Occlusion / orthodontic courses by Indian dental academy

OCCLUSION

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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CONTENTS Introduction History Alignment and occlusion of the dentition -Factors and forces that determine tooth position -Intra-arch tooth alignment -Inter-arch tooth alignment -Occlusal contacts during mandibular movements Summary References www.indiandentalacademy.com

INTRODUCTIONAccording to Glossary of Prosthodontic Terms:

“Occlusion is the act or process of closure or of being closed or shut off”Ramfjord and Ash: Occlusion = Contacts between teeth“Multifactorial functional relationship between the teeth and other components of the masticatory system as well as with other areas of the head and neck that directly or indirectly relate to function, parafunction or dysfunction of the masticatory system.”www.indiandentalacademy.com

Masticatory system

Teeth

Periodontium Articulatory system TMJ

Muscles Occlusionwww.indiandentalacademy.com

HISTORYDevelopment of concept of occlusion--Three periods:1. Fictional period (prior to 1900)2. Hypothetical period (1900-1930)3. Factual period (1930 to present)


1.Fictional period:Fuller, Clark and Imrie-Antagonism,meeting or gliding of teeth.Kingsley(1880)– “Norm”Talbot’s-(1903)Irregularities of teeth and their treatment.

2.Hypothetical period:Edward H. Angle(1899)- “Old Glory” and “Key to Occlusion”.Matthew Cryer and Calvin Case-Occlusion referred to the closure of the teeth one upon the other.


Bennett (1908)-Functional analysis or dynamic approach to occlusion.Turner(1903)-Concept of physiologic rest.Lister and Simon(1922)-Related teeth to the rest of the face and cranium.Milo Hellman-Racial variations in normal occlusions.

3.Factual period:Difference between static and dynamic concepts of occlusion.

Broadbent and Planer-(1930) Occlusion=Interdigitation of teeth + Status of controlling musculature and functional factors.www.indiandentalacademy.com

Alignment and occlusion of the dentition:Tooth positions are determined by various

controlling factors such as:

1. Factors and forces that determine tooth position. 2. Intra-arch tooth alignment.3. Inter-arch tooth alignment.


1.Factors and forces that determine tooth position.(a)Surrounding musculature:Labial to teeth are lips,cheeks-lingually directed forcesTongue-labially and bucally directed forces.


Oral habits-biting on pipe,musical instruments.

(b)Proximal surfaces:Proximal contact wear-mesial drift( because of functional response of alveolar bone and gingival fibres)

(c)Occlusal contacts: prevents extrusion.

Abnormal muscular pattern-Tongue thrust and visceral swallow.


2.Intra-arch tooth alignment: -Relationship of the teeth to each other within dental arch.

Plane of occlusion is not flat.www.indiandentalacademy.com

The curvature of the occlusal plane is due to the varying degrees of inclination of teeth in the dental arches.



THE OCCLUSAL SURFACE

The area of tooth between buccal and lingual cusp tips is called the occlusal table.


(a) Inner inclines(b) Outer inclines


3.Inter-arch tooth alignment: -Relationship of the teeth in one arch to those in the other.

Arch length- Maxilla – 128 mm Mandible – 126 mm Arch width: Distance across arch.


The buccal cusp of mandibular posterior teeth and lingual cusp of maxillary posterior teeth occlude with the opposing central fossa areas – Supporting cusps.


The centric cusp are broad and rounded.

The The buccal cusp of maxillary posterior teeth and lingual cusp of mandibular posterior teeth– Guiding or non-centric cusps (sharp, with definite tips)www.indiandentalacademy.com

Functional outer aspect:Present only on outer aspect of centric cusp.This area assists in shearing of food therefore non-centric cusps- shearing cusps.

Non-centric cusps provide stability to the mandible in maximum intercuspal position.Guiding cusps.


BUCCOLINGUAL OCCLUSAL CONTACT REALATIONSHIP


Proximal contact areas located slightly buccal to the C-F Line-Greater lingual embrasure area-- Major spillway.



MESIO-DISTAL OCCLUSAL CONTACT REALATIONSHIP

These cusp typically contacts 1. Central fossa areas: The actual contact point

are called centric stops, holding contacts, as they serve to hold the teeth in a stable position.


2.Marginal ridge and embrasure areas: Marginal ridge is slightly convex areas, therefore the type of contact is cusp tip contacting a flat surface.


COMMON OCCLUSAL RELATIONSHIPS OF POSTERIOR TEETH

CLASS-I


COMMON OCCLUSAL RELATIONSHIPS OF ANTERIOR TEETH

Maxillary anterior teeth-labial to mandibular anterior teeth.Inclined labially (12º-28º).Normally incisal edges of lower incisors contacts lingual surfaces of upper incisors in the lingual fossae which is 4mm gingival to incisal edges.


In normal occlusion, contacts on the anterior teeth in the intercuspal position are much lighter than on the posterior teeth.Purpose of the anterior teeth-guide the mandible through various movements.

Anterior guidance- It is the anterior tooth contact that provide guidance to the mandible. -determined by exact position and relationship of the anterior teeth which can be examined both horizontally and vertically.


Overjet:distance between the labial incisal edge of maxillary incisor and labial surface of mandibular incisor.

Overbite:distance between the incisal edges of the opposing anterior teeth.www.indiandentalacademy.com

OCCLUSAL CONTACTS DURING MANDIBULAR MOVEMENTS

The TMJ’s and the associated muscles allows the mandible to move in all three planes-(Sagittal,Frontal and horizontal) which ultimately influences contact patterns on the occlusal surfaces of the posterior teeth.Eccentric- any movement of the mandible from the intercuspal position that results in tooth contact.Three types:Protrusive, Laterotrusive, Retrusive. www.indiandentalacademy.com

PROTRUSIVE


LATEROTRUSIVE


RETRUSIVE


SUMMARY



REFERENCES Occlusion series in BDJ, 2001;191:6-7 Okeson JP. Management of

Temporomandibular Disorders and Occlusion, ed. 4th, 1998; Mosby

Ash MM and Ramfjord S. Occlusion, ed. 4th, 1966; WB Saunders Company, Michigan

Santos JD. Occlusion Principles and Concepts, ed. 2nd, 1999; Ishiyaku EuroAmerica, Inc. U.S.A.

Shillingburg HT. Fundamentals of Fixed Prosthodontics, ed.3rd, 1997;Quintessencewww.indiandentalacademy.com

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Occlusion / orthodontic courses by Indian dental academy

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