Dental Surveyor: Components, Types, and Objectives PDF

a- Knowledge and understanding By the end of this course the student will be able to: a1- Identify the different steps for partial denture construction a2- State the components of the partial denture a3- Justify reasons for a badly constructed denture a4- Identify the devices used in the different s...

a- Knowledge and understanding By the end of this course the student will be able to: a1- Identify the different steps for partial denture construction a2- State the components of the partial denture a3- Justify reasons for a badly constructed denture a4- Identify the devices used in the different steps a5- Learn about the properties and behavior of the materials used during the construction. B-Intellectual Skills: b1-Identify their errors in the practical work  Components of RPD I. Denture Base It is that part of the denture which rests on the tissues and to which artificial teeth are attached.  Components of RPD 2. Occlusal rests is a rigid extension of a removable partial denture which contacts a remaining tooth structure providing vertical support and transmitting functional forces to the remaining  Components of RPD III. Direct Retainer It is that part of the denture that engages an abutment tooth to resist displacement of the prosthesis away from the basal seat tissues.  Components of RPD IV. Major Connector It is the unit of the partial denture that connects parts of the prosthesis located on one side of the arch with those on the opposite side.  Components of RPD V. Minor Connector It is the connecting unit between the major connector and other units of the prosthesis. Terminology  Undercut Survey line Guiding planes Path of insertion and path of removal of the denture. Undercut An area of tooth or soft tissue which is beyond the survey line when viewed from a particular direction Survey line A line drawn on a tooth to indicate the greatest circumference in a given horizontal plane. The survey line divides parts of teeth or other tissues into undercut and non-undercut areas. Survey line Undercut Area Types of undercuts Tooth Undercuts Soft Tissue or bony Undercuts  Types of undercuts 1-Desirable Undercuts 2-Undesirable Undercuts **All the Undercuts are Undesirable undercuts Except that used for Denture Retention Components Of Metallic Removable Partial Dentures Are All Rigid, With The Exception Of The Flexible Retentive Clasp Arm Located In An Undercut Area For Retaining The Restoration Against Flexible clasp arm engaging tooth undercut Dislodging Forces Path of Insertion ✓Is The Direction in Which a Restoration Moves From the Point of Initial Contact With the Supporting Teeth until it reaches its fully seated position where the occlusal rests are seated in its position and the denture base is in contact with t h e t i s s u e s. Terminal resting position Path of Removal The Direction of Movement of the Restoration From Its Resting Position to the Last Contact With the Supporting Teeth". It Is the Reverse of the Path of Insertion Terminal resting position  Guiding planes Flat Axial Surfaces In An Occluso-gingival Direction On The Proximal Or Lingual Surfaces Of Teeth Guiding the prosthesis during insertion and removal of the denture Factors Affecting Path of Insertion 1. Interferences - Changing the path of insertion - Contouring the tooth surface - Surgery to remove interfering structures 2. Retentive undercuts should be equal in depth and permit the location of clasp tips in the gingival third of the tooth 3. Guiding planes 4. Esthetics Made possible with less clasp metal and less base material displayed 5. Health of teeth used as abutment Place the clasp on the stronger abutment 1. Interference Features of the mouth which interfere with easy insertion and removal of a denture Examples Severe Lingual Inclination Of Teeth – Mandibular – Undercut ToriThe labial undercut Alveolar Ridges here is a source of ‘interference’ ✓ If a bony undercut is present labially, insertion of a flanged denture along a path at right angles to the occlusal plane will only be possible if the flange stands away from the mucosa or is finished short of the undercut area. This can result in poor retention as well as a poor appearance. ✓ If the cast is given a posterior tilt so that the rod, and thus the path of insertion, is parallel to the labial surface of the ridge it is possible to insert a flange that fits the ridge 19 accurately. How to overcome the problem of interference? Avoidance - changing path of insertion Elimination - modify teeth (or bone ?) - Contouring the tooth surface - Surgery to remove interfering structures Exploitation - sectional dentures 2. Retentive undercuts Undercut areas usually on buccal or lingual surfaces of teeth which may be used for clasping Depth of undercut required depends on clasp material, length and cross sectional area of clasp arm.  Rule: Retentive tip should usually be designed to be placed in the gingival 1/3  Post Is More Readily Removed by Application of Force Near Its Top Than by Applying Same Force Nearer Ground Level 24 ◼ Inadequate retention ◼ Excessive retention Create a “dimple” retention Tooth alteration to lower area by enamoplasty the height of contour Or Crown the tooth 3- Guiding planes * Two or more parallel axial surfaces In An Occluso- gingival Direction On The Proximal Or Lingual Surfaces Of Teeth. *Parallel To The Path Of Insertion Help In *Guiding The Prosthesis During Insertion and Removal Guide surfaces may occur naturally on teeth but more commonly need to be prepared. A guide surface should extend vertically for about 3 mm, and should be kept as far from the gingival margin as possible The functions of guiding planes Guide the Prosthesis in or Out of Place Without Exerting Excessive Forces Against the Teeth The Frictional Contact of the Prosthesis Against These Parallel Surfaces, Contribute to the Retention of the Prosthesis Provide Bracing and Stability When they are Located on the Axial Lingual Surface of the Tooth  Minimize the Amount of Space Between the Denture and the Tooth Thus Making the Prosthesis More Hygienic Reciprocation  4- Appearance Undercuts may affect appearance when anterior teeth are to be replaced Mesial undercuts on teeth adjacent to saddle ; bony undercut labially Cast tilting may reduce anterior spaces and reduce blocking out of labial undercut BY POSTERIOR TILT THIS UNSIGHTLY GAP CAN BE AVOIDED  Surveying It is the procedure of locating and delineating the contour and position of the abutment teeth and associated structures before designing a removable partial denture  THE DENTAL SURVEYOR It Is a “Paralleling Instrument Used to Determine the Survey Line of Teeth, Identify and Measure Tooth Undercuts and to Determine the Relative Parallelism of the Surfaces of Teeth and Other Areas on the Cast” A- The Base B- Vertical Upright Column C- Cross Arm with Spindle Housing D- The Vertical Spindle With Tool Holder E- Screw To Lock The Spindle F- Tool Holder H- The Surveyor Table M- Ball Retaining Ring N- Tool Rack O- Storage Compartment Parts of a Surveyor Parts of a Surveyor Surveying Tools 1- Analyzing Rods 2- Carbon Marker 3- Undercut Gauge 4- Wax Trimmer  Surveyor tools 1. Analyzing rod It is a rigid metal rod used for diagnostic purposes ,to locate the presence or absence of undercuts Analyzing Rod  Parallel Guiding Surfaces Guiding surfaces, as determined by the path of insertion Parallel guiding surfaces of anterior abutment Determine soft tissue undercut  2. Undercut gauges Used to measure the extent of the undercuts that are being used for clasp retention. Usually there are three sizes: 0.01, 0.02 and 0.03 of an inch.. 01”. 02”. 03”  Undercut Gauges Of an inch ??? of mm. Undercut Gauge Desirable Undercut 3. Carbon rod & reinforcing sheath To mark the survey line on the cast at a given position. A metal shield is used to protect it from breakage. False survey line X Moved around the tooth and along the alveolar ridge  4. Wax trimmer It is used to trim excess wax that may be inserted into those undercut areas, which are to be obliterated. Why do we survey dental casts ? and What are the objectives ? A partial denture must be designed so that it can be easily inserted and removed by the patient, and retained against reasonable dislodging forces and will have the best possible appearance.  Objectives of Surveying 1. Determine the Relative Parallelism of Teeth Surfaces That Act As Guiding Planes 2. Determine Soft, Bony or Tooth Undercuts and Areas of Interferences 3. Identify and Measure Tooth Undercuts 4. Delineate the survey Line A line drawn on a cast by the surveyor marking the greatest prominence of the contour in relation to the planned path of placement of a prosthesis 5. Paralleling crown restorations  6. Trimming Blockout Material Parallel to the Path of Placement 7. Permit an Accurate Charting of the Required Mouth Preparations 8. Determine the Most Acceptable Path of Placement and Removal  9. Recording the Cast Position Tripoding: To be able to reproduce the most advantageous position of the cast at a later date Scoring: References Davenport and Pollard: Aspects of partial denture design; Assigned Reading University of Birmingham.U.K. for Lecture #4 Removable Partial Dentures RT 453S Ting-Ling Chang, DDS, Division of Advanced Prosthodontics, UCLA School of Dentistry Surveying casts for partial Dentures, Dr Michael J. Barsby Applegate OC. Essentials of removable partial denture prosthesis. 1st ed. Philadelphia (PA): W. B. Saunders Co.;. Swenson M, Terklo L. Partial denture. 1st ed. St. Louis (MO): C.V. Mosby Co.;. McCracken WL. Partial denture construction. 1st ed. St. Louis (MO): C.V. Mosby Co.; 200 Partial Removable Prosthodontics, by Kratochvil Chapter 10