Complications of Removable Implant Supported Prostheses
Introduction
The two main complications that result from removable implants are biological and mechanical/technical complications. There is need to assess and interpret data on the incidence of complications, both biological and technical with caution. Berglundh, Persson, and Klinge (2002), found that implant loss was the most common problem, while technical complications were observable in about 60-80% and biological complications – 40-60% of the studies they evaluated. According to Sadowsky (2007), there are no specifications on the length, distribution, and number of implants; however the suggestion for non-palatal coverage designs should be a minimum of 4 implants. In case of risk factors such as off-ridge relations, or compromised quality of bone, there should be at least 6 implants placed to avoid changes in prosthetic design. Despite the lack of literature linking length of implant to implant failure, the suggested survival length for 12mm long maxillary overdentures is about 5 years (Sadowsky, 2007).
In comparison, the removable prosthetic design has been favored over the fixed implant completed denture by patients with a moderate complete denture experience regardless of the palatal coverage. The removable design has also been linked with producing more intelligible speech in comparison to its counterpart (Sadowsky, 2007). Bryant, MacDonald-Jankowski, & Kim (2007) ascertain the need for selecting a removable or fixed type of implant specifically in case of a completely edentulous arch. Therefore it is essential to consider some of the complications associated with each type of implant as well the available remedies in form of techniques and methods before use. The long-term efficacy of wearing removable complete dentures has been confirmed by various researchers (Bryant, MacDonald-Jankowski, & Kim, 2007). This article focuses on the complications associated with removable implant supported prostheses and addresses some of the preventive and managing measures for these problems.
Complications and Problems of Removable Implant Supported Prostheses
Among the main issues patients face after undergoing treatment using the removable implant supported prosthesis is the loss of removable implants. There are two main types of complications in removable implant structured dentures; biological and technical complications. Biological complications are disturbances in the functioning of the implant due to biological mechanisms that have an effect on the tissues that support the implant. Biological complications include implant loss – early and late losses as well as peri-implant tissues reactions. It is vital to detect such complications early; detection of these complications requires radiographic and clinical methods of examination (Berglundh, Persson, and Klinge 2002). Technical complications refer to the mechanical damage of the suprastructures or of the implant and implant components. There is a high incidence of technical complications which is perceived to result from the use of some implant systems. Single crowns, over-dentures, fixed complete bridges and fixed partial bridges are some of the common implant supported reconstructions (Berglundh, Persson, and Klinge 2002). The subsequent sections entail discussions on the loosening of abutments and of bar screws, broken, lost, or loose retainers, placement of new retainers, fracture of bar, and tightening of female retainers as well as fractures of teeth, denture base resin, and cast framework and the need for new prosthetic designs.
Splinted versus Non-Splinted Anchorage Systems: Comparison
The choice of implant system could result in certain prosthetic complications. Non-splint anchorage systems may be well suited for the management of splinted designs as they seemingly require less space in the prosthesis, are less technique sensitive, more economical and easier to clean(Sadowsky, 2007). Magnets have illustrated low retention in comparison to other attachment systems however they are seemingly suitable for patients with dexterity or bruxism problems; this is evidenced by more post-insertion visits resulting from corrosion. The use of solitary anchors and bars for maxillary implant overdentures for instance has illustrated higher incidence of patient satisfaction. Bars are however associated with increased occurrence of hyperplasia (Sadowsky, 2007). Complications linked to the anchorage system are common for overdenture patients these include repair of female retainers and retightening of the bar screw. Complications linked to particular types of attachment system were found by Kiener et al., (2001), to be prosthetic rather than implant-related complications.
Main Issues: Removable Implant Supported Dentures
Removable implant supported dentures are mainly affected by prosthodontic issues. The prosthetics however have a high survival rate, but in the long-run biological and technical issues affect the implant. These issues include soft tissue complications and bone loss. Patients might choose removable over fixed dentures due to issues such as cost effectiveness and patient satisfaction however the popularity of combined tooth-implants is still prevalent. There are numerous studies that compare removable implant-supported dentures as well the complications involved with these. Nedir et al., (2006), conducted a study on prosthetic complication linked to overdentures. It was found that the survival rate of removable implant-supported prostheses was 99.2% after, but with time this reduced to wear. The patients in the study with removable prostheses were found to have more complications compare to ones with fixed – 66.0% versus 11.5% respectively. The study found a significant difference of P< 0.01. The rate of complications for ball-retained prostheses was also significantly (P = 0.04) higher than bar-retained ones at 77.5% versus 42.9%. The cases of complications were more in the removable group however they were also easier to deal with (Nedir, 2006).
An implant loss is considered as an early loss resulting from a lack of tissue integration. In a study by Kiener et al. (2001), 41 patients received 173 ITI implants; five implants were lost in the first year of loading – early failure and four were lost in the second year – later failure. However 95.5% of implants were found in situ at the time of clinical examination. The frequent loss of maxillary implants especially in combination with overdentures is many cases linked to short implants of 10mm (Kiener et al., 2001). According to Visser et al., (2006), loosening of retentive mechanism constitutes 33% and implant loss in bone-type IV was 16% of the complications associated with implants and implant prostheses. Implant loss is associated with insufficient retention of dentures and reduced stability. Most of the implants are lost during the first year of placement and specifically in patients of higher bone height in the mandibular symphysis region. Loosening and detaching attachments are also linked to the use of ball attachments over bar implants. Most of the retention issues were linked to technical or biological complications discussed by numerous researchers.
Biological Issues
Biological issues include soft tissue loss and bone loss and these complications are common-placed in the case of removable implant-support dentures. Soft tissue complications are characterized by symptoms from peri-implant tissues – excessive swelling, persisting pain, fistula or suppuration, and hyperplasia requiring surgery (Berglundh, Persson, and Klinge 2002). According to Kiener et al., (2001), there were several incidences of sore spots removal in patients in the first year but no incidence of stomatitis however other studies suggest increased occurrence of stomatitis and mucosal irritations associated with maxillary overdentures. Hyperplasia underneath the bar was repeatedly found in three of the patients making treatment very necessary. The need for correction of soft tissue problems is more common with bar design than with ball attachments (Klemetti, 2008). Peri-implantitis entails a combination of probing depth of over 6mm, attachment loss or bone loss of 2.5mm and bleeding on probing/suppuration. The occurrence of crestal bone loss is also common. There is evidence of an 80-95% range of implant stability that can be maintained for over 10 years; after the first year the average rate of crestal bone loss is estimated at less than 0.1mm yearly (Bryant, MacDonald-Jankowski, & Kim, 2007). Lack of stability of an implant is an influencing factor with regard to the retention of prostheses.
Mechanical and Technical Issues
There are a number of technical issues associated with removable implants which may lead to their loss. Implant stability and retention are affected by the design and type of attachments. Technical issues are the leading causes for the higher need for patient aftercare in the case of removable prosthesis in comparison to fixed prosthesis. In the study by Visser et al., (2006) the incidence of necessary prosthetic care is higher in the case of implant-retained overdenture patients in comparison to patients with conventional dentures. Bars with extensions were found to be more susceptible to complications due to some fractures of the distal bar extensions. However these were prosthetic complications as they did not affect the wearing of the dentures (Kiener et al., 2001). Mechanical retention problems such as the antero-posterior rotation of the prosthesis are considered as unforeseeable while foreseeable problems include relining, and need to change the clip (Nedir, 2006).
Type of Material
The type of material used to design implants also influences the survival and success rates of such an implant. Overdentures of acrylic resin teeth primarily retained by an alloy of splinted gold, non-splinted magnet, Dolder bar-and-clip, or by gold alloy attachments are often used for removable implant supported dentures (Bryant, MacDonald-Jankowski, & Kim, 2007). The resin material used for removable dentures is strong and durable as well as flexible and realistic looking. The clips of removable dentures can be made of titanium metal, cobalt-chrome or plastic.
Issues Originating from Removable Implant Supported Dentures
There are several issues associated with the use of removable implant supported dentures. First, the increased need for care and aftercare services associated with this type of prosthesis leads to numerous measures for prevention and managing the complications that arise. Secondly, the issues of patient satisfaction and cost effectiveness also affect the popularity of use for overdentures which might lead to compromised quality prosthetics for the patient. Malocclusion is another common problem that affects removable implants. The retention and success of removable implants is subject to occlusal stresses which in most cases affect the maxilla rather than the mandible (Klemetti, 2008).
Techniques to Prevent and Manage the Problems
Both biological and technical issues linked to removable implant support dentures can be reduced or even solved through appropriate preventive and treatment measures. Visser et al. (2006), found that patients with implant-retained overdentures required more care and aftercare in comparison to conventional dentures. Prosthesis varies in numerous ways such as in terms of prosthetic materials, splinting/rotational characteristics, number and position for support, and abutment designs (Bryant, MacDonald-Jankowski, & Kim (2007). The use of appropriate methods and techniques to remedy problems associated with removable dentures can help to reduce the incidence of complications and consequently lead to fewer cases of patient aftercare procedures as well as patient satisfaction. Adequate evaluation criteria are necessary for determining effective types of implant supported prostheses in order to make more accurate comparisons of prosthetic treatment outcomes. There is need to standardize prosthetic procedures, bone quantity and loading conditions, marginal bone measurements, and number of implants as well as inadequate sample size in order to make an objective assessment of preferred retention systems for overdentures (Kiener et al., 2001). Patient satisfaction should be factored into the decision for different types of prostheses (Visser et al., 2006).
Increase the life of the prostheses
Increasing the life of the prosthesis refers to augmenting its success and survival rate. To achieve this it is necessary to promote denture retention by connecting multiple implants with rigid bars (Kiener et al., 2001). A study by Attard and Zarb suggests a cumulative survival rate of 10-19 years among 132 implants originally placed to support 47 complete removable dentures by using appropriate implant design (Bryant, MacDonald-Jankowski, & Kim, 2007). It was found that Branemark-type bar-clip over-dentures were more successful prosthesis as they required less maintenance in comparison to the spring ball attachment and titanium alloy matrix overdentures from the same manufacturer (Klemetti, 2008). This suggests that the design of the prosthesis is an essential factor in prolonging the life of the prosthesis.
Choose Fixtures of Appropriate Type, Size, and Design
Choosing the appropriate type, design, and size of a prosthetic feature is essential in preventing and managing complications associated with removable implant supported dentures. Bryant, MacDonald-Jankowski, & Kim’s, (2007), study on the difference of implant success and survival outcomes of removable prosthesis in edentulous arches results indicate that the features of the prosthesis affects its success and survival rate. This variation in designs such as using the Dolder bars helps to reduce the amount of care and aftercare necessary for implant supported dentures. Kiener et al. (2001), estimated a mean of 2.4 complications for overdentures with extension bars; the use of extension bars makes the implants more susceptible to complications. According to Klemetti (2008), there little significant difference in using ball attachments and a bar however the bar provides more stability. The combination of a bar and two implants seems to result in the least number of repairs and complications (Klemetti, 2008). The use of dentures with an open-horseshoe design limits contact surface between the underlying soft tissue and denture base and results in lower incidence of stomatitis.
Control of opposing occlusal stresses
Occlusal stresses often interfere with the retention and success of removable implant supported dentures. In the maxilla, prosthetic implants are predisposed to stronger occlusal forces in comparison to the mandible. Therefore it is advisable to use a maxillary over-denture that is completely implant-borne than implant-supported and soft-tissue borne (Klemetti, 2008). The benefit of this is the less noticeable denture rotation as well as enhanced survival of the prosthesis. Generally, maxillary over-dentures should be reserved for patients with advanced alveolar atrophy, maxillary ridge anatomy, and other conditions that may compromise the stability and rention of a maxillary fixed denture implant (Klemetti, 2008).
Provide Appropriate Maintenance and Promote Oral Hygiene
In order to prevent and correctly manage removable implant supported dentures, promoting oral hygiene and affording necessary maintenance to patients is vital. According to Visser et al. (2006), it is essential to discuss the maintenance of implant-supported dentures with patients before the placement or a treatment procedure. The need for maintenance of implants results from normal wear and the prosthetic parts becoming excessive. Such as service procedures are often considered as remedying failures and complications of prostheses rather than the implant (Kiener et al., 2001). To measure the repair and maintenance required for the implants it has been suggested to compute the number of patient appointments. It was found that six to nine appointments were necessary in the first year due to technical complications (Kiener et al., 2001). Repairs necessary for removable prosthesis patients include change of the clip, relining, and repair of the overdenture. In cases where implants are lost, it may become necessary to remake the dentures (Kiener et al., 2001). Remake dentures is considerably more expensive than making repairs therefore it is advisable to ensure constant maintenance to avoid a complete remake. Visser et al. (2006) suggest that patients should be subjected to strict regimen of oral hygiene which entails giving the patients necessary instructions to maintain hygiene as well as regular visits to a dental hygienist for oral hygiene inspection.
Decrease Chances of fracture
Future Scope
There has been significant advancement in the technology and specifications of implants which has made them easier to maintain and less costly (Gaviria et al., 2014). The application of technologies such as nanotechnology-based implants and micro casting will improve cell adhesion and protein absorption leading to fewer cases of biological complications from using implants. The nanotechnology can also be useful in the coating of implant surfaces with bone morphogenetic proteins to reduce the incidence of biological complications. The density of the bone is an important factor with regard to implant placement and the use of techniques such as densitometric measurements and dental cone beam CT could lead to the determination of dense bone locations for implant placement. There is a decline in adults missing teeth and this affects future need for prosthodontics. Projections indicate an increase of total unmet need for prosthetics from 488 million hours to 560 million hours in 2020. This information is significant as it indicates an excess of unmet need to available supply of services in the foreseeable future. The implication of this is that the need for removable denture services will persist among a considerable size of the population which affects practicing dentists (Gaviria et al., 2014).
Conclusion
Removable implant-supported dentures are helpful in restoring the function and aesthetics of the teeth. These are often used as transitional options for fixed dentures however their use is also associated with a number of complications – biological and technical. The main issue with removable prosthetics is the lack of retention which results from the aforementioned complications. Biological complications refer to bone loss and soft tissue loss while technical issues are often associated with the use of certain types and designs of implants. Removable prosthetics generally have lower survival and success rates than the fixed implants as well as increased incidence of aftercare however this can be improved by implementing certain techniques and methods. These include lessening the chance of a fracture, affording suitable maintenance and repair as well as oral hygiene, selecting fixtures with appropriate size, design, and type, increasing life of the prostheses and lastly taking into account the presence of opposing occlusal forces. Oral hygiene and maintenance are important elements of the removable implants type dentures. Removing and cleaning the implants is essential to prevent oral problems such as tooth decay and gingivitis. Maintenance and repair of the implants is also vital as it ensures stability and retention of the implants. Selecting the proper material, design, size, and type of implant is also vital.
References
Berglundh, T., Persson, L. and Klinge, B. (2002). A systematic review of the incidence of biological and technical complications in implant dentistry reported in prospective longitudinal studies of at least 5 years. Journal of Clinical Periodontology, 29(s3), pp.197-212.
Bryant, S. R., MacDonald-Jankowski, D., and Kim, K. (2007). Does this type of implant prosthesis affect outcomes for the completely edentulous arch? International Journal of Oral & Maxillofacial Implants, 22, pp.117-139.
Gaviria, L., Salcido, J., Guda, T. and Ong, J. (2014). Current trends in dental implants. Journal of the Korean Association of Oral and Maxillofacial Surgeons, 40(2), pp. 50-60.
Kiener, P., Oetterli, M., Mericske, E, and Mericske-Stern, R. (2001). Effectiveness of maxillary overdentures supported by implants: Maintenance and prosthetic complications. International Journal of Prosthodontics, 14(2), pp. 133-140.
Klemetti, E. (2008). Is there a certain number of implants needed to retain an overdenture? Journal of Oral Rehabilitation, 35(s1), pp.80-84.
Sadowsky, S.J. (2007). Treatment considerations for maxillary implant overdentures: A systematic review. Journal of Prosthetic Dentistry, 97(6), pp.341-350.
Visser, A., Meijer, H.J.A., Raghoebar, G.M. & Vissink, A. (2006). Implant-retained mandibular overdentures versus conventional dentures: 10 years of care and aftercare. International Journal of Prosthodontics, 19 (3), pp. 271-278.
