Bone healing around implants placed in a jaw defect augmented with Bio-Oss. An experimental study in dogs

The present experiment was carried out to study some tissue reactions around implants that were placed in an edentulous ridge which had been augmented with deproteinized natural bovine cancellous bone mineral. In 4 male beagle dogs, the premolars in the right side of the mandible were extracted and a large buccal ridge defect was created by mechanical means. The bone plate at the lingual aspect of the defect was left intact. 5 months later, the distal 2/3 of the defect area was augmented with Bio‐Oss^® (Geistlich Sons Ltd, Wolhusen, Switzerland) mixed with a fibrin sealer (Tisseel^®, Immuno AG, Vienna, Austria). After 3 months of healing, 3 fixtures (Astra Tech AB, Mölndal, Sweden; TiO‐blast; 8×3.5 mm) were installed in the mandible; 2 were placed in the augmented portion and 1 was placed in the non‐augmented portion of the defect. After a healing period of 3 months, abutment connection was performed and a plaque control period initiated. 4 months later, the dogs were sacrificed and each implant region was dissected. The tissue samples were dehydrated, embedded in plastic, sectioned in the bucco‐lingual plane and examined in the light microscope. It was observed that osseointegration failed to occur to implant surfaces within an alveolar ridge portion previously augmented with Bio‐Oss^®. In the augmented portion of the crest, the graft particles were separated from the host tissue as well as from the implant by a well‐defined connective tissue capsule. Although the lingual aspect of all fixtures (test and control) was in contact with hard tissue at the time of installation, after 4 months of function, a deep vertical bone defect frequently had formed at the lingual surface of the implants. It was concluded that in this model (i) Bio‐Oss^® failed to integrate with the host bone tissue and (ii) no osseointegration occurred to the implants within the augmented portion of the crest.     

Oral implants placed in bone defects treated with Bio‐Oss®, Ostim®‐Paste or PerioGlas: an experimental study in the rabbit tibiae

Objectives: To compare the histological features of bone filled with Bio‐Oss^®, Ostim‐Paste^® or PerioGlas placed in defects in the rabbit tibiae by evaluating bone tissue composition and the integration of titanium implants placed in the grafted bone. Material and methods: Two cylindrical bone defects, about 4 mm in diameter and 6 mm in depth, were created in the tibiae of 10 rabbits. The defects were filled with either Bio‐Oss^®, PerioGlas, Ostim^®‐Paste or left untreated, and covered with a collagen membrane. Six weeks later, one titanium sandblasted and acid‐etched (SLA) implant was inserted at the centre of each previously created defect. The animals were sacrificed after 6 weeks of healing. Results: Implants placed in bone previously grafted with Bio‐Oss^®, PerioGlas or Ostim^®‐Paste obtained a larger extent of osseointegration, although not statistically significant, than implants placed in non‐grafted bone. The three grafting materials seemed to perform in a similar way concerning their contribution towards implant osseointegration. All grafting materials appeared to be osteoconductive, thus leading to the formation of bridges of mineralized bone extending from the cortical plate towards the implants surface through the graft scaffold. Conclusions: Grafting with the above‐mentioned biomaterials did not add any advantage to the osseointegration of titanium SLA implants in a self‐contained defect.     

Effect of grafting materials on osseointegration of dental implants surrounded by circumferential bone defects. An experimental study in the dog

Aims: This study was designed to evaluate the effect of gap width and graft placement on bone healing around implants placed into simulated extraction sockets in the mandibles of four beagle dogs. Materials and methods: Four Ti‐Unite^® implants (13 mm × 3.3 mm) were placed on each side of the mandible. Three implants were surrounded by a 1.35 mm circumferential and a 5 mm deep gap around the coronal portion of the implants. A fourth implant was inserted conventionally into both sides of the mandibles as a positive control. The gaps were filled with either Bio‐Oss^®, autogenous bone or with a blood clot alone. The study design was balanced for animal, side and modality. Ground sections were prepared from biopsies taken at 3 months, and computer‐aided histometric measurements of bone/implant contact and area of bone within threads were made for the coronal 5 mm. Data were analysed using analysis of variance. Results: The mean bone/implant contact was 9.8 mm for the control and ranged from 9.3 to 11.3 mm for the three test modalities. The corresponding values for area within threads were 1 mm² and 1–1.2 mm². Modality had a significant effect on both bone/implant contact (F=16.9; P<0.0001) and area within threads (F=16.7; P<0.0001). Conclusion: The results of this study suggest that both autogenous bone graft and Bio‐Oss^® played an important role in the amount of hard tissue fill and osseointegration occurring within marginal bone defects around implants.     

The effects of bone grafting material and a collagen membrane in the ridge splitting technique: an experimental study in dogs

Objectives: This study was designed to evaluate the effect of bone graft materials and collagen membranes in ridge splitting procedures with immediate implant placement using a dog model. Materials and methods: Mandibular premolars were extracted in five beagle dogs. After 3 months, ridge splitting and placement of three OsseoSpeed^? implants were performed bilaterally. The gaps between the implants were allocated according to the following eight treatment modalities; Group 1(no graft), Group 2 (autogenous bone), Group 3 (Bio‐Oss^® Collagen), Group 4 (Bio‐Oss^®), Group 5 (no graft+BioGide^®), Group 6 (autogenous bone+BioGide^®), Group 7 (Bio‐Oss^® Collagen+BioGide^®), and Group 8 (Bio‐Oss^®+BioGide^®). The dogs were sacrificed after 8 or 12 weeks and the specimens were analyzed histologically and histometrically. Results: The gaps between the implants were filled with the newly formed bone, irrespective of which of the eight grafting techniques was used. Group 1 revealed a significantly lower percentage of bone‐to‐implant contact (BIC) than Group 5 at 8 and 12 weeks (P<0.05). Group 1 showed the most prominent marginal bone loss (MBL) at 12 weeks (P<0.05). Regarding the use of membranes, Groups 1 and 2 showed significantly more MBL than Groups 5 and 6 at 12 weeks (P<0.05). Conclusions: After ridge splitting, if the gaps between implants were grafted or covered with collagen membranes, a higher percentage of BIC was obtained. Based on our results, we suggest that the use of bone graft materials and/or collagen membranes is better for the prevention of MBL after ridge splitting procedures. To cite this article:
Han J‐Y, Shin S‐I, Herr Y, Kwon Y‐H, Chung J‐H. The effects of bone grafting material and a collagen membrane in the ridge splitting technique: an experimental study in dogs.
Clin. Oral Impl. Res. xx , 2011; 000–000
doi: 10.1111/j.1600‐0501.2010.02127.x     

Sinus augmentation analysis revised: the gradient of graft consolidation

Objective: Graft consolidation follows a gradient that reflects the properties of bone substitutes at sites of sinus augmentation. Here we present an analytical method to investigate the process of graft consolidation taking the distance from the maxillary host bone into account. Material and methods: We therefore evaluated histological specimens, 6 and 12 weeks after the sinus of minipigs was augmented with Bio‐Oss^®, a deproteinized bovine bone mineral, and Ostim^®, an aqueous paste of synthetic nanoparticular hydroxyapatite. A curve was drawn that represents the changes in histomorphometric parameters within a given distance from the maxillary host bone. Results: Based on this curve, three regions of interest were defined: R1 (0–1 mm) the bridging distance where new bone is laid onto the host bone, R2 (2–3 mm) a region of osteoconduction where new bone exclusively grows on the biomaterial, R3 (4–5 mm) and a region of osteoconduction where bone formation has reached its maximal extension. Qualitative and quantitative analysis of the three regions can reveal differences in graft consolidation, depending on the bone substitutes and the observation period [Bone volume (BV) per tissue volume after 6 weeks: R1: 19±8.4% for Bio‐Oss^® and 42.9±13.2% for Ostim^® (P=0.03), R2: 3±2.4% for Bio‐Oss^® and 14.7±9.5% for Ostim^® (P=0.03), R3: 5±4.1% for Bio‐Oss^® and 5.3±5.3% for Ostim^® (P=0.86). BV per tissue volume after 12 weeks: R1: 38.0±13.3% for Bio‐Oss^® and 53.3±6.6 for Ostim^® (P=0.04), R2: 14±12.2 for Bio‐Oss^® and 26.4±11 for Ostim^® (P=0.18), R3: 6.6±7 for Bio‐Oss^® and 10.7±5.8 for Ostim^® (P=0.32) after 12 weeks]. Conclusion: Based on the graft consolidation gradient, the impact of bone substitutes to modulate the process of bone formation and the kinetic of degradation within a distinct region of the augmented sinus can be investigated.     

Maxillary sinus augmentation using xenogenic bone substitute material Bio-Oss in combination with venous blood. A histologic and histomorphometric study in humans

The aim of the present study was to evaluate bone formation following maxillary sinus augmentation using bovine bone substitute material Bio‐Oss^® in combination with venous blood by means of histologic and histomorphometric examination of human biopsies. This involved a total of 15 sinus floor elevation procedures being carried out on 11 patients (average age of 49.6 years) according to the technique described by Tatum (1986). The subantral sinus cavity was augmented using bovine apatite combined with venous blood. After an average healing phase of 6.8 months, trephine burrs were used to take 22 bone biopsies from the augmented sinus region. Then 38 Brånemark^® implants were inserted in both the osteotomies resulting from bone sampling and in regular sites in the augmented posterior maxilla. Histomorphometric analysis of ground sections from the bone biopsies prepared according to the standard method of Donath & Breuner (1982) produced an average percentage of newly‐formed bone of 14.7% (±5.0%) and a proportion of residual xenogenic bone substitute material of 29.7% (±7.8%). Some 29.1% (±8.1%) of the surface of the Bio‐Oss^® granulate was in direct contact with newly‐formed bone. Histologically, newly‐developed bone became evident, partly invaginating the particles of apatite and forming bridges in the form of trabeculae between the individual Bio‐Oss^® particles. Despite the absence of osteoclastic activity, the inward growth of bone indicates slow resorption of the xenogenic bone graft material. When the implants were uncovered, after an average healing phase of 6 months, 4 of the 38 implants had become loose. Of these 4 implants, 1 had to be subsequently explanted, while the others remained as “sleeping implants” and were not included in the implants superstructure. Thus, the resulting clinical survival rate, prior to prosthetic loading, was 89.5%.     

Guided bone generation in a rabbit mandible model after periosteal expansion with an osmotic tissue expander

Objectives: To evaluate the space‐maintaining capacity of titanium mesh covered by a collagen membrane after soft tissue expansion on the lateral border of the mandible in rabbits, and to assess bone quantity and quality using autogenous particulate bone or bone‐substitute (Bio‐Oss^®), and if soft tissue ingrowth can be avoided by covering the mesh with a collagen membrane. Material and methods: In 11 rabbits, a self‐inflatable soft tissue expander was placed under the lateral mandibular periosteum via an extra‐oral approach. After 2 weeks, the expanders were removed and a particulated onlay bone graft and deproteinized bovine bone mineral (DBBM) (Bio‐Oss^®) were placed in the expanded area and covered by a titanium mesh. The bone and DBBM were separated in two compartments under the mesh with a collagen membrane in between. The mesh was then covered with a collagen membrane. After 3 months, the animals were sacrificed and specimens were collected for histology. Results: The osmotic soft tissue expander created a subperiosteal pocket and a ridge of new bone formed at the edges of the expanded periosteum in all sites. After the healing period of 3 months, no soft tissue dehiscence was recorded. The mean bone fill was 58.1±18% in the bone grafted area and 56.9±13.7% in the DBBM area. There was no significant difference between the autologous bone graft and the DDBM under the titanium mesh with regard to the total bone area or the mineralized bone area. Scanning electron microscopy showed that new bone was growing in direct contact with the DBBM particles and the titanium mesh. There is a soft tissue ingrowth even after soft tissue expansion and protection of the titanium mesh with a collagen membrane. Conclusion: This study confirms that an osmotic soft tissue expander creates a surplus of periosteum and soft tissue, and that new bone can subsequently be generated under a titanium mesh with the use of an autologous bone graft or DBBM. To cite this article:
Abrahamsson P, Isaksson S, Andersson G. Guided bone generation in a rabbit mandible model after periosteal expansion with an osmotic tissue expander.
Clin. Oral Impl. Res. 22 , 2011; 1282–1288.
doi: 10.1111/j.1600‐0501.2010.02108.x     

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 (₃P₃, ₄P₄) 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. To cite this article:
Araújo MG, Liljenberg B, Lindhe J. Dynamics of Bio‐Oss^® Collagen incorporation in fresh extraction wounds: an experimental study in the dog.
Clin. Oral Impl. Res. 21 , 2010; 55–64.     

The effect of permanent grafting materials on the preservation of the buccal bone plate after tooth extraction: an experimental study in the dog

Objectives: The aim of the present study was to evaluate the effects of a novel bone substitute system (Natix^®), consisting of porous titanium granules (PTG) and a bovine‐derived xenograft (Bio‐Oss^®), on hard tissue remodelling following their placement into fresh extraction sockets in dogs. Material and methods: Six modalities were tested; Natix^® granules with and without a covering double‐layered Bio Gide^® membrane; Bio‐Oss^® with and without a covering double‐layered Bio Gide^® membrane; and a socket left empty with and without a covering double‐layered Bio Gide^® membrane. Linear measurements, indicative of buccal bone height loss, and an area measurement indicative of buccal bulk bone loss were made. The statistical analysis was based on the Latin Square design with two blocking factors (dog and site). Tukey's post hoc test was used to adjust for multiple comparisons. Results: Histological observation revealed that while bone formed around both the xenograft and the titanium particles, bone was also noted within titanium granules. Of the five modalities of ridge preservation techniques used in this study, no one technique proved to be superior. Conclusion: The titanium granules were observed to have promising osseoconductive properties. To cite this article:
Bashara H, Wohlfahrt JC, Polyzois I, Lyngstadaas SP, Renvert S, Claffey N. The effect of permanent grafting materials on the preservation of the buccal bone plate after tooth extraction: an experimental study in the dog.
Clin. Oral Impl. Res. 23 , 2012; 911–917
doi: 10.1111/j.1600‐0501.2011.02240.x     

Deproteinized Bovine Bone Used as an Adjunct to Guided Bone Augmentation: An Experimental Study in the Rat

Background: Promising results have been reported following treatment of periodontal and peri‐implant bone defects with deproteinized bovine bone grafts, but their influence on bone formation has not been clarified. Purpose: The goal of this study was to examine whether implantation of deproteinized bovine bone (Bio‐Oss, Geistlich AG, Wolhusen, Switzerland) influences bone formation when used as an adjunct to guided bone augmentation (GBA). Materials and Methods: A rigid, hemispherical, Teflon capsule was loosely packed with a standardized quantity of Bio‐Oss and placed with its open part facing the lateral surface of the mandibular ramus (test) in 30 rats. At the contralateral side of the jaw, an empty capsule was placed (control). Groups of 10 animals were sacrificed after 1, 2, and 4 months. The volumes of the space created by the capsule and of the (1) newly formed bone, (2) remaining Bio‐Oss particles, (3) soft connective tissue, and (4) acellular space in the capsule were estimated by a point‐counting technique in three or four histologie sections, taken by uniformly random sampling. Results: Bone formation at 1 month was limited in both tests and controls. After 2 months, the mean volume of the newly formed bone occupied 9.0% of the space created by the capsule in the test specimens compared with 23.8% in the control specimens (p <.01). After 4 months, the respective figures were 11.6% (tests) versus 38.7% (controls) (p <.01). Conclusion: It can be concluded that Bio‐Oss, used as an adjunct to GBA, interferes with bone formation.     

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 (₄P₄) 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. To cite this article:
Araújo MG, Linder E, Lindhe J. Bio‐Oss^® Collagen in the buccal gap at immediate implants: a 6‐month study in the dog.
Clin. Oral Impl. Res. 22 , 2011; 1–8.
doi: 10.1111/j.1600‐0501.2010.01920.x     

Bone regeneration at implants placed into extraction sockets of maxillary incisors in dogs

Aim: To compare the influence of autologous or deproteinized bovine bone mineral as grafting material on healing of buccal dehiscence defects at implants installed immediately into the maxillary second incisor extraction socket in dogs. Material and methods: In the maxillary second incisor sockets of 12 Labrador dogs, implants were installed immediately following tooth extraction. A standardized buccal defect was created and autologous bone particles or deproteinized bovine bone mineral were used to fill the defects. A collagen membrane was placed to cover the graft material, and the flaps were sutured to fully submerge the experimental areas. Six animals were sacrificed after 2 months, and six after 4 months of healing. Ground sections were obtained for histological evaluation. Results: After 2 months of healing, all implants were osseointegrated. All buccal dehiscence defects were completely filled after 2 months irrespective of the augmentation material (autologous bone or Bio‐Oss^®) applied. Bone‐to‐implant contact (BIC) on the denuded implant surfaces was within a normal range of 30–40%. However, the newly formed tissue at 2 months was partially resorbed (>50% of the area measurements) after 4 months. Conclusions: Applying either autologous bone or deproteinized bovine bone mineral to dehiscences at implants installed immediately into extraction sockets resulted in high degree of regeneration of the defects with satisfactory BIC on the denuded implant surface. To cite this article:
De Santis E, Botticelli D, Pantani F, Pereira FP, Beolchini M, Lang NP. Bone regeneration at implants placed into extraction sockets of maxillary incisors in dogs.
Clin. Oral Impl. Res. 22 , 2011; 430–437.     

Clinical and radiographic characteristics of single‐tooth replacements preceded by local ridge augmentation: a prospective randomized clinical trial

Objectives: To assess in a randomized‐clinical trial the influence of three augmentation techniques (chinbone with or without a Bio‐Gide^® membrane and Bio‐Oss^® with a Bio‐Gide^® membrane) on the clinical and radiographic characteristics of hard and soft tissues around implants and adjacent teeth in the reconstructed maxillary anterior region, up to 1 year after functional loading. Materials and methods: Ninety‐three patients requesting single‐tooth replacement and presenting with a horizontal (bucco‐palatinal) bone deficiency were included. After augmentation, 93 ITI‐Esthetic^Plus implants were placed. Clinical variables, standardized photographs and radiographs were analysed to assess the impact on the levels of the marginal gingiva (MGL) and marginal bone (MBL) around implants and adjacent teeth, viz at pre‐augmentation, pre‐implantation (TPI) and 1 (T₁) and 12 (T₁₂) months after final crown placement. Results: Implant survival was 97.8%. No significant differences were observed in the treatment outcomes of the three augmentation modalities. Combining the three modalities, a slight but significant increase in the implants approximal pocket depth was found between T₁ and T₁₂. Approximal bone loss at the implant between T₁ and T₁₂ was 0.14 ± 0.76 mm (mesial) and 0.14 ± 0.47 mm (distal); the approximal MGL slightly increased (mesial: 0.24 ± 0.46 mm, distal: 0.25 ± 0.66 mm), and the buccal MGL decreased (0.11 ± 0.61 mm). Bone loss at the adjacent teeth, although minor, was significant between TPI and T₁. No correlations were observed in changes of MBL and MGL. Conclusions: None of the three applied augmentation technique procedures influenced the characteristics of the MGL and MBL or the implant survival of single‐tooth replacements. Peri‐implant hard and soft tissues were very stable in the first year after loading.     

Maxillary sinus floor elevation with bovine bone mineral combined with either autogenous bone or autogenous stem cells: a prospective randomized clinical trial

Aim: To assess whether differences occur in bone formation after maxillary sinus floor elevation surgery with bovine bone mineral (BioOss^®) mixed with autogenous bone or autogenous stem cells. The primary endpoint was the percentage of new bone three months after the elevation procedure. Material and methods: In a randomized, controlled split‐mouth design, in 12 consecutive patients (age 60.8 ± 5.9 years, range 48–69 years) needing reconstruction of their atrophic maxilla, a bilateral sinus floor augmentation procedure was performed. Randomly, on one side the augmentation procedure was performed with bovine bone mineral (BioOss^®) seeded with mononuclear stem cells harvested from the posterior iliac crest (test group) while BioOss^® mixed with autogenous bone (harvested from the retromolar area) was applied on the contra‐lateral side (control group). On 14.8 ± 0.7 weeks after the sinus floor elevation, biopsies from the reconstructed areas were taken at the spots where subsequently the endosseous implants were placed. The biopsies were histomorphometrically analyzed. Results: Significantly more bone formation was observed in the test group (17.7 ± 7.3%) when compared with the control group (12.0%± 6.6; P=0.026). In both the test and control group, all implants could be placed with primary stability. In one patient, not all biopsies contained BioOss^®. This patient was excluded from analysis. Conclusion: Mesenchymal stem cells seeded on BioOss^® particles can induce the formation of a sufficient volume of new bone to enable the reliable placement of implants within a time frame comparable with that of applying either solely autogenous bone or a mixture of autogenous bone and BioOss^®. This technique could be an alternative to using autografts. To cite this article: Rickert D, Sauerbier S, Nagursky H, Menne D, Vissink A, Raghoebar GM. Maxillary sinus floor elevation with bovine bone mineral combined with either autogenous bone or autogenous stem cells: a prospective randomized clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 251–258.
doi: 10.1111/j.1600‐0501.2010.01981.x     

Ridge alterations following immediate implant placement and the treatment of bone defects with Bio-Oss in an animal model

Background: Conflicting data exist on the outcome of placing Bio‐Oss® (Geitslich Pharm AG, Wolhausen, Switzerland) into extraction sockets. It is therefore relevant to study whether the incorporation of Bio‐Oss into extraction sockets would influence bone healing outcome at the extraction sites. Purpose: The aim of this study was to assess peri‐implant bone changes when implants were placed in fresh extraction sockets and the remaining defects were filled with Bio‐Oss particles in a canine mandible model. Materials and Methods: Six mongrel dogs were used in the study. In one jaw quadrant of each animal, the fourth mandibular premolars were extracted with an elevation of the mucoperiosteal flap; implants were then placed in the fresh extraction sockets and the remaining defects were filled with Bio‐Oss particles. After 4 months of healing, micro‐computed tomography at the implant sites was performed. Osseointegration was calculated as the percent of implant surface in contact with bone. Additionally, bone height was measured in the peri‐implant bone. Results: Average osseointegration was 28.5% (ranged between 14.8 and 34.2%). The mean crestal bone loss was 4.7 ± 2.1 mm on the buccal aspect, 0.4 ± 0.5 mm on the mesial aspect, 0.4 ± 0.3 mm on the distal aspect, and 0.3 ± 0.4 mm on the lingual aspect. Conclusion: The findings from this study demonstrated that the placement of implants and Bio‐Oss® particles into fresh extraction sockets resulted in significant buccal bone loss with low osseointegration.     

Alveolar ridge preservation with guided bone regeneration and a synthetic bone substitute or a bovine‐derived xenograft: a randomized,controlled clinical trial

Objectives: The aim of this randomized, controlled clinical trial was to compare the potential of a synthetic bone substitute or a bovine‐derived xenograft combined with a collagen membrane to preserve the alveolar ridge dimensions following tooth extraction. Methods: Twenty‐seven patients were randomized into two treatment groups following single tooth extraction in the incisor, canine and premolar area. In the test group, the alveolar socket was grafted with Straumann Bone Ceramic^® (SBC), while in the control group, Bio‐Oss^® deproteinized bovine bone mineral (DBBM) was applied. In both groups, a collagen barrier was used to cover the grafting material. Complete soft tissue coverage of the barriers was not achieved. After 8 months, during re‐entry procedures and before implant placement, the horizontal and vertical dimensions of the residual ridge were re‐evaluated and trephine biopsies were performed for histological analysis in all patients. Results: Twenty‐six patients completed the study. The bucco‐lingual dimension of the alveolar ridge decreased by 1.1±1 mm in the SBC group and by 2.1±1 in the DBBM group (P<0.05). Both materials preserved the mesio‐distal bone height of the ridge. No differences in the width of buccal and palatal bone plate were observed between the two groups. The histological analysis showed new bone formation in the apical part of the biopsies, which, in some instances, was in direct contact with both SBC and DBBM particles. The coronal part of the biopsies was occupied by a dense fibrous connective tissue surrounding the SBC and DBBM particles. Conclusion: Both biomaterials partially preserved the width and the interproximal bone height of the alveolar ridge. To cite this article:
Mardas N, Chadha V, Donos N. Alveolar ridge preservation with guided bone regeneration and a synthetic bone substitute or a bovine‐derived xenograft: a randomized, controlled clinical trial.
Clin. Oral Impl. Res. 21 , 2010; 688–698.     

Effect of rhBMP-2 on guided bone regeneration in humans

Abstract: The aim of the present clinical study was to test whether or not the addition of recombinant human bone morphogenetic protein‐2 (rhBMP‐2) to a xenogenic bone substitute mineral (Bio‐Oss^®) will improve guided bone regeneration therapy regarding bone volume, density and maturation. In 11 partially edentulous patients, 34 Brånemark implants were placed at two different sites in the same jaw (five maxillae, six mandibles) requiring lateral ridge augmentation. The bone defects were randomly assigned to test and control treatments: the test and the control defects were both augmented with the xenogenic bone substitute and a resorbable collagen membrane (Bio‐Gide^®). At the test sites, the xenogenic bone substitute mineral was coated with rhBMP‐2 in a lyophilization process. Following implant insertion (baseline), the peri‐implant bone defect height was measured from the implant shoulder to the first implant–bone contact. After an average healing period of 6 months (SD 0.17, range 5.7–6.2), the residual defects were again measured and trephine burs were used to take 22 bone biopsies from the augmented regions. The healing period was uneventful except for one implant site that showed a wound dehiscence, which spontaneously closed after 4 weeks. Later at reentry, all implants were stable. At baseline, the mean defect height was 7.0 mm (SD 2.67, range 3–12 mm) at test and 5.8 mm (SD 1.81, range 3–8 mm) at control sites. At reentry, the mean defect height decreased to 0.2 mm (SD 0.35, range 0–1 mm) at test sites (corresponding to 96% vertical defect fill) and to 0.4 mm (SD 0.66, range 0–2 mm) at the control site (vertical defect fill of 91%). Reduction in defect height from baseline to reentry for both test and control sites was statistically significant (Wilcoxon P<0.01). Histomorphometric analysis showed an average area density of 37% (SD 11.2, range 23–51%) newly formed bone at test sites and 30% (SD 8.9, range 18–43%) at control sites. The fraction of mineralized bone identified as mature lamellar bone amounted to 76% (SD 14.4, range 47.8–94%) at test compared to 56% (SD 18.3, range 31.6–91.4%) at control sites (paired t‐test P<0.05). At BMP‐treated sites 57% (SD 16.2, range 29–81%) and at control sites 30% (SD 22.6, range 0–66%) of the surface of the bone substitute particles were in direct contact with newly formed bone (paired t‐test P<0.05). It is concluded that the combination of the xenogenic bone substitute mineral with rhBMP‐2 can enhance the maturation process of bone regeneration and can increase the graft to bone contact in humans. rhBMP‐2 has the potential to predictably improve and accelerate guided bone regeneration therapy.     

Histologic analysis of clinical biopsies taken 6 months and 3 years after maxillary sinus floor augmentation with 80% bovine hydroxyapatite and 20% autogenous bone mixed with fibrin glue

Background: Bovine hydroxyapatite (Bio‐Oss®, Geistlich Pharmaceutical, Wollhausen, Switzerland) has been suggested to be used in maxillary sinus floor augmentation procedures prior to or in conjunction with implant placement. However, the long‐term histologic fate of this material is not well understood. Purpose: The aim with this study was to histologically evaluate the tissue response in patients to a mixture of bovine hydroxyapatite (BH), autogenous bone, and fibrin glue 6 months and 3 years after a maxillary sinus floor augmentation procedure. Materials and Method: Biopsies were taken from a group of 20 consecutive patients 6 months (n = 16) and 3 years (n = 12) after maxillary sinus floor augmentation with a mixture of BH (80%), autogenous bone (20%), and fibrin glue and prepared for histologic analysis. Results: Light microscopy and morphometry from biopsies taken after 6 months showed various amounts of mineralized bone tissue. The specimen area was occupied by 54.1 ± 12.6% nonmineralized tissue, followed by 21.2 ± 24.5% lamellar bone, 14.5 ± 10.3% BH particles, and 10.2 ± 13.4% woven bone. The nonmineralized tissue seen in bone‐forming areas consisted of a loose connective tissue, rich with vessels and cells. There were no signs of resorption of the BH particles. The lamellar bone appeared to have originated from the recipient site and was seldom in contact with the BH particles. After 3 years, the nonmineralized tissue area had decreased to 36.0 ± 19.0% (p > .05) and consisted mainly of bone marrow tissue. The surface area of lamellar bone had increased to 50.7 ± 22.8% (p > .05), and there was almost no immature bone. The mean specimen area occupied by BH particles, was 12.4 ± 8.7% and had not changed from 6 months (not significant). Moreover, the sizes of the particles were similar after 6 months and 3 years. The degree of BH particle–bone contact had increased from 28.8%± 19.9% after 6 months to 54.5 ± 28.8% after 3 years (p > .05). Conclusion: Histology of specimens from maxillary sinuses augmented with 80% BH particles, 20% autogenous bone, and fibrin glue showed a positive bone tissue response after 6 months and 3 years after augmentation of the maxillary sinus floor prior to implant placement in a group fo 20 patients. The bone surrounding and in contact with the BH particles after 6 months was mainly immature woven bone, which with time was replaced by mature lamellar bone filling the interparticle space as observed in the 3‐year specimens. Moreover, bone‐integrated BH particles seem to be resistant to resorption. The results indicate that the procedure may be considered when only small amounts of intraoral autogenous bone graft are available.