Principles

In order to attain longer-term success with restorative care, it is paramount to develop a fundamental appreciation of clinical occlusion. However, clinical occlusion is a subject in dentistry over which many operators unfortunately develop deep anxiety! Sometimes the applied nomenclature and the manner in which various concepts are portrayed can be confusing, in particular the means by which they may relate to practical procedures and their functional relevance. The aim of this part of the book is therefore to keep matters simple, succinct and relevant to everyday clinical practice.

Failure to provide a mechanically sound masticatory system that is conducive to optimal function with desirable levels of load distribution and minimal concomitant trauma to the investing structures will culminate in premature restorative failure. There is also a risk of causing iatrogenic damage to the residual tissues, as well as possible instability concerning the spatial position of a tooth or teeth within the dental arches.

The clinician must therefore be aware of the concept of the ideal occlusal scheme. An assessment of the patient’s existing occlusal scheme should be carried out with reference to this standard. The assessment should take into account both static and dynamic components of the patient’s occlusal scheme.

As part of good clinical practice, a preliminary occlusal assessment should be carried out when undertaking a routine patient examination. However, there are certain circumstances where a more detailed evaluation may be indicated. These would include the following:

• The presence of pathological tooth wear
• A history of recurrently fracturing teeth or restorations
• Where restorations involving the occlusal table are being planned (of both the direct and indirect varieties)
• Presence of temporomandibular joint disorders
• Instability within the dental arch, such as increased tooth mobility or movement.

This chapter will address the clinical stages involved as part of the occlusal assessment.

Procedures

A thorough examination of the temporomandibular joints is recommended. Ask your patient to point to any areas of their head or face that may be symptomatic on maximal opening – if they point to a muscular area, it may be suggestive of muscular dysfunction.

A note of the presence of any mandibular deviation on opening and closing movements is useful. The maximum degree of mandibular opening should be determined by measuring the interincisal distance; any distance less than 35 mm is considered to be restricted. The maximum degree of lateral movement should also be determined; the normal is accepted to be about 12 mm.

Bilaterally palpate the masticatory muscles by pressing them between your thumb placed extra-orally and index finger intra-orally, and observe the presence of hypertrophy, tenderness or discomfort, particularly in areas of muscle insertion. The anterior and posterior temporalis muscles and the superficial and deep masseter muscles are perhaps the most relevant in this context. However, you may also wish to assess the anterior digastric, sternomastoid, trapezius and medial and lateral pterygoid muscles.

Make a note of the appearance of your patient’s face: a square profile, usually due to hypertrophy of the masseter muscles, may be suggestive of a tendency towards a parafunctional tooth-clenching habit. It is commonplace also to describe the skeletal profile.

A detailed intra-oral occlusal evaluation should take into account both static and dynamic features. The former are traditionally noted during the classical orthodontic assessment. The static occlusal examination should take note of the presence of any of the following features: