81 - model cast RPD. principle of model cast framework construction

1. Surveying:

   • To identify the most favorable tilt, the retentive undercuts and interferences.

   • To located and delineate the contours and relative positions of abutment teeth and associated structures.

   • Path of insertion. • Recording the position of the cast.

   • Measuring the retention.

   • Recording the prosthetic equator.

   • (Survey lines are transferred to soft tissue areas that may be contacted by components of a RPD. These commonly include soft tissue areas that may be contacted by infrabulge (bar type) clasps. The clinician must ensure that survey lines have been transferred to all facial and lingual surfaces).

2. Planning

   • placing b help of surveyor

3. Teeth preparation

   • fixing teeth in wax in right position

   • (Master casts are modified by the addition of wax relief to non-bearing regions and by the placement of block out wax parallel to the path of insertion at regions beneath the height of contour where framework contact is not planned (i.e. All areas except retentive clasp tips).)

   • (Diagnostic casts can serve as a visual guide for tooth preparation.)

4. model cast denture technology

   • Flasking process

   • High temperature Polymerization cycle (long or short)

   • After cooling, remove the denture from the gypsum

   • Clean and polish

1. Surveying:

   • To identify the most favorable tilt, the retentive undercuts and interferences.

   • To located and delineate the contours and relative positions of abutment teeth and associated structures.

   • Path of insertion. • Recording the position of the cast.

   • Measuring the retention.

   • Recording the prosthetic equator.

   • (Survey lines are transferred to soft tissue areas that may be contacted by components of a RPD. These commonly include soft tissue areas that may be contacted by infrabulge (bar type) clasps. The clinician must ensure that survey lines have been transferred to all facial and lingual surfaces).

2. Planning

   • placing b help of surveyor

3. Teeth preparation

   • fixing teeth in wax in right position

   • (Master casts are modified by the addition of wax relief to non-bearing regions and by the placement of block out wax parallel to the path of insertion at regions beneath the height of contour where framework contact is not planned (i.e. All areas except retentive clasp tips).)

   • (Diagnostic casts can serve as a visual guide for tooth preparation.)

4. model cast denture technology

   • Flasking process

   • High temperature Polymerization cycle (long or short)

   • After cooling, remove the denture from the gypsum

   • Clean and polish

Three steps are involved in making a denture framework by using relief, block out ledges, and ready made pattern forms:

• Prepare the base model – Start with a master cast (a detailed mold of the patient's mouth). Areas where the denture will sit are given extra space (relief), and certain undercut areas are smoothed out (block out) to prevent unwanted fitting issues. Small ledges are also shaped to help secure the clasps.

• Create the framework pattern – A major connector (usually a lingual bar) is formed to link both sides of the denture. Pre-made plastic clasp forms are positioned carefully to rest on supportive ledges. Additional wrought wire and a mesh structure are added to allow the denture base to attach properly.

• Finish the metal framework – The completed framework pattern is used to cast the final metal framework of the denture. Once done, it's placed back on the master cast to check the fit and prepare for final adjustments.

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