In this study, the height of the interdental bone septum in the mesial teeth and distal teeth of the alveolar cleft were compared and evaluated through the radiographs taken immediately after surgery, 6 months after surgery, and 1 year after surgery [11, 19]. This method has been used in several studies to evaluate the results of alveolar bone grafting [21–23]. In this study, if more than 50 % of the graft bones remained 1 year after surgery, we considered it a successful alveolar bone graft. As a result, the success rate of the intramembranous bone graft was 91.67 % and that of the endochondral bone graft was 83.33 %. In comparison with other studies that reported a success rate of 80 to 90 %, both groups showed a similar result .
Although not statistically significant, the success rate of intramembranous bone was higher than that of the endochondral bone. Grafted bones were exposed in three patients after surgery. Two patients underwent the iliac crest bone graft, and one patient received the chin bone graft. Severe reduction of the graft bone was observed until type III or type IV in all patients. If the size of the cleft site is large, the excessive tension causes the failure of the primary closure, especially in the palatal side. That is, the size of the alveolar cleft rather than the type of the grafting bone was seen as having a greater effect on the result of the surgery [22, 24].
The interdental bone septum height tended to decrease in the intramembranous bone more than the endochondral bone at 6 months after surgery; however, the endochondral bone decreased more than the intramembranous bone at 1 year after surgery. The mean resorption rate of the area of the grafted bone also tended to decrease in the intramembranous bone more than the endochondral bone at 6 months after surgery. That is, initially, the intramembranous bone is absorbed more rapidly; however, the intramembranous bone is more stable than the endochondral bone in the long-term follow-up. In this regard, one of the most important factors that can affect the outcome of a bone graft is its revascularization. When the graft becomes newly vascularized, nutrients, gas, and undifferentiated mesenchymal cells are transported into the defect and bone regeneration is promoted [25, 26].
In several previous studies, the endochondral bone grafts were more rapidly revascularized than the intramembranous bone grafts in animal models [18, 27]. This would explain the result of the initially greater volume maintenance of the endochondral bone grafts. However, after revascularization, it is considered that that the volume of intramembranous bone is maintained better than that of the endochondral bone due to the differences of micro-architecture of the mineralized matrix of bone .
The ilium which can be harvested in large quantities at a time, and is easy to work with due to both the cortical and cancellous bone, is the most popular; however, it has problems such as the gait disturbance and formation of scar tissue around the mouth [28–30]. Some surgeons used the calvarial bone of the intramembranous bone rather than the ilium of the endochondral bone, because of the similarity of the bones’ histology and development . In addition, the autogenous bone harvested from the mandibular ramal or chin area can be used for bone grafting . The mandibular bone has a good result compared to iliac surgery, and it has the advantage of a shorter operative time and hospital stay, as well as no extraoral scar formation . But, if a great amount of grafting bone is required, the mandibular bone cannot be used because only a small amount can be collected. In this study, we used the mandibular bone and not the calvarial bone, and all patients with bilateral cleft received the iliac bone graft.
In this study, the heights of the interdental bone septum were measured 6 months and 1 year after surgery. Other studies have shown that absorption of graft bone occurs mainly during the first 6 months, and there are no significant changes of the bone between 6 months and 1 year following surgery . Therefore, the follow-up period of 1 year is sufficient to test this result. But the limitations of this study were that it has a small number of samples and the width of the bone could not be assessed using radiographic images.