This study intends to provide information, under conditions resembling application, on
- the long-term stability of the cementation,
- the decementation behavior and
- the tendency toward microleakage (marginal gap formation)
of VarseoSmile Crown plus crowns under masticatory loads.
The 3D-printed crowns made of VarseoSmile Crown plus were cemented, i.e. adhesively affixed, to milled Trinia* stumps (by Bicon*, the elasticity modulus of the stump material of 18.8 GPa is comparable to that of natural dentin) using Variolink Esthetic DC* (by Ivoclar Vivadent*). There was no pre-treatment in which the inner surfaces were sandblasted.
This study design, based on clinical use, was subject to both a chewing simulation at 50 N load with 1.2 million chewing cycles (1.2 Hz) and 10,000 thermocycles (5°C/55°C) (corresponding to approx. 5 years in the mouth) and to a staircase simulation (significantly elevated requirements through gradual increase of the load force (with 50 – 80 – 120 N load), with 400,000 chewing cycles and 10,000 thermocycles (5°C/55°C) each time.
After the simulation, the cemented crowns were removed from the stumps. The force required to do so was measured and the damage profile was analyzed. In addition, the marginal gaps were inspected using micro computer tomography (µCT). The validity of the results was conclusively verified using a computer-based finite element analysis (FEA).
The values ascertained for all BEGO VarseoSmile Crown plus crowns fell within a very high range, which speaks in favor of a long clinical retention time.
- On average, the force of withdrawal without conducting a chewing simulation was approx. 800 N, and after a chewing simulation it was approx. 1000 N. These high values were determined after the chewing simulation at 50 N and after the staircase chewing simulation, demonstrating that the forces of withdrawal themselves fell within a high range and even increased with the duration of wear. From a clinical perspective, the application of such high forces could result in extraction of the tooth due to failure of the adhesive bond.
- The examined crowns displayed a resistance to fracture that was greater than the physiological masticatory forces.
- A decementation was not detected throughout the entire test sequence.
- Neither a lifting of the crown margins or washout of the luting composite from the marginal gap could be observed. The µCT showed that the marginal gap did not increase, the bonding area was not damaged, and the crowns did not shift due to mechanical load, in any of the tested cases.
- The FEA analysis demonstrated that no clinically relevant tensions or deformations were detectable or to be expected in the crown margin area, for crowns made of VarseoSmile Crown plus. This result promises a stable, durable margin closure.
The present studies provide evidence that 3D-printed crowns made of VarseoSmile Crown plus do not exhibit a tendency toward decementation, i.e. a loss of composite material or marginal gap formation, when using commercially available, dual-curing luting composites (e.g. Variolink Esthetic DC).
µCT image: No washout of adhesive in the crown margin area
FEA analysis with visualization of the very minor deformation load in the crown margin area
The above information is based on a scientific study of the decementation behavior of VarseoSmile Crown plus, conducted by:
Prof. Dr. Jan-Frederik Güth, ZT Josef Schweiger, M.Sc., Dipl. Ing. Dr. Kurt-Jürgen Erdelt; Department of Prosthetic Dentistry, University Hospital, LMU Munich, Germany
* This symbol is a commercial designation/registered trademark of a company which is not part of the BEGO company group.