Long-term stability of autogenous bone grafts following combined application with guided bone regeneration

Efficacy of biomaterials for lateral bone augmentation performed with guided bone regeneration. A network meta-analysis

Bone regeneration is often required concomitant with implant placement to treat a bone fenestration, a dehiscence, and for contouring. This systematic review assessed the impact of different biomaterials employed for guided bone regeneration (GBR) simultaneous to implant placement on the stability of radiographic peri-implant bone levels at ≥12 months of follow-up (focused question 1), as well as on bone defect dimension (width/height) changes at re-assessment after ≥4 months (focused question 2). Only randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared different biomaterials for GBR were considered. A Bayesian network meta-analysis (NMA) was performed using a random-effects model. A ranking probability between treatments was obtained, as well as an estimation of the surface under the cumulative ranking value (SUCRA). Overall, whenever the biological principle of GBR was followed, regeneration occurred in a predictable way, irrespective of the type of biomaterial used. A lower efficacy of GBR treatments was suggested for initially large defects, despite the trend did not reach statistical significance. Regardless of the biomaterial employed, a certain resorption of the augmented bone was observed overtime. While GBR was shown to be a safe and predictable treatment, several complications (including exposure, infection, and soft tissue dehiscence) were reported, which tend to be higher when using cross-linked collagen membranes.

Techniques on vertical ridge augmentation: Indications and effectiveness

Vertical ridge augmentation techniques have been advocated to enable restoring function and esthetics by means of implant-supported rehabilitation. There are three major modalities. The first is guided bone regeneration, based on the principle of compartmentalization by means of using a barrier membrane, which has been demonstrated to be technically demanding with regard to soft tissue management. This requisite is also applicable in the case of the second modality of bone block grafts. Nonetheless, space creation and maintenance are provided by the solid nature of the graft. The third modality of distraction osteogenesis is also a valid and faster approach. Nonetheless, owing to this technique's inherent shortcomings, this method is currently deprecated. The purpose of this review is to shed light on the state-of-the-art of the different modalities described for vertical ridge augmentation, including the indications, the step-by-step approach, and the effectiveness.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

A Novel Approach of Periodontal Osseous Wall Piezosplitting and Sequential Bone Expansion in Management of Localized Intra-Bony Defects with Wide Angulation—A Randomized Controlled Trial

Piezoelectric surgical instruments with various mini-sized tips and cutting technology offer a precise and thin cutting line that could allow the wider use of periodontal osseous wall swaging. This randomized controlled trial was designed to investigate the use of a minimally invasive piezo knife to harvest vascularized interseptal bone pedicles in treating intra-bony defects. Sixteen non-smoking patients (mean age 39.6 ± 3.9) with severe chronic periodontitis were randomly assigned into one of two groups (N = 8). The Group 1 (control) patients were treated by bone substitute grafting of the intra-bony defect, whereas the Group 2 patients were treated by intra-bony defect osseous wall swaging (OWS) combined with xenograft filling of the space created by bone tilting. In both groups, the root surfaces were treated with a neutral 24% EDTA gel followed by saline irrigation. Clinical and radiographic measurements were obtained at baseline and 6 months after surgery. The sites treated with osseous wall swaging showed a statistically significant probing-depth reduction and increase in clinical attachment compared with those of the Group 1 patients. The defect base level was significantly reduced for the OWS group compared to that of the Group 1 control. By contrast, the crestal bone level was significantly higher in the OWS group compared to Group 1. The crestal interseptal bone width was significantly higher in Group 2 at 6 months compared to the baseline value and to that of Group 1 (<0.001). The osseous wall swaging effectively improved the clinical hard- and soft-tissue parameters. The use of mini inserts piezo-cutting, sequential bone expanders for osseous wall redirection, and root surface EDTA etching appears to be a reliable approach that could allow the use of OWS at any interproximal dimension.

Mechanical Properties and Corrosion Resistance of TiAl6V4 Alloy Produced with SLM Technique and Used for Customized Mesh in Bone Augmentations

Bone augmentation procedures represent a real clinical challenge. One option is the use of titanium meshes. Additive manufacturing techniques can provide custom-made devices in titanium alloy. The purpose of this study was to investigate the material used, which can influence the outcomes of the bone augmentation procedure. Specific test samples were obtained from two different manufacturers with two different shapes: surfaces without perforations and with calibrated perforations. Three-point bending tests were run as well as internal friction tests to verify the Young’s modulus. Test samples were placed in two different buffered solutions and analyzed with optical microscopy. A further SEM analysis was done to observe any microstructural modification. Three-point flexural tests were conducted on 12 specimens. Initial bending was observed at lower applied stresses for the perforated samples (503 MPa) compared to non-perforated ones (900 MPa); the ultimate flexural strength was registered at 513 MPa and 1145 MPa for perforated and non-perforated samples, respectively. Both microscopic analyses (optical and SEM) showed no significant alterations. Conclusions: A normal masticatory load cannot modify the device. Chemical action in the case of exposure does not create macroscopic and microscopic alterations of the surface.

Clinical and histological outcomes of maxillary sinus floor augmentation with synthetic bone substitutes for dental implant treatment: A meta-analysis

The objective of the present review was to gather all available human randomized clinical trials comparing the clinical and histological results of synthetic bone substitutes used in maxillary sinus floor augmentation. Authors electronically searched in Pubmed/Medline, Scopus and Cochrane databases to analyse the success of endosseous dental implant, implant failure, peri-implant marginal bone loss, newly formed bone and residual bone graft material.  After the search, ten randomized clinical trials were included. Four studies ranging from low to unclear risk of bias were used for meta-analysis, being able to compare only biphasic calcium phosphate (BCP) and deproteinized bovine bone (DBB). A greater amount of residual graft material (mean difference -MD- 4.80 mm; 95% CI, 9.35 to 0.26; P= 0.040) was found in DBB group. No other statistically significant differences were found between BCP and DBB for the rest of outcomes. Thus, our results suggested that BCP can be considered a suitable alternative to DBB in maxillary sinus floor augmentation due to its clinical and histological results.

Bonegraft Wrap Technique: Avoiding Accentuated Labiomental Groove After Genioplasty

This work presents the wrap technique developed by the authors aiming to avoid the occurrence of unaesthetic deep labiomental fold in genioplasty. The technique recommends the use of particulate bone graft that is wrapped on collagen or a Surgicel membrane which is placed over the osteotomized segment of the chin fixated with a prebent 4-hole titanium plate.

Osteodistraction With Dental Implant-Borne Devices for Bone Regeneration in Atrophied Premaxilla

Aim of this work is to present the evolution of an innovative technique for tooth/implant supported bone distraction, leading to proper oral rehabilitation in patients with atrophic alveolar bone, even when a complete premaxilla expansion is needed, or in patients in whom implants were already present, but inserted in wrong position.Distraction osteogenesis was selected because of its moderate invasiveness, the few surgical steps needed, and the proper cost/benefits balance. This procedure is particularly suited for young patients with remarkable aesthetic demands related to active social and working life, as for elderly patients expecting lower surgical stress and risks.

Maxillary Sinus Floor Augmentation Using an Equine-Derived Graft Material: Preliminary Results in 17 Patients

Objective

Sinus floor elevation with lateral approach is probably the most frequently performed reconstructive procedure to rehabilitate posterior maxilla when a bone deficiency is present. Different graft materials have been proposed and tested, often with high clinical performances and predictable results. Histological analysis is required when evaluating new materials. We investigated human biopsies retrieved after sinus floor elevation procedure by histomorphometric evaluation to test the performance of an equine-derived bone grafting material.

Study Design

Seventeen consecutive patients were enrolled and sinus lift surgeries were performed using an equine bone graft. Six months after surgery, at implant placement, bone samples were collected. Histomorphometry analysis was carried out on decalcified samples.

Results

All surgeries were uneventful and no additional grafting was required prior to implant insertion. Forty percent of new bone formation was detected, which represented the most abundant tissue retrieved, followed by the residual graft material (33%) and fibrous tissue (27%). A significant reduction in particles size demonstrates a remodeling activity of the graft material.

Conclusion

Within the limitations of this study, this equine-derived bone graft proved to be an effective material to induce new bone formation in the sinus floor elevation procedure.

Maxillary Sinus Grafting With Biphasic Bone Ceramic or Autogenous Bone: Clinical, Histologic, and Histomorphometric Results From a Randomized Controlled Clinical Trial

PURPOSE

The present, randomized, controlled clinical trial compared the histologic and histomorphometric results from maxillary sinus augmentation with either biphasic calcium phosphate (BCP) (60% hydroxyapatite and 40% β-tricalcium phosphate) or autogenous bone (AB) as bone-grafting materials.

MATERIAL AND METHODS

Ten patients received bilateral sinus elevation surgery with intraoral AB chips (control group) on one side and BCP (test group) on the contralateral side. After a healing period of 6 to 8 months, implant sites were created and trephine cores were harvested for histological and histomorphometric analysis of the grafted areas.

RESULTS

The histological examination of biopsies showed BCP particles interconnected by bridges of a vital newly formed bone. Histomorphometry demonstrated that the amount of newly formed bone in the control group (36.8%) was significantly greater than that in the BCP (28.2%) group (P = 0.0032). BCP and AB cores revealed an average of residual graft particles of 32.9% and 4.8%, respectively. The average percentage of soft tissue components was 38.9% in the BCP cores and 58.4% in the AB cores.

CONCLUSIONS

Based on our findings, the amount of vital bone formation was significantly higher for AB than that for BCP. However, BCP seemed to be a biocompatible and osteoconductive material that can be used with success as a bone substitute in maxillary sinus procedures.

Microarray gene expression during early healing of GBR-treated calvarial critical size defects

OBJECTIVES

To investigate the gene expression and molecular pathways implicated in the regulation of the osseous healing process following guided bone regeneration (GBR).

MATERIAL AND METHODS

Six 6-month-old Wistar male rats were used. Standardized 5-mm critical size defects were created in the parietal bones of each animal and treated with an extracranial and intracranial ePTFE membrane, according to the GBR principle. Three animals were randomly sacrificed after 7 and 15 days of healing. Total RNA was extracted from each sample and prepared for gene expression analysis. RNA quality and quantity were assessed, followed by hybridization of the cRNA to Affymetrix GeneChip Rat Genome 230 2.0 Arrays. The Affymetrix data were processed, and first-order analysis, quality control and statistical analysis were performed. Biological interpretation was performed via pathway and Gene Ontology (GO) analysis.

RESULTS

Between the 7- and 15-day samples, 538 genes were differently regulated. At day 7, inflammatory and immune responses were clearly upregulated. In addition, GO terms related to angiogenesis and cell cycle regulation were overexpressed. At day 15, a more complex cellular activity and cell metabolism were evident. The bone formation processes were significantly overexpressed, with several genes encoding growth factors, enzyme activity, and extracellular matrix formation found as upregulated. Remarkably, a negative regulation of Wnt signalling pathway was observed at 15 days.

DISCUSSION

The gene expression profile of the cells participating in osseous formation varied depending on the healing stage. A number of candidate genes that seem differentially expressed during early stages of intramembranous bone regeneration was suggested.

The effect of experimental osteoporosis on bone regeneration: part 2, proteomics results

OBJECTIVES

To identify and describe protein expression in a Wistar rat calvarial critical size defect (CSD) model following treatment with guided bone regeneration in healthy and osteoporotic conditions.

MATERIAL AND METHODS

Thirty-six 10-month-old female Wistar rats were used. Half of them were ovariectomized (OVX) and fed with a low-calcium diet to induce an osteoporotic-like status. In each animal of both groups, two 5-mm calvarial CSDs were treated with deproteinized bovine bone mineral graft particles and a bilayer collagen membrane. Six OVX and six control rats were randomly euthanized at 7, 14, and 30 days. One defect/animal was randomly chosen for proteomic analysis. Differently expressed proteins between the two groups were identified with matrix-assisted laser desorption time-of-flight mass spectrometry and liquid chromatography-mass spectrometry/mass spectrometry.

RESULTS

At 7 days, 29 and 27 proteins were, respectively, identified in the healthy and OVX animals. At 14 days, 103 proteins were detected in the healthy controls and 20 proteins in the OVX rats, while at 30 days, 31 and 75 proteins were identified, respectively. Only limited proteins known to play a role in the later stages of bone formation and maturation were identified within the animals 'proteomes.

DISCUSSION

The osseous formation process was quite immature even at 30 days of healing. An overexpression of inflammatory and stress response pathways was detected in the OVX animals, as well as a tendency toward a delayed maturation of the osseous wound and a reduced/delayed differentiation of osteoblast cell precursors.

The effect of experimental osteoporosis on bone regeneration: Part 1, histology findings

OBJECTIVES

To histologically define the healing events occurring in calvarial critical size defects (CSDs) following treatment with a collagen barrier for guided bone regeneration (GBR) and a particulate graft in healthy and osteoporotic conditions.

MATERIAL AND METHODS

Thirty-six 10-month-old, female, Wistar rats were used in this study. Half of them were ovariectomized (OVX) and fed with a low-calcium diet to induce an osteoporotic-like status. In each animal of both groups, two 5-mm CSDs were created, one in the centre of each parietal bone, and they were treated with a deproteinized bovine bone mineral (DBBM) particulate graft and a bi-layer collagen membrane. Six OVX and six healthy control rats were randomly euthanized at 7, 14 and 30 days. One defect per animal was randomly processed for decalcified histology. Three central sections were used for qualitative histology and histomorphometric analysis.

RESULTS

No significant difference in terms of percentage of newly formed bone was detected between the two groups at the different healing periods. However, a trend towards less bone formation and of poorer quality, expressed as reduced bone maturation, was detected in the OVX animals at 30 days.

DISCUSSION

According to this study, GBR with a collagen barrier and a DBBM graft can be successfully obtained also in osteoporotic-like conditions. Future studies considering longer healing periods and controlling for the confounding factors arising from the use of a particulate graft are needed to confirm these data.

The Use of Narrow Diameter Implants in the Molar Area

Implant rehabilitations in the posterior jaw are influenced by many factors such as the condition of the remaining teeth, the force factors related to the patient, the quality of the bone, the maintenance of the hygiene, the limited bone height, the type and extent of edentulism, and the nature of the opposing arch. The gold standard is to place a regular diameter implant (>3.7 mm) or a wide one to replace every missing molar. Unfortunately, due to horizontal bone resorption, this option is not possible without lateral bone augmentation. In this situation, narrow diameter implant (NDI < 3.5 mm) could be the alternative to lateral bone augmentation procedures. This paper presents a clinical study where NDIs were used for the replacement of missing molars. They were followed up to 11 years. Special considerations were observed and many parameters were evaluated. NDI could be used to replace missing molar in case of moderate horizontal bone resorption if strict guidelines are respected. Yet, future controlled prospective clinical trials are required to admit their use as scientific evidence.

Can bone marrow aspirate concentrate change the mineralization pattern of the anterior maxilla treated with xenografts? A preliminary study

Objective:

To evaluate bony reconstruction of the atrophic anterior maxilla using particulate grafts with or without autologous bone marrow aspirate concentrate (BMAC).

Materials and Methods:

Eight patients with atrophy of the anterior maxilla due to teeth loss were selected and split into groups according to the type of material used: Control Group (CG) (n = 4) - particulate xenograft only and Test Group (TG) (n = 4) - a combination of particulate xenograft and BMAC. Both groups received a collagen membrane to cover the xenograft. After 4 months, during implant placement, a sample of bone was removed from the graft area using a 2 mm diameter trephine bur. The specimens were fixed and preserved for histomorphometric evaluation, which included the following parameters: Mineralized tissue (MT) and non-MT (NMT). Cone beam computed tomography was performed at 3 time intervals to measure bone thickness: (1) Before grafting, (2) 4 months and (3) 8 months postgrafting, using localized bone gain (mm) as the outcome variable.

Results:

Tomographic analysis revealed bone gain in CG of 3.78 ± 1.35 mm and 4.34 ± 1.58 mm at 4 and 8 months, respectively. TG showed an increase of 3.79 ± 0.52 mm and 4.09 ± 1.33 mm after 4 and 8 months, respectively. Histomorphometric analysis revealed that, for CG, MT- and NMT-related values were 52.3% ± 16.78% and 47.70% ± 5.55%, respectively, whereas for TG, they were 65.04% ± 20.98% and 34.96 ± 10.38, respectively.

Conclusion:

Although radiographic bone gain appeared similar between the groups, the use of BMAC obtained via the BMAC^® method revealed an increased mineralization trend in the anterior maxilla. It must be highlighted, however, that this is a preliminary study with a relatively small sample population and further studies with larger sample sizes are needed to verify these results.

Differences in the developmental origins of the periosteum may influence bone healing

BACKGROUND AND OBJECTIVE

The jaw bone, unlike most other bones, is derived from neural crest stem cells, so we hypothesized that it may have different characteristics to bones from other parts of the body, especially in the nature of its periosteum. The periosteum exhibits osteogenic potential and has received considerable attention as a grafting material for the repair of bone and joint defects.

MATERIAL AND METHODS

Gene expression profiles of jaw bone and periosteum were evaluated by DNA microarray and real-time polymerase chain reaction. Furthermore, we perforated an area 2 mm in diameter on mouse frontal and parietal bones. Bone regeneration of these calvarial defects was evaluated using microcomputed tomography and histological analysis.

RESULTS

The DNA microarray data revealed close homology between the gene expression profiles within the ilium and femur. The gene expression of Wnt-1, SOX10, nestin, and musashi-1 were significantly higher in the jaw bone than in other locations. Microcomputed tomography and histological analysis revealed that the jaw bone had superior bone regenerative abilities than other bones.

CONCLUSION

Jaw bone periosteum exhibits a unique gene expression profile that is associated with neural crest cells and has a positive influence on bone regeneration when used as a graft material to repair bone defects. A full investigation of the biological and mechanical properties of jaw bone as an alternative graft material for jaw reconstructive surgery is recommended.

Role of oxidative and nitrosative stress in autogenous bone grafts to the mandible using guided bone regeneration and a deproteinized bovine bone material

The aim of this study was to evaluate the role of oxidative and nitrosative stress in autogenous bone grafts to the mandible based on immunohistochemical analysis.

MATERIAL AND METHODS

Using a well-established sheep model autogenous bone grafts were harvested form the iliac bone. A combination of a Collagen Membrane (CM) and Deproteinized Bovine Bone Material (DBBM) was used to cover the bone graft (Experiment 2). This modification was compared with simple onlay bone grafts (Experiment 1). Immunohistochemically, the expression of specific stable degradation products of oxidative and nitrosative stress was compared between the two experimental groups.

RESULTS

Specific markers for oxidative and nitrosative stress showed statistically significant differences in expression in the different experimental groups. The influence of oxidative and nitrosative stress on osteoblasts (OB), osteoclasts (OC), and osteocytes (OCy) was analysed. Experiment 2 showed increased expression of markers in OB and decreased expression in OC.

CONCLUSIONS

Taking the result of this study and reports from the literature into consideration grafts in Experiment 2 showed less resorption and atrophy, higher activity of OB and inhibition of OC, and less expression of Reactive Oxygen and Nitrogen Species (RONS) as markers of oxidative stress within the graft. These data illustrate the improved remodelling processes in grafts using CM and DBBM.

Effects of mechanical loading on the degradability and mechanical properties of the nanocalcium-deficient hydroxyapatite-multi(amino acid) copolymer composite membrane tube for guided bone regeneration

Background and methods

Guided bone regeneration (GBR) is a new treatment for bone defects, and the property of membrane is critical to the success of GBR. This study focuses on a novel membrane tube for GBR, which was prepared by a nanocalcium-deficient hydroxyapatite–multi(amino acid) copolymer (n-CDHA-MAC) composite. The biomechanical strength and degradability of this membrane tube under mechanical loading after immersion in phosphate-buffered solution were investigated to evaluate the effects of mechanical loading on the membrane tube. The membrane-tube group with no mechanical loading and femora bone were used as controls.

Results

The compressive strength and bending strength of n-CDHA-MAC membrane tubes were 66.4 ± 10.2 MPa and 840.7 ± 12.1 MPa, which were lower than those of the goats’ femoral bones (69.0 ± 5.5 MPa and 900.2 ± 17.3 MPa), but there were no significant (P > 0.05) differences. In the in vitro degradability experiment, all membrane tubes were degradable and showed a surface-erosion degradation model. The PH of solution fluctuated from 7.2 to 7.5. The weight and mechanical strength of loaded tubes decreased more quickly than nonloaded ones, with significant differences (P < 0.05). However, the strength of the loaded group after degradation achieved 20.4 ± 1.2 MPa, which was greater than the maximum mechanical strength of 4.338 MPa based on goat femoral middle stationary state by three-dimensional finite-element analysis.

Conclusions

n-CDHA-MAC membrane tubes have good biomechanical strength during degradation under mechanical loading. Therefore, this membrane tube is an ideal GBR membrane for critical size defects of long bones in goats for animal experiments.

Controlled release strategies for bone, cartilage, and osteochondral engineering--Part I: recapitulation of native tissue healing and variables for the design of delivery systems

The potential of growth factors to stimulate tissue healing through the enhancement of cell proliferation, migration, and differentiation is undeniable. However, critical parameters on the design of adequate carriers, such as uncontrolled spatiotemporal presence of bioactive factors, inadequate release profiles, and supraphysiological dosages of growth factors, have impaired the translation of these systems onto clinical practice. This review describes the healing cascades for bone, cartilage, and osteochondral interface, highlighting the role of specific growth factors for triggering the reactions leading to tissue regeneration. Critical criteria on the design of carriers for controlled release of bioactive factors are also reported, focusing on the need to provide a spatiotemporal control over the delivery and presentation of these molecules.

Expression of growth factors during the healing process of alveolar ridge augmentation procedures using autogenous bone grafts in combination with GTR and an anorganic bovine bone substitute: an immunohistochemical study in the sheep

OBJECTIVES

This study aims to evaluate the expression of various immunohistochemical growth factors and vascularization markers in augmentation on the mandible comparing onlay bone grafts and Guided Bone Regeneration (GBR).

MATERIALS AND METHODS

Using a sheep in vivo model, autogenous bone grafts were harvested from the iliac crest. A combination of a resorbable collagen membrane (CM) and a Deproteinized Bovine Bone Material (DBBM) was performed. This modification of the host side was compared with an onlay bone graft control group. Expression of different vascularization markers was compared between these groups.

RESULTS

The expression of revascularization markers was significantly higher within the modification of the host side using GBR and DBBM. Regarding different graft regions, a significantly higher expression within the bone graft using GBR and DBBM could be observed in staining on bone morphogenetic protein-2 (BMP-2) (5.75 vs. 3.55), vascular endothelial growth factor (VEGF) (3.08 vs. 1.64), VEGF Receptor 1 (VEGFR-1) and VEGF Receptor 2 (VEGFR-2) (4.88 vs. 2.24 and 5.06 vs. 2.74), and endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) (5.29 vs. 3.28 and 5.22 vs. 3.09; p = 0.000, all others p < 0.05), whereas the control group showed a higher rate of resorption during the surveillance period until euthanasia of sheep after 16 weeks.

CONCLUSION

The use of GBR and DBBM in the transplantation process of autogenous bone grafts compared with the therapeutical use of certain growth factors may enhance vascularization and lower atrophy and resorption.

CLINICAL RELEVANCE

The use of a combination of GBR and DBBM in augmentation procedures on the mandible shows less resorption than simple onlay bone grafts and seems to be superior in a clinical use.

Effects of EMD in combination with bone swaging and calcium phosphate bone cement on periodontal regeneration in one-wall intrabony defects in dogs

BACKGROUND AND OBJECTIVE

Although the application of EMD is a widely accepted periodontal-regenerative therapy, its effects on noncontained intrabony defects are unpredictable because of the lack of a space-making property. The combined use of EMD and autogenous bone grafts reportedly stimulates significant periodontal regeneration in intrabony defects. The aim of the present study was to evaluate the effects of EMD in combination with bone swaging (BS) and injectable calcium phosphate bone cement (CPC), which was placed into the spaces between the grafted swaged bone and the proximal host bone, on periodontal healing in one-wall intrabony defects in dogs.

MATERIAL AND METHODS

One-wall intrabony defects (3 mm wide and 5 mm deep) were surgically created on the mesial and distal sides of the bilateral mandibular premolars in four dogs. The 16 defects were assigned to one of the following treatments: EMD only, BS only, EMD with BS (EMD + BS), or EMD with BS and CPC (EMD + BS + CPC). The animals were killed 8 wk after surgery for histologic evaluation.

RESULTS

The height of newly formed bone was significantly greater in the EMD + BS + CPC group (3.73 ± 0.30 mm) than in the BS-only (2.74 ± 0.33 mm; p < 0.05) and EMD + BS (2.88 ± 0.98 mm; p < 0.05) groups. The area of newly formed bone was significantly larger in the EMD + BS + CPC group (5.68 ± 1.66 mm(2)) than in the EMD-only (3.68 ± 0.33 mm(2); p < 0.05), BS-only (3.48 ± 1.26 mm(2); p < 0.05) and EMD + BS (3.38 ± 1.37 mm(2); p < 0.05) groups. The EMD-only (4.63 ± 0.42 mm), EMD + BS (4.67 ± 0.30 mm) and EMD + BS + CPC (4.78 ± 0.54 mm) groups showed significantly greater cementum formation than did the BS-only group (3.93 ± 0.56 mm; p < 0.05).

CONCLUSION

These results indicate that treatment with EMD + BS + CPC promotes favorable periodontal healing in one-wall intrabony defects in dogs.

A novel osteogenesis technique: The expansible guided bone regeneration

Guided bone regeneration is a unique osteogenesis technique that requires a barrier membrane under periosteum to create space for bone regeneration. However, creating sizeable spaces is clinically not commonly feasible. A titanium plate and a thin silicone membrane were surgically layered on each calvaria of eight rabbits. Then, the periphery of the silicone membrane was fixed by a plastic ring to the underlying bone using titanium micro screws. After 1 week, a 5-mm-length titanium screw was used to elevate the titanium plate, which in turn elevated the silicone membrane together with overlying soft tissue in a rate of 1 mm/day for 5 days to create a secluded space. Animals were killed at 2 months (n = 4, group 1) and 4 months (n = 4, group 2) after the elevation. Histological and microradiographical analyses demonstrated creation of an amount of de novo bone formation (68.2 ± 22 mm(3) in group 1 and 70.3 ± 14 mm(3) in group 2) in the sizeable created spaces (207.1 ± 31 mm(3) in group 1 and 202 ± 21 mm(3) in group 2) without exposure of the device. This novel osteogenesis technique, "expansible guided bone regeneration," created a substantial in vivo incubator without applying growth factors or osteoprogenitor cells. Creating a growing space over the secluded surface allowed the development of normal biological healing process occurring on the bone surface into a regenerative process, generating bone outside the genetically determined skeletal bone. This technique is a new tissue engineering approach stimulating endogenous tissue repair without applying cells or factors exogenously.

The effect of loading in regenerated bone in dehiscence defects following a combined approach of bone grafting and GBR

OBJECTIVES

To evaluate by histology the effect of loading on the regenerated bone at dehiscence type defects around implants when treated with a combined approach of bone grafting and guided bone regeneration (GBR).

MATERIALS AND METHODS

In twelve Göttingen mini-pigs, the lower premolars and first molars were extracted and the alveolar process was reduced in width. After 3 months, two Straumann SLActive (Straumann AG, Basel, Switzerland) implants were placed in each hemi-mandible. Twelve implants were placed into the reduced alveolar ridge (group P) with no further defect or treatment on the site, while on 36 implants, buccal dehiscence defects were created and treated as follows: Group T1: synthetic bone substitute (Straumann Bone Ceramic, SBC, Straumann AG). Group T2: SBC with a polyethylene glycol membrane (Straumann MembraGel, Straumann AG); Group N: the dehiscence remained untreated. Three months following implantation, long, custom-made, healing abutments were placed in one hemi-mandible only to ensure functional loading. After 2 months, histological analysis was performed.

RESULTS

A trend for lower residual defect height and higher bone-to-implant contact was observed in the loaded sites compared with non-loaded sites in groups P, T1 and N. In group T2, the opposite effect was observed. In terms of bone formation, sites treated with SBC grafting and GBR (group T2) exhibited the largest surface area of regenerated bone followed by T1 and N. Significant resorption of the graft particles was noted in group T2 and the graft surface area occupied by SBC was significantly higher in group T1 compared with group T2 (P < 0.05).

CONCLUSIONS

Loading may have a positive effect on bone-to-implant contact in implants inserted in pristine bone or inserted in dehiscence sites and treated by grafting/no grafting.

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.

The effect of SLActive surface in guided bone formation in osteoporotic-like conditions

OBJECTIVES

The aim of the study was to evaluate new bone formation under etched titanium (SLA) and modified-etched hydrophilic titanium (modSLA) domes placed on the calvarium of healthy, osteoporotic and osteoporotic treated with bisphosphonates rabbits.

METHODS

Experimental osteoporosis was induced by ovariectomy (OV) and calcium-deficient diet in 24 New Zealand female rabbits. Twelve OV rabbits were treated with weekly dozes of alendronate (Fosamax(®)) (B) while 12 OV rabbits received no treatment (O). Another 12 rabbits were sham operated and used as healthy controls (C). At 6 weeks following OV, one modSLA and one SLA titanium dome were placed in the parietal bones of each rabbit. The animals were sacrificed at 30 and 120 days following the dome placement. Various histomorphometric measurements were performed in the most central of the undecalcified sections produced.

RESULTS

After 30 days of healing, in the C group, the total bone (TB) area was 37.6% and 37.0% under the modSLA and SLA domes, respectively. In the O group, the TB was 35.7% and 24.8%. In the B group, TB was 37.0% and 32.1%, respectively. After 120 days of healing, in the C group TB was 40.1% and 36.4%, respectively. In the O group, TB was 29.6% and 27.9%, respectively. In the B group, TB was 49.7% and 42.5%, respectively. Hierarchical analysis of variance showed that the type of titanium dome significantly influenced new bone and the amount of new bone being in contact with inner surface of the dome (BIC) independently of the observation period and group (P<0.05). The administration of bisphosphonates influenced the BIC (P<0.05).

CONCLUSION

The use of modSLA surface may promote bone healing and osseointegration in osteoporotic rabbits, whereas administration of bisphosphonates may compromise the osseointegration of the newly formed bone at the early healing period.

The comparative analysis of homologous fresh frozen bone and autogenous bone graft, associated or not with autogenous bone marrow, in rabbit calvaria: a clinical and histomorphometric study

The aim of this study was to evaluate the potential of fresh frozen homologous and autogenous grafts, associated or not with autogenous bone marrow, to form bone. Sixty titanium cylinders were used, and were fixed to the skulls of 30 rabbits. These cylinders were filled with (A) autogenous bone (AM) autogenous bone associated with the bone marrow (H) fresh frozen homologous bone (HM) fresh frozen homologous bone associated with the bone marrow (M) pure autogenous bone marrow and (C) blood clot. The animals were sacrificed after 02 and 03 months. After clinical evaluation, the samples were stained with hematoxylin, eosin and Mallory Trichrome dyes for optical microscopy analysis and histomorphometric analysis. Experimental groups that received mineralized materials (A, AM, H, HM) showed the best bone formation results, presenting no statistical difference between them (P > 0.05). Groups that did not receive mineralized materials (M and C) showed the worst results (P < 0.05), but the M group showed better results than the C group. Most of the autogenous and homologous bone particles were resorbed and there was a larger amount of residual particles in the homologous graft (H, HM) when compared with the autogenous graft (A, AM; P < 0.05). These findings suggest that fresh frozen homologous grafts produced similar amounts of new bone when compared with the autogenous grafts. However, the amount of residual bone particles was larger in the homogenous groups, which may indicate a slower remodeling process. The homologous fresh frozen bone seems to be a good osteoconductive material. The use of only autogenous bone marrow showed better results when compared to the bood clot. However, this research indicates that association with mineralized materials is required.

Osteoconduction of different sizes of anorganic bone particles in a model of guided bone regeneration

The aim of this study was to evaluate the effect of two different sizes of anorganic bone particles (300-500 and 850-1000μm) on the formation of new bone in a model of guided bone regeneration. In both groups, newly formed bone was seen histologically adjacent to the original surface of the skull, and there were outgrowths to the centre of the secluded graft 4 weeks after implantation. Some particles near the surface were in contact with the newly formed bone, and osteoconductive bone growth was present along their surface. Ten weeks after implantation the area created by grafting with small particles seemed to have a denser structure than that created with large particles. Histomorphometric analysis showed a higher density of newly formed bone in the small-particle group than in the large-particle group both 4 and 10 weeks after implantation. The total contact length between newly formed bone and particles and the ratio of bone:space between the particles were also significantly higher in the small-particle group at both time points. We conclude that the size of grafted particles of bone and the spaces between particles are important determinants of osteogenesis during guided bone regeneration.

Influence of host periosteum and recipient bed perforation on the healing of onlay mandibular bone graft: an experimental pilot study in the sheep

PURPOSE

The aim of this study was to evaluate the role of host periosteum and recipient bed perforation on the healing of an onlay graft to the mandible based on histologic and immunohistochemical analysis.

MATERIALS AND METHODS

Each of the 12 adult sheep used in the study received four iliac corticocancellous onlay bone grafts on the lateral surface of the mandible. In experiment 1, the block graft was placed in direct contact with the recipient bed and fixed with micro-screws, and in experiment 2, the recipient cortical bed was perforated before graft placement. The host periosteum around the graft was excised before flap replacement in experiment 3, and in experiment 4, a sheet of silicone membrane was placed between the graft and the recipient bed. The animals were euthanised at 4, 8, 12 and 16 weeks after surgery and the findings were analysed by routine microscopy (haematoxylin and eosin and tartrate-resistant acid phosphatase [TRAP] stains) and immunohistochemistry for proliferation and apoptotic markers (Ki67, caspase-3 and TUNEL stains).

RESULTS

After 8 weeks, full graft-host integration was seen in all the experimental groups except experiment 4. After 16 weeks, pronounced graft resorption and volume reduction was observed in experiments 1 and 2, whilst experiment 3 was characterised with extensive connective tissue infiltration and severe resorption of the graft. The number of osteoclasts expressed peaked at 4 weeks in experiments 1 and 2 and at 16 weeks in experiment 3. Immunoreactivity for Ki67 by osteoblasts lining the trabecular bone of the graft's spongiosa expressed moderate level of Ki67 at 8 weeks, and thereafter declined markedly. The strongest expression of caspase-3 on the bone surface was observed after 16 weeks.

DISCUSSION AND CONCLUSION

Recipient cortical bed perforation offered no advantage over non-perforated bed regarding healing and integration of a bone graft. Excision of the host overlying the periosteum was accompanied with rapid absorption of the grafts and partial or complete replacement with fibrous connective tissue. This study also demonstrated that cell death by apoptosis is a fundamental component of osteoblastic phenotypic differentiation during healing of corticocancellous bone graft.