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It is estimated that between 2 million and 3 million dental implants are placed and restored each year in the United States.1,2 Dental implants are reported to have a high mean cumulative survival rate of 96.1% post-loading, but survival is generally defined as the implants being present and in function and does not consider overall implant health or disease.3 Rates of peri-implant mucositis and peri-implantitis have been noted to be approximately 43% and 22%, respectively, with the prevalence of peri-implant disease increasing with implant function time.4 Given the volume of implants placed and the prevalence of peri-implant diseases, it is critical that dental healthcare professionals are able to make evidence-based treatment recommendations that can reduce the patient's risk for developing peri-implant diseases. This article reviews common risk factors for peri-implant diseases and recommendations for dental implant care that can prevent development of such diseases.
Definitions and Prevalence of Peri-Implant Diseases
A healthy dental implant is characterized by a lack of clinically discernable inflammation. In health, the peri-implant soft tissues demonstrate a firm consistency. There is no bleeding or suppuration on probing, probing depths remain stable from baseline, and marginal bone levels are stable after initial physiologic bone remodeling that occurs after restoration. While physiologic remodeling may differ based upon the individual implant geometry, restorative connection, and apico-coronal implant placement, bone loss >/= 2 mm after restoration is considered to be indicative of progressive bone loss and peri-implantitis.5 Implants with peri-implant mucositis, on the other hand, present with clinical signs and symptoms of inflammation (eg, erythema, edema, profuse bleeding and/or suppuration on gentle probing, and increasing probing depths) without progressive marginal bone loss.5 Peri-implant mucositis is considered a reversible condition, but it is also a precursor to peri-implantitis when left untreated. Peri-implantitis is an immune-modulated biological condition of dental implants that is defined by clinical inflammation and progressive bone loss.5 The histological lesions seen in peri-implant diseases are larger than those in analogous lesions around teeth.5-7 Clinically, implants with peri-implantitis demonstrate progressive bone loss that is generally circumferential in nature.8
The case definitions published in the 2018 American Academy of Periodontology/European Federation of Periodontology World Workshop on Classification of Periodontal and Peri-implant Diseases have facilitated investigations evaluating the prevalence of peri-implant diseases. Peri-implant mucositis and peri-implantitis in European, South American, and North American populations have been estimated to be 43% (confidence interval [CI] of 32% to 54%) and 22% (CI of 14% to 30%), respectively.4 Despite the fact that these diseases are extremely common, predictably successful treatment options have not been identified. Current peri-implantitis therapies have demonstrated short-term benefits at best.9 Some interventions for peri-implant diseases demonstrate recurrence rates of peri-implantitis of up to 100% after 12 months.10 Overall, 75% of peri-implantitis cases remain unresolved after treatment or recur within 5 years.11 Given the current paucity of effective therapies for peri-implant disease, it is imperative that dental healthcare providers seek to center prevention of peri-implant disease as an integral part of implant therapy.
Risk Factors for Peri-Implant Diseases
Experimentally induced peri-implant mucositis has confirmed a microbial primary etiology for peri-implant diseases.12,13 While many of the microbes seen in the peri-implant disease biofilms are also present in periodontal disease, new discoveries have focused on the unique dysbiotic biofilms associated with peri-implant disease and their interactions with the implant surface substrate that may make it more challenging to treat peri-implant diseases and fully eliminate an inflammatory immune-mediated reaction once it is established. While biofilms associated with periodontitis and peri-implantitis have bacteria such as P. gingivalis, T. forsythia, and T. denticola in common, peri-implant microbiota also include a more heterogenous group of bacteria, including many strict and facultative anaerobes.14-17 Furthermore, the effects of the dysbiotic biofilms are modified by patient-, implant-, site-, prosthetic-, and clinical/surgical-related factors (Figure 1).
Patient compliance with home-care recommendations and professional dental hygiene care is critical to the long-term success of dental implants. Patients who were not practicing adequate oral hygiene were shown to be 3.8 times more likely to develop peri-implantitis than those with optimal oral hygiene practices.18 Plaque accumulation and increased plaque indices have been associated with an increased likelihood of peri-implant mucositis and peri-implantitis.7,19 While patient-delivered home care alone is not adequate to achieve the resolution of peri-implant diseases,20 meticulous oral hygiene delivered over a period of time has been shown to positively impact the oral microflora.21 In addition to enhanced oral hygiene measures, adherence to regular professional peri-implant maintenance has been associated with lower incidence of peri-implantitis and implant loss.22-25 In fact, individuals who received regular, professional maintenance care in the 5 years following implant placement demonstrated 50% less peri-implantitis cases compared with those who did not visit the dental office during that time.26 Given these findings, a risk-based, regular maintenance protocol should be considered the standard of care for individuals with dental implants.27,28
The majority of tooth loss in adults is due to periodontitis.29 In such patients, tooth replacement with dental implants carries additional risk given that a history of periodontitis has been shown to increase the risk for development of peri-implantitis by up to 19-fold.7 Furthermore, implants that replaced periodontally involved teeth demonstrated more peri-implant bone loss than those that replaced teeth lost due to other causes,30 and the presence of untreated periodontal disease with residual pocket depths of ≥ 5 mm conveyed a significant increase in the risk for development of peri-implantitis.24,31,32 These findings indicate that treatment of periodontitis to appropriate end points prior to implant placement and strict implant maintenance protocols for dental implant patients with a history of periodontitis should be undertaken to reduce the risk for peri-implantitis.33
Both tobacco use and glycemic control related to diabetes mellitus have been identified as significant modifiers to periodontal disease progression.34 It is unsurprising, therefore, that both smoking/vaping and diabetes mellitus have been associated with an increased risk of development of peri-implant diseases.7,28,31 Smoking has been associated with a higher risk of peri-implantitis and implant failure.35,36 This relationship appears to be due to the influence of nicotine on oral tissues, and vaping has been associated with more severe effects than even those seen with cigarette smoking.37 The relationship between tobacco use and peri-implant disease has been shown to be dose-dependent with higher risk conveyed by greater current and past tobacco use.35 Dysglycemia associated with diabetes mellitus has been associated with altered wound healing and a hyper-inflammatory state. Diabetes mellitus has been associated with a significant increase in risk for peri-implantitis.38 Patients who present with systemic factors associated with increased risk of peri-implant disease, including tobacco use and dysglycemia, should be informed of the increased risk of implant disease and counseled about modifications to their overall health. Further, such systemic factors should be considered when developing maintenance recommendations for individuals with dental implants.28
Implant designs differ with various implant systems, and implant surface characteristics, platform designs, and implant geometry may convey differing risk levels for peri-implantitis. For example, moderately roughened implant surfaces demonstrated lower rates of peri-implantitis when compared with minimally roughened and very rough implant surfaces.39 It should also be noted that once exposed to the oral environment, roughened surfaces are more plaque retentive than smooth surfaces, which may perpetuate progressive peri-implant bone loss once peri-implantitis has been initiated.40
It should be noted that while titanium and titanium alloys have been shown to be biocompatible in most cases, no metal or metal alloy is completely inert once it is implanted in the human body. As the metallic implant is installed and is in contact with bodily fluids and tissues, particles can be released as a result of friction and/or dissolution.41,42 An increased presence of titanium particles in subgingival plaque and peri-implant tissues has been observed at implants with peri-implantitis when compared with healthy implants.43,44
Implant site-related factors
Implant site-related factors—including anatomical factors, previous implant failure, history of odontogenic infection, and periodontal phenotype—can also influence the likelihood of developing peri-implant disease. The anatomical position of the dental implant may impact access for home care and professional dental hygiene procedures. Furthermore, implant placement at sites with a previous implant failure45 or residual infection46 have demonstrated increased subsequent failures. This may indicate that in such cases, bacterial flora associated with the chronic and/or acute infection could spread to the implant after placement.45,46 Periodontal phenotype, particularly the width and thickness of keratinized mucosa, have been associated with peri-implant bone levels. A width of keratinized mucosa less than 2 mm has been associated with greater plaque accumulation and marginal bone loss,49,50 and a vertical tissue thickness of less than 2 mm is also associated with 2 to 3 X more marginal bone loss in the first year after implant restoration.47,48 Given the importance of soft tissue quality and quantity around implants, peri-implant phenotype modification through soft and/or hard tissue grafting has been shown to improve long-term outcomes and promote peri-implant health.50,51
Prosthetic factors, including residual cement, occlusal overload, and prosthetic contours, can impact marginal bone levels around dental implants. As a result, proper restorative planning and/or alteration of restorations may positively impact implant outcomes. Cemented restorations have demonstrated significantly higher rates of peri-implantitis when compared with screw-retained restorations.52 The impact of residual cement also seems to be particularly pronounced in patients with a history of periodontitis.53 Occlusal overload and off-axis occlusal forces have been found to be associated with marginal bone loss and loss of osseointegration of dental implants, particularly in the presence of mucosal inflammation.54,55 Over-contoured restorations can impair plaque removal and lead to development of peri-implant disease.54 In cases where the emergence angle was greater than 30º, a more than 2-fold increase in peri-implantitis was seen.56 Given these prosthetic considerations, preferential use of screw-retained restorations where possible to allow for retrievability could improve long-term outcomes and allow for restorative modifications while eliminating subgingival residual cement reported with cemented implant restorations.
Implant malpositioning has been highly associated with the development of peri-implantitis.54 This association is likely a result of the increased potential for off-axis occlusal forces and poorly contoured restorations on malpositioned implants.57 Utilization of guided surgical techniques has been shown to improve implant placement accuracy.58 It should be noted that both static and dynamic guided protocols must be based upon accurate initial data and implant planning based upon sound surgical principles.59,60 Furthermore, adherence to proper surgical technique, including surgical asepsis and appropriate drilling protocols, is imperative for optimal implant outcomes. Introduction of infection and/or improper preparation of the osteotomy site can lead to local necrosis and failure of osseointegration. Careful postsurgical management and early identification of postoperative wound healing concerns, including the exposure of dental implant cover screws during the healing process (Tal exposures), are also critical to reduce early bone loss in the postsurgical healing period.61
Maintenance of Dental Implant Health in Practice
Given the high number of dental implants placed annually and an increasing focus on long-term success rates for dental implants, the prevention of peri-implant diseases has come to the forefront. Dental implant placement and restoration requires an interdisciplinary approach, and a similar focus on the multifactorial risks for development of peri-implant diseases should be employed as a part of ongoing implant maintenance to achieve optimal implant health. Dental healthcare professionals should develop risk-based maintenance protocols for dental implant patients and emphasize regular examinations, professional dental hygiene care, and effective home care to promote long-term success.28,62,63 It has been noted that increases in training and familiarity with implant protocols is associated with an increased emphasis on preventive oral hygiene protocols during implant maintenance by dental healthcare professionals.64 These findings highlight the importance of continuing education on best practices for implant maintenance. Furthermore, a consensus statement from the 11th European Workshop on Periodontology confirmed the importance of both home care and professional dental hygiene care in the maintenance of peri-implant health.65
Home-care recommendations for dental implants
Patients who have received dental implants have, on average, worse baseline oral hygiene practices than patients who have maintained their natural dentitions.66 In addition, implant contours and surfaces differ from teeth and require implant-specific armamentarium and careful instructions to allow patients to master these hygiene techniques.67 Adequate removal of oral biofilm (approximately 80% to 85%) every 12 hours is a critical component to reduce biofilm mass and dysbiosis.68 Twice-daily toothbrushing should be performed using a soft manual or electric toothbrush. Interdental biofilm removal can be accomplished with nylon-coated interdental brushes, tape dental floss, or water flossers. Floss can be used in a "shoe-shine" rag fashion with the floss crossed on the buccal implant surface to best access all areas of the implant fixture.69 Utilization of oral hygiene aids for dental implants may require additional armamentarium, including nylon-coated interdental brushes, angled or end-tuft brushes, or water jets or flossers.67,69 Because of the contours of dental implants, adaptation of oral hygiene aids may require alteration of techniques and coaching by a dental healthcare professional.67,69
Professional hygiene care in the dental office
Implant maintenance protocols should include a careful clinical and radiographic assessment of peri-implant health. Unlike periodontitis where a probing depth of ≥ 4 mm is generally a sign of disease, peri-implant disease is characterized by increasing probing depth, bleeding and/or suppuration on gentle probing, and/or radiographic bone loss.7 These differences also highlight the need for baseline clinical periodontal charting and parallel radiographs that accurately capture bone levels as well as accurate continued assessments at regular intervals. More frequent radiographic examination may be needed for dental implants when compared with natural teeth because progressive bone loss is a defining diagnostic finding for peri-implantitis.
Because of the differences in adherence of mineralized accretions to implant surfaces, mechanical instrumentation that is performed during professional dental hygiene procedures should focus on biofilm removal in health and utilize an armamentarium that maintain the surface integrity of the dental implants.66,67 Utilization of air-abrasion technology, waterjet irrigation, specialized implant ultrasonic tips, and nonmetal instruments have been suggested for roughened surface dental implants to avoid disruption of the titanium surface and induction of titanium particle dissolution into the peri-implant soft tissues.16,66,67,69-72 A frequency of regular periodontal maintenance ranging from 3-6 months has demonstrated the optimal maintenance of dental implant health.27,28,73 It has also been established that individuals with increased risk factors for peri-implant diseases may require more frequent peri-implant maintenance to reduce the risk of developing peri-implantitis.28 It has also been shown that initial bone loss for peri-implantitis can be seen radiographically as early as 6 months, and the majority of dental implants that develop radiographic bone loss do so within the first 3 years after functional loading.74 Frequent implant maintenance should, therefore, begin during the initial period of loading for all implants with maintenance intervals re-evaluated as a part of patient evaluation. A checklist for implant maintenance procedures is summarized in Figure 2.
Mechanical plaque removal and professional maintenance are critical to establishing optimal implant health. Regular and effective patient-administered and professionally delivered biofilm control performed in combination reduce peri-implant clinical inflammation, although complete resolution of inflammation may not be fully achieved in all cases.75 Employment of a comprehensive understanding of risk factors for peri-implant diseases to develop individualized personalized peri-implant maintenance protocols is critical to reduce the incidence of peri-implant diseases and identify the initial signs of disease to allow for more effective treatment.76
About the Authors
Maria L. Geisinger, DDS, MS
University of Alabama at Birmingham
Department of Periodontology
Janie L. Boyesen, DDS, DMSc