MECHANICAL CHARACTERIZATION OF THE HARD PALATE By JENNIFER LANE HOTZMAN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010 1 © 2010 Jennifer Lane Hotzman 2 To my family and friends 3 ACKNOWLEDGMENTS Many individuals have contributed to the success of my dissertation. First, I would like to thank my advisor, Dr. David Daegling, for all of his assistance throughout this entire experience. I would have never been able to complete this undertaking without all of his patience and guidance. I would also like to thank my parents who were unfailing in their support of my dream to accomplish this goal. I give general thanks to Kaki York and Chris Ward who helped answer questions regarding statistics throughout the entire process. There are also specific individuals and organizations I would like to thank for providing help with particular portions of my project. Dr. Gerald Bourne assited with granting access to both the nanoindenter and microindenter. The nanoindentater is in the Major Analytical Instrumentation Center, Department of Materials Science and Engineering, University of Florida. I would like to thank Dr. Andrew Rapoff for providing guidance on how to best prepare the specimens for indentation. Laurel Freas assisted with the initial sawing of the palate that was completed in order to prepare the specimens for indentation. SCANCO USA, Inc. conducted the micro-computed tomography scanning of the macaque skull. I would like to thank Dr. Rasheesh Kapadia for coordinating the scanning and providing the data to me. I would also like to thank Casey Self for packaging the specimen and shipping it to the company to be scanned. I would like to thank Eileen Westwig at the American Museum of Natural History and Linda Gordon at the Smithsonian National Museum of Natural History for coordinating my visits and allowing me access the museum collections to gather my comparative data. I also wish to thank Laura Regan for providing me room and board when I collected my data at the Smithsonian Museum. 4 The wood block experiment also required some assistance during the preparation phase. I would like to thank Andy Thon and Anna Vick for helping me to procure the wood necessary for the experiment as well as the tools. Traci van Deest also helped preparing the wood block by assisting with sawing it to the correct dimensions. Finally, I would like to thank Chris Ayers for his computer support and more importantly his moral support. Without his help, this project would have been even more difficult to accomplish. I want to extend my gratitude to all of the individuals who helped me to complete my project. 5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES...........................................................................................................................7 LIST OF FIGURES .........................................................................................................................9 CHAPTER 1 PROBLEM INTRODUCTION..............................................................................................17 Research Statement.................................................................................................................17 Hypotheses..............................................................................................................................18 2 BACKGROUND INFORMATION.......................................................................................22 Mechanics in Bone Growth ....................................................................................................22 Palatal Growth ........................................................................................................................33 Sutures ....................................................................................................................................38 Structure and Function of the Periodontal Ligament..............................................................45 Biomechanics of Mastication .................................................................................................47 3 METHODS.............................................................................................................................61 4 RESULTS...............................................................................................................................91 5 DISCUSSION.......................................................................................................................250 Comparing the Material Properties of the Maxillae and Mandible ......................................250 Modeling the Palate ..............................................................................................................259 Sutural Complexity and Loading..........................................................................................266 Allometry of the Palate.........................................................................................................271 Implications of Research for Understanding the Functional Morphology of the Skull .......275 Unresolved Questions...........................................................................................................277 6 CONCLUSIONS ..................................................................................................................287 LIST OF REFERENCES.............................................................................................................292 BIOGRAPHICAL SKETCH .......................................................................................................303 6 LIST OF TABLES Table page 3-1 Samples sizes for comparative study .................................................................................83 3-2 Definitions of measurements collected..............................................................................84 4-1 Descriptive statistics for elastic moduli (GPa) values from the nanoindentation section. .............................................................................................................................130 4-2 Elastic moduli values from section 1 calculated from microindentation.........................137 4-3 Elastic moduli values from section 2 calculated from microindentation.........................138 4-4 Elastic moduli values from section 3 calculated from microindentation.........................139 4-5 Elastic moduli values from section 4 calculated from microindentation.........................140 4-6 Elastic moduli values from section 5 calculated from microindentation.........................141 4-7 Elastic moduli values from section 6 calculated from microindentation.........................142 4-8 Elastic moduli values from section 7 calculated from microindentation.........................143 4-9 Maximum strain at different gage locations in the pigs...................................................146 4-10 Position 1 predictions and observed strain.......................................................................150 4-11 Position 2 predictions and observed strain.......................................................................150 4-12 Position 3 predictions and observed strain.......................................................................150 4-13 Predicted stress and strain values from hand calculated moment of inertia ....................151 4-14 Expected versus observed strain ratios during macaque bending....................................152 4-15 Shear and principal strain ratios for pig specimens in torsion.........................................152 4-16 Position 1 shear predictions for the macaque cranium during twisting...........................158 4-17 Position 2 shear predictions for the macaque cranium during twisting...........................158 4-18 Shear strains and principal strain ratios for the macaque during twisting .......................158 4-19 Reduced major axis results for papionins. .......................................................................162 4-20 Reduced major axis results for colobines. .......................................................................164 7 4-21 Reduced major axis results for hominoids.......................................................................166 4-22 Significance (alpha) values for phylogenetic group comparisons from RMA2*. ...........168 4-23 Ratio averages for palatal dimensions versus size...........................................................169 4-24 Descriptive statistics of fractal dimensions for species by sex........................................237 4-25 Descriptive statistics of suture length ratio for species by sex ........................................238 4-26 Mann-Whitney U P values for the sexes of each species ................................................239 4-27 Mann-Whitney U tests significance values for species versus fractal dimension (FD) ..240 4-28 Mann-Whitney U tests significance values for species versus suture length ratio..........243 4-29 Mann-Whitney U tests significance values for phylogenetic groups versus suture measurement ....................................................................................................................246 4-30 Mann-Whitney U tests significance values for dietary contrasts.....................................246