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OCCLUSION (PART III) INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.c om
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Occlusion Part(III) / orthodontic courses by Indian dental academy

Apr 27, 2017

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  • OCCLUSION (PART III) INDIAN DENTAL ACADEMY

    Leader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com

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  • ContentsIntroductionPosterior controlling factorsAnterior controlling factorsUnderstanding the controlling factors

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  • Vertical determinants of occlusal morphology (on cusp height)Horizontal determinants of occlusal morphology (on ridge and groove direction) Summary References

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  • IntroductionThe occlusal anatomy of the teeth must function in harmony with the structures controlling the movement patterns of the mandible.To maintain harmony of the occlusal condition, the posterior teeth must pass close to but must not contact their opposing teeth during mandibular movement

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  • Posterior controlling factorswww.indiandentalacademy.com

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  • The angle at which the condyle moves away from horizontal reference plane is referred to as the condylar guidance angle.

    Two TMJs posterior controlling factors

    Fixed factors

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  • Anterior controlling factors

    Vertical overlap and horizontal overlapVariable factor (altered by dental procedures)

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  • Understanding the controlling factorsIf the criteria for optimum functional occlusion has to be fulfilled, the morphologic characteristics of each posterior tooth must be in harmony with those of its opposing tooth or teeth during all eccentric mandibular movements.The relationship of a posterior tooth to the controlling factors influences the precise movement of that tooth.

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  • Therefore, the significance of the anterior and condylar guidances lies in how they influence posterior tooth shape.www.indiandentalacademy.com

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  • Occlusal surface of the posterior teeth can be affected in 2 mannersHeightWidth Factors that influence the heights of cusps and depths of fossae are the vertical determinants of the occlusal morphologyFactors that influence the direction of ridges and grooves on the occlusal surfaces are considered the horizontal determinants of the occlusal morphology

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  • Vertical determinants of occlusal morphology (on cusp height) a) Effect of condylar guidance b) Effect of anterior guidance c) Effect of plane of occlusion d) Effect of curve of Spee e) Effect of mandibular lateral translation movement www.indiandentalacademy.com

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  • a) Effect of condylar guidancewww.indiandentalacademy.com

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  • b) Effect of anterior guidance

    It is a function of the relationship between the maxillary & mandibular anterior teeth.

    Anterior guidance = Overjet X overbite

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  • c) Effect of plane of occlusion

    It is an imaginary line extending from cusp tip of mandibular canine to distobuccal cusp of lower second molarRelationship of this plane to the angle of articular eminence influences the steepness of the cusps.

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  • As the plane of occlusion becomes more nearly parallel to the angle of the articular eminence, the posterior cusps must be made shorter. www.indiandentalacademy.com

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  • d) Effect of curve of Spee 3 components affecting the cusp height are: Length of the radius of the curve Degree of curvature of the curve of Spee Orientation of curve of Spee

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  • Length of the radius of the curvewww.indiandentalacademy.com

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  • Degree of curvature of the curve of Speewww.indiandentalacademy.com

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  • Orientation of curve of Speewww.indiandentalacademy.com

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  • e) Effect of mandibular lateral translation movement

    Bennett movement- A bodily side shift of the mandible that occurs during lateral movements.www.indiandentalacademy.com

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  • The degree of medial movement of orbiting condyle depends on two factors :

    Morphology of medial wall of the fossa.Inner horizontal portion of the Temporomandibular ligament (which attaches to the lateral pole of the rotating condyle)

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  • Lateral translation movement has 3 attributesAmountDirectionTiming Amount and Timing are dependent on medial wall of fossa and TM ligament.Direction depends on the direction taken by the rotating condyle.

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  • Effect of amount of lateral translation movement on cusp heightGreater the amount of lateral translation movement, shorter is the posterior cuspwww.indiandentalacademy.com

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  • Effect of the direction of lateral translation movement on cusp height

    Determined by the morphology and ligamentous attachments of the TMJ undergoing rotation.The movement occurs within a 60 degree cone whose apex is located at the axis of rotation.

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  • Effect of timing of lateral translation movement on cusp heightDependent on the medial wall of fossa and TM ligament.Immediate side shift when the lateral translation movement occurs earlyProgressive side shift if movement occurs in conjunction with an eccentric movement

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  • Horizontal determinants of occlusal morphology Influences the direction of ridges and grooves on the occlusal surfacesEach centric cusp tip generates both laterotrusive and mediotrusive pathways across its opposing toothEach pathway represents a portion of the arc formed by the cusp rotating around the rotating condyle

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  • Horizontal determinants of occlusal morphology (on ridge and groove direction)Effect of distance from rotating condyleEffect of distance from mid-Sagittal planeEffect of distance from rotating condyle and from mid-Sagittal planeEffect of mandibular lateral translation movementEffect of inter-condylar distance

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  • Effect of distance from rotating condyle

    Greater the distance wider the anglewww.indiandentalacademy.com

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  • b) Effect of distance from mid-Sagittal planeMore the distance wider the anglewww.indiandentalacademy.com

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  • c) Effect of distance from rotating condyle and from mid-Sagittal planeThe combination of the two positional relationships is what determines the exact pathways of the centric cusp tipsBecause of the curvature of the dental arch; as the distance of tooth from rotating condyle increases distance from midsagittal plane decreases, but distance from rotating condyles increases FASTER than decrease in distance from midsagittal plane.

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  • Therefore, the teeth toward the anterior region (e.g. premolars) have larger angles than posterior teeth (e.g. molars).www.indiandentalacademy.com

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  • d) Effect of mandibular lateral translation movementinfluences the directions of ridges and grooves

    Movement depends on 2 factors:AmountDirection

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  • Effect of amount of lateral translation movement on ridge and groove directionwww.indiandentalacademy.com

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  • Effect of direction of lateral translation movement on ridge and groove directionwww.indiandentalacademy.com

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  • e) Effect of inter-condylar distance As inter condylar distance increases distance between the condyle and the tooth increases wider angles

    (in a given arch configuration) As inter condylar distance increases the tooth is placed nearer the mid-sagittal plane relative to the rotating condyle-midsagittal plane distance decrease in the angle generated

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  • Increase in inter-condylar distance decrease in angle between mediotrusive and laterotrusive pathwayswww.indiandentalacademy.com

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  • Summary Vertical determinants of occlusal morphology (on cusp height and fossa depth)Horizontal determinants of occlusal morphology (on ridge and groove direction)

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    Factor Condition Effect Condylar guidanceSteeper Taller Anterior guidanceMore overbiteMore OverjetTaller Shorter Plane of occlusionMore parallelShorter Curve of Spee More acute Shorter Lateral translation Greater movementMore superior Greater immediate shiftShorter ShorterShorter

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    Factor Condition Effect Distance from rotating condyleGreater Wider the angleDistance from midsagittal planeGreaterWider the angle

    Lateral translationGreaterWider the angle

    Intercondylar distanceGreaterSmaller the angle

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  • 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

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  • Santos JD. Occlusion Principles and Concepts, ed. 2nd, 1999; Ishiyaku EuroAmerica, Inc. U.S.A. Shillingburg HT. Fundamentals of Fixed Prosthodontics, ed.3rd, 1997;Quintessence

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  • Thank you

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