It is undeniable that equine dentistry has come into its own in recent years; the field that was previously neglected by the veterinary profession is now a staple of continuing professional development diaries around the world and many periodical publications would perhaps be somewhat thinner were it not for submissions dealing with matters relating to equine dentition. While equine clinicians will always be embarrassed by the relative mountain of collective knowledge available to those in the human dental sphere, huge strides have been made in recent years and the papers included in EVJ's first Virtual Issue, ‘Advances in equine dentistry: 2009 and 2010’ which is now available free online (http://onlinelibrary.wiley.com/) serve as an excellent illustration of this point.
The science of equine dentistry has lagged considerably behind its implementation, largely due to the paucity of equine dental research through much of the latter half of the twentieth century. Many techniques (and associated equipment) have been developed and widely applied in the absence of scientific validation and, as a consequence, much of the practice of equine dentistry to this day has a weak supporting evidence base. The huge demand for ‘answers’ for troublesome conditions relating to head carriage and mastication, allied with an increasingly competitive marketplace has served both to drive practitioners to formulate new approaches to treatment and to push equipment manufacturers into something approaching an ‘arms race’. Examples range from arbitrary rules used by practitioners in the performance of prophylactic and remedial dental work for dental ‘equilibration’ (Carmalt et al. 2006) through to procedures such as wolf tooth removal, diastema widening (Dixon et al. 2008) and filling of occlusal defects. While many such procedures have become part of the fabric of equine dental culture and might indeed be supported by substantial anecdotal success, objective scrutiny of efficacy and long-term outcome has been sorely lacking in most areas to date. The belated recognition of this knowledge deficit has however now fuelled a very productive phase of fundamental research from which workers in the field are starting to reap benefits.
That an understanding of what is ‘normal’ is prerequisite to the diagnosis (let alone treatment and prevention) of disease is an assumption that applies to all medical fields yet only recently have we started to accrue enough information to permit us to say tentatively that we are starting to ‘know’ the equine mouth in health. While much remains to be learnt, it would be remiss not to acknowledge the immense contribution to current equine dental knowledge made by the Edinburgh group led by Professor Paddy Dixon. Seminal papers by the group have been produced on dental morphology and physiology (Kilic et al. 1997a,b,c,d; Fitzgibbon et al. 2010), pathology (Dacre et al. 2007, 2008), and surgical (Dixon et al. 2005) and diagnostic (Townsend et al. 2011) techniques and have served to inspire satellite groups to conduct associated investigations, some of which are included in ‘Advances in equine dentistry: 2009 and 2010’. The publications drawn together in this virtual issue relating to pulpar anatomy of the equine cheek teeth (White and Dixon 2010; Bettiol and Dixon 2011) are excellent examples of scientific methods providing information that is not only easily digestible but directly relevant to first opinion clinicians undertaking procedures such as rostral profiling or diastema widening of cheek teeth; applicability to the ‘real world’ is a common thread in much of the Edinburgh research.
One of the problems faced by equine dental practitioners on a daily basis is determining whether what confronts them in the oral cavity is related to any clinical signs the horse may be displaying. It is a common failing to presume that detection of abnormality within a mouth is always significant and equally that treatment of any such abnormality should always be effected. As more is revealed about the equine mouth it is becoming clear that ‘normal’ as defined by the absence of masticatory or ridden dysfunction rarely goes hand-in-hand with absence of oral/dental pathology. With most oral pathology, whether it is buccal ulceration, diastemata, dental infection or focal overgrowth, there is no linear relationship with exhibited pain. Horses free from external clinical signs may have marked overgrowths, fractured teeth or severe diastemata, yet others with relatively minor oral findings may for instance be presented for painful mastication or head carriage problems. The increasingly widespread use of oral endoscopy has led to greater documentation of the ‘fine detail’ of the erupted dental tissues and clinicians investigating sinonasal disorders must make judgements on the importance with respect to tooth vitality of findings such as pitting of secondary dentine overlying pulp chambers or focal gingival lesions (Ramzan 2009). It is essential, therefore, that associations between clinical and pathological findings are tested objectively, and ‘Advances in equine dentistry: 2009 and 2010’ includes excellent examples of this by Windley and others (2009b) and Casey and Tremaine (2010).
Given that the science of equine dentistry is largely a blank canvas, it is no surprise that observational studies, particularly those drawn from practitioners' experience should also play a prominent role at the present time. The absence of published information on prevalence, distribution or outcome of treatment of any pathological process lends itself well to a democratisation of the literature and the field will continue to derive much benefit from practitioners applying scientific rigour to the documentation of their observations (Simhofer et al. 2008; Du Toit et al. 2009a,b,c; Ramzan et al. 2009; Gere and Dixon 2010; Ramzan and Palmer 2010). There is certainly no reason why clinicians ‘at the coal face’ cannot shed light on some of the big remaining ‘known unknowns’ in equine dentistry: the longitudinal progression of diastemata and periodontal disease, the prevalence and aetiology (and strategies for management) of cheek tooth malalignments, the necessity for wolf tooth removal, and the factors that determine whether a tooth remains vital following an infectious or traumatic insult are but a few of these.
Any discussion of the future direction of equine dental research must inevitably conclude with mention of the advent of advanced imaging techniques. While radiography remains the most widely applied imaging modality for equine head and dental disorders and has evolved in the digital age to be a tool of considerable usefulness (Townsend et al. 2011), computed tomography (CT) is undoubtably set to revolutionise the field. Computed tomography has of course been around for many years but the need for general anaesthesia has in the past greatly restricted uptake in equine practice. Based on the pioneering work of Alastair Nelson, the relatively recent introduction of CT units that permit imaging of the head of standing, sedated horses has proven a defining moment and the large caseload currently seen by multidetector scanners operational in UK referral centres (Townsend et al. 2009; Powell 2010; Ramzan 2010) is certain to expand our understanding of dental disease in a fashion that would have been inconceivable even a few years ago. It is not difficult to surmise what some of the early fruits of this new era will be: enhanced prognostication in cases of dentoalveolar infection and more targeted surgical correction of sinus disease must be chief among them. Researchers are already working with CT to unlock the relationship between tooth structure and pathological process, and clinicians who deal with the tricky business of tooth vitality in the context of exodontia or restorative work will find 3 relevant papers in the virtual issue (Veraa et al. 2009; Windley et al. 2009a,b). It is inevitable that better diagnosis and treatment outcomes for dental disease will ensue from CT; the days of removing the wrong tooth, or a tooth that might have happily remained in situ with alternative treatment are hopefully drawing to a close. The lessons learned from 3-dimensional imaging of the equine head will doubtless filter into the wider veterinary community to assist decision making even in populations for which CT is not accessible or economically viable.
So what can we expect of equine dentistry over the next few years? Understandably for a field in which so much remains to be discovered there will continue to be a steady stream of research papers crowding the veterinary press. Remedial techniques in current use will be either validated or debunked and new treatments for troublesome conditions such as periodontal disease will arise; CT and real-time intra-oral imaging will stimulate the development of standing surgical procedures of far greater elegance and precision than any available today. Equine dentistry has certainly arrived as a specialism in its own right.