Methods: We used whole mount in situ hybridization to collect genetic expression pattern data and CT scanning to collect morphological data from embryonic T. scripta heads. Results: T. scripta embryos were found to express Pitx2, Pax9, Barx1, and Fgf8 in the presumptive odontogenic region in patterns comparable to those found in the mouse and chick. Msx1 and Msx2 expression was also detected but was limited proximally during Yntema stage 14 (Y14), similar to previously reported results in Hamburger-Hamilton stage 27 (HH27) chicks. We postulate that the evolutionary origins for tooth loss in turtles may be linked to a loss <strong>of</strong> BMP4 signaling in the proximal epithelium, potentially representing a form <strong>of</strong> parallelism with the clade Aves. Additionally, Shh-expressing epithelial thickenings were found in the palatal region <strong>of</strong> some Y17 T. scripta specimens. The fossil record <strong>of</strong> palatal teeth in Testudinata leads us to hypothesize that the thickenings could be tooth rudiments, and adds complexity to question <strong>of</strong> the molecular origins <strong>of</strong> tooth loss in the turtle lineage. Support: NSF grant BSC-0616308 and REU supplement. #56 Title: Local response <strong>of</strong> reduced functional loads in dentoalveolar complex <strong>of</strong> vertebrates N LEONG (1), S DJOMEHRI (1), P CHUANG (1), D CURTIS (1), M RYDER (2), S P HO (1) (1) Division <strong>of</strong> Biomaterials & Bioengineering, Department <strong>of</strong> Preventive and Restorative Dental Sciences, <strong>UCSF</strong> <strong>School</strong> <strong>of</strong> <strong>Dentistry</strong>, (2) Department <strong>of</strong> Or<strong>of</strong>acial Sciences Division <strong>of</strong> Periodontology, <strong>UCSF</strong> <strong>School</strong> <strong>of</strong> <strong>Dentistry</strong> Objective: Previous investigations using reduced functional loads illustrated significant changes in root-bone morphology, mechanical hardness <strong>of</strong> alveolar bone (AB) and secondary cementum (SC), and gradual increases in mineral at mechanically strained entheses <strong>of</strong> bone-PDL and cementum-PDL. Our purpose was to correlate biophysical and biochemical properties <strong>of</strong> load bearing PDL, bone, and cementum in response to decreased loads over time. Methods: Methods include spatiotemporal mapping <strong>of</strong> biochemical properties <strong>of</strong> the molar-bone complex in 6, 8, 12, and 15 week (N=4) rats fed hard (stiffness 127-158N/mm) and s<strong>of</strong>t (stiffness 0.3-0.5N/mm) diets. Sections were evaluated for tartrate resistant acid phosphatase (TRAP) positive cells indicating clastic activity and MicroXCT virtual sections for corresponding morphological changes in bone and PDL-width. Results: AGE(Weeks) 6 8 12 15 PDL-Width(µms): Distal Mesial Distal Mesial Distal Mesial Distal Mesial Hard 136+20 118+20 129+21 148+4 139+34 139+29 146+15 135+21 S<strong>of</strong>t - - 148+39 126+19 126+40 126+15 118+28 117+16 Bone CEJ-ABC(µms): Hard 167+33 262+43 275+147 375+127 181+0 255+0 285+131 511+265 S<strong>of</strong>t - - 218+160 307+123 245+57 285+53 182+85 278+79 Osteoclast Count Hard 13+3 12+3 13+2 8+3 12+3 7+2 6+1 8+2 S<strong>of</strong>t - - 10+2 9+2 13+2 9+1 13+2 11+3 Conclusion: In this study biophysical and biochemical markers were measured to better understand the effects <strong>of</strong> functional loads on the biomechanics <strong>of</strong> the bone-tooth fibrous joint. Prolonged reduced functional loads illustrated: i) increased osteoclastic activity; ii) decreased alveolar bone recession (increased hyper-eruption); iii) significantly decreased (Students’ t-test P < 0.05) PDL-width. Tissue adaptation can be correlated to the local biochemical activity governing a functional dentoalveolar complex; however investigations beyond the discussed time points are necessary. A better understanding <strong>of</strong> the mechanisms, interaction and clinical significance <strong>of</strong> adaptive events will require additional markers such as RANKL, OPG, OCN, E11, fibrogenic and osteogenic proteoglycans. Support: NIH/NIDCR-R00DE018212, <strong>UCSF</strong> Department <strong>of</strong> Preventive and Restorative Dental Sciences and Department <strong>of</strong> Or<strong>of</strong>acial Sciences, #58 Title: Bond Strength and Visual Morphological Structure <strong>of</strong> Three Glass Ionomer Cements M LOW, L PINZON, M GOEL, D TANG <strong>UCSF</strong> Department <strong>of</strong> Preventive and Restorative Dental Sciences Purpose: To evaluate dentin-glass ionomer bond strength after 24 hours and 3 months storage time and to analyze the morphology <strong>of</strong> the three glass ionomer cements (GICs): Fuji IX, Ketac Molar Quick Aplicap, and Fuji under AFM Methods: Human third molars were sectioned sagittally in a bucco-lingual direction in the proximal location and polished with 320grit SiC discs. Composite stubs (5mm height/19.6 mm2 area) (Gradia/GC America) were air abraded with Al2O3 particles, ultrasonically cleaned, and bonded to the dentin specimens with the cements according to the manufacturers’ instructions. Specimens were stored in water at 37°C for 24 hours and 3 months and were de-bonded under shear load with a universal testing machine (Instron/1122) at a cross-head speed <strong>of</strong> 5 mm/min. Failure modes were determined using 100X magnification Data was <strong>School</strong> <strong>of</strong> <strong>Dentistry</strong> Research and Clinical Excellence Day 2011 Program 25
analyzed using ANOVA with Fisher’s PLSD intervals (p
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