Ask Dr. Christensen

April 1, 2003
In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers.

by Gordon J. Christensen, DDS, MSD, PhD

In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers. If you would like to submit a question to Dr. Christensen, please send an email to [email protected].

Question ...
Recently, I referred a patient to a periodontist for a hemisection of a lower-right, second- molar bridge abutment, to help support a prosthesis from tooth 29 to tooth 31. The distal root of the molar abutment appears to be very strong, and it also appears radiographically healthy. The mesial root of the molar abutment was cracked, as determined by radiograph, and it was infected and painful. The mesial root was hemisected. What longevity can be expected in such a situation for the tooth and the bridge, and what precautions should I give the patient?

Answer from Dr. Christensen ...
I have accomplished many tooth hemisections over the years, and I have observed many successes and some failures. Long-term results have varied considerably. The situation you described is the potential salvage of an expensive fixed prosthesis. If the patient were to have the tooth extracted, the entire fixed prosthesis would be destroyed. An implant or two would be indicated, and, if adjacent teeth are present, a new four-unit, fixed prosthesis or four single crowns would be required. The average cost of this replacement would be $6,000 to $8,000 (U.S.), or, if a four-unit fixed prosthesis could be placed without implants, the average cost would range from $2,400 to $4,000. For the typical dental patient, these sums of money are not a small consideration. An attractive alternative is hemisection of tooth 18 and whatever repair of the apical portion of the remaining tooth structure is needed. The cost of a typical hemisection is minimal compared to reconstructing the entire area of the mouth again.

What conditions should be considered before suggesting a hemisection? The following are my own requirements for consideration of a hemisection, whether it is to salvage a prosthesis, or to support a new fixed prosthesis.

1 The tooth root(s) to be saved must not look suspicious in any way.

2 The patient should not be a bruxer or clencher.

3 The supporting bone around the roots to be retained should be excellent.

4 Endodontic therapy in the remaining root(s) should be acceptable.

5 The periodontal health around the root(s) to be saved should be acceptable.

6 The remaining coronal tooth structure on the root(s) to be retained should be capable of supporting the planned prosthesis or crowns. At least one-half of the coronal tooth structure should be remaining before build-up for optimum potential for success.

7 If salvage of a prosthesis supported by the root(s) is planned, the prosthesis should be in acceptable condition, and the prosthesis should be expected to serve for a reasonable number of years.

Even when all of the above characteristics are fulfilled, I still have had failure of hemisected tooth roots. Patients should be advised that the prognosis for hemisected teeth and the restorations supported by them is guarded. If the patient still wants to go ahead with the treatment after hearing your suggestions about hemisection, do your best to provide a service that will justify the fee. In my opinion — and with significant clinical experience — only about 50 percent of hemisected teeth and the restorations placed on them have served more than five years. However, I have had numerous patients for whom hemisected teeth have served over 25 years. Please be sure that the patient understands that the service has an unknown longevity, but that you will do your very best.

Question ...
Some clinicians have told me that mandibular dentures can be stabilized and retained by only two implants placed under an old or a new denture. However, I also have been told by another "expert" that such treatment is not indicated and that it fails soon after placement. How do you feel about the potential for success of an overdenture placed over two implants?

Answer from Dr. Christensen ...
You have asked about treatment that I have accomplished many times over more than 15 years. The following are my clinical opinions about an overdenture placed over two implants. Overall, I have had wonderful success with two implants placed under both previously-made and new dentures. I have experienced more success when the implants are allowed to serve independently and they are not connected together. Various types of attachments can be placed on the individual implants. I prefer small-ball attachments placed on the implants, with "o"-ring rubber attachments placed in the denture base. Many implant companies make such attachments, and a company that has this type of attachment for various brands of implants is Attachments International in San Mateo, Calif. (800) 999-3003.

This type of attachment allows flexibility in the movements of the denture. If the patient chews on something hard, the denture base can move apically and seat more firmly on the gingival tissues. Severe force is not placed on the implants. If an implant fails, a new implant can be placed, while the remaining one serves alone until the new one can be used with a rebased denture. Over many years of using this treatment as my favorite relatively low-cost way to stabilize and add retention to a lower denture, I have had very few implants fail. However, when the two implants are connected together, and/or a rigid attachment is used on the implants and superstructure, I have had significant failure.

Two Practical Clinical Courses videos are related to the questions asked in this editorial — V2392, "Prosthodontics for Implants Simplified" and V4796, "Dr. Christensen's Most Frequent Failures, And How to Avoid Them."

Dr. Christensen is a practicing prosthodontist in Provo, Utah. He is the founder and director of Practical Clinical Courses, an international continuing-education organization for dental professionals initiated in 1981. Dr. Christensen is a co-founder (with his wife, Rella) and senior consultant of Clinical Research Associates, which, since 1976, has conducted research in all areas of dentistry and publishes its findings to the dental profession in the well-known CRA Newsletter. He is an adjunct professor at Brigham Young University and the University of Utah. Dr. Christensen has educational videos and hands-on courses on the above topics available through Practical Clinical Courses. Call (800) 223-6569 or (801) 226-6569.

Dr. Christensen's views do not necessarily reflect the opinions of the editorial staff at Dental Economics.

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