Dental Screws in Dental Implant Prosthodontics Part 3 of 4

Classification based on location of the screws.

The dental screws may be placed in the following locations
1. Crown.
2. Root.
3. Cast Crown.
4. Coping.
5. Post.
6. Bar.

Inner coping of implants where the outer section of prosthetic component will be attached.

Screws are placed in metal structures when insertion and removal will be required.

Intracoronal screws
Screws are inserted within the crown contour using the correct reaming or tapping instruments. Once they are in place, the screws may provide retention for a restorative material which in turn may become a core. Of the various types of screw used in this way, the following are the examples:
– TMS pin
– Reten pin

Occasionally, screws are used to add to the retention of a casting. The divergent screws pass through threads in the Casting into the underlying dentin. A screw may act as a retainer for a resin veneer cast crown.

Intra root screws
A screw is inserted into the root preparation to retain a prosthesis such as a cast crown; a retaining device covers the screw. The following systems are among those that are available.
Kurer Crown anchor system
Post and core system
Kurer press stud
The Kurer press stud has a male part on its head. The female part may be simply placed over the male after the stud shaped projection has been screwed into the prepared root.

Copings
The inner component of a telescopic crown or possibly a double inlay is locked to the tooth crown with a screw to form an abutment. Preformed screws are commonly used.

Posts
Screws are used in two ways:
1. to screw a cast crown and bar to manufactured threaded core; such cores have been soldered to a diaphragm that covers the root face.
2. to lock a cast crown with a screw to a laboratory constructed core in which a threaded tube has been incorporated.

Posts incorporating screws
A root diaphragm may be attached to its retaining post by means of a screw. This system, occupies the minimum of vertical space. The VK double screw provides an alternative method. A threaded post is seated in the prepared root, allowing the prosthesis to be removed at any time by the operator by undoing the screw which fits into a threaded hole. One can consider this to be a screwblock system using both the root and metal.

Bar
A prosthesis is locked to a bar with a preformed screw. The screw assembly should be placed through the top or lateral surfaces of the bar.

Other Classification of Dental Screws:

Reference
Matsuo E, (1981): Screw Retained Dental Prosthesis, Quintessence Publishing Ed. 1.

Written by:
Jesus Lecitona+
Dental Implants Cost website – http://costofdentalimplant.com/
PDA Information Committee Member
PDA Pangasinan Chapter
PDA San Juan City Chapter

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