Occlusion

What’s in a Bite?

Fortunately for us the vast majority of dental treatments are highly successful and we have happy patients. However, when things go wrong there is a risk of both complaint and litigation. Our Protection Societies tell me that there is more dental litigation per head of population in the UK than the USA!

As part of the litigation process your records will be reviewed and your patient examined by an Expert Witness. When I acted as an Expert Witness there were many cases where extensive restorations had been carried out without regard to the occlusion, and no record that a detailed occlusal examination had been carried out, even when patients had been complaining of symptoms highly suggestive of TMJ dysfunction syndrome, undermining any defence that you might wish to make.

The next stage is to consider what we need to know about each patient’s occlusion and the creation of a systematic occlusion and TMJ examination pro forma on which you can record your clinical findings. This ensures that you do not forget any stage. Whilst this was my chosen order, please feel free to change to suit your own preferences. If you do not already have one available, then a stethoscope is one item you must buy.

  1. Angles classification: I, II div I, II div II or III.
  2. Overbite and overjet in millimetres, and whether complete or incomplete.
  3. The relation of the first molars: Class I, II, or III.
  4. Any missing teeth.
  5. Any teeth that have tipped or overerupted.

Mandibular posterior teeth tend to tip mesially into spaces whilst maxillary teeth both tip mesially and rotate around the axis of the palatal root. It is also common to find that maxillary palatal cusps are below the natural line of the Curve of Monson.

  1. Any mobile teeth?
  2. Are border mandibular movements canine protected, group function or are there interferences on either side?
  3. What is the interincisal opening in millimetres?

Here you are looking for any trismus. The usual minimum opening is 35mm.

  1. Is there any deviation on opening to either right or left?

You need to stand behind the patient to see this.

  1. Using Dawson manoeuvre (See 20 Answers) manipulate the mandible and place the condyles in centric relation. Gently close. Do the teeth go into centric occlusion. Do centric relation and centric occlusion coincide or not.
  2. If no to question 10, where are the initial contacts, and in what direction does the mandible move to reach centric occlusion? (Fig 1)

Occlusion at centric jaw relation

Centric occlusion

12. What is the occlusal vertical dimension?

 

Rest vertical dimension?

These two dimensions enable you to calculate the freeway space, normally 3 – 4mm anteriorly.

OVD at initial contact?

The latter is an important measurement as there may well be no freeway space.

  1. Use your stethoscope to listen to the sounds of the temporomandibular joint during opening and closing. You are listening for:
  • Clicking – a sign that there is a disc abnormality and a pointer to TMJ dysfunction
  • Crepitus – a sign that there are degenerative changes within the joint from osteoarthritis, rheumatoid arthritis or rarely psoriatic arthritis.
  1. The final stage is palpation of the muscles of mastication for tenderness. This is normally graded on a subjective scale of one + for slight tenderness to 3+++ for a very tender muscle.

Temporalis

Palpate the temple through the skin remembering that there are both vertical and horizontal fibres.

Masseter

Palpate either through the skin or, ask the patient to open their mouth slightly and palpate laterally the ascending ramus on each side.

Lateral Pterygoid

Sit in front of your patient who should have their mouth half open. On the left side slide your right forefinger along the the buccal aspect of the maxilla, between it and the ascending ramus of the mandible. Gently push inwards and upwards. Note: tender lateral pterygoids are very common in patients with TMJ dysfunction syndrome. Palpate the right side similarly using your left forefinger.

Medial Pterygoid

Warn your patient that the next test may ‘be a bit yucky’ Using your right forefinger slide it into the lingual sulcus between the lingual border of the mandible and tongue , under the mylohyoid ridge then press quickly laterally. Use your left forefinger similarly on the left side.

You have now gained a great deal of information about your patient’s occlusion. What it all means will be discussed in my next section

For the many computer literate, you should be able to create a section in each patient’s file to supplement the usual dental chart, periodontal and Spacemark chart. Alternatively you can create a paper questionnaire record.

Over to you.

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