Periodontal disease is one of the most frequently diagnosed disease processes in primary care practice. The prevalence varies widely and depends on the depth of examination undertaken. In conscious awake animals, in examinations based on visual assessment, prevalence has been reported to be between 9.3 and 18.2 percent. In detailed examinations under anaesthesia, the prevalence has been reported to be much higher at between 44 and 100 percent (Wallis and Holcombe, 2020).
The prevalence also varies depending on the breed of dog. In a recent large-scale study including 22,333 dogs, certain breeds were found to have a significantly higher incidence of periodontal disease. Breeds with the highest adjusted odds of disease included the Toy Poodle, King Charles Spaniel, Lhasa Apso, Greyhound and Yorkshire Terrier. It was also reported that dogs weighing under 10kg had three times the adjusted odds for periodontal disease when compared to dogs over 40kg (O’Neill et al., 2021). In Yorkshire Terriers specifically, at 37 weeks of age periodontal disease was reported to be present in at least one tooth or tooth aspect (Wallis et al., 2019) and recent studies have suggested an incidence of close to 90 percent in all dental patients (Stella et al., 2018). It is for these reasons that periodontal disease has been highlighted as a significant welfare concern (Niemiec et al., 2020).
How is periodontal disease defined?
Dental diseases can be split into two defined stages: gingivitis and periodontitis. Gingivitis is the early stage manifesting in inflammation of the gingiva. This stage is reversible by removal of the plaque biofilm through dental treatments, supported by an effective oral homecare regimen. If left untreated, gingivitis can progress to periodontitis where destruction of the supporting tooth structures, ie the periodontal ligament, cementum and bone, occurs. Periodontal disease stage 1 (PD1) has been associated with up to a 25 percent loss of tooth-supporting structures and in extreme cases (PD3/4), over 50 percent of supporting structures can be lost (Davis et al., 2013). These changes, once they have occurred, are irreversible.
Periodontal disease stage 1 has been associated with up to a 25 percent loss of tooth-supporting structures and in extreme cases, over 50 percent of supporting structures can be lost
The severity of periodontal disease has been shown to have little correlation with increasing numbers of bacteria, but by the change in the oral microbiome population. In canine periodontal disease, the oral microbiome shifts from a mainly Gram-negative aerobic population to a Gram-positive anaerobic population (Davis et al., 2013).
Build-up of subgingival plaque causes inflammation of the gingiva and periodontal tissues to occur, leading to recession and tissue damage. The severity depends on the host’s own immune response and the virulence of the bacteria present. The loss of the periodontal tissues occurs progressively towards the tooth root, leading to attachment loss and ultimately loss of the tooth (Niemiec et al., 2020).
Diagnosis of periodontal disease
Clinical features of periodontal disease include inflammation of the gingiva, bleeding of the gumline on probing and halitosis. As the disease progresses, attachment loss becomes evident; this can be visualised on examination as gingival recession and also via periodontal pocketing. The consequences for periodontal disease are initially at a local level, and include oro-nasal fistulas, local osteomyelitis and pathological fractures, mainly of the mandible. Progression can result in an ascending infection that can affect optic tissues, or at a systemic level, due to inflammatory mediators and bacterial translocation, a negative effect on major organs such as the heart, liver and kidneys can be seen (Niemiec et al., 2020).
It has been recently reported that to accurately diagnose periodontal disease and effectively stage the pathology, a detailed exam must be carried out under general anaesthesia (Stella et al., 2018). In most primary care practices, this could involve a two-stage process, with the first stage consisting of a general anaesthetic and identification of pathology/staging and the second stage potentially involving a further general anaesthetic to implement the appropriate clinical treatment.
The significant difference in prevalence of periodontal disease on conscious exam compared to exam under anaesthetic highlights the needs for improved and earlier diagnosis
There are several challenges that vets may face with this approach. To proceed with a dental or not can be a complex discussion with the pet owner, and the decision to go ahead is often multifactorial based on potential time for procedure, staff experience, cost, perceived outcome for owner and pet, and risk versus benefit for the patient. Until this point, in the UK no diagnostic test has existed for periodontal disease where pathology is not visible, being hidden under the gumline. The significant difference in prevalence of periodontal disease on conscious exam compared to exam under anaesthetic (Wallis and Holcombe, 2020) highlights the needs for improved and earlier diagnosis.
Detection of thiols
In humans, it has been reported that volatile sulphur compounds, or thiols, produced by oral microbes are the primary contributors to halitosis. Two key thiols identified were hydrogen sulfide (H2S) and methylmercaptan (CH3SH) (Van den Velde et al., 2009) and these have been reported to be associated with, and are significant in, the progression of periodontal disease in dogs too (Nordhoff et al., 2008).
Thiols have also been shown to decrease following professional periodontal therapy(Rawlings and Culham, 1998). They can be detected in oral fluid and a novel diagnostic test strip has been developed (Marretta et al., 2012). The recently released WSAVA Global Dental Guidelines advocate the use of a thiol detection strip in examination rooms as an indicator for gingival health and periodontal disease (Niemiec et al., 2020).
A pilot study by Marretta et al. (2012) evaluated a test strip to determine dissolved thiol concentrations as an indicator of gingival health and periodontal status. The test strips, which comprised a small porous pad with a plastic backing impregnated with a thiol detection reagent, estimated the level of thiols dissolved in oral fluid, and provided a colorimetric change to the thiol detection reagent in the pad (Figure 1). The intensity of the colour changed directly with increasing thiol levels. The colour change can be shown to pet owners in the consulting room as a visual aid to augment the veterinary surgeon’s clinical points during the dental conversation and strengthen the argument to progress to professional dental treatments (Figure 2). Correlation between increased thiol detection scores in this study with worsening periodontal inflammation showed promise, with further studies recommended (Marretta et al., 2012).
The colour change can be shown to pet owners in the consulting room as a visual aid to augment the veterinary surgeon’s clinical points […] and strengthen the argument to progress to professional dental treatments
A more recent study confirmed that thiol detection strips can detect active periodontal disease which has not been diagnosed during the conscious exam of the oral cavity (Queck et al., 2018). The results revealed that a visual conscious exam of the patient significantly underestimates the presence of periodontal disease and at what active stage it is present. The thiol detection strip detected periodontal disease when no visual cues were present (Queck et al., 2018), indicating the strips’ value in aiding earlier opportunity for interventions in the treatment and prevention of periodontal disease.
Thiol detection strips could be used across the primary care practice such as in nursing clinics, wellness checks for routine vaccinations or regular health-plan check-ups, as well as in cases of suspected periodontal disease where no pathology can be visualised.
The strips can aid in early detection of periodontal disease to allow clinical intervention at earlier stages of the disease process. They could be used to augment the dental conversation positively and as a visual cue that can be easily seen by the pet owner, ultimately strengthening the discussion in favour of clinical intervention if required.
The tests may also improve owner compliance, dental procedure revenues, dental homecare revenues and the awareness of the importance of the early detection of periodontal disease (Goldstein et al., 2016). Ultimately, this can only be of benefit to animal welfare.