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During eating, the teeth usually endure the sharply temperature changes because of different foods. It is of importance to investigate the heat transfer and heat dissipation behavior of the dentino–enamel junction (DEJ) of human tooth since dentine and enamel have different thermophysical properties. The spatial and temporal temperature distributions on the enamel, dentine, and pulpal chamber of both the human tooth and its discontinuous boundaries, were measured using infrared thermography using a stepped temperature increase on the outer boundary of enamel crowns. The thermal diffusivities for enamel and dentine were deduced from the time dependent temperature change at the enamel and dentine layers. The thermal conductivities for enamel and dentine were calculated to be 0.81 Wm-1K-1 and 0.48 Wm-1K-1 respectively. The observed temperature discontinuities across the interfaces between enamel, dentine and pulp-chamber layers were due to the difference of thermal conductivities at interfaces rather than to the phase transformation. The temperature gradient distributes continuously across the enamel and dentine layers and their junction below a temperature of 42°C, whilst a negative thermal resistance is observed at interfaces above 42°C. These results suggest that the microstructure of the dentin-enamel junction (DEJ) junction play an important role in tooth heat transfer and protects the pulp from heat damage.

PurposeTo analyze the outcomes and toxicities of induction chemotherapy (ICT) followed by concurrent chemoradiotherapy (CCRT) plus adjuvant chemotherapy (ACT) in patients with locoregionally advanced nasopharyngeal carcinoma (LA-NPC).MethodsRetrospective analysis of 163 patients with LA-NPC referred from August 2015 to December 2018 was carried out. All patients underwent platinum-based ICT followed by CCRT plus ACT.ResultsThe median follow-up time was 40 months, ranging from 5 to 69 months. The 3-year disease-free survival (DFS), overall survival (OS), locoregional recurrence-free survival (LRRFS), and distant metastasis-free survival (DMFS) rates were 80.8, 90.0, 91.6, and 87.4%, respectively. The most frequent acute grade 3/4 adverse events were leukopenia (66.8%), neutropenia (55.8%), mucositis (41.1%), thrombocytopenia (27.0%), and anemia (14.7%).ConclusionICT followed by CCRT plus ACT did not seemingly enhance DFS and OS in LA-NPC patients compared to the addition of ICT to CCRT (historical controls). In contrast, ICT followed by CCRT plus ACT had more acute adverse events than ICT followed by CCRT. Longer-term clinical studies are required to examine the treatment outcomes and late toxicities.