the posterior region might explain these results. The slight counterclockwise rotation (2°) of the occlusal plane observed in the BAMP group should not be a clinical concern considering most of the patients with UCLP had an initial positive overbite. Furthermore, a slight anterior rotation of the mandibular plane angle (–1.48°) was observed in the BAMP group, but a slight posterior rotation (+0.41°) in the CG.
The mandibular sagittal displacement (SNB) was similar between groups even though the distance between condylion and gnathion (Co–Gn) was significantly reduced in the BAMP group compared with the CG (Table 4). These changes can be explained by the significant gonial angle closure observed in the BAMP group (Table 2). Previous studies also reported a gonial angle closure of approximately 2° after BAMP therapy in non-cleft individuals (13,26). The backward and upward force vector of Class III elastics applied to the anterior region of the mandibular body can explain the gonial angle closure. Chin cup therapy in non-cleft individuals also caused restriction of mandibular length increase and gonial angle closure (27). The gonial angle closure is not a clinical concern in patients with UCLP considering their predominant vertical growth pattern (28).
The maxillary advancement produced a significant reduction of the maxillomandibular discrepancy in BAMP group compared with controls (Table 4). Small intergroup differences in the SNB angle, although not significant, might have been a contributing factor to ANB angle improvement in the BAMP group. Wits appraisal increased by 2.5 mm in the experimental group while slightly decreased in the CG (Table 4). As a consequence of maxillomandibular sagittal relationship changes, molar relationship significantly improved in the BAMP group (Table 4). Overjet improved by 2.35 mm (SD = 3.07) although some patients did not reach a positive overjet at the end of treatment (Tables 2 and 4). Individual variation was striking in the BAMP group probably due to patient cooperation. Twenty percent of the sample declared they did not use Class III elastics properly. Variation in growth pattern and age can also explain the high level of interindividual variation. The mean amount of anteroposterior correction was not enough to solve the skeletal maxillomandibular discrepancy in all patients with UCLP who displayed severe maxillary deficiency at baseline (Table 2). These results in some cases have the potential to avoid orthognatic surgery. In others, BAMP effect might have decreased the amount of surgical maxillary advancement that will be needed after growth. Long-term follow-up is necessary to demonstrate the reduced need for orthognathic surgery after BAMP therapy.
The main difference between BAMP and facemask therapy seems to rely on the absence of dental effects in the former, whereas facemask therapy cause maxillary incisor proclination and mandibular incisor retroinclination (8,9,23,24). Another difference is that BAMP does not rotate the mandible posteriorly and downward as observed with facemask therapy (13,18). Another advantage of BAMP therapy in patients with UCLP is the decreased time of active growth after treatment once the therapy is usually applied later than facemask therapy. Finally, BAMP also permits the use of an active retention as the night use of Class III elastics until the end of growth period without any dental adverse effects.
The longitudinal stability of BAMP therapy should be studied in the future. The percentage of patients for whom Le Fort I surgery is prevented still needs to be investigated. The influence of compliance using the Class III elastics, the facial growth pattern and the degree of skeletal maturation should also be taken into consideration when evaluating the BAMP outcome in future studies. In addition, BAMP and facemask outcomes should be compared in patients with UCLP.
Conclusions
Compared with a CG, BAMP therapy in individuals with UCLP demonstrated a significant orthopaedic maxillary protraction, an improvement in the Class III skeletal pattern, a counterclockwise rotation of the palatal plane, and an improvement in the molar relationship.
Funding
Authors thank São Paulo Research Foundation (FAPESP, process #2013/19.880-0) for the financial support.
Conflict of Interest
The authors declare that they have no conflict of interest.
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