Influence of bone-anchored maxillary protraction on secondary alveolar bone graft status in unilateral complete cleft lip and palate

Introduction

Our objective was to evaluate the effects of bone-anchored maxillary protraction (BAMP) on the status of the secondary alveolar bone graft in patients with unilateral complete cleft lip and palate (UCLP).

Methods

The experimental group (EG) comprised 26 patients with UCLP, mean age of 11.9 years, submitted to secondary alveolar bone grafting (SABG) with recombinant bone morphogenetic protein, and BAMP therapy, using miniplate-borne Class III intermaxillary elastics. Cone beam computed tomography (CBCT) examinations were taken 6 months after SABG and before BAMP (T1) and after 18 months of BAMP therapy (T2). The control group (CG) was composed of 24 patients with UCLP submitted only to SABG with recombinant bone morphogenetic protein or autogenous bone from iliac crest without BAMP therapy, matched by initial age and sex with the EG. In the CG, CBCT examinations were performed 6 months (T1) and 12 months (T2) after SABG surgery. CBCT axial sections were analyzed using Garib scores in both time points. Intra- and intergroup comparisons were performed using Wilcoxon and Mann-Whitney tests, respectively ( P <0.05).

Results

No intergroup differences were found at T1 and T2. The EG showed significant improvement of graft status from T1 to T2 at the cervical and middle levels of the alveolar cleft. No significant interphase differences were found for graft scores in the CG.

Conclusions

Despite loads of intermaxillary elastics applied to the maxilla, no harm to the grafted alveolar bone was observed after BAMP therapy in patients with UCLP.

Highlights

  • Alveolar bone grafts of UCLP patients were evaluated using CBCT before and after BAMP.

  • The graft was evaluated in 3 different sites longitudinally.

  • No harm on the grafted alveolar bone was observed after BAMP therapy.

Skeletal anchorage recently opened a new window for facial orthopedics. In patients with Class III malocclusion, bone-anchored maxillary protraction (BAMP) demonstrated significant anterior displacement of the midface, a slight restriction of anterior displacement of the mandible, anterior crossbite correction, and improvement on the facial profile. Maxillary deficiency in patients with unilateral complete cleft lip and palate (UCLP) was shown to be adequately managed with BAMP therapy during late mixed or early permanent dentition. BAMP in UCLP was found to be symmetric and similar to that in patients without cleft lip and palate in both jaws. ,

Secondary alveolar bone grafting (SABG) with autogenous bone from the iliac crest is the gold standard with adequate outcomes. Since the introduction of the alveolar bone graft, materials have been studied as an alternative to autogenous graft to prevent invasive procedures. Recombinant bone morphogenetic protein (rhBMP-2) has been one of the main alternatives for autogenous SABG. The option of grafting with rhBMP-2 is relatively recent, but studies have demonstrated success rates similar to the autogenous gold standard.

The alveolar bone bridge formed after SABG fuses maxillary segments as a single bone. However, the grafted alveolar region might be a vulnerable area because of a smaller labiolingual thickness when compared with the neighboring maxillary alveolar ridge. Could sagittal forces of compression influence the newly formed bone? No previous work has investigated such an assumption. No previous studies have evaluated the effects of Class III elastics from BAMP therapy on the status of the grafted alveolar cleft. Therefore, this study aimed to assess the outcome of BAMP technique on the status of secondary alveolar bone graft performed with rhBMP-2 in patients with UCLP. The hypothesis is that there is no difference in alveolar graft status between patients treated with or without BAMP therapy.

Material and methods

Ethics committee approval was obtained from the Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo, Brazil (protocol no. 65573717.8.0000.5441). For the sample size calculation, a significance level of 5%, power of 80%, and effect size of 0.9 were adopted, resulting in a sample size of n′ = 20.4 elements per group. Once nonparametric tests were used for comparison between the groups, a nonparametric procedure was performed on the basis of asymptotic relative efficiency (n = n′/ 0.864), resulting in a minimum sample size of 24 elements per group. This retrospective longitudinal study comprised 2 groups of patients with UCLP from a single rehabilitation center.

The experimental group (EG) was composed of 26 patients (17 males and 9 females) with a mean initial age of 11.9 years (standard deviation [SD], 0.75) treated with BAMP therapy 6 months after rh-BMP2 SABG. Patients had an interarch relationship (Goslon Yardstick index) of 3, 4, or 5 (mild, moderate, and severe maxillary deficiency, respectively) and were treated in a previous study. The mean initial overjet was −4.98 (SD, 2.73). CBCT scans were taken before (T1) and right after (T2) BAMP therapy with an interval of 18 months. Bollard miniplates were installed 6 months after SABG surgery by the same surgeon on the infrazygomatic crest in the posterior region of maxilla and between the roots of canines and lateral incisors on the anterior region of the mandible. Full-time Class III elastics were delivered 3 weeks after miniplates placement with an initial load of 100 g of force, which was increased gradually to 250 g of force in the following months. During BAMP therapy, patients with negative overbite wore a biteplate in the maxillary arch until the correction of the crossbite. SNA and SNB mean change was 1.68 (SD, 1.64) and −0.03 (SD, 1.79), respectively. The overjet mean change was 2.35 (SD, 3.07). Figure 1 shows an example of the treatment outcome.

Fig 1
Patient from the EG before initiating BAMP therapy (A) and 18 months after (B) .

The control group (CG) comprised 24 patients (16 males and 8 females) with a mean age of 10.5 years not submitted to BAMP therapy. Secondary alveolar bone graft surgery was performed either with rhBMP-2 (n = 12) or autogenous cancellous bone from the iliac crest (n = 12). SABG surgeries of both groups were performed by 2 surgeons from a single center.

CBCT examinations had been previously obtained using the 3-dimensional i-CAT system (Imaging Sciences International, Hatfield, Pa) with settings: 120 kVp; 5 mA; 0.3-mm voxel size; scan time, 4.8-8.9 seconds; field of view of 13 cm in height × 16 cm in depth. The analysis was performed using 3D Slicer software 4.0 (Slicer, Ann Arbor, Mich).

To assess the axial slices, we standardized the head position following the long axis of the maxillary central incisor on the noncleft side perpendicular to the horizontal plane in both sagittal and coronal views ( Fig 2 ). Three axial sections at 3 mm, 6 mm, and 9 mm apically to the cementoenamel junction of the referred tooth were used to represent the cervical, middle, and apical root thirds, respectively ( Fig 3 ).

Fig 2
Standardization of the CBCT scan keeping the long axis of the maxillary central incisor contralateral to the cleft coincident to the vertical sagittal and coronal reference lines (3D Slicer software 4.0).

Fig 3
Axial CBCT slices from an EG patient at 3 mm (A) , 6 mm (B) , and 9 mm (C) apically to the cementoenamel junction.

Statistical analysis

Two raters (O.S.G. and D.G.) have evaluated the graft alveolar cleft using the method by Garib et al ( Fig 4 ). The first rater performed 2 evaluations within 15 days. Intrarater and interrater agreements were determined using kappa statistics. Intergroup comparison was performed using the Mann-Whitney test. The intragroup comparison was performed using the Wilcoxon test. Statistical analysis was conducted using SigmaPlot (version 11; Systat Software GmbH, Erkrath, Germany). Results were regarded for P <0.05.

Fig 4
Illustration representing the scores attributed to tomographic reconstructions. 0 , no bone bridge mesially to the maxillary canine and no visible bone covering both roots of adjacent teeth; 1 , no bone bridge mesially to the maxillary canine and presence of visible bone covering only 1 of the adjacent roots; 2 , no bone bridge mesially to the maxillary canine and presence of visible bone covering both roots of the adjacent teeth; 3 , narrow alveolar bone bridge mesially to canine. The bone bridge was considered narrow when corresponded to less than 50% of the labiolingual thickness of the adjacent canine image; 4 , complete alveolar bone bridge present mesially to the maxillary canine. The bone bridge was considered adequate when corresponded to more than 50% of the labiolingual thickness of the adjacent canine image.

Results

Both intrarater and interrater agreements were excellent ( Table I ).

Table I
Intrarater and interrater reliabilities by kappa index
Comparison Reproducibility 95% CI
Examiner 1 × examiner 1 0.91 0.84-0.99
Examiner 1 × examiner 2 0.91 0.84-0.99

CI , confidence interval.

Excellent reproducibility.

In the EG, a graft status improvement was observed between T1 and T2. No interphase differences were found for the graft status in the CG ( Table II ).

Table II
Intragroup comparison (Wilcoxon test)
Group Measurements, mm Pre- or posttreatment Median 25% 75% P
EG 3.0 T1 2.0 2.0 3.8 <0.001
T2 4.0 3.0 4.0
6.0 T1 3.0 2.0 4.0 0.042
T2 4.0 3.0 4.0
9.0 T1 4.0 2.0 4.0 0.375
T2 4.0 3.5 4.0
CG 3.0 T1 4.0 1.0 4.0 0.625
T2 4.0 2.5 4.0
6.0 T1 4.0 3.0 4.0 0.500
T2 4.0 3.0 4.0
9.0 T1 4.0 2.3 4.0 0.129
T2 4.0 3.0 4.0
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Jan 9, 2021 | Posted by in Orthodontics | Comments Off on Influence of bone-anchored maxillary protraction on secondary alveolar bone graft status in unilateral complete cleft lip and palate
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