Faculty Bibliography

Hydroxyapatite (HA)-reinforced polymers have been proposed as a method of improving the biological properties of bone cements and implant materials. For example, bone cements based on polymethylmethacrylate (PMMA) have long been used to secure orthopedic implants to the skeleton. This composite could also be used as a polished coating on other materials or in bulk form, shaped or molded, to custom fit a specific clinical need. However, complications may occur as a result of the limited mechanical and biological properties of PMMA. The purpose of this investigation was to determine whether the incorporation of HA in a PMMA matrix would enhance the biological properties of osteoblast response as compared to PMMA alone. Fetal rat calvarial osteoblasts were plated on discs of PMMA, PMMA/HA, commercially pure titanium (CpTi) and tissue culture polystyrene (control). Osteoblast attachment and day 2 proliferation were similar on all implant materials, whereas, day 8 proliferation on PMMA/HA was significantly higher than on PMMA and similar to CpTi and control. Extracellular matrix production was examined by immunohistochemistry which indicated that osteoblasts cultured on PMMA/HA showed a more distinct networked pattern of organized fibronectin. Histochemical staining of mineralization was examined by confocal microscopy which demonstrated a higher degree of mineralization in nodules formed on PMMA/HA as compared to PMMA. Together, these results indicate that the addition of HA in a PMMA matrix improves osteoblast response as compared to PMMA alone. Therefore, the incorporation of HA into a PMMA matrix may be a useful method to provide PMMA materials with enhanced osteogenic properties

The DentiPatch lidocaine transoral delivery system (Noven Pharmaceuticals) is indicated for mild topical anesthesia of mucosal membranes in the mouth. The DentiPatch is a mucoadhesive patch containing 46.1 mg of lidocaine (20% concentration). Current studies in adults report that DentiPatch application produces very low plasma concentrations of lidocaine. However, it is not known what plasma levels are obtained when the same dosage is used in children. The purpose of this study was to determine whether the plasma lidocaine concentrations generated by the DentiPatch are within a safe range for children. The sample in this study was 11 children aged 2-7 years requiring general anesthesia for comprehensive dental care. A lidocaine DentiPatch was placed on the buccal mucosa above the maxillary incisors for 5 minutes. Blood samples were drawn before placing the DentiPatch and at various time intervals after removing it. Blood samples were analyzed by fluorescence polarization immunoassay to determine the plasma concentrations of lidocaine and its major metabolite, monoethylglycinexylidide. The lidocaine and monoethylglycinexylidide absorbed from the DentiPatch did not reach toxic plasma levels in children. However, plasma concentrations were much higher than in adults and were high enough to require inclusion in the calculation of total lidocaine administered to a pediatric patient

The purpose of this study was to describe and assess the use of fissure sealant retention as a quality measure of the delivery system for pediatric dentistry. The Pediatric Dentistry Section at the Ohio State University College of Dentistry adopted Sealant retention as a measure of quality. Sealant retention in first and second molars was evaluated at each six-month recall appointment. Sealants were categorized as satisfactory or unsatisfactory. Two hundred five sealants were evaluated between March 1998 and March 1999. The mean age of the patients at the time of sealant evaluation was 14.0 +/- 2.9. Mean sealant retention period was 29.8 +/- 23.2 months, with a range of 0.9 to 148 months. Median sealant retention period was 23.2 months. Overall, 75.6 percent of the sealed teeth were classified as satisfactory. Use of this data in making improvements is discussed. Our results indicate that the use of sealant retention is a suitable measure for quality of care in pediatric dentistry

Facial cellulitis in the pediatric hospital population can be classified as odontogenic and nonodontogenic. Emergency departments welcome timely diagnosis from consultants as cellulitis is associated with significant morbidity in children. The purpose of this retrospective study is to assist pediatric dentists in recognizing differences between odontogenic and nonodontogenic facial cellulitis and to determine whether odontogenic infections make up a major portion of facial swellings seen upon admission to the hospital. The completed medical records of 100 patients admitted to Children's Hospital of Pittsburgh from 1980-1989 with an ICD-9 diagnosis of facial cellulitis were reviewed. The types of cellulitis were differentiated using admission data. The information reviewed included age, sex, temperature, white blood cell count, location of facial infection, and season of the year. Odontogenic cellulitis comprised approximately 50% of the total hospital facial infections of the records reviewed during the 10-year period. Upon admission, patients with odontogenic and nonodontogenic facial cellulitis have similarities (season of onset during the year, febrile temperature, and location of infection) and differences (mean admission temperature, age at time of affliction, white blood cell count, and most commonly occurring microorganisms.

We previously showed that anti-fibronectin antibodies or soluble fibronectin fragments containing the central cell-binding domain inhibit formation of mineralized nodules by fetal calvarial osteoblasts in vitro. These findings suggest a critical role for fibronectin in osteoblast differentiation and morphogenesis. In this study we tested the hypothesis that fibronectin's effects on osteogenesis are mediated via direct interactions with integrin receptors for fibronectin on osteoblasts. Immunocytochemical analysis identified the integrin fibronectin receptor alpha5ss1 in fetal rat calvarial tissue and in cultured osteoblasts at all stages of differentiation. Three other integrins, alpha3ss1, alpha8ss1 and alphavss3, which can bind fibronectin, as well as other matrix components, were also identified in tissue and at all stages of cell culture. Immunoprecipitation data showed that alpha5ss1 levels are constant throughout osteoblast differentiation whereas levels of alpha3ss1 and alpha8ss1 decline in mature mineralized cultures. To determine whether integrin fibronectin receptors are required for osteoblast formation of mineralized nodules, we examined the extent of nodule formation in the presence and absence of function-perturbing anti-integrin antibodies. The antibodies were present continuously in cultures beginning at confluence (day 3), and nodule formation was measured at days 10 and 20. An anti-alpha5 integrin subunit antibody reduced nodule formation to less than 5% of control values at both time points. Inhibition of nodule formation was reversible and did not affect cell attachment and viability. Function-perturbing antibodies against alpha3ss1 and alpha8ss1 also reduced nodule formation, to less than 20% of control values. In contrast, function-perturbing antibodies to alphavss3 and alphavss5 did not affect nodule formation, indicating that the inhibitions noted were indeed specific. To determine the effect of antibody treatment on gene expression, steady-state mRNA expression was examined and found to be suppressed for osteoblast markers alkaline phosphatase and osteocalcin. Together, these results indicate that direct osteoblast interactions with the extracellular matrix are mediated by a select group of integrin receptors that includes alpha5ss1, alpha3ss1 and alpha8ss1. We further conclude that the specific alpha5ss1 fibronectin receptor mediates critical interactions between osteoblasts and fibronectin required for both bone morphogenesis and osteoblast differentiation

Cell interactions with extracellular matrix and with other cells play critical roles in morphogenesis during development and in tissue homeostasis and remodeling throughout life. Extracellular matrix is information-rich, not only because it is comprised of multifunctional structural ligands for cell surface adhesion receptors, but also because it contains peptide signaling factors, and proteinases and their inhibitors. The functions of these groups of molecules are extensively interrelated. In this review, three primary cell culture models are described that focus on adhesion receptors and their roles in complex aspects of morphogenesis and remodeling: the regulation of proteinase expression by fibronectin and integrins in synovial fibroblasts; the regulation of osteoblast differentiation and survival by fibronectin, and the regulation of trophoblast differentiation and invasion by integrins, cadherins and immunoglobulin family adhesion receptors.

The secretion of fibronectin by differentiating osteoblasts and its accumulation at sites of osteogenesis suggest that fibronectin participates in bone formation. To test this directly, we determined whether fibronectin-cell interactions regulate progressive differentiation of cultured fetal rat calvarial osteoblasts. Spatial distributions of alpha 5 integrin subunit, fibronectin, osteopontin (bone sialoprotein I) and osteocalcin (bone Gla-protein) were similar in fetal rat calvaria and mineralized, bone-like nodules formed by cultured osteoblasts. Addition of anti-fibronectin antibodies to cultures at confluence reduced subsequent formation of nodules to less than 10% of control values, showing that fibronectin is required for normal nodule morphogenesis. Anti-fibronectin antibodies selectively inhibited steady-state expression of mRNA for genes associated with osteoblast differentiation; mRNA levels for alkaline phosphatase and osteocalcin were suppressed, whereas fibronectin, type I collagen and osteopontin were unaffected. To identify functionally relevant domains of fibronectin, we treated cells with soluble fibronectin fragments and peptides. Cell-binding fibronectin fragments (type III repeats 6-10) containing the Arg-Gly-Asp (RGD) sequence blocked both nodule initiation and maturation, whether or not they contained a functional synergy site. In contrast, addition of the RGD-containing peptide GRGDSPK alone did not inhibit nodule initiation, although it did block nodule maturation. Thus, in addition to the RGD sequence, other features of the large cell-binding fragments contribute to the full osteogenic effects of fibronectin. Nodule formation and osteoblast differentiation resumed after anti-fibronectin antibodies or GRGDSPK peptides were omitted from the media, showing that the inhibition was reversible and the treatments were not cytotoxic. Outside the central cell-binding domain, peptides from the IIICS region and antibodies to the N terminus did not inhibit nodule formation. We conclude that osteoblasts interact with the central cell-binding domain of endogenously produced fibronectin during early stages of differentiation, and that these interactions regulate both normal morphogenesis and gene expression