The use of a dental implant as an abutment in three unit implant-tooth supported fixed partial denture: a case report and 32 month follow-up

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1 CASE REPORT Australian Dental Journal 2006;51:(3): The use of a dental implant as an abutment in three unit implant-tooth supported fixed partial denture: a case report and 32 month follow-up DF Clarke,* ST Chen, AJG Dickinson Abstract The combined use of dental implants and teeth as abutments in fixed partial dentures may offer advantages to both patients and practitioners in certain clinical situations. An implant-tooth retained prosthesis may reduce surgical intervention and cost to the patient. It may also mean that anatomical restrictions to the provision of an implant-retained fixed prosthesis may be overcome. In this case report, the steps in provision of a three unit implantto-tooth fixed partial denture are described and the treatment planning and prognosis of a restoration of this type are discussed. Key words: Implant, implant dentistry, implant-tooth fixed partial denture, fixed partial denture. Abbreviations and acronyms: I-I FPD = implant-supported fixed partial denture; I-T FPD = implant-tooth supported fixed partial denture. (Accepted for publication 18 May 2006.) INTRODUCTION Implant-supported fixed partial dentures (I-I FPDs) have been shown to be a predictable treatment modality. 1 However, in clinical practice, especially in the posterior regions of the mandible and maxilla, this restoration may not be possible due to inadequate bone volume. Bone resorption and the presence of anatomical structures such as the inferior alveolar canal and the maxillary sinus may mean that implant placement is contra-indicated or is only possible with supplementary procedures such as bone grafts, or transposition of the contents of the inferior alveolar canal. The ability to use a tooth in combination with an implant to support a fixed partial denture (I-T FPD) can obviate the need for such supplementary procedures. The combined use of teeth and dental implants as abutments for fixed prostheses is a subject of some *Private practice, Ivanhoe East, Victoria. Private practice, Balwyn, Victoria. Private practice, Glen Iris, Victoria. controversy in dentistry. The advantages include the restriction of the surgical intervention and ability to provide the patient with the prosthesis at a lower cost. However, dental implants are attached directly to the alveolar bone by means of a functional ankylosis (osseointegration), whereas the periodontal ligament affords some movement of the tooth in the alveolar socket. Renouard and Rangert 2 discussed the potential for differential movement and the possibility of a cantilever loading effect on the tooth. In order to minimize this effect, stress-breaking connectors have been used in these prostheses. However, this has been associated with a greater incidence of tooth intrusion. 3-5 Fixed partial dentures with rigid connectors have been reported not to be associated with this phenomenon. 3-6 Bragger et al. 6 reported on the biological and technical complications and failures of I-T FPDs over four to five years of function. These data indicated that loss of FPDs occurred at a similar rate with I-T, I-I or tooth-supported reconstructions. It can be concluded from the study that several factors are likely to be associated with increased likelihood of a successful outcome. These include the requirement that the abutment tooth should be healthy and periodontally sound, the FPD should be limited to three units with no cantilever extensions, only one implant and one tooth to support the prosthesis with the pontic being placed between the two abutment restorations, construction of a rigid onepiece framework and the absence of bruxism. This case report describes the restoration of a partially dentate maxillary right posterior sextant using a second molar and a single implant to support an I-T FPD. CASE REPORT A healthy 46-year-old female non-smoker presented with the request to replace the missing tooth 16 for aesthetic and functional reasons. The patient had maintained regular dental attendance with minimal restorative treatment necessary over the past 12 years. Since January 1996, the patient has been under the care of a specialist periodontist for supportive and Australian Dental Journal 2006;51:3. 263

2 Fig 1. Pre-operative periapical radiograph showing crestal bone loss associated with periodontitis on tooth 14. maintenance care and maintained a stable and healthy periodontal state. However, the single remaining premolar (tooth 14) and tooth 16 did not respond to treatment and in 1998 tooth 16 was extracted due to advanced chronic periodontitis. At the time of consultation for consideration of the restoration of the 16 edentulous site, an 8mm pocket was present on the distal aspect of tooth 14. The tooth responded normally to pulp sensibility testing. A periapical radiograph revealed that bone loss extended to the apex of this tooth (Fig 1). The teeth were in a Class I dental relationship with adequate intercuspation in posterior sextants. Group function existed in lateral excursions and no interferences occurred during protrusion. There was no evidence of parafunctional attrition. Full mouth periodontal probing revealed that, other than associated with tooth 14, there were no probing depths over 3mm and no sites with bleeding on probing. The prognosis of tooth 14 was considered hopeless for the periodontal reasons stated above. The remaining second molar tooth (17) had a moderate amalgam restoration and pocketing of less than 3mm with no bleeding on probing. The tooth exhibited a zero mobility rating and for these reasons considered acceptable for use as an abutment tooth for a fixed partial denture. The decision was made to extract tooth 14. Several treatment options were considered in light of the patient s preference to avoid a removable partial denture: (1) A tooth-supported fixed partial denture was considered unsuitable due to the long edentulous span and the biologic cost to tooth preparation of the minimally restored tooth 13; (2) A bone graft to the maxillary sinus floor, followed by placement of two implants and restoration with implant-retained crowns; (3) Implant placement in the 14 site and fabrication of a three unit I-T FPD. Following discussion of the advantages and disadvantages, and prognostic implications of each option, the patient agreed to the third option, being the implant-tooth fixed partial denture. Fig 2. Intra-oral view of socket immediately after tooth extraction. Appropriate pre-operative radiographs were taken (OPG, periapical radiographs and axial tomograms). Extraction of tooth 14 was undertaken four weeks prior to implant placement under local anaesthesia (Xylocaine 2%, 1: adrenaline. Astra Pharmaceuticals, Sydney, Australia). Care was taken to minimize trauma to the surrounding hard and soft tissues by the use of periotomes and luxators to remove the tooth (Fig 2). Postoperative healing was uneventful. Implant placement was undertaken using the same local anaesthetic. The patient rinsed with a chlorhexidine-based mouthwash (Savacol Colgate, Baulkham Hills, Australia) for one minute prior to surgery. Oral antibiotics (Amoxycillin 250mg tid) were administered to the patient 24 hours prior to surgery as a prophylactic measure. A crestal incision was made from tooth 13 to tooth 17, with sulcular extensions on the buccal and palatal aspects of tooth 13. Distally, the crestal incision terminated 2mm from tooth 17 with buccal and palatal releasing incisions. Granulation tissue within the healing socket of tooth 14 was separated from the flaps by splitting the crestal incision on the buccal and palatal aspects of the socket. The granulation tissue within the socket was retrieved and later used as a connective tissue graft to enhance the buccal contour of the ridge. Full thickness buccal and palatal mucoperiosteal flaps were raised. Implant placement at the 14 site required several considerations. Firstly, it was necessary to avoid damage to the root of tooth 13 due to its increased axial inclination. The osteotemy site was prepared with a slight distal angulation which provided engagement of the medial wall of the maxillary sinus. In placing the implant, consideration was given to the mesial angulation of tooth 17 to allow for an ideal abutment tooth preparation. Finally, preparation of the implant site was complicated by a discrepancy in bone height mesially and distally. The mesial aspect of the osteotomy site, adjacent to tooth 13 showed maintenance of bone height in comparison to the distal aspect where crestal bone loss had occurred. The implant shoulder was therefore positioned to allow submucosal placement of 264 Australian Dental Journal 2006;51:3.

3 Fig 5. Intra-oral view of sectioned metal coping luted with Duralay at try-in. Fig 3. Periapical radiograph of implant eight weeks after placement. 1mm distally and 3 4mm mesially. During preparation, some mesial bone had to be removed to allow seating of the healing abutment without interference. Due to the available bone and a desire to limit the depth of the placement of the restorative shoulder, an 8mm long, 4.1mm diameter Staumann RN Plus implant with an SLA (sand blasted and acid etched) surface (Straumann, Waldenburg, Switzerland) was chosen. A 3.5mm bevelled healing abutment was attached to the implant and the flaps adapted around the healing abutment and secured with interrupted 5/0 chromic gut sutures (Dynek, South Australia, Australia). Early healing was uneventful and the patient was reviewed two weeks postoperatively. Radiographic evaluation following eight weeks of healing demonstrated an acceptable apparent bone to implant contact (Fig 3). The implant demonstrated no signs of mobility. Preparation of tooth 17 was undertaken after replacement of the amalgam restoration. The design of the preparation was influenced by the fixture angle. During preparation, the impression coping was attached to the fixture to allow visualization of the fixture angle to maximize parallelism (Fig 4). Margins were kept supragingival to aid ease of cleaning. As a result of the submucosal position of the mesial aspect of the implant shoulder, a screw-retained implant impression coping was placed and a vinyl polyvinlysiloxane impression was made incorporating the prepared tooth 17. Following cast fabrication, a SynOcta abutment (2.5mm) was chosen to allow for the fabrication of a gold mesostructure using a prefabricated standard gold collar. The mesostructure provided an ultimate restorative margin 1 1.5mm submucosal on the mesial and buccal aspect. Postsurgical recession on the distal aspect of the implant site provided a supramucosal restorative margin. Prior to finalization of the I-T FPD, a try-in of the metal casting was undertaken (Fig 5). The pontic was sectioned prior to try-in and the two portions secured with self-curing acrylic resin (Duralay, Reliance, Worthington, USA). The restoration was designed to be a one-piece rigid structure of porcelain fused to metal and luted to place. A gold margin was prescribed for the retainer on tooth 17 to allow for reduced tooth preparation and provide a minimal marginal gap dimension. The fixed partial denture was fabricated from a gold framework (Degunorm, Degussa, Postfach, Germany) with hydrothermal veneering ceramic (Duceragold, Degussa, Postfach, Germany). Both retainers were provided with vent-holes to aid cement escape on the palatal surface. After try-in, the restoration was completed and then cemented with resin-modified glass ionomer cement (Fuji Plus, GC Corporation, Tokyo, Japan) and the vent-holes sealed with amalgam alloy Fig 4. Periapical radiograph showing implant with impression coping attached and prepared 17. Fig 6. Intra-oral view of fixed partial denture immediately after insertion. Australian Dental Journal 2006;51:3. 265

4 Fig 7. Periapical radiograph of fixed partial denture, 32 months post-insertion. (Fig 6). The occlusal scheme provided shimstockretaining contact in maximum intercuspation and freedom from interferences in lateral and protrusive excursions. The patient was instructed on the use of Superfloss (Oral B, Sydney, Australia) to allow cleaning under the pontic and advised to attend twice yearly for review and ongoing maintenance. Follow-up at 32 months revealed stable alveolar bone heights around both the tooth and the implant (Fig 7). Soft tissue levels were also stable. Periodontal probing revealed probing depth within normal limits and the absence of bleeding on probing. The patient maintains excellent oral hygiene. DISCUSSION While there are potential cost and technical advantages in using an I-T FPD, differing opinions exist with respect to the outcome. Complications to both the tooth and the dental implant have been reported. These have included implant fracture, 6 tooth intrusion, 3-5 cement bond breakdown, 3,4 abutment tooth fracture, 3,6 peri-implantitis, 5,6 periodontal 3,6 and endodontic complications. 3,6 Bragger et al. 6 reported on biological and technical complications and found no statistical difference between the survival rates of I-I, I-T and tooth supported FPDs when in function for between four to five years. The authors concluded that an I-T FPD when considered should avoid cantilever extensions and be restricted to support using one implant and one tooth; being at either end of the FPD. High success rates have also been noted in a systematic review of a number of studies that had observation periods of at least five years. 4 Lang et al. reviewed scientific publications investigating I-T FPDs and reported a reduced survival rate of I-T FPDs between the five-year and 10-year observation periods. The authors reported that the failure rates of abutment teeth and implants were not significantly different over the five or 10-year period. Their conclusion that neither the tooth nor the implant is responsible for the lower survival rate infers that other factors may be causative. Future papers that include reporting on the quality of mechanical resistance and retention of the preparation of the abutment tooth may also provide valuable information as to expected survival outcomes. Unfortunately, as Lang et al. identified, there was only one randomized control trial over a 10-year observation period that addressed the comparison between I-I FPD and I-T FPD. 7 Thus, the low number of prostheses reported restricts the significance of the conclusions that may be drawn. More studies with larger subject numbers and with data over a 10-year observation period are required. However, some of the complications reported with this type of prosthesis offered a guide to patient selection and treatment planning. Tooth intrusion has been associated with non-rigid connectors 3-5 and so this was avoided in this case. The risk of complications to the abutment tooth from periodontal disease and the implant with peri-implantitis were minimized by treating a patient who was periodontally stable, a nonsmoker with excellent oral hygiene and maintenance compliance. Supragingival restorative margins were also provided on the abutment tooth. Technical and biologic complications related to the implant, its abutment and the tooth may also be due to factors such as the presence of bruxism, and the retentive qualities of the tooth preparation. Bragger et al. 6 reported a greater incidence of complications with I-I and I-T FPDs in bruxers. Therefore, it was important to the authors of this case report that there was no evidence of parafunction. Lang et al. 4 reported that loss of retention often preceded complications to the abutment tooth. This agrees with observations of conventional tooth-borne FPDs. 8,9 With this in mind, care was taken to provide adequate resistance and retention form with minimal taper of axial walls on the abutment tooth, providing a preparation parallel with the implant abutment and enhanced resistance form with mesial and distal retention grooves. This case report represents a follow up of 32 months, and while there are no signs of any complications on either the tooth or the implant, careful maintenance and observation will be required to reduce the risk of a reduced survival outcome up to and beyond a 10-year observation period. ACKNOWLEDGEMENTS The authors would like to acknowledge the Faculty of Dentistry at The University of Sydney. The treatment was performed as part of clinical requirements for the Graduate Diploma in Clinical Dentistry (Oral Implants). Acknowledgement is also made of Mr Robert Hill, a dental technician who undertook fabrication of the restoration. REFERENCES 1. Lindh T, Gunne J, Tillberg A, Molin M. A meta-analysis of implants in partial edentulism. Clin Oral Implants Res 1998;9: Australian Dental Journal 2006;51:3.

5 2. Renouard F, Rangert B. Risk factors in implant dentistry. Carol Stream: Quintessence Publishing Co. Inc.,1999: Naert I, Duyck J, Mahmoud M, Van Steenberghe D. Freestanding and tooth-implant connected prostheses in the treatment of partially edentulous patients. Part I: An up to 15-years clinical evaluation. Clin Oral Implants Res 2001;12: Lang N, Pjetursson B, Tan K, Bragger U, Egger M, Zwahlen M. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. II. Combined tooth-implant-supported FPDs. Clin Oral Implants Res 2004;15: Lindh T, Dahlgren S, Gunnarsson K, et al. Tooth-implant supported fixed prostheses: a retrospective multicenter study. Int J Prosthodont 2001;14: Bragger U, Aeschlimann S, Bürgin W, Hämmerle C, Lang N. Biological and technical complications and failures with fixed partial dentures (FPD) on implants and teeth after four to five years of function. Clin Oral Implants Res 2001;12: Gunne J, Astrand P, Lindh T, Borg K, Olsson M. Tooth-implant and implant supported fixed partial dentures: a 10-year report. Int J Prosthodont 1999;12: Schwartz NL, Whitsett LD, Berry TG, Stewart JL, Unserviceable crowns and fixed partial dentures: life-span and causes for loss of serviceability. J Am Dent Assoc 1970;81: Valderhaug J. A 15-year clinical evaluation of fixed prosthodontics. Acta Odontol Scand 1991;49: Address for correspondence/reprints: Dr Damian Clarke 242 Lower Heidelberg Road Ivanhoe East, Victoria dclarke@clarkedental.com.au Australian Dental Journal 2006;51:3. 267