R Seyedmahmoud1, Y Wang2,3, G Thiagarajan1,4, J P Gorski1,5, R Reed Edwards1, J D McGuire1, M P Walker6,7. 1. Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. 2. Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. wangyo@umkc.edu. 3. Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. wangyo@umkc.edu. 4. Department of Civil and Mechanical Engineering, School of Computing and Engineering, University of Missouri-Kansas City, Kansas City, MO, USA. 5. Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. 6. Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. walkermp@umkc.edu. 7. Center of Excellence in Musculoskeletal and Dental Tissues, University of Missouri-Kansas City, 650 East 25th St, Kansas City, MO, 64108, USA. walkermp@umkc.edu.
Abstract
OBJECTIVES: The aim of this study is to determine the effects of in vitro and in vivo high-dose radiotherapy on microhardness and associated indentation pattern morphology of enamel. MATERIALS AND METHODS: The inner, middle, and outer microhardness of enamel was evaluated using three experimental groups: control (non-radiated); in vitro irradiated; in vivo irradiated. In vitro specimens were exposed to simulated radiotherapy, and in vivo specimens were extracted teeth from oral cancer patients previously treated with radiotherapy. Indentations were measured via SEM images to calculate microhardness values and to assess the mechanomorphological properties of enamel before and after radiotherapy. RESULTS: Middle and outer regions of enamel demonstrated a significant decrease in microhardness after in vitro and in vivo irradiation compared to the control group (p < 0.05). Two indentation patterns were observed: pattern A-presence of microcracks around indent periphery, which represents local dissipation of deformation energy; pattern B-clean, sharp indents. The percentage of clean microindentation patterns, compared to controls, was significantly higher following in vitro and in vivo irradiation in all enamel regions. The highest percentage of clean microindentations (65%) was observed in the in vivo irradiated group in the inner region of enamel near the dentin-enamel junction. CONCLUSIONS: For the first time, this study shows that in vitro and in vivo irradiation alters enamel microhardness. Likewise, the indentation pattern differences suggest that enamel may become more brittle following in vitro and in vivo irradiation. CLINICAL RELEVANCE: The mechanomorphological property changes of enamel following radiation may be a contributory component of pathologic enamel delamination following oral cancer radiotherapy.
OBJECTIVES: The aim of this study is to determine the effects of in vitro and in vivo high-dose radiotherapy on microhardness and associated indentation pattern morphology of enamel. MATERIALS AND METHODS: The inner, middle, and outer microhardness of enamel was evaluated using three experimental groups: control (non-radiated); in vitro irradiated; in vivo irradiated. In vitro specimens were exposed to simulated radiotherapy, and in vivo specimens were extracted teeth from oral cancerpatients previously treated with radiotherapy. Indentations were measured via SEM images to calculate microhardness values and to assess the mechanomorphological properties of enamel before and after radiotherapy. RESULTS: Middle and outer regions of enamel demonstrated a significant decrease in microhardness after in vitro and in vivo irradiation compared to the control group (p < 0.05). Two indentation patterns were observed: pattern A-presence of microcracks around indent periphery, which represents local dissipation of deformation energy; pattern B-clean, sharp indents. The percentage of clean microindentation patterns, compared to controls, was significantly higher following in vitro and in vivo irradiation in all enamel regions. The highest percentage of clean microindentations (65%) was observed in the in vivo irradiated group in the inner region of enamel near the dentin-enamel junction. CONCLUSIONS: For the first time, this study shows that in vitro and in vivo irradiation alters enamel microhardness. Likewise, the indentation pattern differences suggest that enamel may become more brittle following in vitro and in vivo irradiation. CLINICAL RELEVANCE: The mechanomorphological property changes of enamel following radiation may be a contributory component of pathologic enamel delamination following oral cancer radiotherapy.
Authors: Talitha de Siqueira Mellara; Regina Guenka Palma-Dibb; Harley Francisco de Oliveira; Francisco Wanderley Garcia Paula-Silva; Paulo Nelson-Filho; Raquel Assed Bezerra da Silva; Léa Assed Bezerra da Silva; Alexandra Mussolino de Queiroz Journal: Radiat Oncol Date: 2014-01-22 Impact factor: 3.481