Lambros Kostopoulos

Bone and suture regeneration in calvarial defects by e-PTFE-membranes and demineralized bone matrix and the impact on calvarial growth: An experimental study in the rat

The aim of this study was to evaluate the effect of: guided tissue regeneration (GTR) alone, implantation of demineralized bone matrix (DBM) alone, and of the combined treatment on the healing of craniectomy defects involving the sagittal cranial suture, and to examine subsequent calvarial growth. Sixty four-week-old rats were used in the study. These animals were randomly assigned to five groups (A-E) of 12 animals. In four groups (A-D), a calvarial defect (5.0 mm) involving the sagittal suture was produced in each animal. Group A: The defect was left untreated. Group B: DBM was implanted into the defect. Group C: The cerebral and the galeal aspect of the defect was covered with an e-PTFE membrane. Group D: The defect was treated with the double membrane technique combined with implantation of DBM. Group E: The animals were sham-operated, no defect was created. In all groups, two gutta-percha points were placed to indicate the lateral borders of the parietal bones. Histological analysis 4 months following surgery showed that the untreated cranial defects (A) had healed with fibrous connective tissue in the midportion of the defect. The DBM grafted defects (B) healed either completely with bone containing DBM particles or partially with bone and connective tissue. The defects (D) treated with DBM combined with GTR healed completely with bone, while the defects (C) treated with membranes alone healed with bone but a suture-like tissue similar to the normal sagittal suture of the sham-operated controls (E) was always present in the midportion of the defect. Cephalometric radiography demonstrated that the membrane-treated (C) and the sham-operated animals (E) exhibited similar coronal growth of the cranial vault following treatment. Craniometric measurements on chemically defleshed specimens showed that sham-operated and membrane-treated animals presented significantly more biparietal width than the animals treated with DBM alone or DBM combined with GTR (P < 0.05). The results demonstrated that predictable osseous healing including the formation of a sagittal suture can be accomplished in craniectomy defects by GTR, and undisturbed cranial growth reestablished. The treatment of the defects with DBM alone or DBM combined with GTR resulted in craniosynostosis and reduced cranial growth.

Healing of Osseous Submucous Cleft Palates with Guided Bone Regeneration

The aim of this study was to develop an experimental model in rats of an osseous submucous cleft palate and to examine if bone regeneration can be achieved in such defects by the placement of membranes according to the principle of guided tissue regeneration (GTR). An osseous submucous cleft palate defect (5 mm x 2 mm) was created surgically in Wistar rats. Membranes of expanded polytetrafluoroethylene were placed so that they covered both the nasal and the palatal aspect of the defect before the palatal mucoperiosteal flap was repositioned and sutured. Histological analysis after seven weeks of healing showed that significantly more test animals (5/9) healed with newly formed bone and a suture-like tissue in the middle of the defects than controls treated without membranes (0/17). In specimens evaluated macroscopically after 12 weeks, the corresponding rates for the test group were 12/12 compared with 0/13. These observations indicate that an experimental model of an osseous submucous cleft palate can be established in rats, and that complete osseous healing and creation of a midpalatal suture-like tissue in the bony defect is favoured by the placement of membranes according to the principle of GTR.

Immediate implant placement in molar regions: risk factors for early failure

OBJECTIVES To identify risk factors for early failure of immediately placed implants in molar regions associated with three bone regenerative techniques. METHODS Ninety-two patients (44 women and 48 men; mean age 50 years, 35 smokers and 57 non-smokers) in need of a single implant crown to replace a molar were included. After placing the implant, patients were randomized to one of three treatment groups for bone reconstruction of remaining periimplant defects: Autologous bone (AB) chips, Ossix membrane (OM) or a combination of AB chips and OM. The implant was submerged, and after 4 months of healing a re-entry surgery was made to connect a healing abutment. Implants with a dehiscence on ≥2 sites (mesial/distal/oral/buccal) together with ≥50% visible threads, were judged as failures. A series of simple logistic regression analyses were performed to identify risk factors for failure among the following independent variables: sex, jaw, smoking status, plaque, bleeding on probing, fistula, extraction reason, mean initial periimplant defect size, treatment group, implant length, buccal bone dehiscence (BBD), soft-tissue dehiscence and infection. The identified risk factors entered a multiple logistic regression analysis. RESULTS Fifteen implants failed before abutment operation (13 explantations/two non-osseointegrated). Treatment group had no impact on failure. Risk factors for failure were: Smoking >10 cigarettes/day (odds ratio [OR]=9.29, confidence interval [CI]=1.21-71.16), BBD (OR=11.43, CI=1.34-97.74) and infection (OR=36.7, CI=2.75-489.31). CONCLUSIONS Implants placed immediately after extraction of a molar were associated with a high risk for failure at abutment operation. There was no difference in failure rate between three bone reconstructive techniques.

The use of human hypertrophic chondrocytes-derived extracellular matrix for the treatment of critical-size calvarial defects

OBJECTIVES To evaluate the effect of immortalized hypertrophic chondrocytes extracellular matrix (HCM) with or without the use of guided bone regeneration (GBR) on the healing of critical-size calvarial defects. MATERIAL AND METHODS In 42 rats, 5 mm critical-size calvarial defects were surgically created. The animals were randomly allocated to six groups of seven rats each: Group A1: one defect was left untreated (control), while the contralateral defect was covered by a double non-resorbable membrane (GBR). Group B1: one defect was filled with calcium phosphate cement (CP), while the contralateral defect was treated with GBR and CP. Group C1: one defect was filled with a mixture of CP and HCM, while the contralateral defect was treated with GBR and CP+HCM. The healing period for all three groups was 30 days. The remaining three groups were treated in a similar manner but the healing period was 60 days. Five animals from each group were evaluated by maceration and two animals were analysed histologically. RESULTS At 30 days, all the control-treated defects did not present complete closure. When GBR was applied alone or combined with CP, 3/5 and 5/5 defects, respectively, presented complete closure. At 60 days, one defect from the control group presented complete closure. All the defects treated with GBR alone presented complete closure, whereas the combined use of GBR with CP or CP+HCM resulted in 4/5 and 3/5 defects with complete closure, respectively. The only treatment modality that did not present any specimen with defect closure at both 30 and 60 days was the combination of CP+HCM. The histological analysis indicated that when GBR was not used alone, the healing consisted of an amorphous acellular structure and loose granulation tissue, which, even though clinically resembled hard tissue, did not demonstrate the histological characteristics of bone. CONCLUSION The predictability of bone formation in critical-size defects depends mainly on the presence or absence of barrier membranes. The combined use of GBR with calcium phosphate alone or in combination with immortalized human HCM did not enhance the potential for osseous healing provided by the GBR procedure.

Immediate implant placement in molar regions: a 12-month prospective, randomized follow-up study

OBJECTIVES To evaluate marginal bone changes radiographically and clinically around immediately placed implants in molar regions associated with three bone regenerative techniques 12 months after loading. METHODS Ninety-two patients received an implant after random allocation to a bone reconstruction method of remaining peri-implant bone defects using either Autologous bone (AB) chips, Ossix membrane (OM) or a combinations of AB chips and OM. After 4 months of healing, a re-entry surgery was performed to connect a healing abutment. A screw-retained crown was mounted 4-6 weeks afterwards. Seventy-six patients attended a follow-up visit 12 months after loading. Marginal bone level was assessed radiographically before re-entry surgery and at the 12-month follow-up; probing pocket depth (PPD) and probing defect depth (PDD) at the implant platform level without the mounted crown were assessed after and just before crown delivery respectively and at the 12-month follow-up. RESULTS Fifteen implants were judged as failures at re-entry surgery, and one patient died before follow-up. A statistically significant bone loss was seen in the three groups after 12 months (average 0.48 mm), but no significant differences were found among the groups. Likewise, no differences in PPD or PDD could be found between the groups. An average bone loss of 0.48 mm was recorded at the 12-month follow-up examination resulting in an average peri-implant bone level of approximately 1.1 mm related to an average PPD of 3.1 mm and an average PDD of 1.3 mm. CONCLUSIONS After 12 months of loading, no significant differences in peri-implant bone level were observed after the use of three bone regenerative techniques in connection with immediately placed implants in molar regions.

Tirilazad inhibits surgically induced edema and interleukin-1 production: An experimental study in rats

The aim of this study was to evaluate the anti-inflammatory effect of tirilazad mesylate on edema and interleukin-1 (IL-1) levels in serum following standardized surgical procedures. Four groups, each containing eight rats, were randomized for treatment as follows: A) no medication, B) low-dose tirilazad, C) high-dose tirilazad, and D) corticosteroids. The animals were examined by nuclear magnetic resonance imaging (NMRI) 24 and 72 hours after surgery and the NMRI data were used in the determination of soft tissue edema. In addition, serum was obtained for analysis of IL-1 levels. Four other groups of animals were subjected to the same treatment regimen as groups A-D), respectively, and 24 hours after surgery the animals were killed, whereafter serum was obtained for analysis of IL-1 levels. The present study demonstrated that low-dose tirilazad significantly reduces soft tissue edema compared with all other treatment regimens 24 hours postoperatively. At 72 hours postoperatively significant reduction of soft tissue edema was achieved at low-dose tirilazad when compared to high-dose tirilazad and steroids. In addition, a significant suppression of the expression of IL-1 was observed at 24 and 72 hours when comparing low-dose tirilazad and the control group.