Saturday, September 10, 2011

OPERATIVE TREATMENT OF PRIMARY TEETH....A NOTE

Pit and fissure caries

Pit and fissure caries is less of a problem in primary teeth than in permanent ones. The fissures are usually much shallower and less susceptible to decay, so the presence of a cavity in the occlusal surface of a primary molar is a sign of high caries activity. Because of this it is quite likely that the children who require treatment of these surfaces will be young. However, treatment is not difficult and can usually be accomplished without problem. Infiltration analgesia should be given together with supplemental intrapapillary injection. Caries is removed using a 330 bur in a high-speed handpiece. For restoration although, as indicated above, silver amalgam has not so far been bettered in clinical trial because occlusal caries in the primary dentition indicates high caries activity, the material of choice may be a resin-modified glass ionomer cement with its possible caries preventive properties.



Approximal caries

Silver amalgam

Failure of amalgam itself as well as faults in the cavity design have been the most commonly reported causes of failure of approximal restorations in primary teeth. Attempts to overcome these deficiencies and to improve durability have come through alteration in cavity design and the choice of material used. A reduction in the size of the occlusal lock, rounded line angles, and minimum extension for prevention all result in less destruction of sound tooth tissue. In addition, the 'minimal' approximal cavity with no occlusal 'dovetail' has been described for both amalgam and adhesive restorations, and incorporates some mechanical retention in the form of small internal resistance grooves placed with a very small round bur just inside the enamel-dentine junction.

It is unlikely that the 'perfect cavity design' exists for an amalgam restoration in primary molars due to certain anatomical features:

1. Widened contact areas make a narrow box difficult to achieve.

2. Thin enamel means that cracking and fracture of parts of the crown are more common.

3. Primary teeth may undergo considerable wear under occlusal stress themselves and this in turn will affect the restorations.

It is therefore necessary to investigate other materials for use in restoring the primary dentition.

Composite resin

Composite resin has been used quite widely to restore primary teeth and results are generally acceptable. Cavity design is usually a modified approximal design with bevelling of the margins to increase the amount of enamel available for etching and bonding.

The use of rubber dam is essential if a dry field is to be achieved. This fact together with the material's relative expense probably reflects the lack of widespread use of composite resin in many countries.

Glass ionomer cement

More studies have been conducted using glass ionomer cements than composite resins. However, the cavity designs used in the different studies vary considerably and it is difficult to draw firm conclusions. Certainly, glass ionomer cement will undergo significantly more loss of anatomical form than amalgam in the approximal area, and as such conventional glass ionomers have not been shown to be as durable as amalgam. However, the operator will need to balance this fact with the obvious mechanical and chemical advantages of the cement namely its ability to bond to enamel and dentine, thus requiring a more conservative preparation, and its ability to act as a reservoir of fluoride.

Compomers

Compomers are now widely used in general dental practice for the restoration of approximal lesions in primary teeth. After good initial results, longer follow-up periods have shown that this material indeed lived up to its early promise and good survival rates have been reported for restorations in primary molars. However, it must be placed in cavities prepared to the usual principles of cavity design for a most favourable outcome.

Stainless-steel crowns

Stainless-steel crowns should be considered whenever posterior primary teeth (especially first molars) require restoration. They were originally developed to provide a 'restoration of last resort' for those teeth that were not salvageable by any other means. At the time that they were introduced in the early 1950s the only alternatives were silver or copper amalgam or a selection of cements, materials completely unsuited to the restoration of grossly carious teeth or those that had been weakened by pulp treatment. Over the years, it has become apparent that the life expectancy of these crowns is far better than any other restoration for primary posterior teeth and that they come close to the ideal of never having to be replaced prior to exfoliation. In addition, they are less demanding technically than intracoronal restorations in primary teeth.

They should therefore now be considered for any tooth where the dentist cannot be sure that an alternative would survive until the tooth is lost. It is unfair to put a child through more treatment situations than necessary because a less successful material, which needs frequent replacement, was chosen.

Anterior teeth

The treatment of decayed primary incisors depends on the stage of decay and the age and co-operation of the patient. In the preschool child, caries of the upper primary incisors is usually as a result of 'nursing caries syndrome' due to the frequent or prolonged consumption of fluids containing fermentable carbohydrate from a bottle or feeder cup. The lower incisors are rarely affected as they are protected during suckling by the tongue and directly bathed in secretions from the submandibular and sublingual glands. In 'nursing caries' the progression of decay is rapid, commencing on the labial surfaces and quickly encircling the teeth. It is impossible to prepare satisfactory cavities for restoration and after a comprehensive preventive programme the most suitable form of restoration is the 'strip crown technique'. This utilizes celluloid crown forms and a light-cured composite resin to restore crown morphology. Either calcium hydroxide or glass ionomer cement can be used as a lining and the high polishability of modern hybrid composites make them aesthetically, as well as physically, suitable for this task.

In older children over 3 or 4 years of age new lesions of primary incisors, although not usually associated with the use of pacifiers, do indicate high caries activity. Such lesions do not progress so rapidly and usually appear on the mesial and distal surfaces, here a glass ionomer cement or composite resin can be used for restoration. Glass ionomer lacks the translucency of composite resin but has the useful advantages of being adhesive and releasing fluoride.

Fractures of the incisal edges in primary teeth, as in permanent teeth, should be restored with composite resin.

Strip Crowns (3M ESPEE) are a useful aid in the restoration of primary incisors. Unfortunately, owing to their low sales in the United Kingdom and the rest of Europe, the company has discontinued the sale of these crowns and now they are only available on special request. They are however, freely available in the United States. In the authors opinion, these crowns are excellent for building primary incisors where extensive tooth tissue has been lost due to either caries or trauma. The technique for their use is similar to that of such crowns used in permanent teeth; the crowns are easily trimmed with sharp scissors, filled with composite, and seated on a prepared and conditioned tooth. The celluloid crown form can be stripped off after the composite has been cured. 

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