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ePaper created 2016-01-07, 12:59:38 | version 1.38.0
case report I I 31implants4_2015 The restoration consisted of two distinct parts: – the milled bar screwed on to the multi-unit abut- ments; and – the removable telescopic part: the prosthesis, fric- tion-retained on the bar (Figs. 12a & b).7,8 As the seven implants were well distributed over the entire arch, no palatal coverage was needed, meaning enhanced comfort for the patient. Reten- tion of the prosthesis by the bar was enhanced by four CEKA attachments (ALPHADENT; Fig. 13). A milled bar-retained removable prosthesis can be considered an attractive option for patients pre- senting with an atrophic upper jaw and/or bruxism becauseitefficientlycompensatesforthetissueloss, ensuring a good aesthetic outcome, in addition to excellent stability and retention of the prosthesis.9 For this reason, this option is classified by some as falling in the category of removable bridges.9–12 The prosthesis is nevertheless resilient enough to with- stand high mechanical stress, reducing the risk of fracture, especially that of the veneering layer.13,14 _Discussion With conventional casting techniques, producing asubstructureforanimplant-retainedprosthesisre- mains technically difficult.15,16 The difficulty of achieving passive fit is proportional to the number of elementsandvolumeofthesubstructure.Despitethe advances in casting technology, in the case of large- span substructures, primary or secondary brazing is often needed to compensate for the dimension vari- ationsinordertoachieveanabsolutelypassivefit.17,18 Suchanaccurate,passivefitofthesubstructureises- sentialforthebonephysiologyofimplantsandlong- term reliability of implant-retained rehabilita- tions.19,20 Owing to its high precision, CAD/CAM is an invaluable tool for evolving the prosthetic workflow technologically.1,21 The restoration is designed based on a 3-D CAD image created from the scanned data.22–24 CAD software allows modelling of the prosthesis, taking into account the material selected (such as zir- conia;titanium;cobalt–chromium;IPSe.max,Ivoclar Vivadent; and PMMA). As the subtractive fabrication technique (milling) associated with this CAD ensures that the material structure will not be altered, a metal substructure featuring optimal density and homogeneity is ob- tained. In addition, the computerized configuration of this process ensures reproducible results and irre- proachable passive insertion of these substructures. _Conclusion Today’s laboratory scanners can digitize the model, wax-up and implant index. CAD/CAM tech- nology offers unmatched work quality, precision and reproducibility compared with conventional proce- dures. It is certainly the most appropriate technology forproducingimplant-retainedsuperstructures.This technology also allows improved passive fit of sub- structures and facilitates the work of the laboratory technician. Passivefitasaprerequisiteforsuccessfulimplant- retained prostheses ensures long-term reliability of rehabilitation work.25 Moreover, the fabrication cen- tres can machine biocompatible materials such as titanium and zirconia. These CAD/CAM techniques, which are already well established in dental laboratories, constitute a major contribution to our daily practice, and will soon be essential in all practices._ Theauthordeclaresnoconflictofinterest. Editorial note: A complete list of references is available fromthepublisher. about the author Dr Richard Marcelat has a DDS in Oral Implantology from the University of Liège and in Basal Implantology from the University of Nice SophiaAntipolis,as well as a Postgraduate Certificate in Implantology from CURAIO in Lyon in France. He can be contacted at richard.marcelat@orange.fr Figs. 12a & b_The telescopic denture on a milled bar. Fig. 13_CEKA attachments as additional retention devices. Fig. 12a Fig. 12b Fig. 13