Since the late eighties pulsed infrared lasers like the Er:YAG and the Er,Cr:YSGG lasers are available for dentists. These lasers appear to have interesting applications in endodontics. It was demonstrated in vitro, with dyes, that a root canal can effectively be irrigated with them. Initially these lasers were recommended for preparation of enamel, dentin and bone and for surgery. The way that it worked in a root canal in combination with a liquid was, however, not clear. With a special high speed imaging technique the working mechanism of a pulsed infrared laser was studied, using a model of a root canal in a basin filled with either water or with a 5% NaOCl solution. The working mechanism can be attributed to the high stream of liquid, the turbulence and the cavity-effects, created by explosive vapour bubbles. These phenomena appear to make a major contribution to the cleansing and disinfecting of the root canal.

In recent years it has become more and more apparent that contract research not only has obvious advantages, but risks also. It has been found that occasionally investigators are pressed to modify the conclusions of their work if the conclusions conflict with the interests of the funding organisation. In other cases, the publication of results is obstructed or retarded. Not only commercial companies, but also governmental and other non-profit institutions are guilty of these practices. If research findings are not presented or are presented in an altered form, not only will science be obstructed, but also the entire society will suffer. The responsibility for preventing these practices not only falls with the investigators, but also with their research institutions and the funding organisations.

In every case of restorative care, dentists deal with reference positions of the mandible. For this purpose, the intercuspal position and the retruded contact position are the most often used reference positions. Concerning how precisely these clinically relevant positions could be determined, insufficient knowledge was available 25 years ago. There was also uncertainty concerning the causal role of the occlusion in cases of temporomandibular disorders. It was established that the reproducibility of the retruded contact position and other reference positions established by the dentist, did not differ from one another. The position of the patient had no influence on reproducibility, nor did the choice of bite registration material. The intercuspal position is the most reproducible reference position in all conditions tested. The opinion, widely held at the time, that a discrepancy between the reference positions would lead to temporomandibular disorders was addressed in the dissertation ´Reference Positions in the Mandible´.