Abstract
The aim of this study was to evaluate the osseointegration of three different bone grafting techniques. Forty-eight mature New Zealand rabbits were divided randomly into three groups of 16 each. Horizontal augmentation was performed on the corpus of the mandible using three different techniques: free bone graft (FBG), free periosteal bone graft (PBG), pedicled bone flap (BF). The animals were sacrificed at postoperative weeks 1, 3, or 8. Specimens were decalcified for histological examination, and histomorphometric measurements were performed. The histological evaluation demonstrated bony fusion between the grafts and the augmented mandibular bone after 8 weeks in all groups. At week 8, the bone volume was significantly greater in the BF group than in the FBG ( P < 0.001) and PBG ( P = 0.001) groups, and also the trabecular thickness was significantly greater than in the FBG ( P = 0.015) and PBG ( P = 0.015) groups. Trabecular separation was significantly lower in the BF group than in the FBG group at week 8 ( P = 0.015). BF demonstrated greater osseous healing capacity compared to FBG and PBG. The preserved vascularization in BF improves the bone quality in mandibular bone augmentations.
Bone grafting and alveolar bone augmentation facilitate dental implantology in patients with atrophic alveolar bone, such as grades IV–VI of the Cawood and Howell classification . A variety of augmentation procedures have been described. Chiapasco et al. described five methods to augment the local bone volume at deficient sites: (1) osteoinduction by the use of appropriate growth factors ; (2) osteoconduction where a grafting material serves as a scaffold for new bone formation ; (3) distraction osteogenesis (DO) ; (4) guided bone regeneration (GBR) ; and (5) vascularized bone flaps .
Bone grafting can be performed with autogenous bone or with bone substitutes. The bone graft should ideally deliver osteoinductive and osteoconductive properties. In this study it was focused on autogenous bone grafts, which incorporate the two aforementioned qualities. Autogenous bone grafts can be harvested intraorally from the mandibular symphysis, ascending ramus/body, coronoid process, and the zygomatic-maxillary buttress .
Bone blocks are frequently harvested for horizontal or vertical augmentation of the alveolar ridge. The periosteal layer is usually pushed aside while harvesting the bone graft. Hence, a free bone graft without overlying periosteum is harvested. However, the periosteum plays a crucial role in ‘intermembranous ossification. It is divided into two layers: the inner cambium layer and the outer fibrous layer. The cambium layer contains osteoprogenitor cells, which have osteogenic potential . Many experimental studies have reported that bone generation is induced by transplanted free-periosteum in the closed space . In addition, clinical studies have shown that in children, free-periosteum grafting to the palatal clefts and alveolar clefts produces new bone formation in the bone defects .
The question has thus been raised whether the osseous healing capacity of bone grafts can be enhanced by leaving the covering periosteal layer intact, i.e., will a free periosteal bone graft demonstrate better healing capacity and an improved osseointegration than a free bone graft? Furthermore, it may be interesting to compare the osseous integration of free bone grafts with the healing capacities of pedicled bone flaps. In the sandwich osteoplasty, the alveolar bone remains lingually attached to the adjacent soft tissues . Hence, the pedicled bone flap stays attached to its surrounding soft tissues and its vascularity remains almost undisturbed. The same principle may hold true for alveolar bone spreading or splitting techniques.
The objective of this animal study was to determine whether there is a significant difference in osseous healing between free bone grafts with or without the overlying periosteum and pedicled bone flaps.
Materials and methods
Forty-eight skeletally mature male New Zealand rabbits weighing 2.8–3.2 kg (mean ± standard deviation (SD) 3.05 ± 0.15 kg) were used in this study. The animals were divided randomly into three groups of 16. The local animal ethics committee approved this study.
Surgical procedure
General anaesthesia was obtained by intramuscular (i.m.) injection of 35 mg/kg ketamine (Ketalar; Pfizer, Istanbul, Turkey) and 3 mg/kg xylazine (Rompun; Bayer, Istanbul, Turkey). After placing the animal in a supine position, the submandibular region was prepared and draped under aseptic conditions. Two millilitres of articaine with 1:200,000 epinephrine (Ultracaine-DS; Hoechst Marion Roussel, Istanbul, Turkey) was administered supraperiosteally to provide anaesthesia and haemostasis. The mandibular corpus was exposed unilaterally through a submandibular incision. Horizontal augmentation was performed at the base of the mandibular corpus using three different techniques. All grafts used for horizontal augmentation were of the same dimensions (3 × 0.5 × 3 cm).
In the first group, free bone grafts (FBG) were harvested from the angle of the mandible and fixed to the mandible for horizontal augmentation ( Fig. 1 A) . In the second group, free periosteal bone grafts (PBG) were harvested from the angle of the mandible. The overlying periosteal layer remained attached to the bone graft ( Fig. 1 B). In the third group, the bone was harvested from the mandibular angle leaving the overlying periosteum and the muscle attached. The bone remained attached to the masseter muscle. After mobilization of the pedicled bone flap (BF), it was rotated anteriorly to augment the corpus of the mandible ( Fig. 1 C). In all groups, the grafts were fixed to the mandibular corpus with 1.5-mm titanium microscrews (Trimed; Aksu Medikal, Adana, Turkey). The soft tissue was closed in layers with resorbable sutures (Vicryl; Ethicon, Brussels, Belgium). At the end of the operation, the animals were given 100 ml dextrose solution (5%) via an orogastric tube to replace the fluid loss and to support the postoperative nourishment.
