BillB,
After a blood supply is established around the implant, there should be no problem. This only takes a few weeks. Of greater importance is to keep pressure off the implant or off the tissue that is over the implant to eliminate micromovement during healing. It is common now to place the implant and a healing abutment--a threaded screw cover that extend through the gum just slightly. This helps eliminate a second surgery just to expose the top of the implant for restoration. Some implants, however, may be completely covered by gum tissue. It depends on a lot of things.
The center of the implant is indeed hollow. This space doesn't communicate with any anatomic structures. This space is surrounded by titanium or titanium alloy.
The internal space is threaded to receive the implant abutment--this connects the implant to the tooth. The abutment can be directly attached to the tooth or act as an intermediary part onto which the tooth will be screw retained. Basically, you can get screwed 3 times--a screw within a screw, within a screw.
Newer implants have cut down on the number of parts that are stacked onto the implant. It is not uncommon to have the abutment screwed into the implant and the tooth CEMENTED onto the abutment--very much like traditional crowns are cemented onto the prepared teeth. Screw retained restorations can be removed if necessary. Cemented restorations might NOT be removable--even with temporary cement--but might fit better in the end.
Screw retention requires greater accuracy in technique. All machined and threaded surfaces must fit--exactly. This is very hard to achieve consistently. Cemented restorations have a slight gap that is filled in with cement. This gap allows for a good fit without all machined parts lining up exactly. The fit accuracy of machined parts is better than the accuracy of the impression materials available to transfer their position to the models used for fabrication.
We have a particular problem with something called "thread time". This is the difference between 1) the ability to screw in a threaded hole to go EXACTLY the same place each time and 2) the inability to accurately pick up the exact position of a threaded hole with the corresponding screw. Imagine a threaded hole with the beginning of the threading at the 12 o'clock position. Any two "identical" screws will seat within that hole at slighly different positions when compared with the lab duplicates and the implant in the mouth. On the lab model, the beginning of the thread may be at the 3 o'clock position. This is a 1/4 turn difference and only fractions of thousanths of a mm but it cause misfits. Once an abutment is attached, it is best to never move it again and then build the restoration to that position. If you remove the abutment, you have no guarantee that it will position exactly to the same point again. The more abutments you have connected together, the greater the error. Impression materials typically have errors measured in microns--10-50 microns. This "slosh" makes up for errors in thread time and can actually aid in the quality of the fit.
All threaded parts should be torqued with micro torque drivers to insure proper compression. It is impossible to "guestimate" by hand. The strongest grip cannot achieve torque reading on a hand driven mini screwdrive anywhere close to recommendations. Each company and implant system part has it's own torque recommendations.
There are even abutments made of zirconia ceramic now with allow for great esthetics, especially in the front of the mouth. The ceramic is amazingly strong. It is similar to the ceramic that is used in the insulating part of a spark plug and is related to the ceramic used in the new ceramic knife blades. The zirconia is machined to very close tolerances. Once attached to the implant, the ceramic can be prepared like a tooth by the dentist or the lab.
The introduction of successful implant techniques, has caused a change in thinking during treatment planning. It used to be that a dentist would try to salvage a tooth--even if it were compromised. Now, a successfully integrated (healed) implant has a BETTER long term prognosis than a shaky tooth. Extraction and replacement with an implant will last longer than salvage/restoration of a tooth with a questionable prognosis. The initial cost for the implant is more but when you factor in the replacement cost of the shaky tooth which is sure to fail, the costs are almost equal.
Good luck with your future tooth. Don't worry about the space within the implant, it's not a problem. Besides, nobody has ever done any diving/implant research--so I can make up just about any answer I like!
Regards,
Larry Stein
