What Are Pins and Posts in Dentistry

When the teeth are decayed and it has to be restored the dentist goes for the filling but sometimes the decay is extensive and a large part of the tooth is lost. In such cases pins and posts are used as the simple filling material can not give the adequate strength to sustain the masticatory forces and fractures. The pins and posts can be used separately or together as decided by the dentist.

Pins in Dentistry

There are many types of pins available in dentistry. They are basically thin metallic shafts. They are either cemented in the tooth after making the space for them or they are screwed in the tooth. They are used to give the strength to the filling. First the pins are placed in the tooth above that core built up is done and after that crown is given above that.

INDICATIONS

  1. As additional aids of retention in badly broken down or mutilated teeth.
  2. In teeth with poor prognosis i.e. endodontically and periodontically involved teeth.
  3. When one or more cusps need capping.
  4. Increased resistance and retention form is needed.

CLASSIFICATION
1.    Direct/non parallel pins- are inserted into Dentin followed by placement of restorative material directly over them.

Three major categories of direct pins are:

Cemented pins- pins are 0.001-0.002 inch smaller than their pin channels and the difference in diameter provides space for cementing medium. Are least retentive but virtually place no stress on surrounding dentin during or after placement.

Friction locked pins- are 0.001 inches larger than their pin channels and hence utilize the elasticity of dentin for retaining the tapped pins in a vise like grip. Better retention than cemented pins but generates stresses in dentin in the form of cracks or craze lines.

Threaded pins- are 0.0015-0.002 inches larger than their pin channels and like friction locked pins they are also retained by elasticity of dentin. Provides maximum retention but at the same time generates excessive stresses in the form of cracks in dentin.

Threaded pins
 

Four sizes of TMS pins.
•    Regular ( 0.031 inch [0.78 mm]
•    Minim (0.024 inch [0.61 mm]
•    Minikin (0.019 inch [0.48 mm]
•    Minuta ( 0.015 inch [0.38 mm]

2.    Indirect/parallel pins- are an integral part of Cast restoration. These pins are placed parallel to each other as well as parallel to the path of insertion of the restoration.

MATERIALS USED
1.    Stainless steel
2.    Titanium
3.    Silver
4.    Cast gold alloys
5.    Platinum-palladium
6.    Platinum-iridium
7.    Plastic
8.    Aluminium
9.    Acrylic

PRINCIPLES OF PIN PLACEMENT
Most desirable locations for pin holes are corners of the tooth and least desirable are in the middle of facial, lingual, mesial and distal surfaces of a tooth.
Dentist should try and place pins in locations where they will be surrounded by optimum bulk of dentin and restorative material.



PRINCIPLES OF PIN PLACEMENT
 
 

Minikin pins placed in maxillary second premolar and restoration built over pins

ADVANTAGES

  1. Offer retention without the need for extensive preparation of tooth structure.
  2. May increase resistance form of the tooth preparation to some extent.
  3. Less time consuming and less expensive than cast restorations which require multiple appointments.

DISADVANTAGES

  1. Do not increase the strength of the overlying restorative material.
  2. Induce stresses in dentin in the form of cracks or craze lines, which may increase the potential for the fracture of tooth, micro leakage, pulpal damage etc.
  3. Increase the chances of perforation into pulp or on the external tooth surface.

Posts in Dentistry

As compared to pins the posts are thicker than the pins and are used in the root canals after root canal treatment where the tooth loss is extensive. In the root canal the post is cemented or screwed and above that core built up is done. After the core built up crown is given. Now many types of posts are available.

INDICATIONS

  1. Primary purpose is to retain a core in a tooth with extensive loss of coronal tooth structure.
  2. If an Endodontically treated tooth is to receive a crown.
  3. Pulp chambers are too small to provide adequate retention and resistance.

TYPES OF POSTS
1.    Active versus passive posts - Most active posts are threaded and are intended to engage the walls of canal, where as passive posts are retained strictly by the luting agent. Active posts are more retentive than the passive posts but introduce more stresses into the roots than the passive posts. Use of active posts should be limited to short roots in which maximum retention is needed.

2.    Parallel versus tapered posts -

  • Parallel posts are more retentive than tapered.
  • Induce less stress into the root.
  • Less likely to cause root fracture.
  • Have more success rate.
  • Tapered posts on the other hand require less dentin removal.


Parallel versus tapered posts
 

Tapered post on the left side and Parallel post on the right side

3.    Prefabricated post and cores
- are typically made of stainless steel, nickel chromium alloy or titanium alloy. They are very rigid, and with the exception of titanium alloys, are very strong. The main advantage is that they can be laced in the single visit and are quite economical as compared to the posts which are fabricated in the laboratory.

 3.	Prefabricated post and cores

Prefabricated screw post

4.    Custom cast post and cores- These have fallen from favour because they require two appointments, temporization, and a laboratory fees. Offer advantage in certain clinical situations like when multiple teeth require post and core, malaligned tooth, or tooth with minimal crown structure.
5.    Ceramic and zirconium posts- These are aesthetic posts that are white and/or translucent but are weaker than metal posts, so a thicker post is necessary, which may require removal of additional radicular tooth structure.
6.    Fibre posts- were more flexible than metal posts and had approximately the same stiffness as of dentin. Can be made up of Carbon, Glass, Quartz and Silicon.

How the Post Space is Prepared

-Preservation of radicular dentin is important.
-Gutta-percha can be removed with the help of heat or chemicals.
-Post length equal to 3/4th of root canal length or at least equal to the length of the crown is required.
-At the same time 4-5mm of gutta-percha should remain apically to maintain adequate seal.
-Post diameter should not exceed 1/3rd of the root diameter.

What can be Complications While Inserting Post

  1. Certain degree of risk to a restorative procedure.
  2. Procedural accidents may occur during post space preparation that includes perforation in the apical portion of the root or into the lateral fluted areas of midroot, so called STRIP

PERFORATION.
3.    Also increases the chances of root fracture and treatment failure. 
                                                                                                
For these reasons, posts should only be used when other options are not available to retain a core.

 

 User Comments on -  What Are Pins and Posts in Dentistry


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Posted By : Dr. Ritz on 30-Aug-2013 08:32 PM
Harry, If even after doing root canal treament, the teeth are constantly hurting, it is normal upto a week but if after that they are still hurting then you have to go to dentist and get xray done. There is possibility that root canal is not properly done and there is infection left or there is some fracture in the tooth or even the crowns can be high. So according to diagnosis the treatment will be needed. It can be re-root canal or crown adjustment.
 


Posted By : Harry Smith on 28-Aug-2013 09:09 AM
My dentist installed four gold pins into two large restorations for support, then placed caps on both, then decided it was necessary to root canal them. Now they both hurt constantly. Not sensitive to heat or cold. Just low grade pain in the root areas above gum line.
 


Posted By : Dr. Rtiz on 31-May-2013 08:00 PM
Ian, you have not written whether the tooth was restored before pulling out. There can not be any pin in that area. Either it is left out part of tooth or some foreign body which got stuck in that area. You can take second opinion as it is difficult to comment without clinical examination and xrays.
 


Posted By : ian on 31-May-2013 06:06 AM
under xray iv found out that thers some sort of pin or wire in my gum ware my wisdam tooth was ...but i want to know why its ther ....i should have been told .....
 


Posted By : Dr.Ritz on 14-Dec-2012 03:49 AM

Hi Therese,I think the correct answer would be d..medial of mand 1st molar

 


Posted By : Therese on 13-Dec-2012 06:15 PM
I need help bat this question regarding pins . The placement of retentive in the proximal regions of post teeth would mostly result in periodontal ligament perforation in the? A.medial of the mand 1st pm b. Distal of mand 1st pm c.distal of mand 1st molar d.medial of mand 1st molar
 


Posted By : tamer yosef on 16-May-2012 08:02 AM

I am realy benefitted

 


Posted By : Amira Rizk on 16-Sep-2011 09:54 AM
Thanns alot for these helping information
 


Posted By : Dr Ritz on 05-Sep-2011 05:37 AM
Pins and posts are given by the dentist in cases of teeth which are badly mutilated. Pins are given to provide strength to the tooth. If you have some badly mutilated tooth or tooth with loss of much of tooth structure, then the pins or post may be given to you by your dentist.
 


Posted By : MyungSub Kim on 05-Sep-2011 12:27 AM
I would like to purchase the dental pin. can you send to me the sample of dental pin by bia mail.
 

 
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