Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

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Mineral trioxide aggregate
Although not an inter-appointment medicament, mineral trioxide
aggregate (MTA) is an innovative material that appears to induce 
the formation of new bone and is used for perforation repair. Root
perforations are an unfortunate recognised hazard associated with
endodontic treatment and post-space preparation. The communica-
tion is likely to stimulate an inflammatory response and consequent
resorption in the adjacent bone. It is therefore important to seal the
defect as soon as possible. This is achieved by placement of a pellet 
of MTA cement over the defective site and by dressing the tooth. At 
a second visit, the temporary material is removed and the MTA is
checked to ensure that it has set. The canals may then be obturated
conventionally and the tooth kept under clinical and radiographic
review.
OBTURATION (ROOT FILLING)
Rationale
The pulp space of a non-vital tooth is a potential reservoir for the 
stagnation and degeneration of tissue fluids to occur, and may act 
as a source of initiation and maintenance of periapical disease. If 
these stagnant and necrotic substances are contaminated with micro-
organisms there is a potentially inaccessible source of persistent and
progressive disease. To prevent this from happening, complete, three-
dimensional obturation of the cleaned and shaped root canal with an
impervious filling should be carried out to seal off communication
between the pulp space and periodontal membrane.
Objectives
The objectives of filling, or ‘obturating’, the canal space are:
• To prevent percolation of peri-radicular exudates into the pulp
space via the apical foramina or lateral canals.
• To prevent proliferation and spread of micro-organisms from the
canal into the surrounding tissues.
• To seal the canal from coronal leakage.
• To encompass any residual bacteria.
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Sealers
Gutta-percha is the most commonly used root canal filling material
but does not adhere to dentine. Warm gutta-percha may contract away
from the root canal walls, leaving a potential space into which fluids
may percolate. There is therefore a need to use a sealant material that
bridges the gap between the filling and the walls of the canal and fills
any potential spaces into which micro-organisms may proliferate.
A sealer may fulfil any one or more of the following functions:
• Acts as a luting agent
• Fills any discrepancy between the canal walls and core material
• Fills any discrepancy between gutta-percha points
• Acts as a lubricant
• Acts as a bactericidal agent
• Fills any lateral canals
Requirements
A sealer should have the following properties:
• Be capable of achieving a thin film
• Have high tissue tolerance
• Be of uniform consistency
• Have good rheological properties
• Be of low solubility
• Have an adequate working time
Groups
There is a variety of sealers available, and these may be simply split
according to their constituents:
• Zinc oxide based
• Calcium hydroxide based
• Resin sealers
• Glass-ionomer sealers
In the initial setting phase, sealers may be cytotoxic; hence, overexten-
sion of the sealer beyond the confines of the canal should be avoided.