Introduction
The association between maxillary protraction and bone graft in patients with cleft lip and palate remains unclear. The purpose of this study was to investigate whether a secondary alveolar bone graft influences dentoskeletal effects of facemask therapy in unilateral cleft lip and palate patients with a skeletal Class III relationship.
Methods
In this prospective nonrandomized clinical trial, 61 consecutive boys with unilateral cleft lip and palate and skeletal Class III malocclusion were divided into 3 groups: grafted facemask group (n = 21), ungrafted facemask group (n = 20), and untreated control group (n = 20). Sixteen dentoskeletal measurements on lateral cephalometric radiographs were compared before and after therapy or observation with 1-way analysis of variance or the Mann-Whitney U test.
Results
After facemask therapy, the grafted group showed a statistically significantly greater advancement of Point A (S-Vert-A, 4.18 ± 1.94 mm; SNA, 3.51° ± 2.21°) than did the ungrafted group (S-Vert-A, 2.64 ± 1.58 mm; SNA, 1.92° ± 1.05°). Furthermore, significant SNB changes were found in the grafted group when compared with those in the ungrafted group (−0.38° ± 1.77° vs −1.69° ± 1.34°; P <0.05). The changes in the mandibular plane angle (MP-SN, MP-FH) in the grafted group were less pronounced than in the ungrafted group by approximately 2° ( P <0.05). Flaring of the maxillary incisors was more pronounced in treated subjects than in untreated subjects. The mandibular incisors proclined in both grafted (1.54° ± 4.21°) and control (0.97° ± 3.71°) patients, and were retroclined in the ungrafted group (−2.13° ± 3.68°).
Conclusions
Facemask therapy performed after an alveolar bone graft produced more anterior maxillary migration (90%) and less pronounced mandibular clockwise rotation (10%) than those in the ungrafted group (50%, 50%, respectively).
Highlights
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We evaluated bone grafting effects on maxillary protraction in skeletal Class III cleft patients.
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Facemask therapy after bone grafts led to pronounced maxillary advancement in UCLP patients.
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Maxillary protraction after alveolar bone grafts led to less pronounced mandibular clockwise rotation in UCLP patients.
Skeletal Class III malocclusion with maxillofacial growth dysplasia is common in patients with operated cleft lip and palate and results in personal, social, functional, and psychological problems. The management of this craniofacial malformation is challenging, primarily because of the maxillary retrusion coupled with potentially unfavorable mandibular growth.
By exerting directed, constant anterior force on the maxilla, facemask therapy can foster balanced skeletal harmony and a favorable occlusion. It is widely implemented in the mixed or early permanent dentition and before the peak pubertal growth to alleviate the need for future orthognathic surgery.
Kim et al concluded that the optimal timing for anterior protraction in Class III children may involve initiating maxillary protraction before age 10. Early mixed dentition is also favored over late, presumably because of the closure of the sutures in the vicinity of the nasomaxillary complex.
In the meantime, a secondary alveolar bone graft, which is optimally carried out between 9 and 11 years of age, before the eruption of the permanent canines, has become the state of the art. Its purpose is to reconstruct the anatomy of the maxillary alveolar process and restore the integrity of the maxillary dental arch to benefit the orthodontic tooth movement in the cleft area.
With the proximity of timing of maxillary protraction and secondary alveolar bone graft, the treatment sequencing lacks clinical evidence, and the patient is often subject to hospitalization. In addition, the synergistic effects of bone graft and maxillary protraction remain apparently unexamined in vivo. It is unknown whether a secondary alveolar bone graft influences the outcomes of facemask therapy. Up to now, 2 studies of 3-dimensional finite element analysis are available, suggesting the advantage of secondary alveolar bone graft before maxillary protraction.
We conducted a prospective clinical trial to compare the dentoskeletal effects of preadolescent boys with unilateral cleft lip and palate (UCLP) treated with facemask before and after secondary alveolar bone graft. The null hypothesis was that skeletal and dental differences do not exist between the treated groups with these protocols.
Material and methods
This clinical trial was approved by the ethics committee of the Peking University School of Stomatology, People’s Republic of China. All clinical investigations were carried out according to the guidelines of the Declaration of Helsinki. Informed consent from the subjects and their guardians was obtained in written format.
This study was designed as a prospective nonrandomized clinical trial to determine the effect of secondary alveolar bone graft on facemask therapy in growing patients with UCLP. In a northern Chinese population, boys with skeletal Class III UCLP were enrolled according to the following inclusion criteria: (1) operated nonsyndromic UCLP; (2) concave profile with anterior crossbite; (3) palatoplasty surgery before 3 years of age; (4) no pharyngeal flap surgery; (5) −4° ≤ ANB ≤ 0°; and (6) cervical vertebral maturation stage between CS1 and CS3. The exclusion criteria were additional congenital anomaly, temporomandibular disorder, or previous orthodontic treatment.
In each group, a sample size of 16 subjects was estimated at power of 80% and 0.05 level of significance, which would enable significant detection between the protracted and unprotracted groups in the distance from Point A to the y-axis line of 1 mm with a standard deviation of 0.98 mm. To allow for a 20% loss, 61 patients in total participated in this study initially.
Based on hospitalization and family preference, 61 boys with UCLP were enrolled in 3 groups: (1) a grafted facemask group containing 21 patients with hypoplastic maxilla, who had undergone secondary alveolar bone graft at least 5 months previously to allow for clinically and radiographically successful osseointegration; (2) an ungrafted facemask group containing 20 patients with a history of complete UCLP, without alveolar bone grafting; and (3) an unprotracted control group containing 20 patients who had not been treated because of loss of anchor teeth, matched to the treated subjects with regard to sex, age, skeletal structure, and cleft type, and subsequently received treatment after the eruption of the maxillary permanent first premolars.
Subjects in the protracted groups were treated with facemask by an orthodontist (W.L.) at the Department of Orthodontics, Peking University Hospital of Stomatology, Beijing, China. All surgical procedures including the secondary alveolar bone graft (cancellous bone graft from the iliac crest) were performed in the Cleft Lip and Palate Treatment Center, Peking University Hospital of Stomatology. Before protraction, all patients in the grafted group had attained interdental septum of category I or II according to the standard system of Bergland et al.
All patients successfully finished the treatment except for 3 in the grafted group and 2 each in the ungrafted group and the control group, who dropped out because of poor compliance. Consequently, 18 boys remained in each group for analysis: the grafted group (age, 9.98 ± 1.10 years), the ungrafted group (age, 9.54 ± 1.30 years), and the control group (age, 9.76 ± 1.43 years).
In both treatment groups, the Hyrax appliance was banded on the maxillary permanent first molars and deciduous first molars or permanent first premolars. Protraction hooks were soldered bilaterally to the buccal aspects of the permanent first molar bands and extended anteriorly to the canine area. The protraction elastics were 30° down the occlusal plane, and the protraction force was 450 to 500 g per side. Maxillary expansion was not conducted. Bite-block appliances in the mandibular arch were inserted to prevent incisor interference. All patients were instructed to wear the facemask (Tiantian Dental Equipment, Hunan, China) for a minimum of 12 to 14 hours per day. Facemask therapy was continued until a positive overjet was achieved. Radiographic observations after about one year were performed in the control group.
Lateral cephalometric radiographs were obtained on all experimental subjects before treatment or observation and after completion of protraction treatment or observation using the same cephalostat. A horizontal reference line that angulated 7° clockwise from the SN line passing through S point was registered as the x-axis, and a perpendicular line was subsequently constructed through S point as the y-axis. The cephalometric landmarks and measurements are shown in the Figure and Table I . Sixteen dentoskeletal variables were measured on the cephalograms; landmarks were traced by an experienced investigator (Y.Z.) and reconfirmed by another investigator (R.G.). Software (version 11.7; Dolphin Imaging and Management Solutions, Chatsworth, Calif) was used for evaluation of the cephalograms. All variables were reassessed by the same operator (Y.Z.) 2 weeks later.
| Variable | Definition |
|---|---|
| SNA (°) | Angle between subspinale and sella at nasion, indicating the horizontal position of the maxilla relative to the cranial base |
| S-Vert-A (mm) | Horizontal distance from subspinale to a plane drawn perpendicularly to SN-7 plane (horizontal plane angulated 7° clochwise to the SN plane) at S |
| Ptm-A/PP (mm) | Distance between subspinale and Ptm projected on the palatal plane, respectively |
| SN-PP (°) | Angle between the SN plane and the palatal plane) |
| SNB (°) | Angle between supramental and sella at nasion, indicating the horizontal position of the mandible relative to the cranial base |
| MP-SN (°) | Angle between the mandibular plane and SN plane, representing mandibular inclination |
| MP-FH (°) | Angle between the mandibular plane and Frankfort horizontal plane, representing mandibular inclination |
| y-axis (°) | Angle between the y-axis (line connecting sella to gnathion) and Frankfort horizontal plane |
| ANB (°) | Angle between subspinale and supramental at nasion, indicating the relative positions of the maxilla and mandible in relation to the cranium |
| Wits (mm) | Distance between the points of perpendiculars tracing from Points A and B contact on the occlusal plane, indicating the relative positions of the maxilla and mandible anteroposteriorly |
| U1-SN (°) | Angle between the long axis of the maxillary central incisor and the SN plane, determining the inclination of the central incisor relative to the anterior cranial base |
| IMPA (°) | Angle between the long axis of the mandibular central incisor and the mandibular plane, determining the axial inclination between the mandibular incisor and the inferior border of the mandible |
| U1-L1 (°) | Angle between the long axis of the maxillary central incisor and the mandibular central incisor, determining the degree of labial inclination of the incisors |
| SN-FOP (°) | Angle between the SN plane and FOP plane (occlusal plane) |
| Overjet (mm) | Distance between the maxillary anterior teeth ridges and the mandibular anterior teeth ridges in the anteroposterior axis |
| Overbite (mm) | Distance between the maxillary anterior teeth ridges and the mandibular anterior teeth ridges in the vertical axis |
Statistical analysis
First, a 1-sample Kolmogorov-Smirnov test showed all the variables to be normally distributed. Second, after the Levene test of equality of variance, a Mann-Whitney U test was performed on the SN-PP at baseline, the treatment changes in SNA, U1-L1, overbite, and overjet, all of which were labeled as variance-unequal. Third, all remaining cephalometric variables, ages, and durations of treatment or observation were analyzed with 1-way analysis of variance (ANOVA). Pairwise comparison was performed with post hoc least significant difference test. All statistical analyses were performed with the SPSS software package (version 20.0; IBM, Armonk, NY). The significance level was set at P <0.05 for all tests. To calculate the intraexaminer difference, 5 randomly selected pairs of data from each group were measured twice by the same investigator (Y.Z.) 2 weeks later. Correlation coefficients of each measurement were then calculated.
Results
The age distributions and treatment durations among the 3 groups were well matched ( Table II ). The intraclass correlation coefficients calculated for the repeatability test ( Table III ) were all above 0.9, indicating high reliability.
| Grafted | Ungrafted | Control | Grafted vs ungrafted | Grafted vs control | Ungrafted vs control | |
|---|---|---|---|---|---|---|
| Mean (SD) | Mean (SD) | Mean (SD) | P ∗ | P ∗ | P ∗ | |
| T0 (y) | 9.98 (1.10) | 9.54 (1.30) | 9.76 (1.43) | 0.563 | 0.861 | 0.868 |
| T1 (y) | 11.24 (0.99) | 10.88 (1.33) | 10.81 (1.25) | 0.647 | 0.529 | 0.980 |
| Duration (mo) | 15.06 (5.83) | 16.06 (5.91) | 12.50 (4.63) | 0.848 | 0.350 | 0.137 |
∗ One-way ANOVA and post hoc least significant difference test.
| Variable | Mean | SD | ICC |
|---|---|---|---|
| Maxillary | |||
| SNA (°) | −0.11 | 0.53 | 0.985 |
| S-Vert-A (mm) | 0.23 | 0.61 | 0.990 |
| Ptm-A/PP (mm) | 0.31 | 0.73 | 0.969 |
| SN-PP (°) | −0.26 | 0.72 | 0.964 |
| Mandibular | |||
| SNB (°) | 0.15 | 0.85 | 0.965 |
| MP-SN (°) | −0.14 | 0.73 | 0.987 |
| MP-FH (°) | 0.27 | 0.61 | 0.988 |
| y-axis (°) | 0.04 | 0.84 | 0.952 |
| Maxillomandibular | |||
| ANB (°) | −0.13 | 0.58 | 0.918 |
| Wits (mm) | 0.03 | 0.73 | 0.946 |
| Dental | |||
| U1-SN (°) | 0.09 | 0.64 | 0.994 |
| IMPA (°) | 0.15 | 0.52 | 0.995 |
| U1-L1 (°) | 0.21 | 0.70 | 0.996 |
| SN-FOP (°) | 0.03 | 0.63 | 0.992 |
| Overjet (mm) | 0.13 | 0.51 | 0.925 |
| Overbite (mm) | −0.09 | 0.43 | 0.984 |
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