Comparative study of the osseous healing process following three different techniques of bone augmentation in the mandible: an experimental study

The aim of this study was to evaluate the osseointegration of three different bone grafting techniques. Forty-eight mature New Zealand rabbits were divided randomly into three groups of 16 each. Horizontal augmentation was performed on the corpus of the mandible using three different techniques: free bone graft (FBG), free periosteal bone graft (PBG), pedicled bone flap (BF). The animals were sacrificed at postoperative weeks 1, 3, or 8. Specimens were decalcified for histological examination, and histomorphometric measurements were performed. The histological evaluation demonstrated bony fusion between the grafts and the augmented mandibular bone after 8 weeks in all groups. At week 8, the bone volume was significantly greater in the BF group than in the FBG (P < 0.001) and PBG (P = 0.001) groups, and also the trabecular thickness was significantly greater than in the FBG (P = 0.015) and PBG (P = 0.015) groups. Trabecular separation was significantly lower in the BF group than in the FBG group at week 8 (P = 0.015). BF demonstrated greater osseous healing capacity compared to FBG and PBG. The preserved vascularization in BF improves the bone quality in mandibular bone augmentations.     

Measurement of ridge alterations following tooth removal: a radiographic study in humans

Objective: The aim of this study was a radiographic mesiodistal analysis of the shape of the bone crest 3 months after tooth removal. Material and methods: One hundred single tooth extractions were performed on 100 patients because of orthodontic or prosthetic causes. Bite blocks were used for two radiographs: one on the day of extraction and the other after healing of the socket, 3 months later. These X‐rays were used to determine: (1) the most apical distance of alveolar ridge resorption, with baseline as the line between bone‐to‐teeth contact (the greatest distance in bone resorption height) and (2) the mesiodistal distance (MDD) and mesial and distal angles arising after bone tissue modeling. Results: Significant differences (P<0.05) emerged between the MDDs of multiple‐ [8 mm, 95% confidence interval (CI): 6.09, 9.90] and single‐root teeth (5.60 mm, 95% CI: 4.80, 6.50). However, mesial or distal angles or the most apical distance of alveolar ridge resorption did not differ (mean distance in height=4.32 mm, 95% CI: 3.85, 4.78; mean angle=24°). Conclusions: In this study, the post‐extraction mesiodistal bone distance between teeth adjacent to the edentulous ridge depends on the size of the edentulous space. Nevertheless, the distance does not affect the distance in bone loss height. The distance of bone resorption height reaches a balance at the midpoint, which we consider indicative of stable healing. This resorption process must be considered when placing dental implants in fresh extraction sockets, especially in aesthetic sites, because the implant surfaces could be exposed after 3 months. To cite this article:
Moya‐Villaescusa MJ, Sánchez‐Pérez A. Measurement of ridge alterations following tooth removal: a radiographic study in humans.
Clin. Oral Impl. Res. 21 , 2010; 237–242.
doi: 10.1111/j.1600‐0501.2009.01831.x     

Comparison of BMP-2 and -4 for rat mandibular bone regeneration at various doses

OBJECTIVE: To compare mandibular bone regeneration with bone morphogenetic proteins-2 and -4 (BMP-2 and -4) at varying doses. STUDY DESIGN: Defects were created in the left hemi-mandibles of 82 Sprague-Dawley rats. The defects were filled with a hyaluronic acid polymer loaded with 0.01, 0.1, 1, or 10 microg of BMP-2 or -4. Control groups consisted of animals with unfilled defects, or with defects filled with the hyaluronic acid sponges loaded with growth factor dilution buffer. Animals were killed after 8 weeks, and the hemi-mandibles were analyzed histologically using stereologic techniques. RESULTS: Mandibles implanted with carriers containing 10 microg of BMP-2 or -4 differed significantly from controls in terms of new bone area (p = 0.01 and p = 0.0001, respectively). Marrow space development occurred in a dose-dependent fashion (p < 0.0001 for both growth factors), and this effect was more pronounced for BMP-2 at larger doses (p < 0.0001 at 1 and 10 microg doses). New bone areas and volumes did not differ significantly between the growth factors. While defects implanted with BMP-4 tended to have thicker cortical bone and more trabecular bone, at least partial defect bridging was achieved in a greater number of defects implanted with BMP-2 (47%) than with BMP-4 (35%). CONCLUSION: Although similar areas and volumes of new bone were induced with BMP-2 and -4, differences were noted in the quality of bone generated with each growth factor. The results indicate a threshold dose for acute administration between 1 and 10 mug BMP-2 for bony union in this model, and > or =10 microg for BMP-4. SIGNIFICANCE: These findings suggest that differences in bone growth factor osteogenic potential deserve further study and may have an impact on the translation of osteoinductive protein therapy into clinical practice.     

Histomorphologic and histomorphometric evaluation of various endosseous implant healing chamber configurations at early implantation times: a study in dogs

Aim: The objective of this study was to evaluate the early healing of endosseous implants presenting various healing chamber configurations in a beagle dog mandible model. Methods: The four premolars of 12 beagle dogs were extracted and allowed to heal for a period of 8 weeks. Implants allowing six different healing chamber configurations were placed in each dog (three per side, six configurations per dog). The animals were sacrificed after 3 and 5 weeks in vivo (n=6 per time in vivo), and the implants were non‐decalcified processed to slides of ～30 μm thickness. Bone‐to‐implant contact (BIC) and bone area fraction occupied (BAFO) within the healing chamber were quantified. Statistical analysis was performed by a GLM ANOVA model at 5% significance level. Results: Osseointegration and healing with woven bone filling throughout all healing chambers was observed. Replacement of woven bone by lamellar bone showing primary osteonic structures was observed at 5 weeks. BIC was significantly affected by healing chamber configuration (P<0.001) and was not affected by time in vivo (P>0.42) at 3 and 5 weeks in vivo. BAFO was not affected by healing chamber configuration (P>0.14) however significantly increased over implantation time (P<0.001). Conclusion: Regardless of healing chamber design and dimensions considered, healing allowed the devices osseointegration. However, healing chamber configuration significantly affected osseointegration measurable parameters such as BIC. To cite this article:
Marin C, Granato R, Suzuki M, Gil JN, Janal, MN Coelho PG. Histomorhpologic and histomorphometric evaluation of various endosseous implant healing chamber configurations at early implantation times: a study in dogs.
Clin. Oral Impl. Res. 21 , 2010; 577–583.
doi: 10.1111/j.1600‐0501.2009.01853.x     

Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs

OBJECTIVES: The aim of the present experiment was to study events involved in the healing of marginal, central and apical compartments of an extraction socket, from the formation of a blood clot, to bone tissue formation and remodeling of the newly formed hard tissue. MATERIAL AND METHODS: Nine mongrel dogs were used for the experiment. The fourth mandibular premolars were selected for study and were divided into one mesial and one distal portion. The distal root was removed and the socket with surrounding soft and mineralized tissue was denoted "experimental unit". The dogs were killed 1, 3, 7, 14, 30, 60, 90, 120 and 180 days after the root extractions. Biopsies including the experimental units were demineralized in EDTA, dehydrated in ethanol and embedded in paraffin. Serial sections 7 microm thick were cut in a mesio-distal plane. From each biopsy, three sections representing the central part of the socket were selected for histological examination. Morphometric measurements were performed to determine the volume occupied by different types of tissues in the marginal, central and apical compartments of the extraction socket at different intervals. RESULTS: During the first 3 days of healing, a blood clot was found to occupy most of the extraction site. After seven days this clot was in part replaced with a provisional matrix (PCT). On day 14, the tissue of the socket was comprised of PM and woven bone. On day 30, mineralized bone occupied 88% of the socket volume. This tissue had decreased to 15% on day 180. The portion occupied by bone marrow (BM) in the day 60 specimens was about 75%, but had increased to 85% on day 180. CONCLUSION: The healing of an extraction socket involved a series of events including the formation of a coagulum that was replaced by (i) a provisional connective tissue matrix, (ii) woven bone, and (iii) lamellar bone and BM. During the healing process a hard tissue bridge--cortical bone--formed, which "closed" the socket.     

Recent outcomes and perspectives of the application of bone morphogenetic proteins in implant dentistry

Background: Since the discovery of bone morphogenetic proteins (BMPs), the number of related studies has increased substantially, and more recent outcomes have cast encouraging perspectives on their use in reconstructive surgery. Purpose: The aim of the present review was to summarize the present knowledge about the use of BMPs in conjunction with dental implants based on the literature. Materials and Methods: Scientific articles dealing with the use of growth factors and bone healing with or without dental implants were searched for on MEDLINE and critically scrutinized. Results: Thirty‐nine scientific reports formed the base for the present review. Whereas the osteoinductive capability of BMPs is well documented, studies on their effects in implant dentistry are still incipient. Preclinical and clinical studies did not show outstandingly good outcomes of the application of BMPs compared with conventional treatments or controls. Conclusions: The number of studies in the field of dental implantology in which BMPs have been used is still too small for establishing clinical protocols of their use in order to improve a recipient bone bed prior to implant placement or to enhance the integration process of an implant.     

Timing of Implant Placement and Augmentation with Bone Replacement Material: Clinical Assessment at 8 and 16 Months

Purpose: The purpose of this study is to evaluate implants placed at different times of bone augmentation. Materials and Methods: Four implants were placed in seven dogs: one at a 6‐month bovine mineral grafted site (6‐month Bio‐Oss® grafted site [6mBio]), one at a grafted membrane‐protected simultaneously augmented (Fresh Bio‐Oss® grafted site [FrBio]) site, one at a clotted (nongrafted clotted membrane‐protected site [Clot]) membrane‐protected site, and one at a pristine (nongrafted uncovered site [Cont]) site. Implants were exposed after 6 months. The same protocol was repeated on the contralateral side, at a delay of 8 months. Peri‐implant care was performed throughout the hygienic phase (2 and 10 months, respectively) every 48 to 72 hours. Probing depth and bleeding on probing were recorded. Implant stability was determined by a Periotest® (Medizintechnik Gulden, Modautal, Germany). Statistical analysis was conducted using analysis of variance with repeated measures. Results: Average probing depth at the simultaneously grafted sites was 2.21 mm and 2.03 mm at 8 and 16 months, respectively. At the 6‐month grafted sites, it was 1.96 mm and 1.57 mm. At the Clot sites, it was 2.68 mm and 2.07 mm, and 2.21 mm and 1.82 mm at the Cont sites, respectively. The average bleeding on probing was 0.50 and 0.42 at the FrBio sites, and 0.35 and 0.07 at the 6mBio sites during the respective periods. At the Clot sites, it was 0.50 and 0.28, and at the Cont sites, 0.43 and 0.21, respectively. Probing depth significantly reduced over the time at 6mBio, Clot, and Cont sites (p < .03). Average implant stability score at the FrBio sites was ?0.24 and ?0.27, and ?0.50 and ?0.46 at the 6mBio sites, at 8 and 16 months, respectively. At the Clot sites, it was ?0.35 and ?0.46. Cont sites averaged ?0.37 at both periods. Implant stability was significantly higher (p < .005) comparing 6mBio over FrBio, 6mBio over Cont, and Clot over FrBio sites. Conclusions: Immediate and delayed augmentations are safe modes. Probing depth and bleeding indices gradually improved along time. Implant stability was higher at the delayed mode.     

The effect of non-resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs

Objective: For successful implant treatment in the esthetic area, stable hard tissue and soft tissue are very important. At the buccal side without buccal bone defects, prophylactic guided bone regeneration (GBR) with bone substitute was frequently used for achieving thick buccal bone. The aim of this study was to evaluate the effect of GBR using a non‐resorbable membrane in an immediate implant site without bone defects. Material and methods: Immediate implants were placed into the mandibles of four mongrel dogs. In the experimental group (TM group), a non‐resorbable membrane was placed and fixed onto the buccal bone plate around the implant. In the control group, the implants were placed without membrane coverage. After 12 weeks, the dogs were sacrificed and histological specimens were prepared. The vertical distances from the smooth–rough surface interface (SRI) to the gingiva, the first‐bone contact, and the bone crest were measured on the buccal and lingual sides. The horizontal thicknesses of the gingiva and bone at 0, 1, 2, and 3 mm below the SRI were measured. Results: In the TM group, first‐bone contact on the buccal side was more coronally positioned approximately 0.8 mm than the control group (P=0.041). The buccal bone thickness of the TM group was well preserved and there was no difference between the buccal and lingual sides. Comparing the control group, implants of the TM group had 1 mm thicker buccal bone (P=0.0051 at bone 1 mm level, P=0.002 at bone 2 mm level). In the control group, buccal bone loss was observed and buccal bone was about 1 mm thinner than the lingual bone (P<0.05). Conclusions: GBR with a non‐resorbable membrane and no bone graft substitute could help to preserve buccal bone thickness on the immediate implant site without defects. To cite this article:
Park S‐Y, Kye S‐B, Yang S‐M, Shin S‐Y. The effect of non‐resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs.
Clin. Oral Impl. Res. 22 , 2011; 289–294.
doi: 10.1111/j.1600‐0501.2010.01995.x