Today AM Seminar 3157 Get Casts from Marjorie

Today • AM - Seminar - 3157 – – Get Casts from Marjorie Survey Class I & II Casts (no preps) Tripod Casts Get Heads & Mounts ready for PM • PM - Clinic – Prepare guiding planes on Class I & II Typodonts (last sheet Course Sched) – Formative – Marking sheets – Diagnostic Casts Mark Sheets - Hand in

Surveying, Path of Insertion, Guiding Planes

Definitions • Height of contour • Undercut = Infrabulge • Suprabulge

Definitions • Height of contour • Undercut = Infrabulge • Suprabulge

Rule: Retentive tip should usually be designed to be placed in the gingival 1/3

Path of Insertion • Path that the prosthesis is – Placed/removed – Usually a single path

Advantages of a Single Path of Insertion • Equalizes retention

Advantages of a Single Path of Insertion • Bracing and Cross-arch Stabilization

Advantages of a Single Path of Insertion • Minimizes torque on abutments

Advantages of a Single Path of Insertion • Allows removal without encountering interferences

Advantages of a Single Path of Insertion • Directs forces along axes of teeth

Advantages of a Single Path of Insertion • Provides frictional retention

Selecting a Single Path of Insertion • Use a dental surveyor to – Select path – Prepare guiding planes

Guiding Plane Preparation • Where rigid components contact abutments • Proximal Plates • Bracing Arms • Rigid portions of Retentive Arms

Other Uses of a Surveyor • Blocking out undesirable undercuts – Ensures the framework is not cast in an undercut

Parts of a Surveyor • Surveying Table

Parts of a Surveyor • Surveying Arm

Parts of a Surveyor • Surveying Tools – Analyzing Rod

Parts of a Surveyor • Surveying Tools – Carbon Markers

Parts of a Surveyor • Surveying Tools – Undercut Gauges . 01” . 02” . 03”

Undercut Gauges

Parts of a Surveyor • Surveying Tools – Wax Trimmer

Selecting a Path of Insertion • Orient cast relatively horizontal – Final tilt rarely more than 10° from horizontal

Selecting a Path of Insertion • Place analyzing rod against abutments – Contact point is Height of Contour - Below is infrabulge - Above is suprabulge

Selecting a Path of Insertion • Tilt cast to obtain maximum parallelism – Heights of contour are at relatively same position occluso-gingivally – Equal amounts of undercut

Altering Path of Insertion • Proximal surfaces similar undercuts • Retentive areas similar undercuts

Selecting a Path of Insertion • Modify tilt if necessary – Soft tissue interferences

Selecting a Path of Insertion • Modify tilt if necessary – Esthetics

Once Path Selected • Instructor: – Approves path – Demo: - Mark heights of contour with carbon marker - Tripod

Selecting a Path of Insertion • Lock cast position & tripod

Tripoding

Optimal Path of Insertion • Retentive undercuts equalized – Retentive arm has a different path of escapement than guiding plane, so it must flex during removal

Optimal Path of Insertion • Retentive undercuts equalized – Ideally, retentive arms should oppose each other on opposite sides of the arch

Optimal Path of Insertion • Minimize severe tooth & soft tissue interferences

Optimal Path of Insertion • Esthetics – Minimize display of clasps, metal components

Optimal Path of Insertion • Prepare Guiding Planes – Flat surfaces parallel to path of insertion – Control & limit movement of RPD – Initial contacts for RPD

Guiding Planes • Stabilization

Effectiveness of Guideplanes • Most effective when: – Parallel to each other – More than one common axial surface

Effectiveness of Guideplanes • Most effective when: – Directly opposing each other

Effectiveness of Guideplanes • Most effective when: – Prepared on several teeth – Cover a large surface area

Assessing Guiding Planes Proximal View Facial View Carbon Markings

Preparing Guiding Planes • Select path of insertion • Design Partial Denture * • Select number & position of guiding planes • Prepare guiding planes

Use Surveyor to Align Bur Intraorally

FINGER REST!

Burs 8837 K-014 • Long Cylindrical Carbide or Diamond (8837 K 014)

Guiding Plane Dimensions

Axial Surface Already Parallel to Path of Insertion • NO Preparation !

Polish Prepared Surfaces • Rubber wheels or points

Prepare Guiding Planes First

Effects of Guiding Planes On Retention & Stability • Maintains Retention

Effects of Guiding Planes On Retention & Stability • Minimizes Need for Retention

Effects of Guiding Planes On Retention & Stability • Stabilizing Teeth

Other Alterations of Axial Contours • Lowering Heights of Contour – Rigid elements contacting abutments – Improve esthetics – Prepare guiding planes most efficient method to lower

Other Alterations of Axial Contours • Raising Heights of Contour – Insufficient retention in gingival 1/3 (at least 1 mm from gingiva) – Prepare undercut – Add resin above to create undercut

Preparing Retention • Axial surface must be close to parallel the path of insertion

Retentive Preparation Shape • Follows the path of designed retentive tip

Creating Undercuts with Bonded Resins • Axial surface must be close to parallel the path of insertion

Summary of Abutment Modifications • After RPD Designed – Guideplanes – Lower heights of contour to eliminate interferences & improve esthetics – Create undercuts if absolutely necessary (raising heights of contour) – Rest seat preparation