Our questionnaire indicated a distribution of 61.4% cement-retained versus 38.6% screw-retained prostheses (Q3), suggesting that cement retention is used more frequently in Japan. Unfortunately, the fabrication-oriented focus of this survey prevented clarification of the types of cement used for cement retention and the breakdown between provisional and definitive cement.

Next, concerning the types of abutments used with cement-retained prostheses (Q4) (Figure 1), CAD/CAM abutments accounted for about one third of the total (titanium, 19.7%; zirconia, 12.1%), and custom UCLA-type abutments made from cast gold alloy accounted for about the same proportion. It is likely that this breakdown is because, in many cases, implant systems using fabricated crowns are not supported by CAD/CAM abutments. CAD/CAM system use is also subject to numerous limitations because of the licensing process imposed by the Ministry of Health, Labour and Welfare (MHLW) in Japan, which is strict when compared with its constituents in other countries. The questionnaire also indicated that titanium two-piece abutments (preparable type) are used in about the same proportion; 28% of the time. This reflects such factors as efforts to keep laboratory costs down and to shorten delivery time frames, in addition to the above reasons.

Concerning the types of prostheses used in the anterior region (i.e., veneering materials), the questionnaire indicated a trend toward selection of roughly the same materials for both single crowns and bridges (Q5) (Figure 2). As a rule, porcelain fused to metal (PFM) crowns accounted for 43.7% of the total, but selection of metal-free restorations using zirconia has been increasing in recent years, reaching approximately 27.1%. Incidentally, veneering porcelain was also used as the veneer material for zirconia copings.