Crack Propagation in Teeth: A Comparison of Perimortem and Postmortem Behavior of Dental Materials and Cracks*

Abstract: This study presents a new method for understanding postmortem heat-induced crack propagation patterns in teeth. The results demonstrate that patterns of postmortem heat-induced crack propagation differ from perimortem and antemortem trauma-induced crack propagation patterns. Dental material of the postmortem tooth undergoes dehydration leading to a shrinking and more brittle dentin material and a weaker dentin-enamel junction. Dentin intertubule tensile stresses are amplified by the presence of the pulp cavity, and initiates crack propagation from the internal dentin, through the dentin-enamel junction and lastly the enamel. In contrast, in vivo perimortem and antemortem trauma-induced crack propagation initiates cracking from the external surface of the enamel toward the dentin-enamel junction where the majority of the energy of the crack is dissipated, eliminating the crack’s progress into the dentin. These unique patterns of crack propagation can be used to differentiate postmortem taphonomy-induced damage from antemortem and perimortem trauma in teeth.     

African American and White Adolescents' Strategies for Managing Cultural Diversity in Predominantly White High Schools

This study examined 3 strategies that African American and White participants (9th–12th grade) used to manage cultural diversity: multicultural, separation, and assimilation/acculturation strategies. Older African American adolescents endorsed multicultural strategies (integration/fusion and alternation) more strongly and separation less strongly than their younger African American peers. The reverse pattern was found for White adolescents. With respect to peer relations, separation and multicultural strategies were associated with cross-ethnic peer relations for both African American and White respondents. For African American adolescents, multicultural strategy endorsement was positively related to ethnic identity; particularly for older compared with younger African American adolescents, assimilation/acculturation was a strategy associated with a less strongly positive sense of ethnic identity. The results are discussed in relation to forces supporting adolescents' strategy development, and the implications of strategy usage for adjustment in predominantly White schools.     

On the evaluation of procedural systems in laboratory experiments

Conclusion This article has criticized various aspects of the Thibaut and Walker research. Thibaut and Walker have greatly contributed to the study of procedural justice by conceptually isolating issues and suggesting ways they can be empirically studied. Our criticisms in Section I point out weaknesses in the design of particular experiments but do not question the appropriateness of laboratory research on the operating characteristics of procedural systems. In this realm, Thibaut and Walker's work will provide the starting point for future research.We do question the appropriateness of laboratory research for answering subjective questions, as outlined in Section III. While we agree that experimental research can indicate how people feel about a system, we do not think that objective measurement of the incidence of such subjective feelings tells us anything about the objective qualities of the systems considered. The assertion that one system is superior to another because some people feel it is so goes beyond the limitations of the experiments and the data. This type of overgeneralization is seriously misleading when it is used to support policy recommendations, particularly when other factors, such as the costs we discuss in Section II, are not considered.We wish to thank Dr. Jacqueline Macaulay, Professor Stewart Macaulay, and Dr. Neil Vidmar for their comments on an earlier draft of this article. Responsibility for its contents rests solely with us.