CDA Essentials 2019 • Volume 6 • Issue 7

47 Issue 7 | 2019 | S upporting Y our P ractice Theviewsexpressedarethoseofthe authoranddonotnecessarilyreflect theopinionsorofficialpoliciesofthe CanadianDentalAssociation. Preoperative (1) and postoperative (2) image of a series of veneers cemented on the anterior teeth. According to Dr. Carvalho, “Veneers are an excellent option to improve the shape and colour of anterior teeth, but the wrong choice of cementing resin can compromise the results over the long term.” When selecting the type of resin cement to use when applying veneers, there are many factors that dentists should consider: retention, support of the brittle veneer, solubility and wear over time, and colour stability of the resin cement. Dr. Ricardo (Rick) Carvalho of the University of British Columbia addressed these aspects in an interview on CDA Oasis, although he focused on what he believes is the most clinically relevant question: “Why are veneers changing colour over time?” According to Dr. Carvalho, in order to understand colour change (i.e., darkening or turning yellow over time) when cementing veneers, dentists should consider the presence of amines in the resin cement and how they directly affect the colour over time. “Typically, a dual-cured resin cement undergoes two types of polymerization: self-curing and light-curing. Because of these two routes of polymerization, dual-cured resin cements contain aromatic tertiary amines, as well as a camphorquinone (CQ)-amine photoinitiating system for the polymerization or the light activation for the light curing mechanism,” says Dr. Carvalho. “It is actually these amines that may become yellow over time and contribute to the discoloration of the veneers.” Other factors may play a role in the colour instability of veneers, but certainly the presence of aromatic tertiary amines in the resin cement is an indication that the material may change shades over time. “We can improve colour stability by always choosing a light-cure only resin cement for cementing veneers. Aromatic tertiary amines are not required in light-cured resin cements and, therefore, they are more colour stable over time,” he says. “Alternatively, one can choose a new generation dual-cured resin cements that use an amine-free initiator system. Amine-free resin cements are relatively new, yet despite their novelty, the results for colour stability are promising.” Dr. Ricardo M. Carvalho Dr. Carvalho is a professor in the department of oral biological and medical sciences, division of biomaterials at the University of British Columbia (UBC). Veneer Discoloration: Can it be avoided? ➋ ❶