The new NobelProcera system for clinical success: The next level of CAD/CAM dentistry

The impact of advanced materials and manufacturing techniques on dentistry is significant. Owing to their many advantages, CAD/CAM technology and industrial fabrication of prosthetic components will replace several conventional laboratory fabrication processes in the future. Today, almost any clinical situation from conventional tooth-supported to implant-retained superstructures can be manufactured. This broad versatility and a guarantee of the highest quality material and precision of fit ensure reliable and safe solutions for any clinical indication irrespective of the type of finishing (Fig. 1). Moreover, industrialised fabrication methods reduce cost-intensive manual labour and provide cost-efficiency in the dental laboratory and practice. The CAD/CAM system is able to minimise material incompatibilities, corrosive phenomena due to dissimilar metal alloys, interfaces between cast and machined components, and inadequate precision of fit.

This influences both the long-term success of a restoration and the aesthetic outcome. However, the predominant criteria for success are adequate treatment planning and the precise transfer of the intra-oral situation into a digital data set.

Conoscopic holography: The next level in non-contact digitisation in dentistry

Currently the majority of scanners utilised in dentistry apply the triangulation principle. The configuration consists of two sensors (one a digital sensor and the other a camera or light-projector) observing the object. The triangulation sensor projects light onto the object, which is reflected back to a detector that is at an angle to the emitted light. The position of the illuminated pixel creates a triangle (light, object, detector) that allows the calculation of the distance from the sensor to the object. Owing to the working principle, this technique is adequate for scanning conventional dental casts predominantly. Although initial attempts to scan cavities were made, the general set-up has distinct limitations (shadowing effect). A variation of triangulation is structured light (projected fringes) projected onto the object. A camera, offset slightly from the pattern projector, looks at the shape of the light and uses a triangulation technique to calculate the distance of every point on the line.

Figs. 2 & 3a: The working principle of a conoscopic laser scanner. The significant difference to conventionally used non-contact triangulation scanners is the co-linearity of the laser beam. (Fig. 2). Schematic illustration of the conoscopic holography (left) and triangulation working principle (right) (Fig. 3a).

An innovative technology introduced with the new NobelProcera non-contact scanner is conoscopic holography. The most significant difference to triangulation is the co-linearity of the laser beam: the light is emitted and reflected in the same axis, allowing for a whole new range of applications. In conoscopic holography—unlike triangulation—the measurement is not based on the geometry of the sensor and the system. Conoscopic holography creates a special fringe pattern and signals proportional to the distance from the object, and obtains a large amount of quality data reflected back from the surface, increasing measurement capability and precision. The scanner can digitise any convex (positive) or concave (negative) geometry that the laser beam is capable of ‘seeing’ with coverage of up to 240º (180º + 60º undercuts). This set-up combined with the co-linearity also allows for the scanning of impressions, eliminating a potential step for inaccuracies, such as model fabrication (Figs. 2–4a & b).

Figs. 3b & 4: General set-up of triangulation scanners prevents scanning of deep cavities due to shadowing effects (left). Co-linearity of the beam in conoscopic holography (right) allows for scanning of deep cavities (e.g. impressions) (Fig. 3b). The new NobelProcera scanner (Nobel Biocare) based on conoscopic holography provides high accuracy for both impression-scanning and conventional cast-scanning (Fig. 4).

Ease of use and additional safety features with improved design software

In order to ensure efficient workflow, the digitisation and manufacture of components is needed, as well as a user-friendly software interface and intuitive handling.

Current scientific findings and clinical experience underscore the need for adequate material manufacture and framework design to minimise clinical failures, such as the chipping of veneering ceramics or fracture of frameworks. The most important request—especially when working with zirconia substructures—is that the framework is anatomically designed and no manual post-processing adjustments are needed. Previously, double-scans were performed to achieve this goal. However, with new software design tools, these time-consuming and cost-intensive steps are unnecessary, as ‘anatomic tooth-libraries’ support the user in optimal restoration and framework design. Automatic cutback functions increase the ease of use and provide an additional margin of safety by ensuring homogenous veneering material thickness.

An equally important aspect to consider is the design and dimension of the connector cross-section for fixed dental prostheses. Long-term clinical success is ensured only if minimum connector dimensions are respected. Newly developed software tools support the user in virtual design of the frameworks and provide immediate feedback on cross-sectional area, connector height and width, as well as coping thickness (Figs. 5a–d).

Figs. 5b–d: Advanced software systems provide an additional margin of safety for the technician and the patient, as cross-sectional views allow for assessment of the correct framework dimension. As the connector area is the most critical aspect of long-term clinical success, special software features (NobelProcera software, Nobel Biocare) help to design the connector appropriately.

Versatility for patients’ demands and expectations: Material selection

A wide range of materials can be used in CAD/CAM manufacturing. Important aspects to consider include long-term stability in the oral cavity, biocompatibility, and post-processing options (for example, the type of veneering material).

Advancements in ceramic materials research have led to the development of high-strength, non-silica-based ceramics that have beneficial properties, including biocompatibility, aesthetics and long-term function. Aluminium oxide (Al₂O₃) and zirconium oxide (ZrO₂) ceramics are the most common materials for copings, FPD frameworks, and implant abutments. It is often wrongly assumed that CAD/CAM technology is only applicable to zirconium ceramics. Actually, CAD/CAM technology can be applied to a variety of materials. Aluminium oxide ceramics are the material of choice in aesthetically demanding areas, for example the anterior dentition, owing to their beneficial light optical properties.

In addition, the clinical applicability of Al₂O₃ in single-tooth and short-anterior FPD has been clinically proven, and Al₂O₃ surpasses zirconium in terms of long-term clinical success and aesthetic outcome. In contrast, for large-span and posterior restorations, yttria-stabilised zirconium dioxide (Y-TZP) is the material of choice. The material fracture strength properties of Y-TZP allow its application in any area of the oral cavity where strength and stability are more important than aesthetics. Additionally, the material properties of zirconium make it a reliable alternative to cast alloys for implant-retained superstructures, including implant abutments and multi-unit implant-retained bridge frameworks. The availability of shaded zirconia is yet another step towards extensive and highly aesthetic solutions for the patient (Fig. 6).

Fig. 6: In order to maximise aesthetic outcome, shaded zirconia abutments (NobelProcera Abutment Shaded zirconia, Nobel Biocare) can be combined with alumina or zirconia copings.

Alternative materials are titanium and non-precious alloys, such as cobalt-chrome (CoCr). If centrally manufactured, these materials ensure excellent precision and long-term function in the oral cavity (Figs. 7a & b).

Figs. 7a & b: Industrial fabrication provides consistent product quality irrespective of material ordered, owing to material-specific milling and sintering strategies impossible in small units (Nobel Biocare production facility Tokyo, Japan).

Additionally they may be applied whenever space requirements or expected biomechanical forces prohibit the use of ceramic materials or as long-term provisional restorations. With the new NobelProcera software, deciding on the appropriate material needs merely a click of a button.

Clinical versatility through solutions for natural teeth and implants

A basic requirement of a modern CAD/CAM system is providing solutions for natural teeth and implants. In the future, implant-retained restorations for missing teeth will become the predominant form of restoration. The clinical success rates, the high predictability and a reduction of costs, as well as the implementation of implantology in dental school curricula will lead to more frequent and earlier implant placement when a tooth is deemed non-restorable.

The abutment design and material to restore implant-retained single-tooth or implant-retained FPD restorations must fulfil some basic requirements. Today, multiple abutment types are available. Various studies have demonstrated the successful application of ceramic and titanium abutments in terms of acceptable soft-tissue and marginal bone stability.

A study examining different abutment materials and their influence on soft-tissue barriers surrounding dental implants found that the type of material used affected both the height and the quality of the tissue. Titanium and ceramic abutments permitted the formation of a mucosal attachment, while gold-alloy and metal-ceramic abutments led to soft-tissue recession and crestal bone resorption. Similar findings were observed through in vitro studies that validated the finding of reduced plaque and bacterial adhesion on titanium or zirconia abutments.

An indispensable factor of the long-term clinical success of implant-retained superstructures is the precision of fit. Depending on the complexity of a restoration, poor fit can have a significant impact on function and stability in the oral environment. When it comes to reproducible precision, CAD/CAM technology clearly outperforms conventional framework manufacturing techniques. New generation software tools eliminate the need for time-consuming framework design on the master cast. Instead, a scan of the implant position can easily be matched to a scan of a wax-up, followed by a virtual framework design in the CAD tool. Adjusting the design and dimensions according to the anticipated final contour of the definitive restoration is done in a few minutes instead of several hours with conventional fabrication protocols (Fig. 8).

Fig. 8: Screenshot of the design tool for implant-retained frameworks (NobelProcera software, Nobel Biocare). Cost-efficient workflow and high precision make this approach a very promising one for the future.

Eliminating time-consuming and cost-intensive fabrication steps in the laboratory is not only beneficial for economic considerations, but also leads to an overall increase in precision and component quality through industrial manufacturing processes.

Editorial note: This article was originally published in Cosmetic Dentistry Vol. 3, Issue 2, 2009 and is published here with the kind permission of Nobel Biocare. A complete list of references is available from the authors.

Contact info

Hans Geiselhöringer, Dental Technician
Dental X Hans Geiselhöringer GmbH & Co. KG
Lachnerstraße 2
80639 Munich, Germany

Dr Stefan Holst
University Clinic Erlangen
Dental Clinic 2 – Department of Prosthodontics
Glueckstraße 11
91054 Erlangen, Germany