Removable
Implant-Retained Removable Prosthetic Designs for Patients With Maxillary Posterior Edentulism
Steven J. Sadowsky, DDS
Steven J. Sadowsky, DDS, maintains a full-time prosthodontic
practice in Poulsbo, Wash. He is an associate clinical professor at the
University of Southern California School of Dentistry.
Copyright 2003 Journal of the California Dental Association.
When a patient has lost the maxillary posterior teeth, as patient "A.K."
had, the problem has conventionally been resolved with a tooth-tissue
supported removable partial denture. However, successful function with
the prosthesis depends on the design of the remaining anterior teeth and
their ability to provide anterior guidance.1 Generally, this
can be achieved in the periodontal disease-resistant patient. Properly
designed2 and maintained RPDs can provide long-term clinical
service without detrimental effects on the periodontium, provided that
preprosthetic periodontal health has been established.3 However,
when the maxillary anterior sextant is periodontally compromised, treatment
planning may be more complex.
With moderate anterior bone loss, the use of a fixed splint and a distal extension RPD, with or without attachments, has been successful.4 With the advent of a predictable endosseous implant system, placing posterior implants to support fixed partial dentures may be the treatment of choice. However, in the clinical scenario where there is a lack of alveolar bone height and/or width inferior to the maxillary antrum, sinus bone augmentation5 or onlay grafting6 may be essential for successful integration. Removable implant prostheses offer an alternative for patients who may have sinus complications, contraindications for extensive surgery, or time or financial limitations.
The bilateral placement of implants in the maxillary first premolar position as overdenture abutments for a distal extension RPD can provide auxiliary support and retention. Implant-retained attachments can eliminate direct retainers on the cuspids. Simplifying the framework design has been shown to reduce the periodontal indices on the cuspids,7 and may improve the survival rate of RPDs at 50 percent over 10 years.8 An additional implant placement in the molar region bilaterally can provide greater occlusal and extension base stability. With either single-anchor attachments or bar-retained clips, an RPD overdenture with four posterior implants would mimic a posterior tooth-supported prosthesis.
With advanced bone loss in the anterior dentulous zone, accepted treatment plans would involve either an anterior fixed implant-supported splint with a posterior RPD9 or a bar-retained overdenture.10 In either case, a minimum of four implants is recommended. 11 The combination fixed and removable prosthetic design can also be fabricated with intracoronal or extracoronal attachments installed in the distal surfaces of the terminal abutments. The bar-retained overdenture can be designed with a round bar (Figure 1) or a milled bar (Figure 2), which offers the benefits of a fixed and removable prosthesis (Figure 3).12,13
Success rates of maxillary implant overdentures do not appear as high as mandibular implant overdentures.14 Inferior bone quality, adverse loading conditions, unfavorable crown-to-implant ratios and poor patient selection have been underscored as risk factors.15 Therefore, the following guidelines have been recommended: The implant length should be greater than or equal to 10 mm with an even distribution between first premolars.10 A standard diameter of 4.1 mm is suggested. Implants of a reduced diameter should be combined with a standard diameter.10 Alcoholics, drug abusers, bruxers, depressed patients, and heavy smokers (more than 10 cigarettes per day) should be excluded.16 When these criteria have been observed, cumulative survival rates of 90 percent over five years have been documented.17,18 A number of authors have reported higher incidence of complications with removable implant prostheses compared to fixed.19,20
However, Zitzmann and Marinello21 found no significant difference between fixed and removable implant reconstructions in the time until retreatment, a measure that may represent best the outcome of prosthetic success.
The use of solitary retentive anchors for the substructure design of the removable implant prosthesis on the maxillae remains controversial. A bar connection may offer cross support for varying bone densities found in the maxillae. However, studies have not been conclusive as to superiority of the bar compared to ball attachments.22
The milled-bar-retained removable prosthesis, often referred to as a spark erosion prosthesis, has a number of advantages.23 The interimplant distance does not depend upon on retaining clip space. Nonparallel implant alignment can be more easily reconciled with the mesostructure. The rigid-bar construction may thwart bending moments that may impact more flexible bar designs.24 The metal superstructure retards fracture with minimal bulk and extension onto the palatal region. The attachments offer retention security and allow removal for hygiene (Figure 4). Only an 8 to 10 mm interarch distance is required25 as opposed to 11-13 mm for the conventional overdenture design.26 The disadvantages of this design are technique-sensitivity and increased cost. Alternative milled-bar designs with reduced costs have been reported.27,28 No longitudinal studies have been published on the success rate of the maxillary milled-bar design.
The removable implant overdenture design may be the first-choice treatment for patients also considering a fixed implant alternative. In fact, it has been shown that this design on the maxillae can be accepted as an equally good treatment modality when patients’ assessments are evaluated.29 Differential treatment planning for a fixed or removable implant prosthesis for patient A.K. or others include decisions regarding number and position of implants and type of prosthesis. A pyramid of objective and subjective factors (Figure 5) can be helpful to consider. Complete denture principles dictate lip support, dental-gingival esthetic needs, space allowance, and phonetic requirements.31 Limited bone quality and quantity may preclude a fixed restoration.32 Off-ridge relations may favor a removable prosthesis. When a patient is a bruxer, posterior implants may help to stabilize the increased forces.33 Subjective factors include patients’ expectations about retention, timeline of treatment, hygiene access, and cost.
In conclusion, the increasing emphasis on evidence-based dentistry during the past 25 years has buttressed dentists’ ability to predict treatment success over the long term. Decisions regarding fixed or removable designs, conventional or implant retained prosthesis, or having treatment at all have become more deliberate.
References
1. Starr NL, The distal extension case: An alternative restorative design for implant prosthetics. Int J Periodontics Restorative Dent 21:61-7, 2001.
2. Owall B, Budtz-Jörgensen E, et al, Removable partial denture design: A need to focus on hygienic principles? Int J Prosthodont 15:371-78, 2002.
3. Petridis H, Hempton TJ, Periodontal considerations in removable partial denture treatment: A review of literature. Int J Prosthodont 14:164-72, 2001.
4. Hindels GW, Load distribution in extension saddle partial dentures. J Prosthet Dent 2:92-100, 1952.
5. Keller EE, Tolman DE, Eckert SE, Maxillary antral-nasal inlay antogenous bone graft reconstruction of a compromised maxilla: A 12-year retrospective study. Int J Oral Maxillofac Implants 14:707-21, 1999.
6. Keller EE, Tolman DE, Eckert SE, Surgical prosthetic reconstruction of advanced maxillary bone compromised with autogenous onlay block bone grafts and osseointegrated endosseous implants: A 12-year study of 32 consecutive patients. Int J Oral Maxillofac Implants 14:197-209, 1999.
7. Zlaterić DK, Celebic A, Valentic-Peruzivic M, The effect of removable partial dentures on periodontal health of abutment teeth and non-abutment teeth. J Periodontal 73:137-44, 2002.
8. Vermeulen AHBM, Keltjens HMAM, et al, Ten-year evaluation of removable partial dentures: Survival rates based on retreatment, not wearing and replacement. J Prosthet Dent 76:267-72, 1996.
9. Pellecchia M, Pellecchia R, Emtiaz S, Distal extension mandibular removable partial denture connected to anterior fixed implant supported prosthesis. A clinical report. J Prosthet Dent 83:607-12, 2000.
10. Mericske-Stern R., Taylor TD, Belser U, Management of the edentulous patient. Clin Oral Impl Res 11(Suppl):108-25, 2000.
11. Lewis S, Sharma A, Nishimura R, Treatment of edentulous maxillae with osseointegrated implants. J Prosthet Dent 68:503-8, 1992.
12. Van Roekel NB, The fixed-removable implant prosthesis. A practical alternative. Quintessence Dent Tech 49-61, 1995.
13. Tipton PA, The milled bar-retained removable implant-supported prosthesis: a treatment alternative for the edentulous maxilla. J Esthet Restor Dent 14(4):208-16, 2002.
14. Jemt T, Chai J, et al, A 5-year prospective multicenter follow-up report on overdentures supported by osseointegrated implants. Int J Oral Maxillofac Implants 11:291-8, 1996.
15. Jemt T, Lekholm U, Implant treatment in edentulous maxillae: A 5 year follow-up report on patients with different degrees of jaw resorption. Int J Oral Maxillofac Implants 10:303-11, 1995.
16. Ekfeldt A, Christiansson U, et al, A retrospective analysis of factors associated with multiple implant failures in maxillae. Clin Oral Implants Res 12(5):462-7, 2001.
17. Narhi TO, Hevinga M, et al, Maxillary overdentures retained by splinted and unsplinted implants: A retrospective study. Int J Oral Maxillofac Implants 16:259-66, 2001.
18. Mericske-Stern R, Oelterli M, et al, A follow-up study of maxillary implants supporting an overdenture: Clinical and radiographic results. Int J Oral Maxillofac Implants 17:678-86, 2002.
19. Naert I, Gizani S, van Steenberghe D, Rigidly splinted implants in the resorbed maxilla to retain a hinging overdenture: A series of clinical reports for up to 4 years. J Prosthet Dent 79:156-64, 1998.
20. Jemt T, Book K, et al, Failures and complications in 92 consecutively inserted overdentures supported be Brånemark implants in severely resorbed edentulous maxillae: A study from prosthetic treatment to first annual check-up. Int J Oral Maxillofac Implants 7:162-7, 1992.
21. Zitzmann NU, Marinello CP, Treatment outcomes of fixed or removable implant-supported prostheses in the edentulous maxilla. Part II: Clinical findings. J Prosthet Dent 83:424-33, 2000.
22. Bergendal T, Enquist B, Implant-supported overdentures. A longitudinal prospective study. Int J Oral Maxillofac Implants 13:253-62, 1998.
23. Salinas TS, Finger IM, et al, Spark erosion implant-supported overdentures: Clinical and laboratory techniques. Implant Dent 1:246-51, 1992.
24. Jemt T, Carlsson L, et al, In vivo load measurements on osseointegrated implants supporting fixed or removable prosthesis: a comparative pilot study. Int J Oral Maxillofac Implants 6:413-7, 1991.
25. Clark S, Combination fixed/removable implant prosthesis using spark erosion technology. Implant Society 2:15-16, 1991.
26. Abu Jamra NF, Stavridakis MM, Miller RB, Evaluation of interarch space for implant restorations in edentulous patients: A laboratory technique. J Prosthodont 9:102-6, 2000.
27. Brudvik JS, Chigurupatik, The milled implant bar: an alternative to spark erosion. J Can Dent Assoc 68(8):485-8, 2002.
28. Davodi A, Nishimura R, Beumer J, An implant-supported fixed-removable prosthesis with a milled tissue bar and Hader clip retention as a restorative option for the edentulous maxilla. J Prosthet Dent 78:212-17, 1997.
29. Zitzmann NU, Marinello CP, Treatment outcomes if fixed or removable implant-supported prostheses in the edentulous maxilla. Part I: Patients’ assessments. J Prosthet Dent 83:424-33, 2000.
30. Niswonger ME, Rest position of mandible and centric relation. J Am Dent Assoc 21:1572-82, 1934.
31. Pound E, Esthetic dentures and their phonetic values. J Prosthet Dent 1:98-111, 1951.
32. Davis DM, The role of implants in the treatment of edentulous patients. Int J Prosthodont 3:42-50, 1990.
33. Rangert B, Jemt T, Jorneus L, Forces and moments on Brånemark implants. Int J Oral Maxillofac Implants 4:241-7, 1989.
To request a printed copy of this article, please contact: Steven J. Sadowsky, DDS, 15415 Harvey Road, NE, Bainbridge Island, WA 98110-1052.
Legends
Figure 1. Intaglio view of overdenture superstructure.
Figure 2. Maxillary implant bar overdenture framework.
Figure 3. Maxillary implant milled-bar framework.
Figure 4. Superstructure for milled-bar framework (note retention latches on palatal aspect).
Figure 5. Pyramid of factors to be considered for successful treatment planning.
