Peri‐implant disease is classified into two types: peri‐implant mucositis and peri‐implantitis [1, 2]. The definitions of peri‐implant diseases were first proposed at the first European Workshop on Periodontology [1]. Peri‐implant mucositis was defined as a reversible inflammatory reaction in the soft tissues surrounding a functioning implant, and peri‐implantitis was described as inflammatory reactions associated with loss of supporting bone around an implant in function [1]. According to the diagnostic criteria suggested in the Consensus of the Seventh European Workshop on Periodontology, peri‐implant mucositis was defined as bleeding on gentle probing(<0.25 N), and peri‐implantitis is characterized by changes in the level of the crestal bone in conjunction with bleeding on probing with or without concomitant deepening of peri‐implant pockets [3, 4]. The Consensus of the 2017 World Workshop on the Classification of Periodontal and Peri‐Implant Diseases and Conditions presented the main clinical characteristic of peri‐implant mucositis as bleeding on gentle probing [5]. Erythema, swelling, and/or suppuration may also be present (Figures 2.1–2.3). Peri‐implantitis was defined as a plaque‐associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri‐implant mucosa and subsequent progressive loss of supporting bone [5] (Figures 2.4–2.6).

Implants are designed to function over long term [6], yet many studies suggest that the prevalence of peri‐implant disease is higher than expected [7–9]. In 2013, Atieh et al. reported in a systematic review and meta‐analysis that the summary estimates for the frequency of peri‐implant mucositis were 63.4% of participants and 30.7% of implants, and those of peri‐implantitis were 18.8% of participants and 9.6% of implants [8]. Another systematic review from 2015 reported the prevalence of peri‐implant disease ranged from 19 to 65% for peri‐implant mucositis and from 1 to 47% for peri‐implantitis [7]. Since there is evidence suggesting that peri‐implant mucositis is the precursor of peri‐implantitis [10, 11], and the progression of peri‐implantitis appears to be faster than that observed in periodontitis [5], it is essential to better understand peri‐implant diseases and implement preventive strategies [12].

Prevalence of Peri‐implant Mucositis and Peri‐implantitis

Several recent studies have provided more information about the epidemiology of peri‐implant diseases in different geographical areas as shown in Table 2.1 [3,13–18]. The prevalence of peri‐implant mucositis ranged from 23.9 to 54.5% at patient‐level and from 27 to 69.2% at implant‐level, and those of peri‐implantitis ranged from 9.7 to 56.6% at patient‐level and from 9.2 to 27.9% at implant‐level [3,14–18].

Variability in the prevalence of peri‐implant disease might be attributable to differences between studies with different study designs, limited convenience sample, and unstandardized diagnostic criteria for peri‐implant diseases. A retrospective cross‐sectional study from India reported the prevalence of peri‐implant mucositis to be 0.33%, which is evidently lower than various other studies done by other authors [19]. Besides, French et al. reported that the prevalence of mucositis varied from 18.2% using the “relaxed” bleeding‐on‐probing scores threshold (moderate multipoint bleeding) to 49.5% using a “strict” bleeding‐on‐probing scores threshold (minimal single‐point bleeding) [13], and the prevalence of peri‐implantitis (combination of mucositis and marginal bone loss ≥1.0 mm) varied from 3.6% using relaxed criteria to 4.7% using strict criteria, which means the prevalence of peri‐implant diseases differed depending on the corresponding definition [13, 14]. Interestingly, recent studies have defined an intermediate peri‐implant health category between peri‐implant mucositis and peri‐implantitis; for example, Romandini et al. denominated peri‐implant mucositis as presence of bleeding and suppuration on probing together with radiographic bone levels(BL) <1 mm, pre‐peri‐implantitis as presence of bleeding and suppuration on probing together with 1 mm≦BL <2 mm, and peri‐implantitis as presence of bleeding and suppuration on probing together with radiographic BL ≧2 mm [14]. Under this definition, the prevalence (at patient‐level) of peri‐implant mucositis was 11.1%, of pre‐peri‐implantitis was 31.3%, and of peri‐implantitis was 56.6%; the prevalence (at implant‐level) of peri‐implant mucositis was 31.9%, of pre‐peri‐implantitis was 31.7%, and of peri‐implantitis was 27.9% [14]. Therefore, epidemiological studies with a cross‐sectional design, adequate sample sizes, and standardized diagnostic criteria are necessary to study the prevalence and risk indicators of peri‐implant diseases.

Risk Factors of Peri‐implant Mucositis and Peri‐implantitis

Many factors, such as diabetes mellitus [20], poor oral hygiene [20, 21], periodontitis [20–22], smoking [23–26], implant surface roughness [23], augmentation at the implant site [23], type of dentition [23], bacterial micro‐leakage at the implant–abutment interface [27], lack of keratinized mucosa [27], residual excess cement [28], implant location [21], and prosthetic design [29] were described as factors enhancing the risk of peri‐implant disease. There are limited data available to support systemic conditions as risk indicators for peri‐implant mucositis and peri‐implantitis; besides, many of these studies have not included all these factors in their statistical analysis.

As shown in Table 2.1, a history/presence of periodontitis, smoking, systemic disease, poor oral hygiene/plaque control record (PCR) (>20%), keratinized tissue width (<2 mm), implant position (maxilla), surgical procedure (two‐stage), frequency of maintenance, number of dental implants, and surgical technique (two‐stage) [3, 15, 17, 18] were reported as risk factors for peri‐implant mucositis recently. While the cross‐sectional study from Spain using a network of sentinel dentists reported that none of the studied variables (including length and diameter of implants, surface roughness, keratinized tissue‐mid‐buccal, and prosthesis) were significantly associated at univariate or multivariate level with mucositis [15]. As for peri‐implantitis, a history/presence of periodontitis, smoking, poor oral hygiene/PCR (>20%), keratinized tissue width (<2 mm), implant position/location (maxilla), surgical procedure (two‐stage), number of dental implants, diameter and surface of dental implants, type of prosthesis, <16 remaining teeth, implant brand, restoration type (bridge versus single crown), supportive therapy, trauma as reason of tooth loss (versus caries), autoimmune disease, gender, and bisphosphonate use [3,13–18] were reported as risk factors for peri‐implantitis recently (Table 2.1). Among those studies, the university‐representative cross‐sectional study from Spain indicated that interproximal flossing/brushing, proton pump inhibitors, and anticoagulants were protective indicators for peri‐implantitis [14].