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Item The effects of salivas on occlusal forces(Wiley, 2015-05) McCrea, Emily S.; Katona, Thomas R.; Eckert, George J.; Department of Orthodontics and Oral Facial Genetics, IU School of DentistryContacting surfaces of opposing teeth produce friction that, when altered, changes the contact force direction and/or magnitude. As friction can be influenced by several factors, including lubrication and the contacting materials, the aim of this study was to measure the occlusal load alterations experienced by teeth with the introduction of different salivas and dental restorative materials. Pairs of molar teeth were set into occlusion with a weighted maxillary tooth mounted onto a vertical sliding assembly and the mandibular tooth supported by a load cell. The load components on the mandibular tooth were measured with three opposing pairs of dental restorative materials (plastic denture, all-ceramic and stainless steel), four (human and three artificial) salivas and 16 occlusal configurations. All lateral force component measurements were significantly different (P < 0·0001) from the dry (control) surface regardless of the crown material or occlusal configuration, while the effects of the artificial salivas compared to each other and to human saliva depended on the crown material.Item The roles of wedging and friction in the mechanics of dental occlusal contacts(2019-04) Katona, Thomas R.; Eckert, George J.Objective: The primary aim of this project is to elucidate the basic mechanical engineering principles that govern and explain unexpected and counter-intuitive occlusal contact force measurements. Methods: Forces were measured on matched pairs of first molar denture, ceramic and stainless steel crowns during occlusion and disclusion, with human saliva and dry (control). The weighted maxillary assembly, guided by a precision slide, was lowered onto, and raised from, the mandibular crown. The forces experienced by the mandibular tooth were continuously measured by the load cell that supported it. Statistical analyses included LOESS smoothing splines and generalized additive models. Principles of basic statics and classic friction were applied to explain and validate the results. Results: It was determined that within the span of a single chomp, the in-occlusal plane force component (Flateral) on the tooth is highly variable in direction and/or magnitude. The most salient observations were that Flateral was higher in disclusion than in occlusion, and the largest Flateral did not necessarily occur when the bite force was maximum. Furthermore, saliva significantly affected the results. Conclusions: The results demonstrated that contacting teeth experience complex transient mechanical environments that can be readily explained with elementary engineering principles involving wedging and friction at the occlusal contacts.