There are many options in restoring a patient’s dentition (Figure 28-1). Some are more difficult than others, but the final results are usually the same. The author has been involved in implant dentistry for the last 16 years. The largest increase in the use of implants has been over the last few years. The author’s dental lab, Jesse & Frichtel (Pittsburgh, PA), is averaging 5000 implants per year. Implant restoration has become the most successful type of restoration for technicians and dentists. The most significant reasons for this success are the very low remake factor and the dramatic cosmetic change. Over time, certain procedures have proven to be the easiest and most predictable in restoring single and multiple unit implants. In this chapter the procedures for a partially edentulous to a fully edentulous restoration are discussed.

Figure 28-1. Perfect white and pink restorations are in easy reach today.

(Courtesy Dr. J. Bedard.)

Partially Edentulous Reconstruction

Prior to the patient’s appointment, provide the laboratory with the specialist’s surgical instructions via email or facsimile. These instructions note the implant size, location, and manufacturer. This information will be used to forward the correct impression posts. On average, it takes up to 5 days to send the necessary impression posts for the case. Also provide the laboratory with the dentist’s name and phone number, the patient’s name, and the date of the patient’s appointment.

Appointment 1 (Impression)

At the first appointment the master impression is taken either by the closed tray or open tray technique.

Option 1: Closed Tray

1. Make sure all the necessary parts are on hand (such as impression posts and screwdrivers) before seeing the patient.

Tip: Be careful; the healing cap or cover screw can require a different screwdriver from the impression post or abutment.

2. Remove the healing cap from the patient’s mouth and store it within easy reach. If you are dealing with multiple implants, lay the healing caps in order so they will not be mixed up.

Tip: Remove only one healing cap at a time and place the impression post before taking the next healing cap off. This will help prevent the collapse of the soft tissue.

3. Place the corresponding impression posts onto the implant by rotating the antirotation device (a hex, octagon, or three notches) in position until you feel the drop or lock of the impression post. Only hand-tighten the screw (Figure 28-2).

4. Take an x-ray horizontal to the platform of the implant to verify that there is no gap between the two components. If a gap or misfit between the two parts can be seen, seat the impression post one more time.

Figure 28-2. The impression post hand-tightened to the exposed implant head.

(Courtesy Dr. R. Windl.)

Tip: It is possible that debris, plaque, or overgrown bone is on the implant platform. Also, the flare of the impression post could be in contact with the surrounding bone. In this case, debris, plaque, or bone should be removed or recontoured.

5. Take a full-arch impression with a conventional crown and bridge heavy- and medium-body impression material. The full-arch impression is necessary for the laboratory to reproduce all detectable functions of the patient.

Tip: Make sure to apply the medium body around the impression post and then place the loaded impression tray as would be done on a crown and bridge impression.

6. Remove the tray after the impression material has fully set. The impression post will stay on the implant. Check for any air pockets or voids surrounding the impression post area.

7. Unscrew the impression posts and immediately place the corresponding healing cap on the implant to prevent the collapse of the soft tissue (Figure 28-3).

Figure 28-3. The implant analog connected to the impression post and carefully inserted into the impression.

(Courtesy Dr. R. Windl.)

Tip: When dealing with more than one implant, it is important that each impression post is packed separately with the corresponding tooth number.

IMPORTANT: Please send the following items to the laboratory: impression, impression post, x-ray of the impression posts in position, opposing model, bite, and all necessary instructions. Also be sure to include the type, size, and manufacturer of the implant.

Option 2: Open Tray

1. Make sure all necessary parts are on hand (such as impression posts and screwdrivers) before seeing the patient.

Tip: Be careful; the healing cap or cover screw can require a different screwdriver from the impression post or abutment.

2. Remove the healing cap from the patient’s mouth and store it within easy reach. If you are dealing with multiple implants, lay the healing caps in order so they will not be mixed up.

Tip: Remove only one healing cap at a time and place the impression post before taking the next healing cap off. This will help prevent the collapse of the soft tissue.

3. Place the corresponding impression posts onto the implant by rotating the antirotation device (a hex, octagon, or three notches) in position until you feel the drop or lock of the impression post. Only hand-tighten the screw.

Tip: For additional accuracy connect all impression posts with dental floss. Then apply GC pattern resin (GC America Inc., Alsip, IL) or a light-curing composite around the impression posts and floss before taking the impression (Figure 28-4).

4. Take an x-ray horizontal to the platform of the implant to verify that there is no gap between the two components. If a gap or misfit between the two parts can be seen, seat the impression post one more time.

Figure 28-4. A, The open tray impression posts connected with dental floss. B, The posts connected with GC pattern resin.

(Courtesy Dr. R. Windl.)

Tip: It is possible that debris, plaque, or overgrown bone is on the implant platform. Also, the flare of the impression post could be in contact with the surrounding bone. In this case, debris, plaque, or bone should be removed or recontoured.

5. A plastic stock tray is widely used for the open tray procedure. Grind a hole in the tray directly over the impression posts, and verify that the impression posts are accessible through the hole (Figure 28-5).

6. Take a full-arch impression with a conventional crown and bridge heavy- and medium-body impression material. The full-arch impression is necessary for the laboratory to reproduce all detectable functions of the patient. As the material begins to set, wipe off the excess from the hole so you can see the screw heads.

Figure 28-5. A stock tray modified to allow access to the screws.

(Courtesy Dr. R. Windl.)

Tip: Blowing low pressure air onto the soft impression material disperses the impression material away from the screw heads.

7. After the material is fully set, unscrew and remove the retaining screw from the impression post. Next, take the impression out. The impression post will be secured in the impression. The screws should be packed and numbered separately.

8. Reinsert the healing caps.

IMPORTANT: Please send the following items to the laboratory: impression with impression posts embedded, x-ray of the impression posts in position, opposing model, bite, and all necessary instructions. Also, be sure to include the type, size, and manufacturer of the implant.

At the Laboratory

Option 1: Cement-Retained Restorations

Upon receipt of the case, the laboratory technician connects the impression posts to the analog. Most implant laboratories stock these analogs. The soft tissue material is applied around the impression posts and the analog. Then the master cast is poured. This allows the technician to remove the soft tissue from the master cast to verify an accurate seat of the restoration.

Tip: This method is preferred because the soft tissue around the implant can be taken on and off without losing information that would be lost if this area were in stone.

There are multiple options when choosing the right abutment for each implant. Most of the larger implant companies have a broad spectrum of abutments. Different choices include cuff heights, flares, and angulations in various materials such as titanium, gold colored abutments, or ceramic colored abutments.

DESIGN 1: STOCK ABUTMENTS

The author has found over the years that about 90% of all implants used are so-called “stock abutments,” which are modified to achieve the look of a custom abutment. Most often, stock abutments need only a small amount of adjustment to fit the patient’s situation. Using stock abutments ultimately results in a tremendous savings for the dentist. The average U.S. cost difference between a stock abutment and a custom abutment is about $150. In most cases, these savings do not compromise the end result of the restorations. Therefore, if you see a custom abutment instead of a stock abutment in most of your cases, one of three things could be a possibility:

1. Your specialist is not placing the implants in the ideal position.

2. Your laboratory is taking you for a ride.

3. You are a prosthodontist who only gets cases that nobody else wants to touch.

If a stock abutment is used, it is likely to be designed as follows. The facial margin and lingual margin should be set 1.5 mm and 0.5 mm below the gum line, respectively. By connecting the lingual to the facial, the abutment will get a scalloped margin. Also, the technician needs to place a flat side and/or groove on the abutment. Both of these two prep features seat the crown and prevent future loosening of the crown. The shoulder preparation on the abutment gives additional stability and thickness to the porcelain, ultimately creating more color and fewer fractures on the margin.

Tip: Depending on the tooth that has to be restored, an abutment that has a significantly wider flare than the implant itself should be used. This gives enough material to create the preparation design chosen by the dentist.

1. The chosen abutment is placed onto the model with soft tissue mask and the gum line is marked on the abutment (Figure 28-6, A).

2. The abutment is removed and screwed onto an abutment holder. Grinding the abutment on the model could loosen or break out the implant analog.

3. The abutment should be prepped to the desired shape. For single crowns, you should incorporate at least two antirotational devices (for example, a scalloped margin and a flat side) (Figure 28-6, B).

Figure 28-6. A, The gum line outlines on the abutment with a permanent marker. B, Prepped abutment with lingual flat side and facial groove.

DESIGN 2: CUSTOM ABUTMENTS

Custom abutments are used mainly for compromised implant placement, very large restorations (to provide better alignment of the abutments), or to change the angle of the abutment.

In today’s dental lab custom abutments are designed with the help of a computer. Before this computer technology was available, custom abutments had to be waxed and casted. After that, the crown was manufactured on top of the abutment. This process required very skilled technicians with years of experience in implant dentistry. Because the dental laboratory industry faces the loss of one third of all its technicians in the next 4-6 years, finding these skilled technicians is very difficult.

Computer-aided design is a huge part of the future of the dental lab industry. Companies such as Atlantis (Waltham, MA) and Nobel Biocare (Göteborg, Sweden) have become great partners for the laboratories. Both companies use computer technology to fabricate abutments out of materials such as titanium or zirconium with little margin of error.

Atlantis

With the Atlantis system the models are sent to the Atlantis facility. There, technicians scan the model and design the abutment with the help of computer software. The abutments are made parallel to each other and then tapered in at a 2-degree angle (Figure 28-7). This level of precision is very difficult for a lab technician to achieve. Atlantis offers polished, unpolished, or gold-plated surface options. Atlantis also offers abutments that are compatible with a wide variety of implant manufacturers so it is very likely that they have the implant abutment needed. Each abutment is saved as a computer file and can be duplicated or reordered as necessary.

Figure 28-7. Parallel Atlantis abutments with retentive surface.

Nobel Biocare

The Nobel Biocare system requires the technician to create a plastic abutment first, view this on the model, and then scan the plastic abutment using a contact scanner (Figure 28-8, A). The computer file is then sent via the Internet to a Nobel Biocare milling facility, where they mill the custom abutment and send it back to the laboratory (Figure 28-8, B and C). Noble Biocare offers implant abutments for companies such as Astra and Strauman in addition to their own platforms.

Figure 28-8. A, Custom-designed scan pattern. B, Zirconium abutments returned from Nobel Biocare’s milling center. C, Adjusted abutments at try-in stage.

(C, Courtesy Dr. S. Kukunas.)

On these abutments the technician has the option to either wax and cast conventional crowns or use the same scanning software to design a full zirconium or aluminoxide substructure. Because these abutments are usually smaller than a tooth preparation, special attention should be paid to the porcelain support of the framework. There should not be more than 2 mm of unsupported space or there may be porcelain fractures in the future.

Option 2: Screw-Retained Restorations

If retrievability is the driving force behind the restoration, a screw-retained restoration is a great alternative option, especially with the new substructures scanned and milled out of zirconium. Because there is no longer a metal substructure, these restorations give both a perfect fit and great cosmetics. Before scanning technology was available, the technician had to wax up the design over a UCLA abutment, which was then invested and casted. After the cast was cooled, it was divested, sandblasted, and then seated by hand to the master model. Compared to the zirconium substructures, these metal-based restorations have a much higher margin of error (Figure 28-9).

Figure 28-9. Screw-retained crown.

Another major use of screw-retained restorations is in cases with less than 7 mm between the head of the implant and the opposing arch, where a conventional crown cannot be cemented. Normally, a restorative height of 2 mm is required for the crown, leaving only 5 mm for the abutment. These 5 mm do not give enough surface area to cement a crown. Therefore, the only option in these compromised cases is a screw-retained crown.

With a zirconium substructure a technician still designs the frame, but instead of casting it the technician scans the framework and an off-site milling machine mills the substructure. This guarantees a very accurate fit to the master model. Because of the precision and consistency of this computer-based system, the author strongly prefers zirconium over metal substructures for these types of restorations (Figure 28-10).

Figure 28-10. A, Nine engaging plastic UCLA abutments screwed to the model. A full pattern of the desired end restoration is made in clear orthodontic acrylic. B, The full contour substructure cut back to allow room for the porcelain. This pattern is scanned by the computer. C, After receiving the substructure, it is checked on the model and returned for the try-in.

Appointment 2 (Try-in)

The same steps are taken at the framework try-in as in a cement-retained procedure, with the exception that a passive fit is desired. An implant bridge try-in is no different from a crown and bridge try-in. A sealed margin and no rocking of the bridge should be seen. If there is rocking in a metal framework, the frame should be cut and reconnected using GC pattern resin. After the frame is secured, a pickup impression with a full-arch tray should be taken. It is recommended that the frame be tried-in one more time after it is laser welded and returned by the laboratory.

Tip: A zirconium framework is very hard to cut and there is no way to solder, laser, or reconnect the framework; it has to be remade. In the case of a nonfitting zirconium framework, a new implant level impression is recommended.

At the Laboratory

After receiving the case, the framework has to be cleaned thoroughly to ensure that there is no biological matter left behind on the frame. These residues could cause failure in the bond between the frame and the porcelain or cause gas bubbles when the porcelain is fired. Porcelain can now be applied to the frame (Figure 28-11).

Figure 28-11. A, Finished zirconium framework with pink porcelain applied. B, Finished framework from palatinal view.

(A, Courtesy Dr. J. Bedard.)

Appointment 3 (Insert)

Option 1: Cement-Retained Restorations

The abutment and the transfer jig come on the model and the crown is packaged separately.

1. Remove the healing cap from the patient’s mouth and store it within easy reach. When dealing with multiple implants, lay the healing caps in order so they will not be mixed up.

Tip: It is recommended to remove one healing cap at a time and place the impression post before taking the next healing cap off. This helps prevent the collapse of the soft tissue.

2. Insert the abutment onto the implant and verify the seat with an x-ray.

Tip: Before beginning this procedure, unscrew the abutment from the model, leaving the transfer jig on the implant abutment. Place the transfer jig with the abutment(s) into the patient’s mouth. The jig will guide you (Figure 28-12).

3. Place the crown on the abutment.

4. Check for occlusal clearance. Slight contact should be made on the crown only under full bite force.

Figure 28-12. A, Jig in place on the model. B, The jig holding all three abutments together in the right position.

IMPORTANT: Use a torque wrench to tighten the abutment. Torque settings vary depending on the implant manufacturer and screw type.

5. If the dentist and the patient are satisfied, cement the crown with permanent or temporary cement.

Option 2: Screw-Retained Restorations

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