Oral Examination Under General Anaesthesia
Examination Under General Anaesthesia
The endotracheal tube does not allow full closure of the mouth to examine the relationship between the teeth. In the anaesthetised patient prior to intubation, the muscles are relaxed and the tongue often gets in the way, so a complete evaluation of occlusion is not always possible.
The oropharynx should be examined prior to endotracheal intubation. Normal anatomical features of the oral cavity need to be identified and inspected. A check list is given below:
Any abnormalities need to be noted – look for swellings, inflammation, ulcerations. Check if the lesion is localised to one area or more generalised. Always biopsy abnormal tissue if a cause cannot be identified.
Under general anaesthesia, it is also useful to recheck the temporomandibular joints for crepitus or clicks if a problem is suspected. The mandibular symphysis should also be checked for mobility – a small degree of movement is normal in cats.
The following indices and criteria should be evaluated for each tooth:
- Gingivitis and gingival index
- Periodontal probing depth
- Gingival recession
- Furcation involvement
In animals with large accumulations of dental deposits (plaque and calculus) on the teeth, it may be necessary to remove these to assess periodontal status accurately. Care must be taken not to damage the gingival tissues whilst removing the calculus.
Instruments Used to Examine the Mouth
The periodontal probe is used to:
- Measure periodontal probing depth
- Assess the degree of gingival inflammation
- Evaluate furcation lesions
- Evaluate extent of tooth mobility
The dental explorer or probe, a sharp-ended instrument, is used to:
- Determine the presence of caries
- Explore other enamel and dentin defects, e.g.fracture, odontoclastic resorptive lesions
Dental Record Sheets
Various charts are available and the particular choice depends on operator preference. A complete dental record is required for diagnostic and therapeutic purposes, as well as for medicolegal reasons.
Gingivitis and Gingival Index
The presence and degree of gingivitis (inflammation of the gingiva) is assessed based on a combination of redness and swelling, as well as presence or absence of bleeding on gentle probing of the gingival sulcus. An index which relies on both visual inspection and bleeding, namely the modified Löe and Silness gingival index (Löe, 1967), can also be used:
Gingival index 0 - Clinically healthy gingiva
Gingival index 1 - Mild gingivitis: slight reddening and swelling of the gingival margin; no bleeding on gentle probing of the gingival sulcus
Gingival index 2 - Moderate gingivitis: the gingival margin is red and swollen; gentle probing of the gingival sulcus results in bleeding
Gingival index 3 - Severe gingivitis: the gingival margin is very swollen with a red or bluish-red color; there is spontaneous hemorrhage and/or ulceration of the gingival margin
Periodontal Probing Depth (PPD)
The depth of the sulcus can be assessed by gently inserting a graduated periodontal probe until resistance is encountered at the base of the sulcus. The depth from the free gingival margin to the base of the sulcus is measured in mm at several locations around the whole circumference of the tooth. The probe is moved gently horizontally, walking along the floor of the sulcus. The gingival sulcus is 1–3 mm deep in the dog and 0.5–1 mm in the cat. Measurements in excess of these values usually indicate periodontal disease, when the periodontal ligament has been destroyed and alveolar bone resorbed, thus allowing the probe to be inserted to a greater depth. The term used to describe this is periodontal pocketing. All sites with periodontal pocketing should be accurately recorded. Gingival inflammation resulting in swelling or hyperplasia of the free gingiva will, of course, also result in measuring sulcus depths in excess of normal values. In these situations, the term pseudopocketing is used, as the periodontal ligament and bone are intact (i.e.there is no evidence of periodontitis) and the increase in PPD is due to swelling or hyperplasia of the gingiva.
Gingival recession is also measured using a periodontal probe. It is the distance (in mm) from the cemento-enamel junction to the free gingival margin. At sites with gingival recession, PPD may be within normal values despite loss of alveolar bone due to periodontitis.
Furcation involvement refers to the situation where the bone between the roots of multirooted teeth is destroyed due to periodontitis (Fig. 6.4). The furcation sites of multirooted teeth should be examined with either a periodontal probe. The grading of furcation involvement:
Grade 0 - No furcation involvement
Grade 1 - Initial furcation involvement: the furcation can be felt with the probe/explorer, but horizontal tissue destruction is less than 1/3 of the horizontal width of the furcation
Grade 2 - Partial furcation involvement: it is possible to explore the furcation but the probe/explorer cannot be passed through it from buccal to palatal/lingual; horizontal tissue destruction is more than 1/3 of the horizontal width of the furcation
Grade 3 - Total furcation involvement: the probe/explorer can be passed through the furcation from buccal to palatal/lingual
The extent of tooth mobility should be assessed using a suitable instrument, e.g. the blunt end of the handle of a dental mirror or probe. It should not be assessed using fingers directly, since the yield of the soft tissues of the fingers will mask the extent of tooth mobility. The grading of mobility:
Grade 0 - No mobility
Grade 1 - Horizontal movement of 1 mm or less
Grade 2 - Horizontal movement of more than 1 mm. Note that multirooted teeth are scored more severely and a horizontal mobility in excess of 1 mm is usually considered a Grade 3 even in the absence of vertical movement.
Grade 3 - Vertical as well as horizontal movement
Any surface defect of the crown needs to be identified and recorded. Surface defects are diagnosed using the explorer probe – the sharp point is run across the crown to identify any catches. Crown defects such as enamel dysplasia, fractured teeth (with or without pulp exposure), worn teeth, caries lesions or odontoclastic resorptive lesions are noted on the chart and treated appropriately.