Implant-Assisted Unilateral Removable Partial Dentures

Transcription

1 Volume 33 No. 1 Page 106 Implant-Assisted Unilateral Removable Partial Dentures Authored by John F. Carpenter, DMD Upon successful completion of this CE activity 2 CE credit hours will be awarded Opinions expressed by CE authors are their own and may not reflect those of Dentistry Today. Mention of specific product names does not infer endorsement by Dentistry Today. Information contained in CE articles and courses is not a substitute for sound clinical judgment and accepted standards of care. Participants are urged to contact their state dental boards for continuing education requirements.

2 Implant-Assisted Unilateral Removable Partial Dentures Effective Date: 1/1/2014 Expiration Date: 1/1/2017 ABOUT THE AUTHOR Dr. Carpenter is a full-time practicing clinician in New Windsor, NY, emphasizing implant and complex restorative dentistry. He is an at ten ding in the department of dental medicine at West chester Medical Center in Valhalla, NY, where he works with the dental residents helping them plan and execute all phases of dentistry. Dr. Carpenter is a Fellow and a Master in the AGD, and a Diplomate in the International Congress of Oral Implantologists. He is a member of nu merous dental associations and serves as a manuscript reviewer for General Dentistry, AGD s bimonthly journal. Dr. Car penter is active in the Ninth District Dental Association, a component of the New York State and ADA, where he has served as education chairman for 2 terms. In addition, Dr. Carpenter has lectured as well as published articles for several professional journals on implants and other subjects. He can be reached at [email protected]. Disclosure: Dr. Carpenter reports no disclosures. INTRODUCTION A unilateral edentulous space (Ken nedy Classifications II and III), in my opinion, is one of the most difficult situations to restore with a removable partial denture (RPD). The traditional RPD design to solve this unilateral space is actually bilateral (Figure 1); rests and clasps placed opposite the edentulous side are necessary, and a major connector is used to connect the 2 sides. In the maxilla, the major connector will contact and cross the palate and in the mandible, cross behind the lower anterior teeth. While these designs offer good support, stability, and retention (the 3 keys to removable partial denture design), many of my patients have been less than happy. The negatives of such a traditional partial include bulkiness, palatal coverage, Figure 1. Traditional unilateral Kennedy Class III partial. A major connector is utilized to connect both sides of the arch. Patients often complain of its bulkiness. speech issues, metal clasps that show, and movement (instability). Patients often ask: If I m only missing teeth on my left, why does the partial need to go over to my right side? This article will review alternatives to the traditional bilateral RPD. Three cases will be presented that describe unilateral implant-assisted RPD (IARPD) solutions. ALTERNATIVE OPTIONS TO THE TRADITIONAL BILATERAL METAL REMOVABLE PARTIAL DENTURE Fixed Implant Prosthesis Option Restoration of unilateral missing posterior teeth with a fixed implant-supported prosthesis is the most current ideal option (Fig ures 2 to 4). The advantages of a fixed im plant restoration are numerous with pa tients often perceiving them as actual body parts. However, possible contraindications in clude anatomical challenges, such as proximity to vital structures and lack of bone. While many of these challenges can be overcome, not all patients are willing to undergo the ad ditional surgeries and the time necessary to grow bone. Other disadvantages include fi nancial limitations and bioengineering challenges, such as excess interocclusal space. Metal Nesbit Unilateral Removable Partial Denture The Nesbit partial is another option. This small, removable prosthesis is used to re place one to 3 teeth on one side of the arch. Historically, this has been used only for a Kennedy Class III edentulous arch (a unilateral posterior space with anterior and pos terior teeth) (Figure 5). The traditional Nes bit RPD has metal rest seats and clasps that fit around the teeth on each side of the space. 1

3 Figures 2 to 4. A posterior fixed-implant restoration. Note the excellent bone width. No bone grafting was necessary to complete this restoration. Patients may feel this has the benefit of being singlesided and less bulky. Unfor tunately, a serious risk of aspiration and swallowing exists due to its small size and limited retention (Figure 6). This danger can produce laceration, infection, and re quires hospitalization and surgical intervention. 1-3 Flexible Nesbit Unilateral Removable Partial Denture This is very similar to the metal Nesbit, ex cept new flexible nylon materials are used (Figure 7). Several material choices exist (such as Valplast, Flexite, and TCS). The esthetics are improved, but unfortunately, this is essentially a tissue-borne prosthesis. The nylon flexible RPD lacks important elements of the traditional RPD; namely, occlusal rests and a rigid framework. Biomechanically, both the metal and flexible unilateral Nesbits are flawed. The supposed benefit of being singlesided (no bilateral support) creates an unstable prosthesis. This design does not allow for a broad distribution of force like the traditional bilateral design that includes indirect retainers and palatal coverage, etc. Nesbits are subject to forces during function, resulting in a rocking buccal-lingual motion. 4,5 This creates excessive pressure on the abutment teeth. The flexible Nesbit also has the added disadvantage of excessive tissue pressure, causing accelerated bone loss of the edentulous ridge. While the Nesbit unilateral RPD ad dresses the patient s desire for a smaller and economical tooth replacement, I have been reluctant to recommend it. Its inherent mechanical shortcomings and possible catastrophic risk of swallowing have precluded its use in my practice until recently. A simple modification was all that was necessary to create an enhanced Nesbit RPD. By ad ding an implant to this original traditional Nesbit design, a more stable, sup - ported, and retentive prosthesis is obtained. The danger of accidental dis lodgement has been minimized and the unfavorable forces on the abutment teeth and the edentulous ridge have been eliminated. CASE REPORTS The following cases will describe unique ways implants can be used to improve the safety and function of a unilateral RPD. For the sake of brevity, please understand that each of these patients underwent a complete evaluation including dental history, complete radiographs, and oral exam. I feel passionate that each patient s treatment diagnosis is unique and treatment should only be selected after a great deal of time listening and getting to know our patients. While these 3 pa tients selected a unilateral IARPD option, others with similar problems se lected a traditional bilateral partial and others selected a fixed-implant prosthesis. Case No. 1 A 68-year-old male patient presented with discomfort to chewing, upper left. An examination disclosed a failing posterior abutment of a 4-unit fixed bridge (Figure 8). The bridge was sectioned and No. 15 was extracted atraumatically with concurrent socket bone grafting. Treatment options were discussed and included: (1) implant-supported fixed bridge for Nos. 13, 14, and 15 (sinus grafting would be necessary); (2) bilateral conventional metal RPD; and (3) unilateral IARPD. 2

4 Figure 5. A metal Nesbit partial. Traditional metal clasps and rests fit the adjacent abutment teeth. Figure 6. A radiograph of a swallowed unilateral Nesbit partial requiring surgical intervention. Figure 7. A nylon flexible Nesbit partial. This offers improved esthetics but is tissue-borne and will lead to accelerated ridge destruction. Figure 8. Panoramic radiograph of patient No. 1. The maxillary upper left posterior bridge is failing. Figure 9. Processing of a Micro ERA attachment (Sterngold). Figure 10. Radiograph demonstrating an anterior ERA attachment and posterior implant locator attachment. Note the small island of bone that allowed the implant to be placed without bone augmentation. Figures 11 and 12. Intaglio and intraoral views of implant-assisted removable partial dentures (IARPD). The patient selected option No. 3. His selection was based on the avoidance of additional surgery (lateral wall sinus augmentation). He also declined option No. 2 due to the fact that it would cross his palate. A single crown was required for tooth No. 13, since the bridge was sectioned and the old abutment fit was poor. It was decided to use a precision extracoronal attachment (Micro ERA [Sterngold]) to increase retention of the RPD, and improve esthetics since the buccal clasp on No. 13 would not be needed (Figure 9). An implant (Legacy [Implant Di rect]) was placed in the small island of bone distally and allowed to heal for 3 months before beginning construction of the prosthesis. Figures 10 to 12 de monstrate the fabrication of the IARPD. 3

5 Figure 13. Salvage case. Attempts at a fixed-implant prosthesis had failed. Note how tooth No. 26 is periodontally compromised and represents a poor quality abutment. Figure 14. Radiograph of the sole posterior implant to be utilized to improve the retention, stability, and support of a small Nesbit partial. Figure 15. A LOCATOR abutment (ZEST Anchors). These abutments are available in different heights for each implant platform. IARPDs are a space-sensitive prosthesis so the correct height must be selected. Figure 16. A blue male is being snapped into the metal housing with the special locator tool. Figures 17 and 18. Final unilateral IARPD with a flexible pink clasp. This was incorporated into the design to help overcome the patient s esthetic concerns. The partial was inserted without the locator attachment to allow soft-tissue settling. The next day, a LOCATOR abutment (ZEST An chors) was torqued into the implant and the metal housing processed into the in taglio side of the partial. Case No. 1 Highlights 1. Most extracoronal at tachments used to support a precision RPD require 2 splinted crown abutments to prevent excess force on the teeth. The posterior implant with locator at tachment eliminated the need for a second crown on No Please note that No. 12 does have a definitive rest seat and lingual bracing arm. This is traditional RPD design and will limit harmful lateral and vertical movement in function (Figure 12). 3. Esthetics was addressed since no buccal clasp will show in a broad smile. 4. The patient s desire to avoid complicated, timeconsuming sinus surgery with its associated morbidity was complied with. 5. Implant placement in these type of cases is simple: location is less demanding than with fixed restorations and there is no need for large/long implants. The IARPD de sign allows for a combination of tissue and implant support, hence the forces are much less on the implant. Case No. 2 This case is what I call a salvage case. A 50-year-old female who was formerly treated by a periodontist presented to our office for a second opinion. Two implants had been placed in the lower right quadrant and a fixed implant-supported prosthesis was planned. How ever, the implant in the No. 27 position had failed 2 times and the patient refused another implant surgery (Fig ures 13 and 14). The posterior implant (Bio met 3i) had osseointegrated. Complications to treatment in cluded: she was angry 4

6 with her former periodontist; tooth No. 26 was very weak periodontally and had a +2 mobility; she did not want any metal to show; and her finances were limited. She requested a fixed bridge from Nos. 26 to 29. I explained that tooth No. 26 was too weak to be used as a fixed-bridge abutment, and that connecting natural teeth to implants is not without complications. After much deliberation, it was decided to fabricate a unilateral IARPD by placing a locator attachment on the osseointegrated implant (Figure 15). This would help provide stability, support, and retention for a unilateral partial. A metal framework was used with a mesial-occlusal rest seat, guide plane, and circumferential clasp on No. 30. Anteriorly, No. 26 re ceived a metal lingual apron for bracing and a flexible pink buccal retentive arm (Figures 16 to 18). This case was definitely a compromise, but resulted in a happy patient. Case No. 2 Highlights 1. Problem solving patient s expectations (a fixed bridge was not appropriate in this situation). 2. Adding a flexible pink clasp eased the patient s esthetic concerns, but a lingual bracing arm helped with the stability of a weak tooth (Figure 18). 3. This treatment was very cost-effective, a major concern of this patient. Case No. 3 This 55-year-old male had been a patient for some time. At each recall, I would see an extremely long fixed bridge (Nos. 17 to 23) that was failing (Figure 19). The posterior abutment was loose and recurrent decay was developing. Never really having a good solution to his looming problem, I dreaded the day when treatment would become necessary. My initial thoughts regarding treatment options included: (1) a new fixed bridge (an option with which I was uncomfortable); (2) two new anterior crowns and a bilateral RPD (where to place the rests and clasps on the opposite side concerned me); and (3) a fixed implant-supported bridge for Nos. 18 to 21 and separate anterior crowns Nos. 22 and 23. (Concerns included proximity to the mandibular nerve, excessive interarch space [Figure 20], the unpredictability and cost of vertical bone augmentation.) Figure 19. Preoperative radiographic view of a failing long-span fixed bridge. Figure 20. Bone resorption and resulting excessive interarch space. Figure 21. An implant was placed after the socket grafting healed. Note the lack of bone vertical height anterior to the site. This site was the only area where adequate height and width could be obtained for implant placement without bone augmentation. Figure 22. Doubleabutted crowns (Nos. 22 and 23) with an ERA extracoronal attachment (Sterngold). This was necessary in this situation to resist lateral movement of the IARPD. The unilateral IARPD gave me an option with which I felt comfortable. The patient agreed, so the failing fixed bridge was sectioned and tooth No. 17 was extracted with 5

7 concurrent bone grafting. Three months later, an implant was placed at site No. 17, utilizing single-stage surgery (Figure 21). The prosthesis construction was begun 4 months later and went smoothly. An extra coronal ERA attachment was utilized for its retention, esthetics, and stress-breaking features. After insertion and one day of tissue settling, a locator attachment was utilized for the distal im plant abutment (Figures 22 to 24). An esthetic and functional prosthesis was created, resulting in a satisfied patient. Continuing Education Figures 23 and 24. Postoperative photos. A locator abutment was torqued into the posterior implant and an ERA and LOCATOR attachment were processed, creating a secure prosthesis. Case No. 3 Highlights 1. Optimal esthetics were achieved with no display of metal; however, still note the lingual plate providing stability behind the double-abutted anterior abutments (Figure 23). 2. Splinted double anterior abutments were utilized in this case since both teeth needed new crowns and because the long edentulous space justified the splinting to resist movement of the RPD during function (Figure 22). 3. Selection of the best implant site: Site No. 17 was chosen because of its residual height and width. Teeth Nos. 18 to 21 had been missing for 20+ years and resorption made these sites a poor choice (Figures 21 and 22). 4. The large interocclusal space makes this case a classic indication for a RPD and not a fixed-implant prosthesis (Figure 20). The crown height space is excessive. A fixed-implant prosthesis would create a vertical cantilever magnifying stress to the prosthesis and implants. DISCUSSION Each of these patients could have pursued a fixed-implant reconstruction, yet each declined this option. It has been my experience when discussing the option of fixed-implant restorations requiring extensive bone grafting that the patient often selects an alternative treatment option. Pa - tients often choose the less challenging removable option. Many reasons exist, including: (1) financial limitations; (2) patients are often emotionally unable to commit to the additional bone augmentation surgery with associated morbidity; and (3) the time commitment of more Figure 25. A diagram demonstrating the damaging leverage forces a RPD can transmit to the abutment teeth. Figure 26. By adding an implant, an IARPD is created. This design helps neutralize the damaging forces to the abutment teeth and increases retention, support, and stability. Damaging forces to the ridge by the RPD are also mitigated; hence, bone is preserved. complicated cases. The use of RPD enhanced by the addition of implants has been a major growth area of my practice. Demo graphic studies show an increase in the number of baby boomers who have maintained many of their own teeth. 6-8 Years ago, this age group was often fully edentulous but is now partially edentulous. Many of the problems with conventional RPDs can be overcome with the placement of one or more strategically positioned implants. En hanced RPDs have been described in the literature under the following names: IARPD, 9 implant- 6

8 Table. Advantages of Implant-Assisted Removable Partial Dentures l Improved comfort and confidence l Patients who formerly were unable to wear conventional removable partial dentures (RPD) are often able to wear an implant-assisted RPD l Enhanced retention, support, and stability l Improved esthetics if clasps can be eliminated l Preservation of bone l Better distribution of forces and elimination of damaging leverage to natural abutment teeth l Psychological advantage to patient of preserving compromised natural teeth that are not suitable to use as abutments to support a RPD l An increase in chewing force l A contingency plan where implant placement may be staged and this prosthesis can be used as an interim option retained par tial overdentures, 10 and implant-supported re movable partial dentures. 11 There are many advantages to IARPD versus conventional RPD 12 (Table). Figures 25 and 26 help demonstrate how the placement of an im plant neutralizes the unfavorable torqueing forces which RPDs place on abutment teeth. CLOSING COMMENTS While simple in theory, IARPD treatment requires a comprehensive un derstanding of implant therapy and mastery of removable prosthodontic fundamentals. As with all dental treatment, a complete diagnosis must first be completed. Special considerations include evaluation of atypical anatomy, and measuring intra- and interarch spaces. A good understanding of RPD design concepts is a prerequisite for successful treatment. This article demonstrates a different use of the IARPD concept. The unilateral posterior edentulous space is one of the most difficult situations to treat with a RPD. By placing one strategic implant, each of these pa tients was able to receive a unilateral Nesbit IARPD. The destructive forces associated with a unilateral partial were eliminated. Secure retention was also obtained reducing the risk of swallowing and allowing for a smaller, less bulky, RPD design. REFERENCES 1. Toshima T, Morita M, Sadanaga N, et al. Surgical removal of a denture with sharp clasps impacted in the cervicothoracic esophagus: report of three cases. Surg Today. 2011;41: Brunello DL, Mandikos MN. A denture swallowed. Case report. Aust Dent J. 1995;40: Gallas M, Blanco M, Martinez-Ares D, et al. Un noticed swallowing of a unilateral removable partial denture. Gerodontology. 2012;29:e1198-e Schneid T, Mattie P. Mechanical principles associated with removable partial dentures. In: Phoenix RD, Cagna DR, DeFreest CF. Stewart s Clinical Removable Partial Prosthodontics. 4th ed. Hanover Park, IL: Quintessence Publishing; 2008: Preiskel HW. Distal extention prosthesis. In: Precision Attachments in Prosthodontics: The Application of Intracoronal and Extracoronal Attachments, Volume 1. Hanover Park, IL: Quintessence Publishing; 1984: Douglass CW, Shih A, Ostry L. Will there be a need for complete dentures in the United States in 2020? J Prosthet Dent. 2002;87: Douglass CW, Watson AJ. Future needs for fixed and removable partial dentures in the United States. J Prosthet Dent. 2002;87: Wöstmann B, Budtz-Jørgensen E, Jepson N, et al. Indications for removable partial dentures: a literature review. Int J Prosthodont. 2005;18: Schneid T, Mattie P. Implant-assisted removable partial dentures. In: Phoenix RD, Cagna DR, DeFreest CF. Stewart s Clinical Removable Partial Prosthodontics. 4th ed. Hanover Park, IL: Quintessence Publishing; 2008: Chikunov I, Doan P, Vahidi F. Implant-retained partial overdenture with resilient attachments. J Prosthodont. 2008;17: Ohkubo C, Kobayashi M, Suzuki Y, et al. Effect of implant support on distal-extension removable partial dentures: in vivo assessment. Int J Oral Maxillofac Implants. 2008;23: Carpenter J. The retrofit of an existing removable partial denture with implants: a case report. Implant Practice US. 2010;3:

9 POST EXAMINATION INFORMATION To receive continuing education credit for participation in this educational activity you must complete the program post examination and answer 6 out of 8 questions correctly. Traditional Completion Option: You may fax or mail your answers with payment to Dentistry Today (see Traditional Completion Information on following page). All information requested must be provided in order to process the program for credit. Be sure to complete your Payment, Personal Certification Information, Answers, and Evaluation forms. Your exam will be graded within 72 hours of receipt. Upon successful completion of the postexam (answer 6 out of 8 questions correctly), a letter of completion will be mailed to the address provided. Online Completion Option: Use this page to review the questions and mark your answers. Return to dentalcetoday.com and sign in. If you have not previously purchased the program, select it from the Online Courses listing and complete the online purchase process. Once purchased the program will be added to your User History page where a Take Exam link will be provided directly across from the program title. Select the Take Exam link, complete all the program questions and Submit your answers. An immediate grade report will be provided. Upon receiving a passing grade, complete the online evaluation form. Upon submitting the form, your Letter of Completion will be provided immediately for printing. General Program Information: Online users may log in to dentalcetoday.com any time in the future to access previously purchased programs and view or print letters of completion and results. This CE activity was not developed in accordance with AGD PACE or ADA CERP standards. CEUs for this activity will not be accepted by the AGD for MAGD/FAGD credit. POST EXAMINATION QUESTIONS 1. In the author s opinion, restoration of unilateral missing posterior teeth with a fixed implantsupported prosthesis is the most current ideal option. 2. The Nesbit partial is another option. This small, removable prosthesis is used to replace 3 to 4 on one side of the arch. 3. Biomechanically, both the metal and flexible unilateral Nesbits are flawed. 4. The flexible Nesbit does not cause excessive tissue pressure that normally would result in accelerated bone loss of the edentulous ridge. 5. Most extra coronal attachments used to support a precision removable partial denture (RPD) require 2 splinted crown abutments to prevent excess force on the teeth. 6. The implant-assisted removable partial dentures (IARPD) design allows for a combination of tissue and implant support, hence the forces are much less on the implant. 7. Demographic studies show an increase in the number of baby boomers who have maintained many of their own teeth. 8. Enhanced RPDs have been described in the literature under the following names: IARPD. In the closing comments, the author clearly states that a good understanding of RPD design concepts is not required for successful treatment. 8

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