Background
The objective of this study was to assess the long-term stability of bone-anchored maxillary protraction (BAMP) in patients with unilateral complete cleft lip and palate (UCLP) and sagittal midface deficiency.
Methods
The sample comprised 30 patients with UCLP (20 males and 10 females), with a mean age of 11.8 years (standard deviation = 0.79 years). All patients presented with moderate to severe maxillary deficiencies and were prospectively treated with BAMP for 18 months. Cone-beam computed tomography was obtained before (T1) and after BAMP therapy (T2), whereas conventional lateral cephalograms were acquired at least 5 years after BAMP therapy (T3: mean age = 20.15 years, standard deviation = 2.38 years). Moreover, 3 patients were lost during the follow-up, and 1 was excluded because of missing T2 records. Interphase comparisons were performed using analysis of variance and Tukey honest significant difference test ( P <0.05). Discriminant analysis was used to identify pre and posttreatment predictive variables associated with surgical or nonsurgical outcomes.
Results
Among the 26 patients included in the final sample, 46.2% (n = 12) received nonsurgical treatment in phase 2, whereas 53.8% (n = 14) required orthognathic surgery. In the nonsurgical subgroup, the outcomes achieved with BAMP therapy remained stable from T2 to T3. In the surgical subgroup, treatment changes were negligible, and an impairment of facial convexity was observed during the posttreatment follow-up. Discriminant analysis revealed that pretreatment indicators predictive of nonsurgical outcomes included a less negative overjet, a smaller mandibular plane angle, and a reduced gonial angle. Greater improvements in the ANB angle and overjet during treatment were associated with a higher likelihood of a nonsurgical outcome.
Conclusions
Patients with UCLP who achieved a positive overjet during BAMP therapy remained stable in the long-term, and orthognathic surgery was avoided. Hyperdivergent growth pattern with obtuse gonial angle and more severe negative overjet were initial predictors of the need for orthognathic surgery. Greater correction of the skeletal maxillomandibular relationship and overjet during BAMP therapy was associated with nonsurgical outcomes.
Highlights
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Bone-anchored maxillary protraction can reduce the need for orthognathic surgery in unilateral complete cleft lip and palate.
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An increased gonial angle was a predictor of surgical outcomes.
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Greater increase in the ANB angle and overjet were indicators of nonsurgical outcomes.
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Careful case selection and patient compliance are essential.
Maxillary growth deficiencies present a significant challenge in the comprehensive care of patients with complete unilateral cleft lip and palate (UCLP). The development of the maxilla is compromised from the embryonic phase as a result of mesenchymal deficiencies. After birth, lip and palate repair restricts transverse, vertical, and sagittal maxillary growth. , Midface retrusion leads to anterior crossbites and adversely affects functional, esthetic, respiratory, and psychosocial aspects. ,,
Sagittal growth deficiencies in patients with cleft lip and palate are typically addressed with facemask therapy during the mixed dentition phase. , Collateral effects, including a clockwise rotation of the mandible, an increase in the anterior facial height, and dental compensations, have been previously described. , Another limitation of facemask therapy in patients with complete cleft lip and palate is the long-term instability. , Facemask therapy is typically initiated long before skeletal maturity, and despite treatment, maxillary growth deficiencies frequently persist thereafter.
The advent of skeletal anchorage has introduced new possibilities for orthopedic maxillary protraction in adolescent patients with Class III malocclusion. The protocol, described by De Clerck et al, consisted of bone-anchored maxillary protraction (BAMP), in which full-time Class III elastics were anchored on 2 posterior miniplates inserted in the maxilla and 2 anterior miniplates placed in the mandible. Short-term outcomes of BAMP included midface protraction, slight posterior displacement of the condyles and mandibular ramus, and a decrease in the gonial angle. No palatal or mandibular plane rotation was observed after BAMP therapy.
BAMP has previously been applied in patients with complete cleft lip and palate. ,,,,,,,, The short-term outcomes of BAMP therapy in patients with UCLP were comparable to those observed in patients with no cleft, despite the presence of scar and fibrosis surrounding the repaired maxilla. The evaluation of long-term stability is essential to determine whether BAMP can prevent the need for LeFort I osteotomy at the end of the pubertal growth spurt. However, no previous study has assessed the long-term stability of BAMP therapy in patients with UCLP. The hypothesis is that BAMP therapy has the potential for stability and orthognathic surgery avoidance, provided that treatment timing is closer to the end of pubertal growth spurt and that Class III elastics could be used on the miniplates as retention during nighttime without inducing dental collateral effects. A Supplementary Table with a comparative summary of BAMP studies in oral clefts is provided.
The objective of this study was to evaluate the long-term stability of BAMP in patients with UCLP presenting with midface sagittal deficiencies. In addition, this study aimed to determine the extent to which BAMP reduced the need for surgery at the completion of facial growth and identify variables associated with nonsurgical vs surgical outcomes.
Material and methods
Ethical committee approval was obtained from the Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo (protocol No. 72919423.5.0000.5441). The study was prospective. Eligible patients between October 2011 and February 2014 were recruited. , Considering a minimum detectable difference of 1.5° in the SNA angle for interphase changes, a standard deviation (SD) of 1.6° (Faco et al ), a statistical power of 80%, and a 2-sided alpha level of 5%, a sample size of 9 patients was required in each subgroup. A sample loss of 20% was assumed because of the longitudinal study design, resulting in an initial sample of 22 patients, 11 per group.
At baseline, the complete sample consisted of 30 patients with UCLP (20 males and 10 females) and a mean age of 11.9 years (SD = 0.8 years) from a single center. All patients displayed moderate to severe maxillary deficiencies with a mean initial Wits appraisal of −5.53 (SD = 3.60) and were treated with BAMP. The initial inclusion criteria comprised patients between 10-13 years of age, with a Goslon Yardstick index of 3, 4, or 5, in late mixed or early permanent dentition, exhibiting fully erupted mandibular permanent canines, and having undergone secondary alveolar bone grafting ≥6 months before BAMP therapy. The exclusion criteria were the presence of syndromes and inadequate oral hygiene.
Transverse maxillary deficiencies were corrected before the start of the study through rapid maxillary expansion, performed before the secondary alveolar bone grafting procedure during the mixed dentition stage. All patients were treated with BAMP using 2 Bollard miniplates (Tita-Link, Brussels, Belgium) inserted into the maxillary infrazygomatic crest and 2 miniplates positioned bilaterally between the roots of the mandibular permanent canines and lateral incisors. Three weeks after miniplate placement, full-time Class III intermaxillary elastics (G&H Orthodontics, Franklin, Ind) were used connecting the maxillary and mandibular miniplates bilaterally. Traction started at 75 g of force on each side, gradually increasing to 150 g of force in the second month and 250 g of force in the third month, which was maintained until the completion of active treatment. Class III elastics were replaced twice daily, in the morning and evening. In addition, removable bite plates were used in the maxillary arch to avoid occlusal interference during the crossbite correction. The bite plates received springs positioned palatally to the permanent incisors, which were slightly activated only when the incisors reached an edge-to-edge relationship. After achieving a positive overjet, the bite plates were removed to allow for the spontaneous correction of the posterior open bite. In the complete sample, the endpoint of active BAMP therapy was the achievement of a positive overjet. After achieving a positive overjet, Class III elastics were used during nighttime on the miniplates as an active retention until the end of pubertal growth spurt, simultaneously with comprehensive orthodontic treatment. No extractions were performed in the mandibular arch in any patient. During the comprehensive orthodontic treatment, mild dental compensation was carried out by tipping the maxillary incisors labially. When a positive overjet was not achieved, BAMP therapy was interrupted within 18 months, and no retention was placed. The mean duration of BAMP therapy was 18 months (SD = 3 months). Comprehensive orthodontic treatment was started, and Class III elastics were used during nighttime on the miniplates as an active retention until the completion of the pubertal growth spurt. The end of the pubertal spurt was defined according to the Fishman skeletal maturity indicators, specifically when the epiphysis of the radius demonstrated complete mineralization (Skeletal maturation indicator [SMI 11]). In male patients, retention with Class III elastics was maintained even after debonding, in conjunction with orthodontic retention using a Hawley plate in the maxillary arch and a 3 × 3 fixed retainer in the mandibular arch. Retention period with nighttime elastics was 39 ± 8 months.
After BAMP therapy, patients were allocated to either orthognathic surgery or compensatory orthodontic treatment without surgery. The primary criterion for selecting the treatment modality following BAMP therapy was the overjet. Patients with a positive or edge-to-edge overjet were managed nonsurgically. As a secondary criterion, the Wits appraisal ≤–1mm and patient-reported concerns regarding facial esthetics were considered as an indication for orthognathic surgery, even in patients with a positive or edge-to-edge overjet. However, none of the patients in this category reported esthetic concerns, and all were treated nonsurgically. In contrast, patients presenting with a negative overjet and Wits appraisal ≤–1mm were initially offered orthognathic surgery as the primary treatment option, and all accepted this treatment plan.
Cone-beam computed tomography scans (CBCT) were obtained before (T1: mean age = 11.89 years, SD = 0.79 years) and after BAMP therapy (T2: mean age = 13.30 years, SD = 0.81 years). After a mean of 6.77 years post-BAMP therapy, a follow-up assessment was performed in 26 out of 30 patients using digital lateral cephalograms (T3: mean age = 20.15 years, SD = 2.38 years) obtained from March 2019 to November 2023. Three patients discontinued treatment during the active BAMP phase: 1 because of miniplate instability, and 2 because they did not adapt to the protocol and did not wish to continue the treatment. One patient was excluded because of incomplete dental records at T2, considering that the post-BAMP CBCT was missing. The final sample comprised 26 patients (16 males and 10 females). Synthetic lateral cephalograms generated from T1 and T2 CBCT images, along with the T3 conventional lateral cephalogram, were analyzed using Dolphin Imaging & Management Solutions 11.5 software (Patterson Dental Supply Inc, Chatsworth, Calif). The 6% magnification factor of cephalometric images obtained at T3 was corrected. Eleven cephalometric variables were analyzed ( Fig 1 ).
Cephalometric variables ([1] SNA; [2] SNB; 3. ANB; [4] Wits appraisal; [5] FMA; [6] gonial angle [Ar-Go-Gn]; [7] maxillary incisor labiolingual inclination [U1-palatine plane]; [8] mandibular incisor to mandibular plane angle [IMPA]; [9] overjet; [10] overbite; [11] molar relationship).
Statistical analysis
Cephalograms were retraced after a 15-day interval in 30% of the sample. Systematic and random errors were assessed using paired-samples t tests and the Dahlberg formula, respectively. Data normality was evaluated with the Shapiro-Wilk test. Interphase comparisons were performed using analysis of variance followed by Tukey honest significant difference test ( P <0.05). Stepwise discriminant analysis was conducted to identify pre and posttreatment variables predictive of nonsurgical vs surgicalgroup classification. Statistical analyses were performed using SPSS Statistics (version 25.0, NY) and BioEstat software (version 5.3, Amazonas, Brazil).
Results
No significant systematic errors were detected for the cephalometric variables. Random errors ranged from 0.526° (SNB angle) to 2.542° (U1-PP angle).
In the final sample of 26 patients with UCLP treated with BAMP and followed long-term, 12 patients (46.2%) were treated nonsurgically, whereas 14 patients (53.8%) underwent orthognathic surgery. No significant differences were observed in initial mean age and gender distribution between the nonsurgical and surgical groups ( Table I ). At T3, 9 of the 14 patients indicated for surgery had been operated on a mean time of 3.7 years before, whereas 5 were still awaiting surgery. Of those operated, 8 underwent bimaxillary surgery and 1 underwent maxillary surgery only.
Table I
Gender distribution and age at T1, T2, and T3
| Gender | Age, y (T1) | Age, y (T2) | Age, y (T3) | |||
|---|---|---|---|---|---|---|
| Female | Male | Total | mean (SD) | mean (SD) | mean (SD) | |
| Nonsurgical group | 5 | 7 | 12 | 11.83 (0.90) | 13.24 (1.00) | 18.81 (2.66) |
| Surgical group | 5 | 9 | 14 | 11.94 (0.70) | 13.48 (0.63) | 21.30 (1.37) |
| Total | 10 | 16 | 26 | |||
| P value | 0.7558 | 0.7000 | 0.4566 | 0.0052 | ||
Interphase changes in the nonsurgical subgroup are presented in Table II . After BAMP therapy (T3-T2), the maxillary advancement observed during treatment remained stable ( Table II ). No changes were observed in the mandible during the treatment and follow-up period ( Table II ). The anteroposterior relationship between the maxilla and the mandible improved during BAMP therapy and remained stable over the long term ( Table II ). The mandibular plane exhibited a counterclockwise rotation, and a closure of the gonial angle was observed over time ( Table II ). The labial tipping of the maxillary incisors increased both during and after BAMP therapy ( Table II ). No significant changes were observed in the inclination of the mandibular incisors ( Table II ). The overjet increased both during BAMP therapy and throughout the follow-up period ( Table II ). No interphase changes were observed for the overbite and molar relationship ( Table II ).
Table II
Interphase changes in the nonsurgical and surgical subgroups (analysis of variance and Tukey honest significant difference tests)
| Subgroup | T1 | T2 | T3 | Confidence interval | P value | |||
|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | |||
| Nonsurgical | ||||||||
| SNA ( o) | 74.02 | 3.53 | 75.18 | 4.01 | 75.27 | 3.66 | [73.62 to 76.02] | 0.028 |
| SNB ( o) | 75.42 | 4.57 | 74.17 | 3.98 | 75.56 | 4.16 | [73.69 to 76.41] | 0.088 |
| ANB ( o) | –1.24 | 2.96 | 0.85 | 3.34 | –0.16 | 2.67 | [–1.26 to 0.70] | 0.021 |
| Wits (mm) | –5.03 | 3.91 | –2.27 | 3.88 | –2.63 | 4.23 | [–4.64 to–1.97] | 0.007 |
| FMA ( o) | 28.15 | 3.98 | 27.18 | 5.15 | 25.01 | 5.52 | [25.16 to 28.40] | 0.016 |
| Ar-Go-Gn ( o) | 125.63 | 5.39 | 123.44 | 6.42 | 121.53 | 5.81 | [121.59 to 125.48] | 0.001 |
| U1-PP ( o) | 113.36 | 6.73 | 116.11 | 8.43 | 119.54 | 6.89 | [113.85 to 118.83] | 0.018 |
| IMPA ( o) | 78.83 | 5.66 | 80.43 | 5.83 | 82.34 | 7.90 | [78.40 to 82.66] | 0.386 |
| Overjet (mm) | –2.74 | 1.76 | 1.17 | 2.12 | 2.34 | 1.28 | [–0.65 to 1.17] | <0.001 |
| Overbite (mm) | 1.60 | 3.46 | 0.54 | 1.36 | 1.22 | 1.01 | [0.40 to 1.84] | 0.480 |
| M/R (mm) | –1.71 | 2.07 | 0.18 | 3.28 | –0.92 | 2.82 | [–1.73 to 0.10] | 0.230 |
| Surgical | ||||||||
| SNA ( o) | 73.86 | 3.84 | 74.86 | 4.17 | 74.98 | 4.32 | [73.30 to 75.85] | 0.362 |
| SNB ( o) | 76.87 | 4.76 | 77.25 | 5.38 | 80.73 | 4.84 | [76.67 to 79.90] | <0.001 |
| ANB ( o) | –3.01 | 2.98 | –2.39 | 3.79 | –5.75 | 3.30 | [–4.93 to–2.69] | 0.002 |
| Wits (mm) | –5.98 | 3.40 | –4.79 | 4.69 | –6.85 | 4.79 | [–7.22 to–4.53] | 0.276 |
| FMA ( o) | 31.99 | 5.23 | 30.33 | 5.15 | 27.06 | 6.37 | [27.97 to 31.62] | <0.001 |
| Ar-Go-Gn ( o) | 129.79 | 4.47 | 128.69 | 4.07 | 129.15 | 5.50 | [127.77 to 130.65] | 0.516 |
| U1-PP ( o) | 114.71 | 7.30 | 115.13 | 8.86 | 118.91 | 7.15 | [113.80 to 118.70] | 0.319 |
| IMPA ( o) | 76.62 | 6.62 | 79.89 | 7.40 | 82.34 | 8.10 | [77.25 to 81.98] | 0.008 |
| Overjet (mm) | –4.86 | 2.55 | –3.87 | 3.51 | –2.26 | 4.76 | [–4.84 to–2.48] | 0.191 |
| Overbite (mm) | 0.21 | 2.40 | 0.48 | 1.97 | –1.78 | 4.37 | [–1.36 to 0.63] | 0.191 |
| M/R (mm) | –3.24 | 3.03 | –1.01 | 2.93 | –2.04 | 3.71 | [–3.12 to–1.07] | 0.163 |
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