The CICERO system for CAD/CAM fabrication of full-ceramic crowns

doi:10.1067/mpr.2001.114399

The Journal of Prosthetic Dentistry

Volume 85, Issue 3, March 2001, Pages 261-267

https://doi.org/10.1067/mpr.2001.114399 Get rights and content

Abstract

The CICERO method of crown fabrication consists of optically digitizing a gypsum die, designing the crown layer buildup, and subsequently pressing, sintering, and milling consecutive layers of a shaded high-strength alumina-based core material, a layer of dentin porcelain, and a final layer of incisal porcelain. Final finishing is performed in the dental laboratory. The CICERO method allows efficient production of all-ceramic restorations without compromising esthetics or function. This article reviews the process involved in the fabrication of a CICERO crown. (J Prosthet Dent 2001;85:261-7.)

Section snippets

Basic elements of the CICERO method

CICERO is a registered trademark of Cicero Dental Systems B.V. (Hoorn, The Netherlands). The CICERO method for the production of ceramic restorations uses optical scanning, ceramic sintering, and computer-assisted milling techniques to fabricate restorations with maximal static and dynamic occlusal contact relations. With the CICERO CAD/CAM method, crowns and inlays with different ceramic layers—such as high-alumina core, dentinal, and incisal porcelain for maximal strength and enhanced

Scan-model preparation

In this example, a CICERO crown on the maxillary right second premolar is constructed. An impression is made of the arch with the prepared teeth and poured in gypsum. The operator must proceed with great precision because the impression and the model are the basis for all future processing. The gypsum cast of the model that contains the preparation is marked with black/white contrast for unambiguous scanning of the margin (Fig. 2).

. Preparation marked with black/white contrast of unambiguous

Summary

This article has detailed the CICERO method for the production of an all-ceramic crown. CICERO deviates from the CAD/CAM techniques developed recently in that it makes use of a layered crown for better strength and enhanced esthetics.

Functional computer-modeled ceramic restorations can be produced with proper occlusal relations without excessive work in the patient's mouth. The development of CICERO may be one of the major factors in a wider implementation of computer-modeled fixed

Supplementary Files

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A comprehensive search of studies published up to September 2019 was performed in PubMed/MEDLINE, Web of Science, Cochrane Library, and SciELO databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA Statement) criteria and was registered and approved in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42020152197). The population, intervention, comparison, outcome (PICO) question was “Do the CAD-CAM frameworks have similar performances to those fabricated by conventional techniques?” The meta-analysis included clinical and in vitro studies based on the effect size and test of Null (2-Tail) with 95% confidence interval (CI). Clinical and in vitro studies were selected and analyzed separately.
A total of 15 articles out of 358 were selected. For clinical studies, quantitative analysis with a sample of 25 participants showed a mean discrepancy between occlusal rests and rest seats of 184.91 μm (95% CI: 152.6 μm-217.15 μm) and heterogeneity (I²) of 0%. Clinical data considered that frameworks were acceptable for continuity of treatment. The predominant materials were cobalt-chromium (Co-Cr) and polyetheretherketone (PEEK), and studies using Co-Cr reported that the structure required adjustments. In addition, it has been reported that the indirect technique was time-consuming and selective laser melting (SLM) can be costly. PEEK structures have been more widely accepted because of improved esthetics. Quantitative data from the in vitro studies revealed that the additive manufacturing technique (2.006 mm: 95% CI: -2.021 mm to 6.032 mm) was not significantly different from the indirect technique (0.026 mm; P=.455; random: I²: 98.402%).
Clinical studies and in vitro research on CAD-CAM planning and manufacturing of removable prosthesis frameworks are still sparse. However, preliminary data indicate a similar fit and esthetic improvement when compared with the conventional technique.
Morphology and fracture behavior of lithium disilicate dental crowns designed by human and knowledge-based AI
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Citation Excerpt :
Knowledge-based AI is a problem-solving method based on a preset knowledge base (Haenlein and Kaplan, 2019; Steels and Lopez de Mantaras, 2018) that has been deployed in dental prosthesis design, namely “generic tooth” shape design in Cicero system (Elephant Industries, Netherlands) that can design fixed partial dentures and crown (van der Zel, 1993; Olthoff et al., 2000) and “biogeneric individual model” in CEREC CAD software (Sirona Dental Systems, Bensheim, Germany) that can automatically generate designs of single crowns, partial crowns, inlays, onlays and veneers (Bohner et al., 2016; Revilla-Leon et al., 2021). Based on the mathematical representation of tooth morphology, the algorithm captures features within the teeth library, computes average tooth size/shape/occlusal features quantitatively, then reconstructs the occlusal surface via different mechanism: For Cicero, static contact is used to search for the antagonist contact and then axiographic motions are inputted to simulate the dynamic jaw motion (Olthoff et al., 2000; van der Zel et al., 2001). For CEREC biogeneric individual (BI) mode, the morphology and occlusal relationship among the abutment tooth, the adjacent and antagonist teeth are inputted and analyzed, then the missing tooth structure is automatically generated based on principal component analysis (Revilla-Leon et al., 2021; Mehl and Blanz, 2005; Mehl et al., 2005a, 2005b; Richter and Mehl, 2006; Shan et al., 2021; Arslan et al., 2015).
This study aimed to compare the occlusal morphology and fracture behavior of lithium disilicate ceramic dental crowns on 12 human participants' premolar #45 designed by a knowledge-based AI (CEREC, biogeneric individual function, BI) and different human personnel (experienced technician, TD, and trained dental students, AD) using CAD software. Digital datasets of crown design were best-fit aligned with the original teeth to evaluate profile and volume discrepancies of the occlusal morphology, and difference in the functional cuspal angle. Milled and sintered lithium disilicate crowns were resin-luted to 3D-printed dental casts and were subjected to axial load-to-fracture test. The fracture loads and failure modes were recorded and examined. Repeated measures ANOVA with LSD post-hoc test, Kruskal-Wallis test, Pearson's correlation coefficient, paired t-test, and chi-square exact test were used for statistical analyses (α = 0.05). BI-generated crowns showed the highest occlusal profile discrepancy (0.3677 ± 0.0388 mm), whereas human-CAD designed crowns showed higher conformity to the original teeth (0.3254 ± 0.0515 mm for TD, 0.3571 ± 0.0820 for AD; z-difference method; p < 0.001). Cusp angle values were significantly different in all groups except BI and TD (54.76 ± 3.81° for the original teeth, 70.84 ± 4.31° for BI, 67.45 ± 5.30° for TD, and 62.30 ± 7.92° for AD; p < 0.001). Although all three groups of crown designs could achieve clinically acceptable fracture resistance (1556.09 ± 525.68 N for BI, 1486.00 ± 520.08 N for TD, 1425.77 ± 433.34 for AD; p = 0.505) such that no significant difference in fracture strength was found, most crowns presented catastrophic bulk fracture that was not clinically restorable because of the substrate fracture. Group BI had a significantly higher percentage of restorable substrate damage than TD (p = 0.014) and AD (p < 0.001). In conclusion, in designing lithium disilicate dental crown, CAD design with human may be better than knowledge-based AI.
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Preparation and characterization of new dental porcelains, using K-feldspar and quartz raw materials. Effect of B<inf>2</inf>O<inf>3</inf> additions on sintering and mechanical properties
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Common uses include teeth full coverage as crowns, inlays and onlay porcelain bridges, veneering agents, castable ceramics and porcelain fused to metal [39–46]. It is particularly suitable as a restorative dental material because of its glass-like properties, its resemblance to tooth enamel, durability, etc [43–47]. These compounds include feldspar, silica and kaolin (also refined as clay).
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^☆: Supported by a grant from the Foundation of Technical Sciences, Utrecht, under grant number STW.ATH 55.3637.

^☆☆: ^aTechnical Director, CICERO Dental Systems B.V.

^★: ^bLaboratory assistant and computer programmer, CICERO Dental Systems B.V.

^★★: ^cLaboratory assistant and computer programmer, CICERO Dental Systems B.V.

^♢: ^dProfessor and Department Chair, Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA), University Amsterdam.

^♢♢: Reprint requests to: Dr J. M. van der Zel, Verlengde Lageweg 10 1628 PM Hoorn, THE NETHERLANDS Fax: 31(229)259-021 E-mail: [email protected]

^♦: J Prosthet Dent 2001;85:261-7

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The CICERO system for CAD/CAM fabrication of full-ceramic crowns☆,☆☆,★,★★,♢,♢♢,♦

Abstract

Section snippets

Basic elements of the CICERO method

Scan-model preparation

Summary

Supplementary Files

J Am Dent Assoc

Measurement of margins of partial-coverage tooth preparations for CAD/CAM

Int J Prosthodont