THE NORTH, SOUTH, EAST AND WEST OF OCCLUSION

Dr Tom Bereznicki BDS (Edin)

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ASPECTS NOT BEING COVERED:

• The full clinical examination

• Anatomy of the joints or associated musculature

• Severe Skeletal Class 2 & 3 cases

• Anterior open bites

• Cross-bites

• TMJDS

• Bruxism

OCCLUSAL DETERIORATION STAGE 1

OCCLUSAL DETERIORATION STAGE 2

BASIC PRINCIPLES• In normal occlusions Centric Relation (CR) should be coincident

with maximum Intercuspation (ICP) - ???

• In lateral jaw excursions there should ideally be Canine Guidance or Group Function with or without Canine Guidance

• With the lower jaw in Working Side (WS) there should be no contacts on the Non- Working Side (NWS)

• In protrusive jaw movements all the contacts should be on the anterior teeth with no contacts on the posterior teeth

• Any undesirable contacts are known as premature contacts or prematurities in centric and interferences if in lateral and protrusive excursions

• Ideally there should be Anterior Guidance also known as a Anterior Protected Occlusion

“Most responses to occlusal disharmony are adaptive in nature

The possibility of converting a patient with a symptom free ‘adapting occlusion’ to one which is uncomfortable because

of “high fillings” increases with the number and complexity of the

restorations - moreover the response varies between individuals”

M Wise

CENTRIC

WHERE SHOULD THE CONDYLES BE?

Courtesy of Michael Wise

DO WE NEED TEETH TO FIND CENTRIC?

SHOULD RCP = ICP?

THE PERFECT BITE? ICP MAY BE UP TO 1mm ANTERIOR TO RCP

Figs (a) SHOW NORMAL OCCLUSAL CONTACTS, Figs (b) SHOW THE FREEDOM PATIENTS REQUIRE IN LONG CENTRIC

CENTRIC/INTERCUSPALCONFORMATIVE V REORGANISED

Conformative v reorganised

Food packing

TOOTH POSITION IS DICTATED BY THE NEUTRAL ZONE

IN THE PRESENCE OF PERIODONTAL DISEASE, OCCLUSAL FORCES DUE TO LOSS OF VERTICAL DIMENSION IN THE

POSTERIOR SEGMENTS CAN RESULT IN THE FRONT TEETH MIGRATING AS WELL AS SUFFER ACCELERATING BONE LOSS – SPLAYING. A LARGE CENTRIC PREMATURITY WILL CAUSE

THE SAME PROBLEM

2008

2016

2 WEEKS POST OCCLUSAL ADJUSTMENT

STABILITY 6 MONTHS LATER

Working Side Interference

Infers a heavy or early occlusal contact towards the back of the

mouth during an excursive movement

S Davies et al

THE MECHANICS OF OCCLUSION CAN BE COMPARED TO A NUTCRACKER

FORCES IN BRUXING CAN BE 10X THAT DURING NORMAL FUNCTION AND GO UP TO 250PSI

8X 5X 1X

Canine rise

Group function

Working-side Protrusive

CROSS-OVER IN WORKING SIDE

Dawson Academy 2009 – Why Porcelain Breaks and Chips

CORRECT CROSSOVER DISCLUSION

IT IS NOT BY CHANCE THAT THE MOST COMMON ANTERIOR AESTHETIC FRACTURE IS TO THE MAXILLARY LATERAL INCISOR. PROPER OCCLUSAL DESIGN DICTATES A SMOOTH TRANSITION TO THE INCISAL EDGE OF THE MAXILLARY CENTRALS AS THE

PATIENT MOVES BEYOND THE CANINE IN LATERAL EXCURSION. WHEN THIS POSITIONING IS OVERLOOKED, EXCESSIVE LOADS

CAN BE PLACED ON THE DISTAL OF THE LATERAL INCISORS LEADING TO FRACTURE.

ANTERIOR CROSS-OVERTHE PROGRESSION OF THE EXCURSION SHOULD PASS SMOOTHLY FROM CANINE TO LATERAL TO CENTRAL

INCISOR

Working-side ‘crossover’

Lingual cusp height adjusted to bring the anterior guidance into contact on the central incisors

Before and after occlusal adjustment by reduction of the lingual cusps

Working-side “cross-over”

Non-Working Side Interference

“Is an anterior guidance on the back teeth of the non-working side during

lateral excursions”

S Davies et al

PROTRUSIVE

There are three forms of protrusive:

• Edge to edge

• Protrusive with anterior disclusion and posterior contacts

• Protrusive with ‘crossover’

Edge to edge with posterior disclusion

Protrusive with anterior disclusion and only contacts in the posterior quadrants

Protrusive with “anterior crossover”

IS ANTERIOR CROSSOVER THE CAUSE OF LOWERFIXED RETAINERS DE-BONDING?

Cosmetic bonding

centric

Working-side Protrusive

WHAT ARE THE IMPLICATIONS OF OCCLUSION IN THE PROVISION OF

TREATMENT?

DIAGNOSIS

Working-side

Protrusive

Centric

Working-side

ENDODONTICS

“Some patients become exquisitely sensitive about the way their teeth meet to the extent that they are better at

detecting interferences than many dentists. These patients appear to have an amplified level of sensation

which can be troublesome when perceived as pain. There is often a heavy occlusal contact present - you just need to know how to look for it and adjust it. A pitfall of not recognising such a patient is unnecessary root canal

treatment”R Wassell - Occlusal pitfalls and how to avoid them – BDJ Vol 212 – No 6 – 24th

March 2102

Extract or adjust the over-erupted lower last standing molar

AVOIDING FAILING RESTORATIONS

Veneers

Minimal prep does not mean no prep

“Always consider, particularly if working on the last standing molar, whether there a premature contact in RCP- if there is, as soon as you carry out an occlusal adjustment there will be distal movement of the mandible and it is likely that

you will require further adjustment of the occlusal surface as the vertical dimension in that

area will be diminished”

Michael Wise

Take care when crowning last standing molars

“Most responses to occlusal disharmony are adaptive in nature

The possibility of converting a patient with a symptom free ‘adapting occlusion’ to one which is uncomfortable because of “high fillings” increases with the number

and complexity of the restorations -moreover the response varies between

individuals”

M Wise

Differential wear

Crown adjustment

Glazed porcelain Surface texture following adjustment with a diamond bur

Surface texture following adjustment with a diamond bur

Porcelain surface after polishing with the Meisinger porcelain polishing kit

IMPLANTS

‘Occlusal loading of a fully integrated implant can be the point of success or failure long term. Implant stability can be quickly lost if

not introduced into a healthy occlusal environment – an environment where stress is minimised by good anterior

guidance, posterior disclusion and good centric stops. Light occlusal stops on implant teeth need routine adjustment to maintain proper occlusal timing with the natural dentition.

Occlusal overload and lateral interferences will quickly show signs of bone loss around the implants’

7 Deadly Sins of Implants – Dawson Academy, Nov ‘15

”

Ortho cases

“All clinicians involved in a multidisciplinary treatment need to be

mindful of the overall duty of care to the patient – particularly the referring

dentist. An assumption that the other clinician was dealing with the problem will be viewed as a very poor defence”

Dental Protection - Annual Review 2015.

CROSS-OVER IN WORKING SIDE

Dawson Academy 2009 – Why Porcelain Breaks and Chips

CORRECT CROSSOVER DISCLUSION

IT IS NOT BY CHANCE THAT THE MOST COMMON ANTERIOR AESTHETIC FRACTURE IS TO THE MAXILLARY LATERAL INCISOR. PROPER OCCLUSAL DESIGN DICTATES A SMOOTH TRANSITION TO THE INCISAL EDGE OF THE MAXILLARY CENTRALS AS THE

PATIENT MOVES BEYOND THE CANINE IN LATERAL EXCURSION. WHEN THIS POSITIONING IS OVERLOOKED, EXCESSIVE LOADS

CAN BE PLACED ON THE DISTAL OF THE LATERAL INCISORS LEADING TO FRACTURE.

1 YEAR LATER

WHEN TO SAY NO

ACKNOWLEDGEMENTS

IMPLANT PLACEMENT – DR ANDREW DAWOODALL CLINICAL SLIDES USED ARE MY OWN IF NOT THEN

ATTRIBUTED TO LAST YEAR’S STUDENTSREFERENCES ATTRIBUTED AS MUCH AS POSSIBLE

BIBLIOGRAPHY

• Occlusion and Restorative Dentistry for the General Practitioner

Michael Wise – 10 Part BDJ series - Feb 1982 onwards

• What is Occlusion

S Davies,RMJ Gray et al – 7 Part series BDJ - Sept 2001 onwards

Dawson Academy – various short articles

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