The aim of this study is the histopathological evaluation of the efficiency of N-2-butyl cyanoacrylate in the fixation of bone block grafts on mandible. Autogenous monocortical block grafts taken from tibial bone were fixed to the outer surface of the angle of the mandible with N-2-butyl cyanoacrylate on the right side and mini screws on the left side. Postoperatively in the first and third months, six rabbits were killed and tissue samples were obtained from the grafted area. No significant difference was found between the cyanoacrylate and screw group with respect to inflammation or foreign body reaction. The level of graft necrosis was found to be significantly higher in the cyanoacrylate group than in the screw group in both the first and third month samples. Bone formation between the graft and recipient bone was evaluated and bone formation was found to be significantly higher in the screw group than in the cyanoacrylate group. No trabecular bone formation was observed between the graft and recipient bone in the cyanoacrylate group. Screw fixation was found to be superior to N-2-butyl cyanoacrylate in all parameters.
A variety of augmentation techniques can be used to provide sufficient bone volume for implant placement in the severely resorbed alveolar ridge, including guided bone regeneration, onlay grafting, combinations of onlay, veneer, interpositional inlay grafting, distraction osteogenesis, ridge splitting, free and vascularized autografts for discontinuity defects, mandibular interpositional grafting, and socket preservation . Bone block graft is the preferred method, since it secures a source of osteogenic cells and a rigid structure for mechanical support. Bone block graft conserves its volume better than particulate grafting .
Conventionally, titanium plates and screws have been used to achieve rigid fixation for onlay grafting. Despite the advantages of titanium screws, they have some potential drawbacks including the need for removal before implant placement, which may be difficult if bony overgrowth occurs, the risk of screw fracture during removal and radiographic artefact during imaging. Other problems associated with the use of titanium screws are patient discomfort due to palpability through the oral mucosa, bone atrophy or osteopenia caused by stress shielding and corrosion, allergic reactions, and the possibility of causing growth restriction of the craniofacial skeleton in paediatric patients .
Recent studies, have demonstrated the efficiency of tissue adhesive materials in soft and hard tissue fixation . Discovered in 1949, cyanoacrylate, has been proposed as a potential surgical adhesive . Multiple brands and formats of cyanoacrylate adhesives are available, and are widely used for corneal perforation repair, skin laceration repair, esophageal and gastric variceal repair, skin grafting, and vascular repair . Liquid cyanoacrylate consists of cyanoacrylate monomers, which polymerize into long chains in the presence of hydroxyl ions. Water containing human tissue activates the polymerization of cyanoacrylate monomers, and is bonded together as the glue rapidly sets. The property of nearly instantaneous bonding makes cyanoacrylates an effective hemostatic agent and tissue adhesive. Glubran 2 (GEM, Viareggio, Italy) is a new cyanoacrylate surgical glue composed of N-2-butyl cyanoacrylate (NBCA) and methacryloxysulfolane monomer. The longer radical chain has a lower polymerization temperature resulting in lower toxicity and fewer inflammatory reactions .
Cyanoacrylates have been described for use in cartilage–cartilage, cartilage–bone and bone–bone fixation since 1970s . Although there have been many studies on the adhesive properties of cyanoacrylates in bone–bone fixation, there has been only one study evaluating the remodelling process of onlay grafts fixed with cyanoacrylate. In a recent study, de O liveira N eto et al. analyzed the tomographic histological and immunohistochemical effects of NBCAs for onlay graft fixation and reported successful results in all parameters. The aim of this study was to evaluate whether NBCA glue fixation could provide a reasonable alternative to screw fixation in mandibular onlay grafting procedures.
Materials and methods
The animal experiment protocol was approved by the Ethical Committee of the University. 12 skeletally mature adult male New Zealand white rabbits (body weight 2.5–3 kg) were used in the study. The rabbits were kept in a dedicated animal holding facility in the laboratory animal unit and housed individually in stainless steel cages and fed with standard laboratory rabbit chow and water ad libitum . Postoperatively, the animals were given antibiotics (Cefozin ® , Bilim, Istanbul, Turkey) and analgesics (Temgesic ® 0.05 mg/kg, Reckitt and Colman, Wayne, NJ, USA) as single intramuscular injections for 3 consecutive days.
All animals were anesthetized with a combination of ketamine (Alfamine ® , 10 mg/ml, Alfasan Woerden, Holland) and xylazine (Alfazyne ® , 20 mg/ml, Alfasan Woerden, Holland). Cortical graft blocks measuring 3 mm × 3 mm × 2 mm were harvested from right tibial bone, using a surgical drill ( Fig. 1 A) . After bone block removal, the grafts were kept in sterilized gauze soaked in saline until final preparation of the recipient site. After the removal of the graft, the wound was sutured with resorbable 3–0 sutures (Vicryl, Ethicon, Norderstedt, Germany).
A split-mouth test design was followed in order to minimize the risk of inter-individual variations. In each animal, the buccal side of the mandibular body was used as the recipient bone. A skin incision was made along the inferior border of the mandible. Following elevation of the underlying tissues in layers, full-thickness buccal and lingual muscle-periosteal flaps were elevated. The bone surface was exposed and the recipient site was perforated ( Fig. 1 B). On the left side, the graft was fixed to the lateral aspect of the mandible with NBCA ( Fig. 1 C). On the right side, graft fixation was provided by a single titanium screw (diameter 1.5 mm × 8 mm; OsteoMed, TX, USA) ( Fig. 1 D). NBCA was applied to the graft surface and fixed to the prepared recipient bone surface on digital pressure application for 20 s. Before suturing, the stability was controlled by minimal force. After graft fixation was certain, the surgical site was primarily closed with 3.0 Vicryl suture. The animals were killed using a high dose of ketamine at the fourth and twelfth weeks postoperatively, and tissue samples were harvested from the grafted areas.
After death, tissue containing the recipient bed, the graft, and the overlying soft tissue was removed en bloc . Tissues were fixed in 10% buffered formalin for 2 days and decalcified in 2% paraformaldehyde/10% formic acid solution for 4 weeks. Tissues were dehydrated through ascending concentrations of ethyl alcohol, cleared with xylene, and embedded in paraffin. Serial 5 μm-thick coronal sections of the specimens were cut, and stained with haematoxylin-eosin (HE). Samples were evaluated by means of inflammation, foreign body reaction, graft necrosis and bone healing at graft-recipient bone junction. The authors’ classification was used during histopathologic examination. This graded inflammation as: 0, none; 1, low; 2, moderate; 3, extensive. Foreign body reaction (FBR) as: 0, no; 1, yes. Graft necrosis (GN) as: missing and/or pyknotic osteocytes seen in the total graft: 0, none; 1, 50%; 2, >50%. Graft-recipient bone interface (GRI) as: 0, no trabecular communicate; 1, trabecular communication.
Statistical analysis of the results was carried out with SPSS (Statistical Package for Social Sciences) for Windows 10.0. The Wilcoxon signed rank test was used to find possible differences between the two fixation method at weeks 4 and 12. Differences were considered significant at the p < 0.05 level.
The postoperative period was uneventful in both surgical sites of the mandible and the tibia. The graft was detached from the recipient bone only in one 4-week sample in the cyanoacrylate side due to the bone cutting procedure. This sample was excluded from the study. The distribution of samples with regard to inflammation, bone formation in GRI, GN and FBR are presented in Tables 1–4 , respectively. The evaluations of all samples according to the authors’ classification at weeks 4 and 12 weeks are presented in Table 5 .
|Inflammation||Week 4||Week 12|
|None||0||3 (50%)||1 (17%)||4 (67%)|
|Low||4 (75%)||2 (33%)||2 (33%)||2 (33%)|
|Extensive||1 (25%)||1 (17%)||1 (17%)||0|
|Graft-recipient bone interface||Week 4||Week 12|
|No trabecular comminication||5||1||6||0|
|Graft necrosis||Week 4||Week 12|
|Necrosis limited in some areas||3||2||2||1|
|Total necrosis of the graft||2||0||3||0|
|Foreign body reaction||Week 4||Week 12|