Clinical and histological evaluation of subepithelial connective tissue after collagen sponge implantation in the human palate.

BACKGROUND AND OBJECTIVE: Successful root-coverage treatment depends on the thickness of the donor tissue. This study aimed to evaluate the thickness of donor tissue after augmentation of the connective tissue in the palatal area by implantation of lyophilized collagen sponge (Hemospon(®) ). MATERIAL AND METHODS: Ten patients with an indication for root coverage, whose palate was deficient in adequate connective tissue, were recruited. The procedure was carried out in two stages. In the first stage, the palatal thickness in the donor site was measured at three standardized points (points 1, 2 and 3), from the distal of the canine to the distal of the first molar, and the lyophilized collagen sponge was inserted. In the second stage, the palatal thickness over the implant was measured (at points 1, 2 and 3), two biopsies of the palatal mucosa were collected - one over the implant (experimental sample) and the other on the contralateral side (control sample) - and then root-coverage treatment was performed. Analyses consisted of clinical assessment of the palatal measurements before and after sponge implantation, and histological assessment of the experimental and control biopsy samples. Data were analyzed using the Wilcoxon test. RESULTS: Both analyses showed a significant increase in mean thickness, of 1.08 mm of neoformed tissue in the clinical analysis (the tissue at point 2 was the thickest of the three points) and of 0.53 mm in the histological analysis. CONCLUSION: The insertion of lyophilized collagen sponge induced a significant increase in the thickness of palatal connective tissue.

Healing of extraction sockets and surgically produced - augmented and non-augmented - defects in the alveolar ridge. An experimental study in the dog.

OBJECTIVES: The current experiments had three aims (i) to determine whether the absence of the periodontal ligament (PDL) may alter features of the healing of an extraction socket, (ii) to examine if there were differences in the proportion of different tissues in resolved extraction sockets and surgically produced defects after 3 months of healing, (iii) to study the influence of different biomaterials on the healing of surgically produced bone defects. MATERIAL AND METHODS: Extraction sites: In five dogs, the 4th mandibular pre-molars were hemi-sected and the distal roots were removed. The extraction socket of one of the pre-molars was instrumented to eliminate all remnants of the PDL tissue. The socket of the contra-lateral pre-molar was left without instrumentation. The dogs were sacrificed after 3 months of healing. Defect sites: In five dogs, the pre-molars and 1st molars on both sides of the mandible were first removed and 3 months of healing allowed. After this interval three standardized cylindrical defects were prepared in each side of the mandible. The defects were 3.5 mm in diameter and 8 mm deep. In each quadrant one defect was grafted with Bio-Oss Collagen, one with Collagen Sponge and one defect was left non-grafted. The dogs were sacrificed 3 months after the grafting procedure. RESULTS: Extraction sites: The two categories of extraction sockets did not differ with respect to gross morphological features. The tissue of the extraction sites, apical of a newly formed bone bridge, was dominated by bone marrow. Few trabeculae of lamellar bone were also present. Defect sites: The non-augmented defect was sealed by a hard-tissue bridge. In the central and apical portions of the defect bone marrow made up about 61%, and mineralized bone 39% of the tissues. The invagination of the surface of this crestal bone was 0.8+/-0.3 mm. The defect augmented with Collagen Sponge was covered by a hard-tissue bridge 38% of the tissue within the defect was made up of bone marrow while the remaining 62% was occupied by mineralized bone. The invagination of the hard-tissue bridge was on the average 0.6+/-0.1 mm. In defects augmented with Bio-Oss Collagen the biomaterial occupied a substantial portion of the tissue volume. Eighty-five percent of the periphery of the Bio-Oss particles were found to be in direct contact with newly formed mineralized bone. Woven bone and bone marrow made up 47% and 26% of the newly formed tissue. The invagination of the most coronal part of the bone defect was 0.1+/-0.1 mm. CONCLUSION: Sockets that following tooth removal had their PDL tissue removed exhibited similar features of healing after 3 months as sockets which had the PDL retained. The tissues present in an extraction site appeared to be more mature than those present in a surgically produced defect of similar dimension. The Bio-Oss Collagen augmented defect exhibited less wound shrinkage than the non-augmented defect.

Effect of enamel matrix proteins (Emdogain') on healing after re-implantation of "periodontally compromised" roots. An experimental study in the dog.

OBJECTIVE: The present experiment was performed to assess whether Emdogain applied on the root surface of extracted teeth or teeth previously exposed to root planning can protect the tooth from ankylosis following re-implantation. MATERIAL AND METHODS: The experiment included two groups of dogs, including five animals each. The root canals of all mandibular third premolars (3 P 3) were reamed and filled with gutta-percha. A crestal incision was placed from the area of the second to the fourth premolar. Buccal and lingual full thickness flaps were elevated. With the use of a fissure bur, the crown and furcation area of 3 P 3 were severed in an apico-coronal cut. The distal and mesial tooth segments were luxated with an elevator and extracted with forceps. Group A: The mesial and distal segments of 3 P 3 were air dried on a glass surface for 60 min. The roots from the right side were conditioned and exposed to Emdogain application. The roots from the left side received the same treatment with the exception of Emdogain application. The mesial and distal tooth segments were re-implanted and the crown portions were severed with a horizontal cut and removed. The buccal and lingual flaps were mobilized and sutured to obtain complete coverage of the submerged roots. Group B: A notch was prepared in each root, 4-5 mm apical of the cemento-enamel junction. The area of the root that was located coronal to the notch was scaled and planned. The roots in the right side of the mandible were treated with Emdogain, while the roots in the left side served as controls. After 6 months of healing, the dogs were killed and blocks containing one root with surrounding tissues were harvested, and prepared for histological examination, which also included morphometric assessments. Thus, the proportions of the roots that exhibited signs of (i) replacement (ii) inflammatory and (iii) surface resorption were calculated. RESULTS AND CONCLUSION: It was demonstrated that healing of a re-implanted root that had been extracted and deprived of vital cementoblasts was characterized by processes that included root resorption, ankylosis and new attachment formation. It was also demonstrated that Emdogain treatment, i.e. conditioning with EDTA and placement of enamel matrix proteins on the detached root surface, failed to interfere with the healing process.

Lateral ridge augmentation by the use of grafts comprised of autologous bone or a biomaterial. An experiment in the dog.

OBJECTIVE: The present investigation was performed to determine if a block of Bio-Oss used as an onlay graft can be used as a scaffold for new bone formation. MATERIAL AND METHODS: Five mongrel dogs were used. The mandibular premolars were extracted. On both sides of the mandible, the buccal bone plate was resected and defects, about 25 mm long, 8 mm high and 5 mm wide, were produced After 3 months of healing, a second surgical procedure was performed. In the left side, a block of Bio-Oss was adjusted to the buccal bone wall. The graft had the shape of a cylinder and was retained with a miniscrew and covered with a collagen membrane. In the contra-lateral side of the mandible, a block biopsy was first obtained from the ascending ramus. This bone graft had the shape of a cylinder that was 8 mm in diameter and 3 mm thick. The graft was transferred to the experimental site, adjusted to the buccal wall, retained with a miniscrew, and covered with a membrane. The flaps were repositioned and closed with sutures to ensure a complete coverage of the experimental sites. After 6 months of healing, the dogs were sacrificed and the experimental sites dissected. The biopsies were processed for ground sectioning. The sections were stained in toluidine blue, examined in the microscope, and a number of histo- and morphometric assessments made. RESULTS: The study demonstrated that cortical bone used as an onlay graft in the lateral aspect of the alveolar ridge, during a 6-month period of healing integrated with the host bone but underwent marked peripheral resorption. Thus, close to 30% of the height and 50% of the length of the graft was replaced with connective tissue. It was further observed that while the dimensions of a graft which contained a scaffold of cancellous bovine bone mineral remained unchanged, only moderate amounts of new bone formed at the base of this graft. CONCLUSION: Grafts of autologous cortical bone, placed on the surface of a one-wall defect, may undergo marked resorption during healing. A similar graft of Bio-Oss may retain its dimension, and limited amounts of new bone will form within the biomaterial.