G. J. Seal, Y.-L. Ng, D. Spratt, M. Bhatti & K. Gulabivala
Departments of Conservative Dentistry and Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University College London, London, UK.

Aim.
To compare the bacterial killing of Streptococcus intermedius biofilms in root canals using lethal photosensitization with various combinations of photosensitizer concentration and laser light dose or 3% sodium hypochlorite (NaOCl) irrigation.

Conclusions.
The combined use of a photosensitizing agent and a low power laser directed at the access cavity was bactericidal to S. intermedius biofilms in root canals but was unable to achieve total kill, unlike 3% NaOCl.

M.-K. Wu, D. Barkis, A. Roris & P. R. Wesselink
Department of Cariology, Endodontology and Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, the Netherlands.

Aim.
The aim of this study was to determine whether the first file that binds at the working length corresponds to the canal diameter.

Conclusions.
Neither the first K-file nor the first Lightspeed instrument that bound at the working length accurately reflected the diameter of the apical canal in curved mandibular premolars. It is uncertain whether dentine can be removed from the entire circumference of the canal wall by filing the root canal to three sizes larger than the file that binds first.

G. Yoshikawa, Y. Murashima, R. Wadachi, N. Sawada & H. Suda
Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.

Aim.
The purpose of the present study was to evaluate the effects of resorbable and non-resorbable membranes, and calcium sulphate on bone regeneration in osseous defects in conjunction with apicectomy.

Conclusions.
The findings of the present study showed that e-PTFE membrane was most effective for bone regeneration into osseous defects in conjunction with apicectomy; that the resorbable membranes used were not effective compared with controls; and, that calcium sulphate could be substituted for e-PTFE membrane. However, additional experiments are required to determine whether or not calcium sulphate is effective for complicated types of osseous defect, such as combined endodontic-periodontal lesions and through-and-through osseous defects.

D. Tziafas, O. Pantelidou, A. Alvanou, G. Belibasakis  & S. Papadimitriou
Departments of  Endodontology, School of Dentistry,  Histology and Embryology, Faculty of Medicine,
Clinical Sciences/Surgery Clinic, School of Veterinary Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Aim.
The objective of the present experiment was to study the early pulpal cell response and the onset of reparative dentine formation after capping application of MTA in mechanically exposed pulps.

Conclusions.
The present experiments indicate that MTA is an effective pulp-capping material, able to stimulate hard tissue bridge formation during the early wound healing process. The stereotypic pulp defence mechanism by which primitive matrix (fibrodentine) trigger expression of the odontoblastic potential of pulpal cells seems to be related to the dentinogenic activity of MTA. Further experimental data are needed to determine whether interactions between extracellular matrix components (including fibronectin) and endogenous signaling molecules (growth factors) take place after pulp capping with MTA.