Written by Larry G. Hubbard, DDS Monday, 28 February 2005 19:00
The field of implant dentistry has expanded to include implant diameters less than 3.5 mm and greater than 4.3 mm. This article will discuss the advantages that implants less than 3 mm in diameter offer in solving patient needs. Several companies offer these "mini-implants," such as Imtec's MDI and IntraLock's MDL series. While the FDA has approved some minis for interim use, Imtec's MDI are cleared for long-term stabilization. That being said, the practicing dentist is free to use his or her clinical judgment in implant selection.
Two different uses are presented. One is the severely limited space that often presents when replacing maxillary lateral incisors, and the other is the growing acceptance of these implants as immediate load implants supporting lower dentures.
CASE REPORT 1
|Figure 1. Limited space for laterals.||Figure 2. Treatment partial replacing laterals.|
J was a bright, enthusiastic 17-year-old who had undergone an extended period of orthodontics by a local orthodontist. As seen in Figure 1, the space to replace the congenitally missing laterals was very limited. An even greater concern was the fact that the cuspids and centrals were apically tipped toward each other. J and her parents were informed of the difficulty of the case. It was recommended that the patient undergo orthodontics again to decrease the approximation of the apices. J and her parents stated they were aware of the problem and had undergone longer orthodontic treatment in a failed attempt to improve the future implant sites. It was agreed to place reduced-diameter implants to allow J to discontinue using her temporary treatment partial. J was extremely distressed with the partial, or as she called it, her "fake teeth," even though it looked very lifelike (Figure 2). To J, the thought of anyone, even the dentist, seeing her with 2 missing teeth was unbearable.
|Figure 3. Sounding bone with periodontal probe.||Figure 4. Dermal punch 2 mm in diameter.|
Using the Dexis Deximplant program, it was determined that a 1.8 x 10-mm implant could be placed in the No. 7 site, and a 1.8 x 13-mm implant was chosen to support the crowns. The bone was sounded with a periodontal probe and yielded a 2-mm gingival thickness (Figure 3). There are different heights of polished collars to accommodate different tissue thickness. A 2-mm dermal punch was used to remove a plug of gingiva to allow a very minimal inspection of the bone (Figure 4).
|Figure 5. Spirex drill penetrating cortical plate.||Figure 6. Implant placed.|
One of the many advantages of the various mini-implant systems is the simplified placement. A sterile, single-use spirex drill is used to penetrate the cortical plate (Figure 5). An osteotomy is not performed as with traditional implants, only a pilot hole is created for the self-tapping screw that will be placed (Figure 6). Radiographs are used to verify correct angulation. The maxillary bone is softer than most mandibular bone. The implant is placed to its proper position.
|Figure 7. Both implants in position.|
The same protocol was used to place the implant in the No. 10 site (Figure 7). It should be stressed that while mini-implants offer the advantage of simplified placement, proper continuing education is needed to perform any new dental procedure and is offered by various manufacturers.
|Figure 8. Crowntek provisional crown.|
Temporization offered a challenge in this particular case. Traditional polycarbonate provisional crowns were too dark for this young lady's bleached teeth. Fortunately, Crowntek provisional crowns (GC America) have recently been offered to the dental profession. They are thinner than conventional provisional crowns and are offered in many smaller sizes. It was even necessary to reduce the proximals (Figure 8).
|Figure 9. Provisional crowns in place but not in occlusion.|
The Crowntek provisional crowns were taken slightly out of occlusion. J also was instructed on placing minimal pressure on the implants for the next several months (Figure 9). Later, an impression will be made utilizing the appropriate implant impression coping and analogs, and porcelain crowns will be fabricated.
In about an hour, a patient's problem was solved. On the recheck appointment, J beamed with joy at not having "fake teeth" anymore. Some say dentistry is often thankless, but that day was not one of them.
|Figure 10. Resorbed mandibular ridge.|
Mr. M was an 83-year-old gentleman with a problem. He could no longer enjoy social engagements due to the instability of his lower denture. His lower denture fit well, and the occlusion was satisfactory; however, as seen in Figure 10, the ridge was resorbed and provided a poor base for a lower denture. In dentistry, we often think we are treating teeth or edentulous jaws; however, we are really treating people. In Mr. M's case, he did not want implants; he wanted a solution to his unstable denture. Actually, Mr. M's problem was his inability to socialize around food.
After a full discussion with Mr. M and his wife and after an informed consent, they decided to try having dental implants placed to solve the instability problem of the lower denture. A concern developed while discussing different implant types. The option of placing standard-size implants and allowing 6 months for healing was rejected. In today's instant gratification society, patients often are reluctant to wait 6 months. Mr. M quite humorously stated that at age 83, 6 months is much longer for him than for this author. Mr. M's wife raised the fact that he also fatigued easily and wasn't able to undergo an extended surgical procedure.
The possibility of using mini-implants to stabilize the lower denture was presented and accepted. An informed consent DVD is available and was used in addition to written material and models. It was discussed that on very rare occasions, the implant can break. This would prove to be fortuitous, as this in fact is what happened.
|Figure 11. "Mini ceph."||Figure 12. Planned implant sites.|
A standard panoramic film was taken. In addition, a "mini-ceph" was taken of the mandibular anterior region (Figure 11). An occlusal film taped to a tongue depressor yields a cross-sectional view of the area, which helps in implant angulation. This is a technique taught by Dr. Charles English at Imtec mini-implant seminars. The mental nerve often loops anterior to the nerve's exit. The mental bundle was palpated, and 1 spot 7 mm from each bundle was marked with a sanitary marking stick (Great Plains Dental). The remaining distance was divided and marked (Figure 12).
|Figure 13. Providing a pilot hole.||Figure 14. Finger wrench advancing implant.|
|Figure 15. Improved mechanical advantage with thumb wrench.||Figure 16. First implant placed.|
|Figure 17. Ratchet seating implant.|
The single-use, sterile spirex drill was used to perforate the cortical plate but not to perform an osteotomy. The goal was to provide a pilot hole for the self-tapping implant (Figure 13). The finger wrench was used to advance the implant slowly until no advancement occurs (Figure 14). The next step was to use the thumb wrench, which improves the mechanical advantage (Figure 15). There should be resistance to the wrenches, or the possibility of success is very low. The implant was advanced until the square head was slightly subgingival (Figure 16). This process was repeated for the other 2 implants on the right. The most distal implant on the left was difficult to ad-vance. The ratchet even had difficulty in placing the implant (Figure 17). The goal is to have all the implants parallel. The implant would not seat sufficiently, and in a futile attempt to seat the implant completely, the implant separated. Fortunately, we had discussed in the informed consent that there was a possibility of implant separation. In dentistry, dentists sometimes resent informed consent as something else to worry about. In this case, since it had been mentioned, the patient and wife were informed of what happened and treatment was continued.
|Figure 18. Final arrangement of implants.|
Of the numerous implants the author has placed, this is the only implant that has separated. On reflection, the implant should have been backed out when severe resistance was felt with the ratchet wrench. After again locating the mental bundle with palpation, another implant was placed distal to the separated implant (Figure 18). The metal O-ring caps were placed on the lower denture. There was a look of satisfaction on Mr. M's face when the denture was placed and wouldn't slide sideways.
|Figure 19. Metal O-ring caps in place.|
The placement of 5 im-plants in this case took less than 30 minutes. The placement of the O-ring caps took an additional 45 minutes (Figure 19), but this gave Mr. M a chance to rest. On his recheck appointment, the denture was stable, and Mr. M and his wife were extremely satisfied.
There are many solutions to various dental problems. As this article has demonstrated, sometimes they are mini solutions.
Dr. Hubbard maintains a private practice that concentrates on cosmetic and comprehensive care in Statesboro, Ga. He is a member of the American Academy of Implant Dentistry (AAID) and has completed the Medical College of Georgia/AAID's maxi course in implantology. He is not affiliated with any company that markets dental implants. Dr. Hubbard can be reached by phone at (912) 764-9891 or by fax at (912) 489-3491.
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