FORM DIFFERENCE COMPUTATIONS IN RESTORATIVE DENTISTRY

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DESCRIPTION (Adapted from investigator's Abstract): Form (size and shape) comparisons between objects are important in; 1) restorative dentistry with respect to fit, wear, occlusion, stress/strain distribution, quality control and design analysis; 2) growth and development sciences; 3) the diagnosis, treatment planning, and prognosis of many clinical problems; and 4) physical anthropology. If the form comparison between two objects is adequately described, the underlying cause of form difference could be determined. Such causal information in restorative dentistry would then suggest; 1) different materials processing techniques, 2) the use of materials with different properties, and/or 3) design alterations leading to increased clinical performance. Strain based tensorial morphometric comparison techniques will be used since, unlike traditional scalar methods, principal strains and the parameters obtained from them 1) provide both magnitude and direction of form change, 2) can be determined at any point on or in the structure, 3) size and shape change can be segregated, and 4) are coordinate system independent. The major hypothesis present is that tensorial morphometric methods can be constructed which eliminate many, if not all, finite element scaling analysis limitations without compromising any of the advantages. The limitation of artificial subdivision is addressed by the macroelement method while the requirement of homologous landmarks is addressed by the nonlandmark method. There are four minor hypotheses: 1) these morphometric methods provide stable accurate solutions in numerical simulations; 2) these methods provide additional clinically useful difference information not obtainable from other techniques, and can be objectively assessed in a number of significant experimental systems including i) duplication accuracy in stone, ii) casting accuracy, and iii) eye growth processes; 3) these methods provide results which compare well to established techniques such as finite element scaling analysis, Euclidean distance matrix analysis, and percentage change in dimension; and 4) these methods provide a more complete description of form change than that of other techniques. The results, along with the techniques themselves, could increase accuracy and therefore fit, occlusion, and the clinical life of any restoration which requires duplication of oral structures and/or casting. The eye growth study could lead to insights into the processes involved and their effect on shape. The significance of the techniques would go beyond this study since; 1) the nonlandmark method could be used to analyze most biological and prosthetic structures which have previously eluded such tensorial study due to the paucity of landmarks, 2) the macroelement method could be used in structures which have a number of landmarks, such as the craniofacial complex, and 3) these form difference methods would make optimal use of the new boundary coordinate assessment techniques.