I'm ready for my implant restoration. This is for an implant bridge for the lower anterior incisors (#23, #24, #25, #26). My implants are in #23 and #26, abutments in place ready to go. The implants were installed by a periodontist, and I now am at a dentist who will make the teeth. When he examined me, he said I would need a 3 or 4 unit bridge. I said I had 4 natural teeth there originally, so how could I possibly need just a 3 unit bridge. (He only used his eyes to exam me, no measuring instruments). He told me it was a spacing issue, and the actual number of units will be decided by the dental lab. The lab will start with solid block of zirconia, and craft the bridge using a CAD/CAM system. Further information is that he will trying to do a screw-retained bridge, avoiding cement if possible. Is it true that sometimes they can only fit a 3 unit bridge where 4 natural teeth used to be? If so, how common is this? I am scheduled for my dental impression a week from now.