Schupbach P

Surface‐modified zirconia implants: tissue response in rabbits

AIM To evaluate the bone tissue response to zirconia implants with three different surface modifications in comparison with the oxidized titanium surface with the goal to optimize osseointegration in terms of strength and speed. MATERIALS AND METHODS A total of 18 rabbits with 143 implants were used. One hundred and twenty-three were threaded zirconia ceramic implants with three different surface topographies and 20 modified titanium oxide implants were controls. Each rabbit received eight implants and sacrificed after 3 weeks. The removal torque test (RTQ) and histology were performed. RESULTS Sixteen out of 18 rabbits completed the study with a total of 110 implants. No statistical significance was observed between the chemical modification implants compared with the topographically modified zirconia implant in terms of interfacial shear strength proven by the RTQ applied. No statistical significance was also observed in the bone-to-implant contact between the zirconia implants and the control oxidized implants. CONCLUSIONS The findings suggest that additional specific chemical modifications of the topographically modified zirconia implants do not seem to enhance the bone-to-implant contact and appear not to increase the interfacial shear strength.

Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model

OBJECTIVES The aim of the present study was to evaluate a Ca-P coated implant surface in a rabbit model. The Ca-P surface (test) was compared to the titanium porous oxide surface (control) in terms of bone-to-implant contact (BIC) and removal torque value. MATERIALS AND METHODS Two hundred and sixteen dental implants were inserted in the tibia and in the femur of 36 rabbits. One hundred and eight were represented by Ca-P oxidized surface implant and other 108 were titanium porous oxide surface modified implants. Each rabbit received six implants. Animals were sacrificed after 2, 4 and 9 weeks of healing. Each group included 12 rabbits. The femoral implant and the proximal implant of the tibia of each animal were subjected to the histologic analysis and the distal implants of the tibia underwent removal torque test (RTQ). RESULTS Histological analysis in terms of BIC and RTQ did not revealed any significant difference between the Ca-P oxidized surface and the oxidized surface at 2 and 4 weeks. At 9 weeks, the oxidized surface demonstrated better results in terms of RTQ in the tibia. CONCLUSION In conclusion, findings from the present study suggested that the Ca-P coating had no beneficial effect in improving bonding strength at the bone-implant interface either at 2, 4 and 9 weeks.

A Prospective, Randomized Controlled Preclinical Trial to Evaluate Different Formulations of Biphasic Calcium Phosphate in Combination With a Hydroxyapatite Collagen Membrane to Reconstruct Deficient Alveolar Ridges

Many patients and clinicians would prefer a synthetic particulate bone replacement graft, but most available alloplastic biomaterials have limited osteogenic potential. An alloplast with increased regenerative capacity would be advantageous for the treatment of localized alveolar ridge defects. This prospective, randomized controlled preclinical trial utilized 6 female foxhounds to analyze the osteogenic impact of different formulations of biphasic calcium phosphate (BCP) in combination with an hydroxyapatite-collagen membrane and their ability to reconstruct deficient alveolar ridges for future implant placement. The grafted sites were allowed to heal 3 months, and then trephine biopsies were obtained to perform light microscopic and histomorphometric analyses. All treated sites healed well with no early membrane exposure or adverse soft tissue responses during the healing period. The grafted sites exhibited greater radiopacity than the surrounding native bone with BCP particles seen as radiopaque granules. The graft particles appeared to be well-integrated and no areas of loose particles were observed. Histologic evaluation demonstrated BCP particles embedded in woven bone with dense connective tissue/marrow space. New bone growth was observed around the graft particles as well as within the structure of the graft particulate. There was intimate contact between the graft particles and newly formed bone, and graft particles were bridged by the newly formed bone in all biopsies from the tested groups. The present study results support the potential of these BCP graft particulates to stimulate new bone formation. Clinical studies are recommended to confirm these preclinical findings.

The Combination of Purified Recombinant Human Platelet-Derived Growth Factor-BB and Equine Particulate Bone Graft for Periodontal Regeneration

BACKGROUND The objective of this study is to evaluate the potential for periodontal regeneration of a critical-sized defect with the application of recombinant human platelet-derived growth factor (rhPDGF-BB) combined with either a particulate equine or a β-tricalcium phosphate (β-TCP) matrix. METHODS Critical-sized intrabony 2-wall defects were created bilaterally on the distal surface of the second premolar and the mesial surface of the first molar in nine hounds. Twelve defects received rhPDGF-BB/equine treatment, 12 defects received rhPDGF-BB/β-TCP treatment, and the remaining 12 sites served as sham-surgery controls. The animals were sacrificed after a 10-week healing period. RESULTS Clinical healing was uneventful without obvious signs of overt gingival inflammation. Histologic and histomorphometric analyses revealed statistically that there were differences among the three groups in terms of new bone formation (P <0.001). The amount of test material for both rhPDGF-BB/equine and rhPDGF-BB/β-TCP groups was comparable, but the amount of newly formed bone was significantly higher (P <0.01) in favor of the rhPDGF-BB/equine group. The amount of new cementum formed for the rhPDGF-BB/equine group (4.8 ± 1.3 mm) was significantly higher (P =0.001) than the sham-surgery control group (1.7 ± 1.9 mm). CONCLUSION Both rhPDGF-BB/equine and rhPDGF-BB/β-TCP have the potential to support the regeneration of the periodontal attachment apparatus.

Vertical ridge augmentation using an equine bone and collagen block infused with recombinant human platelet-derived growth factor-BB: a randomized single-masked histologic study in non-human primates.

BACKGROUND This study tests the effectiveness of hydroxyapatite and collagen bone blocks of equine origin (eHAC), infused with recombinant human platelet-derived growth factor-BB (rhPDGF-BB), to augment localized posterior mandibular defects in non-human primates (Papio hamadryas). METHODS Bilateral critical-sized defects simulating severe atrophy were created at the time of the posterior teeth extraction. Test and control blocks (without growth factor) were randomly grafted into the respective sites in each non-human primate. RESULTS All sites exhibited vertical ridge augmentation, with physiologic hard- and soft-tissue integration of the blocks when clinical and histologic examinations were done at 4 months after the vertical ridge augmentation procedure. There was a clear, although non-significant, tendency to increased regeneration in the test sites. As in the first two preclinical studies in this series using canines, experimental eHAC blocks infused with rhPDGF-BB proved to be a predictable and technically viable method to predictably regenerate bone and soft tissue in critical-sized defects. CONCLUSION This investigation supplies additional evidence that eHAC blocks infused with rhPDGF-BB growth factor is a predictable and technically feasible option for vertical augmentation of severely resorbed ridges.

Recombinant human platelet-derived growth factor BB for reconstruction of human large extraction site defects.

This study investigated the ability of growth factor-enhanced matrices combined with a tenting screw scaffolding system and resorbable membrane to regenerate large alveolar extraction site defects. Eight patients were randomized to treatment either with a bovine or equine matrix mixed in a ratio of 1.0 mL (0.3 mg/mL) recombinant human platelet-derived growth factor BB (rh-PDGF-BB) per gram of xenograft and allowed to absorb for 10 minutes. Tenting screws were used to provide additional support, and the growth factor-enhanced particulate matrix was incrementally placed and condensed into the defect and covered by a resorbable membrane. Reentry surgery after 5 months allowed for trephine core biopsies and implant placement. All sites healed well with evidence of bonelike hard tissue that was confirmed histologically as vital bone around the remaining graft particulate in both treatment groups. The results of this study demonstrate the capability of growth factor-enhanced matrices combined with tenting screws and a resorbable membrane to support the reconstruction of large extraction site defects.

Equine-derived bone mineral matrix for maxillary sinus floor augmentation: a clinical, radiographic, histologic, and histomorphometric case series.

The objective of this proof-of-principle multicenter case series was to examine the bone regenerative potential of a newly introduced equine-derived bone mineral matrix (Equimatrix) to provide human sinus augmentation for the purpose of implant placement in the posterior maxilla. There were 10 patients requiring 12 maxillary sinus augmentations enrolled in this study. Histologic results at 6 months demonstrated abundant amounts of vital new bone in intimate contact with residual graft particles. Active bridging between residual graft particles with newly regenerated bone was routinely observed in intact core specimens. A mean value of 23.4% vital bone formation was observed at 6 months. This compared favorably with previous results using xenografts to produce bone in the maxillary sinus for the purpose of dental implant placement. Both the qualitative and quantitative results of this case series suggest comparable bone regenerative results at 6 months to bovine-derived xenografts.

The Clinical and Histologic Outcome of Dental Implant in Large Ridge Defect Regenerated With Alloplast: A Randomized Controlled Preclinical Trial

A basic tenet of successful osseointegration is that the implant resides in a sufficient quality and quantity of bone to ensure bone contact and thus stabilization. A prospective, randomized controlled preclinical trial was conducted to evaluate the bone-to-implant contact (BIC) when placing implants in bone regenerated by 3 different combinations of biphasic calcium phosphate (BCP). Dental implants were placed into the regenerated ridges of 6 female foxhounds; the ridges were reconstructed with different formulations of BCP in combination with an hydroxyapatite collagen membrane. They were retrieved after 3 months to perform light microscopic and histomorphometric analyses. Implants in each group appeared to be stable and osseointegrated. Light microscopic evaluation revealed tight contacts between the implant threads with the surrounding bone for all 4 groups. The mean BIC ranged from 64.7% to 73.7%. This preclinical trial provided clinical and histologic evidence to support the efficacy of all 3 formulations of BCP to treat large alveolar ridge defects to receive osseointegrated dental implants.

Late Dental Implant Failures Associated with Retained Root Fragments: Case Reports with Histologic and SEM Analysis

Interest has recently developed in the purposeful retention of root fragments with their periodontal apparatus to support bone and soft tissue at immediate implant sites in the esthetic zone. This methodology is designed to avoid bone grafting, connective tissue grafts, and the use of membranes and may have short-term benefits in terms of tissue preservation. However, it is not completely without long-term risks. At times, implants may be unintentionally placed into edentulous sites where root fragments remain. This report presents two cases of long-term failure postloading associated with unintentionally retained root fragments. Histologic evaluation evidenced retained root fragments in close association with dental implants and the surrounding bone. Scanning electron microscopic evaluation revealed that the failed implant surfaces were infiltrated by bacterial deposits and calculus. Clinicians should exercise caution when placing dental implants in sites with retained root fragments, as long-term risks may be associated with this therapy.

The efficacy of mineralized allograft cortical and cancellous chips in maxillary sinus augmentations.

A mixture of mineralized allograft cortical and cancellous chips was used to augment the maxillary sinuses of 10 patients. Eleven sinus augmentation procedures were performed, and 19 bone cores were obtained at reentry after 6 to 7 months. Computed tomography at 6 months postaugmentation demonstrated bone formation in all sites. Light microscopic and histomorphometric evaluation confirmed bone formation at the treatment site that would receive osseointegrated implants to replace the missing maxillary posterior teeth. These encouraging results support the use of a mixture of mineralized allograft cortical and cancellous chips for sinus augmentation.