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CEREC Biojaw - typical tooth restorations for the whole jaw

Prof. Dr. Albert Mehl

Prof. Dr. Albert Mehl

Παρ. 11 Ιανουαρίου 2019


CEREC, the treatment method for indirect restorations in just one visit, relies on software with innovative algorithms. Biojaw is one of them. It ensures precisely fitting initial proposals. Prof. Dr. Albert Mehl of the University of Zurich, who was closely involved in the development of Biojaw, explains how it works.

CEREC is a CAD/CAM method for the computer-aided production of restorations based on optical impressions. The CEREC software used for this contains different algorithms for calculating the restoration proposals. How exactly Biojaw – the most important innovation of this software – works is explained here in detail.


Fig. 1: Prof. Dr. Albert Mehl, University of Zurich, is closely involved in the continued development of CEREC and trains CEREC customers all over the world.

The idea

A reference is required to make a proposal for a restoration. These are generally models for which precise impressions of several intact dentitions have been made. Algorithms can derive rules from these impressions for the interaction between tooth sizes, tooth positions relative to each other and to the antagonist, and typical tooth shapes. Biojaw adds an essential component that makes this tool a computer-controlled learning method or a knowledge-based model. The model uses only naturally occurring features. The patient‘s natural teeth are used as the reference.







Fig. 1a-c: Average Biojaw with static (blue) and dynamic (yellow) contacts; this model was calculated from approx. 250 natural dentitions. In addition, individual deviations from this average model can be registered and rules for the reconstruction derived.

Fig. 2a: Automatic reconstruction of different restoration types in a multi-stage process, here: initial situation

Fig. 2b: The Biojaw model is adapted to the remaining tooth substance to allow harmonious positioning, determination of size relationships, and continuation of occlusal surfaces and incisal edges in the restorations.

Fig. 2c: The proposal is refined by analyzing the morphology, determining contact points, and adhering to minimum layer thicknesses (biogenerics)

The technology

For the calculation, the virtual 3D model, the preparations or the associated tooth numbers are needed. The program then analyzes the remaining dentition, particularly the adjacent and antagonist teeth. Based on this information, the „Biojaw“ is then superimposed on this remaining dentition as precisely as possible. In combination with biogenerics, which is a collection of single-tooth models, harmonious and well positioned proposals can be made, even for large-span restorations.

Once the position of teeth has been determined with Biojaw, the individual shapes can be adjusted precisely with biogenerics. At the same time, exact points of contact with the adjacent (approximal) and antagonist (occlusal) teeth are precisely adjusted again, abrasions are detected, transitions to the preparation borders are re-adjusted, and minimum layer thicknesses are maintained, to enable preparation of an expedient, lifelike tooth restoration.


In addition to biogenerics, the Biojaw represents another fundamentally new concept in restoration design. It involved comprehensive restructuring of the software and process sequencing, but at the same time it is the basis for further improvements and functions in the future. The Biojaw also serves as the basis for the Biojaw positioning tool, which opens up new options for positioning teeth and changing the shapes of groups of teeth. With Biojaw and biogenerics, all conceivable restoration proposals can be processed and calculated. They represent the beating heart of the CEREC, CEREC Premium, and inLab design software.

Biojaw is available for CEREC software version 4.4 and higher. No changes have to be made to the milling machines.

How it works

Biojaw is used after the intraoral scan. The scan must include the directly adjacent teeth and especially the antagonist. This lends support to the individual fit and alignment by Biojaw. The adjacent teeth are examined for morphological properties, and these properties are then used in the reconstruction. The anatomy of the entire clinically visible tooth surface is considered, i.e., not only the occlusal surfaces of the posterior teeth or, for example, the incisal third of the front teeth.

Biojaw enables even completely edentulous situations to be reconstructed. If there is no remaining dentition at all, the alignment is calculated using the alveolar ridge and the occlusal plane, for example. The following however applies. The less remaining dentition there is, the more the proposal tends towards the „average jaw.“ Very good results can be obtained even with free-end situations. For these, the scan of the antagonist is very important. The information from the Biojaw is also very helpful for inlays, veneers and onlays. The adjacent teeth can be analyzed more effectively and cusp tips, marginal ridges, approximal surfaces and incisal edges can be detected. If the Biojaw lies exactly flush against these tooth surfaces, the area to be reconstructed is simultaneously automatically aligned correctly in terms of the height of the marginal ridge, the course of the incisal edge or the approximal contacts in a knowledge-based procedure.

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