The importance of The importance of occlusion in oral function occlusion in oral function

and dysfunctionand dysfunction

A. De Laat A. De Laat Copenhagen 2007Copenhagen 2007

IntroductionIntroduction

Aim of dentistry and orthodontics in Aim of dentistry and orthodontics in particular : maintenance and restoration of particular : maintenance and restoration of masticatory functionmasticatory function

Other goals : speech, esthetics, ….Other goals : speech, esthetics, …. ? Preventive action concerning ? Preventive action concerning

development of dysfunction (and pain)development of dysfunction (and pain)

OutlineOutline

Dental occlusion and normal jaw function :Dental occlusion and normal jaw function :- - masticationmastication, forces , forces - - swallowingswallowing (and (and speech)speech)- mastication and development of - mastication and development of occlusionocclusion

(Mal)occlusion and Temporomandibular (Mal)occlusion and Temporomandibular Disorders Disorders - etiological role ?- etiological role ?- management of TMD- management of TMD- other orofacial pains- other orofacial pains

MasticationMastication

Lundeen, Gibbs, 1972-1985

Influence of foodInfluence of food

Influence of tooth morphologyInfluence of tooth morphology

Influence of ageInfluence of age

Influence of jaw relationshipInfluence of jaw relationshipP. Proeschel (1988, 2006)P. Proeschel (1988, 2006)

Different chewing patterns :Different chewing patterns :

Soft food – Tough foodSoft food – Tough food

Angle ClassAngle Class

Cross biteCross bite

Reversed sequencingReversed sequencing

ConclusionConclusion

Differences between groups with different Differences between groups with different (mal)occlusions or tooth morphology(mal)occlusions or tooth morphology

DO exist…..DO exist…..

But are they important …?But are they important …?

Bite forceBite forceM. Bakke (2006)M. Bakke (2006)

““Objective measure” of one parameterObjective measure” of one parameter Relatively simple measurementRelatively simple measurement

Maximum Bite ForceMaximum Bite Force

Unilateral molars : 300-600 NUnilateral molars : 300-600 N Premolars : 70 %Premolars : 70 % Front teeth : 40 %Front teeth : 40 % Bilateral molars : 140 % - 200 % (PVDF)Bilateral molars : 140 % - 200 % (PVDF) Maximum (Eskimo’s) : 1750 N Maximum (Eskimo’s) : 1750 N (Waugh 1937)(Waugh 1937)

Hagberg 1987, Bakke et al 1989, Ferrario et al 2004, Tortopidis et al 1998

Maximum bite forceMaximum bite force

Depends on number of teethDepends on number of teeth Gender differenceGender difference Importance of motivation and cooperation Importance of motivation and cooperation

Rugh and Solberg 1972

Maximum bite forceMaximum bite force

Influence of pain : arthritis or TMD results Influence of pain : arthritis or TMD results in decrease of 40 % in decrease of 40 % (Wenneberg et al 1995, Stohler (Wenneberg et al 1995, Stohler 1999)1999)

Correlated to PPT Correlated to PPT (Hansdottir and Bakke 2004)(Hansdottir and Bakke 2004)

Maximum bite forceMaximum bite force

Influence of age (constant from 20-50 y, Influence of age (constant from 20-50 y, decreases later, decreases later, Bakke et al 1990Bakke et al 1990))

Decreases with increasing facial height, Decreases with increasing facial height, gonial angle,… (gonial angle,… (Ingerval & Helkimo 1978, Throckmorton Ingerval & Helkimo 1978, Throckmorton

et al 1980, Proffitt et al 1983, Braun et al 1995et al 1980, Proffitt et al 1983, Braun et al 1995)) No influence of tooth decay or loss of No influence of tooth decay or loss of

periodontal support (periodontal support (Miyaura et al 1999, Morita et al Miyaura et al 1999, Morita et al

20032003))

Maximum bite forceMaximum bite force

Dentures....Dentures....

..and implant-support helps… (Bakke et al 2002, Van Kampen et al 2002)

Malocclusion and bite forceMalocclusion and bite force

Negative influence of :Negative influence of :- overjet on incisal MBF overjet on incisal MBF (Ahlberg et al 2003)(Ahlberg et al 2003)

- unilateral cross-bite unilateral cross-bite (Sonnesen et al 2001)(Sonnesen et al 2001)

- open bite open bite (Bakke & Michler 1991)(Bakke & Michler 1991)

ConclusionsConclusions

Occlusal contact area seems most Occlusal contact area seems most correlated, more than malocclusioncorrelated, more than malocclusion

But…does it matter,sinceBut…does it matter,since- only 10-20 % of variation explained- only 10-20 % of variation explained(while e.g. thickness of masseter explains 55 %...)(while e.g. thickness of masseter explains 55 %...) - normal chewing forces are only 15-30 % - normal chewing forces are only 15-30 % of MBF….of MBF….

Masticatory ability and performanceMasticatory ability and performanceP.H. BuschangP.H. Buschang

Anatomical (occlusal contact area, Anatomical (occlusal contact area, malocclusion …); physiological (muscle malocclusion …); physiological (muscle strength, training, gender,…) and strength, training, gender,…) and psychological components interplay in psychological components interplay in mastication, and deficiencies in one part mastication, and deficiencies in one part can be compensated for by otherscan be compensated for by others

““Masticatory performance” is an objective Masticatory performance” is an objective measure, directly linked to food measure, directly linked to food breakdown, nutrition, digestionbreakdown, nutrition, digestion

Masticatory performanceMasticatory performance

Particle size distribution of (test-)food, Particle size distribution of (test-)food, chewed a standard number of cycleschewed a standard number of cycles

Methodology : fractional sievingMethodology : fractional sieving Typical food (peanuts, carrot, bread,…) Typical food (peanuts, carrot, bread,…)

Optosil, or specially developed test-foodsOptosil, or specially developed test-foods

Masticatory performance is Masticatory performance is influenced by :influenced by :

Number of teeth/occluding units (but Number of teeth/occluding units (but subjects with missing teeth do not chew subjects with missing teeth do not chew longer…)( longer…)( Helkimo et al 1978, Yurkstas et al 1965, Henrikson Helkimo et al 1978, Yurkstas et al 1965, Henrikson

et al 1998et al 1998)) Patients with dentures increase the Patients with dentures increase the

number of chewing strokes and wait number of chewing strokes and wait longer to swallow (? Corrected for age )longer to swallow (? Corrected for age )

Mixed dentition : increase in early, Mixed dentition : increase in early, decrease in late phasedecrease in late phase

MP and malocclusionMP and malocclusion

Less potent effect than mutilated dentitionLess potent effect than mutilated dentition In cross-sectional studie, MP of Class III In cross-sectional studie, MP of Class III

patients is up to 60 % lower (patients is up to 60 % lower (English et al 2002, English et al 2002,

Lundberg et al 1974, Zhou and Fu 1995Lundberg et al 1974, Zhou and Fu 1995). MP of Class II ). MP of Class II is 30 to 40 % lower (is 30 to 40 % lower (Henrikson et al 1998Henrikson et al 1998) but ) but Median Particle Size (MPS) was not Median Particle Size (MPS) was not significantly different (significantly different (Toro et al 2006Toro et al 2006) )

MP and malocclusionMP and malocclusion

After a predetermined number of chewing After a predetermined number of chewing cycles (20,30,40) , the Median Particle cycles (20,30,40) , the Median Particle Size is larger in subjects with ICON (index Size is larger in subjects with ICON (index for complexity, outcome,need) < 43 than for complexity, outcome,need) < 43 than > 43> 43

but no differences in particle distribution but no differences in particle distribution or masticatory frequency (or masticatory frequency (Ngom 2007Ngom 2007) )

MP and digestionMP and digestion

Animal experiments clearly indicate Animal experiments clearly indicate relation between food particle size and relation between food particle size and digestion (digestion (Gyimesi et al 1972Gyimesi et al 1972))

In man, also incompletely chewed food is In man, also incompletely chewed food is digested. In elder persons, MP has been digested. In elder persons, MP has been linked to GI-problems : 49 % of patients linked to GI-problems : 49 % of patients without posterior teeth have gastritis vs without posterior teeth have gastritis vs 6 % when no teeth are missing (6 % when no teeth are missing (Mumma 1970Mumma 1970))

Mastication and developing Mastication and developing occlusionocclusion

Over the centuries, malocclusion seems to Over the centuries, malocclusion seems to have increased 10-fold and modern life-have increased 10-fold and modern life-style and nutrition have been suggested style and nutrition have been suggested as cause (as cause (Corrucini 1984, Varrela 1990,1992Corrucini 1984, Varrela 1990,1992), even ), even more than genetics (more than genetics (Townsend et al 1998Townsend et al 1998) )

Nutrition influences elevator muscle Nutrition influences elevator muscle development and muscle function development and muscle function influences transverse and vertical facial influences transverse and vertical facial dimensions (dimensions (Kiliaridis 2006Kiliaridis 2006))

CONCLUSIONSCONCLUSIONS

Malocclusion influences the chewing cycleMalocclusion influences the chewing cycle Number of occlusal contacts and units Number of occlusal contacts and units

influences the maximum bite force influences the maximum bite force Class II and III patients have a lower Class II and III patients have a lower

masticatory performancemasticatory performancebut….but….

Probably not of Probably not of clinicalclinical significance in non- significance in non-compromised patients compromised patients