The importance of occlusion in oral function and

The importance of occlusion in oral function and dysfunction A. De Laat Copenhagen 2007

Introduction Ø Aim of dentistry and orthodontics in particular : maintenance and restoration of masticatory function Ø Other goals : speech, esthetics, …. Ø ? Preventive action concerning development of dysfunction (and pain)

Outline Ø Dental occlusion and normal jaw function : - mastication, forces - swallowing (and speech) - mastication and development of occlusion Ø (Mal)occlusion and Temporomandibular Disorders - etiological role ? - management of TMD - other orofacial pains

Mastication Lundeen, Gibbs, 1972 -1985

Influence of food

Influence of tooth morphology

Influence of age

Influence of jaw relationship P. Proeschel (1988, 2006) Ø Different chewing patterns :

Soft food – Tough food

Angle Class

Cross bite

Reversed sequencing

Conclusion Ø Differences between groups with different (mal)occlusions or tooth morphology DO exist…. . But are they important …?

Bite force M. Bakke (2006) Ø “Objective measure” of one parameter Ø Relatively simple measurement

Maximum Bite Force Ø Unilateral molars : 300 -600 N Ø Premolars : 70 % Ø Front teeth : 40 % Ø Bilateral molars : 140 % - 200 % (PVDF) Ø Maximum (Eskimo’s) : 1750 N (Waugh 1937) Hagberg 1987, Bakke et al 1989, Ferrario et al 2004, Tortopidis et al 1998

Maximum bite force Ø Depends on number of teeth Ø Gender difference Ø Importance of motivation and cooperation Rugh and Solberg 1972

Maximum bite force Ø Influence of pain : arthritis or TMD results in decrease of 40 % (Wenneberg et al 1995, Stohler 1999) Ø Correlated to PPT (Hansdottir and Bakke 2004)

Maximum bite force Ø Influence of age (constant from 20 -50 y, decreases later, Bakke et al 1990) Ø Decreases with increasing facial height, gonial angle, … (Ingerval & Helkimo 1978, Throckmorton et al 1980, Proffitt et al 1983, Braun et al 1995) Ø No influence of tooth decay or loss of periodontal support (Miyaura et al 1999, Morita et al 2003)

Maximum bite force Ø Dentures. . . and implant-support helps… (Bakke et al 2002, Van Kampen et al 2002)

Malocclusion and bite force Ø Negative influence of : overjet on incisal MBF (Ahlberg et al 2003) - unilateral cross-bite (Sonnesen et al 2001) - open bite (Bakke & Michler 1991) -

Conclusions Ø Occlusal contact area seems most correlated, more than malocclusion Ø 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 Ø 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 Ø “Masticatory performance” is an objective measure, directly linked to food breakdown, nutrition, digestion

Masticatory performance Ø Particle size distribution of (test-)food, chewed a standard number of cycles Ø Methodology : fractional sieving Ø Typical food (peanuts, carrot, bread, …) Optosil, or specially developed test-foods

Masticatory performance is influenced by : Ø 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) Ø Patients with dentures increase the number of chewing strokes and wait longer to swallow (? Corrected for age ) Ø Mixed dentition : increase in early, decrease in late phase

MP and malocclusion Ø Less potent effect than mutilated dentition Ø 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 malocclusion Ø 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 Ø but no differences in particle distribution or masticatory frequency (Ngom 2007)

MP and digestion Ø Animal experiments clearly indicate relation between food particle size and digestion (Gyimesi et al 1972) Ø 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 Ø Over the centuries, malocclusion seems to have increased 10 -fold and modern lifestyle and nutrition have been suggested as cause (Corrucini 1984, Varrela 1990, 1992), even more than genetics (Townsend et al 1998) Ø Nutrition influences elevator muscle development and muscle function influences transverse and vertical facial dimensions (Kiliaridis 2006)

CONCLUSIONS Ø Malocclusion influences the chewing cycle Ø Number of occlusal contacts and units influences the maximum bite force Ø Class II and III patients have a lower masticatory performance but…. Ø Probably not of clinical significance in noncompromised patients