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Veneering options - part 1

by: Stefan Holst

Read the first part of Professor Stefan Holst's article on veneering options for fixed implant-retained restorations. This time, you get an introduction to techniques and materials.

Veneering Options for Fixed Implant-retained Restorations

The combination of advanced materials and manufacturing techniques makes the industrial production of prosthetic components possible for every clinical situation. Where just a decade ago only single copings could be manufactured, today we’re seeing manufacturing versatility that allows not only single abutments but multi-unit frameworks on the implant or abutment level.

The NobelProcera System guarantees unrivalled product quality for almost any patient situation. No other CAD/CAM system has such a celebrated heritage, stemming from decades of experience in producing the highest quality multi-unit frameworks for both natural teeth and implants.

When compared to conventionally fabricated frameworks, CAD/CAM frameworks demonstrate decisively distinctive advantages, including material homogeneity, customized design options, and ease of fabrication. Industrial production also guarantees uniform high quality and consistent cost-efficiency by reducing labor-intensive work in the dental laboratory along with its related costs.

Scientific data confirms that material incompatibilities between cast and machined components can be minimized or eliminated when titanium or zirconia are used. Corrosive phenomena at the interface between dissimilar metal alloys can thus be prevented while facilitating precision fit at the same time. This approach also promotes soft tissue stability and marginal bone maintenance.

Crucial choices

In order to ensure longevity when restoring an edentulous patient with an implant-retained restoration, the selection of proper materials, prepared with appropriate precision, is vital.

What the ideal protocol for finishing/ veneering CAD/CAM frameworks entails has been intensively debated in recent years. Both metal-based and all-ceramic framework materials can withstand intraoral loading; the veneering material is the weak link.

Despite extensive research activities, chipping — or the partial delamination — of ceramic veneering materials is reported as the chief reason.

In addition to the options dental ceramics provide, polymer-based materials should also be taken into consideration as an alternative material when finishing options for frameworks are considered.

Today, polymers are used in dentistry for a wide array of applications, in which their use ranges from impression materials to direct/ indirect restorative materials. They are used as denture base materials and for such standard components in implant dentistry as healing caps, impression transfer units, etc.

By modifying their chemical composition and/or adding filler particles to the microstructure, the physical properties and material characteristics of polymers can be adjusted to specifically meet the requirements of a given clinical application.

Advances in material sciences

Extensive research activities in recent years have led to new and improved materials — and entire groups of materials — that reduce unwanted or non-beneficial properties and provide safe, easy-to-use (and easy to- maintain) solutions.

If combined with high-strength framework materials such as titanium or zirconia, polymer veneering significantly reduces the overall cost of the restoration. Cost control, of course, must always be kept in mind, since patient expectations and financial means differ, clinical situations vary, and virtually every laboratory set-up is unique.

Three General Techniques

For conventional veneering, three general techniques can be used to achieve esthetics and function:

  • The conventional hand layering technique is the most frequently used method, which generally results in a good esthetic outcome and proper morphologic contouring. However, the specific skills and experience of the technician have a significant impact on the overall outcome and quality of a restoration utilizing this technique. A manual process, hand layering can sometimes be uncharitably characterized by its lack of standardization.
  • The “press technique” is an alternative method that reduces operator-induced errors such as cracks, air trapping, etc., and ensures a more homogenous material microstructure. With this technique, a full anatomical contour is waxed, invested, and the ceramic material is pressed onto the framework.
  • Full anatomic milling from a homogenous glass-based ceramic or acrylic block material utilizing CAD/CAM technologies is the third option. This method produces optimal material microstructure due to its use of high-quality block specimen and the complete elimination of manual manipulation.

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