Secondary alveoloplasty with autogenous bone graft is the most commonly procedure used to reconstruct alveolar clefts [15]. Despite the resorption rates and post-operative morbidity, the iliac crest bone is the most used as a grafting material [7, 8], thus being the donor site preferred by the majority of the cleft treatment centres [16]. Nevertheless, the results presented in our study demonstrated that mandibular symphysis bone graft, when used to reconstruct alveolar clefts in patients aged between 7 and 12 years old, has a behavior similar to that of the iliac crest one.
Extraction of bone grafting material from the mandibular symphysis is described as being more advantageous than the iliac crest because of lower morbidity rate, shorter hospitalization and absence of skin scar [17], in addition to better bone incorporation as both mandible and maxilla have the same ectomesenchymal origin and intra-membranous ossification process [6]. Mandibular symphysis has a lower amount of bone available for grafting [6, 7, 17, 18], but it is a donor site near the operative field, which reduces the surgery and anaesthesia times [17].
Data on post-operative complications in the donor graft sites were not collected in the present study. Possible complications associated with the extraction of bone graft from the mandibular symphysis are lower lip ptosis, lesion in teeth adjacent to the donor site and lesion to the mentual nerve. On the other hand, extraction of bone graft from the iliac crest results necessarily in skin scar and the patients may also complain of post-operative pain, difficulty in walking [17, 19], sensorial loss, seroma, haematoma, fracture, abdominal herniation, contour defects, peritoneal perforation and keloids [8, 20].
Previous studies have determined that the age of 9–12 years old, i.e. before eruption of the canines, is the most suitable moment for performing alveolar grafting [14, 17, 21, 22]. Although our results were positive for patients with similar age (7–12 years old), Dissaux et al. [23] performed a tomographic analysis to show that alveolar bone grafts are successful when children are surgically treated earlier (i.e. around 5 years old) compared to those aged around 10 years old. Therefore, the upper lateral incisors can erupt through the grafted bone, which ensures better results in terms of residual bone height.
The results demonstrated that bone grafts from iliac crest and mandibular symphysis interfered with the upper canine eruption at the same frequency, that is, 19.6% in both groups of patients. These values were close to those reported by Sindet-Pedersen and Enemark [17], who found 15% and 20% of impacted upper canines in patients submitted to mandibular symphysis and iliac crest grafts, respectively. Sindet-Pedersen and Enemark [22] studied a sample of 28 patients with mandibular symphysis grafts and showed that all patients had the canines erupted in the grafted area, but they did not describe whether the teeth were surgically exposed or orthodontically pulled. Desai et al. [24] evaluated the eruption stage and changes in the position and pattern of canine eruption after alveolar graft from iliac crest in 30 patients aged between 9 and 13 years old. The authors found that the canine did not erupt in only 20% of the cases, demonstrating that eruption was satisfactory and the root grew continuously in the region of the grafted alveolar cleft. The risk of impacted canines is increased if they are unfavourably, either vertically or laterally, positioned before the surgery as they erupt continuously in the same graft angle.
The literature has long been evaluating the resorption of autologous bone grafts in alveolar clefts. Sindet-Pedersen and Enemark [25] compared radiographically the results of alveoloplasty with iliac crest grafting performed in patients before and after the eruption of upper canine. The authors used an approach similar to that in our study, but they divided the grafted area into quarters rather than into thirds. Of the patients with the age group and cleft classification similar to ours, they found 89.4% of type I, 9.67% of type II and 1.07 of type III. Despite the change in the classification, the results are compatible to those found at T1.
Bergland et al. [14] evaluated periapical radiographs of patients submitted to iliac crest grafting after at least 12 months from the surgery. Of the 143 patients aged 8–11 years old who underwent grafting before eruption of the canine in the area of cleft, 96% of the cases were successful, which is a result similar to ours. Enemark et al. [21] repeated the methodology used in the study by Sindet-Pedersen and Enemark [25], but with a 7-year follow-up. Among the 95 patients with cleft classification and age similar to those of our study, 71.57% were classified as type I, 23.15% as type II, 4.2% as type III and 1.05 as type IV. Likewise, despite the different cleft classification, it should be noted that their result was worse than ours at T2. Sindet-Pedersen and Enemark [22] evaluated the radiographs of unilateral patients aged 8–15 years old for 8 months, on average, after mandibular symphysis bone grafting. Bergland scale was used and all 28 patients had their cleft categorised as type I (26 patients) or type II (2 patients). Sindet-Pedersen and Enemark [17] compared the radiographic images of unilateral cleft patients who were submitted to alveolar reconstruction. Twenty patients received the iliac crest bone graft and 20 received mandibular symphysis bone graft. The age of the patients ranged from 8 to 13 years old and the follow-up period lasted 19 months, on average. The alveolar clefts on the radiographs were classified in the same way as earlier and the authors found no significant difference in the bone height between both treatments, showing results similar to ours. One factor making it difficult to compare both groups of patients relies on the fact that the maxillary transverse discrepancies in patients with mandibular symphysis bone graft were not corrected prior to the surgery, differently from those patients with iliac crest bone graft. Such heterogeneity did not occur in our sample, thus making our assessment more reliable.
Trujillo et al. [12] used CBCT to compare the bone formation in cleft patients with mean age of 10 years old submitted to alveolar bone grafting using recombinant human bone morphogenetic protein-2 (rhBMP-2) and autogenous grafts obtained from iliac crest and mandibular symphysis. The higher mean amount of bone neoformation was achieved in patients with iliac crest bone graft (85.4%), followed by those with rhBMP-2 (81.22%) and with mandibular symphysis bone graft (80.56%). However, there was no statistically significant difference, which corroborates our findings. Lundberg et al. [26] used the Bergland scale to assess the results of the alveolar bone grafting with iliac crest bone graft in 91 patients with mean age of 9.2 years old after seven years from the surgery. The authors found a high rate of success (91%) and reported that a poor oral hygiene increased significantly the risk of surgical failure. This suggests that perioperative measures to maintain a good oral health can reduce such risk.
The rates of success found in the present study are compatible to the literature. However, it is difficult to compare it with other studies because of the different classification criteria used and differences in previous treatments before the grafting procedure. Notably, the majority of the cleft lip and palate centers perform alveoloplasty with bone from the iliac crest instead of mandibular symphysis [7, 16]. Nevertheless, the mandibular symphysis was shown to be a viable source of graft as the long-term results are compatible with those using iliac crest bones, in addition to the lower rates of complication [17, 19, 20]. Therefore, among the two options presented here, the choice of the graft donor site should be made on the basis of the necessary and available amount of bone.
Grafting procedures using bones from iliac crest and mandibular symphysis were considered to be viable when used for reconstruction of alveolar clefts in patients aged between 7 and 12 years old, since there were no statistically significant differences in the bone formation.