Establishment Of Cracked Tooth Vitro Experimental Model And Application Of Photoacoustic Tomography Imaging System

Objective:To establish a vitro model of cracked tooth for detection study and apply the photoacoustic tomography imaging system in detection of cracked tooth.Method:Obtained 12 freshly extracted teeth,divided into 4 groups.Every group contained 3 specimens,3 integrate teeth without wet-wrapping for Gl;3 crowns of teeth without wet-wrapping for G2;3 integrate teeth with 2 layer wet-wrapping for G3;3 integrate teeth with 4 layer wet-wrapping for G4.Lowest temperature was-196?,stored for 12h,highest was 90 ?,stored for 5min.Obtained 2 freshly extracted teeth.Specimen 1 was an integral tooth,neither lesions nor attrition on the crown.Specimen 2 was damaged on the buccal and lingual surfaces by the forceps,and with white spot enamel caries on the promial surface,which were not discovered by radiological examination.Photoacoustic tomography imaging system scanned two specimens,reconstructed the image of specimens by delay and sum algorithm.The PA signal was processed by Time-Domain and Frequency-Domain analysis.Two signal processing methods were compared.Results:Specimens in G1 and G2 had cracks in enamel and dentin after experiment,but 2 of the specimens was fractured.However,in G3 and G4.cracks of crown were not evoked by the same temperature changing progress.Photoacoustic tomography imaging system reconstructed the cross-section images of specimens.The results of different signal processing methods showed different information.Frequency-Domain analysis distinguished enamel and dentin,normal tissue and lesion more clearly.Conclusion:Temperature gap can create cracks in enamel and dentin.Wet-wrapping can adjust the temperature change of the tissue.Photoacoustic tomography imaging system can reconstruct the cross-section structure of the teeth.