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lesion depth of 100µm. Lesions were completely dehydrated and stored prior to use. Next, specimens were immersed into a pH 7.4 metastable remineralization solution of 8mM CaCl2 and 5mM KH2PO4 with the constant composition system titrating two separate pH 7.4 solutions of 8mM CaCl2 and 5mM KH2PO4 at a constant rate into the reaction vessel containing the dentin samples. This was either done for 7 days or 14 days. Samples were later embedded into epoxy, sectioned perpendicular to the exposed surface, air dried, polished down to 0.25µm, ground down to a thickness of 100µm and analyzed by polarized light microscopy (PLM). Nanoindentation was used to test the mechanical properties of the remineralized lesions. Results: Lesion depth: Control averages are 109.5±10.3µm, 7 days averages are 77.0±5.8µm, 14 days averages are 82.4±8.2µm. Conclusions: The constant composition titration system increases the nucleation lag time thereby allowing demineralized dentin more time to nucleate and potentially more time to nucleate within the intrafibrillar (within collagen fibrils) dentin so that more mechanical properties are regained. Support: UCSF Department of Preventive and Restorative Dental Sciences and by NIH-grants R01 DE16849 and R01-017529 #11 Title: Discontinuities in human alveorlar bone J M HURNG (1), M P KURYLO (1), J D LIN (1), J A HAYTER (2), S M WEBB (2), P A PIANETTA (2), S P HO (1) (1) UCSF Department of Preventive and Restorative Dental Sciences, Division of Biomaterials and Bioengineering (2) Stanford Synchrotron Radiation Lightsource, SLAC, Menlo Park, CA Objective: This study highlights discontinuities in alveolar bone (AB) of human bone-tooth fibrous joints. Results indicate “quality” of AB could be redefined and would affect mechanobiology at the periodontal ligament (PDL)-bone and PDL-cementum entheses of the fibrous joint. Methods: X-ray attenuation and elemental spatial variations on 1-2µm sections from AB were identified using transmission X-ray microscopy (TXM, 5.4 keV) and microprobe X-ray fluorescence imaging (µ-XRF, 12 keV). Fibromodulin (FMOD) and biglycan (BGN) were identified using immunohistochemistry. Mechanical resistance of various regions in AB were investigated using nanoindentation technique. Results: Two types of bones marked by differences in X-ray attenuation, calcium (Ca), phosphorus (P), and zinc (Zn) were identified in AB. Bone with radial fibers (RFB) was identified as a higher X-ray attenuating material and µ-XRF measurements yielded higher counts of Ca, P, and Zn. Higher X-ray attenuating bands were observed in inter-lamellae regions of lamellar bone (LB) with a presence of FMOD, and entheses demonstrated presence of BGN. AFM wet scans illustrated hygroscopic lamellae relative to inter-lamellae. Radial PDL fibers in RFB, changed their orientation into circumferential in LB within a junction of 10-30 µm. Hygroscopicity but higher X-ray attenuation was observed at this junction. Steep modulus gradients representing discontinuities were observed between RFB and LB. Physico-chemical heterogeneity were further complemented by elastic modulus values of 23.9 ± 2.8 GPa for lamellae, 33.2 ± 0.4 GPa for inter-lamellae, with signif icant modulus differences between lamellae and interlamellae confirmed via Student's t-test (P< 0.05), and 2-8 GPa for RFB. Conclusions: Higher packing density and differential collagen fiber orientation, not necessarily mineral changes, within RFB, LB and the junction could contribute to a higher attenuation. The discontinuity in modulus profile between RFB and LB could compromise the “quality” of alveolar bone and could impair joint biomechanics. Support: NIH-NIDCR R00DE018212-03, NIH-NIBIB 5R01EB004321, and DOE-BES #12 Title: Calcium Phosphate Growth on Amelogenin Nanoribbons P ISHANI AFOUSI, O MARTINEZ-AVILA, S HABELITZ UCSF Department of Preventive and Restorative Dental Sciences Introduction: Amelogenin protein is critical for enamel formation as it constitutes the main component of the developing enamel matrix. The full-length Amelogenin, rH174 can, not only self-assemble into nanospheres, but also into more complex structures known as nanoribbons. Objectives: The objective of this study was to show that amelogenin nanoribbons can act as templates for calcium phosphate mineralization. Methods: Amelogenin nanoribbons were prepared from oil-water emulsions, and initially imaged using atomic force microscopy (AFM) to establish a control and then incubated in various [Ca/P] with saturation degree of 11, pH of 7.4, and 37˚C, with and without Fluoride of 0.002ppm. The samples were imaged using AFM after 24hr and 72hr incubation times. While no significant differences in width and length between pre and post-incubation time of amelogenin nanoribbons were observed, the height of amelogenin nanoribbons increased from an average of 4.7nm to 7.23nm after 72hrs of incubation; with no significant difference in heights between 24hr and 72hr incubation times. Also there was no difference between samples that were pre-treated with fluoride and those that were treated with saturated calcium phosphate solutions only. Results: The results of the study support the conclusion that amelogenin nanoribbons can provide a suitable backbone for calcium phosphate deposition and growth. Support: UCSF Department of Preventive and Restorative Dental Sciences School of Dentistry Research and Clinical Excellence Day 2011 Program 7
#13 Title: Effect of Xylitol-Wipe Use on Genotype Profile and Biofilm Formation of Mutans Streptococci I MARKOVA , N HOANG, C LE, J D B FEATHERSTONE, L ZHAN UCSF Department of Preventive and Restorative Dental Sciences, Department of Orofacial Sciences Purpose: To evaluate the prolonged impact of daily use of xylitol-wipes on genotype profile and biofilm formation of Mutants streptococci (MS) in high-risk infants. Methods: In a double-blind randomized controlled clinical trial, 44 mothers with active caries and their infants aged 6-35 months were recruited (N=22 each group). The infants were randomized into the xylitol-wipe or placebo-wipe groups. Guardians were instructed to use wipes on their infants 3-4 times daily in addition to daily tooth brushing for one year. Children were followed up at 2 year (1 year after completion of the wipe use). Saliva samples were collected and 10 MS colonies were isolated from each child. Fermentation tests were performed for each MS isolate for Phenotyping. Arbitrary primed-PCR technique was used to identify MS genotypes and transmission patterns and compared with the MS isolates from children at baseline and 1 year at the completion of wipe use to access the genotype stability. Sucrose dependent biofilm formation ability of MS genotype was measured. Results: Twenty children (11 in xylitol-wipe group and 9 in placebo-wipe group) returned for the 2-year follow-up visit with14 subjects having MS infection. One hundred twenty MS isolates were isolated from 12 subjects and all identified as S. mutans by fermentation test. Fifteen genotypes from xylitol-wipe group and 10 genotypes from placebo wipe group were identified by AP-PCR. More than 75% of MS genotypes isolated at 2 year were new colonizers compared to MS genotypes isolated at baseline and one year. There is no statistical significant difference in biofilm formation ability between the two wipe groups (P>0.7, t test). Conclusion: Only less than 50% of subjects participated in the extended follow-up study. MS colonization in both groups showed high variability with new colonizers. No prolonged effect of xylitol-wipe use was seen in biofilm formation ability of MS. Support: This project was supported by NIH/NCRR/OD UCSF-CTSI Grant Number TL1 RR024129. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH. #14 Title: Monitoring natural occlusal lesions with a new rapid-sanning Cross-Polarization Optical Coherence Tomography L H MAUNG, H KANG, C L DARLING, M STANINEC, D FRIED UCSF Department of Preventive and Restorative Dental Sciences Background and Objective : Our lab has demonstrated that cross-polarization sensitive optical coherence (CP-OCT) can be used to nondestructively measure the severity of demineralization in the occlusal surfaces. Occlusal lesions typically do not appear on conventional x-ray radiographs until they have progressed well beyond the dentin, at which point, it is often too late for the conservative intervention. Clinicians rely mostly on the visual inspection and the dental explorer. However, such methods suffer from poor sensitivity. In this research, a novel cross polarization optical coherence tomography system (CP-OCT) with a microelectromechanical system(MEMS) based scanner will be used to image the occlusal lesions. The purpose of this research is to evaluate the performance of the new rapid scanning CP-OCT system to image occlusal caries. Materials and Methods: Teeth with suspected occlusal caries (n=15) will be selected. Cross- Polarization Optical Coherence Tomography (CP-OCT) will be used to scan the occlusal surface of each tooth. The software is developed to quantify the severity and depth of the naturally occurring occlusal lesion, and images of the scans will be mapped topographically. After scanning with CP-OCT, the sample teeth will be sectioned and analyzed with Polarized Light Microscopy (PLM), and Microradiograph (TMR). The performance of this new CP-OCT will be compared with the histological results. Support: This research is supported by NIDCR RO1 14698 & NIDCR RO1 17869 #15 Title: Incidence of Upper Cervical Vertebrae Anomalies in Individuals with Craniofacial Anomalies Using CBCT B MAXFIELD, S DOUGLAS, S OBEROI UCSF Department of Orofacial Sciences Objective: To develop a method to identify upper cervical vertebrae anomalies (CVA) in individuals with non-syndromic cleft lip and palate (CLP) and hemifacial microsomia (HFM), and to compare the prevalence and type of CVA with control individuals. Materials and Methods: Retrospective cross-sectional study on a sample of 48 cone beam computed tomography (CBCT) scans of 38 individuals with CLP and 10 with HFM from the UCSF Center for Craniofacial Anomalies and 45 CBCT scans of control subjects from the UCSF division of Orthodontics. CBCT scans were interpreted using Anatomage software ( InVivo 3.0, San Jose, California, USA) by two concurrently viewing examiners. The scans were analyzed using the volume rendering tool allowing the examiners to isolate the vertebrae and visualize all captured vertebrae in three-dimensions from all directions. Scans were also interpreted in a step-wise manner through the slices in the sagittal, coronal, and axial view. All analysis was done to register and categorize anomalies into posterior arch deficiencies, fusion, and the association of both. Results: In the cleft group, 13.16% had CVA and the HFM group, 10% were found to have CVA. In the control sample, 9.76% showed anomalies of the cervical spine. This difference was statistically significant. Reliability was verified by analyzing 5 CLP and 5 control scans randomly selected to confirm equal results. Conclusions: CBCT scans interpreted with Anatomage software tool are useful in diagnosing CVA. Although CVA are common in craniofacial anomalies, even in cleft lip and palate, there is a relative high prevalence in normal controls as well. School of Dentistry Research and Clinical Excellence Day 2011 Program 8
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