Computer modeling of occlusal surfaces of posterior teeth with the CICERO CAD/CAM system,☆☆

https://doi.org/10.1067/mpr.2000.107785Get rights and content

Abstract

Statement of Problem: Static and dynamic occlusal interference frequently needs to be corrected by selective grinding of the occlusal surface of conventional cast and ceramic-fused-to-metal restorations. CAD/CAM techniques allow control of the dimensional contours of these restorations. However, parameters responsible for the occlusal form need to be determined. In most articulators, these parameters are set as default values. Which technique is best for minimizing the introduction of occlusal interference in restorations has not been determined. Purpose: This study investigated differences in crown structure of a crown designed in static occlusion (STA) with designs adapted for dynamic occlusal interferences. Therefore, values from an optoelectronic registration system (String-Condylocomp, KAVO), an occlusal generated path (OGP) technique and default settings (DEF) were used in the CICERO CAD/CAM system. Material and Methods: Morphology of CON, DEF, and OGP crowns was compared with that of the STA crown with respect to differences in a buccolingual section and frequency of occlusal distances in an interocclusal range of 1 mm, measured from the occlusal surface of the crown. Results: All crown types fulfilled the esthetic and morphologic criteria for restorations in clinical dentistry. Difference in the morphology of the OGP crown, compared with that of the STA crown, was greater than that for the CON and DEF crowns. These differences were seen especially in the distobuccal part of the occlusal surface; however, the number of occlusal contacts was considered sufficient to stabilize occlusion. Conclusion: Functional occlusion, adapted to dynamic occlusion in a CICERO crown for the first mandibular molar, can be obtained using data acquired with the String-Condylocomp registration system. The OGP technique was preferred to other techniques because of the simplicity of the technique for eliminating potential problems with opposing teeth during motion. However, this is achieved at the cost of fewer points of contact during occlusion than with the CON crown. (J Prosthet Dent 2000;84:154-62.)

Section snippets

Material and methods

Fourteen acrylic resin dental elements were placed in the upper and lower jaws of a model of a human head (Patient Simulator, Kavo EWL). The relation between the maxilla and mandibular could be classified as Angle Class I with a sagittal overjet of 1 mm. The dental arches were fixed in the head and connected via a mechanical temporomandibular joint (TMJ). The inclination of the condylar path of the TMJ has been preset by the manufacturer. The contact movements of both jaws are guided manually

Results

Trajectories in mediotrusive, laterotrusive, and protrusive direction as obtained from the border movements in the KAVO simulator are shown on a projection of the STA design of the first mandibular molar in the occlusal, the buccolingual, and the mesiodistal view, respectively (Fig. 4, A through C ).

. Result of translations and rotations calculated for position of T46, illustrated as pathways from maximal occlusion in mediotrusive (red), laterotrusive (blue), and protrusive (yellow) direction in

Discussion

Although the strength and the esthetic demands of dental restorations can be met by automated production system,7, 8, 9 and such systems are less time-consuming and thus will help to reduce the expenses of dental treatment, the functional properties of the restoration will determine its overall quality. For this reason, the production of crowns that do not cause interference in dynamic occlusion and in which there is optimal contact in centric occlusion will be of great value to dental practice.

Summary

This study demonstrated that, in the near future, computer techniques may help to monitor the ideal articulation in restorative dentistry. Electronic registration devices are an essential part of these new techniques. The CICERO CAD/CAM system is well equipped to demonstrate the influence of various articulator settings on the 3-dimensional configuration of occlusal surfaces. A study to demonstrate systematically the influence of these parameters is in progress.

Supplementary Files

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    This study was supported by a grant from the Foundation of Technological Sciences Utrecht under grant number STW.ATH.553637.

    ☆☆

    Reprint requests to: Dr L. W. Olthoff, Department of Oral-Maxillofacial Surgery, Prosthodontics, and Special Dental Care, PO Box 80.037, 3508 Ta Utrecht, THE NETHERLANDS, Fax: (31)30-2535537, E-mail: [email protected]

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