Restorative dentistry (Proceedings)
Restorative dental problems, although not as involved as those in human dentistry, can be very technique-sensitive and difficult to resolve. The resolution of particular problems is usually dependent upon the choice and imagination or inventiveness of the operator. Restorative problems are usually those of a mechanical or iatrogenic nature rather than medical or pathological. The restoration of the coronal aspect of endodontically treated teeth, with carious lesions, coronal defects, and missing teeth constitute the bulk of restorative problems.
Complete texts have been written describing the many materials used in dentistry, their strengths, failings, and applications. Dental materials are constantly evolving in use, effectiveness, and variety. Some basic materials employed over the past two decades are still in use, and quite effective. Dental materials of choice for animal dentistry are composites; chemical and light cured varieties, glass ionomers and silver amalgam.It must be remembered that there is no strength to be gained from most dental restorative materials. The opposite is quite often true, for sound tooth structure is removed to achieve mechanical retention of some composite restorations and silver amalgam. Glass ionomer cements do not require mechanical retention, however they lack resistance to abrasion, and like all restoratives, they do not lend themselves to sheer strength when lateral force is placed upon them. Therefore, lost tooth structure incisal to the remaining tooth crown cannot be replaced with existing dental materials; they will invariably fracture.
Problems encountered in the use of dental materials are usually the result of poor technique, lack of familiarity with the properties and uses of the various materials, improper instrumentation, and failure to follow the manufactures instructions in a step-by-step manner to completion.
There are many publications available to the veterinarian from the manufacturers detailing in total all the properties of their products, their applications, instrumentation, and an atlas detailing step-by-step procedures.
The most common problem in veterinary dentistry is the use of glass ionomer cements to restore cervical line resorptive lesions in cats. Failure usually is the result of poor visibility, gingival hemorrhage contaminating the area, and poor restorative technique. Cats with resorptive lesions should have a thorough prophylaxis at 10 to 12 day prior to restorative procedures. The removal of dental plaque and inflammatory agents will help to control hemorrhage during restorative procedures.
A fine gauge gingival retraction chord placed in the gingival sulcus prior to restoration retracts the gingiva, providing better visibility while controlling sulcular bleeding.
A glass ionomer restorative material of choice is placed into the lesion as per the manufacturer's instructions, and finished to proper anatomic contour. It is best to complete the restoration with the retraction chord in place until completion. If the retraction chord tends to block visibility to the lesion, it may be removed just before placement of the restorative material. The hemostatic agents in the chord usually will have retracted the gingiva for visibility, while providing sufficient hemostasis to place the restoration before moisture contamination.
Proper attention to finish is essential. The restorative material must not have overhanging ledges, or a roughened surface that can provide plague retentive areas. A smooth, polished finish can be had with the use of fine sanding disks, and special finishing rubber cups and wheels available from all dental supply houses.
Many restorative procedures fail because of poor cavity design. The mechanics of cavity preparation must be adhered to. Cavity design basically is the removal of caries, if present, and any unsupported enamel, while providing mechanical retention for the restorative materials. The use of adhesive materials can eliminate the need for mechanical retention.
There is no stereotypical design of cavity preparation. Each is designed with the specific purpose of the elimination of caries, restriction of resorption, reduction of sensitivity (in the case of feline root resorption and sensitivity), and to restore coronal anatomy.
Each restoration is designed to perform the additional steps necessitated by the limitations of the operator or restorative material. Poor preparation accounts for the majority of restorative failures.
Clinicians are advised to review human restorative dental publications to familiarize themselves with the principals of cavity preparation and design. Cavity marginal integrity, gingival extension of the restoration, unsupported enamel rods, and restoration evaluation all play an important role in achieving success.