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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 A. De Laat Copenhagen 2007
Introduction • 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)
Outline • 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
Mastication Lundeen, Gibbs, 1972-1985
Influence of jaw relationshipP. Proeschel (1988, 2006) • Different chewing patterns :
Conclusion • Differences between groups with different (mal)occlusions or tooth morphology DO exist…..But are they important …?
Bite forceM. Bakke (2006) • “Objective measure” of one parameter • Relatively simple measurement
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 force • Depends on number of teeth • Gender difference • Importance of motivation and cooperation Rugh and Solberg 1972
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 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 force • Dentures.... ..and implant-support helps… (Bakke et al 2002, Van Kampen et al 2002)
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)
Conclusions • 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 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 • 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 : • 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 • 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 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 • 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 • 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)
CONCLUSIONS • 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