Sinus mucosa thinning and perforation after sinus augmentation. A histological study in rabbits.

AIM: To evaluate the modifications and possible perforations of the sinus mucosa lining graft particles and implant surfaces after sinus lifting. MATERIAL AND METHODS: Twelve New Zealand rabbits underwent a bilateral sinus lifting using either autogenous bone harvested from the tibia (AB; autogenous bone group) or deproteinized bovine bone mineral (DBBM group) as filler. Implants were simultaneously installed. Thinned sites (<40 µm) and perforations were histologically evaluated at the sinus mucosa in contact with the graft and with the implant after 7 and 40 days of healing. RESULTS: The mean width of the pristine mucosa was ~70-80 µm. After 7 days of healing, the sinus mucosa in contact with the graft presented fourteen thinned sites in the AB group (mean width 28.8±12.8 µm) and fifty-nine in the DBBM group (mean width 22.2±5.2 µm). No perforations of the mucosa were seen in the AB group while six perforations distributed in two sinuses were found in the DBBM group. After 40 days, only one thinned mucosa and no perforations were observed in the AB group while ninety-six thinned mucosa sites were shared by six sinuses (19.2±3.8 µm), and 3 perforations by two sinuses in the DBBM group. Few sites of the mucosa were in contact with the implant apex and threads after 7 days of healing. However, after 40 days, twelve thinned mucosa sites were seen in four sinuses in the AB groups (mean width ~19 µm) and 5 in two sinuses in the DBBM group (mean width ~20 µm). Perforations were seen in two sinuses in the AB group, and in one sinus in the DBBM group. CONCLUSIONS: The sinus mucosa might be damaged by a close contact with graft particles and implant surface.

Healing at implants installed concurrently to maxillary sinus floor elevation with Bio-Oss® or autologous bone grafts. A histo-morphometric study in rabbits.

OBJECTIVE: To compare the healing at elevated sinus floors augmented either with deproteinized bovine bone mineral (DBBM) or autologous bone grafts and followed by immediate implant installation. MATERIAL AND METHODS: Twelve albino New Zealand rabbits were used. Incisions were performed along the midline of the nasal dorsum. The nasal bone was exposed. A circular bony widow with a diameter of 3 mm was prepared bilaterally, and the sinus mucosa was detached. Autologous bone (AB) grafts were collected from the tibia. Similar amounts of AB or DBBM granules were placed below the sinus mucosa. An implant with a moderately rough surface was installed into the elevated sinus bilaterally. The animals were sacrificed after 7 (n = 6) or 40 days (n = 6). RESULTS: The dimensions of the elevated sinus space at the DBBM sites were maintained, while at the AB sites, a loss of 2/3 was observed between 7 and 40 days of healing. The implants showed similar degrees of osseointegration after 7 (7.1 ± 1.7%; 9.9 ± 4.5%) and 40 days (37.8 ± 15%; 36.0 ± 11.4%) at the DBBM and AB sites, respectively. Similar amounts of newly formed mineralized bone were found in the elevated space after 7 days at the DBBM (7.8 ± 6.6%) and AB (7.2 ± 6.0%) sites while, after 40 days, a higher percentage of bone was found at AB (56.7 ± 8.8%) compared to DBBM (40.3 ± 7.5%) sites. CONCLUSIONS: Both Bio-Oss® granules and autologous bone grafts contributed to the healing at implants installed immediately in elevated sinus sites in rabbits. Bio-Oss® maintained the dimensions, while autologous bone sites lost 2/3 of the volume between the two periods of observation.

Sequential healing of open extraction sockets. An experimental study in monkeys.

AIM: To describe the sequential healing of open extraction sockets at which no attempts to obtain a primary closure of the coronal access to the alveolus have been made. MATERIAL AND METHODS: The third mandibular premolar was extracted bilaterally in 12 monkeys, and no sutures were applied to close the wound. The healing after 4, 10, 20, 30, 90 and 180 days was morphometrically studied. RESULTS: After 4 days of healing, a blood clot mainly occupied the extraction sockets, with the presence of an inflammatory cells' infiltrate. A void was confined in the central zones of the coronal and middle regions, in continuity with the entrance of the alveoli. At 10 days, the alveolus was occupied by a provisional matrix, with new bone formation lining the socket bony walls. At 20 days, the amount of woven bone was sensibly increasing. At 30 days, the alveolar socket was mainly occupied by mineralized immature bone at different stages of healing. At 90 and 180 days, the amount of mineralized bone decreased and substituted by trabecular bone and bone marrow. Bundle bone decreased from 95.5% at 4 days to 7.6% at 180 days, of the whole length of the inner alveolar surface. CONCLUSIONS: Modeling processes start from the lateral and apical walls of the alveolus, leading to the closure of the socket with newly formed bone within a month from extraction. Remodeling processes will follow the previous stages, resulting in trabecular and bone marrow formation and in a corticalization of the socket access.

Evaluation of the presence of VEGF, BMP2 and CBFA1 proteins in autogenous bone graft: histometric and immunohistochemical analysis.

AIMS: The purpose of this study was to evaluate the expression of proteins that participate in the osteoinduction stage (VEGF, BMP2 and CBFA1) of the process of bone regeneration of defects created in rat calvariae and filled with autogenous bone block grafts. MATERIALS AND METHODS: 10 adult male rats (Rattus norvegicus albinus, Wistar) were used, who received two bone defects measuring 5 mm each in the calvariae. The bone defects constituted two experimental groups (n = 10): Control Group (CONT) (defects filled with a coagulum); Graft Group (GR) (defects filled with autogenous bone removed from the contralateral defect). The animals were submitted to euthanasia at 7 and 30 days post-operatively. RESULTS: Quantitative analysis demonstrated significantly greater bone formation in Group GR, but the presence of the studied proteins was significantly greater in the CONT Group in both time intervals of observation. CONCLUSION: It was not possible in this study in cortical bone block groups to detect the osteoinductive proteins in a significant amount during the repair process.

Tissue engineering: using collagen type I matrix for bone healing of bone defects.

Among the many tissues in the human body, bone has been considered as a powerful marker for regeneration and its formation serves as a prototype model for tissue engineering based on morphogenesis. Therefore, collagen type I is one of the most useful biomaterials used in tissue engineering as extracellular matrix components capable to promote bone healing. The literature reveals excellent biocompatibility and safety due to its biological characteristics, such as biodegradability and weak antigenicity, making collagen type I the primary resource in medical applications. Thus, it was also used for tissue engineering including skin replacement, bone substitutes, and artificial blood vessels and valves. The authors describe the treatment of an abscessed apical periodontal cyst and show good outcomes of bone healing, using tissue engineering, as collagen type I matrix.

Histologic study of use of microfibrillar collagen hemostat in rat dental sockets

The aim of this paper was to evaluate if the placement of microfibrillar collagen hemostat (MCH) into a dental socket interfered with healing. General anesthesia was administered to 30 adult male Albinus Wistar rats and the maxillary right central incisor was extracted. In the control group after each tooth was extracted, the socket was sutured. In the MCH group after each tooth was extracted, MCH was placed into the socket before suturing. Postoperatively, 5 animals were sacrificed from each group at 7, 21 and 28 days. The right maxilla was removed from each animal and histologic slides were stained with Masson's trichromic and hematoxylin and eosin. Quantitative and qualitative analyses were done. The percentage of bone area in the dental socket was quantified using the Image Lab 98 image analysis system. The bone area formation for the control and MCH groups was: 8.1 percent and 3.3 percent at 7 days, 34.4 percent and 33 percent at 21 days and 41 percent and 41.3 percent at 28 days, respectively. We concluded that MCH interferes with the beginning of dental socket healing but does not interfere with the final healing of the dental socket

Histologic study of use of microfibrillar collagen hemostat in rat dental sockets.

The aim of this paper was to evaluate if the placement of microfibrillar collagen hemostat (MCH) into a dental socket interfered with healing. General anesthesia was administered to 30 adult male Albinus Wistar rats and the maxillary right central incisor was extracted. In the control group after each tooth was extracted, the socket was sutured. In the MCH group after each tooth was extracted, MCH was placed into the socket before suturing. Postoperatively, 5 animals were sacrificed from each group at 7, 21 and 28 days. The right maxilla was removed from each animal and histologic slides were stained with Masson's trichromic and hematoxylin and eosin. Quantitative and qualitative analyses were done. The percentage of bone area in the dental socket was quantified using the Image Lab 98 image analysis system. The bone area formation for the control and MCH groups was: 8.1% and 3.3% at 7 days, 34.4% and 33% at 21 days and 41% and 41.3% at 28 days, respectively. We concluded that MCH interferes with the beginning of dental socket healing but does not interfere with the final healing of the dental socket.