Clinical Longevity of Ceramic Laminate Veneers

Overview

Rationale: Survival rates of teeth with laminate veneers were reported to have more marginal caries and discoloration when existing restorations are present. However in these studies no conditioning of the existing restorations was performed. Objective: This study evaluate the survival rate of ceramic laminate veneers bonded to teeth with and without existing composite restorations Study design: Prospectief Cohort research Study population: the participants received laminate veneers and older then 18 years. Intervention (if applicable): The participants received laminate veneers in the past. No intervention. Main study parameters/endpoints: Survival and success of laminate veneers with existing restorations: Survival (no loss of laminate veneer during follow up time), Success was measured using USPHS health criteria. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: The participants are asked to come for a check-up of their restorations, the investigators will evaluate the laminate veneers by sight and take some light photo's and a patient questionnaire will be given.

The use of ceramic laminate veneers as opposed to metal-ceramic or all-ceramic full-coverage crowns is a minimal invasive treatment option in reconstructive dentistry. Since their retention relies solely on adhesion, durable adhesion of resin luting cements to both the enamel/dentin and the cementation surface of the ceramic is crucial. Luting cements used in conjunction with phosphoric acid etching followed by adhesive application on enamel show reliable adhesion with mean bond strengths up to 40 MPa. Also, etching the intaglio of glass ceramic veneers with hydrofluoric acid followed by silane coupling agent application delivers bond strength values similar to or higher than to enamel. Even after long-term water storage and thermocycling aging conditions, promising results were reported with resin-ceramic adhesion. Ceramic laminates are indicated not only to restore malformed, malpositioned, or discolored teeth where mainly the substrate is the enamel and/or dentin but also in situations where resin composite restorations are present on the tooth to be restored. In case of secondary caries, severe marginal or surface changes, it may be necessary to remove such restorations. On the other hand, degradation of polymers in the aggressive oral environment may decrease the free radicals available on the resin surface that may eventually decrease the adhesion of resin cements to such composites. However, limited information is available on the survival of ceramic laminates on such existing composite restorations where mainly fractures and marginal defects were reported. Defects were especially noticed at the locations where the existing fillings were present. In fact, today, advances in surface conditioning methods and adhesion promoters enable durable composite-composite adhesion. Among numerous other methods, several studies reported increased composite- composite bond strengths after conditioning the composites with alumina or alumina-coated silica particles followed by silanization. The process of silanization promotes the wettability of the substrates and further reacts with the glass particles present on the composite surface forming covalent bonds. Composite- composite bond strength simulating aging after silica coating and silanization was reported to deliver significantly higher bond strengths (46-52 MPa) than conditioning the composite substrate with phosphoric acid and adhesive resin application only (16-25 MPa). Unfortunately, the previous clinical studies did not report application of any surface conditioning method prior to cementation of ceramic laminates. In clinical practice, the clinical dilemma is whether or not to remove the existing composite restorations with no indications of caries or acceptable surface degradation that could be refinished and repolished. Alternatively, full-coverage crowns are indicated on teeth with large composite restorations that require more tissue removal yielding to preparations in dentin that is a substrate less favorable to bond onto than enamel. The objective of this prospective clinical study is to evaluate the performance of ceramic laminate veneers bonded onto either intact teeth or to teeth with existing composite restorations with no indications of caries, ditching, or marginal staining. The null hypothesis tested is that the presence of existing composite restorations would not decrease the survival rate of ceramic laminate veneers compared to those bonded onto intact teeth.