The importance of occlusion in oral function and dysfunction
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The importance of occlusion in oral function and dysfunction. A. De Laat Copenhagen 2007. Introduction. Aim of dentistry and orthodontics in particular : maintenance and restoration of masticatory function Other goals : speech, esthetics, ….

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The importance of occlusion in oral function and dysfunction

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The importance of occlusion in oral function and dysfunction

The importance of occlusion in oral function and dysfunction

A. De Laat Copenhagen 2007



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

  • Other goals : speech, esthetics, ….

  • ? Preventive action concerning development of dysfunction (and pain)



  • Dental occlusion and normal jaw function :- mastication, forces - swallowing (and speech)- mastication and development of occlusion

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



Lundeen, Gibbs, 1972-1985

Influence of food

Influence of food

Influence of tooth morphology

Influence of tooth morphology

Influence of age

Influence of age

Influence of jaw relationship p proeschel 1988 2006

Influence of jaw relationshipP. Proeschel (1988, 2006)

  • Different chewing patterns :

Soft food tough food

Soft food – Tough food

Angle class

Angle Class

Cross bite

Cross bite

Reversed sequencing

Reversed sequencing



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

    DO exist…..But are they important …?

Bite force m bakke 2006

Bite forceM. Bakke (2006)

  • “Objective measure” of one parameter

  • Relatively simple measurement

Maximum bite force

Maximum Bite Force

  • Unilateral molars : 300-600 N

  • Premolars : 70 %

  • Front teeth : 40 %

  • Bilateral molars : 140 % - 200 % (PVDF)

  • Maximum (Eskimo’s) : 1750 N (Waugh 1937)

Hagberg 1987, Bakke et al 1989,

Ferrario et al 2004, Tortopidis et al 1998

Maximum bite force1

Maximum bite force

  • Depends on number of teeth

  • Gender difference

  • Importance of motivation and cooperation

Rugh and Solberg 1972

Maximum bite force2

Maximum bite force

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

  • Correlated to PPT (Hansdottir and Bakke 2004)

Maximum bite force3

Maximum bite force

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

  • Decreases with increasing facial height, gonial angle,… (Ingerval & Helkimo 1978, Throckmorton et al 1980, Proffitt et al 1983, Braun et al 1995)

  • No influence of tooth decay or loss of periodontal support (Miyaura et al 1999, Morita et al 2003)

Maximum bite force4

Maximum bite force

  • Dentures....

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

Malocclusion and bite force

Malocclusion and bite force

  • Negative influence of :

  • overjet on incisal MBF (Ahlberg et al 2003)

  • unilateral cross-bite (Sonnesen et al 2001)

  • open bite (Bakke & Michler 1991)



  • Occlusal contact area seems most correlated, more than malocclusion

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

Masticatory ability and performance p h buschang

Masticatory ability and performanceP.H. Buschang

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

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

Masticatory performance

Masticatory performance

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

  • Methodology : fractional sieving

  • Typical food (peanuts, carrot, bread,…) Optosil, or specially developed test-foods

Masticatory performance is influenced by

Masticatory performance is influenced by :

  • Number of teeth/occluding units (but subjects with missing teeth do not chew longer…)( Helkimo et al 1978, Yurkstas et al 1965, Henrikson et al 1998)

  • Patients with dentures increase the number of chewing strokes and wait longer to swallow (? Corrected for age )

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

Mp and malocclusion

MP and malocclusion

  • Less potent effect than mutilated dentition

  • In cross-sectional studie, MP of Class III patients is up to 60 % lower (English et al 2002, Lundberg et al 1974, Zhou and Fu 1995). MP of Class II is 30 to 40 % lower (Henrikson et al 1998) but Median Particle Size (MPS) was not significantly different (Toro et al 2006)

Mp and malocclusion1

MP and malocclusion

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

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

Mp and digestion

MP and digestion

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

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

Mastication and developing occlusion

Mastication and developing occlusion

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

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



  • Malocclusion influences the chewing cycle

  • Number of occlusal contacts and units influences the maximum bite force

  • Class II and III patients have a lower masticatory performancebut….

  • Probably not of clinical significance in non-compromised patients

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