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Occlusion is
the static relationship of the teeth and is basic to all aspects of dentistry. The act of being closed, maxillary teeth contact mandibular teeth.
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Intra-arch Alignment - Plane of Occlusion
- Maxilla - Convex
- Mandible - Concave; Curve Of Wilson and Bonwill’s Triangle (Frontal); Curve Of Spee (Sagittal); Monson Sphere (4" radius)
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Intra-arch Alignment - Tooth Angulation
- Mandible - Sagittal: Anterior and posterior teeth inclined mesially
- Maxilla - Sagittal: Anterior teeth inclined mesially; 3rd molar inclined distally
- Mandible - Frontal: Posterior teeth inclined lingually
- Maxilla - Frontal: Posterior teeth inclined buccally
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Occlusal Table
Area between the buccal and lingual cusp tips; 50 - 60% of total buccolingual dimension
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Arch length
- Distance from distal of last molar to distal surface of opposite last molar
- Maxillary arch (128mm) slightly larger than mandibular (126mm) due to width of mandibular incisors
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Arch Width
- Distance across the arch
- Mandibular width less than maxillary arch; Maxillary tooth facial to mandibular tooth
- Mandibular BOL with Maxillary CFL
- Maxillary LOL with Mandibular CFL
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During chewing, Maxillary buccal cusp prevent _____. Mandibular lingual cusps prevent _____. Cheek, lip and tongue _________.
- cheek biting
- tongue biting
- replace food onto occlusal surface
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Supporting Cusps
- Contact central fossa
- maxillary lingual & mandibular buccal cusps
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Guiding/Non Supporting Cusps
- Minimize tissue trauma
- maintain food on occlusal table
- guide the mandible during movements
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Functional outer inclines/aspects
small area (1mm) on supporting cusp, only area of outer incline with functional significance
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CROSS BITE
Mandibular lingual contact maxillary central fossa. Maxillary buccal contact mandibular central fossa.
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Class I Molar Occlusion (80%)
Mesiobuccal cusp of mandibular first molar occludes _________;
Max ML cusp of M1 occludes ________;
Mesiobuccal cusp of the maxillary first molar _______.
- in the embrasure area between maxillary second premolar and first molar
- in CF of Man M1
- is aligned directly over the buccal groove of the mandibular first molar
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Class II Molar Occlusion
Mandibular first molar more _____.
Mesiobuccal cusp of mandibular first molar occludes ____________.
Distolingual cusp of the maxillary first molar occludes ____________ and is aligned _________.
- distal
- in the central fossa area of the maxillary first molar
- in the central fossa area of the mandibular first molar
- directly under the buccal groove of the maxillary first molar
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Class III Molar Occlusion
Mandibular first molar more _______.
The distobuccal cusp of the mandibular first molar occludes _________.
The mesiobuccal cusp of the maxillary first molar _________.
The mesiolingual cusp of the maxillary first molar occludes ________.
- mesial
- in the embrasure between the maxillary second premolar and first molar
- is situated over the embrasure between the mandibular first and second molar
- in the mesial pit of the mandibular second molar
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The occlusion of anterior teeth functions
- Incise food
- Speech
- Lip support
- Esthetics
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The occlusion of posterior teeth functions
- Break up food
- Withstand occlusal forces
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Anterior Teeth angulation
12-28 degree labial inclination of max. and mand. anterior teeth
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Anterior overlap
- 3 to 5 mm of the mand. anterior teeth are hidden by the max.
- Vertical overlap is the distance between the incisal edges
- Horizontal overlap is the distance between the labial surfaces
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Vertical overlap+Horizontal overlap =
Incisal Guidance
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6 variations of anterior overbite
- Class I: Normal overbite
- Class II Div 1: Deep overbite (Man. occlude w/ the gingival third of Max) & Normal labial inclination
- Class II Div 2: Deep overbite & lingual inclination of max. incisors
- Class III: Edge to Edge anterior relationship
- Class III: with reverse anterior relationship
- Anterior open bite: no incisal guidance when post teeth occlude
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Morphology of condyles of mandible
- The medial pole (MP) is more prominent than the lateral pole (LP).
- The articular surface on the posterior aspect of the condyle is greater than on the anterior aspect.
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TMJ components from temporal bone
- STF: stylotympanic fissure. Fissure btwn styloid and tympanic part
- Mandibular (glenoid) fossa
- AE: articular eminence
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Characterized by the mode of movement, TMJ is a _________ joint.
- GINGLYMOARTHROIDIAL
- ginglymoid = hinging (rotation)
- arthroidial = gliding (translation)
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Three components of TMJ
- condyle
- mandibular fossa
- articular disc - dense fibrous connective tissue; no nerves; no blood vessels
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RETRODISCAL TISSUE
- loose connective tissue
- highly vascularized & innervated
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Ligament functions
- Protect structures
- Passive restraining devices
- Limit movements
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Ligaments
- Collateral (Discal; medial/lateral) Ligaments
- Capsular Ligaments - extends anteriorly to include the articular eminence and encompass the entire articular surface of the joint.
- Temporomandibular Ligament
- ACCESSORY LIGAMENTS
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ACCESSORY LIGAMENTS
- Sphenomandibular Ligament
- Stylomandibular Ligament
- limits the protrusive movement, especially stylo-
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Muscle of mastication (nerve)
- Temporalis
- Masseter
- Medial “Internal” Pterygoid
- Lateral "External" Pterygoid - inferior & superior heads
- All supplied by the mandibular branch of CN V (Trigeminal)
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Temporalis
- Origin: lateral surface of skull
- Insertion: coronoid process of ramus
- Function: elevates & retrudes the mandible
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Masseter
- Origin: zygomatic arch
- Insertion: lateral surface of the mandibular angle
- Function: elevates & protrudes mandible, forms a sling together with Medial Pterygoid muscle
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Medial Pterygoid
- Origin: medial surface of the lateral pterygoid plate
- Insertion: medial surface of the mandibular angle
- Function: elevates & protrudes mandible
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Lateral Pterygoid - inferior head
- Origin: lateral surface of lateral pterygoid plate
- Insertion: neck of condyle
- Function: bilateral - protrudes, depress the mandible; Unilateral - lateral to the contralateral side mandible
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Non-masticatory depressor
Digastric Muscle
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Lateral Pterygoid - superior head
- Origin: Sphenoid bone
- Insertion: articular capsule, disc
- Function: move the disc during protrusion
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FRANKFORT HORIZONTAL PLANE
- Porion - Orbitale
- Porion: upper margin of ear canal
- upper member of the articulator
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Bennet angle
- 0-30 degrees
- represents the medial wall of glenoid fossa
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Condylar Guidance
Sagittal angle represents the superior wall of the glenoid fossa
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VDO, VDR, VDR-VDO
- Vertical Dimension of Occlusion (VDO): Distance between maxilla and mandible when teeth are in contact.
- Vertical Dimension of Rest (VDR): Distance between maxilla and mandible when the mandible in a physiologic rest position.
- VDR-VDO=Inter Occlusal Distance (IOD) or Free Way Space: 2-4 mm (avg 3 mm)
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Protrusive contacts
- Distal Inclines of Maxillary Teeth occlude with Mesial Inclines of Mandibular Teeth
- Maxillary Distal Inclines of Lingual Supporting Cusps
- Mandibular Mesial Inclines of Buccal Supporting Cusps
- Condyle moving down and forward with disc (follows shape of articular eminence)
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Laterotrusive & Mediotrusive
Side to Side Position and the contact on the anterior teeth
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Movement of the Man supporting cusp and Max contact site during protrusive, retrusive, laterotrusive, and mediotrusive movement
- M and M
- D and D
- B and B
- LM and LM
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Rotational movement of mandible rotate along _____.
- axis of rotation/horizontal transverse (/hinge) axis
- within the inferior cavity of TMJ (between the superior surface of the condyle and the inferior surface of the articular disc)
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Translational movement
- A movement in which each point of the moving object has simultaneously the same velocity and direction
- Occurs within the superior cavity of TMJ (between the superior surface of the articular disc and the inferior surface of the articular fossa, i.e. between the disc-condyle complex and the articular fossa)
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Border movement
reproducable and limited by the ligaments and the articular surfaces of the TMJs, as well as by the teeth.
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Functional Movement
- Intraborder movement.
- Determined by the responses of the neuromuscular system
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Mandibular movement envelope in sagittal plane
- Starts from CR: hinge movement (20-25mm), limited by TM ligaments
- Maximum opening: 40-60mm; limited by capsular ligaments
- Anterior closing border movement: limited by Stylomandibular Ligament; w/ the contraction of the inferior lateral pterygoids
- Superior contact border movement: limited by teeth morphology
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Superior contact border movement in sagittal plane
- CR->ICP: forward and upward in 90% population (~1.25mm)
- ICP->edge to edge: forward and downward: limit by contact of incisal
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Functional movement in sagittal plane
- Begin at or 2-4 mm below the ICP at the physiologic rest position of the mandible or Postural Position, PP.
- Chewing stroke like a tear drop, open in posterior direction and close in anterior direction
- Functional Opening & Closing
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Posselt’s Envelope of mandibular movement
By combining mandibular border movements in the three planes, a three-dimensional envelope of motion can be produced that represents the maximum range of movement of the mandible.
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