Mauricio G. Araújo

Ridge preservation with the use of Bio-Oss® collagen: A 6-month study in the dog

BACKGROUND In previous short-term studies, it was observed that while the placement of biomaterial in alveolar sockets may promote bone formation and ridge preservation, the graft may in fact also delay healing. AIM The objective of the present experiment was to evaluate the more long-term effect on hard tissue formation and the amount of ridge augmentation that can occur by the placement of a xenogeneic graft in extraction sockets of dogs. MATERIAL AND METHODS Five beagle dogs were used. The third mandibular premolars were hemi-sected. The distal roots were carefully removed. A graft consisting of Bio-Oss collagen was placed in one socket while the contra-lateral site was left without grafting. After 6 months of healing, the dogs were euthanized and biopsies were sampled. From each experimental site, four ground sections - two from the mesial root and two from the healed socket - were prepared, stained and examined under a microscope. RESULTS The placement of Bio-Oss collagen in the fresh extraction socket served as a scaffold for tissue modeling but did not enhance new bone formation. In comparison with the non-grafted sites, the dimension of the alveolar process as well as the profile of the ridge was better preserved in Bio-Oss-grafted sites. CONCLUSION The placement of a biomaterial in an extraction socket may modify modeling and counteract marginal ridge contraction that occurs following tooth removal.

Root-Coverage Procedures for the Treatment of Localized Recession-Type Defects: A Cochrane Systematic Review

BACKGROUND The purpose of this review is to evaluate the effectiveness of different root-coverage procedures in the treatment of recession-type defects. METHODS The Cochrane Oral Health Group Trials Register, Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE were searched for entries up to October 2008. There were no restrictions regarding publication status or the language of publication. Only clinical randomized controlled trials (RCTs) with a duration > or = 6 months that evaluated recession areas (Miller Class I or II > or = 3 mm) that were treated by means of periodontal plastic surgery procedures were included. RESULTS Twenty-four RCTs provided data. Only one trial was considered to be at low risk of bias. The remaining trials were considered to be at high risk of bias. The results indicated a significantly greater reduction in gingival recession and gain in keratinized tissue for subepithelial connective tissue grafts (SCTGs) compared to guided tissue regeneration (GTR) with bioabsorbable membranes (GTR bms). A significantly greater gain in keratinized tissue was found for enamel matrix protein compared to a coronally advanced flap (0.40 mm) and for SCTGs compared to GTR bms plus bone substitutes. Limited data exist on the changes of esthetic conditions as related to the opinions and preferences of patients for specific procedures. CONCLUSIONS SCTGs, coronally advanced flaps alone or associated with other biomaterial, and GTR may be used as root-coverage procedures for the treatment of localized recession-type defects. In cases where root coverage and gain in keratinized tissue are expected, the use of SCTGs seems to be more adequate.

Bio-Oss® Collagen in the buccal gap at immediate implants: a 6-month study in the dog

BACKGROUND following tooth extraction and immediate implant installation, the edentulous site of the alveolar process undergoes substantial bone modeling and the ridge dimensions are reduced. objective: the objective of the present experiment was to determine whether the process of bone modeling following tooth extraction and immediate implant placement was influenced by the placement of a xenogenic graft in the void that occurred between the implant and the walls of the fresh extraction socket. MATERIAL AND METHODS five beagle dogs about 1 year old were used. The 4th premolar in both quadrants of the mandible ((4) P(4) ) were selected and used as experimental sites. The premolars were hemi-sected and the distal roots removed and, subsequently, implants were inserted in the distal sockets. In one side of the jaw, the marginal buccal-approximal void that consistently occurred between the implant and the socket walls was grafted with Bio-Oss Collagen while no grafting was performed in the contra-lateral sites. After 6 months of healing, biopsies from each experimental site were obtained and prepared for histological analyses. RESULTS the outline of the marginal hard tissue of the control sites was markedly different from that of the grafted sites. Thus, while the buccal bone crest in the grafted sites was comparatively thick and located at or close to the SLA border, the corresponding crest at the control sites was thinner and located a varying distance below SLA border. CONCLUSIONS it was demonstrated that the placement of Bio-Oss Collagen in the void between the implant and the buccal-approximal bone walls of fresh extraction sockets modified the process of hard tissue healing, provided additional amounts of hard tissue at the entrance of the previous socket and improved the level of marginal bone-to-implant contact.

Evidence‐based knowledge on the biology and treatment of extraction sockets

OBJECTIVES The fresh extraction socket in the alveolar ridge represents a special challenge in everyday clinical practice. Maintenance of the hard and soft tissue envelope and a stable ridge volume were considered important aims to allow simplifying subsequent treatments and optimizing their outcomes in particular, when implants are planned to be placed. MATERIAL AND METHODS Prior to the consensus meeting four comprehensive systematic reviews were written on two topics regarding ridge alteration and ridge preservation following tooth extraction and implant placement following tooth extraction. During the conference these manuscripts were discussed and accepted thereafter. Finally, consensus statements and recommendations were formulated. RESULTS The systematic reviews demonstrated that the alveolar ridge undergoes a mean horizontal reduction in width of 3.8 mm and a mean vertical reduction in height of 1.24 mm within 6 months after tooth extraction. The techniques aimed at ridge preservation encompassed two different approaches: i) maintaining the ridge profile, ii) enlarging the ridge profile. Regarding timing of implant placement the literature showed that immediate implant placement leads to high implant survival rates. This procedure is primarily recommended in premolar sites with low esthetic importance and favorable anatomy. In the esthetic zone, however, a high risk for mucosal recession was reported. Hence, it should only be used in stringently selected situations with lower risks and only by experienced clinicians. In molar sites a high need for soft and hard tissue augmentation was identified. CONCLUSIONS Future research should clearly identify the clinical and patient benefits resulting from ridge preservation compared with traditional procedures. In addition, future research should also aim at better identifying parameters critical for positive treatment outcomes with immediate implants. The result of this procedure should be compared to early and late implant placement.

Effect of a xenograft on early bone formation in extraction sockets: an experimental study in dog

AIM The aim of this study was to study the effect on early bone formation resulting from the placement of a xenograft in the fresh extraction socket in dogs. MATERIAL AND METHODS Five beagle dogs were used. The distal roots of the third and fourth mandibular premolars were removed. In one quadrant, a graft consisting of Bio-Oss Collagen was placed in the fresh extraction wound, while the corresponding premolar sites in the contra-lateral jaw quadrant were left non-grafted. After 2 weeks of healing, the dogs were perfused with a fixative, the mandibles removed, the experimental sites dissected, demineralized, sectioned in the mesio-distal plane and stained in hematoxyline-eosine. RESULTS The central portion of the non-grafted sockets was occupied by a provisional matrix comprised of densely packed connective tissue fibers and mesenchymal cells. Apical and lateral to the provisional matrix, newly formed woven bone was found to occupy most of the sockets. In the apical part of the grafted sockets, no particles of the xenograft could be observed but newly formed bone was present in this portion of the experimental site. In addition, limited numbers of woven bone trabeculae occurred along the lateral socket walls. The central and marginal segments of the grafted sockets, however, were occupied by a non-mineralized connective tissue that enclosed Bio-Oss particles that frequently were coated by multinucleated cells. CONCLUSIONS The placement of Bio-Oss Collagen in the fresh extraction wound obviously delayed socket healing. Thus, after 2 weeks of tissue repair, only minute amounts of newly formed bone occurred in the apical and lateral borders of the grafted sockets, while large amounts of woven bone had formed in most parts of the non-grafted sites.

Dimension of the facial bone wall in the anterior maxilla: a cone‐beam computed tomography study

OBJECTIVE To determine the thickness of the facial bone wall in the anterior dentition of the maxilla and at different locations apical to the cemento-enamel junction (CEJ). MATERIAL AND METHODS Two-hundred and fifty subjects, aged between 17 and 66 years, with all maxillary front teeth present were included. Written informed consents were obtained. Cone-beam computed tomography scans were performed with the iCAT unit. This examination included all tooth and edentulous sites in the dentition. The images were acquired by means of the iCAT software and processed by a computer. Measurements of the (i) distance between the CEJ and the facial bone crest and (ii) the thickness of the facial bone wall were performed. The bone wall dimensions were assessed at three different positions in relation to the facial bone crest, i.e., at distances of 1, 3, and 5 mm apical to the crest. RESULTS The measurements demonstrated that (i) the distance between the CEJ and the facial bone crest varied between 1.6 and 3 mm and (ii) the facial bone wall in most locations in all tooth sites examined was ≤1 mm thick and that close to 50% of sites had a bone wall thickness that was ≤0.5 mm. CONCLUSION Most tooth sites in the anterior maxilla have a thin facial bone wall. Such a thin bone wall may undergo marked dimensional diminution following tooth extraction. This fact must be considered before tooth removal and the planning of rehabilitation in the anterior segment of the dentition in the maxilla.

Dynamics of Bio-Oss® Collagen incorporation in fresh extraction wounds: an experimental study in the dog

AIM The objective of this experiment was to analyze processes involved in the incorporation of Bio-Oss Collagen in host tissue during healing following tooth extraction and grafting. METHODS Five beagle dogs were used. Four premolars in the mandible ((3)P(3), (4)P(4)) were hemi-sected, the distal roots were removed and the fresh extraction socket filled with Bio-Oss Collagen. The mucosa was mobilized and the extraction site was closed with interrupted sutures. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2 and 4 weeks of healing could be obtained. The dogs were euthanized and perfused with a fixative. Each experimental site, including the distal socket area, was dissected. The sites were decalcified in EDTA, and serial sections representing the central part of the socket were prepared in the mesio-distal plane and parallel with the long axis of the extraction socket. Sections were stained in hematoxylin and eosin and were used for the overall characteristics of the tissues in the extraction socket. In specimens representing 1, 2 and 4 weeks of healing the various tissue elements were assessed using a morphometric point counting procedure. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells positive for tartrate-resistant acid phosphatase activity (TRAP), alkaline phosphatase and osteopontin were identified. RESULTS The biomaterial was first trapped in the fibrin network of the coagulum. Neutrophilic leukocytes [polymorphonuclear (PMN) cells] migrated to the surface of the foreign particles. In a second phase the PMN cells were replaced by multinuclear TRAP-positive cells (osteoclasts). The osteoclasts apparently removed material from the surface of the xenogeneic graft. When after 1-2 weeks the osteoclasts disappeared from the Bio-Oss granules they were followed by osteoblasts that laid down bone mineral in the collagen bundles of the provisional matrix. In this third phase the Bio-Oss particles became osseointegrated. CONCLUSIONS It was demonstrated that the incorporation of Bio-Oss in the tissue that formed in an extraction wound involved a series of different processes.

Socket grafting with the use of autologous bone: an experimental study in the dog

BACKGROUND studies in humans and animals have shown that following tooth removal (loss), the alveolar ridge becomes markedly reduced. Attempts made to counteract such ridge diminution by installing implants in the fresh extraction sockets were not successful, while socket grafting with anorganic bovine bone mineral prevented ridge contraction. AIM to examine whether grafting of the alveolar socket with the use of chips of autologous bone may allow ridge preservation following tooth extraction. METHODS in five beagle dogs, the distal roots of the third and fourth mandibular premolars were removed. The sockets in the right or the left jaw quadrant were grafted with either anorganic bovine bone or with chips of autologous bone harvested from the buccal bone plate. After 3 months of healing, biopsies of the experimental sites were sampled, prepared for buccal-lingual ground sections and examined with respect to size and composition. RESULTS it was observed that the majority of the autologous bone chips during healing had been resorbed and that the graft apparently did not interfere with socket healing or processes that resulted in ridge resorption. CONCLUSION autologous bone chips placed in the fresh extraction socket will (i) neither stimulate nor retard new bone formation and (ii) not prevent ridge resorption that occurs during healing following tooth extraction.

Ridge alterations following grafting of fresh extraction sockets in man. A randomized clinical trial.

OBJECTIVE To evaluate dimensional alterations of the alveolar ridge that occurred following tooth extraction at sites grafted with Bio-Oss(®) Collagen. MATERIAL AND METHODS Twenty-eight subjects with maxillary incisors, canines, and premolars scheduled for extraction were included. The tooth was carefully removed. The patients were randomly assigned to a test or a control group. In the test group patients, Bio-Oss(®) Collagen was placed in the fresh extraction socket while in the controls no grafting was performed. Radiographic examination (cone beam computed tomograms, CBCT) was performed immediately after tooth extraction and socket treatment. Four months later, a new CBCT was obtained. In the radiographs, (i) the distance (mm) between base of the alveolar process (apex) and the buccal and palatal crests was determined, (ii) the outer profile of alveolar process of the experimental sites was outlined, and the cross section of the area (mm(2) ) determined. RESULTS After 4 months of healing, the buccal and to a less extent also the palatal bone plate had become markedly reduced in height. The placement of a biomaterial in the socket failed to prevent resorption of the buccal and palatal bone walls. The cross-sectional area of the control ridge was reduced about 25% and of the test ridge with 3%. CONCLUSION The placement of a xenograft in fresh extraction sockets markedly counteracted the reduction in the hard tissue component of the edentulous sites.

β-tricalcium phosphate in the early phase of socket healing: an experimental study in the dog

OBJECTIVES The aim of this experiment was to analyze processes involved in the incorporation of beta-tricalcium phospate (TCP) particles in host tissue during healing following tooth extraction and grafting. MATERIAL AND METHODS Five beagle dogs were used. Four premolars in the maxilla ((3)P(3), (2)P(2)) were hemi-sected, the distal roots were removed and the fresh extraction socket filled with TCP. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2, and 4 weeks of healing could be obtained. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells that expressed Tratarate resistant acid phosphate, alkaline phosphatase, and osteopontin were identified by the use of markers. RESULTS The porosities of the TCP particles were initially filled with erythrocytes that subsequently were replaced with mineralized bone. Some of the graft material was invaded by mesenchymal and inflammatory cells and disintegrated. Thus, small membrane bound granules appeared in the granulation tissue and the provisional matrix. In the process of hard tissue formation, partly mineralized (modified) TCP particles became surrounded by ridges of woven bone. CONCLUSIONS It was demonstrated that the early healing of an extraction socket that had been grafted with beta-TCP involved (i) the formation of a coagulum that was (ii) replaced with granulation tissue and a provisional matrix in which (iii) woven bone could form. In this process the biomaterial was apparently involved.