Histological reaction to hydroxyapatite in the middle ear of rats.

OBJECTIVE: Present study was performed to evaluate the histological response of rat middle ear mucosa following implantation of Apaceram granules, a synthetic dense hydroxyapatite [Ca10(PO4)6(OH)2], prepared from commercially available synthetic auditory ossicle, and to assess the precise histological response of the rat middle ear to implantation of Apaceram granules, by microscopic examination of mucosal tissue at various time points after implantation. METHODS: Apaceram granules were implanted in the temporal bulla of 32 rats. As control, sham surgery was performed in a group of ten rats. Bulla specimens were removed at 1, 3, 7, 14, and 30 days after surgery in the implant and control groups, and at 90, 180 and 300 days in the implant group. Specimens were decalcified, sectioned at a thickness of 6 microm, and stained with haematoxylin and eosin, and Mallory's azan for histological examination of mucosal tissue. RESULTS: Evidence of inflammatory reaction was slightly greater in the implant group than in controls. Lymphocyte and macrophage counts were higher in the implant group 1 day after surgery, but decreased to similar levels by day 3, and continued to decrease thereafter, and few were observed in the implant group at 300 days. Neutrophils observed at 1 day after surgery were not evident in either group at 3 days. Gradual fibrosis development continued in both groups over all time points studied. Foreign body giant cells were never observed in either group. No bony reaction was observed in any specimen. CONCLUSION: The results of this study suggest that Apaceram is biocompatible and suitable for reconstructive ear surgery.

Orthodontic treatment for a patient with Pierre-Robin sequence complicated by juvenile periodontitis.

OBJECTIVE: To arrest the advancement of periodontitis. PATIENT: A 17-year-old boy diagnosed with Pierre-Robin sequence at birth exhibited localized juvenile periodontitis. Severe bone loss and mobile teeth were localized in the incisors and molars, which were irregularly positioned, possibly associated with a residual scar from palatoplasty for a soft palate cleft at an early age. CONCLUSION: Combined orthodontic-periodontic-prosthodontic treatment arrested the advancement of the periodontitis and established a stable occlusion.

Thickness of fibrous capsule after implantation of hydroxyapatite in subcutaneous tissue in rats.

The present study evaluates in rats the histomorphometrical thickness of fibrous capsules that surround hydroxyapatite (HA) disks after implantation. HA disks were implanted into the subcutaneous tissue of 79 rats for 1 day to 20 months. Decalcified histological sections stained with hematoxylin and eosin were examined. Fibrous capsule thickness (FCT) was measured using an objective micrometer. On the fourteenth day, primary fibrous capsules formed around implants. From that time point FCT increased with time of implantation. Within a given sample, FCT differed from one portion of the fibrous capsule to another, depending on which site faced the disks. FCT was thickest at the upper and lower portions of the disks, thinner at the lateral portions, and thinnest at the upper and lower ring-shaped portions. Two possible explanations for the above findings are discussed in this paper: (1) The area of contact between disk and tissue differs. (2) Chemical stimulation of implanted material caused by demineralization and remineralization may result from the varying thicknesses of fibrous capsules. FCT from upper and lower portions of HA disks increased by over 200% in the first 10 months and steadily increased about 20% over the next 10 months. Many studies have concluded that HA is useful for reconstructive surgery, so the long-term effects of FCT need further study.

Subcutaneous inflammatory reaction to a synthetic auditory ossicle (Bioceram) in rats.

Cellular response and inflammatory reaction to synthetic auditory ossicle (Bioceram) made from aluminium oxide are investigated. Local inflammatory effects are important in wound healing and in determining biocompatibility of an implant, necessitating the study of biologic effects of implants, especially inflammation and fibrous capsule formation. Bioceram discs were implanted subcutaneously in the interscapular region of rats for various periods of time, ranging from 1 day to 300 days. Histological sections 6 microns thick were stained with haematoxylin and eosin. Cell types around the implants were examined quantitatively by light microscopy. Inflammatory cell reaction to Bioceram decreased rapidly within 14 days, similar to the reaction in control groups. From 30 days to 300 days after implantation, there was continuous reduction to very low levels for macrophages and lymphocytes, but fibrous connective tissue capsule around implants matured. Preliminary results suggest that Bioceram is a satisfactory biocompatible material for reconstructive surgery from the viewpoint of cellular response. We also briefly discuss the different tissue responses in light of our previous study on hydroxyapatite (Apaceram).

A subcutaneous tissue reaction in the early stage to a synthetic auditory ossicle (Bioceram) in rats.

The discs of synthetic auditory ossicle (Bioceram), which are composed of aluminium oxide (Al2O3), were implanted subcutaneously in the interscapular region of 16 rats. The implanted specimens were removed at 1, 3, 7 and 14 days after implantation. The decalcified 6 microns thick sections were stained with H.E. and cell types around the implants were counted microscopically. We found that an acute inflammatory reaction occurred at one day, in which macrophages and neutrophiles predominated, and almost disappeared at about 7 days after implantation. Fibrosis began to be observed at 3 days. During this early stage, foreign body giant cells were found in only one specimen at 3 days. These findings, in comparison with those in the controls, showed that the chemical irritation of Bioceram to the subcutaneous tissue is slight, although the physical and/or chemical irritation of Bioceram lasts continuously and induces fibrosis around the bioimplant. The results so far suggest that Bioceram seems to be a satisfactorily biocompatible material, at least within the extent of 2 weeks.

Long-term observation of subcutaneous tissue reaction to synthetic auditory ossicle (Apaceram) in rats.

The present study evaluates histological characteristics of the soft tissue response to long-term implantation of Apaceram discs composed of dense hydroxyapatite in rats. Discs were implanted into the subcutaneous tissue of 76 rats for six to 20 months. Decalcified histological sections stained with haematoxylin and eosin (H & E) and Mallory's azan were examined. Different cell types surrounding implants were counted. The greatest proportion of macrophages was found at six months (13.5 per cent). This proportion gradually decreased to four per cent at 20 months. Small numbers of lymphocytes and foreign body giant cells were observed in every group, but neither neutrophils nor osteogenesis were observed in any specimens. Results of the present study and previous related studies indicate that despite reappearance of a small number of macrophages six months after implantation, Apaceram is useful for reconstructive surgery.

Fluoridation of hydroxyapatite powder by ammonium hexafluorosilicate.

Diamine silver fluoride [AgF: (NH3)2AgF] is a unique fluoride solution used clinically in Japan for primary teeth. AgF has been shown to reduce dental caries and dentine hypersensitivity. However, AgF also stains teeth black due to sulfide precipitation and thus is unacceptable for permanent teeth. In the present study, the potential value of ammonium hexafluorosilicate [SiF: (NH4)2SiF6], which has a formula similar to that of AgF but contains no Ag, was studied with respect to its ability to fluoridate apatite. Hydroxyapatite [HAP: Ca10(PO4)6(OH)2] powder was treated with several topical fluoride solutions, i.e. neutral sodium fluoride, acidulated phosphate fluoride (APF) along with AgF and SiF. Following treatment, the HAP powders were analyzed for their fluorine content, crystallinity changes, and solubility in acidic solution. The highest level of fluoridated HAP [FAP: Ca10(PO4)6(OH)xF2-x] was observed in HAP powder treated with SiF, even though more total fluorine in the form of FAP and CaF2 was observed in HAP powder samples treated with APF. Presumably as a consequence of this higher level of FAP formation after SiF treatment, the highest level of crystallinity along with the lowest solubility in acidic solution were observed in HAP powder treated with SiF solution. We concluded, therefore, that SiF may have potential value for use as a topical fluoride solution.

Subcutaneous tissue reaction to synthetic auditory ossicle (Apaceram) in rats.

A study was carried out in order to obtain further information about the soft tissue response to thin Apaceram discs of dense hydroxyapatite (HA) implanted in rats for various periods of time between one day and 10 months. The Apaceram discs were implanted subcutaneously into the interscapular region of 33 rats. A sham operation was performed on eight rats used as controls. Decalcified histological sections stained with haematoxylin and eosin and Mallory's azan were examined and the different cell types found around the implants were counted. It was found that an acute inflammatory reaction occurred after one day and disappeared at about two weeks after implantation. In the test groups, macrophages and lymphocytes disappeared about one week later, and no inflammatory reaction was observed from one to three months. However, a tissue reaction occurred at six months with the appearance of macrophages and lymphocytes, and decreased gradually at 10 months. Meanwhile, a few foreign body giant cells at the Apaceram-tissue interface and a thick layer of fibrous connective tissue around the Apaceram disc were observed at 10 months. No osteogenesis was observed in any specimen. The results obtained so far suggest that Apaceram is still a useful material for reconstructive surgery, despite the possible appearance of a slight macrophage reaction at six months.

Remodeling mechanisms of transseptal fibers during and after tooth movement.

The remodeling mechanisms of transseptal fibers during and after tooth movement were investigated histologically. An autoradiographic study was conducted to assess the synthetic response. One hundred fifty male Wistar strain growing rats were divided into three groups--one control and two experimental groups. Animals in the experimental groups were subjected to tooth movement with 25 g and 150 g of force. Maxillary first and second molars were separated and retained mechanically. Transseptal fibers were stretched in proportion to the amount of force applied for up to 2 days. Dynamic remodeling with proliferation of fibroblasts during tooth movement and slow rearrangement during retention periods occurred in both experimental groups. Collagen phagocytosis within the fibroblasts was observed ultrastructurally during the experimental periods. The number of silver grains in fibroblasts in the collagen fibers increased 160% the first day and 206% during the first 3 days. Proliferating fibroblasts remodeled the transseptal fibers through the synthesization and degradation of collagen fibers.

Effect of retinoic acid on contraction of collagen gel induced by fibroblasts.

Retinoic acid inhibited the contraction of collagen gel containing fibroblasts. Moreover, in its presence fibroblasts extensions were shorter, fewer collagen fibers were recognized, cell adhesiveness was inhibited concentration-dependently, and microfilaments appeared to be disrupted, resulting in morphological changes including loss of multipolar cell processes due to changes in cytoskeletal linkages.

[A study to establish the model of transseptal fibers in vitro by human gingival fibroblast].

The present study was attempted to establish the model of transseptal fibers in vitro to clarify the remodeling mechanisms of the fibers during orthodontic treatment. Human premolars were transversally cut. The thickness of films was 150 microns and a pair of dental rings was placed at intermediate of 500 microns in tissue culture dishes. Human gingival fibroblasts were seeded in these dishes and cultured. Culturing of these cells were changed at 1, 5, 10 and 20 days and used to histological observation. The following results were obtained: 1. It was observed that human gingival fibroblasts and fibrillar materials oriented approximately the surfaces of sliced teeth and extended the process of cells along the direction from sliced teeth to another one. The bridges of cells and fibers between two sliced teeth were completed after 10 days culturing. 2. The fibrillar materials were examined by TEM and bundles constructed from banded fibrils which each band was 60 nm in diameter. The red fibers were stained with Van Gieson's stain method and so many red fibers filled in the space between the two sliced teeth. This suggests that the most of fibrillar materials were collagen fibers formed from human gingival fibroblasts. The structural materials were assumed to be resembled to transseptal fibers in vivo. This culture system is usefull to study the remodeling mechanisms of transseptal fibers in tooth movement.

Effects of preparation conditions in aqueous solution on properties of hydroxyapatites.

Hydroxyapatite powders (HAP: Ca10(PO4)6(OH)2) were prepared from calcium nitrate and di-ammonium hydrogen phosphate at various temperatures in aqueous solution in the absence and presence of carbon dioxide. In the absence of carbon dioxide, the crystallinities as well as the calcium to phosphate ratio (Ca/P ratio) of HAP powders increased with an increase in the preparation temperature. Calcium ion deficiency caused low Ca/P ratios of HAP powders. Such HAP powders decomposed thermally to beta-tricalcium phosphate (beta-TCP: Ca3(PO4)2) at 800 degrees C in 3 hours whereas HAP powders with sufficient calcium were stable at 1200 degrees C for 3 hours. In the presence of carbon dioxide as well the crystallinities of HAP powders increased with an increase in the preparation temperature, but carbonate-bearing HAPs were obtained instead of pure HAP. In addition, calcium carbonate was obtained along with carbonate-bearing HAP prepared below 60 degrees C.