Experimental study on mandibular bone regeneration with different biomaterials in rats B. Peral, L. M. Redondo, A. Verrier, A. Serrat, M. A. Torres, C. Vaquero

Revista Española de Cirugía Oral y Maxilofacial 2008: 30: 313–323 The aim of this experimental study was to evaluate bone regeneration using different types of biomaterials in rats. Twenty-four white male adult Wistar rats aged 3–4 months were divided into four groups. Once the rats were anaesthetized using intraperitoneal ketamine and local infiltration with articaine, a submandibular approach was used to expose the mandible angle and ramus. A critical circular bone defect of 4 mm diameter was performed bilaterally in the mandible. The rats were divided equally into four groups: Group I (Control) – a defect was left uncovered; in Group II – both vestibular and lingual sides of a defect were covered with a resorbable demineralized bone membrane (Lambone ^® ); Group III – a defect was filled with freeze-dried collagen (Collos ^® ) and also covered with the same membrane (as in Group II); Group IV – a defect was filled with bioactive glass (Nova Bone ^® ) and covered by Lambone membrane.

A total of 48 specimens were obtained by block excision of each mandible, half of them at 3 weeks of the postoperative period and the others at 6 weeks. Each specimen underwent macroscopic, radiological and histological examination. SPSS for Windows was used for statistical analysis. The level of statistical significance was set at 5%. Two specimens were excluded from the study due to abscess and mandibular fracture.

Macroscopic results showed lack of bone formation in the Control Group with soft tissue occupied the defect. No displacement of the membranes was observed in the experimental groups. Radiological results showed circular radiolucent defects in the majority of cases in the Control Group. In Group II specimens, low intensity of radio-opacity was observed at 3 weeks while radio-opacity increased at 6 weeks with evident signs of centripetal bone repair. Group III specimens showed homogeneous radio-opacity in the centre of the defects at 3 weeks with practically complete radiological repair at 6 weeks in 80–100% of cases. In most Group IV specimens, heterogeneous radio-opacity with granular appearance was visible at 3 weeks at 6 weeks. Bone densitometry showed statistically significant differences ( p < 0.001) at 6 weeks in all groups with respect to the Control Group. Group IV (Membrane + Collos ^® ) achieved the highest mean densitometric value (4.89).

Histological results showed no ossification in Group I. Centripetal bone regeneration accounting for 30% of the defect at 3 weeks until 50% at 6 weeks was observed in Group II. Extensive repair with immature cancellous bone up to about two-thirds of the defect was observed at 3 weeks in Group III specimens, while complete ossification of the defect was noted in all cases at 6 weeks. No bone formation was observed in Group IV animals, neither at 3 nor 6 weeks. Intense foreign body inflammatory cells were found in all specimens of this group. Quantitative histological results showed a significant statistical difference regarding bone maturity, bone marrow and peripheral formation of bone in Group III while compared to Groups I, II and IV ( p < 0.001).

In the authors’ opinion, the association of resorbable membrane and freeze-dried collagen enhances bone regeneration in critical size defects. Radio-opacity per se should not be used as the only criterion for evaluating bone regeneration.

JULIO ACERO