Augmentation of the rat jaw with autogeneic cortico-cancellous bone grafts and guided tissue regeneration

Healing patterns of alveolar bone following ridge preservation procedures

OBJECTIVES

Examine the histomorphometric bone composition, following alveolar ridge preservation techniques and unassisted socket healing.

MATERIALS AND METHODS

Forty-two patients (42) requiring a single rooted tooth extraction were randomly allocated into three groups (n = 14 per group): Group 1: Guided Bone Regeneration (GBR) using deproteinised bovine bone mineral (DBBM) and a porcine collagen membrane; Group 2: Socket Seal (SS) technique using DBBM and a porcine collagen matrix; Group 3: Unassisted socket healing (Control). Trephined bone biopsies were harvested following a 4-month healing period. Forty-two samples underwent Back-Scattered Electrons -Scanning Electron Microscopy (BSE-SEM) imaging, with 15 samples examined using Xray Micro-Tomography (XMT) (n = 6 for each GBR/SS and n = 3 Control). Images were analysed to determine the percentage (%) of connective tissue, new bone formation, residual DBBM particles and direct bone to DBBM particle contact (osseointegration).

RESULTS

BSE-SEM analysis demonstrated that new bone formation was higher in the Control (45.89% ± 11.48) compared to both GBR (22.12% ± 12.7/p < .004) and SS (27.62% ± 17.76/p < .005) groups. The connective tissue percentage in GBR (49.72% ± 9), SS (47.81% ± 12.57) and Control (47.81% ± 12.57) groups was similar. GBR (28.17% ± 16.64) and SS (24.37% ± 18.61) groups had similar levels of residual DBBM particles. XMT volumetric analysis indicated a lower level of bone and DBBM particles in all test groups, when matched to the BSE-SEM area measurements. Osseointegration levels (DBBM graft and bone) were recorded at 35.66% (± 9.8) for GBR and 31.18% (± 19.38) for SS.

CONCLUSION

GBR and SS ARP techniques presented with less bone formation when compared to unassisted healing. GBR had more direct contact/osseointegration between the DBBM particles and newly formed bone.

The Effect of Different Types of Collagen Membranes on Peri-Implant Dehiscence Defects

AIM

This experimental study aimed to compare the bone-implant contact (BIC) following guided bone regeneration with 3 bioabsorbable collagen membranes on peri-implant dehiscence defects.

METHODS

Forty-eight standard dehiscence defects were created in the sheep iliac bone crest, and dental implants were placed into the defects. With the guided bone regeneration technique, the autogenous graft was placed into the defect and covered with different types of membranes: Geistlich Bio-Gide, Ossix Plus, and Symbios Prehydrated were covered. One group was left without a membrane as the control group (C) by applying only an autogenous graft. After recovery periods of 3 and 6 weeks, the experimental animals were sacrificed. Histologic sections were prepared by a nondecalcified method, and BIC was examined.

RESULTS

There was no statistically important difference between groups in the third week ( P >0.05). A statistically significant difference between groups was found in the sixth week ( P <0.01). Bone-implant contact values of the C group were significantly lower than those of the Geistlich Bio-Gide and Ossix Plus groups ( P <0.05). There was no statistically significant difference between control and Symbios Prehydrated groups ( P >0.05). In all sections, osseointegration was observed, with no signs of inflammation, necrosis, or foreign body reaction.

CONCLUSION

In our study, it has been concluded that the resorbable collagen membranes used in treating peri-implant dehiscence defects might affect the BIC, and the success varies according to the type of membrane used.

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.

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.

Role of periosteum in alveolar bone regeneration comparing with collagen membrane in a buccal dehiscence model of dogs

To investigate the role of periosteum on the treatment of buccal dehiscence defects comparing with collagen membrane in canine model. Bilateral dehiscence-type defects at the buccal side on the distal root of the lower 3rd/4th premolars were created in six beagle dogs with a total of 24 defects and assigned into three groups: Group A: blood clot in an untreated defect; Group B: deproteinized bovine bone material (DBBM) covered with an absorbable membrane; Group C: DBBM covered with the periosteum. The structural parameters for trabecular architecture and vertical bone regeneration were evaluated. Histological and histomorphometric evaluation were carried out to observe new bone formation and mineralization in the graft site. Immunohistochemical analysis was performed to identify the expression of osteopontin (OPN) and osteocalcin (OCN) at postoperative 3 months. Group C achieved greater vertical alveolar bone gain than that of group A and group B. The periosteum-covered group showed significantly greater new bone formation and accelerated mineralization. The greater immunolabeling for OPN and OCN was observed in group C than in group A. Periosteal coverage has explicit advantages over collagen membranes for the quality and quantity of new bone regeneration in dehiscence defects repairing.

Functionally graded membrane deposited with PDLLA nanofibers encapsulating doxycycline and enamel matrix derivatives-loaded chitosan nanospheres for alveolar ridge regeneration

Functionally graded membranes (FGM) with regenerative signals and nanofibrous topography mimicking the native extracellular matrix have been shown to improve the outcome of alveolar ridge regeneration (ARR). This study developed a novel FGM with doxycycline-enamel matrix derivative (EMD) nanofibrous composites deposition to coordinate anti-inflammation and differentiation signals, thus facilitating ARR. Doxycycline-loaded PDLLA nanofibers (PD), EMD-loaded chitosan nanospheres (CE), and CE-embedded PD (CE-PD) were fabricated by electrospinning, deposited on the surfaces of barrier membrane to develop a FGM, and the efficacy was validated by delivering the FGM to regenerate experimental alveolar ridge defects in rats. Results revealed that PD had potent antibacterial capability, and CE-PD allowed sustained release of EMD to promote osteogenesis in vitro. In the alveolar ridge defects, FGM with PD on the outer surface downregulated MMP-8, and wound dehiscence was further reduced with Cbfa1 upregulation in those treated by FGM with CE-PD on the inner surface at 1 week. FGM with CE-PD revealed significantly greater new bone formation and defect fill at 4 weeks. In conclusion, FGM with PD reduced early tissue breakdown and with CE-PD nanofibrous composites accelerated wound healing and facilitated osteogenesis, and thus could be an advantageous strategy for ARR.

Histological Evaluation of Guided Bone Regeneration in Osseous Defects Using A Novel Non-Resorbable Membrane

BACKGROUND: Guided bone regeneration and guided tissue regeneration procedures have been performed using barrier membranes in clinical dentistry to enhance bone formation in osseous defects, ridge preservation and reconstruction. Despite the considerable number of new biomaterials that develop with more advantages and fewer disadvantages for bone regeneration, the cost and surgical approach difficulties are still the main obstacles that we tried to overcome using the novel membrane. AIM: Our research aimed to assess histologically the bone formation using the novel membrane in experimental bone defects. MATERIAL AND METHODS: Our study was conducted on ten mongrel dogs. Each animal presented two groups. The first group was at the left side of the animal mandible which received Bio-Oss only while the right side received Bio-Oss and was covered by the novel non-resorbable membrane. These dogs were sacrificed (3, 6, 9 and 12 weeks) postoperatively for histological assessment of healing and bone formation of osseous defects. RESULTS: The histological evaluation showed that the formation of new bone in group I (Bio-OSS only) was less in amount as compared with group II (Bio-Oss with the novel non-resorbable membrane). CONCLUSION: The present clinical findings revealed that the novel non-resorbable membrane was inert and induced no inflammatory reaction or graft rejection. The study provided histological evidence of new bone formation in close contact with host bone due to osteoconductivity of Bio-Oss and cell occlussiveness of the membrane.

[Clinical efficacy of hydroxyapatite and tricalcium phosphate modified with hyaluronic acid in the treatment of patients with periimplantitis]

THE AIM OF THE STUDY

Was to assess the effectiveness of the use of hydroxyapatite (HAP) and tricalcium phosphate (TCF) modified with hyaluronic acid in the treatment of patients with periimplantitis.

MATERIALS AND METHODS

Clinical studies were conducted in 128 patients (44% male and 56% female) aged up to 55 years, who sought dental care with the main diagnosis of periimplant mucositis and periimplantitis. To compare the features of osseointegration of dental implants under bone remodeling three groups of patients were formed: one control and 2 main ones. In the control group the wound was managed under a blood clot, in the first main group HAP and TCF and in the second main group HAP and TCF modified with hyaluronic acid were used. X-ray examination was performed in various modes. Clinical assessment of implant stability in the operated area was carried out using subjective (percussion and palpation method) and objective method of frequency resonance analysis using the Osstell ISQ device calculating the stability coefficient of the dental implant (SCDI).

RESULTS

12 months after the periimplant zone remodeling procedure the bone resorption rates surrounding the implant were statistically significantly the lowest in the second main group (0.682±0.006 mm, p<0.001) compared with the values in the control and first main groups (1.626±0.022 and 1.025±0.034 mm, respectively). In the former groups bone resorption continued to progress during the observation period. In patients of the second main group, the average values of the SCDI for all study periods were 68.97±1.09 units which turned out to be the highest indicator and significantly differed from the values of other observation groups (p<0.05), which may be due to a tighter fit of the implants to the surface of the newly formed bone tissue.

CONCLUSION

The results of the study 12 months after the periimplant zone remodeling operation procedure prove the efficacy of HAP and TCF modified with hyaluronic acid for the treatment of patients with periimplantitis.

Ultraviolet Functionalization Improved Bone Integration on Titanium Surfaces by Fluorescent Analysis in Rabbit Calvarium

This study evaluated the effect of ultraviolet functionalization (UV) on bone integration ability in rabbit model, using epifluorescence microscopy. Each of 12 rabbits (n = 6) received randomly four titanium domes prepared with or without ultraviolet for 48 hours (UVC, λ = 250 ± 20 nm; Philips, Tokyo, Japan): (1) turned surface (T), (2) turned surface with UV (T-UV), (3) sandblasted (120 μm aluminum oxide) and etched by 18% hydrochloric acid and 49% sulphuric acid at 60°C for 30 min (SLA) and (4) SLA surface with UV (SLA-UV). Fluorochrome bone labels were marked by oxytetracycline at 25 mg/kg on 13th days and 14th days and calcein at 5 mg/kg on 3th days and 4th days before euthanization. The study samples were sacrified at 2 weeks and 4 weeks. The undecalcified specimens were prepared. The newly formed total bone of cross-sectional area (TB, %), the mineralized trabecular bone of cross-sectional area (MB, %), and the new bone and dome contact (BDC, %) were measured and analyzed by fluorescence microscope and Image Pro Express 6.0. The data of MB and TB showed new bone regeneration was increased in all groups, but no signs of difference were found. However, the means BDC of UV treatment on turned surface at 4 weeks, the UV treated on SLA surface at 2 weeks and 4 weeks were statistically significantly higher than the control group (P &lt; .05). Within the limitations of the study, it can be concluded that ultraviolet functionalization on the titanium surface could enhance the new bone tissues and titanium surface integration.

The Bioresorption and Guided Bone Regeneration of Absorbable Hydroxyapatite-Coated Magnesium Mesh

INTRODUCTION

Nonabsorbable metallic membrane for guided bone regeneration is remained permanently even though after complete healing. There would be metallic exposure followed by the risk of infection; the membrane should be removed for the additional procedure such as implant installation. Since absorbable nonmetallic mesh is absorbed within 3 to 6 months, it is unnecessary to be removed. However, the absorbable membrane shows lower retention, lower mechanical strength, and difficulty of manipulation than the nonabsorbable ones.The purpose of this study is to evaluate the ability of absorbable metallic mesh (hydroxyapatite-coated magnesium mesh) with acceptable mechanical properties and satisfying biocompatibility.

METHODS

The bioresorption and fate of magnesium were evaluated in Sprague Dawley rat (SD rat) with critical defect of calvarium. The critical defect with a diameter of 8 mm was made on calvarium using trephine bur in 18 SD rats. The defected models were divided into 2 groups: the control group (9 SD rat) without mesh and the experimental group (9 SD rat) with the insertion of prototype HA-coated magnesium mesh. The 3 SD rats were sacrificed at 6, 12, and 18 weeks. The histopathological and radiographic examinations were performed afterward.

RESULTS

In the control group, there was no specific symptom. The experimental group also showed no specific symptom including swelling and dehiscence related to hydrogen gas formation. From 6 to 18 weeks, the experimental group showed the progressive absorption and fracture of magnesium mesh. However, there was no specific effectiveness of guided bone regeneration in both groups. There was no significant difference in bone volume, bone surface, and bone volume fraction between the negative control group and the group with magnesium mesh (P >0.05).

CONCLUSION

Hydroxyapatite-coated magnesium mesh showed reasonable process of bioresorption and bony reaction; however, the effectiveness of guided bone regeneration and management of the bioresorption rate should be reconsidered.

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.

Treating Dehiscence During Implant Placement and Loading on Angled Abutment in Maxillary Lateral Incisor Region: A Case Report

The primary factor causing recession is the morphology and anatomy of the dentition. The facial bony plate overlying the root is usually very thin. The complete absence of bone over the facial root surface is referred to as dehiscence. Such buccal bone defects in case of implant dentistry threaten the survival of dental implant. Many surgical techniques are introduced to enhance alveolar bone volume for placing the dental implants. Guided bone regeneration (GBR) is one such established surgical technique for correcting buccal dehiscence defects, along with the use of various barrier membranes for the same. This case report describes an implant placement in the maxillary left lateral incisor region showing dehiscence on the labial cortical plate, along with bone graft and GTR membrane.

Immunohistochemial study on the expression of von Willebrand factor (vWF) after onlay autogenous iliac grafts for lateral alveolar ridge augmentation

INTRODUCTION

The main problems of autogenous bone transplants are their unpredictable atrophy and their loss of structure. One key factor lies in the poor revascularization of simple onlay grafts. The the aim of this study was to evaluate the revascularization processes in autogenous bone grafts from the iliac crest to the alveolar ridge.

METHODS

In a sheep model, autogenous bone grafts were harvested from the iliac crest. A combination of a resorbable collagen membrane (CM) and deproteinized bovine bone material (DBBM) was used to modify the bone graft (experiment 2). This was compared with a simple onlay bone graft (control group, experiment 1). The amount of vessels in bone and connective tissue (CT), and the amount of CT were analyzed. The expression of von Willebrand factor (vWF) was compared between the two experimental groups using immunohistochemical analysis.

RESULTS

The ratio of the amount of vessels in bone and CT changed over time, and more vessels could be detected in bone at 12-16 weeks of graft healing. The number of vessels were significantly higher in experiment 2 than in experiment 1. More CT was found in experiment 1, whereas the amount of CT in both experiments decreased over time.

CONCLUSION

This study shows a more intensive and extensive revascularization in experiment 2, as significantly more vessels were detected. The decreased amount of CT in experiment 2 clarifies its clinical superiority.

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.

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 design and use of animal models for translational research in bone tissue engineering and regenerative medicine

This review provides an overview of animal models for the evaluation, comparison, and systematic optimization of tissue engineering and regenerative medicine strategies related to bone tissue. This review includes an overview of major factors that influence the rational design and selection of an animal model. A comparison is provided of the 10 mammalian species that are most commonly used in bone research, and existing guidelines and standards are discussed. This review also identifies gaps in the availability of animal models: (1) the need for assessment of the predictive value of preclinical models for relative clinical efficacy, (2) the need for models that more effectively mimic the wound healing environment and mass transport conditions in the most challenging clinical settings (e.g., bone repair involving large bone and soft tissue defects and sites of prior surgery), and (3) the need for models that allow more effective measurement and detection of cell trafficking events and ultimate cell fate during the processes of bone modeling, remodeling, and regeneration. The ongoing need for both continued innovation and refinement in animal model systems, and the need and value of more effective standardization are reinforced.

The influence of three barrier membranes on modeling and incorporation of autologous onlay bone grafts in rats. An evaluation by transversal microradiography

OBJECTIVES

To determine whether covering an autologous bone grafts with three different barrier membranes prevents graft resorption, and to compare these membranes to each other.

DESIGN

In 192 rats a standardised 4.0mm diameter bone graft was harvested from the right mandibular angle and transplanted to the left. Membranes used to cover the grafts were a new poly(DL-lactide-epsilon-caprolactone) membrane, a collagen and expanded polytetrafluoroethylene membrane. The controls were left uncovered. Graft resorption and incorporation were measured with transversal microradiography (TMR) in the four groups at 2, 4 and 12 weeks. Data were analysed using multiple regression analyses.

RESULTS

Overall, there were no differences in modeling with resorption between the four groups. ePTFE at 12 weeks showed a lower mineralization ratio and graft height of the graft as compared to the other groups. The mean graft incorporation was progressive and nearly identical from 2 to 12 weeks in all groups.

CONCLUSIONS

Membranes have an equal effect on bone graft modeling and resorption as found in non-covered controls. Therefore, the indication to use a barrier membrane to prevent bone modeling with resorption and enhance incorporation of autologous onlay bone grafts is disputable.

The Influence of Barrier Membranes on Autologous Bone Grafts

In implant dentistry, there is continuing debate regarding whether a barrier membrane should be applied to cover autologous bone grafts in jaw augmentation. A membrane would prevent graft remodeling with resorption and enhance graft incorporation. We hypothesized that membrane coverage does not effect resorption and incorporation of autologous onlay bone grafts. We treated 192 male Sprague-Dawley rats. A 4.0-mm-diameter bone graft was harvested from the right mandibular angle and transplanted to the left. Poly(DL-lactide-ε-caprolactone), collagen, and expanded polytetrafluoroethylene membranes were used to cover the grafts. The controls were left uncovered. Graft resorption at 2, 4, and 12 weeks was evaluated by post mortem microradiography and microCT. Analysis of the data showed no significant differences among the 4 groups. This demonstrates that the indication of barrier membrane use, to prevent bone remodeling with resorption and to enhance incorporation of autologous onlay bone grafts, is at least disputable.

Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.

Reconstruction of mandibular segmental defects using the guided-bone regeneration technique with polylactide membranes and/or autogenous bone graft: a preliminary study on the influence of membrane permeability

PURPOSE

Bone maintenance after mandibular reconstruction with autogenous iliac crest may be disappointing due to extensive resorption in the long term. The potential of the guided-bone regeneration (GBR) technique to enhance the healing process in segmental defects lacks comprehensive scientific documentation. This study aimed to investigate the influence of polylactide membrane permeability on the fate of iliac bone graft (BG) used to treat mandibular segmental defects.

MATERIALS AND METHODS

Unilateral 10-mm-wide segmental defects were created through the mandibles of 34 mongrel dogs. All defects were mechanically stabilized, and the animals were divided into 6 treatment groups: control, BG alone, microporous membrane (poly L/DL-lactide 80/20%) (Mi); Mi plus BG; microporous laser-perforated (15 cm(2) ratio) membrane (Mip), and Mip plus BG. Calcein fluorochrome was injected intravenously at 3 months, and animal euthanasia was carried out at 6 months postoperatively.

RESULTS

Histomorphometry showed that BG protected by Mip was consistently related to larger amounts of bone compared with other groups (P <or= .0001). No difference was found between defects treated with Mip alone and BG alone. Mi alone rendered the least bone area and reduced the amount of grafted bone to control levels. Data from bone labeling indicated that the bone formation process was incipient in the BG group at 3 months postoperatively regardless of whether or not it was covered by membrane. In contrast, GBR with Mip tended to enhance bone formation activity at 3 months.

CONCLUSIONS

The use of Mip alone could be a useful alternative to BG. The combination of Mip membrane and BG efficiently delivered increased bone amounts in segmental defects compared with other treatment modalities.

Effect of absorbable membranes on sandwich bone augmentation

OBJECTIVES

This study was conducted to evaluate the effect of barrier membranes on sandwich bone augmentation (SBA) for the treatment of implant dehiscence defects.

MATERIAL AND METHODS

Twenty-six implant-associated buccal dehiscence defects in 22 patients were treated according to the SBA concept - mineralized human cancellous allograft (inner layer), mineralized human cortical allograft (outer layer) and coverage with barrier membrane. The defects were randomly assigned to the bovine collagen membrane (BME) group; acellular dermal matrix (ADM) group; and no membrane group. Measurements at baseline and 6 months re-entry included defect height (DH: from smooth-rough junction to the most apical part of the defect), defect width (DW: at the widest part of the defect), and horizontal defect depth (HDD: at three locations - smooth-rough junction, middle, and most apical portion of the defect). All measurements were taken from a reference stent. Statistical analyses were performed for comparison of intra- and inter-group comparisons.

RESULTS

All implants placed were successfully osseointegrated. DH at baseline for three groups were not significantly different (P=0.858). Mean % DH reductions for ADM, BME, and control groups at 6 months were 73.9+/-17.6%, 68.1+/-30.1%, and 63.6+/-23.9%, respectively, with no significant difference among the groups (P=0.686). Mean horizontal bone gain, however, was significantly greater for membrane groups (1.7 mm for ADM, 1.6 mm for BME) compared with control group (1 mm) (P=0.044). Implant exposure resulted in significant reduction in total height gain (79.1+/-14.3% vs. 57+/-23.5%, P=0.021).

CONCLUSIONS

Within the limit of this study, it is concluded that SBA technique achieved predictable clinical outcomes. The addition of absorbable membranes enhanced bone gain in thickness compared with membrane-treated sites.

Ridge augmentation by applying bioresorbable membranes and deproteinized bovine bone mineral: a report of twelve consecutive cases

OBJECTIVE

Lateral ridge augmentations are traditionally performed using autogenous bone grafts to support membranes for guided bone regeneration (GBR). The bone-harvesting procedure, however, is accompanied by considerable patient morbidity.

AIM

The aim of the present study was to test whether or not resorbable membranes and bone substitutes will lead to successful horizontal ridge augmentation allowing implant installation under standard conditions.

MATERIAL AND METHODS

Twelve patients in need of implant therapy participated in this study. They revealed bone deficits in the areas intended for implant placement. Soft tissue flaps were carefully raised and blocks or particles of deproteinized bovine bone mineral (DBBM) (Bio-Oss) were placed in the defect area. A collagenous membrane (Bio-Gide) was applied to cover the DBBM and was fixed to the surrounding bone using poly-lactic acid pins. The flaps were sutured to allow for healing by primary intention.

RESULTS

All sites in the 12 patients healed uneventfully. No flap dehiscences and no exposures of membranes were observed. Nine to 10 months following augmentation surgery, flaps were raised in order to visualize the outcomes of the augmentation. An integration of the DBBM particles into the newly formed bone was consistently observed. Merely on the surface of the new bone, some pieces of the grafting material were only partly integrated into bone. However, these were not encapsulated by connective tissue but rather anchored into the newly regenerated bone. In all of the cases, but one, the bone volume following regeneration was adequate to place implants in a prosthetically ideal position and according to the standard protocol with complete bone coverage of the surface intended for osseointegration. Before the regenerative procedure, the average crestal bone width was 3.2 mm and to 6.9 mm at the time of implant placement. This difference was statistically significant (P<0.05, Wilcoxon's matched pairs signed-rank test).

CONCLUSION

After a healing period of 9-10 months, the combination of DBBM and a collagen membrane is an effective treatment option for horizontal bone augmentation before implant placement.

Histomorphometric Analysis of Bone Density in the Maxillary Tuberosity of Cadavers: A Pilot Study

BACKGROUND

Maxillary tuberosities have been widely used as a source of autogenous bone for a variety of oral surgical procedures. However, no previous studies have actually demonstrated the histologic and histomorphometric characteristics of this anatomical region in detail. The aim of this study was to evaluate maxillary tuberosities in cadavers histologically and histomorphometrically.

METHODS

A block section, including the overlying alveolar mucosa, was obtained from a randomly assigned maxillary tuberosity of 20 cadavers (nine females and 11 males). All cadavers were edentulous distal to the second bicuspid teeth, and 14 out of 20 were edentulous distal to the cuspids. A minimum of 35 serial sections were obtained from each cadaver. Description analysis was performed for the presence of either a fibrotic or fatty infiltration of the marrow spaces and thickness and continuity of alveolar bone. Computer-based histomorphometric image analysis of the percentage surface area of bone was also carried out in three sections of each cadaver. Statistical analysis was performed to establish possible differences between genders. The analysis did not control for nutritional status and/or possible systemic or skeletal diseases.

RESULTS

Little variation existed between specimens, regardless of gender, with respect to thickness of oral mucosa overlying the tuberosity. Descriptive bone analysis revealed thin cortical bone and sparse cancellous bone patterns. In addition, the block specimens exhibited no evidence of osteoid or active bone formation, but large marrow spaces infiltrated with loosely organized fibrous connective tissue and/or lipid cells. Histomorphometric analysis demonstrated a mean percentage of vital bone of 24.23% +/- 5.2%. Stratification of the data revealed statistically significant differences in mean percentage of vital bone between genders (27.15% +/- 4.7% for males versus 20.66% +/- 3.4% for females; P = 0.003).

CONCLUSIONS

Within the limitations of this study, maxillary tuberosities seem to mainly consist of marrow spaces, adipose tissue, and a low vital bone profile. Females demonstrated a statistically significant lower amount of vital bone than males. The results suggest that this specific area may not be an ideal source of autogenous bone for grafting purposes in older individuals. However, it is imperative to note that this investigation did not control for nutritional imbalances and skeletal disorders. Further studies are necessary to control all confounding factors.

Early healing pattern of autogenous bone grafts with and without e-PTFE membranes: A histomorphometric study in rats

OBJECTIVE

The aim of this study was to perform quantitative and qualitative analyses of the initial repair pattern of an autogenous bone block graft when covered or not with e-PTFE membranes.

STUDY DESIGN

Sixty male Wistar rats received a bone graft plus an e-PTFE membrane (MB) or just the graft (B). A block graft was harvested from the animal's calvarium and was laid and stabilized on the external cortical area near the angle of the mandible. Descriptive histology and histomorphometric analyses were carried out and the data were analyzed statistically by ANOVA and the Tukey test, with the level of significance set at 5%.

RESULTS

The results for group B showed that there was bone loss during the healing period (B0 = 1.38, B45 = 1.05, F = 7.91 > F(C) = 3.02), that is, the initial volume of the graft decreased in time. Bone tissue loss was about 24%. In contrast, the MB group showed bone tissue gain along the observation period (MB0 = 1.54, MB45 = 2.40, F = 7.91 > F(C) = 3.02), meaning that the total volume of newly formed bone was greater than the original graft area. Bone tissue gain was approximately 55%. MB showed significantly greater bone gain when compared to B (B45 = 1.05, MB45 = 2.40, F = 39.86 > F(C) = 1.90). These significant differences between B and MB could already be observed after 21 days.

CONCLUSIONS

The bone block graft underwent resorption at an early healing stage, while additional new bone formation was observed when the bone graft was covered with an e-PTFE membrane.

Bone formation by enamel matrix proteins and xenografts: an experimental study in the rat ramus

The aim of this study was to evaluate whether the use of enamel matrix proteins with or without the use of deproteinized bovine bone influences bone formation when used as an adjunct to guided bone regeneration (GBR). Twenty rats, divided into four groups of five animals each, were used in this study. Group A1: A hemispherical PTFE capsule was placed empty on the lateral aspect of the mandibular ramus (GBR). At the contralateral side of the jaw, the capsule was filled with an enamel matrix derivative (EMD) before its placement. The healing period was 60 days. Group A2: The animals were treated in the same manner as in Group A1 but with a healing period of 120 days. Group B1: The animals were treated in the same manner as in Group A1 with the difference that deproteinized bovine bone mineral (DBBM) particles were packed in the capsule. At the contralateral side of the jaw, the capsule was filled with a mixture of EMD and DBBM. The healing period was 60 days. Group B2: The same treatment as in B1 but with a healing period of 120 days. The histological analysis revealed that in Groups A1 and A2 newly formed bone was covering a significant part of the empty capsules (GBR). The use of EMD in the capsule did not offer any added benefit to the use of the capsule alone in terms of new bone formation. At Groups B1 and B2, the presence of DBBM and/or EMD did not positively affect the amount of new bone formation. It can be suggested that neither the application of EMD nor the use of DBBM or the combination of EMD and DBBM results in enhanced amounts of bone formation in comparison with the GBR procedure alone.

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

The aim of the study was to compare the long-term stability of membranous and endochondral autogenous bone grafts with or without combined application of guided bone regeneration (GBR). Twenty-five, male, 6-month old, albino rats were used in the study. The animals were divided into four groups (A5, A11, B5 and B11). Group A5 (control): The inferior border of the mandible was exposed in both sides. At one side of the jaw, a calvarial bone graft (baseline -3 x 4 x 0.64 mm) was placed at the inferior border of the mandible and was fixed with a standardized screw-type titanium microimplant. At the contralateral side, an ischiac bone graft (baseline -3 x 4 x 0.87) was transplanted. The healing period was 5 months. Group A11 (control): The animals were treated in the same manner as in Group A5 with the difference that the healing period was 11 months. Group B5 (test): The animals were treated in the same manner as in Group A5 with the difference that an e-PTFE membrane was adapted over the bone graft on each side of the jaw. Group B11 (test): The animals were treated in the same manner as in Group B5 with the difference that 5 months following transplantation the animals were subjected to a second operation and the membranes were removed. The healing period was 11 months. The animals were killed at 5 (Groups A5 and B5) or at 11 months (Groups A11 and B11) following mandibular augmentation and the jaws were defleshed. The width, the length and the thickness/height of the bone graft were evaluated by means of a stereomicroscope. At 5 months, both types of the membrane-treated bone grafts presented increase in all dimensions compared with baseline. However at 11 months, both types of the membrane-treated bone grafts exhibited a decrease in their dimensions which were similar to the baseline measurements. In the control groups, both types of bone graft presented significant resorption both at 5 and at 11 months with the ischiac bone grafts presenting more resorption in width and length than the calvarial bone grafts. It can be concluded that the long-term volume stability of autogenous endochondral and membranous onlay bone grafts combined with GBR is superior to that of autogenous endochondral and membranous onlay bone grafts alone.

Evaluation of gingival blood flow by the use of laser Doppler flowmetry following periodontal surgery. A pilot study

OBJECTIVES

The aim of this pilot study was to evaluate the applicability of laser Doppler flowmetry (LDF) in recording the gingival blood flow following periodontal surgery.

MATERIAL AND METHODS

Five patients suffering from advanced chronic generalized periodontitis were included in the study. After completion of basic periodontal therapy, full-mouth plaque score, bleeding on probing, gingival recession and clinical attachment level were recorded. The upper anterior areas with a pocket probing depth of 6 mm or more were treated with an access flap. LDF recordings were performed in both the buccal and palatal aspect of the operated areas with the aid of an individual acrylic stent at the day of the surgery, prior to local anaesthesia, 3 min following anaesthesia, immediately after the operation and at days 1, 2, 3, 4, 7, 15, 30 and 60 following operation.

RESULTS

Overall, the blood flow decreased immediately following anaesthesia and remained in lower values compared to baseline immediately following operation. The gingival blood flow presented an overall increase in comparison to baseline values until the 7th day following surgery at the buccal and palatal interdental sites, as well as at the alveolar mucosa sites. By the 15th day, as well as at the following observation periods of 30 and 60 days, the gingival blood flow values at the palatal and alveolar mucosa sites were very similar to baseline. Increased blood flow changes were observed at 30 and 60 days following operation at the buccal interdental sites.

CONCLUSION

The results of the present pilot study suggest that the LDF might present clinical applicability in recording changes in gingival blood flow following periodontal surgery.

Effect of GBR in combination with deproteinized bovine bone mineral and/or enamel matrix proteins on the healing of critical-size defects

OBJECTIVES

To evaluate the effect of guided bone regeneration (GBR) in combination with or without deproteinized bovine bone mineral (DBBM) and/or an enamel matrix derivative (EMD) on the healing of critical-size calvarial defects.

MATERIAL AND METHODS

Forty rats were used. In all animals, a standardized critical-size calvarial defect was created surgically. The animals were randomly allocated into 4 groups of 10 animals each. Group A: One calvarial defect was left untreated, while the galeal and the cerebral aspect of the contralateral defect were covered with a bioresorbable membrane (GBR). Group B: One calvarial defect was filled with EMD, while the contralateral defect was treated with GBR and EMD. Group C: One defect was filled with DBBM, while the contralateral defect was treated with combination of GBR and DBBM. Group D: One defect was filled with DBBM combined with EMD, while the contralateral defect was treated with combination of GBR, DBBM and EMD. The healing period was 4 months. Five specimens from each group were macerated and the length, the width and the vertical dimension (thickness) of the remaining defect were evaluated by a stereomicroscope. The remaining specimens in each group were analyzed histologically.

RESULTS

The defects of the macerated specimens that were left untreated or were treated only by EMD, DBBM and combination of EMD and DBBM did not present predictably complete healing of the defects. All the defects where GBR was applied alone or combined with DBBM and/or EMD presented always complete healing (P<0.05). The combined use of GBR with EMD and/or DBBM did not offer any significant advantage above GBR alone in terms of healing of the length and the width of the defect. However, the vertical dimension of the defect was significantly higher (P<0.05) in the GBR-treated specimens of Groups C and D. The histological analysis supported these findings.

CONCLUSION

The predictability of bone formation in critical-size defects depends mainly on the presence or absence of barrier membranes (GBR). The combined use with deproteinized bovine bone mineral and/or enamel matrix proteins did not significantly enhance the potential for complete healing provided by the GBR procedure.