Creating the Ideal Prosthodontic Platform: Implants or Endodontics in the Aesthetic Zone?

With the success of implant therapy both aesthetically and functionally, today’s clinician has to consider numerous diagnostic variables, as well as corresponding treatment procedures, when tooth retention is selected or when implant therapy is chosen. Certain treatment options, such as replacing a root with an immediate implant after extraction or retaining a tooth with endodontic therapy, depend upon proper evaluation of functional as well as aesthetic considerations. Identifying the anatomic limitations of the tooth socket in immediate implant placement is an important consideration to achieve the ideal gingival architecture through prosthodontic techniques.
Several orthodontic, periodontic, and prosthodontic treatments can be utilized to improve both endodontically treated teeth and dental implants. Many of these treatment options are addressed in detail in this article’s accompanying full video program, an excerpt of which is available at dentistrytoday.com. One of the best documents available to help guide a diagnosis is The Parameters of Care by the American College of Prosthodontics. It offers a flow sheet of the different questions that must be discussed with patients and colleagues, as well as answered, to achieve an accurate diagnosis and to ensure that all relevant issues have been shared with the patient. This article will highlight a selection of cases for diagnosis and treatment options, and conclude with patient care for extraction and immediate implant placement for tooth No. 7 in an adult female patient.

IMPLANTS AND IATROGENESIS

It is no longer necessary to harvest healthy, noninvolved host tissues to support therapeutic intervention. Therapeutic, reconstructive therapies can be limited to just the presenting pathology or condition. While enamel or dentin cannot be regenerated, bone and soft tissue can be transplanted to develop an excellent receptor site for implants. In the past, prosthodontics required the use of healthy, adjacent tissues in order to support and retain crowns, fixed partial dentures, and removable partial dentures. Implant therapy is the least invasive form of tooth replacement with the fewest biologic maintenance issues.
Implant prosthodontics has several biologic advantages. These include preserving the alveolar ridge in edentulous patients (minimizing atrophy and resorption), maintaining muscular strength and attachment in edentulous patients, not jeopardizing the periodontal tissues around potential tooth abutments, eliminating endodontic risk, and eliminating recurrent caries risk, a significant cause of tooth loss with age.

ENDODONTIC SURVIVAL

A diagnostic and treatment dilemma is the selection of either endodontic therapy with prosthodontic treatment or implant-supported prosthodontic therapy. Some articles and lecturers advocate the routine use of implant therapy rather than prescribing endodontic therapy. This philosophy is clearly wrong. The question is which therapy will create the most effective and durable prosthodontic platform on which to replace missing teeth, not whether a root canal can be performed.
It seems more conservative to leave a tooth, but many times it is not. The demands of prosthodontics and tissue preservation would indicate that it might be necessary to extract a tooth earlier to provide a more stable long-term result with the technology of dental implants. The reason to perform a root canal is to save the tooth for function. With a root-treated tooth, though, potential problems exist for prosthodontically induced endodontic failure as well as the usual endodontic limitations, so an implant can offer a better prosthodontic platform.
A common issue with endodontically treated teeth is that when a failure does occur the residual pathology can create potential problems for subsequent implant placement. Bone resorption and damage from infections of an endodontic origin can be extensive and require significant bone grafting and soft-tissue reconstruction. An additional reason that an implant or graft might fail in an extraction site of an endodontically compromised tooth is inadequate debridement of the extraction site and surrounding tissues. Residual inflammatory tissues prevent bone regeneration in the socket and must be thoroughly removed to achieve success.

ENDODONTIC PLATFORM VERSUS PROSTHODONTIC PLATFORM

Case 1

Figure 1. Preoperative radiograph of failing hemi-sected molar, No. 19.	Figure 2. Expansion of radiolucency surrounding No. 19.
Figure 3. Fractured Nos. 19 and 20; gingival tissues around No. 19 appear normal.	Figure 4. Significant granulation tissues on the mesial of the hemi-sected root.
Figure 5. Root removal along with granulation tissues created a large defect that required graftng with subsequent implant placement after healing.	Figure 6. Successful grafting followed by implant placement and restoration.

The young woman in the first photo was going to have implant therapy on the lower right (Figure 1). On the lower left is the hemi-sected molar where endodontic therapy had been performed and crowns successfully worn for many years; at the apex, however, a breakdown of the apical seal is evident.
Within 3 years, she had implants placed on the right side, and you can see the breakdown expanding around the hemi-sected root (Figure 2). It was not uncomfortable for the patient, so she chose to delay treatment. One year after that, she developed a fairly large lesion around that tooth but still would not allow its removal until it finally fractured (Figure 3). What is the end result of leaving that recurrent endodontic lesion untreated? Upon opening up the tooth and tissue, there was a large amount of granulation tissue on the mesial of that hemi-sected tooth. After excavating that granulation tissue, look at the size of the defect (Figure 4). As the radiograph showed, the lesion did not look that large, but left untreated, this type of damage is fairly routine.
While many times it is preferred to place an immediate implant in an extraction site, when this tooth was removed (Figure 5) a very large defect remained, and an immediate implant was unable to be placed. A graft was placed and time allowed for healing prior to proceeding with implant placement (Figure 6). It would have been much simpler to treat it earlier. Endodontic damage is a real possibility unless a tooth is treated in the early stages. The Journal of Endodontics shows that retreatment of failing endodontics has a less than 70% success rate. Implant reconstruction was the best alternative for this patient.

Case 2

Figure 7. No. 10 had a subcrestal fracture of the root from a hard popcorn kernel.	Figure 8. Initial healing response at one week after extraction, immediate implant placement, and temporary restoration.

Figure 9. Notice long interproximal contact between Nos. 9 and 10 along with the lack of taper at the gingival portion of No. 10.

This patient is a dentist with only one restoration in his mouth and a small, cantilevered lateral off of tooth No. 27. Unfortunately, he likes popcorn. He hit a hard kernel and tooth No. 10, a beautiful lateral incisor, was fractured subcrestally (Figure 7).
A differential treatment discussion might include endodontic therapy followed by orthodontic extrusion and possible gingival surgery; extraction followed by traditional fixed prosthodontics utilizing retainers and teeth Nos. 9 and 11; or extraction followed by an etched metal/porcelain fixed bridge.
Would you go back and prepare those 2 teeth for a fixed bridge? You would have to include a cuspid and recreate anterior guidance, and match the aesthetics between the 2 centrals. I believe an implant is the better choice since it provides a better platform.
The tooth is removed with particular care to preserve the labial plate of the socket. The implant is placed along with a temporary crown that serves his cosmetic and functional needs immediately. One week later the tissue is healing normally (Figure 8).
One of the challenges with immediate implants in the anterior region is that, in order to gain immediate stabilization of the implant necessary for immediate restoration, too large of a diameter is selected. The wider diameter provides more initial stability but can pinch off the proximal tissues of the papilla. An anterior extraction site is more of an oval shape, so a larger, round implant will impinge on the sensitive papillary tissue. A newer implant selection would be an Ankylos implant (DENTSPLY Friadent), which allows subcrestal placement of the implant, leaving additional interproximal space for the papillary tissues. A reduced offset of the diameter of the abutment, to the diameter of the implant, has been described as platform switching and can be achieved with several implant systems.
At the completion of therapy, a custom abutment was utilized to support the final restoration (Figure 9). But to be critical about this restoration, the mesial-distal width is a bit too wide at the gingival margin, where there should be more taper or cervical convergence. The patient was quite happy with the color match and function, and that he was able to have a fixed temporary crown during the healing phase of 6 months. Nevertheless, selection of an implant to satisfy the needs of immediate restoration can cause aesthetic compromises that must be discussed with the patient.

EXTRACTION AND IMMEDIATE IMPLANT PLACEMENT

Case 3

Figure 11. Notice the discrepancy between the natural gingival contours of No. 7 and the pink porcelain façade on No. 8.

The final case is an 62-year-old female. The radiograph (Figure 10a) shows tooth No. 7 had been previously treated with a post and core; it is failing. An existing bridge is supported by implants at teeth Nos. 8 to 10. The patient has a gingival façade on the 2 centrals that includes tooth No. 10 due to bone loss prior to implant placement (Figure 10b). Treatment options might include the following: the extraction of No. 7 followed by restoration of No. 6 with a PFM crown and a cantilever pontic for No. 7; the extraction of No. 7, followed by removal of the implant restorations on teeth Nos. 8 to 10, and replacement with a new implant bridge with No. 7 as a cantilever pontic; or the extraction of No. 7 with immediate implant placement and temporary restoration. In this case, the best approach is extraction of tooth No. 7 and implant therapy. Tissue health is good and the occlusal plane is normal (Figure 11). An implant restoration is going to give her the best prosthodontic platform to carry a tooth for the greatest number of years.

Figure 12. By using DEXIS Implant, it is possible to visualize the necessary angle correction on the radiograph prior to surgery.	Figure 13. The extreme thinness of the labial plate over No. 7 along with prior endodontic treatment increases the possibility of an existing perforation of the labial plate above No. 7 and will require reangulation of the apex of the implant palatally and distally to avoid the adjacent implant.

Prior to extraction and implant placement, it is important to begin with a set of mounted, diagnostic casts. These will be the primary prosthodontic aid. Imaging is the next step. With the proximity and angulation of the adjacent teeth and implants, a CBCT scan (i-CAT [Imaging Sciences International]) is the best image. The patient’s scan (Figure 12) indicates that the labial bone might be involved in this surgery due to its thinness.
Using the DEXIS digital x-ray system and DEXIS Implant (a separate software program), an outline schematic was produced that could be overlain on the x-rays (Figure 13). This overlay is specific to the 3.8 implant from the XiVE System (DENTSPLY Friadent). In this radiograph, the slight mesial cant to the root is evident, and the root approximation is a bit close. During surgery, the implant will be reangulated away from the apex of the extraction site and the adjacent implant using a biaxial technique, which is based on the external anatomy of a tooth and the multiple angles and axes. (The biaxial technique is demonstrated for optimal visualization in the author’s National Dental Network video, an excerpt of which is available on dentistrytoday.com). In cross-section, the long axis of the root is at a different angle than the angle of the facial portion of the anterior tooth. These 2 angles, the angle of the root and the angle of the coronal portion of the tooth, form the biaxial framework. As in preparing an anterior tooth for a crown when an incisal bevel is necessary, implant positioning also requires bi-angulation. Often the best prosthodontic angles are not the angles of the root, and you will need to reangulate the implant in an extraction socket. A review of the orthodontic literature will demonstrate the angles of all the roots are naturally diverging. There is no root that is straight up and down in the mouth. Invariably, you cannot go through the extraction site exactly, you need to engage the mesial, distal, or palatal aspect of the socket in almost every extraction site. It is rare that you can follow the exact anatomy of an extraction site in placing an implant. Understanding the anatomy of the alveolar bone and extraction socket along with the anatomy of the tooth that remains is key to having successful implants with great prosthetic results.

Operative Procedures

A flapless approach was planned, but if a flap became necessary, an attempt would be made not to elevate the flap over the existing implants. Local anesthetic was administered along with an anti-anxiety medicine (Ativan [Biovail Pharmaceuticals]). A contra-angled periotome was used to separate the periosteal fibers and to begin extraction of the root. The tooth was then manipulated with the Luxator instrument (Directa). By keeping a finger on the facial plate, you can determine if luxation is too aggressive. Maintaining this finger position supports the labial plate. The tooth was delivered with forceps using small twisting motions. Careful, small motions allow you to feel the movement of the root and determine the type of pressure that is being applied to the tooth. The finger support of the labial plate was maintained throughout the extraction. (See an excerpt of the National Dental Network video on dentistrytoday.com).
The socket was then carefully inspected and cleaned out using a curette. A small perforation could be felt at the apex of the socket. Using a periodontal probe, a slight dehiscence was found. The dehiscence occurred at about 13 mm. It was decided that a flap would not be opened since the dehiscence was very small and 8 to 10 mm below the crest of the bone. It is very important to identify whether a dehiscence is occurring, because as you place an implant at the extraction site, you will create a larger dehiscence unless the implant is repositioned away from the defect.

Implant Osteotomy

Figure 14. The initial position of the 2-mm twist drill is tilted buccally to firmly engage the slope of the palatal bone of the socket before rotating the handpiece palatally to parallel the long axis of the adjacent tooth.(Figures 14 to 16 are video screen-captures.)	Figure 15. Calibrated guide pins or trial implants that match each drill diameter allow precise implant positioning in extraction sites during each step of the procedure.

Drilling was begun to place the implant angulated palatally and a little distally away from the labial dehiscence and the tilted implant. Using a 2.0-mm twist drill, drilling was initially done without a drill guide. Many times in the anterior, the surgeon needs to rotate the drill to reangulate, and freehand surgery yields the best result. During drilling it is desirable to engage the palatal wall of the socket. The start of the osteotomy needs to be up 3 to 4 mm from the apex of the socket on the palatal wall at a slight angle, parallel to the incisal edge of the central and cuspid, tilting back toward the distal (Figure 14).
As the tip of the drill engages the palatal wall, a good purchase point is achieved. In this position, the implant osteotomy was redirected to the desired angle. On Figure 15, notice the distal angle to avoid the mesial aspect of the other implant. Using a calibrated guide pin from the XiVE System, the precise position of the implant was ensured. Drilling continued, and the 15-mm guide pin was used to measure when the head of the implant would be at a level of about 3 mm beneath the free gingival margin. An initial radiograph was made using the DEXIS digital system to provide an instantaneous view to confirm correct position. The drill sequence was continued with a 3.0 that expanded the osteotomy. The final drilling was achieved very gently with a 3.4 at a slow 850 rpm. The 15-mm, 3.4 guide pin was used to confirm position and stability. Placing implants into extraction sockets without reflecting a gingival flap requires precision and radiographic imaging. A calibrated guide pin matched to each size osteotomy drill is a critical tool for achieving precise positioning and for evaluating stability.

Implant Seating

Figure 16. Final seating of the implant by hand provides the clinician with the stability of the implant so that immediate restoration can be decided on.

Throat packs are always inserted to protect the patient’s airway in case small items fall into the mouth. The sterile implant was placed on the driver and secured. The implant was seated using 15 rpm. After placing the implant with a handpiece, final seating was accomplished with a direct implant driver to determine the insertion resistance as the implant is secured (Figure 16). All internally indexed implant systems have a marker or guide to ensure the implant is aligned in the right position to the labial. The final step is to line up the index marker to the facial.

Immediate Temporary Crown

Figure 17. The depth and angulation of the immediate implant provides a secure prosthetic platform for a temporary restoration.	Figure 18. Using a biaxial technique for implant positioning maintains the natural gingival contours in comparison to prior techniques that required screw-retained restorations and pink procelain façades to recreate gingival aesthetics.

Figure 19. Notice the maintenance of gingival symmetry symmetrical to No. 6 versus the pink porcelain of No. 8.

The temporary abutment that came with the implant was placed back on the implant. A radiograph was taken of the implant in position (Figure 17). A temporary cap was placed on the abutment made from Integrity (DENTSPLY Caulk), while an implant analog was used in the dental lab to immediately fabricate a temporary crown that attaches accurately to the implant. The temporary crown is placed directly on the abutment (Figure 18). Anterior guidance and occlusion, including lateral excursions, are checked prior to cementing. Cotton was inserted in the implant access hole and TempBond (Kerr) used to cement the temporary. The fit was examined to ensure there is no excess cement under the gingival margin that could cause irritation (Figure 19).

CONCLUSION

Precise positioning of implants is necessary to achieve predictable, aesthetic, and durable treatment outcomes and patient satisfaction. The integration of anatomic knowledge, surgical technique, and prosthodontic reconstruction is the ultimate goal in implant therapy.

Dr. McGarry received his DDS in 1975 from UMKC School of Dentistry, his certificate in prosthodontics in 1978 from the Veterans Administration Hospital-San Francisco, and became a Diplomate of the American Board of Prosthodontics in 1991. He is a Fellow in the American College of Prosthodontists and has served as president of the College. He currently holds an appointment as an associate professor at the University of Oklahoma School of Dentistry and adjunct assistant professor at the University of Illinois School of Dentistry. He maintains a full-time private practice limited to prosthodontics and is the clinical director for the McGarry Implant Institute. He can be reached at mcgarry@implantassociates.net or (405) 755-7777.