Fixed

Treatment Considerations of Fixed Prosthetic Restorations of the Compromised Dentition vs. Alternate Fixed Implant-Supported Options

Peter F. Johnson, DMD

Peter F. Johnson, DMD, is a board-certified prosthodontist in private practice in La Mesa, Calif., and is a clinical associate professor of prosthodontics at the University of Southern California School of Dentistry.

Copyright 2003 Journal of the California Dental Association.

Disclosure
Dr. Johnson is a member of ITI and has received honoraria from Straumann and 3i.

The treatment of the patient "A.K." needs to be evaluated with regard to what was done, what alternatives could have been done in light of current treatment modalities, and whether the alternative treatments would have had an effect on the patient’s prognosis and additional treatment. Evaluating the use of the fixed prosthodontic restorations, this patient had periodontally involved teeth, caries, bone loss and secondary occlusal trauma, and mobile teeth. Fixed restorations were fabricated using a hemisected tooth, endodontically treated teeth with post-cores, subperiosteal and endosteal implants, and splinted natural teeth.

Long-term studies of fixed prosthodontic restorations utilizing teeth or implants for support and anchorage are not necessarily parallel in their methods, criteria of success, and patient populations. Review of the existing literature for indications of patient response to various treatments can provide insight into making alternative treatment choices.

Evidence for Fixed Restorations Supported by Teeth

The long-term survival of tooth-supported fixed partial denture restorations is very good in the first five years, with success rates of 95 percent and better. However, these results drop to 68 percent to 85 percent after 15 years.^1-3 Two meta-analysis studies by Creugers⁴ and Scurria⁵ also show that the cumulative data of seven and eight studies show 74 percent and 69 percent success respectively after 15 years.

Goodacre compiled data from these and other studies and reported that the main causes of failure for fixed prostheses were caries (33 percent), loss of retention (26 percent), periodontal loss (11 percent), and abutment fracture (4 percent). In addition, this same review showed that there was increased failure with splinting teeth, longer edentulous spans, cantilevered pontics, endodontically treated teeth, and fixed partial dentures that included both anterior and posterior teeth.⁶

When using root-resected molars, Blomlof and colleagues⁷ reported 10-year results of 56 percent in periodontally compromised patients, but as high as 89 percent in healthy patients. Basten and colleagues⁸ reported a 92 percent 12-year survival rate for resected molars. Most failures were due to caries, endodontic failure, or strategic treatment planning decisions. However, none of these teeth were used for fixed bridge abutments where the stress on the resected teeth would be greater and presumably cause a lower success rate.

Evidence for Implant-Supported Options

The current fixed alternatives to tooth-supported fixed partial dentures include using dental implants, either as free-standing single or multiple restorations, as bridges or connected to natural teeth. In a 10-year study, Parien and colleagues⁹ reported an 89 percent success rate for implants and an 82 percent success rate for prostheses in the posterior mandible. Fewer complications were seen in premolar than molar areas, and with cemented single crowns than screw-retained crowns.

Other, more recent studies of single-tooth restorations have reported success rates of 98 percent¹⁰ and 96 percent¹¹ for external hex implants and 99 percent for internal tapered implants.¹² In the later study of posterior restorations, failures were noted only in the mandibular molar area, and only 2 percent of the cemented restorations had any complications. In addition, 108 of the restored implants were in areas with multiple contiguous implants, with only one reported failure.

Additional studies report that fixed prosthetic restorations including a pontic on implants in partially edentulous patients also have high success rates: 97 percent in both a 12-year study¹³ and a 15-year study.¹⁴ Restorations where implants are joined to natural teeth have also been successful: 94 percent in a 15-year study¹⁴ and 90 percent in an eight-year study.¹⁵

Two studies evaluating freestanding implant fixed partial dentures against implant-tooth fixed partial dentures in the same patient show no significant differences in bridge retention.^16,17 Implant loss (5 percent), periapical lesions (3.5 percent), tooth fracture (0.6 percent), and tooth extraction due to decay or periodontitis (1 percent) were reasons for tooth-implant prosthesis failure.¹⁸ This same study also noted tooth intrusion (3.4 percent) and crown cement failures (8 percent). Garcia and Oesterle¹⁹ described a survey where respondents reported a 3.5 percent occurrence of natural tooth intrusion. However, Fugazzotto and colleagues²⁰ had only nine intrusion problems in 3,096 screw-fixed attachments. These tooth intrusions were all associated with fractured or lost screws, while Lindhe and colleagues reported 5 percent intrusion, which was all associated with nonrigid connections.²¹ Rigid connection did not appear to allow natural tooth intrusion to occur.²¹ A majority of the complications of tooth-implanted supported fixed partial dentures seemed to occur with the tooth abutments.

Biological Expenditure of Abutment Teeth

In addition to the clinical success and economic cost of alternative therapies, the biological harm of the treatment must be evaluated. Aquilino and colleagues²² looked at the 10-year survival of teeth adjacent to bounded edentulous spaces, edentulous areas with teeth on either side. Survival for patients treated with fixed partial dentures was 92 percent of the abutment teeth; for untreated spaces, 81 percent of the adjacent teeth; and for removable partial dentures, 56 percent of the bordering teeth.

In a parallel study, Preist²³ restored implants placed in bounded edentulous spaces and looked at the survival of the adjoining teeth. Only a single tooth was lost (the fracture of an endodontically treated tooth), and one tooth was restored, resulting in 99.5 percent survival of adjacent teeth, with only 1 percent needing any treatment. The non-involvement of the boundary teeth in the restoration seemed to have a most advantageous effect and would decrease the future liability of these teeth needing further care.

Fugazzotto reported that root-resected teeth appear to have comparable success rates compared to single implants.²⁴ However, his reported success rates for the resected teeth were 10 percent greater than the studies previously cited. He also noted that most failures in both groups were in the terminal molar positions of the arch.

Currently, the replacement treatment for patient A.K. in the mandibular left edentulous area would probably be done with a single cylindrical implant restoration. This would enhance the prognosis of the distal hemisected molar and the full crown restoration anterior to the bounded edentulous space. A decision would need to be made on whether to replace hemisected No. 18 with an implant restoration at the time of initial treatment or later, at the time of its possible failure. Due to the precarious nature of terminal root-amputated teeth, this would probably be done as part of the initial therapy.

The choice of restoring individual units would have restricted any future needed treatment to the single affected tooth or implant. Also, it would have precluded the subsequent treatments that occurred with A.K. of the subperiosteal implant with double-abutted premolars, the root-form implant to tooth fixed partial dentures, and the cantilever splint with subsequent caries on the distal abutment, even though these treatments were the state-of-the-art at the time they were performed.

The mandibular right implant fixed partial denture would be a current treatment choice in light of the progressive bone loss on these posterior teeth. The choice of the implant fixed partial dentures does not involve or compromise any of the remaining teeth in the arch.

Another current treatment alternative to consider for patient A.K. is maxillary bilateral sinus grafts and implant replacement of the maxillary molars before their subsequent loss to both attachment loss and caries. This would have conserved more alveolar bone, provided more stable posterior support and less trauma to the anterior teeth, and prevented the need for a maxillary removable prosthesis. This alternative is much easier to advocate 25 years after this patient’s treatment inception.

Considerations for the Complete Arch Implant-Supported Option

Evaluation of a patient regarding the future progression of disease and the stability of proposed restorations at any single point in time is nearly impossible. A treatment decision that often needs to be made in patients with refractory periodontal disease and a high caries rate is when is it appropriate to extract all the remaining teeth and use the residual bone to fabricate a fixed full-arch implant restoration.

This future alternative can be anticipated with the placement of the implants in the partially edentulous patient and the use of these implants with additional fixtures to convert to the full-arch prosthesis. In a 15-year study of edentulous patient treated with mandibular fixed prostheses, 99 percent of the implants were successful and 100 percent of the prostheses were functional.²⁵ A full-arch fixed prosthesis usually needs much fewer repairs and adjustments than a removable prosthesis.²⁶

Comparing the available literature, even with its limitations, fixed implant restorations of a single tooth, freestanding or connected to teeth with fixed partial dentures, or a full-arch design have a very high success rate, and appear to be much more successful than natural-tooth-supported fixed partial dentures after a 15-year period. The implant restorations are more maintainable in patients with age- or pharmacologically induced xerostomia and geriatric reduced dexterity, because of the lack of caries and pulpal disease. The more frequent need for retreatment of the natural teeth could also counterbalance the possible greater initial financial cost of the implant restorations.

To enhance the prognosis, it is best to choose treatments that seem to have the best success. Regarding the choice of conventional versus implant fixed restorations, this information is now becoming available. The consideration of alternatives needs to take into account the optimal longevity, the probability the restoration will need additional care in the future, and the affect the current therapy may have on future needed treatment.

References

1. Lindquist E, Karlson S, Success rate and failures for fixed partial dentures after 20 years of service: Part I. Int J Prosthodont 11(2):133-8, 1998.

2. Valderhaug J, A 15-year clinical evaluation of fixed prosthodontics. Acta Odontol Scand 49(1):35-40, 1991.

3. Walton TR, An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 1. Outcome. Int J Prosthodont 15(5):439-45, 2002.

4. Creugers NHJ, Kayser AF, van’t Hof MA, A meta-analysis of durability data on conventional fixed bridges. Community Dent Oral Epidemiol 22:448-452, 1994.

5. Scurria MS, Bader JD, Shugars DA, Meta-analysis of fixed partial denture survival: Prostheses and abutments. J Prosthet Dent 79:459-64, 1998.

6. Goodacre CJ, Lecture, Odontic Seminar, USC Continuing Education, San Diego.

7. Blomlof L, Jansson L, et al, Prognosis and mortality of root-resected molars. Int J Periodontics Restorative Dent 17(2):190-201, 1997.

8. Basten CH, Ammons WF Jr, Persson R, Long term evaluation of root-resected molars: a retrospective study. Int J Periodontics Restorative Dent 16(3):206-19, 1996.

9. Parein AM, Eckert SE, et al, Implant reconstruction in the posterior mandible: a long-term retrospective study. J Prosthet Dent 78(1):34-42, 1997.

10. Scholander S, A retrospective evaluation of 259 single-tooth replacements by the use of Brånemark implants. Int J Prosthodont 12(6):483-91, 1999.

11. Naert I, Koutsikakis G, et al, Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study. Clin Implant Dent Relat Res 2(4):209-18, 2000.

12. Levine RA, Clem D, et al, Multicenter retrospective analysis of the solid-screw ITI implant for posterior single-tooth replacements. Int J Oral Maxillofac Implants. 17(4):550-6, 1999.

13. Wyatt CC, Zarb GA, Treatment outcomes of patients with implant-supported fixed partial prostheses. Int J Oral Maxillofac Implants 13(2):204-11, 1998.

14. Naert I, Koutsikakis G, et al, Biologic outcome of implant-supported restorations in the treatment of partial edentulism. Part I: a longitudinal clinical evaluation. Clin Oral Implants Res 13(4):381-9, 2002.

15. Kindberg H, Gunne J, Kronstrom M, Tooth- and implant-supported prostheses: a retrospective clinical follow-up to 8 years. Int J Prosthodont 14(6):575-81, 2001.

16. Gunne J, Astrand P, et al, Tooth-implant and implant supported fixed partial dentures: a 10-year report. Int J Prosthodont 12(3):216-21, 1999.

17. Hosny M, Duyck J, et al, Within-subject comparison between connected and nonconnected tooth-to-implant fixed prostheses: up to 14-year follow-up study. Int J Prosthodont 13(4):340-6, 2000.

18. Naert IE, Duyck JA, et al, Freestanding and tooth-implant connected prostheses in the treatment of partially edentulous patients Part II: An up to 15-years radiographic evaluation. Clin Oral Implants Res 12(3):245-51, 2001.

19. Garcia LT, Oesterle LJ, Natural tooth intrusion phenomenon with implants: a survey. Int J Oral Maxillofac Implants 13(2):227-31, 1998.

20. Fugazzotto PA, Kirsch A, et al, Implant/tooth-connected restorations utilizing screw-fixed attachments: a survey of 3,096 sites in function for 3 to 14 years. Int J Oral Maxillofac Implants 14(6):819-23, 1999.

21. Lindh T, Dahlgren S, et al, Tooth-implant supported fixed prostheses: a retrospective multicenter study. Int J Prosthodont 14(4):321-8, 2001.

22. Aquilino SA, Shugars DA, et al, Ten-year survival rates of teeth adjacent to treated and untreated posterior bounded edentulous spaces. J Prosthet Dent 85(5):455-60, 2001.

23. Priest G, Single-tooth implants and their role in preserving remaining teeth: a 10-year survival study. Int J Oral Maxillofac Implants 14(2):181-8, 1999.

24. Fugazzotto PA, A comparison of the success of root resected molars and molar position implants in function in a private practice: results of up to 15-plus years. J Periodontol 72(8):1113-23, 2001.

25. Lindquist LW, Carlsson GE, Jemt T, A prospective 15-year follow-up study of mandibular fixed prostheses supported by osseointegrated implants. Clinical results and marginal bone loss. Clin Oral Implants Res 7(4):329-36, 1996.

26. Walton JN, MacEntee MI, Problems associated with prostheses on implants: a retrospective study. J Prosthet Dent 71(3):283-8, 1994.

To request a printed copy of this article, please contact/Peter F. Johnson, DMD, 5565 Grossmont Center Drive, Suite 110, La Mesa, CA 91942-3021.

Legends

Figure 1. Paradigm shift in implant therapy: Patient's left side was restored in 1996, to replace a failed bridge Nos. 18 x 20 x 22 due to caries on No. 20. Restoration included two implants in No. 19 mesial and No. 20 positions, and two CSR attachments connecting the implant segment to crowned natural teeth, constructing a five-unit prosthesis. Patient’s right side was restored in 1998 replacing a carious No. 29 abutment of a bridge Nos. 29 x 31. A satisfactory abutment crown was left on tooth No. 31, and individual implants were restored replacing No. 29 and 30. This restored all teeth as single units, and tooth No. 28 was not involved.

Figures 2a and b. Failure of double abutted bridge Nos. 18 x 21 x 22, with the
loss of tooth No. 21 due to subosseous caries. The patient was restored by leaving a satisfactory abutment crown on tooth No. 18, fabricating individual implant crowns on implants Nos. 19, 20 and 21, and making a post-core and crown for endodontically treated tooth No. 22. Any complications would only concern a single tooth unit, rather than a complex fixed partial denture.

Figures 3a and b. Implants replace the mandibular posterior teeth providing posterior fixed support for the vertical dimension of occlusion.

Figures 4a and b. Although not the scenario in this patient’s treatment, posterior implants replacing the molars could be augmented with additional anterior implants after the removal of the anterior teeth, creating a full-arch fixed implant restoration.