BDS [Orthodontics] course

1. OCCLUSION
PROF (Dr.) SAIBEL FARISHTA

2. DEFINITION BY ‘ANGLE’ -
‘IT IS THE NORMAL RELATION OF THE OCCLUSAL
INCLINED PLANES OF THE TEETH, WHEN THE JAWS ARE
CLOSED’
OCCLUSION IS A COMPLEX PHENOMENON INVOLVING
THE TEETH, PERIODONTAL LIGAMENT, THE JAWS, TMJ,
MUSCLES AND THE NERVOUS SYSTEM.

3. TYPES OF CUSPS
THE HUMAN POSTERIOR TEETH CONSTITUTE TWO TYPES
OF CUSPS –
1. THE CENTRIC HOLDING CUSPS
2. THE NON - SUPPORTING CUSPS
1. THE CENTRIC HOLDING CUSPS –
THE FACIAL CUSPS OF MANDIBULAR AND PALATAL CUSPS
OF MAXILLARY POSTERIOR TEETH ARE CALLED AS THE
CENTRIC HOLDING CUSPS. THEY OCCLUDE INTO THE
CENTRAL FOSSA AND THE MARGINAL RIDGES OF
OPPOSING TEETH. THEY ARE ALSO CALLED AS THE
STAMP CUSPS.

4. 2. NON-SUPPORTING CUSPS –
THE MAXILLARY BUCCAL AND MANDIBULAR LINGUAL
CUSPS ARE CALLED NON - SUPPORTING CUSPS. THEY
CONTACT AND GUIDE THE MANDIBLE DURING LATERAL
EXCURSIONS AND SHEAR FOOD DURING MASTICATION,
THEREFORE THEY ARE ALSO KNOWN AS SHEARING OR
GUIDING CUSPS.
ARRANGEMENT OF TEETH IN HUMANS -
I. CUSP - FOSSA OCCLUSION
II. CUSP - EMBRASSURE OCCLUSION

5. I. CUSP - FOSSA OCCLUSION –
IN THIS TYPE OF OCCLUSION, THE STAMP CUSP OF ONE
TOOTH OCCLUDES IN A SINGLE FOSSA OF A SINGLE
OPPONENT. THE UPPER STAMP CUSPS FIT INTO ALL,
EXCEPT THE MESIAL FOSSA OF THE LOWER TEETH.
WHILE THE LOWER STAMP CUSPS FIT INTO ALL THE
UPPER FOSSA EXCEPT THE DISTAL ONES OF BICUSPIDS.
THIS IS CALLED CUSP – FOSSA OCCLUSION OR A TOOTH
TO TOOTH ARRANGEMENT.
II. CUSP - EMBRASSURE OCCLUSION –
IN THIS TYPE OF OCCLUSION, EACH TOOTH OCCLUDES
WITH TWO OPPOSING TEETH. THIS ARRANGEMENT IS
CALLED CUSP – EMBRASSURE CONTACT OR TOOTH TO
TEETH OCCLUSION.

6. CUSP – FOSSA AND CUSP – EMBRASSURE OCCLUSION

7. IMAGINARY OCCLUSAL PLANES AND CURVES
 CURVE OF SPEE
 CURVE OF WILSON
 CURVE OF MONSON
 CURVE OF SPEE
IT REFERS TO THE ANTERO – POSTERIOR CURVATURE OF
THE OCCLUSAL SURFACES, BEGINNING AT THE TIP OF THE
LOWER CUSPID AND FOLLOWING THE CUSP TIPS OF THE
BICUSPIDS AND MOLARS, CONTINUING AS AN ARC THROUGH
THE CONDYLE.
IF THE CURVE IS EXTENDED, IT WOULD FORM A CIRCLE OF
ABOUT 4” DIAMETER.
CURVE OF SPEE - RESULTS FROM VARIATIONS IN AXIAL
ALIGNMENT OF THE LOWER TEETH.

9.  CURVE OF WILSON
THIS IS A CURVE THAT CONTACTS THE BUCCAL AND
LINGUAL TIPS OF THE MANDIBULAR BUCCAL TEETH. THE
CURVE IS MEDIO – LATERAL ON EACH SIDE OF THE ARCH.
IT RESULTS FROM INWARD INCLINATION OF THE LOWER
POSTERIOR TEETH.
THE CURVE OF WILSON HELPS IN TWO WAYS –
 TEETH ARE ALIGNED PARALLEL TO THE DIRECTION OF
MEDIAL PTERYGOID MUSCLE FOR OPTIMUM RESISTANCE TO
MASTICATORY FORCES.
 THE ELEVATED BUCCAL CUSPS PREVENT FOOD FROM
GOING PAST THE OCCLUSAL TABLE.

11.  CURVE OF MONSON
THE CURVE OF MONSON IS OBTAINED BY EXTENDING THE
CURVE OF SPEE AND THE CURVE OF WILSON TO ALL THE
CUSPS AND INCISAL EDGES.

12. CENTRIC RELATION AND CENTRIC OCCLUSION
CENTRIC RELATION – IT IS THE RELATION OF THE
MANDIBLE TO THE MAXILLA, WHEN THE MANDIBULAR
CONDYLES ARE IN THE MOST SUPERIOR AND RETRUDED
POSITION IN THE GLENOID FOSSA, WITH THE ARTICULAR
DISC PROPERLY INTERPOSED.
IT IS ALSO CALLED AS LIGAMENTOUS POSITION OR
TERMINAL HINGE POSITION.
CENTRIC OCCLUSION – IT IS THAT POSITION OF THE
MANDIBULAR CONDYLE, WHEN THE TEETH ARE IN
MAXIMUM INTERCUSPATION. CENTRIC OCCLUSION IS ALSO
KNOWN AS INTERCUSPAL POSITION OR CONVENIENCE
OCCLUSION.

13. CENTRIC RELATION AND CENTRIC OCCLUSION SHOULD
COINCIDE IN ORDER TO HAVE PERFECT HARMONY
BETWEEN THE TEETH, TMJ AND THE NEUROMUSCULAR
SYSTEM.
MAXIMUM INTERCUSPATION CAN ALSO OCCUR WITHOUT
THE CONDYLES BEING IN CENTRIC OCCLUSION. THIS IS
KNOWN AS MAXIMUM INTERCUSPATION, HABITUAL
OCCLUSION OR ACQUIRED OCCLUSION.

14. CENTRIC CONTACTS
THESE ARE THE AREAS OF TEETH THAT CONTACT THE
OPPOSING TEETH. CENTRIC CONTACTS HAVE BEEN
CLASSIFIED INTO POSTERIOR AND ANTERIOR CENTRIC
CONTACTS.
POSTERIOR CENTRIC CONTACTS – THESE CONSISTS OF THE
FACIAL RANGE OF CONTACTS AND THE LINGUAL RANGE OF
CONTACTS.
THE FACIAL RANGE OF POSTERIOR CENTRIC CONTACTS
INVOLVE THE MANDIBULAR FACIAL CUSP TIPS, CONTACTING
THE CENTRAL FOSSA AND MESIAL MARGINAL RIDGES OF
THE OPPOSING MAXILLARY TEETH.
THE LINGUAL RANGE OF POSTERIOR CENTRIC CONTACTS
INVOLVE THE MAXILLARY LINGUAL CUSP TIPS, CONTACTING
THE CENTRAL FOSSA AND DISTAL MARGINAL RIDGES OF THE
OPPOSING MANDIBULAR TEETH.

15. ANTERIOR CENTRIC CONTACTS – THE ANTERIOR TEETH HAVE
ONLY ONE RANGE OF CENTRIC CONTACTS AND ARE IN LINE
WITH THE FACIAL RANGE OF THE POSTERIOR CENTRIC
CONTACTS.
POSTERIOR CENTRIC CONTACTS RESULT IN AXIALLY
DIRECTED FORCES AS THE CONVEX CUSP TIPS OCCLUDE ON
AN OPPOSING TOOTH AREA, THAT IS PERPENDICULAR TO
THE FORCE.
WHEN THESE CONTACTS OCCUR ON INCLINES, IT IS CALLED
AS PODED CENTRIC CONTACTS. IF THE CONTACTS OCCUR ON
TWO INCLINES, IT IS CALLED AS BI – PODED CONTACT, ON
THREE INCLINES ARE CALLED TRI – PODED CONTACTS AND
ON FOUR INCLINES ARE KNOWN AS QUADRA – PODED
CONTACTS.

17. ECCENTRIC OCCLUSION
ECCENTRIC OCCLUSION REFERS TO CONTACT OF TEETH
THAT OCCURS DURING MOVEMENT OF THE MANDIBLE. IT
CAN BE OF TWO TYPES –
1. FUNCTIONAL OCCLUSION
2. NON – FUNCTIONAL OCCLUSION
1. FUNCTIONAL OCCLUSION
IT IS ALSO CALLED AS WORKING SIDE OCCLUSION,
REFERRING TO TOOTH CONTACTS THAT OCCUR IN THE
SEGMENT OF THE ARCH TOWARDS WHICH THE MANDIBLE
MOVES. IT CAN BE OF TWO TYPES – LATERAL AND
PROTRUSIVE FUNCTIONAL OCCLUSION.

18. LATERAL FUNCTIONAL OCCLUSION – IT INCLUDES TOOTH
CONTACTS THAT OCCUR ON CANINES AND POSTERIOR
TEETH, ON THE SIDE TOWARDS WHICH THE MANDIBLE
MOVES. THE LATERAL FUNCTIONAL MOVEMENTS CAN BE OF
TWO TYPES – CANINE GUIDED OCCLUSION AND GROUPED
LATERAL OCCLUSION.
CANINE GUIDED OCCLUSION
DURING LATERAL MANDIBULAR MOVEMENTS, THE
OPPOSING UPPER AND LOWER CANINES OF THE WORKING
SIDE CONTACT, THEREBY CAUSING DISCLUSION OF ALL
POSTERIOR TEETH ON THE WORKING AND THE BALANCING
SIDES. IT IS USUALLY SEEN IN YOUNG PERSONS WITH
UNWORN DENTITION.

19. GROUPED LATERAL OCCLUSION
IN ADDITION TO CANINE GUIDANCE, CERTAIN OTHER
POSTERIOR TEETH ON THE WORKING SIDE ALSO CONTACT
DURING LATERAL MOVEMENTS OF THE MANDIBLE. THIS
TYPE OF CONTACT DURING LATERAL MOVEMENT IS CALLED
GROUPED LATERAL OCCLUSION.
PROTRUSIVE FUNCTIONAL OCCLUSION – IT INCLUDES
ECCENTRIC CONTACTS THAT OCCUR WHEN THE MANDIBLE
MOVES FORWARD. IDEALLY, THE SIX MANDIBULAR
ANTERIOR TEETH CONTACT ALONG THE LINGUAL INCLINES
OF THE MAXILLARY ANTERIOR TEETH WHILE THE
POSTERIORS DISOCCLUDE.

20. 2. NON – FUNCTIONAL OCCLUSION
THESE ARE THE TOOTH CONTACTS THAT OCCUR IN THE
SEGMENT AWAY, FROM WHICH THE MANDIBLE MOVES. FOR
EXAMPLE, IF THE MANDIBLE IS MOVED TO THE LEFT SIDE,
CONTACTS OCCUR ON THE RIGHT SIDE OF THE ARCH. IT IS
ALSO KNOWN AS BALANCING OCCLUSION.
DISCLUSION
IT IS THE DISOCCLUSION OR SEPARATION OF NON –
FUNCTIONAL POSTERIOR TEETH DURING ECCENTRIC
MOTIONS OF THE JAW. DISCLUSION OF THE POSTERIOR
TEETH IS BROUGHT ABOUT BY CONDYLAR GUIDANCE AND
INCISAL GUIDANCE.

21. CONDYLAR GUIDANCE – IT REFERS TO THE DOWNWARD
MOVEMENT OF BOTH THE CONDYLES ALONG THE SLOPES OF THE
ARTICULAR EMINENCE DURING PROTRUSIVE MOVEMENTS,
LEADING TO SEPARATION OF THE POSTERIOR TEETH. WHEREAS,
IN CASE OF LATERAL MOVEMENTS, THE CONDYLE ON THE NON –
FUNCTIONING SIDE TRANSLATES FORWARD ALONG THE
EMINENCE, WHILE THE CONDYLE ON THE FUNCTIONING SIDE
PIVOTS IN IT’S FOSSA, LEADING TO DISCLUSION OF POSTERIORS
ON THE NON – FUNCTIONING SIDE.
INCISAL GUIDANCE – IT REFERS TO ANTERIOR TOOTH FUNCTIONS
WHICH SEPARATE THE POSTERIOR TEETH DURING ECCENTRIC
MOTIONS OF THE JAW. DURING LATERAL AND PROTRUSIVE
MOVEMENTS OF THE MANDIBLE, THE LOWER ANTERIOR TEETH
MOVE DOWNWARD FROM THEIR CENTRIC CONTACT, TOWARDS
THE INCISAL EDGES OF THE MAXILLARY TEETH, WHILE
DISOCCLUDING THE NON – FUNCTIONAL TEETH.

22. TERMINOLOGY
 IDEAL OCCLUSION
 PHYSIOLOGIC OCCLUSION
 BALANCED OCCLUSION
 FUNCTIONAL OCCLUSION
 THERAPEUTIC OCCLUSION
 TRAUMATIC OCCLUSION
 TRAUMA FROM OCCLUSION

23. ANDREW’S SIX KEYS TO NORMAL OCCLUSION
ANDREW’S DURING THE 1970’s PUT FORWARD THE SIX
KEYS TO NORMAL OCCLUSION, AFTER STUDYING 120
MODELS OF PATIENTS WITH IDEAL OCCLUSION.
1) MOLAR INTER – ARCH RELATIONSHIP
2) MESIO – DISTAL CROWN ANGULATION
3) LABIO – LINGUAL CROWN INCLINATION
4) ABSENCE OF ROTATION
5) TIGHT CONTACTS
6) CURVE OF SPEE

24. 1) MOLAR INTER – ARCH RELATIONSHIP
THE MESIOBUCCAL CUSP OF THE UPPER FIRST MOLAR MUST
OCCLUDE IN THE GROOVE BETWEEN THE MESIAL AND
MEDIAL BUCCAL CUSP OF THE LOWER FIRST MOLAR. THE
MESIOLINGUAL CUSP OF THE UPPER FIRST MOLAR SHOULD
OCCLUDE IN THE CENTRAL FOSSA OF LOWER FIRST MOLAR.
THE CROWN OF THE UPPER FIRST MOLAR MUST BE
ANGULATED SO THAT THE DISTAL MARGINAL RIDGE
OCCLUDES WITH THE MESIAL MARGINAL RIDGE OF LOWER
SECOND MOLAR.
2) MESIO – DISTAL CROWN ANGULATION
A LINE THAT PASSES ALONG THE LONG AXIS OF THE CROWN
THROUGH THE MOST PROMINENT PART IN THE CENTRE OF
THE LABIAL OR BUCCAL SURFACE IS CALLED AS THE LONG
AXIS OF THE CLINICAL CROWN.
FOR THE OCCLUSION TO BE CONSIDERED NORMAL, THE
GINGIVAL PART OF THE LONG AXIS OF THE CROWN MUST BE
DISTAL TO THE OCCLUSAL PART OF THE LINE.

25. 3) LABIO – LINGUAL CROWN INCLINATION
IT IS DETERMINED FROM A MESIAL OR DISTAL VIEW. IF THE
GINGIVAL AREA OF THE CROWN IS MORE LINGUALLY PLACED
THAN THE OCCLUSAL AREA, IT IS REFERRED TO AS POSITIVE
CROWN INCLINATION. IN CASE, THE GINGIVAL AREA OF THE
CROWN IS MORE LABIALLY OR BUCCALLY PLACED THAN THE
OCCLUSAL AREA, IT IS REFERRED TO AS NEGATIVE CROWN
INCLINATION.
THE MAXILLARY INCISORS EXHIBIT A POSITIVE, WHEREAS THE
LOWER INCISORS SHOW A MILD NEGATIVE CROWN
INCLINATION. THE MAXILLARY AND MANDIBULAR POSTERIORS
HAVE A NEGATIVE CROWN INCLINATION.
4) ABSENCE OF ROTATIONS
A NORMAL OCCLUSION IS CHARACTERIZED BY ABSENCE OF
ANY ROTATION. ROTATED POSTERIOR TEETH OCCUPY MORE
SPACE IN THE DENTAL ARCH, WHILE ROTATED INCISORS
OCCUPY LESS SPACE IN THE ARCH.

26. 5) TIGHT CONTACTS
TO CONSIDER AN OCCLUSION AS NORMAL, THERE SHOULD BE
TIGHT CONTACTS BETWEEN THE ADJACENT TEETH.
6) CURVE OF SPEE
ACCORDING TO ANDREWS, A NORMAL OCCLUSAL PLANE
SHOULD BE FLAT, WITH THE CURVE OF SPEE NOT EXCEEDING
1.5 mm.

27. ANDREW’S SIX KEYS TO
NORMAL OCCLUSION

28. THANK YOU