Histologic Analysis of Alveolar Bone Following Guided Bone Regeneration

Differential effects of clopidogrel and/or aspirin on the healing of tooth extraction wound bone tissue

Introduction

A multitude of variables influence the healing of tooth extraction wounds, and delayed or non-healing extraction wounds might complicate later prosthodontic therapy. In this research, we analyzed the effects of systemic clopidogrel and aspirin alone or in combination on the healing of tooth extraction wounds in mice in order to provide experimental evidence for the healing of extraction wounds in patients who are clinically treated with the two medicines.

Methods

7-week-old ICR mice were randomly divided into four groups: control group (CON), clopidogrel group (CLOP), aspirin group (ASP), and clopidogrel combined with aspirin group (CLOP + ASP); left upper first molar was extracted, after which mice in 1 week of adaptive feeding, CLOP/ASP/CLOP + ASP groups were respectively administered with clopidogrel (10 mg/kg/d), aspirin (15 mg/kg/d), clopidogrel (10 mg/kg/d)+aspirin (15 mg/kg/d), and the control group was given an equal amount of 0.9% saline by gavage. Mice in each group were euthanized at 14 and 28 days postoperatively, and the maxilla was extracted. The tissues in the extraction sockets were examined using MicroCT and sectioned for HE staining, Masson staining, and TRAP staining, and immunohistochemistry staining (for TRAP, RANKL and osteoprotegerin).

Results

MicroCT analysis showed that at day 14, BS/BV was significantly lower in CLOP and CLOP + ASP groups compared to control and ASP groups, while BV/TV, Tb.Th was significantly higher. At day 28, BV/TV was significantly higher in the CLOP + ASP group compared to the CLOP group, with p < 0.05 for all results. HE staining and Masson trichrome staining findings revealed that at day 28, the mesenchyme in the bone was further decreased compared to that at day 14, accompanied with tightly arranged and interconnected bone trabeculae. In the quantitative analysis of Masson, the fraction of newly formed collagen was significantly higher in the CLOP group in comparison with that in the CON group (p < 0.05). At day 14, the ASP group had substantially more TRAP-positive cells than the CLOP and CLOP + ASP groups (p < 0.05). In immunohistochemical staining, RANKL expression was found to be significantly higher in the ASP group than those in the other three groups at day 28 (p < 0.05); OPG expression was significantly higher in the CLOP group and the CLOP + ASP group compared with that at day 14, and was higher than that in the ASP group at day 14 and day 28. OPG/RANKL was significantly higher in the CLOP and the CLOP + ASP groups than in the ASP group (p < 0.05).

Conclusion

Clopidogrel alone promotes osteogenesis in the extraction wound, whereas aspirin alone inhibits alveolar bone healing. When the two drugs were combined, the healing effect of the extraction wound was more similar to that of the clopidogrel alone group. These results indicated that clopidogrel could promote the healing of the tooth extraction wound, and neutralize the adverse effect of ASP on osteogenesis when the two drugs were used in combination.

Clinical and Biological Validation of an Allogeneous Cancellous Bone Block for Alveolar Maxillary Ridge Reconstruction: A Case Series

This exploratory case series clinically and histologically investigated the performance of allogeneic cancellous freeze-dried bone allograft (FDBA) bone blocks (Maxgraft®) for the lateral augmentation of local alveolar defects in the posterior maxilla as part of two-staged implant therapy. Five patients receiving eight implants 5 months after block augmentation with a follow-up period of up to 3 years were documented and analyzed. Horizontal alveolar dimensions before and 5 months after block augmentation were quantified using CBCT. Radiographic marginal bone level changes were quantified at implant placement, loading, and 1 year post-placement. Graft integration and resorption were histologically qualitatively evaluated from core biopsies retrieved at implant placement. Block augmentations resulted in a pronounced horizontal median bone gain of 7.0 (5.5 to 7.8) mm. Marginal implant bone levels in block-augmented bone remained constant over the 1 year follow-up period. Block grafts appeared histologically well integrated. Histologic analysis also revealed signs of progressive resorption and new bone formation at the lateral aspects of the grafts. The results of this case series support using Maxgraft® cancellous FDBA blocks as suitable materials for the lateral augmentation of local alveolar defects.

[Efficacy of two barrier membranes and deproteinized bovine bone mineral on bone regeneration in extraction sockets: A microcomputed tomographic study in dogs]

OBJECTIVE

To evaluate the effect of two barrier membranes [multilaminated small intestinal submucosa (mSIS) and bioresorable collagen membrane (Bio-Gide)] combined with deproteinized bovine bone mineral Bio-Oss on guided bone regeneration through a canine extraction sockets model.

METHODS

The distal roots of 18 premolars of the Beagle' s bilateral maxillary and mandibular were removed, and 18 extraction sockets were obtained. They were randomly divided into 3 groups, and the following procedures were performed on the sockets: (1) filled with Bio-Oss and covered by mSIS (mSIS group), (2) filled with Bio-Oss and covered by Bio-Gide (BG group), (3) natural healing (blank control group). Micro-computed tomograph (Micro-CT) was performed 4 and 12 weeks after surgery to eva-luate the new bone regeneration in the sockets of each group.

RESULTS

The postoperative healing was uneventful in all the animals, and no complications were observed through the whole study period. Micro-CT analysis showed that the new bone fraction in the mSIS group and the BG group was significantly higher than that in the blank control group at the end of 4 weeks and 12 weeks (P < 0.05), and more new bone fraction was observed in the mSIS group than in the BG group, but the difference was not statistically significant (P>0.05). The new bone fraction of coronal third part of the socket in the mSIS group and BG group at the end of 4 weeks were significantly higher than that of the middle and apical third part of each group (P < 0.05). The values of bone mineral density were similar at 4 weeks in all the groups (P>0.05), but were significantly higher than that in the control group at the end of 12 weeks (P < 0.05). The bone morphometric analysis showed that the trabecular number and trabecular spacing were significantly better in the mSIS group and the BG group than in the control group at the end of 4 weeks and 12 weeks (P < 0.05), while the value in the mSIS group was slightly higher than in the BG group, but the difference was not statistically significant (P>0.05). The difference in trabecular thickness between all the groups was not statistically significant (P>0.05).

CONCLUSION

mSIS membrane as a barrier membrane combined with deproteinized bovine bone mineral can enhance new bone formation in canine extraction sockets, similar to Bio-Gide collagen membrane.

Alveolar Ridge Augmentation Around Exposed Mandibular Dental Implant With Histomorphometric Analysis

INTRODUCTION

Alveolar ridge augmentation either before or during implant placement is a predictable procedure under certain conditions. A major complication during the healing phase is incision line opening and membrane exposure, which may result in reduced bone gain and reduced implant survival. This case report describes alveolar bone regeneration around three dental implants despite membrane exposure that developed during healing post-surgically.

CASE PRESENTATION

A 72-year-old female presented requesting dental implants to replace tooth numbers 18, 19, and 20. A cone-beam computed tomography (CBCT) scan showed loss of horizontal and vertical ridge dimensions. All implants were placed with a variable degree of implant thread exposure on their buccal surfaces, ranging from 3 to 4.5 mm. Simultaneous bone grafting was performed using freeze dried bone allograft and deproteinized bovine bone mineral that was covered by a d-PTFE membrane that was secured with tacking screws. Primary closure was obtained, and flaps were sutured. Three weeks post-surgically, membrane exposure occurred. Exposure was monitored and patient was instructed to follow strict oral hygiene instructions around the exposed membrane. Membrane exposure gradually increased without infection and was removed at 16 weeks. Membrane removal revealed dense fibrous tissues covering all implant surfaces. At the second stage surgery, new bone was seen covering all the implants coronal to the cover screws. A trephine core biopsy specimen revealed significant new bone formation and connective tissue around any residual grafted bone.

CONCLUSION

d-PTFE membrane exposure does not necessarily lead to adverse healing outcomes for alveolar ridge augmentation if handled properly with close patient follow-up.

Bone Augmentation of Peri-Implant Dehiscence Defects Using Multilaminated Small Intestinal Submucosa as a Barrier Membrane: An Experimental Study in Dogs

Objective

The aim of the study is to evaluate the effects of multilaminated small intestinal submucosa (mSIS) combined with bone substitute material to repair peri-implant defects during guided bone regeneration procedures.

Methods

Twelve implants were placed in bilateral lower premolars of three beagle dogs, and a peri-implant buccal bone defect (3 mm width and 4 mm height) was created at each implant site. A total of 12 sites were filled with a particulate bone substitute material and then randomly divided into three treatment groups: covered by mSIS membrane (mSIS group), covered by collagen membrane (BG group), and no treatment (control group), each group of four sites. After 12 weeks of healing, all of the animals were euthanized and dissected blocks were obtained for micro-computed tomography (micro-CT) and histological analyses.

Results

Micro-CT results revealed similar horizontal width of augmented tissue and new bone formation between mSIS and BG groups (P < 0.05). Histological analyses revealed that the differences in horizontal widths of newly formed bone and bone-to-implant contact between mSIS and BG groups were not significant (P > 0.05). All of these parameters were significantly different from those in the control group (P < 0.05).

Conclusions

These findings confirmed that mSIS combined with the bone substitute material enhanced bone regeneration in peri-implant defects, in a manner similar to that of a collagen membrane.

Case presentation of two patients using diagonal platform-switched double implants for maxillary single-first-molar replacement as the alternative of a single-tooth implant

A single-tooth implant restoration is generally performed for maxillary single-first-molar replacement. If the interdental space between the second premolar and the second molar is large enough, a double-implant placement can be performed to avoid creating mesiodistal cantilever and to distribute occlusal loading forces.

If there is not adequate space for a double-implant placement to be performed mesiodistally along the crest of the alveolar ridge line, they should be placed along a diagonal line offset lingually to increase the space. This procedure has two primary advantages. First, greater stability is provided by a double-implant placement. Resistance to lateral forces (palatal-buccal) is much stronger than two implants placed along the alveolar crest ridge line. Residual palatal and buccal bone can provide support against occlusal forces, provided that there is adequate residual bone in these regions.

If anatomical conditions are favorable, the placement of two diagonal implants in the palatal and buccal residual bones can be a rational procedure.

We report on two typical patients. The progress of these patients was followed using computed tomography for 7 and 6 years, respectively.

Enhanced bone regeneration with a novel synthetic bone substitute in combination with a new natural cross-linked collagen membrane: radiographic and histomorphometric study

OBJECTIVES

4Bone is a fully synthetic bioactive bone substitute composed of 60% hydroxyapatite (HA) and 40% beta-tricalcium phosphate (ß-TCP). This study aimed to investigate the effect of resorbable collagen membranes (RCM) on critical size defects in rabbit tibiae filled with this novel biphasic calcium phosphate at 15, 30, 45, and 60 days by radiological and histomorphometric analysis.

MATERIAL AND METHODS

Three critical size defects of 6 mm diameter were created in both tibiae of 20 New Zealand rabbits and divided into three groups according to the filling material: Group A (4Bone), Group B (4Bone plus RCM), and Group C (unfilled control group). At each of the four study periods, five rabbits were sacrificed. Anteroposterior and lateral radiographs were taken. Samples were processed for observation under light microscopy.

RESULTS

At the end of treatment, radiological analysis found that cortical defect closure was greater in Group B than Group A, and radiopacity was clearly lower and more heterogeneous in Group A cortical defects than in Group B. There was no cortical defect closure in Group C. Histomorphometric evaluation showed significant differences in newly formed bone and cortical closure in Group B compared with Groups A and C, with the presence of higher density newly formed bone in cortical and medullar zones.

CONCLUSIONS

Biphasic calcium phosphate functioned well as a scaffolding material allowing bone ingrowth and mineralization. The addition of absorbable collagen membranes enhanced bone gain compared with non-membrane-treated sites. This rabbit study provides radiological and histological evidence confirming the suitability of this new material for guided tissue regeneration of critical defects.

Experimental model of bone response to collagenized xenografts of porcine origin (OsteoBiol® mp3): a radiological and histomorphometric study

BACKGROUND

Adequate alveolar ridges are fundamental to successful rehabilitation with implants. There are diverse techniques for reconstructing atrophied ridges, of which bone substitute grafts is one possibility.

PURPOSE

The aim of this study was to carry out radiological and histomorphometric evaluations of bone response to collagenized porcine bone xenografts over a 4-month period following their insertion in rabbits' tibiae.

MATERIAL AND METHODS

Twenty New Zealand rabbits were used. Twenty collagenized porcine bone xenografts (Osteobiol® mp3, Tecnoss Dental s.r.l., Torino, Italy), in granulated form of 600 to 1,000 µm, were inserted in the proximal metaphyseal area of the animals' tibiae and 20 control areas were created. Following implantation, the animals were sacrificed in four groups of five, after 1, 2, 3, and 4 months, respectively. Radiological and histomorphometric studies were made.

RESULTS

After 4 months, radiological images revealed bone defects with a decrease in graft volume and the complete repair of the osseous defect. No healed or residual bone alterations attributable to the presence of the implants were observed. Histomorphometric analysis at 4 months found mean values for newly formed bone, residual graft material, and non-mineralized connective tissue of 25.4 ± 1.8%, 36.37 ± 3.0%, and 38.22 ± 2.5%, respectively. There were no statistical differences in the length of cortical formation with collagenized porcine xenograft (98.9 ± 1.1%) compared with the control samples (99.1 ± 0.7%) at the end of the study period.

CONCLUSIONS

The biomaterial used proved to be biocompatible, bioabsorbable, and osteoconductive and as such, a possible bone substitute that did not interfere with the bone's normal reparative processes.

Ossification of a collagen membrane cross-linked by sugar: a human case series

BACKGROUND

Collagen membranes cross-linked by glycation (GLYM) for guided bone regeneration (GBR) and guided tissue regeneration (GTR) are used extensively with proven safety and efficacy. Complete GLYM ossification, when placed in contact with bone, was described in a canine jaw model, suggesting that GLYM may serve as an ossification substrate. The purpose of this case series was to histologically evaluate GLYM in GBR procedures in humans.

METHODS

We retrospectively selected seven consecutive patients with implant-related bony defects who underwent GBR with GLYM. Six defects had bone grafts, and one had a barrier alone. Selection criteria were primary closure upon post-surgical examination and tissue that was 2- to 3-mm thick over the implant's cover screw. Tissue was removed when the implants were uncovered after 20 to 29 weeks. Decalcified sections were stained and analyzed under light microscopy.

RESULTS

In five of seven specimens, GLYM was identified and preserved its barrier effect. The mean membrane thickness was 0.17 +/- 0.054 mm. In two cases, the bone grafts under the membrane were embedded in new bone, whereas in five cases, they were embedded in fibrous connective tissue. Formation of new dense bone was observed along the side of the membrane facing the original bone, and various degrees of membrane ossification were evident in all five cases.

CONCLUSIONS

GLYM maintained its barrier effect in five of seven cases for 25 weeks and induced dense new bone along its interface with underlying tissues. To the best of our knowledge, this is the first report on GLYM ossification in humans with direct mineral apposition on glycated collagen and suggests a new concept of tissue-integrated active barriers.

Ultrastructural and histomorphometric alterations of rat jaw bones after experimental induction of lathyrism

OBJECTIVE

The aim of this study was to investigate the effect of beta-aminopropionitrile (beta-APN), present in Lathyrus sativus (L. sativus) seeds consumed in drought prone areas, on the maxillary and mandibular bones of rats.

DESIGN

Eighteen rats were used; they were divided into experimental group (12 rats) and a control group (6 rats). In the experimental group, lathyrism was induced by a once daily subcutaneous administration of beta-APN at a dose of 5mg in 0.4ml distilled water per 100g of body weight for 40 days. The specimens were examined histologically, histomorphometrically and ultrastructurally.

RESULTS

Histopathological examination of lathyritic rats showed that both mandible and maxillae were significantly affected. Irregular bone trabeculae with wide medullary cavities and abundant marrow spaces were observed. Focal resorptive areas lined with osteoclasts were also present. Histomorphometric analysis showed a decrease in the area percentage of bone in lathyritic rats as compared to the control. This decrease was statistically significant only in the mandible (p=0.018). Moreover, a significant increase in the number of osteoclasts (p=0.014, 0.012) and resorptive bays (p=0.013, 0.002) was detected in the maxillae and mandible of the experimental group, respectively. Ultrastructurally, there was a significant difference in the microarchitecture of the collagen fibres in lathyritic rats compared to the control. The collagen fibres in the lathyritic group appeared disorganized, fewer in number and more spaced.

CONCLUSIONS

This study provided evidence for lathyritic disturbances in bone architecture. These disturbances are likely to affect mineralization and bone strength as well.

Implant Zones of the Jaws: Implant Location and Related Success Rate

The article demonstrates the factors of importance in the early and late failures of dental implants based on literature review. An implant location is one of many factors that can influence a success or failure of dental implants. The author identifies and describe four alveolar jaw regions--functional implant zones--with unique characteristics of anatomy, blood supply, pattern of bone resorption, bone quality and quantity, need for bone grafting and other supplemental surgical procedures, and a location-related implant success rate. The article discusses predisposing factors that can lead to early implant failures in different jaw zones. An implant location is investigated as one of these factors. A prior history of trauma to premaxillary region is described in the context of implant success in anterior maxilla. This zone is being referred by the author as the "traumatic zone." The challenges of mandibular posterior implant reconstruction are presented in the context of blood supply to the mandible. A deficiency of vascularization in this region, especially in elderly and edentulous patients, lead the author to refer to this zone as the "ischemic zone." The concept of relative ischemia of the posterior mandible that can develop with age and tooth loss is discussed. A thorough understanding of specifics of each functional implant zone should help to improve successes and prevent failures of dental implants.

Histologic and Histomorphometric Evaluation of Alveolar Ridge Augmentation Using Bone Grafts and Titanium Micromesh in Humans

BACKGROUND

Recently, the use of titanium micromesh for alveolar bone augmentation has drawn interest; however, only limited histologic data are available on the quality of the bone regenerated. Therefore, this study compared the use of 100% intraoral autogenous bone to a combination of intraoral autogenous bone (70%) and bovine porous bone mineral (BPBM) (30%) for alveolar ridge augmentation with titanium micromesh histologically and histomorphometrically.

METHODS

Twelve partially edentulous patients required alveolar bone augmentation before implant insertion because of ridge resorption. The defect sites, six in the maxilla and six in the mandible, were reconstructed with particulate autologous bone (control group, N = 6) or a mixture of autologous bone and BPBM (test group, N = 6) in combination with titanium micromesh. Core biopsies were taken from the defect sites 8 to 9 months after grafting at the time of implant insertion.

RESULTS

Newly formed compact bone with a well-organized lamellar pattern was identified in all specimens. In the samples taken from the test group, the BPBM particles were surrounded completely by newly formed bone with no signs of resorption. The mean total bone volume was 62.38% +/- 13.02% in the control group and 52.88% +/- 11.47% in the test group. The soft tissue volume was 37.61% +/- 13.02% and 29.96% +/- 12.58%, respectively, and the residual BPBM volume was 17.15% +/- 2.72% in the test group. No statistical difference was observed in the histologic parameters evaluated, irrespective of graft type and site (P >0.05).

CONCLUSION

Within the limits of this study, BPBM (30%) in combination with autogenous bone (70%) did not yield a lower percentage of new bone formed compared to autogenous bone alone in ridge augmentation with titanium micromesh.

Ossification of a novel cross-linked porcine collagen barrier in guided bone regeneration in dogs

BACKGROUND

Collagen membranes for guided bone regeneration (GBR) and guided tissue regeneration (GTR) are used extensively as bioabsorbable barriers. Cross-linking of collagen increases its biodurability and enables the control of its degradation kinetics and barrier function. A novel cross-linking technology was used to produce a porcine type I collagen membrane (GLYM). The purpose of this study was to evaluate the safety, efficacy, and degradation kinetics of GLYM compared to a non-cross-linked bilayer type I and III porcine collagen membrane (BCM) in surgically created defects in dogs.

METHODS

After tooth extraction, two mandibular bilateral critical size defects were created in 12 beagle dogs that were randomly assigned to one of five groups: GLYM + bovine bone mineral (BBM), BCM + BBM, BBM alone, sham-operated, or GLYM alone. Dogs were euthanized after 8, 16, and 24 weeks, and sites were prepared for qualitative, semiquantitative, and quantitative light microscopy analyses.

RESULTS

Membrane-protected sites displayed bone filling between the BBM particles with almost complete restoration of the original ridge morphology that increased with time up to 16 weeks and remained unchanged at 24 weeks. Both membranes showed marked degradation within 16 to 24 weeks, with BCM inconsistency that was undetectable in one of four sites at 8, 16, and 24 weeks. Membrane ossification was observed in all GLYM sites and in only one BCM site, which progressed with time to 24 weeks. Bone increased by approximately 1 mm on the lingual side, where the GLYM membrane was in direct contact with bone.

CONCLUSIONS

Both membranes were safe and effective in supporting bone regeneration in critical size alveolar ridge defects in dogs and completely degraded within 24 weeks with marked BCM inconsistency. In areas of direct contact with bone, all GLYM sites were progressively ossified with time and augmented the original alveolar ridge. To the best of our knowledge, this is the first report of complete ossification of a collagen barrier membrane in GBR procedures.

Comparison of bone grafting materials in human extraction sockets: clinical, histologic, and histomorphometric evaluations

PURPOSE

Although there are a number of bone replacement graft materials that are currently available for clinical use, there are few studies that directly compare efficacy among graft treatments before implant placement. The purpose of this report was to compare 3 bone replacement graft materials (PepGen P-15 228 FLOW [DENTSPLY Friadent CeraMed, Lakewood, CO], Puros [Zimmer Dental, Carlsbad, CA], and C-Graft 228 [Clinician's Preference, Golden, CO]) for bone formation by clinical, histologic, and histomorphometric evaluation.

MATERIALS AND METHODS

In this prospective, intraoral pilot study, 13 maxillary sockets in 2 patients (both smokers) were grafted immediately after tooth extraction with C-Graft 228, Puros, or PepGen P-15 228 FLOW (containing additional PepGen P-15 228 particles; FLOW PUTTY). After 4 months, bone cores were retrieved and analyzed histologically.

RESULTS

PepGen P-15 228 FLOW PUTTY produced a significantly (P <0.01) higher amount of vital bone than C-Graft 228 or Puros. The amount of vital bone for FLOW PUTTY was 12-fold higher than for C-Graft 228 and 4-fold higher than Puros. Of 7 FLOW PUTTY treated sites, 7 showed >14% vital bone versus 0 of 3 C-Graft 228 and 0 of 3 Puros treated sites. FLOW PUTTY treated sites showed new vital bone between particles of residual graft. C-Graft 228 treated sites showed residual particles in a background of connective tissue with very little bone. Puros treated sites showed nonvital bone particles in a background of connective tissue, with some new vital bone forming around the nonvital bone.

CONCLUSION

PepGen P-15 228 FLOW PUTTY produced significantly greater vital bone as compared to Puros and C-Graft 228 after 4 months. A larger clinical study is required to confirm these results.