Acta Veterinaria Scandinavica 2007, 49:10 http://www.actavetscand.com/content/49/1/10 FNiogrumreal 1permanent maxillary P2 Normal permanent maxillary P2. Photograph of a P2 occlusal surface. C = cement (light brown), D1 = primary dentin (white/yellowish), D2 = secondary dentin overlying pulp horn (dark brown). * = enamel (visible as a winding ridge). I = infundibulum, (A cone shaped invagination from the occlusal surface of the tooth. The invagination is lined with enamel and filled with cementum (C) to different degrees).8 bottle containing 3.3 ml of VMGA III (Viability Medium, Göteborg, Anaerobically prepared III, Sahlgrenska Acad- emy, Göteborg, Sweden) transport medium (Fig. 6). VMGA III is a special transport medium for human oral bacteria, including streptococci [17]. The anterior infundibulum of the left or right P2 of the upper jaw of control horses was sampled randomly in the same man- ner. In control horses with a closed infundibulum, the sample was taken from the occlusal surface at the site of the infundibulum. Further, as an internal control, samples were taken from the second permanent premolar (P3) in the lower jaw on the opposite side in all control horses and in 30 of the animals with carious lesions. The samples were sent the same day by mail to the Labo- ratory for Oral Microbiology, Faculty of Odontology, Sahlgrenska Academy at Göteborg University, Sweden, for analysis. The samples were all processed at the laboratory within 24 hours of the sampling procedure by a standard method for analysing the bacterial composition in dental caries, with special reference to S. mutans and related spe- cies, using a selective Mitis Salivarius-Bacitracin (MSB) agar [18]. The samples were made up in a 10-fold dilution series and 0.1 ml from each dilution step was inoculated onto an MSB agar plate and incubated for 3 days at 37°C in an atmosphere with 10% CO2 in N2. The appearance and numbers of colony forming units (CFU) of S. devrie- sei were determined visually according to standard proce- dures [19]. In accordance with these standard procedures, the total number of bacteria, CFU per ml VMGAIII, i.e. including all types of bacteria collected, was estimated in each sample and the results were categorised as 0, <100 Page 3 of 9 (page number not for citation purposes)