CAREER: Aging, Tooth Fracture and the Success of Restorative Dentistry

[238237]牙科医生普遍认为，修复和更换失败的修复体消耗了他们大部分的临床活动。牙齿断裂是最有害的失效形式，通常需要完全拔出。修复牙的断裂是目前影响口腔终身健康的主要障碍之一。最近在美国、英国和欧洲报道的研究表明，在45岁及以上有牙齿的成年人中，近50%的牙齿已经修复。因此，尽管在年轻人中蛀牙普遍减少，但在未来十年中，牙齿修复将需要更频繁地进行修复。今天的老年人期望更长寿、更健康的生活，大多数人希望在这段时间内拥有一个功能和美观可接受的牙齿。提出的研究的一般假设是，修复的牙齿骨折是由牙本质的机械性能的变化随着年龄的增长而促进的。牙本质是一种水化、矿化的硬组织，占牙齿体积的大部分。研究活动旨在表征牙本质的力学行为，并利用混合方法将其抗断裂性与年龄联系起来。初步研究表明，牙本质的断裂韧性随组织年龄的增长而降低。为了确定年龄对牙齿断裂的意义，我们将提取的第三磨牙牙本质按3个年龄组制备双悬臂梁标本。单调楔形载荷将用于启动和维持稳定的裂纹扩展，同时使用云纹干涉测量法监测平面内位移作为裂纹长度的函数。实验得到的全场位移将作为断裂过程有限元模型的基准解。采用逆分析方法，可以精确地从数值模型中得到断裂力学及其对能量耗散的贡献。这些活动将与断裂表面的微观分析相辅相成，以确定和量化老化对牙本质断裂机制的影响。这些研究活动与一项教育计划相结合，该计划扩大了马里兰大学巴尔的摩县分校（UMBC）中学生新拓展项目的影响。希望进一步探索科学兴趣的学生将继续作为研究学者，在为期6周的暑期课程中，在PI的实验室从事生物医学研究。教育目标是增加马里兰学校中未被充分代表的少数民族在牙科和工程方面的参与，并通过组织研究学者及其导师到巴尔的摩学校七年级和八年级教室的访问来促进口腔健康和科学。该教育项目由UMBC，马里兰大学牙科学院和Meyerhoff学者计划之间的合作伙伴关系支持。机械工程专业的本科生和研究生以及牙科专业的学生将共同指导研究学者进行研究。Meyerhoff项目将提供专业发展活动，并通过本科系列研讨会向年轻学者介绍其他部门的生物医学研究。

0238237ArolaDentists generally accept that the revision and replacement of failed restorations consumes the majority of their clinical activities. Tooth fracture is the most detrimental form of failure and often requires complete extraction. The fracture of restored teeth is currently one of the primary obstacles to lifelong oral health. Recent studies reported in the US, UK and Europe indicate that nearly 50% of the teeth in dentate adults aged 45 years and over have been restored. Therefore, in spite of a general decrease in tooth decay among the young, dental restorations will be required and necessitate repair more often over the next ten years. Older people today expect longer, healthier lives and most wish for a functional and aesthetically acceptable dentition over this period.The general hypothesis of the proposed investigation is that restored tooth fractures are fostered by a change in the mechanical properties of dentin with aging. Dentin is a hydrated, mineralized hard tissue that comprises the majority of the tooth by volume. Research activities are aimed at characterizing the mechanical behavior of dentin and correlating its fracture resistance with age utilizing a hybrid approach. Based on preliminary studies, the fracture toughness of dentin is expected to decrease with age of the tissue. To establish the significance of aging on tooth fracture, double cantilever beam specimens will be prepared from the dentin of extracted third molars according to 3 age groups. Monotonic wedge loads will be used to initiate and sustain stable crack growth while the in-plane displacements are monitored as a function of crack length using moire interferometry. Full-field displacements from experiments will be used as the benchmark solution for finite element models of the fracture process. Using an inverse analysis the mechanics of fracture and their contribution to energy dissipation will be obtained precisely from the numerical models. These activities will be complemented with a microscopic analysis of the fracture surfaces to both identify and quantify the influence of aging on the mechanisms of fracture in dentin. The research activities are integrated with an educational plan that extends the impact of a new outreach program for middle school students at the University of Maryland Baltimore County(UMBC). Students who wish to further explore their interests in science will continue as Research Scholars and engage in biomedical research within the PI's laboratory during a 6-week summer program. The educational objectives are to increase participation of underrepresented minorities from Maryland's schools in dentistry and engineering, and promote oral health and science through organized visits from the Research Scholars and their mentors to 7th and 8th grade classrooms in Baltimore's schools. The educational program is supported by a partnership between UMBC, the University of Maryland Dental School and the Meyerhoff Scholars Program. Undergraduate and graduate students in Mechanical Engineering and students from Dentistry will jointly mentor the Research Scholars with their investigations. The Meyerhoff Program will provide professional development activities and introduce the young Scholars to biomedical research in other departments through an undergraduate seminar series.