Occlusal Considerations for Long-Term Functional Success by Dr Sam Jethwa

We as dentists, as mostly selfless and helpful creatures – want to try and realise dreams for our patients, and we often forget to mention, ‘ it will be ok’ – works sometimes, but when it doesn’t – we lose sleep. When we see ‘ broken tooth’ in our day list – after a restoration, our heart sinks – how can we limit this stress? There are certain factors we can control, and some we cannot. If we limit those we cannot control, we have done all we can to deliver a successful restoration. If we do not know what to look for, we will always leave controllable factors uncontrolled, and are treating patients with a ‘ fingers crossed’ approach, which is high risk.

Occlusion, Occlusion, Occlusion…
Occlusion is something that sends dentists into frenzy, with multiple definitions, complicated terminology, and various schools of thought. There are few topics that get discussed and argued with such passion or rage, than occlusion. However something we can all agree on, is that if we ignore the occlusion, we are heading into the dark. Without understanding the existing situation, and planning for success, the longevity of our anterior restorations is compromised.

The existing tooth wear, and chewing pattern:

‘ I believe that the more you know about the past, the better you are prepared for the future.’
~ Theodore Roosevelt

When assessing an anterior aesthetic case, the first intra oral examination I conduct is a bite assessment. We can learn from the existing presentation, what risks we may be faced with and if there are any limitations we must then discuss with the patient. An extra oral muscle examination can give us valuable information on the muscles of mastication, TMJ, and helps us identify any ligament laxity, tension, or other abnormalities. Alongside this we can assess the degree of opening, any deviation or deflection on opening and any pain on movement.

Fig 3 shows a typical presentation of lower incisal attrition. We come across patients with this appearance regularly, and often this will be teamed with no posterior wear at all. Or we will see a similar pattern of wear inconsistent with the patient’s age.

These patients fall into the “avoidance” category, where they may be avoiding a posterior interference and posturing forwards as a result. Thorough assessment of their anterior guidance will be needed prior to considering restorative work to ensure that we are within the limits of centric occlusion, or if we require restoration in centric relation. The risk of restoring the opposing teeth, or these lower incisors in a situation such as this, without detailed occlusal assessment, is fracture, and incisal chipping. The reasons for this can either be natural interferences, or previous orthodontics, or multiple single tooth restorations over time.

An alternative pattern is knows as a “destructive” pattern, which can be identified in a mouth with obvious decreased OVD and generalised attrition across the dentition. This is more, and can be challenging to rectify.

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  Fig 1: Natural and functional porcelain restorations, harmonious with the lips

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  Fig 2: We can sometimes have a cracking time in dentistry! A fractured porcelain veneer

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  Fig 3: Male patient in his mid 60s - a common sight - worn lower anterior teeth

A case such as in Fig 4 can be managed, after all the discussions as mentioned in part 1 are taken into account, the occlusion is then assessed in detail and in addition a horseshoe shaped articulating paper is used by asking the patient to chew.

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  Fig 4: A patient in her mid 50s, with a constricted chewing pattern, multiple single tooth restorations, some over-erupted posterior teeth and anterior wear. One of the patient’s complaints was a repeatedly de-bonding anterior composite restoration (UL2).

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  Fig 5: Male patient in his late 30s, treated in centric relation

This highlights any heavy occlusal contacts in the anterior segment - these should be faint or non-existent entirely. Knowing this will aid our treatment planning, and may indicate a place for pre restorative orthodontics to reposition the lower incisors prior to restoration of the upper anterior teeth.

Deprogramming the patient using an anterior jig, or Kois Deprogrammer, will allow us to determine the centric relation bite – a reproducible position where the mandible is fully seated in the condyle with the muscles in a relaxed state.

This allows a construction of a trial smile, to trial the new occlusal scheme until the function has become balanced enough to move to our final restorations. In some cases this trial period can be a matter of months, so it is paramount to ensure interdental cleaning aids can be used despite the temporary smile being splinted to limit any gingival inflammation.

Regular review appointments, and regular occlusal adjustments are made until a balanced and stable scheme is identified. This can in some cases involve building the patient’s dentition up to their first point of contact, either in composite resin or porcelain.

These cases are mostly additive, and therefore conservatively managed. Once treated, we can expect a result where restorations are mostly bonded to enamel, and a balanced occlusal scheme has been produced – predictability can be expected. However educating our patients to appreciate factors beyond our control is something we must not ignore.

In some cases a laboratory hard splint can be recommended for nightly wear.

Conclusion
If treatment planning is conducted with the patient’s main concerns in mind, and existing occlusal issues are identified at an early stage, we can then plan for functional, and aesthetic success.

There will be inevitable failures long term, for one of the multiple reasons outlined above, however most we will be able to predict and be able to pre warn our patients about, thus allowing us to practice with more confidence, and our clients to escape from the stress of dentistry, and enjoy the rewards a beautiful, healthy, smile can give.

Example case
Patient P in her late 40s attended, her goals were discussed and her occlusion was assessed. Thin and chipped incisal edges were noted along with a chewing pattern with heavy contact across the anterior segment.

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  Fig 6: Pre op presentation

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  Fig 7: Trial Smile – resin temp material and flowable resin composite

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  Fig 8: Post Op – porcelain restorations fitted, produced as a copy of the trial smile

Once we have cemented using our standardised bonding protocols, we must then assess excursions and guidance to ensure we are leaving the patient with a functional, comfortable, and balanced result.

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  Fig 9: Asking the patient to slide their lower jaw forwards tests protrusive guidance. More than a single anterior tooth should be in contact

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  Fig 10: Asking the patient to slide their lower jaw to the right tests the right lateral excursion, contacts on the right side are working contacts; contacts on the left side are non-working contacts. In this case we can see canine guidance, which is preferred

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  Fig 11: Asking the patient to slide their lower jaw to the left tests the left lateral excursion, contacts on the left side are working contacts; contacts on the right side are non-working contacts. In this case we can see we are lacking canine guidance due to mal-positioned teeth

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  Fig 12: Asking the patient to slide their lower jaw forwards but left, and also forwards but right, tests the inter-incisal guidance. This excursion should be free of the incisal edge of the lateral incisors in both forward and backward motions.

Dr Sam Jethwa BDS (Lon) MFDS RCS (Edin) PgDip ClinEd