ALTHOUGH dentists speak of permanent fillings, crowns, and bridges, it must be remembered that the only permanent thing we do is extract teeth. When you consider that teeth are subjected to great chewing forces, to acids in foods and drinks, to rapid temperature changes, to brushing abrasion, to attrition and erosion, and to attack by bacteria it is a wonder that any restoration lasts more than a few months. Yet most of the composite or plastic (silver amalgam) fillings will last over 10 years, and crowns and bridges that are properly made will last 15 years or longer. Bonding and veneering will also last many years, but they are most subject to wear and fracture than a well-constructed crown.

The big disadvantage of veneering over crowning is based on the Hippocratic mandate for a doctor to do the least possible harm. Veneering requires very little alteration of the natural tooth. Sometimes a composite veneer requires only etching prior to application. More often a small amount of enamel is removed to reshape the tooth.
Although etching sometimes makes teeth sensitive, the risk of irreversible nerve damage is small, and re-veneering can be done with minimal additional trauma. Not so with a porcelain crown. If the nerve is damaged by over grinding or if the crown is done poorly and gum line decay penetrates to the nerve, root canal therapy becomes necessary; if that fails, the tooth is lost. Also, each time a tooth is recrowned, it is subjected to more grinding and new potential nerve injury and degeneration. That is why I never do porcelain crowns nor do I recommend that.

The disadvantages of veneering relate to colour stability, physical strength, and irritation of the gum. Composites and plastic tend to discolour when exposed to sunlight. The outer surface will inevitably wear, and as it does, it becomes dull. But as noted above, the veneers can be redone easily. Porcelain veneers are colour stable because the colour is fused into the ceramic material, but porcelain is more fragile than composites and plastics and can fracture under a heavy bite.

Composite resins are best used to restore fractured and worn incisal edges of upper front teeth but are prone to failure when used on the lower front teeth. The reason is that the upper incisal edges overlap the lower teeth and are not subjected to excessive pressure. The incisal edges of the lower teeth jut up, into, and against the hard inner surface of the upper teeth on swallowing, chewing, grinding, and clenching. Restoration of these surfaces with composite resins cannot be expected to last long.

No matter how good the veneer, it is a foreign substance, and when it contacts the gum tissue, the body treats it as such. Even if thin, it is still likely to thicken the tooth slightly since a certain amount of material bulk is essential for strength and colour. When the tooth is thus thickened, the gums often become red, puffy, and bleed easily – marginal gingivitis – or the tissue may actually be stimulated overgrowth – hyperplasia. Thus, an attempt at improved appearance may result in impaired unsightly gingival tissue. The cure for minor irregularity or discoloration of teeth may not be worth the disfigurement it may create. Before deciding on any of these esthetic procedures, be sure you are dealing with a problem serious enough to warrant a dentist’s intervention.

As a rule, dentists do not guarantee their work. Guarantees are both unethical and impractical since success is dependent not only on the dentist’s skill but also on the patient’s response to treatment. Nonetheless, most dentists back up their work with an unwritten guarantee of sorts. If for example, a filling falls out within a few days or weeks of placement, a dentist usually replaces it free of charge. This should happen only rarely in a good dental practice. If a more costly service such as a porcelain bridge fails in a short time, many dentists adjust the fee for replacement even if the failure had nothing to do with the quality of original work. As an act of goodwill, the fee may be reduced significantly or the laboratory cost alone passed on to the patient.

Since veneering is so expensive, you should ask about your own dentist’s policy regarding early failure. Some dentists redo the veneers at 50 percent of the original cost if the need arises within a couple of years. Or you might be charged only the laboratory fabrication cost. Though dentists are not obliged to guarantee the results of their work, and should not be expected to, most have a goodwill policy in the event of early treatment failure. My own policy towards my patients is based on what I would like for myself if I were the patient. But generally, just what this policy is may be a factor in choosing between one dentist and another.