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Introduction to Operative Dentistry

Introduction to Operative Dentistry
Third Year

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    tooth form and occlusion tooth form and occlusion Presentation Transcript

    •  Tooth form & Occlusion  
    •   Tooth form and occlusion Importance Determine: - Restoration of teeth: Generally, the restoration should mimic the original tooth anatomy to restore 1. efficient mastication, 2. esthetics, 3. speech and 4. protection of investing tissues
    •  Agenda  Physiology of tooth form How the structure of enamel and dentin influence cavity design? Features of an ideal occlusion Factors of occlusion affecting restorative  dentistry
    •  Physiology of tooth form  Contact area  Marginal ridge  Embrasure
    •  Normal periodontium • Restoration margin should be placed supragingivally to preserve the gingival health
    • Tooth contours   • Definition: convexity of axial surfaces of teeth • Function: Protection of supporting tissues Stimulation of gingiva during mastication
    •   Tooth contours  Over-contour - Food deflect during mastication with less stimulation of gingiva. - Food retention under overcontour with consequent caries or gingivitis  Under-contour - Direct impact of food on supporting tissues causing trauma to them.  Normal
    •  Height of epithelial attachment • The epithelial attachment seals the soft tissue to the tooth. • It could be injured during - Careless probing during examination. - Improper tooth preparation techniques. • Care should be taken during tooth preparation to avoid injury to periodontal attachment.
    •  Marginal ridges • In restorative dentistry, marginal ridges should be restored in two planes; buccolingually and cervico occlusally • Adjacent marginal ridges should be restored at the same height.
    •  Embrasure • The correct relationship of embrasures, cusp to sulci, marginal ridge and grooves of adjacent and opposite teeth provide for the escape of food from occlusal surfaces during mastication. • Correct embrasure form and size is important for self cleaning action.
    •  Proximal contact Definition: height of contour of the proximal surface of tooth that touches its adjacent tooth in  the same arch    Location: - Incisal 1/3 of incisors - Premolars and molars: Junction of occlusal and middle 1/3
    • How the structure of enamel and dentin influence tooth preparation? • Enamel - Enamel is brittle and when not supported by sound dentin [undermined enamel], it is liable to fracture and should be removed.
    • How the structure of enamel and dentin influence cavity design? • Dentin -Dentin is sensitive at dentino- enamel junction due to branching of dentinal tubules at that region. -Obstruction of dentinal tubules and precipitation of minerals by aging or due to subjection to irritation reduce dentin sensitivity. - Cavity floor should be o.20.5 mm beyond sensitive DEJ for non adhesive restoration..
    • Occlusion • Definition Occlusion means the contact of teeth in opposing dental arches when the jaws are closed (static occlusal relationships) and during various jaw movements (dynamic occlusal relationships)
    • Occlusion • Definition Centric relation is the relation between mandible and maxilla where the condyle in the rear most, upper and mid most position in the glenoid fossa.
    • Occlusion Definition • Maximum intercuspation is the maximum occlusal intercuspation irrespective of condylar position. • Complete intercuspation is seen when the intercuspal position and retruded position are coincident during mandibular closure. • Occlusal contacts that prevents this are called premature contacts
    • Angle’s classification for interarch relationship - Class I: most common [maxillary mesiofacial cusp located in the mesiofacial developmental groove of the mandibular first molar] - Class II: posterior positioning of mandible to maxilla. - Class III: anterior positioning of mandible to maxilla.
    •  Mandibular movement  Rotational movement around the horizontal axis.
    •  Mandibular movement Forward movement of the mandible [protrusion]
    •  Mandibular movement Side to side movement [lateral excursions] Working  side Balancing  side
    • Features of an ideal occlusion
    •  Inter-arch tooth relationship • The contact relationship is either 1- Surface contact [anterior] 2- Cusp to fossa apposition [posterior teeth]. Supporting  cusp    
    • Cusp to fossa relationship [cusp to  marginal ridge] • Supporting cusps are mandibular buccal cusps and maxillary palatal cusps
    •  Cusp to fossa relationship • Non Supporting cusps are mandibular lingual cusps and maxillary buccal cusps          
    •  Patient with cusp to fossa contact
    • Alignment of teeth and Dental arches   • In both jaws, cusps are aligned in parabolic curves. • In normal condition, maxillary jaw overlap mandibular jaw.
    •  References Chapter 4; physiology of  tooth form Chapter 2; clinical significance of dental anatomy, histology, physiology and occlusion