Effects of Marrow Penetration on Bone Augmentation Within a Titanium Cap in Rabbit Calvarium

Effects of Minocycline Hydrochloride as an Adjuvant Therapy for a Guided Bone Augmentation Procedure in The Rat Calvarium

This in vivo study reports the influence of minocycline-HCl administration on extra-skeletal bone generation in a Guided Bone Augmentation model, utilizing titanium caps placed on the intact as well as perforated calvaria of rats. The test group was administered 0.5 mg/mL minocycline-HCl with the drinking water, and the amount of bone tissue in the caps was quantified at three time points (4, 8 and 16 weeks). A continuously increased tissue fill was observed in all groups over time. The administration of minocycline-HCl as well as perforation of the calvaria increased this effect, especially with regard to mineralization. The strongest tissue augmentation, with 1.8 times that of the untreated control group, and, at the same time, the most mineralized tissue (2.3× over untreated control), was produced in the combination of both treatments, indicating that systemic administration of minocycline-HCl has an accelerating and enhancing effect on vertical bone augmentation.

Use of Melatonin/Decorticotomy and Autogenous Bone Graft in Induced 1-Wall Defect

PURPOSE

This study was designed to investigate the effect of intramarrow penetration (IMP) and 1% melatonin (MLN) gel on the remodelling process of autogenous bone graft (ABG) in an induced 1-osseous wall defect model.

METHODS

Sixty-four intrabony induced mandibular defects were created on the distal side of premolars-P1, P2, P3, and P4 (on each side)-in 8 beagle dogs. A ligature-induced periodontitis was initiated in each defect. Defects were then divided into 4 equal groups. Group I was treated with open-flap debridement (OFD) alone, group II was treated with OFD/ABG, group III was treated with OFD/IMP/ABG, and group IV was treated with OFD/ABG/IMP/1% MLN gel. The study parameters were bone fill, histologic analysis, and immunohistochemical evaluation of endothelial nitric oxide synthase (eNOS) expression at 2-week (2W) and 8-week (8W) time intervals.

RESULTS

At 8W, significant differences were revealed amongst all groups regarding the amount of bone fill and eNOS expressions (P < .001). Bone fill percentages were 55.5%, 22.3%, 16.8%, and 0% in groups IV, III, II, and I, respectively. eNOS expressions were 1.68 ± 0.06, 8.43 ± 0.04, 16.80 ± 0.17, and 1.97 ± 0.07 in groups IV, III, II, and I, respectively. The favourable results were in line with group IV.

CONCLUSIONS

According to these preliminary results, defects treated by ABG augmented with IMP and 1% MLN gel revealed a greater amount of bone fill and reduced eNOS expression. This combination is therefore highly suggested as an adjunct to ABG.

Comparison of Macro-and Micro-porosity of a Titanium Mesh for Guided Bone Regeneration: An In Vivo Experimental Study

BACKGROUND/AIM

Guided bone regeneration (GBR) is one of the surgical methods used for vertical ridge augmentation prior to dental implant placements. Titanium meshes have been used for osteogenic space maintenance in GBR sites by clinicians. We aimed to compare the influence of micropores and macropores in a titanium mesh on bone regeneration in a rat calvarial vertical GBR model.

MATERIALS AND METHODS

The calvaria of nine rats were exposed, and plastic cylinders were set bilaterally. Eighteen surgical sites were randomly allocated into three groups according to the materials of titanium lid and bone substitutes: microporous titanium lid+deproteinized bovine bone mineral (DBBM), macroporous titanium lid +DBBM, microporous titanium lid+carbonate apatite. Newly generated bone inside the cylinders was evaluated using micro-computed tomography (micro-CT). Furthermore, bone regeneration and angiogenesis were evaluated histologically at 12 weeks.

RESULTS

Quantitative volumetric analyses using micro-CT showed a gradual increase in bone volume inside the cylinders in all three groups. Histological observation confirmed vigorous bone regeneration in the microporous groups compared to that in the macroporous group. In the upper part of the cylinders, soft tissue invaded the GBR site by passing through the pores of the macroporous mesh. The blood vessels in the upper part of the cylinders were smaller in the microporous groups than in the macroporous group. There was no difference in bone formation between cylinders filled with DBBM or carbonate apatite.

CONCLUSION

Microvasculature penetrates 50-μm diameter micropores and accelerates bone formation inside the cylinder, which was set on rat calvaria. The microporous titanium mesh can facilitate angiogenesis from both the dura mater and periosteal in vertical ridge augmentation. Our data showed superiority of microporous titanium vascular permeability and osteoconductivity, supporting bone growth.

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.

Vertical Guided Bone Augmentation Using Titanium Mesh Domes Coated with Natural Latex Extracted from Hevea brasiliensis

The subject of this work is the evaluation of the use of titanium mesh domes coated with latex extracted from Hevea brasiliensis to promote vertical guided bone augmentation (GBA), above the normal limits of the skeleton. Twenty-four New Zealand rabbits were used, in which a circular groove of eight millimeters in diameter and nine holes in the internal region reaching the medulla were made with a trephine drill, in the calvaria. The dome, four millimeters in height, was fixed above this defect. The animals were divided into four groups (N = 6). The first (control) received a titanium dome not covered by the periosteum, and the second received a titanium dome that was covered by the periosteum. For the third, a dome with a latex coating was used and was not covered by the periosteum, and for the fourth, a titanium dome with a latex coating was used and was covered by the periosteum. After 90 days, the animals were euthanized. Computerized tomography imaging demonstrated that vertical bone augmentation was achieved in the groups with titanium domes coated with latex. Microscopic evaluation showed that there were no differences between the control group and Group 2, or between Groups 3 and 4. The other comparisons showed statistically significant differences (p < 0.05, ANOVA-Tukey).

Vertical Bone Augmentation Using Three-dimensionally Printed Cap in the Rat Calvarial Partial Defect

BACKGROUND/AIM

Lost alveolar bone is commonly restored by distraction osteogenesis or bone blocks for substantial vertical bone augmentation (VBA), that is applied in conjunction with a barrier system. This study was performed to determine whether volume control of a three-dimensional (3D) printed nylon cap in the rat calvarial partial thickness bone defect would induce qualitative and quantitative differences in vertical bone regeneration.

MATERIALS AND METHODS

A rat calvarial partial thickness bone defect was prepared and the 3D cap covered the defect to induce VBA, while the control group was left without cap placement. After six weeks the animals were sacrificed, and the calvaria were prepared for micro-CT (μCT) and histology.

RESULTS

Quantitative μCT results showed that our cap system has significant osteoconductive properties, and the histology slide revealed new bone filled inside the cap.

CONCLUSION

The results clearly showed that this system was successful for VBA in a research animal model.

Is More Cortical Bone Decortication Effective on Guided Bone Augmentation?

This study aims to evaluate the possible effect of more cortical bone decortication (CBD) on guided bone augmentation. A total of 16 New Zealand rabbits and 32 titanium domes were used. No cortical bone decortication was applied to the control group and in the study groups, the cortical bones were decorticated with a round burr (Group A: 1 hole with bleeding, Group B: 5 holes with bleeding, Group C: a thin layer of compact bone was completely removed with no bleeding). Then 2 titanium domes were placed on the calvarium of each rabbit with hydroxyapatite/beta-tricalcium phosphate. After 3 months, the animals were sacrificed and specimens were sent for histological and histomorphometric analysis. Histological and histomorphometric analysis showed that bone decortication with burr significantly increased new bone regeneration in all the experimental groups compared with the control group (P <0.05). No statistically significant difference was determined between the study groups. In conclusion, CBD, which has no negative impact on surgery, has a positive effect on guided bone augmentation. However, a greater amount of CBD does not have a greater effect.

Pre-clinical in vivo models for the screening of bone biomaterials for oral/craniofacial indications: focus on small-animal models

Preclinical in vivo experimental studies are performed for evaluating proof-of-principle concepts, safety and possible unwanted reactions of candidate bone biomaterials before proceeding to clinical testing. Specifically, models involving small animals have been developed for screening bone biomaterials for their potential to enhance bone formation. No single model can completely recreate the anatomic, physiologic, biomechanic and functional environment of the human mouth and jaws. Relevant aspects regarding physiology, anatomy, dimensions and handling are discussed in this paper to elucidate the advantages and disadvantages of small-animal models. Model selection should be based not on the 'expertise' or capacities of the team, but rather on a scientifically solid rationale, and the animal model selected should reflect the question for which an answer is sought. The rationale for using heterotopic or orthotopic testing sites, and intraosseous, periosseous or extraskeletal defect models, is discussed. The paper also discusses the relevance of critical size defect modeling, with focus on calvarial defects in rodents. In addition, the rabbit sinus model and the capsule model in the rat mandible are presented and discussed in detail. All animal experiments should be designed with care and include sample-size and study-power calculations, thus allowing generation of meaningful data. Moreover, animal experiments are subject to ethical approval by the relevant authority. All procedures and the postoperative handling and care, including postoperative analgesics, should follow best practice.

Vertical bone regeneration with deproteinised bovine bone mineral or biphasic calcium phosphate in the rabbit calvarium: effect of autologous platelet lysate

Although bone substitutes associated with platelet concentrates are widely used to vertically reconstruct alveolar ridges, their respective and specific contribution remain controversial. The aim of this study was to evaluate the benefit of using either biphasic calcium phosphate (BCP) or demineralised bovine bone mineral (DBBM) alone or with autologous platelet lysate (APL) in vertical bone regeneration. The study involved fourteen New Zealand rabbits. Autologous APL was prepared by freeze-thawing from a platelet suspension (10(9) platelets/ml). Four CP titanium (cpTi) cylinders were fixed to each calvarium; one cylinder was empty, one was filled with APL alone and the others were filled either with BCP or BCP + APL or DBBM or DBBM + APL. New bone formation and biomaterial resorption were evaluated using non-demineralised histology and histomorphometry. After 6 weeks, new bone formation was observed in all cylinders. The newly formed bone in the cylinders filled with APL alone, DBBM and BCP was significantly increased by (0.6-, 2.5- and 3.3-fold, respectively) (P < 0.0001) compared to results obtained with the empty cylinders. Vertical bone height in the cylinders filled with BCP was greater to that observed with DBBM. The residual material in the cylinders filled with BCP was significantly (P < 0.0001) lower (0.35-fold) than that with DBBM. Both newly formed bone and residual material in the cylinders filled with BCP + APL or DBBM + APL were similar to those filled with either BCP or DBBM, respectively. This study provided evidence that APL alone, as well as DBBM and BCP, have a beneficial effect on vertical bone formation and remodelling. APL associated with either DBBM or BCP did not provide additional benefits.

Mechanisms of guided bone regeneration: a review

Post-extraction crestal bone resorption is common and unavoidable which can lead to significant ridge dimensional changes. To regenerate enough bone for successful implant placement, Guided Bone Regeneration (GBR) is often required. GBR is a surgical procedure that uses barrier membranes with or without particulate bone grafts or/and bone substitutes. There are two approaches of GBR in implant therapy: GBR at implant placement (simultaneous approach) and GBR before implant placement to increase the alveolar ridge or improve ridge morphology (staged approach). Angiogenesis and ample blood supply play a critical role in promoting bone regeneration.

Feasibility of alpha tricalcium phosphate for vertical bone augmentation

AIM

Inadequate vertical bone compromises dental implant positioning and subsequent restoration. This study was carried out to investigate the feasibility of alpha tricalcium phosphate (α-TCP) for vertical bone augmentation.

METHODS

Nine cortical perforations were made on each side of the parietal bone of rat calvaria under continuous saline coolant. Polytetrafluoroethylene cylinders were placed under the periosteum and α-TCP particles were applied in the cylinders in the TCP group while the cylinders were left empty in the control group. The animals were sacrificed at 4 and 8 weeks after surgery and analyzed radiologically and histologically.

RESULTS

The augmented bone volumes in the control and TCP groups were 91.5 ± 25.6% and 76.5 ± 49.8% (mean ± SD) of the original bone at 4 weeks, and 136.3 ± 59.7% and 139 ± 62.4% at 8 weeks respectively. There was no significant difference between control and test groups. At 4 weeks the bone height was augmented by 168.8 ± 26.7% and 128.8 ± 62% in the control and TCP groups respectively (not significant), whereas significantly higher vertical bone was achieved in the TCP group than in the control group at 8 weeks (251 ± 32% vs 179.2 ± 30.3%, P < 0.05).

CONCLUSION

After 8 weeks α-TCP is effective in maintaining space under periosteum and potentially would be applicable in vertical bone augmentation.

Autogenous bone with or without hydroxyapatite bone substitute augmentation in rat calvarium within a plastic cap

OBJECTIVES

We evaluated the effect of autogenous bone (AB) and hydroxyapatite bone (HA) for the assessment of bone augmentation beyond the skeletal envelope in the rat calvarium.

STUDY DESIGN

The calvaria of 12 rats were exposed and 2 plastic caps were placed with AB and HA or AB alone in the calvarium. Images of bone augmentation within the plastic caps were taken using micro-CT (R_mCT). Histologic sections were cut along the same plane as those used for the R_mCT images at 12 weeks. Bone volume (BV) was calculated using BV-measuring software.

RESULTS

BV increased at both the experimental and control sites. The newly generated tissue did not significantly differ between the experimental and control sites; however, the mineralized tissue was significantly higher at control sites compared with experimental sites.

CONCLUSIONS

The results indicate that the combination of HA and AB was biocompatible and allowed osteoconduction.

Correlation in the densities of augmented and existing bone in guided bone augmentation

OBJECTIVES

Our previous work used a rabbit experimental model to investigate the effectiveness of guided bone augmentation (GBA). Although a density similar to that of existing bone is required for successful bone augmentation, few studies have compared the densities of augmented and existing bone. The purpose of the present study was to investigate the correlation in the densities of existing and augmented bone following GBA in rabbit calvaria.

MATERIAL AND METHODS

The calvaria of 18 adult male Japanese white rabbits were exposed. A circular groove and nine small holes were drilled into the cortical surface of each left parietal bone. A customized, standardized, hemispherical titanium cap was press-fitted into each groove. Six animals were sacrificed after each healing period of 1, 3, and 6 months and histomorphometric analyses were conducted.

RESULTS

Significant increases were observed in the area of augmented bone between 1 and 6 months (62.7 ± 21.6% vs. 93.4 ± 3.9%). In contrast, no significant differences among healing periods were observed in the density of augmented or existing bone. Regression analysis demonstrated a significant positive correlation between the densities of augmented and existing bone; the strength of this correlation increased with the length of healing (R(2) =0.97).

CONCLUSIONS

These results suggest that the area of augmented bone increases significantly with the length of healing, filling the occlusive space after 6 months, and that the density of augmented bone depends on that of the existing bone, such that augmented bone has a density about half that of the existing bone.

A comparative study of microfocus CT and histomorphometry in the evaluation of bone augmentation in rat calvarium

Microfocus computed tomography (micro-CT; R_mCT) is a dynamic noninvasive method for measuring bone regeneration. This study evaluated whether R_mCT was equivalent to histomorphometry in assessing bone augmentation. Two plastic caps of graft material with (experiment) or without hydroxyapatite (HA; control) were placed in the exposed calvaria of rats. Images of bone augmentation within the plastic caps were then taken using R_mCT. Histological sections were cut along the same plane as that used for the micro-CT images. Bone regeneration beyond the skeletal envelope occurred at both the experimental and control sites. Bone volume also increased at both sites. In addition, consistent patterns of bone formation were observed in both R_mCT and histological images. R_mCT analysis enables highly quantitative and qualitative measurement of bone augmentation in living animals.

Effects of decortication in the treatment of bone defect around particulate dentin-coated implants: an experimental pilot study

OBJECTIVES

The purpose of this study was to evaluate the effects of decortication during bone grafting in defect areas surrounding particulate dentin-coated implants.

STUDY DESIGN

Six dogs were randomly assigned to 3 groups, and each group was further divided into 2 subgroups. The subgroups consisted of dogs that received particulate dentin-coated implants after 4 or 8 weeks. The defects were treated as follows: control group, unfilled defect; experimental group 1, defect filled with Tutoplast without decortication; experimental group 2, defect filled with Tutoplast with decortication. Histologic sections and histomorphometric analysis were obtained 4 and 8 weeks after surgery.

RESULTS

Compared to the 4-week subgroup, statistically significant new bone formation was observed in the 8-week subgroup. In the 4-week subgroup, the area of new bone formation was larger in the group that underwent cortical bone perforation with bone grafting; however, no significant difference was detected within the 8-week subgroup.

CONCLUSION

According to these results, decortication increases early bone formation after implant placement.