Retentive Pins:
These are Pins which are used to improve the retention of the restoration. Pins retain the restoration in position and and hold the restoration and prepared tooth structure together and they also the tooth by Cross-Splinting of Weakened Cusps.
Placing of Retentive pins should be planned and there are many factors to be considered in Retentive Pin placement in Amalgam Restorations, here we are going to list out the basic and must properties on which Number of Retentive pins, Retentive Pin Site, Orientation, Diameter, Size, Interpin distance and Depth are decided.
Number of Pins required:
- One Pin per missing cusp or One pin per missing axial line angle of tooth
Site or Location of Pin to be placed depends on the following factors:
- Should be halfway between the pulp and dentinoenamel junction/external surface of the tooth
- There should be at least 1.0mm of sound dentin around the whole circumference of the pin
- Pin should be located no closer than 0.5mm to the dentino-enamel junction to avoid crazing of enamel
- Dentin thickness around each pin should be atleast 2.5 times the diameter of the pin hole
- Pin placement should be such that atleast 1 mm of Dentinal thickness is present between Pulp and the Pin
Pin Orientation depends on:
- Pin should be oriented parallel to the long axis of the tooth
Pin Diameter depends on:
- The amount of Dentin available
- Overall Size of the concerned Tooth
- Amount of Retention required
Pin Length depends on:
The Pin Length is seen separately in Dentin and in Restorative material.
- Cemented Pins: 3mm in Dentin and 2mm in Restorative material
- Friction locked Pins: 3mm in Dentin and 3mmin Restorative material
- Threaded Pins: 2mm in Dentin and 2mm in Restorative material
Inter Pin Distance depends on:
- Cemented Pins: 2mm
- Friction Locked Pins: 4mm
- Minikin threaded Pins: 3mm
- Minim threaded Pins: 5mm
About The Author
Varun Pandula
I am Varun, a Dentist from Hyderabad, India trying my bit to help everyone understand Dental problems and treatments and to make Dental Education simplified for Dental Students and Dental fraternity. If you have any doubts feel free to contact me or comment in the post, thanks for visiting.
Hi Dr. could you tell me in which interproximal region in a posterior teeth is more probably caused periodontal ligament perforation?
What exactly do you mean by Periodontal Ligament perforation? And which treatment are you referring to will be leading to Perforation?
hi,can u please tell me whether self-threaded pins need to be placed on a flat surface?
Pin holes should be places on flat tooth surface to increase the amount of amalgam condensed around the pin. By placing on flat surface you can engage the tooth completely thus giving more retention.
Hi doctor could you tell me if after a procedure where pins were placed in are they supposed to be visible in the tooth. I can see the matalic
No, they should not be visible as it will give a dark visible tint on the Crown when placed.
Can u please tell me the reference for this concepts?
It is taken from – Sturdevant’s Art and Science of Operative Dentistry textbook and my personal notes from my college days.
Hi doctor can you tell why it should be place parallel to long axis of the tootj
To bear the Occlusal forces without fracturing the tooth. If it is placed at an angel it will tend to bear unwanted forces and lead to fracture of the tooth.
a dentist just placed a pin in front tooth he went thru tooth and is now sticking out under gum line he says he should leave it should i do this ?
Is the Pin visible through the gum or is it sticking out from the Gum? Retentive Pins are usually surrounded by sound tooth structure to help the tooth attain strength. If the pin is visible though the gums it needs to be addressed. I can have a clear picture if I can see an pictures of it, if possible you can mail the images to juniordentist@gmail.com, I can have a look and give you a much better suggestion regarding the condition.
Where do you find out all of the rules and guidelines for pin placement?
I saw a case where I think the pines were placed too close from another dentist. Can you evaluate it for me please to express your opinion and how to fix this? The patient is having sensitivity and refuses to go back to the other dentist. Is it cracked possibly?
Do you have an X-ray or a clinical pic
Yes, I will e-mail you :-)
Yes, I will e-mail you the xray :-)
Thanks
Hello Doctor,
If a large filling falls out of the tooth ( not the first time ) is it possible to restore the tooth using retentive pins. I don’t know anything about the subject, but common sense tells me
it should be possible, like reinforcing supporting rods with cement on a construction site.
Perhaps this is not the best comparison, but I think you know what I mean.
I am not suggesting pins and crowns but a basic restoration.
I would appreciate any comments you might make on this. Thanks.
If the filling has fallen out and the cavity is large it is best to go for a Crown placement as it protect the remaining tooth structure. In case of previously filled teeth with a lost restoration the remaining tooth structure will be weak and the best possible solution is to replace with a crown. If the remaining tooth structure is strong enough to support a new restoration then it can be done using the above mentioned method of placing Retentive pins.
The comparison which you have given is probably the closest you can get to it.
Thank you for your reply. I appreciate it.
Because of your article about pin retained Amalgam Core Restoration, I was prepared to ask my family dentist about using this procedure for a restoration. He was receptive to the idea, took X-rays of that part of my mouth and proceeded. I am confident he did a great job.
Thank you for posting a brief article on the subject.
I used pin retained self threading to reinforce 4 quadrants of molars . Once the amalgam was used to build back the crowns the patients occlusion was restored. Going forth ultimately full crown restoration is ultimately anticipated for mor prolonged service with the pin restored amalgam restorations as supporting abutment bases
Hi doctor, where the retention pin in amalgam restoration should be placed?
Is it parallel to the outer wall or parallel to the long axis of the tooth ??
They should be placed parallel to the long axis of the teeth as the forces need to be dissipated on the tooth and in case the pins are at any other angle they will tend to cause a fracture line.