The Complications of Implant Supported Fixed Prosthetics - Article Example

The Complications of Implant Supported Fixed Prosthetics Introduction There is ever growing reliance on dental implants as the procedure for the treatment of dental patients with complete or partial edentulism, which has resulted in many dental patients being provided with oral implants in their rehabilitation. Such a situation has arisen from the increased awareness among dental patients and dental professional of the advantages that accrue from implant restorations in place of the traditionally used fixed and removable prostheses. The advantages that accrue without any doubt from implant restorations over fixed and removable prostheses are in the functional and biological areas (Kreissel et al, 2007). Increased masticatory efficiency and lack of tissue contact is the key functional and biological advantages in the use of implant supported fixed prosthetics. These implant supported fixed prosthetics function with similarity to the natural denture of the patients and patients appreciate the near normal functionality with such implant restorations. Furthermore, there is greater self-image and self-confidence that results from the feeling and confidence of these implant restorations. In the case of such fixed prostheses there is no requirement for mucosal support. The prosthesis is totally supported by the implant abutment unit, which removes the possibility of prosthesis movement. As a result any possible tissue irritation due to prosthesis movement is completely removed (Stevens, Fredrickson & Gress, 2000). Implant supported prostheses for the rehabilitation of complete or partial edentulism comprises either of removable or fixed restorations. Commonly employed implant-supported fixed prosthesis is made up of a metal substructure and a ceramic veneer. Several studies support the long-term success of such fixed implant supported restorations, though the risk of failure of implant supported fixed prosthetics from complications of the procedure has been less defined. There is also the element of high costs that are associated with implant supported fixed prosthetics. These two factors make it relevant for a better understanding of the risk of failure that arises from the complications of implant supported fixed prosthetics (Kinsel & Lin, 2009). Implant Abutments Implant abutments customized to patient needs are becoming more and more popular in implant supported fixed prosthetics, which target replicating the natural situation. Such abutments are shaped in keeping with the individual anatomical requirements of the site of the implant. Several materials are currently available for the fabrication of these abutments, the more frequently used being metals or ceramics. Each of these materials demonstrates benefits and disadvantages as implant abutments (Zembic et al, 2009). Among the metals used as materials for implant abutments titanium has been found to be the most useful as it demonstrates excellent material stability, and as such is resistant to distortion. Results of clinical investigations have shown high survival rates for restorations that are based on titanium. Titanium has also been found to be a suitable implant abutment for all regions of the jaw. This had resulted in titanium implant abutments being considered the gold standard until recent times. However, titanium suffers from one severe disadvantage in that it causes grey discoloration of the peri-implant mucosa, which leads to impairment of the esthetics in the results from the implant restoration (Zembic et al, 2009). Implant abutments made from ceramic materials like alumina and zirconia offer a solution to the esthetic issues that arise with titanium based implant abutments. There is ample evidence that demonstrates the esthetic benefits of ceramic implant abutments over titanium implant abutments. Yet, these ceramic materials have a disadvantage too. These ceramic materials are brittle. The brittleness property of ceramics makes them less resistant to tensile and makes them prone to micro-structural defects. High tensile forces present during mastication and the possible inherent flaws in the structure raise the potential risk for fracture in ceramic implant abutments during function. The risk for fracture varies with the ceramic materials. From all the ceramic materials used in the creation of implant abutments, zirconia demonstrates the greatest fracture toughness (Zembic et al, 2009). Occlusal Material The occlusal material used for implant supported prostheses have a role to play in the development of complications. Shock absorbing capacity with the ability to and withstand masticatory forces are essential features of good occlusal material to offer protection to the implant-bone interface. Biomechanical features of acrylic resin led to its predominant use during the initial period of the development of implant techniques. Clinical experiences however, led to the consideration of other occlusal material, particularly when it was found that some other occlusal material like porcelain were found to be as good as acrylic resin for use as occlusal material. With no biological consequences found by the use of the hard material of porcelain as occlusal material, and the added benefit of overcoming the most common complications of implant restorations with acrylic resin of the development of fractures, porcelain has become the popular occlusal material in current dental clinical practice. There is general agreement that porcelain as an occlusal material in implant restorations provides superior esthetics and resistance to wear and tear metal ceramic prostheses and acrylic resin continue to be used in implant restorations (Carlsson, 2009). Implant Impressions In the procedure of dental restoration or prostheses the dental impression is a key component as the dental imprint forms the negative imprint for the construction of the replica of the oral structure being replaced. This makes the accuracy of the impression critical in the creation of definitive cast, leading to the fabrication of proper prostheses that gives a good fit. When the impression is inaccurate there is every possibility of a prosthesis misfit that can go on to consequences of mechanical and biological complications. The technical complications that are seen from prosthesis misfit include loosening of the screws, fracture of the screws, fracture of the implant, and occlusal inaccuracies. Discrepancies in the biological margins as a result of prosthesis misfit can lead to soft and hard tissue responses, because of the enhanced load of plaque collection. It is virtually impossible to obtain an absolute passive fit. Yet, minimizing the misfit assists in preventing biological and technical complications, and should remain the objective in implant restorations. Several techniques which include splint, pickup, and transfer techniques have been developed to improve the accuracy in implant impressions. However there is variance in the accuracy in implant impressions, with the pickup technique being superior in accuracy to the transfer technique. Materials used for making the impressions can also contribute to inaccuracies in implant impressions. Polyether and VPS are the two commonly used impression materials, but evidence supports the use of VPS for more accurate impressions. Impression copings using different designs are found to influence the level of accuracy in implant impressions. Evidence has also emerged that angulated implants have been found to contribute to a higher level of inaccurate impressions than is the case with straight implants. Other possible sources of inaccuracies in implant impressions include difference in implant level and abutment level, variance in impression trays, depth of the implant, and delays in the stone pouring (Lee et al, 2008). Complications of Implant Supported Fixed Prosthetics Based on a literature review of the existing body of knowledge on implant supported fixed prosthetics, Abt 2008, found that though high survival rates are associated with implant supported fixed prosthetics, biological and technical complications are a frequent occurrence with implant supported fixed prosthetics, with greater emphasis on technical complications. Gervais and Wilson 2007, support the findings of Abt 2008 that the most frequently encountered complications associated with implant supported fixed prosthetics are biological and technical complications. The consequences of these complications are that they frequently jeopardize the functional utility of the implant supported fixed prosthetics along with reducing the esthetic effectiveness of the prostheses. These complications occur is spite of all the care taken to provide a sound prosthetic design and the high levels of clinical skills and expertise in the dental professional. Such a situation poses a difficulty for clinicians in that they have to evaluate the benefits of prosthetic retrievability, given that there is the likelihood of such complications arising, which also include the costs of replacing the permanently cemented prosthesis. The complications of implant supported fixed prosthetics thus pose a challenge to the philosophy that contributes to permanent cementation in implant supported fixed prosthetics (Gervais & Wilson, 2007). Biological Complications Pjetursson et al 2004, based on a systematic review of the survival and complications of implant supported fixed partial dentures after an observation period of a minimum of five years report that the cumulative rate of biological complications after five years for patients with implant supported fixed partial dentures was 8.6%. The study also found that peri-implant mucosal lesions in its various forms were the most commonly encountered biological complications. The various forms of peri-implantitis encountered were probing pocket depth of 5mm, bleeding on probing, and peri-implantitis at the prostheses placement. Peri-implantitis was found to be more frequent during the first year after the implant restoration procedure, with receding in the frequency of peri-implantitis in the following years. Soft tissue infection or inflammation was found to be a part of the complications arising from such implant restorations. The material used for implant restorations was also found to play a part in the biological complications. Titanium based implants were found to contribute to a higher proportion of implants with signs of inflammation consisting of pain, redness, swelling, and bleeding (Pjetursson et al, 2004). Lang et al 2004, based on a systematic review of the survival and complications of combined tooth implant supported fixed partial dentures after an observation period of a minimum of five years report that the cumulative rate of biological complications after five years for patients with combined tooth implant supported fixed partial dentures was 11.7%. There was less information and impact of peri-implantitis, though peri-implantitis was considered as probing pocket depth of 5mm and bleeding on probing and 13.6% of the patients required treatment for peri-implantitis. In addition there was finding of infrabony pocket formation, where bioceram sapphire based implants were employed in the implant restoration (Lang et al, 2004). Jung et al 2008, based on a systematic review of the survival and complications of combined tooth implant supported single crowns after an observation period of a minimum of five years report that peri-implant mucosal lesions were the most common biological complications associated with combined tooth implant supported single crowns with a cumulative rate of 9.7% five years after the implant restoration procedure. These peri-implant mucosal lesions were described in different terms, such as soft-tissue complications, inflammation, gingival inflammation, gingivitis or bleeding. Fistula formation was a biological complication reported in association with combined tooth implant supported single crowns. Bone loss exceeding 2mm was also seen to occur with an occurrence rate of 6.3% five years after the implant restoration procedure. Another important finding was that the crown design had no influence on the rate of biological complications (Jung et al, 2008). Occlusal overload is associated as a main cause for peri-implant bone loss and implant or implant prosthesis failure. This general association stems from evidence from studies that indicate contribution of occlusal overload to implant bone loss, as well as loss of osseo-integration of successfully integrated implants. However, there is another suggestion arising from evidence from studies that peri-implant bone loss and implant or implant prosthesis failure are a biological complication that stems from peri-implant infection (Kim et al, 2006). Technical Complications Pjetursson et al 2004, based on a systematic review of the survival and complications of implant supported fixed partial dentures after an observation period of a minimum of five years report that the most frequently occurring technical complication consisted of fracturing of the veneer whether it be acrylic, ceramic, or composite. After five years of the implant restoration procedure 13.2% of the patients were found to have fractures of the veneers. The next most common technical complication was the loss of screw access-hole restoration, and found to occur in 8.2% of the anchors after a period of five years from the implant restoration procedure. The next frequently occurring technical complication was abutment or occlusal loosening. The occurrence of this technical complication was found to be 5.8% after five years of the implant restoration procedure. Fractures of abutment and occlusal screws were yet another technical complication with implant restoration procedures and found to occur in 1.5% cases after five years of the implant restoration procedure. Fracture of the luting cement or loss of retention was another technical complication associated with implant restoration procedures. The rate of occurrence was found to be 2.9% five years after the implant restoration procedure. Fracture of the implant itself as a technical complication for implant restorations was found to be rare in occurrence. The rate of occurrence was found to be just 0.4% after five years and 1.8% ten years after the restoration procedure (Pjetursson et al, 2004). Lang et al 2004, based on a systematic review of the survival and complications of combined tooth implant supported fixed partial dentures after an observation period of a minimum of five years report that the most common technical complication reported was veneer fracture whether the material used be acrylic, ceramic, or composite, with an occurrence rate of 9.8% five years after the implant restoration procedure. Rate of veneer fractures ten years after the implant restoration procedure was reported as 9.1%. Loss of retention was also reported as a technical complication in this implant restoration procedure with a rate of occurrence after five years at 6.2% and after ten years at 24.9%. Connection related technical complications consisting of abutment or occlusal screw loosening were also reported in this implant procedure, with an occurrence rate of 3.6% after five years and after ten years. Abutment fractures or abutment screw fractures was yet another technical complication associated with this implant procedure with an occurrence rate of 0.7% five years after the implant restoration procedure. A technical complication that was reported as a rare occurrence with this implant procedure was fracture of the implant. The arte of occurrence of this technical complication was 0.9% five years after the implant restoration procedure. Intrusion of abutment teeth was the final technical complication reported with this implant procedure, with an occurrence rate of 5.2% five years after the implant restoration procedure (Lang et al, 2004). Jung et al 2008, based on a systematic review of the survival and complications of combined tooth implant supported single crowns after an observation period of a minimum of five years report that abutment or occlusal screw loosening was the most frequently encountered technical complication with this implant procedure, with a cumulative occurrence rate after five years of the implant procedure being 12.7%. Use of gold screws was found to increase the rate of the occurrence of this technical complication. The next most commonly occurring technical complication reported with this implant procedure was fracture of the luting cement or loss of retention, with a cumulative occurrence rate of 5.5% five years after the implant procedure. The third most commonly occurring technical complication reported with this implant procedure was fracture of the ceramic or acrylic veneer material that was found to occur at a rate of 4.5% five years after the implant procedure. Fracture of the crown framework was yet another technical complication associated with this procedure and found to occur at a rate of 3% five years after the implant procedure. Technical complications of fracture of components, implants, abutments, and occlusal screws were found to occur, but on a rare basis. The rate of cumulative occurrence of abutment screw fractures five years after the implant procedure was found to be o.35%, while the cumulative rate of occurrence of implant fracture five years after the implant procedure was just 0.14% (Jung et al, 2008). Literary References Abt, E. (2008). Growing body of evidence on survival rates of implant-supported fixed prostheses. Evidence-based dentistry, 9(2), 51-52. Carlsson, G. E. (2009). Dental occlusion: modern concepts and their application in implant prosthodontics. Odontology, 97, 8-17. Gervais, M. J. & Wilson, P. R. (2007). A rationale for retrievability of fixed, implant-supported prostheses: a complication-based analysis. The International journal of prosthodontics, 20(1), 13-24. Jung, R. E., Pjetursson, B. E., Glauser, R., Zembic, A., Zwahlen, M. & Lang, N. P. (2008). A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clinical oral implants research, 19, 119-130. Kim, Y., Oh, T., MIsch, C. E. & Wang, H. (2006). Occlusal considerations in implant therapy: clinical guidelines with biomechanical rationale. Clinical oral implants research, 16, 26-35. Kinsel, P. R. & Lin, D. (2009). Retrospective analysis of porcelain failures of metal ceramic crowns and fixed partial dentures supported by 729 implants in 152 patients: Patient-specific and implant-specific predictors of ceramic failure. The Journal of Prosthetic Dentistry, 101(6), 388-394. Lang, N. P., Pjetursson, B. E., Tan, K., Bra’gger, U., Egger, M. & Zwahlen, M. (2004). A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clinical oral implants research, 15, 643-653. Lee, H., So, J. S., Hochstedler, J. L. & Ercoli, C. (2008). The accuracy of implant impressions: A systematic review. The Journal of Prosthetic Dentistry, 100(4), 285-291. Pjetursson, B. E., Tan, K., Lang, N. P., Bra’gger, U., Egger, M. & Zwahlen, M. (2004). A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clinical oral implants research, 15, 625-642. Kreissel, M. E., Gerds, T., Muche, R. Heydecke, G. & Strub, J. R. (2007). Technical complications of implant-supported fixed partial dentures in partially edentulous cases after an average observation period of 5 years. Clinical oral implants research, 18(6), 720-726. Stevens, P. J., Fredrickson, E. J., & Gress, M. L. (2000). Implant prosthodontics: clinical and laboratory procedures‎. Oxford: Elsevier Health Sciences. . Zembic, A., Sailer, I., Jung, R. E. & Ha’mmerle, C. H. F. (2009). Randomized-controlled clinical trial of customized zirconia and titanium implant abutments for single-tooth implants in canine and posterior regions: 3-year results. Clinical oral implants research, 20(8), 802-808. Read More