When implants have been placed and are restored with the final prostheses, certain principles have to be followed to achieve a good fit and long-term success of the prosthesis. The general principles for delivering an implant-supported prosthesis are very similar to those for delivering a tooth-supported prosthesis. However, the complexity is higher when using implant-supported prostheses since they can have multiple components that fit together very precisely along limited paths of insertion. In addition, these prostheses need to be delivered onto rigidly fixed implants. All these factors make this a much more exacting procedure. It is therefore important to have a protocol to ensure the correct steps are followed so as to minimize the risk of complications and to be able to verify that the procedure has been carried out correctly. It is also important to be able to provide base line information about the prosthesis against which you can compare the condition of prosthesis over time.

After completing this ITI Academy Module, you should be able to: list the step-by-step protocol for delivering an implant-supported prosthesis, describe how to evaluate a prosthesis and rehearse its assembly, describe the steps of trying-in and verifying that a prosthesis is clinically acceptable, describe the clinical techniques for fitting both screw- and cement-retained prostheses, indicate appropriate oral hygiene advice and techniques for implant prostheses and also list the baseline documentation that needs to be recorded for continuing care.

When delivering an implant-supported prosthesis, the following step-by-step protocol should be followed: First evaluate the planned prosthesis prior to the delivery appointment. A rehearsal of the prosthesis assembly should follow. Try-in and verify if the prosthesis is clinically acceptable. If required, make any necessary modifications to render the prosthesis clinically acceptable. Fit the prosthesis. Provide oral hygiene instructions to your patient to ensure proper maintenance. Take baseline records to facilitate continuing care. In the following slides we will go through each step of this process in detail.

The first step in the evaluation and rehearsal should be an inspection of the working cast or model itself. The quality of the working cast or model is important for the accuracy of the final fit of the prosthesis. The points to check include firm retention of the analog in the cast or model; that a solid cast or model has been used when multiple, splinted implants are involved to ensure their interposition precision; and correct representation of the surrounding peri-implant soft tissues that still allows clear access to the analog. If a removable silicone gingival mask has been used to facilitate this access, it should be intact and represent the intended emergence profile. If the working cast or model has been mounted, the articulation against the opposing study cast should be checked and verified as correct.

Next, it is important to evaluate the prosthesis itself prior to the delivery appointment to ensure that is of an appropriate standard and that it fulfills your prescription. If the prosthesis is not correct on the models, it is certainly not going to be correct in the patient's mouth. This assessment is best done well in advance of the fit appointment so that if anything needs to be modified there is enough time to do so. In evaluating the prosthesis, various aspects should be considered: The first is: Does the prosthesis fit on the model? If the prosthesis does not seat on its abutment, you may need to check the internal fit. Any inaccuracies in the fit must be corrected prior to delivery of the prosthesis as these could lead to long-term prosthetic complications.

The second aspect of the prosthesis to evaluate is the contacts. How tight are the proximal contacts? Proximal contacts are assessed using dental floss. The floss should be able to be passed over the contact point with slight resistance. If proximal contacts are too tight, this could lead to difficulties in seating the prosthesis. On the other hand, if the proximal contacts are too light this will lead to problems with interproximal food impaction. Ideally the proximal contacts should be broad enough to prevent food impaction but there should be enough space below the contact point to allow for papilla and interdental cleaning. If a p roximal contact needs to eased, the location of the contact point should be identified using articulating paper so that it can be eased using a polishing wheel.

Attention should then be directed to the occlusion. Is the occlusion correct? It is essential to assess the occlusion of your prosthesis on the models if extensive chairside adjustments are to be avoided at the delivery appointment. Have the models been articulated correctly? This is most accurately verified by using the model to compare the shimstock holds of the patients' natural teeth with those recorded clinically. Ideally the prosthesis should just allow shimstock to draw when the models are articulated and there should be no unintended interferences in lateral and protrusive movements. It goes without saying that it is important that you are satisfied with the overall form and appearance of the prosthesis, including the shade. Should the prosthesis fail on any of aspect it should be rejected and returned to the dental technician for correction.

For cement-retained prostheses, there is the added requirement to assess the position of the finish line of the prosthesis. There is a causal relationship between excess cement and peri-implant disease and every effort should be made to avoid this. Therefore, the cement margin must be located less than 1 mm submucosally in order to allow for removal of any excess cement. When a cement margin is deeper it becomes very difficult to identify and remove any excess cement that might be present. If the cement margin is too deep submucosally, the prosthesis will need to be remade and redesigned to bring the margin into a more accessible position. In some instances that can be resolved by an intermediate custom abutment to bring the cement margin into a more superficial position. Alternatively a screw-retained prosthesis could be made instead.

In order to facilitate the delivery of the prosthesis, it is recommended that you rehearse assembling on the model before attempting to do so in the patient. This allows you to familiarize yourself with all the components involved and how they fit together. Depending on what implant system you are using, there are up to 8 potential positions in which an abutment can be placed. So it is particularly important that you are aware of how to correctly orientate your abutments. You may find it helpful to have some markings, be it a notch in the abutment or a line drawn in indelible marker, to identify the correct orientation of the abutment. If the abutment positioning is particularly tricky, perhaps due to limited access, it may be helpful to have a positioning jig made which guides the abutment into the correct orientation. It may help to practice the path of insertion of the prosthesis, as implant prostheses tend to have very specific paths of insertion and the prosthesis may fail to seat if the incorrect path is followed. Where multiple prostheses are involved, it is important to be aware of the correct order for seating the prostheses, as you may find that one prosthesis prevents another from seating if they have been placed in the wrong order.

Evaluation and Rehearsal, Key Learning Points: When delivering an implant-supported prosthesis, it is important to follow a logical sequence so that, in the heat of the moment, none of the steps is missed. Every effort should be made to identify and eliminate potential pitfalls that would make it more difficult to deliver and maintain the prosthesis. The prosthesis should be evaluated prior to the delivery appointment, so as to ensure that it is suitable for clinical use and to eliminate potential complications that could arise as a result of any defects. Should any aspect of the prosthesis be incorrect, it should be returned to the dental technician for correction. Prior to delivering the prosthesis you should rehearse assembling it. This familiarizes you with the components involved and how they fit together. It's particularly important to know how to correctly position any abutments used.

Having satisfied yourself that the prosthesis is acceptable on the model and that you are familiar with the components in the prosthesis and how they fit together, you proceed to the delivery appointment. The first stage of delivering a prosthesis is to try-in the prosthesis and assess whether it is clinically acceptable. On removing the healing abutment or provisional prosthesis, the prosthesis should be tried in without delay. This is important in order to avoid the soft tissues collapsing, which, in turn, could cause the prosthesis to fail to seat due to soft tissue impingement. It can often be more challenging to position the prosthesis in the patient than it was on the model, due to limited access and presence of soft tissues. It is therefore important that the prosthesis is tried-in using the sequence that was rehearsed on the model so that you are confident you are assembling it correctly. If a different sequence is followed other factors, such as undercuts, which may be difficult to identify intraorally, may prevent seating of the prosthesis. Any screws should just be finger tightened at this time to facilitate easy removal of the prosthesis if needed.

On trying-in the prosthesis, it should be clinically evident whether it is seating in the same way as it did on the model. If in doubt, and particularly with bone-level type implants, where the components are not visible, a confirmation radiograph should be taken to confirm that the prosthesis is seated. As seen in this example the radiograph shows a prosthesis which splints two implants, it's fully seated on one implant and not on the other.

If you find your prosthesis fails to seat, one possible cause is failure to engage the abutment onto the top of the implant. This is less likely to occur on modern internal connection implants than it was on external connection implants. The abutment will need to be repositioned so that it is fully seated. Another possible cause is that the proximal contacts of the prosthesis are too heavy and need to be checked and eased to allow seating. The proximal contacts are checked using dental floss, and if adjustment is required, the contact point is identified using articulating paper. If the soft tissues have collapsed, they may interfere with seating of the prosthesis. It may be necessary to replace the healing abutment or provisional prosthesis to push the tissues back into place before trying-in the prosthesis again. If you have checked the above factors and found them correct but the prosthesis is still not correctly positioned, you may have an inaccurate model. You will need to retake your impression and remake the prosthesis. When trying-in splinted implant prostheses, ensure that the prosthesis is fully seated on each implant using the Sheffield Test. The Sheffield test is used to confirm passive fitting of frameworks. In addition to complete absence of rocking before screw connection, it must be possible for one screw to be fully tightened in place without any visible discrepancy between any other framework-to-implant connecting part. In the laboratory this is tested at 20x magnification and at chairside with Loupes. Failure to fully seat a prosthesis has been linked to complications, but not to biological complications. If the prosthesis fits passively on the model but not in the patient, this indicates an inaccurate model and a new impression should be taken.

Prior to checking the occlusion on the prosthesis, first verify the shimstock-foil-holds on the rest of the patient's teeth before the prosthesis is inserted. Occlusion should only be assessed once you are satisfied that the prosthesis is fully seated. The prosthesis should conform with the guidelines for occlusal design on implant prostheses.

The static occlusion should be assessed first. Occlusal forces should be directed along the long axis of the implant. Contacts should be avoided on inclined planes that could cause non-axial loading. The firmness of occlusal contacts should be graded to allow for differences in axial movement between teeth and implants. Clinically this is most easily tested using shimstock foil that is eight micrometers thick. On light closure, the shimstock should be held where there are tooth-to-tooth occlusal contacts. When an implant occludes against a tooth, it should be possible to withdraw the shimstock with slight resistance. With an implant prosthesis occluding against another implant prosthesis, the shimstock should be able to be withdrawn easily when there is only light contact. On firm closure the shimstock should be held by all occlusal contacts.

Once satisfactory static occlusion has been achieved, the dynamic occlusion can be assessed. This is best done using different colors of articulating paper for each movement. Every effort should be made to avoid lateral working or non-working contacts on posterior implant prostheses as these will introduce harmful non-axial loading, which could lead to prosthetic complications. In the same way, adjacent teeth should be used for guidance where possible so as to provide proprioceptive feedback and reduce the risk of occlusal overload.

Finally the form and appearance of the prosthesis is assessed. Confirm that the form of the prosthesis meets the required functions by checking the following aspects: Does the prosthesis provide the desired occlusal function for which it was made? Do the proximal contacts and crown contours of the prosthesis protect mucosal margins from food impaction while at the same time allowing access for cleaning measures to prevent excessive plaque accumulation? And, last but not least, does the prosthesis fulfill the esthetic requirements of the patient? If any aspect of the prosthesis is inadequate this must be corrected. Once you are convinced that its clinically acceptable, you can proceed to fitting the prosthesis.

Try-In and Verify, Key Learning Points: The prosthesis should be fully seated to reduce the chance of developing prosthetic complications. It is essential to ensure that the prosthesis is fully seated before attempting to assess the occlusion. This may require radiographic verification when using implant systems where the head of the implant is not accessible. Occlusal forces should be directed along the long axis of the implant with graded contact to allow for differences in axial movement between teeth and implants. Avoid lateral working/non-working contacts on implant prostheses. The proximal contacts and crown contours of the prosthesis should protect mucosal margins from foo d impaction while at the same time allowing access for cleaning measures to prevent excessive plaque accumulation.

The next objective focuses on the clinical technique for fitting a prosthesis. When fitting a screw-retained prosthesis, the first step is to fully tighten the screw in the abutment according to the level determined by the manufacturer. In order to know how tightly you are tightening the screw you need to use a calibrated torque driver. This can be manual or motorized. The tightness to which the abutment screw needs to be tightened can vary according to the manufacturer. This can be between 30 to 40 Newton centimeters. Always check the appropriate tightness for your chosen implant system. If the prosthesis is separate from the abutment then the screw in the prosthesis also needs to be tightened. The screw is always tightened to a lower torque than the abutment screw. This is usually between 15 to 20 Newton centimeters, depending on the brand of implant you are using, so please check the manufacturer's instructions.

Once the prosthesis is fully tightened into position, it is necessary to close the access hole. The material of choice for doing this is polytetrafluoroethylene or PTFE tape. If you were to just fill the hole with restorative material it would flow into the head of the screw. This would mean that it would be very difficult to remove the restorative material without a significant risk of damaging the head of the screw. Should the screw be damaged it could make it very difficult to unscrew. To protect the screw head a strip of PTFE is packed into place over the implant head. The PTFE compacts into a firm plug of inert material, which protects the screw and does not deteriorate over time as do wax or cotton pledgets. It forms a firm base against which restorative material can be packed to fill the rest of the hole. Being white, it can help reduce the darkening effect on the restorative material. A variety of restorative materials can be used to fill the rest of the access hole; most commonly composite or glass ionomer materials are used.

As with the screw-retained prosthesis the abutment screw for the cement-retained prosthesis needs to be fully tightened using a calibrated torque driver; the torque value is determined by the implant manufacturer. The screw head is protected from the luting cement that is used to cement the prosthesis by packing PTFE tape into the screw hole in the abutment.

The crown can now be cemented onto the abutment, however you need to avoid the potential complications caused by excess cement. As the crown fits very closely on the abutment, only a very small amount of cement is needed. When loading the crown, only a thin layer of cement needs to be painted onto the walls of the prosthesis staying clear of the margins. This reduces the risk of excess cement extending beyond the margins of the crown. When choosing a luting agent, take a material that is brittle when set and is non-adhesive. This makes it easier to remove any excess material should there be any. For this reason resin-based cements are best avoided. The cement should be radiopaque to allow any excess to be identified radiographically. Cements with a high film thickness should be avoided as they can impair full seating of the prosthesis, thus introducing occlusal interferences that were not present at try-in. Once the prosthesis is seated, it is important to clean carefully around the prosthesis to find and remove any excess cement.

Clinical Technique for Fitting a Prosthesis, Key Learning Points: When fitting a prosthesis the abutment screw must always be tightened, using a calibrated torque driver. Any other screws, known as prosthesis screws, are tightened to a lower torque. How tight the screws are tightened is determined by the implant manufacturer. Screw heads should be protected using PTFE, so that they can be easily unscrewed should the need arise. With cement-retained prostheses, it is important to avoid excess cement under the tissues. To prevent this, only a very thin layer of cement is painted onto the walls of the prosthesis, avoiding the area close to the margin. Just in case there is any excess cement, a cement should be chosen that is radiopaque so that the excess can be seen on the radiograph. The cement should also be brittle and non-adhesive to facilitate removal of any excess.

With the delivery of their implant-supported prostheses, the patient needs to be made aware that their prosthesis is an artificial replacement of their tooth and as such needs even more care and maintenance than their natural dentition. Every effort needs to be made to minimize plaque accumulation around implants to reduce the risk of developing peri-implant mucositis and peri-implantitis. Patients need to be shown not only how to clean interdentally but also how clean submucosally along the emergence profile as far as the implant itself. Oral hygiene advice needs to be tailored for each prosthesis. A variety of different cleaning aids can be used depending on the shape and form of the prosthesis. Each patient needs to be provided with an individual maintenance program to allow for regular monitoring, oral hygiene reinforcement and professional biofilm removal. This should initially be on a 3-monthly basis.

In order to facilitate the long-term maintenance of the prosthesis, the following postoperative records should be taken as part of the detailed clinical record of the case. Postoperative radiographs record that the prosthesis has been fully seated and that there is no sign of excess cement. They also record the condition of the bone around the implant at the time of delivering the prosthesis. Peri-implant probing depths should be recorded, preferably against a fixed reference point, as the soft tissues may remodel and change around the prosthesis. As peri-implantitis tends to cause circumferential bone loss a single accessible reference probing point may be all that is required per implant. The occlusal scheme at the time of delivering the prosthesis should be recorded, indicating the static and dynamic occlusal relationships. As teeth can move, the occlusal contacts will inevitably change over time. Care must be taken to ensure no interferences develop. Postoperative photographs may also help in the long-term monitoring of the implant prosthesis. Systematic and continuous monitoring of peri-implant tissues during maintenance care is recommended for the early diagnosis of peri-implant disease.

Oral Hygiene and Baseline Documentation, Key Learning Points. Prostheses need more care and maintenance than natural dentition. Patients should receive oral hygiene instructions to clean interdentally and submucosally along the emergence profile as far as the implant itself. An individual maintenance program should be set up. Postoperative records facilitate long-term maintenance and should include radiographs, peri-implant probing depths and occlusal relationships.

Protocol for Fixed Implant Supported Prosthesis Delivery, Module Summary: A logical sequence should be followed to avoid missing any steps when delivering an implant-supported prosthesis. The prosthesis should be evaluated prior to the delivery appointment and again at try-in, to ensure that it is suitable for clinical use. Screws need to be tightened to specific levels defined by the manufacturer using a calibrated torque driver. With cement-retained prostheses, avoid leaving any excess material. Bespoke oral hygiene instructions and an individualized maintenance program must be provided. Detailed baseline records need to be taken to facilitate monitoring of peri-implant tissues during maintenance care.