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sushantpatel_doc's picture
Joined: 30 Nov 2009

Passive, Parallel, Pillar like Metal Post – Clinical Approach

One of the important stages in endodontic therapy is to restore the tooth with a stable restoration for mastication and aesthetic purpose.
Post & core helps to restore the tooth to the normal anatomy.
Every tooth which is endodontically treated need not be treated with a post. Main function of the post is to give retention to the core. It does not strengthen the tooth. Whenever clinician feels that coronal filling is not having sufficient retention, one can opt for post. There is no clear-cut clinical guideline to decide the indication for post. But many a times more than approx 30%to 40% destruction needs a post.

Achieve Coronal seal: - as early as possible.(within 1 to 3 months).
Ferrule effect is mandatory - for resistance and retention form.
Crown margins should end 1 to 2 mm below the core material or on a sound tooth / root structure.
Passive, parallel design is the best.
Threaded – tapered design is disastrous.
Cast posts are the best but the procedure is technique sensitive & dependent on impression procedure and laboratory.
Post which compensates the anatomical coronal flare is recommended.
Amalgam could be the best alternative to improved composite Resins in subgingval destruction.
Cementation of the post – post design / length is the key to success. Luting cement can be zinc phosphate / flowable composite resins or dual cure cements.
Clinical success of the post depends on length, size, design & ferrule effect.

Metal Post woes –

Aesthetics - Cast post is highly objectionable esthetically but prefabricated post are used with core buildup materials. So one can mask metal post by opaquer.

Fracture of the root - Inappropriate tapered post leads to root fractures, thus parallel post are preferred. Parallel design distributes uniform pressure on the root. Thus preventing root fracture.

Indications of the Post –

Clinicians Desire:- whenever coronal filling needs additional retention, one may decide to place a post.
One may decide according to the tooth structure available after removal of entire carious lesion
One may decide after anticipating the amount of tooth structure that would be available after crown preparation.
Abutments of F.P.D. & R.P.D.s,
Mandibular incisors
Teeth having cervical cavities
If destruction of the tooth is more than 30% to 40%

Selection of the canal –

Canal closest to the destruction.
Largest canal of the tooth.
In case of multiple cuspal destruction, one may place post in more than one canal.
One should not select curved canals. All post should end at curvature.
One should not select canals with questionable prognosis (canals with sealed perforation/ separated instruments should be avoided).

Size of Post –

To select the size of post - select the size of peeso that fits without resistance.
Please check manually whether Peeso is making full turn.
One may practically place the selected post on the radiograph of the indicated tooth to confirm the approximate size (atleast 1mm of root dentin thickness should be available around the post).

Length of post –

Ideal post length must be more than 2/3rd the tooth length (more than ½ the root length).
Measure tooth length i.e from cusp tip to root apex (W.L). Calculate 2/3rd of this length and add 2 mm.
One should avoid to put post in the apical 4mm of area. Post length = WL – 5mm.
Post should end at 4mm below the bony crest in periodontally compromised case.

Compensation of anatomical coronal flare –

Every canal has a natural /anatomical coronal flare which needs to be compensated by the post
Every passive parallel post that is selected must have a ring or tier that fits at the flared coronal area to compensate for the coronal flare of the root.
In case of cast post the anatomical coronal flare gets compensated by the casting, which is made by taking an impression of the anatomical coronal flare.
If you compensate the natural anatomical flare, these posts can withstand masticatory forces better. (Metal post can withstand masticatory force & is choice of the material. Castpost are the best but are technique sensitive.
If anatomical coronal flares is not comperreted, due to masticatory load, cement around Post will breakdown and leads to loosening of the Post.

Clinical procedure for placement of passive post –

Use peeso drill # 1 to remove the Gutta Percha.
Use peeso drill to see which peeso fits in the canal space and accordingly matching i – post is selected.
Peeso is taken till calculated post length in the canal.
Overused Peeso drills are not recommended for preparation of posthole.
Try the post. Initially it will be loose and the flare will be away from the anatomic coronal flare.
Cut or trim the post using the airotor till the flare matches with the anatomical coronal flare. Cut the post till it becomes firm and steady. Take a radiograph to confirm the length.
If the Post is too ‘tight’ in the canal then reduce the flare with the help of airroter.
Use any cementing material to cement the post e.g. - Zinc Phosphate or dual care cements.
Use opaquer to mask the metal if required.
Use any core build up material (silver amalgam or contrast coloured composite) and seal the coronal cavity.
Build the normal contacts and cuspal forms.

This post has a peculiar design which compensates the anatomical coronal flare of every canal. This anatomical coronal flare, if not compensated, may lead to loosening of the post and ultimately failure of the treatment. This post is of parallel & passive design, which prevents fracture of the root under mastication. i-post is made up of surgical grade stainless steel alloy in three sizes matching with # 2, # 3, # 4 & # 5 peeso drills.

Benefits of i – post –

100 % indigenous – Indian
Prefabricated – ready to use
Inbuilt flare to compensate anatomic coronal flare.
Strong – solid metal
User friendly – matches with peeso drill # 2, # 3, # 4 and # 5.
Pointed tip and easy identification
Readily available
Economical, Rs. 120/- per Post
Stable – due to design
Better prognosis

Please Note :-

Clinical success of the post depends on size, length, material & ferrule effect.
Avoid using # 3 peeso reamer in mesial roots of mandibular molar & buccal roots of upper molars.
Overused Peeso drills are not recommended to prepare posthole.
Use opaquer for masking metal head.
Use conventional contraangle Handpiece at speed 5000 to 10,000 RPM for removal of Gutta Percha while preparing posthole.

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