Preclinical Prosthetic Dentistry · MU Plovdiv

72. Metal cast clasps – parts, types.

Inside: 6 sections · 1 labelled picture · 3 tables · 13 flashcards · 3 min

Topic 72 of 96 in the MU Plovdiv syllabus for Preclinical Prosthetic Dentistry (Dental Medicine, Year 2). The free AceMed note covers it in 6 sections, about 199 words (3 min of reading), with 13 flashcards.

In this note

  1. Introduction
  2. The dental surveyor
  3. Survey lines
  4. The five Ney clasps
  5. Undercut depth: the Ney gauge
  6. Other cast clasp designs

Introduction

Cast clasps are cast in one piece with the metal framework of a partial denture. The Ney system organizes their design around the dental surveyor: each abutment is surveyed, the survey line is drawn, and the clasp type is chosen to match that line.

The dental surveyor

A surveyor (parallelometer) holds the cast on a tilting table under a vertical arm. The first surveyor was introduced in 1918, and Ney produced the first widely used instrument. It is used to:

  • Choose the path of insertion by tilting the cast.
  • Draw the survey line (height of contour) on each abutment with a carbon marker.
  • Measure undercut depth with gauges.
  • Find guide planes and block out unwanted undercuts.
  • Check parallelism of crown preparations, attachments and milled surfaces.

Undercut depth: the Ney gauge

How deep the retentive tip may go depends on how flexible the arm is:

Too deep an undercut makes the clasp overstress the tooth or deform; too shallow, and the denture won't stay in.

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