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#26 Title: Novel Approach for Bone Grafting in the Tibia and Mandible K SRAN (1) (2), C BAHNEY (2), D HU (2), R MARCUCIO (2) (1)UCSF School of Dentistry, (2) Orthopaedic Trauma Institute, San Francisco General Hospital Objectives: The long-term objective of this study is to develop a novel regenerative modality to repair large bone defects. Current grafting technologies available to augment bone healing suffer from poor clinical outcomes including osteonecrosis and/or poor integration. Common to these technologies is a healing mechanism that promotes direct bone formation and this approach could be fundamental in these failures. Alternatively, bone formation can be achieved through a cartilage intermediate (endochondral ossification), which is the normal mechanism by which long bones develop and non-stabilized fractures heal. We hypothesize that promoting endochondral ossification in large defects will stimulate regeneration of a vascularized and integrated bone. This hypothesis was tested in gap defects created in both the tibia and mandible. This comparison is significant because these bones form through different developmental mechanisms: the long bone by endochondral ossification, the mandible by intramembranous ossification. Methods: Using microsurgical techniques, cartilage grafts were isolated from day-7 fracture calli in reporter mice (LacZ+/+ or eGFP) and transplanted into gap defects in the tibia or mandible. Healing was evaluated histologically at 21 or 28 days post-surgery using Safranin O and Trichrome staining to identify bone and cartilage, and LacZ/GFP immunohistochemistry to identify donor versus host cells. Results: Cartilage grafts transplanted into the tibia and mandible transitioned into bone containing large marrow spaces indicative of good vascularization. Good integration was observed between the graft and host tissues. Interestingly, immunohistochemistry staining showed that donor tissue persisted in the bone regenerate suggesting endochondral ossification may not be the mechanism of repair. Conclusion: These data support the hypothesis that cartilage grafts can create a well-vascularized bone regenerate that integrates with host tissue in both the mandible and tibia, suggesting this technique could be a clinically viable therapy for large segmental defects in both the axial and appendicular skeletal systems. Support: American Association of Dental Research (AADR) Student Research Fellowship and The Department of Orofacial Sciences #27 Title: Oral Health Disparities and Dental Care Utilization among California Adolescents T STAVREV (1), L CHUNG (2), M ORELLANA (3) (1) UCSF School of Dentistry, (2) UCSF Department of Preventive and Restorative Dental Sciences, (3) UCSF Department of Orofacial Sciences Objectives: To identify determinants of dental care utilization among adolescents in California with an emphasis on factors related to acculturation variables such as primary language spoken at home, years lived in the U.S., and citizenship status. Methods: This cross-sectional study is a secondary data analysis of the California Health Interview Survey (CHIS), the nation’s largest telephone health survey, with a focus on a subsample of 3,379 adolescents aged 12-17 in California from 2009. To produce population estimates, weights were applied to the sample. Bivariate and multivariable logistic regression analyses were conducted to examine the relationship between sociodemographic variables and dental service use. Jackknife repeated method was used to estimate the sampling variability of the statistics. Multicollinearity among independent variables were examined and the Allen-Cady modified backward selection model was used to fit a more parsimonious model. Pearson’s χ2 test was utilized to test for independence among various categories. Results: Overall, 10% of adolescents did not have a dental visit within the past year. Black adolescents were significantly less likely than white adolescents to have had a prior year dental visit. Additionally, being a non-U.S.-citizen, born to parents who are not married, and not having a health insurance were significantly associated with lack of dental visits. All p-values were less than 0.05. Languages spoken at home and years lived in the U.S. were not a significant predictor of having had a prior year dental visit. Conclusions: Racial and economic disparities related to dental service utilization exist for California adolescents. In addition to these traditional sociodemographic factors, citizenship status remained a strong determinant of utilizing dental care. Focusing intervention efforts on California’s immigrant children could help reduce these oral health disparities and increase access to dental care. Support: UCSF Program in Global Oral Health. #28 Title: Response of human periodontal ligament fibroblasts to Si2+ in vitro A TANG, V VARANASI, P LOOMER UCSF Department of Orofacial Sciences Introduction: Human periodontal ligament fibroblasts (hPDLFs) have several characteristics that enable their osteogenic nature. Osteogenesis of hPDLFs cultures closely mimic that of osteoblasts, and hPDLFs exhibit properties similar to those of osteoblasts such as alkaline phosphatase synthesis and mineralized nodule formation. In addition, hPDLFs are involved in the production, maintenance and/or remodeling of gingiva, periodontal ligament, cementum, and alveolar bone. Thus, stimulation of hPDLFs could result in improved healing of osseous defects surrounding teeth subjected to periodontal disease. Bioactive glasses have been used School of Dentistry Research and Clinical Excellence Day 2011 Program 13
in treating such defects, but the mechanisms are not well understood. Recently, we identified that 45S5 bioglass enhanced collagen type I and osteocalcin expression in hPDLFs. Several ions were identified as being released by the bioglass, with Silicon ion being most prominent. Objectives: The purpose of this study was to determine the effects of silicon ion on hPDLFs, in comparison to whole extracts of 45S5 Bioglass. Methods: Glass conditioned medium (GCM) was prepared by soaking 45S5 glass powders in DMEM for 3 days to make 45S5 ion extracts. Silicon medium was prepared by dissolving sodium metasillicate in DMEM. All media was sterile-filtered and supplemented with 10% FBS, 1% pen-strep, and 1% fungizone. Human periodontal ligament fibroblasts were cultured in either control media, silicon media, or GCM, and the medium was changed every 2 days for up to 16 days. All experiments were carried out in triplicate. At days 2, 4, 8 and 16, cultures were stopped and submitted for gene analysis. At day 16, cultures were also submitted for protein analysis. Results/ Conclusions: The results of this work are currently in progress, and may provide new tools for understanding how silicon ions regulate osteogenesis. Support: American Association of Dental Research (AADR) Student Research Fellowship and The Department of Orofacial Sciences II. GRADUATE CATEGORY #29 Title: Odontoblasts of Immature Rat Molars Lack Expression of TRPV1 J J EMRICK (1) and D J JULIUS (2) (1) UCSF Department of Preventive and Restorative Dental Sciences, (2) Department of Physiology Introduction:Thermal changes in the oral cavity are a common trigger of dental pain (Pashley, 1996). Members of the transient receptor potential (TRP) family of ion channels are responsible for initiating the cellular mechanisms of thermal sensation and nociception. Specifically, TRPV1 is responsible for detecting noxious heat (Caterina et al., 1997), and is functionally expressed in mouse and human odontoblasts (Son et al., 2009; El Karim et al., 2010). Recent evidence in adult rats suggests that TRPV1 expression in odontoblasts may be limited to immature teeth without fused apices (Yeon et al., 2009). Objective: We studied rat odontoblast expression of TRPV1 in molars prior to maturation of the apices using microfluorometry. Methods: Odontoblasts were prepared as previously described in Guo, et al., 1999. Briefly, maxillary and mandibular first and second molars were extracted from 4 week old Sprague-Dawley rats following CO2 euthanasia and cervical dislocation. Apices were visibly open in all molars. Molar crowns were isolated from roots above the level of the cementoenamel junction (CEJ) then fractured. Crown segments and associated pulpal tissue containing odontoblasts were enzymatically digested in collagenase IA and protease I then triturated using a series of Pasteur pipettes. Odontoblasts were plated onto a Matrigel and poly-D-Lysine substrate; loaded with ratiometric calcium indicating dye, Fura-2-acetoxymethyl ester (Fura-2 AM); then subsequently stimulated with selective TRPV1 agonist, capsaicin (20 µM). Cell vitality was confirmed by trypan blue staining. Results:Odontoblasts were identified principally on the basis of phenotype and successful loading with Fura-2 AM. Capsaicin did not elicit a response from odontoblasts. Trypan blue stain confirmed odontoblasts’ vitality. Conclusion:The lack of TRPV1 expression in rat molar odontoblasts is consistent with recent studies (Yeon et al., 2009). The absence of rat odontoblasts’ expression of TRPV1 in mature or immature teeth may represent a key difference from human or mouse odontoblasts. Support: COHORT,T32:DE0073060-16 #30 Title: Acceptability, feasibility and utilization of two automated formats for phone-based oral health education K S HOEFT (1), M J GONZALEZ-VARGAS (1), Z ROMAN (1), C KAVANAGH (1), J MURRAY (1), B HECKMAN (1), D SCHILLINGER (2), M HANDLEY (3), J C BARKER (1), S A GANSKY (1), M M WALSH (1) (1) Center to Address Disparities in Children's Oral Health (CAN DO), UCSF Department of Preventive and Restorative Dental Sciences, (2) Department of Medicine; (3) Department of Epidemiology and Biostatistics Objectives: To assess the acceptability, feasibility and utilization of two automated formats of a phone-based oral health (ECC) education program among a convenience sample of low-income English and Spanish-speaking parents of children aged 1-3 years. Methods: Qualitative interviews ranging 30 to 90 minutes were conducted with parents to assess the acceptability of passive (tollfree number on a brochure) versus proactive (automatically generated call plus brochure) phone education formats. Qualitative data were transcribed and thematically analyzed by trained researchers. Sampling for acceptability, feasibility and utilization data was conducted at two WIC and two community health clinic sites. Quantitative phone call data was collected via the automated phone system and statistical analyses were done with STATA software. Results: Thirty one (17 English, 14 Spanish) qualitative interviews were conducted. Both formats were acceptable to parents of both languages. Thirteen of 56 parents (23%) who agreed to be contacted for the automated phone education answered the call and stayed on the line to hear the information. Spanish-speaking parents had four times the odds of completing such educational calls compared to English-speaking parents (adjusted odds ratio of 4.34 (95% CI: 1.03, 18.3). Only 2 parents called the toll-free number for education. School of Dentistry Research and Clinical Excellence Day 2011 Program 14
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