By Jon Julian, D.D.S.
Dentists need to be creative in their treatment planning in order to arrive at successful outcomes.
When a restoring doctor is faced with a missing lower incisor or incisors, the spacing is often problematic. Consider that the average lower incisor is approximately 5 mm in mesiodistal width. When you want to place a 3.5 mm diameter implant, it only leaves you .75 mm on either side—a tight fit. Ideally you would want at least 7.5 mm for that implant allowing 2mm from the proximal surface of the implant to the adjacent tooth. If crowding exists, the problem just gets worse. I would like to show you three different case scenarios of restoring in crowded areas where our goals were to create functionality, preserve esthetics, and allow for easy access for good oral hygiene.
This case presented with periodontal failing teeth numbers 25, 26, and 27 that were splinted together with composite. When the teeth were removed, we measured 14 mm of mesiodistal space available for implants and crowns. An ideal space analysis would suggest 28 2mm 3.5 3mm 3.5 3mm 3.5 2mm 24 or 20.5 mm needed for three implants comfortably. Being 6.5 mm short forced us to think of other options.
We could place one implant for 25 and one for 27 and construct a three-unit bridge—a traditional solution with only one drawback: hygiene is harder to maintain with a pontic space that collects food and debris. Our solution was to place a single implant supporting two crowns for 25 and 26. By centering the implant and allowing the lab to create a two-crown look on a single abutment, the patient has the ability to floss as if there were two crowns there. Esthetically this is as good as or better than a bridge would have been, as a distinct separation occurs between 26 and 27. Our lab did an exceptional job here to mimic the teeth on the other side of the midline.
Now let’s consider the patient who was missing numbers 24 and 25. The mesio-distal space available was 8 mm. As two implants side by side occupy 7 mm, this is not a workable situation. We could choose to place a bridge from 22 to 27, but that involves reducing virgin teeth; and it involves two pontics and splinting teeth together which would make hygiene even more difficult for this patient. Therefore an ANKYLOS® 3.5 x 11 mm implant was placed in the mesio-distal center of the space between 23 and 26. A single large posterior balance abutment was used to support the slightly crowded and overlapping crowns in the final result. Cosmetically, we created a natural appearance that functioned as well as two separate crowns with the added benefit of being able to floss each side. The patient can keep the restoration clean as easily as any single tooth.
The last case is a real esthetic and functional challenge. This patient presented with advanced periodontal disease especially in the maxilla and severe crowding in the mandible (even though she was already missing 26). A maxillary denture combined with lower restorative work was planned. We wanted to correct the position of 27 and replace 25 and 24. To arrive at an esthetically pleasing finish we also elected to crown 22 and 23.
The mesial of 23 and 24 needed to be reduced severely in order to have 7 to 8 mm of mesio-distal space to fill with two crowns. We extracted 24 and 25 and prepared 22, 23, and 27 for crowns. We also reduced the mesio contour of 28. An ANKYLOS 3.5 x 11 mm implant was centered and well below the crest of existing bone in order to give a great emergence profile. A temporary bridge was placed until after the healing and integration phase was well under way—approximately three months. A final impression was taken at this time and three weeks later the final crowns were seated. As you can see by the photos, we accomplished our goal of aligning and uprighting all the mandibular anterior teeth (this is opposing a temporary denture at the time of the photos). Hygiene can be easily maintained as flossing the two crown/one implant abutment complex is as easy as flossing any single crown.
In each of these cases we were able to avoid a bridge with pontics and to preserve teeth by utilizing a single implant that supported a two-crown prosthesis. The esthetics were good and the hygienically maintained restoration (which leads to long term success) was much better than a traditional bridge would have allowed. The implants were placed into good quality bone (type I or II). ANKYLOS implants are especially good in this situation as they can be placed far enough sub-crestal to enhance the emergence profile. Their strong morse taper, 360-degree conical connector withstands the lateral forces without the propensity for losing crestal bone, as found with most other implant systems. It does take a good quality laboratory to customize the crowns and give the appearance of two separate crowns on the single abutment.
So please, always measure the mesio-distal space available when planning your cases. Remember to allow 2 mm between teeth and implants and 3 mm between two adjacent implants. You shouldn’t have this crowding problem with other teeth, just the mandibular incisors. With a little creative thinking, the right implant system, and a good laboratory, you will be able to create functional, esthetic and cleansable restorations.
Jon Julian received his D.D.S. degree from theUniversity of Kansas City Dental School in 1978 and maintains a practice in McPherson, Kansas. He is a member of the Dr. Dick Barnes Group and is the instructor of the Implant EZ seminars.