Concept of Normal Occlusion

8/4/2019 Concept of Normal Occlusion

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CONCEPT OF

NORMAL OCCLUSION



INTRODUCTION

• The study and practice of most branchesof dentistry should be based on a strongfoundation of knowledge of occlusion.

• The Pedodontist should know whatconstitutes normal occlusion in order to beable to recognize abnormal occlusion.

• A balanced, stable, healthy andesthetically attractive occlusion is alsoconceivable normal even if minor rotationare present.



• And yet, what may be abnormal for oneage may be normal for another.

• The curve of spee, compensatory curve,cusp height and facial relation of eachtooth to its antagonist and othercharacteristics of occlusion may all vary

within a broad range and still be normal.



• Good examples of the time-linked nature of normally are such transient malocclusion, ascrowding during, eruption of incisors, the ‘uglyduckling’ flaring of maxillary lateral incisors, the

Class II first molar relationship tendencies beforeloss of second deciduous molars.

• “clusion” means closing and “oc” means up thus “occlusion” is closing up.



DEVELOPMENT OF CONCEPT OFOCCLUSION

• The development of the idea of occlusion can betraced through fiction and hypothesis to fact.

• The FICTIONAL APPROACH, in a philosophicalsense, was convenient arrangement of series of observed and thoughts more or, less logicallyarrange.

• The HYPOTHETICAL ATTACK on the problem of occlusion was based on a provisional acceptanceof certain logical entities. This is just theopposite of fiction.



The development of concept of

occlusion thus can be divided intothree periods:

• The fictional period, prior to 1900,

• The hypothetical period, from 1900 to 1930,

• The factual period, from 1930 to the presentdevelopment of concept of occlusion



Classification of occlusion

• Based on mandibularposition.

• Based on relationshipof 1st permanentmolar.

• Based on organizationof occlusion.

• Based on pattern of occlusion.



Based on Mandibular Position

1. Centric Occlusion

2. Eccentric Occlusion



1. Centric Occlusion• It is the occlusion of the teeth when mandible is

in centric relation.

• Centric relation has been defined as the maxillo-mandibular relationship in which condyles

articulate with the thinnest avascular position of their respective discs with complex in theanterosuperior position against shape of articulareminence.

• This position is independent of tooth contact andis clinically identify when mandible is directedanterirly and superiorly.



2 Eccentric Occlusion

• It is defined as the occlusion other thancentric occlusion

• It includes : – Lateral occlusion – Protruded occlusion

– Retrusive Occlusion



Lateral Occlusion

• It is defined as the contact betweenopposing teeth when the mandible is

moved either right or left.



Protruded Occlusion

• It defined as the occlusion of the teethwhen the mandible is protruded.

• It is anterior to centric occlusion.



Retrusive Occlusion

• Occlusion of the teeth when the mandibleis retruded.

• It is posterior to centric occlusion.



Based on relationship of 1stpermanent molar

• Angle’s classification : 3 types

1. Class 1

2. Class 2 – Div 1

– Div 2

3. Class 3



Class 1

• Mesio – Buccalcusp of maxillaryfirst permanent

molar occludes inthe buccal grooveof mandibular first

permanent molar.



Class 2

• Disto – Buccal cusp of the maxillary firstpermanent molar occludes in the buccalgroove of the lower first permanent molar.



Class 2 Div 1

• Proclined upper incisors with a resultantincrease in overjet.

• A deep incisor overbite can occur inanterior region.



Class 2 Div 2

• Presence of linguallyinclined upper centralincisors and labially

tipped upper lateralincisors overlap thecental incisors.

• Patient exhibits a

deep anterioroverbite.



Class 2 Subdivision

• When a class 2 molar relation exsists onone side and a class 1 relation on the

other side, it is referred as class 2subdivision.



Class 3

• Mesio – Buccal cusp of the maxillary firstpermanent molar occluding in theinterdental space between mandibular

first and second molar.



Based on the organization of occlusion

A. Canine guide or protected occlusion

• During lateral movements, only working

side canine comes into contact with theother. This results in disocclusion of allposterior teeth.

• The tip or the buccal incline of the lowercanine is seen to slide along with palatalsurface of upper canine.



B. Mutually protected occlusion

• The posterior teethprevent excessivecontact of the anteriorteeth in maximum

intercuspation.• The anterior teeth

disengage the

posterior teeth in allmandibular extrusivemovement.



C. Group function occlusion• It is define as the

multiple contactrelationship betweenthe maxillary andmandibular teeth, in

lateral movements of the working side.

• By simultaneous

contacts of severalteeth is achieved andthey act as a group todistribute occlusal

forces.



Based on pattern of occlusionA. Cusp to embrasure/

marginal ridgeocclusion

– This pattern of occlusion shows fitting

of one cusp of a teethinto a fossa and fittingof another cusp of same tooth into

embrasure area of two teeth.

– This is tooth – to –two – teeth relation.



Cusp to fossa occlusion

• This pattern of occlusion shows, all cuspof a tooth fitting into fossa only oneopposing teeth.

• This is a tooth – to – one – tooth relation.





Key II - Crown angulation (Tip)

• The gingival portion of the long axis of theall crowns was more distal than the incisalportion.



Key III Crown incl ination

• crown inclination refers to the labiolingual orbuccolingual inclination of long axis of the crown,not to the inclination of long axis of entire tooth.



Crown inclination isexpressed in plus or minus

degrees.• A plus reading is given if

the gingival portion of the

crown is lingual to theincisal portion.

• A minus reading isrecorded when the

gingival portion of thecrown is labial to theincisal portion.



a) Anterior crown inclination:

•) Properly inclinedanterior crownscontribute to normal

overbite and posteriorocclusion.

•) Inclination should be

positive in this categaryof teeth.



b) Posterior crown inclination (upper) :• A minus crown inclination should exist in

each crown from the upper caninethrough the upper second premolar .

• A slightly more negative crown inclinationexists in the upper first and secondmolars.



c) posterior crown inclination (lower) :

• A progressively greater minus crowninclination exists from the lower caninethrough lower second molar.



Key IV – Rotations

• The fourth key to normal occlusion is thatthe teeth should be free of undesirablerotations.



Key V – Tight contacts

• The fifth key is that the contact pointsshould be tight (no spaces).



Key VI – Occlusal plane or curve of spee

• The planes of occlusion found on normalmodels ranged crown flat to slight curves of Spee.

• Even though not all of the non-orthodonticnormal had flat planes of occlusion, flat planeshould be a treatment goal as a form of over-

treatment. There is a natural tendency for curve of Spee to deepen with time.

• Intercuspation of teeth is best when the planeof occlusion is relatively flat.



CONCLUSION

• The primary aim of understanding of occlusion would be to differentiatebetween a developing normal occlusion

and a potential malocclusion.• This gives a sound understanding of occlusion & dental development and the

ability to recognize the rate and directionof facial and dental growth.



• The pedodontist should know about the goal

of treatment i.e. where to stop the treatment.For this a basic knowledge of normal occlusionshould known to us.

• Normal occlusion is not a rigid or static

relationship.• What is normal interdigitation in deciduousand mixed dentition is abnormal in permanentdentition and vice versa.

• The study of normal occlusion can be used tomake a preliminary assessment of child’socclusal status.



• The data can be used to advise the parent

of the child’s growth potential and possibledevelopment problems.

• Successful treatment involves manydisciplines, not all of which are alwayswithin our control. Achieving the finaldesired occlusion is the purpose of attending to the six keys to normal

occlusion.



THANK YOU

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Concept of Normal Occlusion