Radiological and Histological Evaluation of the Effects of Cortical Perforations on Bone Healing in Mandibular Onlay Graft Procedures

The allogeneic shell technique for alveolar ridge augmentation: a multicenter case series and experiences of more than 300 cases

PURPOSE

Allogeneic cortical bone plates (CP) might be used for alveolar ridge augmentation as an alternative to autogenous grafts (AG) and bone substitutes (BS). We report about a multicenter case series and our experiences of more than 300 cases using CP and the shell technique for reconstruction of the alveolar process to illustrate surgical key steps, variations, and complication management.

METHODS

Different types of alveolar ridge defects were augmented using the shell technique via CP. The space between the CP and the alveolar bone was filled with either autogenous or allogeneic granules (AUG, ALG) or a mixture of both. Implants were placed after 4-6 months. Microscopic and histological assessments were performed. In addition, space filling using AUG, ALG and bovine BS was discussed.

RESULTS

Scanning electron microscopy demonstrated the compact cortical structure of CP and the porous structure of ALG allowing micro-vessel ingrowth and bone remodeling. Histological assessment demonstrated sufficient bone remodeling and graft resorption after 4-6 months. In total, 372 CP cases and 656 implants were included to data analysis. The mean follow-up period was about 3.5 years. Four implants failed, while all implant failures were caused by peri-implantitis. Next, 30 CP complications were seen, while in 26 CP complications implant placement was possible. CP rehydration, stable positioning by adjusting screws, smoothing of sharp edges, and a tension-free wound closure were identified as relevant success factors. Space filling using ALG and a mixture of AUG/ALG resulted in sufficient bone remodeling, graft resorption and stability of the augmented bone.

CONCLUSIONS

CP and the shell technique is appropriate for alveolar ridge augmentation with adequate bone remodeling and low complication rates. Allografts can prevent donor site morbidity and therefore may decrease discomfort for the patient.

Maxillary vertical alveolar ridge augmentation using computer-guided sandwich osteotomy technique with simultaneous implant placement versus conventional technique: A pilot study

BACKGROUND

Sandwich osteotomy technique (Inlay bone grafting) is considered as a highly reliable procedure for vertical bone augmentation in the maxillary anterior esthetic zone. The aim of this study was to compare vertical bone gain and palatal tipping using computer-guided inlay technique versus the conventional technique.

MATERIAL AND METHODS

This was a randomized clinical trial including 12 patients who were randomly divided into two groups: sandwich osteotomy with simultaneous implant placement at the anterior maxillary esthetic zone (six patients) using patient-specific guides (PSGs) in the study group versus conventional technique (six patients). In the control group, free-hand sandwich osteotomy was done, while in the study group all the procedures were performed with two sequential PSGs with cutting slits, guiding holes, and implant sleeves. Radiographic assessment included measurements of linear changes in the vertical dimensions of the labial plate of bone and palatal tipping on cross-sectional cuts of cone-beam computed tomography using special software.

RESULTS

All the procedures were uneventful except one case of the study group showed a cracked bony segment that did not affect the final outcome. Radiographic results showed comparable bone gain in both groups with no statistical significance difference (study group 4.4 mm, control group 3.9 mm). To the contrary, the computer-guided approach significantly reduced the palatal tipping to 0.4 mm compared to 2.1 mm in the conventional group, and there was a statistically significant difference between the two groups (p-value <0.001).

CONCLUSION

Sandwich osteotomy using PSGs appears to be efficient and showed promising results regarding improving the palatal tipping compared to the free-hand technique.

The role of cortical perforations in allogeneic block grafting for lateral augmentation in maxilla: A randomized clinical trial

BACKGROUND

The need of decortication on the recipient site remains unclear for bone regeneration. To our knowledge, there are no human clinical trials that studied the influence of decortication on cancellous allogeneic block grafting.

PURPOSE

The aim of the present study is to evaluate the influence of perforating the cortex of the recipient site on cancellous allogeneic block graft integration and revascularization in the maxilla.

MATERIAL AND METHODS

Twenty-six patients referred for lateral bone augmentation were included in this clinical trial. Patients received freeze-dried bone allograft cancellous blocks obtained from the iliac crest; cortical perforations of the recipient bed were performed in the test group while in the control group it was left intact. After a 4-month healing period another surgery was performed to place dental implants, and a bone biopsy was collected using a trephine. All samples underwent micro-CT scans, and were processed for histomorphometric and immunohistochemical analysis. Implant survival comparisons were made using a repeated measures analysis of variance (ANOVA) while all other variables were compared using the analysis of covariance (ANCOVA).

RESULTS

One hundred and nineteen implants were placed into 110 augmented sites. One hundred percent implant survival rate was reported during 24 months follow-up period. No differences were reported in bleeding on probing at 1 (5.6 vs 9%) and 2 years (13.2 vs 12.1%), probing pocket depth at 1 (3.4 ± 0.95 vs 3.6 ± 1.12 mm) and 2 years (3.8 ± 1.02 vs 4.1 ± 1.46 mm), and marginal bone loss at 1 (0.2 ± 0.52 vs 0.3 ± 0.57 mm) and 2 years (0.6 ± 0.91 vs 0.5 ± 0.87 mm). No statistically significant differences were found in the micro-CT and histomorphometric analysis in terms of newly formed bone (25.7 ± 11.2% vs 22.3 ± 9.7%), soft tissue (33.0 ± 14.7% vs 36.5 ± 15.7%), remnant allograft (39.3 ± 20.4% vs 41.2 ± 22.7%), and bone mineralization (57.2 ± 10.6% vs 53.8 ± 8.7%). Perforating the cortex of the recipient site had no significant effect on angiogenesis as shown by immunohistochemical analysis of CD34 positive blood vessels (39.21 ± 10.53/mm² vs 34.16 ± 12.67/mm² ).

CONCLUSION

Cancellous allogeneic bone block grafts are a clinically acceptable alternative for horizontal bone augmentation. Cortical perforations of the recipient site in the maxilla did not improve angiogenesis nor bone formation within the block graft.

Maxillary horizontal alveolar ridge augmentation using computer guided ridge splitting with simultaneous implant placement versus conventional technique: A randomized clinical trial

BACKGROUND

Ridge splitting technique is considered one of the successful horizontal bone augmentation procedures especially for the maxillary bone, the aim of this study was to compare marginal bone loss using a novel ridge splitting protocol versus the conventional technique.

MATERIAL & METHODS

This was a randomized clinical trial including 20 patients who were randomly assigned to ridge splitting with simultaneous implant placement at the anterior maxillary aesthetic zone (10 patients, 29 dental implant) using patient specific guides (PSGs) or conventional technique (10 patients, 29 dental implant). In the control group free hand ridge splitting was done, while in the study group all the splitting and drilling procedures were done through specific slits and sleeves at the patient specific guides. Radiographic Assessment included measurements of linear changes in the vertical dimensions of the labial plate of bone on cross sectional cuts of computed tomography (CBCT) using mimics software.

RESULTS

Wound healing was uneventful for all the patients except one patient in the control group that showed bad split and another showed buccal fenestration. The study group showed lower bone loss (1.38 ± 0.61 mm) compared to the control group (2.42 ± 0.63 mm), with statistical significance difference (P value = 0.001). The loss percentage also was higher in the study group (10.99 ± 4.76%) compared to the control group (19.12 ± 4.53%), and there was statistical significance difference between the two groups (P value = 0.001).

CONCLUSION

Ridge splitting using PSGs appear to be efficient and promising than the free hand technique.

Bone demineralization improves onlay graft consolidation: A histological study in rat calvaria

BACKGROUND

Previous data suggest that bone demineralization may promote bone graft consolidation as well as proliferation and differentiation of pre-osteoblasts, but the biological mechanisms involved in this process need to be clarified. This study investigated the effects of bone demineralization with citric acid (CA) and tetracycline (TCN) on the repair of onlay bone grafts.

METHODS

Onlay bone grafts were performed on the calvaria of 126 Wistar rats. The contacting surfaces between bone graft and receptor bone bed were demineralized for 15, 30, and 60 seconds with TCN (50 mg/mL), or 10% CA, (pH 1), constituting the following test groups (n = 18): TCN15, TCN30, TCN60, CA15, CA30, and CA60. Control grafts (C) were performed without demineralization (n = 18). After 7, 30, and 60 days, biopsies were obtained for quantitative and qualitative histological analysis (a = 6).

RESULTS

Demineralization accelerated the bone repair early from 7 days of healing. Higher percentage area of newly formed bone was observed in CA15 and TCN60 groups when compared to C in all evaluation periods (P = 0.02). At 30 days, C specimens had lower percentage of consolidated surfaces than TCN60, TCN30 and CA15 (P = 0.0015). At 60 days, CA15, CA60, and TCN60 presented bone surfaces almost completely filled by newly formed bone, against about 75% in C specimens (P = 0.0015).

CONCLUSIONS

Both CA and TCN were effective in accelerating osteogenesis at the interface between bone grafts and receptor bone beds, especially when applied for 15 seconds and 60 seconds, respectively.

Healing at the interface between recipient sites and autologous block bone grafts affixed by either position or lag screw methods: a histomorphometric study in rabbits

OBJECTIVE

To compare the sequential healing at the interface gap occurring between autologous bone grafts and recipient sites using two types of fixation techniques.

MATERIAL AND METHODS

Twenty-four adult male New Zealand white rabbits were used. Two bone grafts were collected from the calvaria and secured to the lateral aspect of the angle of mandible in each animal. Cortical perforations at the recipient sites were performed. However, no modifications were applied to the graft for its adaptation to the recipient site. Two types of fixation techniques by position or lag screws were applied. This was done by preparing osteotomy holes smaller or larger than the screw diameter, respectively. The animals were sacrificed after 3, 7, 20, and 40 days.

RESULTS

After 3 days, the distance between the graft and the recipient site was similar between the two different fixations. Due to the anatomical shapes of the recipient sites and grafts, the distance between the two parts was lower in the central region (<0.1 mm) compared to the external regions of the graft (0.5-0.6 mm). The first evidence of small amounts of new (woven) bone was seen after 7 days, forming from the parent bone. The percentage increased after 20 and 40 days. After 40 days, the grafts were well incorporated within the recipient sites in both groups without any statistically significant difference.

CONCLUSIONS

The present study did not show superiority of one method over another. A fixation to a recipient site with perforations may be sufficient for incorporating an autologous bone graft even if its adaptation is not perfect and irrespectively of the fixation method. Distances of approximately half millimeter were bridged with newly formed bone.