ABSTRACT
OBJECTIVE: The authors examined two novel and objective methods for diagnosing stained, carious, and sound dentine, a mechanico-acoustic method and a laser-acoustic method, and compared these with the conventional but subjective method of visual and tactile assessment using a dental probe. SUMMARY BACKGROUND DATA: It is accepted clinical practice to leave stained but relatively firm dentine on the pulpal surface of dental cavities prepared for restoration. The problem for the clinician is in deciding which dentine is carious and which is stained but acceptable to be left in situ. There is no objective method for making this decision, it is usually made on the basis of visual examination and tactile assessment using a dental probe. METHODS: The authors used Fourier analysis of acoustic waves arising from mechanical (dental probe) or laser (Er:YAG laser) interaction with the tooth surface and compared the results with the subjective assessment of the same tissue surfaces as judged by a clinician using visual and tactile assessment with the same dental probe. RESULTS: The results showed that both the mechanico-acoustic and laser-acoustic methods were more accurate and more objective than the conventional visual/tactile method and that an analysis of both the integral and spectral signals produced by the Er:Yag Laser (lambda = 2.94 microns) allowed for a more accurate diagnosis than the other two methods examined. CONCLUSIONS: Both mechanico-acoustic and laser-acoustic methods of diagnosing sound, stained, and carious dentine were more accurate than the subjective visual/tactile method using a dental probe. The laser-acoustic method was the most accurate of all of the methods compared. An advantage of the laser-acoustic method is that it could be included into the actual process of cavity preparation when using an Er:YAG laser, providing an objective and more accurate assessment of the nature of the remaining dentin and may therefore be more economic of time, eliminating the necessity for constant cessation of drilling to assess the nature of the target tissue.
