Replacement of Single Missing Molar Teeth with Dental Implants
Thomas J. Salinas, DDS
Traditional perspectives on replacement of single teeth show that first and second molar adult teeth are frequently afflicted.1 Replacement of missing molars is vital to the preservation of a stable posterior occlusion. This may be accomplished with a fixed partial denture (FPD) or a single-tooth implant restoration. Replacement using an FPD remains an acceptable standard.2
If replacement of a missing molar with a single-tooth implant restoration is selected, additional variables may further challenge the details of treatment. Replacement of a missing tooth with one or two implants has been controversial and it may appear that it is more appropriate to use 2 rather than 1 implant to replace a posterior tooth. In spaces with less than 10mm mesiodistal surgical dimension, 2 implants may not be appropriate. Encroachment of the interimplant distance closer than 3mm may also accelerate the rate of bone resorption in these areas.3 In these case, comparably wider implants (ie, 5mm-diameter) may be a better choice. Long-term success of wide-diameter implants has to emerged with mixed results.4,5 Theories have been proposed that the shock absorbing capacity of the bone surrounding wide-diameter implants is different from that surrounding implants of a standard diameter.6 Additional aspects have indicated that these implants were installed into porous bone in the posterior mandible or maxilla and had comparably poor survival rates in comparison to standard-diameter implants in more dense bone.7
In some cases, it may be feasible to engage a buccal or lingual cortical plate with a wide-diameter implant (eg 6mm) to further stabilize the fixture. By using wider-diameter implants, the emergence of the restoration, either screw-retained or cemented, is comparably less abrupt. This further facilitates hygiene procedures and maintenance of soft tissue health. Deciding factors of success predicate at least 10mm or implant length, canine protected occlusion, adequate buccal/lingual bone volume, relatively dense bone quality, and nonsmoker. If installation is anticipated as an immediate procedure, great care should be taken to install the fixture in the interseptal bone facilitating a central position rather than in any one molar root socket. This affords ideal stress distribution and minimizes soft tissue and prosthetic complications. If installation is to be approached as a delayed procedure, sufficient time (usually 6 to 8 weeks or more) should transpire to allow bone remodeling for primary implant stability. Either a one or two stage surgical approach may offer similar success rates. Affirmation of osseointegration is essential, and may be determined by application of torque (>32 Ncm) to the gingival abutment or cover screw. Care should be taken in these circumstances when the fixture has been installed in close proximity to the inferior alveolar canal or maxillary sinuses.
If more than one adjacent tooth is to be replaced and is to be independent, care should be taken to determine whether simultaneous path of placement or sequential placement permits development of adequate proximal contacts. In cases when internal-connection implants are placed and result in slightly convergent implant axes, careful surgical and prosthetic planning is crucial for long-term success.
*Assistant Professor, Department of Otolaryngology, University of Nebraska medical Center, Omaha, Nebraska.
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- Salinas TJ. Three-unit fixed partial dentures versus single-tooth implant restorations. Pract Proced Aesthet Dent 2003;15(5):372.
- Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-implant bone crest. J Periodontol 2000;71(4):546-549.
- Shin SW, Bryant SR, Zarb GA. A retrospective study on the treatment outcome of wide-bodied implants. Int J Prosthodont 2004;17(1):52-58.
- Mordenfeld MH, Johansson A, Hedin M, et al. A retrospective clinical study of wide diameter implants used in posterior edentulous areas. Int J Oral Maxillofac Impl 2004;19(3):387-392.
- Aparicio C, Orozco P. Use of 5mm diameter implants: Periotest values related to a clinical and radiographic evaluation. Clin Oral Impl Res 1998;9(6):398-406.
- Ivanoff CJ, Grondhal K, Sennerby L, et al. Influence of variations in implant diameters: A 3 to 5 year retrospective clinical report. Int J Oral Maxillofac Impl 1999;14(2):173-180.