Osteocalcin and cross-linked C-terminal telopeptide of type I collagen in gingival crevicular fluid during piezocision accelerated orthodontic tooth movement: A randomized split-mouth study.

Background: Piezocision, a minimally invasive surgical procedure, has been used to accelerate tooth movement'' is appropriate as a background to the abstract section. Aim: The aim of this randomized split-mouth study was to evaluate gingival crevicular fluid (GCF) osteocalcin (OC) and type I collagen cross-linked C-terminal telopeptide (ICTP) levels during canine distalization with and without piezocision acceleration. Material and Methods: Fifteen systemically healthy subjects (M:F 7:8, 16.27 ± 1.14 years) requiring extraction of maxillary first premolars before retraction of canines were included in the study. Piezocisions were randomly carried out on one of the maxillary canines while bilateral canines served as controls. Canine distalization was conducted using closed-coil springs applying a force of 150 g/side by using miniscrews as anchorage. GCF sampling was performed from maxillary canine mesial and distal sites at baseline, 1, 7, 14, and 28 days. The GCF levels of OC and ICTP were detected by enzyme-linked immunosorbent assay (ELISA). The rate of tooth movement was evaluated at 2-week intervals. Results: The amounts of canine distalization from baseline to 14 and 28 days in the piezocision group were significantly higher than the control group (P < 0.05). The GCF OC level of the piezocision group on the tension side and the ICTP level of the same group on the compression side were higher than the respective sides of the control group on day 14 (P < 0.05). Conclusions: Piezocision was found to be an effective treatment procedure for accelerating canine distalization accompanied by increased levels of OC and ICTP.

Single Nucleotide Polymorphisms in IL-1A RS1800587, IL-1B RS1143634 and Vitamin D Receptor Rs731236 in Stage III Grade B/C Periodontitis.

The purpose of the study is to determine the prevalence of interleukin (IL)-1A (rs1800587), IL-1B (rs1143634) and vitamin D receptor (VDR) (TaqI, rs731236) gene polymorphisms in the Turkish population and their association with Stage III Grade B/C periodontitis. Systemically and periodontally healthy individuals (N = 100) and Stage III Grade B/C periodontitis patients (N=100) based on clinical and radiographic examination were included in this research. Clinical attachment level, probing depth, bleeding on probing, plaque and gingival indices of the subjects were measured. Genotyping of IL-1A (rs1800587), IL-1B (rs1143634) and VDR (rs731236) polymorphisms was conducted by Real Time PCR. Allelic and genotypic distributions of IL-1A (rs1800587) gene polymorphism were not associated with periodontitis (p>0.05). In IL-1B (rs1143634) gene polymorphism, the C allele was detected more frequently in healthy individuals compared with the periodontitis patients (p=0.045). CC genotype and C allele in VDR (rs731236) gene polymorphism was higher in periodontitis patients (p=0.031, p=0.034, respectively). In comparison with Grade B periodontitis patients and healthy subjects, CC genotype and C allele were observed more frequently in the Grade B periodontitis in terms of alleles (C/T) and genotypes for VDR (rs731236) polymorphism (p=0.024, p=0.008, respectively). This study presents that the VDR (rs731236) polymorphism are associated with enhanced susceptibility to Stage III periodontitis in the Turkish population. Furthermore, VDR (rs731236) polymorphism may be used as an identification criteria to discriminate Grade B and Grade C in Stage III periodontitis.

Is sialic acid a promising marker for periodontal diseases?

OBJECTIVE: Periodontal diseases are inflammatory chronic infections. Sialic acid (SA) is an acute phase reactant by itself. The aim of this study is to investigate the relationship between salivary and serum SA levels and clinical parameters in different forms of periodontal diseases. SUBJECT AND METHODS: Systemically healthy subjects were included in the study; patients with chronic gingivitis (CG) (n = 10), chronic periodontitis (CP) (n = 10), and aggressive periodontitis (AgP) (n = 10), and ten volunteers with healthy periodontium as the control group. Total SA levels were determined by Warren's thiobarbituric acid method in whole saliva, parotis saliva, and serum samples of subjects before and 3 months after nonsurgical periodontal treatment. Full mouth clinical parameters including plaque index, gingival index, probing depth, and bleeding on probing were also recorded. RESULTS: Before treatment, in both periodontitis groups salivary and serum SA levels were higher than those of controls (P = 0.001). Both salivary and serum SA levels decreased significantly in the patient groups after treatment (P < 0.001). Multiple comparisons of baseline clinical parameters in all groups revealed significant differences (P = 0.001) and these parameters decreased significantly on the 90th day (P < 0.01). There were positive correlations between SA levels and periodontal indices of the CG, CP, and AgP groups (P < 0.05). CONCLUSION: Our results suggest that SA level in both saliva and serum may be a potentially useful marker to determine inflammatory changes and investigate different forms of periodontal diseases.

The gingival crevicular fluid levels of growth factors in patients with amlodipine-induced gingival overgrowth: A pilot study.

BACKGROUND: Amlodipine, calcium channel blocker (CCB), is used in the management of cardiovascular diseases which causes gingival overgrowth (GO). The growth factors may have a role in the pathogenesis of amlodipine-induced GO. OBJECTIVES: This pilot study aimed to investigate the growth factors including transforming growth factor-b1 (TGF-b1), platelet-derived growth factor-BB (PDGF-BB), and basic fibroblast growth factor (bFGF) in gingival crevicular fluid (GCF) of patients with amlodipine-induced GO and compare with of healthy subjects. METHODS: GCF samples were collected from 56 sites presenting GO (GO + group) and from 38 sites not presenting GO (GO- group) of 5 patients using amlodipine for more than one year, and from 45 sites (control group) of 5 healthy subjects. The levels of TGF-b1, PDGF-BB, and bFGF were determined by using ELISA kits. RESULTS: The mean concentration of TGF-b1 in GCF samples of GO + group (9.50 ± 7.30 ng/ml) was higher than both GO- group (2.07 ± 0.50 ng/ml) and control group (2.74 ± 1.01 ng/ml) (P = 0.014). No significant difference was found among the groups in the GCF levels of PDGF-BB (P = 0.767). bFGF was detected in only 33% of the sites from patients. CONCLUSION: These preliminary results suggest that TGF-b1 may play a crucial role in the pathogenesis of amlodipine-induced GO.

Effects of 810-nanometer diode laser as an adjunct to mechanical periodontal treatment on clinical periodontal parameters and gingival crevicular fluid volume of residual periodontal pockets.

BACKGROUND: Aim of this randomized controlled parallel-designed study was to evaluate the effects of diode laser as an adjunct to mechanical periodontal treatment on clinical parameters and gingival crevicular fluid (GCF) volume of the residual pockets diagnosed following initial periodontal treatment in chronic periodontitis (CP) patients. MATERIALS AND METHODS: A total of 84 residual pockets on single-rooted teeth in 11 CP patients were included and randomly assigned into three groups. Residual pockets were treated either only by mechanical treatment (Group M) (n = 28) or only by diode laser disinfection (Group L) (n = 28) or by a combination of these techniques (Group M + L) (n = 28). Plaque index, gingival index (GI), bleeding on probing (BoP), probing depth (PD), clinical attachment level and gingival recession were assessed at baseline and 8 weeks after treatment of residual pockets. GCF samples were collected at baseline, 1 and 8 weeks after treatment. RESULTS: All treatment modalities resulted in significant reductions in PD and attachment gain. GI and BoP showed a greater reduction in both Group M and Group M + L than Group L (P < 0.001), but there was no difference between the Groups M and M + L (P > 0.05). No difference was also found among groups for other clinical parameters. GCF volume decreased significantly in the Groups M and M + L (P < 0.05) but there was no difference among the groups (P > 0.05). CONCLUSION: Results demonstrated clinical improvements on residual pockets in CP patients treated with all three modalities. Moreover, our findings suggest that application of diode laser as an adjunct to mechanical periodontal treatment doesn't demonstrate any additional clinical effect on the residual pockets.

Evaluation of gingival crevicular fluid transforming growth factor-ß1 level after treatment of intrabony periodontal defects with enamel matrix derivatives and autogenous bone graft: A randomized controlled clinical trial.

AIM: The present study aimed to evaluate the effects of enamel matrix derivatives (EMD) either alone or combined with autogenous bone graft (ABG) applied to intrabony defects in chronic periodontitis patients on clinical/radiographic parameters and gingival crevicular fluid (GCF) transforming growth factor-ß1 (TGF-ß1) level and to compare with open flap debridement (OFD). MATERIALS AND METHODS: A total of 30 deep intrabony defects in 12 patients were randomly treated with EMD + ABG (combination group), EMD alone (EMD group), or OFD (control group). Clinical parameters, including plaque index, gingival index, bleeding on probing, probing depth, relative attachment level, and recession were recorded at baseline and 6 months postsurgery. Intrabony defect fill percentage was calculated on the standardized radiographs. TGF-ß1 level was evaluated in GCF just before surgery and 7, 14, 30, 90, 180 days after surgery using enzyme-linked immunosorbent assay. RESULTS: All treatment procedures led to significant improvements at 6 months (P < 0.01). Gain in attachment level (P < 0.01) and radiographic defect fill (P < 0.05) of the combination and EMD groups were found to be significantly higher than those of the control group, while the use of EMD either with ABG or alone was observed to produce significantly less recession than the OFD (P < 0.05). CONCLUSION: The findings suggest no clinical and radiographic differences between the combination and EMD groups whereas GCF TGF-ß1 level demonstrates an increase during the healing phase and is positively affected from EMD.

Flow cytometry analysis of gingival and periodontal ligament cells.

Gingival and periodontal ligament (PDL) fibroblasts are the major cellular components of periodontal soft connective tissues, but the precise differences between these cells are not yet known. In the present study, we have therefore examined the phenotypic and functional features of the cells obtained from gingival and PDL biopsy samples. Spindle-shaped cells characteristic of fibroblasts were the main cell type observed in vitro, although epithelial cells were also present in primary gingival cell cultures. Flow cytometry was used to measure the size and granularity of the cultured cells, and showed that the gingival fibroblasts were smaller and less granular compared with the PDL cells. The expression of certain key extracellular matrix (ECM) proteins, fibronectin, collagen type I, and tenascin was measured by flow cytometry. Analysis of the fluorescence profiles of these cultures showed that the majority of cells expressed fibronectin and that the average fluorescence intensity of this antigen in the PDL cells was higher than that in the gingival fibroblasts. Moreover, the fibronectin-positive PDL cells apparently comprised two subpopulations which expressed fibronectin at different levels, suggesting that the cells in the PDL cultures were functionally heterogeneous. The level of collagen type I was also found to be up-regulated in the PDL compared with the gingival cells and, as with fibronectin, was expressed at two different levels by subsets of the PDL cells. In contrast, tenascin was expressed at very similar levels by both the gingival fibroblasts and PDL cells. In addition, measurement of alkaline phosphatase, a marker enzyme for mineralized tissue-forming cells, showed that the PDL cells had higher activity than the gingival fibroblasts and that the alkaline phosphatase activity in the PDL cells was far more markedly up-regulated by dexamethasone. Our findings demonstrate that, despite their similar spindle-shaped appearance, fibroblasts derived from gingival and PDL tissues appear to display distinct functional activities which are likely to play a vital part in the maintenance of tissue integrity and regenerative processes.

Flow cytometry analysis of guided tissue regeneration-associated human periodontal cells.

BACKGROUND: Expanded polytetrafluoroethylene (ePTFE) barrier membranes have been widely used for guided tissue regeneration (GTR) of the human periodontal ligament (PL). However, the precise cellular and molecular events involved in the re-growth of the new tissue are still unclear. METHODS: Retrieved membranes and the newly-regenerated soft tissue (RT) underlying the membranes were used to examine the cells associated with GTR compared with normal human PL and gingival cells. Flow cytometry (FCM) was used, for the first time, to analyze the spindle-shaped fibroblast-like cells which were adherent to these membranes and the cells which grew out of the RT. RESULTS: The results showed that the membrane-associated (M) cells had the lowest rate of proliferation and appeared to be larger and more granular than the other types of cell. Moreover, both the M- and RT-derived cells were found to express higher levels of the extracellular matrix (ECM) proteins collagen type 1, fibronectin, tenascin, and decorin. In addition, evidence based on FCM profiles identified distinct sub-populations of GTR cells in which fibronectin expression was markedly up-regulated compared with normal PL cells and which also differed in size and granularity. CONCLUSIONS: The results of this study show that cells associated with GTR barrier membranes and with the underlying tissue appear to have distinct phenotypic and functional activities consistent with the production of new periodontal connective tissue and periodontal regeneration.

Expression of growth factors in the gingival crevice fluid of patients with phenytoin-induced gingival enlargement.

The mechanism underlying phenytoin (PHT)-induced gingival enlargement (GE) is not yet known. The aim of the present study was to investigate transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor-BB (PDGF-BB) and basic fibroblast growth factor (bFGF) profiles in the gingival crevice fluid (GCF) of patients with PHT-induced GE and to compare the results with healthy controls. Five PHT-treated patients and five healthy subjects with normal periodontal tissue were included in this study. GCF samples were collected from (i) enlarged gingival sites in patients receiving PHT (GE+); (ii) non-enlarged gingival sites in the same patients (GE-); (iii) normal gingival sites of healthy subjects (control). The levels of TGF-beta1, PDGF-BB and bFGF in the GCF samples were analysed by ELISA. The results showed that the total amounts of TGF-beta1 and PDGF-BB in the GE+ group were higher than in the GE- group and significantly higher than in the control group (P < 0.05). However, no significant differences were found between the groups when the concentrations of these growth factors were compared. bFGF levels were not compared as this growth factor could be detected in only 33, 41 and 44% of the GE+, GE- and control GCF samples, respectively. These results show that TGF-beta1 and PDGF-BB are readily detectable in GCF obtained from enlarged and non-enlarged sites of PHT recipients and suggest that since the amounts were markedly higher at the GE+ than the GE- sites, the systemic administration of PHT has a pronounced localised effect on the levels of these growth factors. Moreover, our findings provide evidence that both TGF-beta1 and PDGF-BB are closely associated with the clinical manifestation of PHT-induced GE.

Expression of growth-factor receptors in normal and regenerating human periodontal cells.

Growth factors are biologically active mediators that bind to specific receptors on target cells and regulate genes involved in cell growth, wound healing and regeneration. The expression of these receptors is thus of fundamental importance for the response of the cells to the factors. The aim here was to examine, using immunohistochemistry and flow cytometry, the expression of growth factor receptors in normal gingiva, periodontal ligament and in cells derived from these tissues, and also in regenerated tissues following guided tissue regeneration (GTR). By immunocytochemistry platelet-derived growth factor receptor-alpha (PDGF-Ralpha) was not detected in any of the tissues, whereas the PDGF-Rbeta and transforming growth factor-beta receptor types I and II (TGF-beta RI, RII) appeared to be upregulated in regenerated tissues compared with gingival and periodontal ligament tissues. Epidermal growth factor receptor (EGF-R) was also notably elevated in the regenerated tissue and was strongly expressed in the gingival epithelium but not in the periodontal ligament. Neither were fibroblast growth factor receptor-I (FGF-RI) or insulin-like growth factor receptor (IGF-R) detected in the periodontal ligament, nor in the gingiva, but they sometimes stained weakly in the regenerated tissues. Flow cytometry (FCM) showed that all the cells derived from the normal gingiva and the periodontal ligament expressed the PDGF-Rbeta, whereas the TGF-beta RI and RII, FGF-RI and IGF-R were detected in only a proportion of the total cells. In contrast, none of the cells expressed the PDGF-Ralpha or the EGF-R. These observations show that the growth factor receptors are differentially expressed by the periodontal tissues and cells and suggest that the corresponding factors may also be differentially involved in periodontal wound healing and regeneration.

Retroviral transduction of human periodontal cells with a temperature-sensitive SV40 large T antigen.

The periodontal ligament (PDL) is considered to contain subpopulations of cells responsible for the development, repair and regeneration of the periodontium. Cell cultures have been used as model systems in order to understand the complex cellular and biochemical events underlying these processes. In order to obtain long-term cultures of these cells that can be cloned and characterized, primary cultures of PDL and gingival cells were infected with an amphotropic retroviral construct encoding a temperature-sensitive SV40 large T antigen (tsT). After selection for drug resistance, the cells expressed the T antigen and proliferated at 34 degrees C for more than 40 passages. However, when the T antigen was inactivated by incubation at 39 degrees C, the cultures became growth-arrested and the granularity of the cells increased, possibly as a result of differentiation. Reverse transcribed-polymerase chain reaction and flow cytometry showed that the tsT-transduced cells expressed a number of soft and hard connective-tissue antigens, including osteocalcin, osteonectin, osteopontin, collagen type I and alkaline phosphatase. Moreover, incubation of the transduced PDL cells at 39 degrees C was found to upregulate the expression of osteocalcin, osteopontin and collagen type I, but downregulate osteonectin. At this temperature, the presence of the dexamethasone downregulated type I collagen, while vitamin D3 had no effect on the expression of any of the antigens examined. Under all culture conditions, antigen expression was far higher in the transduced PDL cells than the gingival cells. The findings thus show that growth of the tsT-transduced PDL and gingival cells is temperature-dependent and that the presence of the T antigen increases their lifespan but does not ablate the expression of certain of their characteristic phenotypic and functional features.

Obesity and increasing rate of infantile Blount disease.

BACKGROUND: The incidence of infantile Blount disease is rising in parallel to the increasing obesity in children. MATERIAL AND METHODS: Seven children (3 female) between the ages of 17 and 30 months (21.8 ± 4.3 months) were included in the study. RESULTS: All patients had complaints of inward bowing of the legs and excess weight gain. The biochemical and hormonal assessments of all patients yielded normal results. Patients were diagnosed with infantile Blount disease based on clinical, laboratory, and radiological findings. CONCLUSION: This disease should be differentiated from physiological genu varum, and the potential psychosocial and physical complications are prevented with early diagnosis and treatment.

Complete androgen insensitivity syndrome and discordant Müllerian remnants: two cases with novel mutation in the androgen receptor.

Complete androgen insensitivity syndrome (CAIS) associated with Müllerian remnant is rare during childhood. The Müllerian system usually regresses because of the presence of the anti-Müllerian hormone (AMH) originating from the Sertoli cells of the gonads. Rarely, residual Müllerian structures may exist. We present two cases from the same family, raised as females. They were 12 and 18 years old, respectively, and they had Tanner V breast development but Tanner I-II pubic hair. The older patient had primary amenorrhea. Both have a 46,XY genotype. Pelvic ultrasonography revealed no uterus and ovaries. The patients underwent bilateral laporoscopic gonadectomy. Both had residual Müllerian structures. Mutation analyses were performed, and both patients were found to be carrying a point mutation in exon 4 of the AR gene consisting of a G nucleotide deletion at position c.1890delG, followed by a frame-shift mutation and a stop codon. This mutation has not been described yet in the literature. Although the association with CAIS and Müllerian remnant is rare, no genetic defect specific to androgen insensitivity with Müllerian remnants has been identified so far.

Oral health in patients on inhaled corticosteroid treatment.

OBJECTIVE: The aim of this study was to investigate the effects of long-term inhaled corticosteroids on bone mineral density (BMD) of the mandible in relation with the tooth loss. DESIGN: Cross sectional analytic study. SUBJECTS AND METHODS: Patients (n = 30) with chronic obstructive pulmonary disease under inhaled corticosteroid therapy for at least 1 year were compared with sex- and age-matched healthy controls (n = 30). BMD of the mandible was measured by dual-energy X-ray absorptiometry. The clinical examination included recording the number of teeth present together with periodontal condition. Levels of serum osteocalcin, alkaline phosphatase, calcium, phosphorus and cortisol were also assessed. RESULTS: BMD of the mandible in patients on corticosteroid treatment was significantly lower than that in the control group (P = 0.001). Patients under treatment had more missing teeth than the control group but the difference did not reach statistical significance. The two groups exhibited similar clinical parameters of periodontal condition. Significantly lower levels of osteocalcin (P < 0.0001), calcium (P = 0.004) and cortisol (P = 0.03) were observed in the patients on corticosteroid treatment. CONCLUSION: Long-term use of inhaled corticosteroids may impair bone metabolism and lead to a marked decrease in the mandibular BMD.

Changes in transforming growth factor-beta1 in gingival crevicular fluid following periodontal surgery.

OBJECTIVES: Growth factors play a major part in wound healing, including in the periodontium. However, the presence of growth factors in gingival crevicular fluid (GCF) in humans during periodontal wound healing has not yet been determined. Our hypothesis is that such factors are present in GCF and that changes in their levels might be of value as a prognostic marker of wound-healing activity and therapeutic progress following periodontal surgery. The aim of this study was therefore to measure transforming growth factor-beta1 (TGF-beta1) in GCF collected from sites that have undergone guided tissue regeneration (GTR) and conventional flap (CF) surgery and to compare these with GCF collected from unaffected healthy sites. MATERIALS AND METHODS: GCF samples were collected, using filter paper strips, at baseline (pre-surgical) and then at intervals up to 26 weeks from 16 patients undergoing GTR and from 11 patients undergoing CF surgery. After elution and acid treatment, TGF-beta1 levels were measured by ELISA. RESULTS: Treatment of periodontal defect sites significantly reduced the mean probing pocket depth (PPD) and improved the mean lifetime cumulative attachment loss (LCAL). Average GCF volumes also significantly increased at all sites at 2 weeks post-surgery and thereafter declined to baseline levels, except at the GTR test sites that were still elevated at 7 weeks. TGF-beta1 could be detected in almost all GCF samples, and 2 weeks after surgery, the average levels increased two-fold at the surgically treated but not at the control sites, which remained unchanged. CONCLUSION: TGF-beta1 is readily detectable in GCF and increases transiently following periodontal surgery. This suggests that changes in the levels of this growth factor in GCF might be useful for monitoring the progress of periodontal repair and regeneration.

Alkaline phosphatase activity is upregulated in regenerating human periodontal cells.

The activity of alkaline phosphatase (ALP) is considered to indicate the presence of osteoblast cells and the formation of new bone. In the present study this enzyme was investigated in cells obtained from retrieved polytetrafluoroethylene membranes (M cells) of periodontal disease patients treated by guided tissue regeneration (GTR) and from the regenerated tissue underlying the membrane (RT cells). Normal periodontal ligament (PL) and gingival cells were also grown from the corresponding healthy tissues of human subjects. ALP activity was measured colourimetrically, using paranitrophenyl phosphate as the substrate, after 4 and 7 d of culture in the absence and presence of dexamethasone (DEX), a synthetic glucocorticoid which induces osteoblast differentiation. The results showed that basal levels of ALP activity were expressed by all the cells and that DEX upregulated ALP levels in the M, RT and PL cells but not in the gingival cells. Moreover, both the basal and DEX-induced ALP activities were statistically significantly higher in the RT cells than in any of the other cells. Our results suggest that both the GTR-associated and normal PL cells express osteoblast-like characteristics and, furthermore, that the RT cultures in particular contain a high proportion of osteoprogenitor cells.

The evolution of clinical periodontal therapy.

Periodontal diseases are considered as old as the history of mankind, Magical, religious and herbal treatments were demonstrated in almost all of the early writings. However, methodical, carefully reasoned therapeutic approaches did not exist until the middle-ages and modern treatment with a scientific base and sophisticated instrumentation did not develop until the 18th century. Prior to the 1950s, diseases were mostly treated by root debridement and the extraction of the affected teeth. Until the 1970s, it was primarily the symptoms of periodontal diseases that were treated. The goal was radical elimination of the periodontal pocket (resective therapy). The means were gingivectomy, flap procedures and osseous surgery. The disadvantages were the massive sacrifice of periodontal tissues, lack of regeneration and clinically elongated teeth. These disadvantages, along with the realization of the importance of aetiologic agents, raised questions about the necessity of total pocket elimination, and the control of subgingival infection by a thorough scaling and root planing (nonsurgical therapy), with and without antibiotics, became a commonly used treatment during the 1980s. Comparative longitudinal studies, surgical versus nonsurgical, demonstrated that both surgical and nonsurgical therapy result in limited regeneration and healing with a long junctional epithelium. The most important aspects of today's modern concept of periodontal therapy are causal, regenerative, and specific for disease type and severity. Although the regeneration of the periodontium can be accomplished with the biological principles of guided tissue regeneration and graft materials, compared to conventional methods, the restoration of a completely normal periodontal status has not yet been achieved. We are about to reach our ultimate goals and presently, the more promising research directions for a substantial regeneration seems to lie in biological mediators. Although the future of periodontal therapy is bright, it is still of critical importance to have a preventive strategy to keep individuals healthy beforehand.

Flow cytometry for assessing biocompatibility.

Flow cytometry (FCM) was examined as a possible procedure for measuring in vitro the biocompatibility of implant materials for orthopedic and dental surgery. The human osteoblast-like cell line MG63 was grown on hydroxyapatite (HA) and P2O5 glass-reinforced HA composite discs and compared with the same cells grown on polystyrene culture dishes. While morphological observation at the light and electron microscopic levels showed no major deleterious effects, FCM indicated that cell size was somewhat reduced, particularly by growth on the HA composite. Morever, this material also appeared to delay the progression of the cells from the G0/G1 into the S phase of the cell cycle. In addition to this low level of inhibition of cell growth relative to control cultures, FCM analysis also demonstrated that the glass-reinforced HA caused some down-regulation of the expression of osteocalcin and fibronectin, two antigens which play a vital part in the integrity and function of bone and soft connective tissue, respectively. These results thus show, first, that although HA and the HA composite used in these experiments were generally biocompatible, they nevertheless had certain suboptimal effects on the cells; and second, that FCM could be a highly useful procedure for effectively screening and evaluating important biological responses to implant materials.