IVOTION – IMPRESSIVE DIGITAL DENTURE SYSTEM (PART 2)

Bonding

This is what makes Ivotion so unique: The bond between the tooth and gingiva material is established without using an adhesive additional component. Both materials are polymerized together in a single process step, comparable with the production of multi-layer prefabricated teeth for removable dentures. In other words, this is a direct chemical bond. As a result, the Ivotion disc can be termed a monolithic material. The material transition runs precisely through the entire Shell Geometry, specific to the respective location. This attribute is critical to the esthetics of the dentures milled from it.

Fig. 2: The REM image shown here (at 150x magnification) shows the homogenous transition between the tooth and gingiva material, which makes Ivotion a monolithic material.

Evidence of the material bond based on shear bond strength in accordance with ISO 10477:2018

Shear bond strength (or shear bond strength test) is a widely established method that is used in particular to demonstrate bonding in the case of crown and bridge materials as well as tooth and denture resins with characterization materials. Accordingly, it also played a key role in the development of the entire Ivotion Denture System.

The standard is met if at least a shear bond strength value of 5 MPa is achieved. An additional internal requirement is a cohesive fracture pattern. This means that the fracture occurs in the material rather than in the bonding area. High measured values and fully cohesive fractures are evidence of a strong material bond.

Fig. 3: Setup of the shear bond strength test. The images show the test equipment set up in accordance with the specifications of the standard, with the test specimen secured using the screw (A) and positioning aid (B). The slider (C), set at an exact distance to the test specimen, shears off the cylindrical part of the test specimen as the load increases, which can cause different types of fractures to occur.

Methodology

In this test, material in the form of a cylinder (∅ 5 × 6 mm) is attached to a base plate measuring 5 × 10 × 15 mm and polymerized, in accordance with the standard. A load is then applied to the polymerized cylinder in a standardized device until they fracture. The load to fracture and the cross-section of the cylinder are then used to calculate the bond strength (shear bond strength in MPa). In addition, the fracture pattern is evaluated and classified into cohesive and adhesive fractures. In the case of Ivotion, the test can only be carried out in reference to the ISO standard, as the test specimens are sourced directly from the milling blank (see Figure 4).

On average, the Ivotion samples achieved values of over 30 MPa while demonstrating only cohesive fracture patterns. The requirements in terms of material bonding are therefore clearly met.

Fig. 4: Image of the test specimens for shear bond strength. Left: milled test specimens still in an Ivotion disc, right: sample test specimens following completed testing with a cohesive fracture pattern.

Diagram 3:
Shear bond strength value of Ivotion, measured on the basis of ISO 10477:2018, internal test. Sample values are shown. The green line indicates the minimum requirements (≥ 5 MPa) in accordance with the standard.

Ivotion is the key to amazing efficiency

Ivotion combines both tooth and denture base material in one disc. Digital dentures made of Ivotion are milled from one disc in a single  uninterrupted milling process without time-consuming manual working steps.

Summary

Ivotion from Ivoclar is an intelligent combination of high-grade proven tooth and denture base materials. The monolithic disc contains the unique Shell Geometry, a three-dimensional tooth and dental arch geometry based on real denture data that defines the transition between the tooth and denture base materials. With the Full Denture Module in the 3Shape Dental System, dentures can be customized to suit the needs of the individual patient. If Ivotion is used, there is no longer any need to bond the denture teeth to the denture base, reducing potential problem areas. The PMMA material also impresses with its optimized fracture resistance.

True to the motto: “Design. Mill. Finish.”, complete dentures are fabricated as part of a fast, uninterrupted milling process in a PrograMill milling machine. After the milling process, only polishing is required to finish them. Ivotion is the key to impressive efficiency: it allows patient-specific, monolithic complete dentures to be produced in a seamless workflow with just a few manual steps.