Predictable and precise tooth preparation techniques for PLVs in complex cases
Galip Gurel discusses all the steps taken for using porcelain laminate veneers in difficult circumstances.
When it comes to restoring the mouth with porcelain in order to improve the aesthetics, the PLVs are one of the most conservative and aesthetic techniques that we can apply. The longevity of the veneers are quite long and durable especially if the right indications are chosen and the correct techniques are applied (Horn 1983). The main idea in any restorative case is to keep it simple and concentrate on one idea which is the conservation of the sound tooth structure.
The dentin-enamal junction (DEJ) where they get together is very important in the structural strength of the tooth. The explanation lies in the most fascinating feature inherent to the natural tooth-a complex fusion at the DEJ, which can be regarded as a fibre-reinforced bond (Lin et al 1993). Because when we limit our preparations on enamel, the tooth will not flex and it will stay as rigid as a tooth can be (Magne and Douglas 1999). Even if our preparation line passes through the DEJ margin and enters into dentin, it won’t create a major problem for minor invasions. However, if we end up finishing our preparation on large amounts of dentin, we very well may end up with other kind of problems. This will not only create complex bonding issues on dentin, but will also free the ‘flexing’ factor on the tooth structure. Over preparing the rotated or aggressive preparation of protrusively placed teeth will cause us to end up in the dentin structure which will lower our bonding values as well as causing the flexing of the tooth structure. When we end up in the dentin structure, it’s not only lowering our bonding values (Noack and Roulet 1987, Van Meerbeek et al. 1996,1998) but it also causes the flexing of the tooth structure. And when the tooth starts flexing, a different phenomena occurs as this situation. First of all, we have the tooth which is aggressively prepared that wants to bend, to flex, and on top of it we’re bonding a veneer, a porcelain material, which is very rigid and in between those two structures we’ll be using the adhesive luting resin which will stay in between and will try to absorb all the stresses. If the tooth receives some different occlusal forces and keep on flexing, the luting resin at the margin will start peeling off slowly. So at these situations we will most probably end up with some micro-leakage or de-lamination.
In order to minimise those effects and problems, we have to be very precise and careful about case selection and tooth preparation (Besler et al 1997). The ideal cases which we would want to place the veneers are when the teeth are aligned perfectly on the dental arch and maintaining their original facial volumes which means that the facial structures of the teeth isn’t worn as it happens by ageing. That means, we exactly need to remove the tooth structure equivalent to the thickness of the veneer that we will be placing on the tooth itself. For that reason we can simply use our standard tooth preparation techniques (Figures 1a-c).