Acta Veterinaria Scandinavica Research Caries in the infundibulum of the second upper premolar tooth in the horse Torbjörn S Lundström1, Gunnar G Dahlén2 and Ove S Wattle*1 BioMed Central Open Access Address: 1Section of Large Animal Medicine and Surgery, Department of Clinical Sciences, Swedish University of Agricultural Sciences, Box 7054, 750 07 Uppsala, Sweden and 2Laboratory for Oral Microbiology, Faculty of Odontology, Sahlgrenska Academy at Göteborg, Sweden Email: Torbjörn S Lundström - dtv@djurtandvardskliniken.se; Gunnar G Dahlén - dahlen@odontologi.gu.se; Ove S Wattle* - ove.wattle@kv.slu.se * Corresponding author Published: 28 March 2007 Acta Veterinaria Scandinavica 2007, 49:10 doi:10.1186/1751-0147-49-10 This article is available from: http://www.actavetscand.com/content/49/1/10 Received: 11 September 2006 Accepted: 28 March 2007 © 2007 Lundström et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Swedish equine dental practices have empirically found that the prevalence of infundibular caries as a primary disorder in the first permanent premolar teeth (P2) of the horse upper jaw has increased during the last 10 years. A previously unknown bacterial species, Streptococcus devriesei (CCUG 47155T), which is related to Streptococcus mutans, has recently been isolated from these carious lesions. To understand the aetiology of caries in horses, it is essential to elucidate the relationship between S. devriesei and P2 infundibular caries. Methods: The anterior infundibulum of maxillary P2, or the occlusal surface at the site of the infundibulum, in 117 horses and ponies, 77 with and 40 without caries in this tooth, was sampled for bacteriological analyses between 1990 and 2004. Samples were transported in VMGA III medium and then inoculated onto MSB agar. The approximate number of bacteria was counted in each sample and the isolates were characterised biochemically, using a commercial kit. Results: All 50 samples taken from carious lesions after 2002 were positive for an S. mutans-like strain, i.e. S. devriesei. The bacteria were also found in four of the control animals, but were much less numerous than in samples from caries-affected horses. None of the swabs taken prior to 2002 were positive for this bacteria. Conclusion: Our results demonstrate that S. devriesei can colonise the infundibulum of P2 of the horse upper jaw, which can be fatal for the dental tissue. We conclude that S. devriesei is strongly associated with P2 caries in horses. Background The development of dental caries in humans has been dis- cussed in terms of an interaction between three main fac- tors: bacteria, substrate, and teeth [1]. Owing to their ability to produce extracellular polysaccharides (polyglu- cans) from sucrose, certain bacterial species, e.g. strepto- cocci, can adhere more easily to the tooth surface [2]. Members of the group of mutans streptococci (e.g. S. mutans and S. sobrinus) are unique in this sense, since their polyglucans are more water insoluble and become sticky when produced in dental plaque [1]. Tooth defects in the form of small fissures or enamel cracks, on the occlusal surface facilitate bacterial colonisation. In a favourable environment, such as the presence of abundant sugars within a tooth fissure, these bacteria produce lactic acids [3,4] in a manner that decreases the pH below the critical Page 1 of 9 (page number not for citation purposes)