Success Criteria in Implant Dentistry: A Systematic Review

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1 RESEARCH REPORTS Clinical P. Papaspyridakos 1 *, C.-J. Chen 1,2, M. Singh 1, H.-P. Weber 1,3, and G.O. Gallucci 1 1 Harvard School of Dental Medicine, Department of Restorative Dentistry & Biomaterials Sciences, 188 Longwood Avenue, Boston, 02115, USA; 2 Chi-Mei Medical Center, Department of Dentistry, Liouying, Taiwan; and 3 Tufts University School of Dental Medicine, Department of Prosthodontics and Operative Dentistry, Boston, MA, USA; *corresponding author, panpapaspyridakos@gmail.com Success Criteria in Implant Dentistry: A Systematic Review J Dent Res X(X):xx-xx, XXXX Abstract The purpose of this study was to examine the most frequently used criteria to define treatment success in implant dentistry. An electronic MEDLINE/ PubMED search was conducted to identify randomized controlled trials and prospective studies reporting on outcomes of implant dentistry. Only studies conducted with roughened surface implants and at least five-year follow-up were included. Data were analyzed for success at the implant level, peri-implant soft tissue, prosthetics, and patient satisfaction. Most frequently reported criteria for success at the implant level were mobility, pain, radiolucency, and peri-implant bone loss (> 1.5 mm), and for success at the peri-implant soft-tissue level, suppuration, and bleeding. The criteria for success at the prosthetic level were the occurrence of technical complications/prosthetic maintenance, adequate function, and esthetics during the five-year period. The criteria at patient satisfaction level were discomfort and paresthesia, satisfaction with appearance, and ability to chew/taste. Success in implant dentistry should ideally evaluate a long-term primary outcome of an implant-prosthetic complex as a whole. KEY WORDS: success, survival, criteria, dental implants, implant complications, dental prostheses. DOI: / Received July 7, 2011; Last revision October 28, 2011; Accepted November 2, 2011 International & American Associations for Dental Research Introduction The commonly accepted criteria for the assessment of implant success were proposed by Albrektsson and colleagues (Albrektsson ), to identify clinical evidence of successful osseointegration and survival of implants. Over the past three decades, implant success has been assessed by survival rates, continuous prosthesis stability, radiographic bone loss, and absence of infection in the peri-implant soft tissues (Albrektsson ; Smith and Zarb, 1989; ; Albrektsson and Zarb, 1998; Misch et al., 2008; Annibali et al., ). Since then, new parameters have been introduced to assess success in the achieving of lifelike implant restorations. These include health status and natural-looking peri-implant soft tissues, as well as prosthodontic parameters, esthetics, and patient satisfaction. However, osseointegration remains the predominant parameter in implant dentistry. It seems logical that the current definition of success criteria should be comprehensive, to include these additional factors (Furhauser et al., 2005; Meijer et al., 2005; Annibali et al., ; Belser et al., ). There is still a lack of homogeneity in the dental literature on reporting complications at both implant and prosthetic levels. A previous systematic review has shown that as much as 38.7% of all implant-supported fixed partial dentures (FPD) for partially edentulous patients had some type of complication during the observation period of 5 yrs (Pjetursson et al., ). This finding highlights the importance of including prosthesis success in analyses of the overall success of dental implants. The aim of this systematic review was to examine the most frequently used criteria to define treatment success in implant dentistry. Materials & Methods Search Strategy An electronic search in the MEDLINE/PubMED database was performed for studies published in English from January 1980 until October The search strategy included the following key word combinations: success criteria AND implant, success rates AND implant, survival rates AND implant, and outcomes AND implant dentistry. The electronic search was supplemented by a manual search of the bibliographies of all articles and related reviews that were selected for full-text reading. Reference manager software (Endnotes, Thomson Reuters, New York, NY, USA) was used to sort selected references and to discard duplicates. 1

2 2 Papaspyridakos et al. J Dent Res X(X) XXXX The following inclusion criteria were used to conduct the studies selection: randomized controlled clinical trials (RCT) and prospective studies with minimum five-year follow-up, studies reporting on roughened surface implants, studies with at least 10 patients, and studies reporting on success/survival criteria used to assess treatment outcomes. Titles and abstracts were initially screened for inclusion by two independent and calibrated reviewers. All titles and abstracts selected by the two reviewers were individually discussed before inclusion for full-text reading. The full-text reading of related publications and data extraction were carried out independently by the two reviewers. In cases where information was not clear, the authors of a given study were contacted via to clarify the issue. Outcome Variables The primary outcome variable was determined by the success rate as presented in the selected articles. To ensure the homogeneity of the result, we then grouped studies according to four well-differentiated clinical situations: implant fixed complete dental prostheses (FCDP), implant overdentures (IOD), implant fixed partial dentures (FPD), and implant single crowns (SC). Secondary outcome variables were the number of parameters used to define success, such as implant fixtures, peri-implant soft tissue, prosthesis, and patient s subjective evaluation. Assessment of Study Quality Following the selection of eligible papers on the basis of inclusion and exclusion criteria, studies were rated on their quality. Specific study-design-related information such as randomization (if applicable), patient and site characteristics, patient selection, intervention, evaluation method, outcome, and follow-up was individually assessed for all included publications. The risk of bias was defined as Low, Medium, or High. To reduce the risk of bias as much as possible, we excluded studies showing High risk of bias. Statistical Analysis Given the heterogeneity among the criteria used to define treatment outcomes, data were analyzed from a descriptive point of view. Inter-reviewer agreement was determined with the use of Cohen s kappa K-statistics. Results The electronic search in the MEDLINE/PubMED database for studies published from January 1980 until October 2010 according to the key words success criteria AND implant, success rates AND implant, survival rates AND implant, and outcomes AND implant dentistry yielded 1524 hits after duplicate references were discarded. The subsequent search at the title level yielded 925 titles (k-score = 0.7) and further at the abstract level identified 402 abstracts (k-score = 0.7). The abstract investigation revealed 258 articles for full-text reading (k-score = 0.85). Excluded Studies Out of the 258 studies selected for full-text reading, 233 were excluded. The studies were excluded when the follow-up period was less than 5 yrs, if a machined implant surface was used, if fewer than 10 patients were included in the study, and if a detailed report on success criteria used for assessment was missing. In addition, multiple publications on the same cohort of patients were also excluded; only the most longitudinal was included. Only RCTs and prospective studies were considered, since they represent the highest level of evidence. The rationale for excluding machined surface implants was that predominantly roughened surface implants are used currently. Study Characteristics/Included Studies The electronic and manual search yielded 2 randomized clinical trials and 23 prospective studies that satisfied the inclusion criteria and were analyzed. In total, 25 publications fulfilled the inclusion criteria and were suitable for analysis. Some of the included articles had mixed data reporting on more than one type of prosthesis (Table 1). Of these 25 publications, only 2 had a low risk of bias, 8 articles reported on implant fixed complete dental prostheses (FCDP), 7 articles on implant overdentures (IOD), 12 articles on implant fixed partial dentures (FPD), and 14 articles on implant single crowns (SC) ( ; Deporter et al., 1999; Behneke et al., ; Weber et al., ; Gotfredsen and Karlsson, 2001; Mericske-Stern et al., 2001; Ferrigno et al., 2002; Chiapasco and Gatti, 2003; Astrand et al., ; Gotfredsen, ; Romeo et al.,, ; Zinsli et al., ; Bornstein et al., 2005; Rasmusson et al., 2005; Wennstrom et al., 2005; Blanes et al., ; Glauser et al., ; Fischer et al., 2008; Roccuzzo et al., 2008; Al Fadda et al., ; Degidi et al., ; Gallucci et al., a; Ma et al., 2010; Payer et al., 2010). The four most frequently used parameters were related to implant fixtures, peri-implant soft tissue, prosthesis, and patient s subjective evaluation (Table 2). The percentage of clinical studies reporting on each of these parameters for success in implant dentistry is shown in Table 3. The most frequently reported criteria for success at the implant level were mobility, pain, radiolucency, and peri-implant bone loss (> 1.5 mm); those for peri-implant soft-tissue level were suppuration, bleeding, and probing pocket depth. The criteria used to assess success at the prosthetic level were the occurrence of technical complications/prosthetic maintenance, adequate function, and esthetics during the five-year period. The criteria reported to assess patient satisfaction level were discomfort, satisfaction with appearance, and ability to function and chew. As shown in Table 4, the reported success rate consistently decreased when the number of parameters included for the assessment of success was increased. In the first group of

3 J Dent Res X(X) XXXX Success Criteria in Implant Dentistry 3 Table 1. Selected Classified according to Their Implant Prosthetic Design Study Study Design Patients/ Implants Risk of Bias Follow- up, yrs Parameters Criteria Success/Survival Rate Implant fixed complete dental prostheses (FCDP) for edentulous patients Gallucci et al., Prospective 45/237 M 5 4 Self-defined criteria 86.7% Degidi et al., Prospective 38/284 M 5 3 Based on Albrektsson 100% for implants; Fischer et al., 2008 RCT 24/139 L 5 3 Self-defined criteria 95.2% for implants; Rasmusson et al., 2005 Prospective 36/199 M 10 1 Self-defined criteria 96.9% for implants; Romeo et al., Prospective 255/759 M 1.3~7 4 Based on Albrektsson 63.8% for prostheses & Buser et al., Astrand et al., Prospective 66/371 M 5 3 Based on Albrektsson 96.3% Ferrigno et al., 2002 Prospective 233/1286 M Up to 10 yrs 3 Based on 95% for 5 yrs; 92.7% for 10 yrs Prospective 1003/2359 M Up to 8 yrs 3 Based on Implant overdentures (IOD) for edentulous patients Ma et al., 2010 RCT 79/158 H 10 2 Based on Albrektsson 85.9% for 5 yrs; 74.5% for 10 yrs Al Fadda et al., Prospective 77/178 M 5 3 Based on Albrektsson & Zarb, % Romeo et al., Prospective 255/759 M 1.3~7 4 Based on Albrektsson & Buser et al., 63.8% for prostheses Zinsli et al., Prospective 149/298 M 10 1 Based on 98.7% Chiapasco and Prospective 82/328 M 3~8 (mean: 2 Based on Albrektsson 88.2% Gatti, ) Deporter et al., Prospective 46/134 M 5~6 3 Based on Albrektsson 83.3% for 5 yrs 1999 Prospective 1003/2359 Up to 8 yrs 3 Based on Implant Fixed Partial Dentures (FPD) for partially edentulous patients Payer et al., Prospective 24/40 M 5 1 Self-defined criteria 92.5% 2010 Romeo et al., Prospective 45/116 M Self-defined criteria 90.5% for implants; 57.7% for prostheses Degidi et al., Prospective 72/219 M 5 3 Based on Albrektsson 99.4% for implants, Blanes et al., Prospective 83/192 M 5~10 (mean: 1 Based on 97.9% 6) Glauser et al., Prospective 38/102 M 5 3 Based on Albrektsson 97.1% Bornstein et al., 2005 Prospective 51/104 M 5 3 Based on 99% Romeo et al., Zinsli et al., Gotfredsen and Karlsson, 2001 Weber et al., Prospective 255/759 M 1.3~7 4 Self-defined criteria 63.8% for prostheses Prospective 149/298 M 10 2 Based on 98.7% Prospective 40/117 M 5 2 Self-defined criteria 97.6% Prospective 46/112 M 5 2 Self-defined criteria 99.1% (continued)

4 4 Papaspyridakos et al. J Dent Res X(X) XXXX Table 1. (Continued) Study Study Design Patients/ Implants Risk of Bias Follow- up, yrs Parameters Criteria Success/Survival Rate Behneke et al., Prospective 55/114 M 5 3 Self-defined criteria 89% Prospective 1003/2359 M Up to 8 yrs 3 Based on Implant single crowns (SC) for partially edentulous patients missing single teeth Payer et al., Prospective 24/40 M 5 1 Self-defined criteria 92.5% 2010 Degidi et al., Prospective 45/45 M 5 3 Based on Albrektsson 100% for implants; Roccuzzo et Prospective 27/106 M 5 2 Self-defined criteria 100% al., 2008 Blanes et al., Prospective 83/192 M 5~10 (mean: 1 Based on 97.9% 6) Glauser et al., Prospective 38/102 M 5 3 Based on Albrektsson 97.1% Bornstein et al., Prospective 51/104 M 5 3 Based on 99% 2005 Wennstrom et Prospective 36/40 M 5 2 Self-defined criteria 97.7% al., 2005 Gotfredsen, Prospective 20/20 M 5 2 Self-defined criteria 100% for implants; 96% for prostheses Romeo et al., Prospective 255/759 M 1.3~7 4 Based on Albrektsson 75.6% for prostheses & Buser et al., Zinsli et al., Prospective 149/298 M 10 2 Based on 98.7% Mericske-Stern Prospective 72/109 M 1~9 (mean: 2 Self-defined criteria 99.1% et al., ) Weber et al., Prospective 46/112 M 5 2 Self-defined criteria 99.1% Behneke et al., Prospective 55/114 M 5 3 Self-defined criteria 89% Prospective 1003/2359 M Up to 8 years 3 Based on FCDP, implant fixed complete dental prostheses; IOD, implant overdentures; RCT, randomized clinical trial; FPD, fixed partial denture; SC, single crown; L, low risk of bias; M, medium risk of bias. completely edentulous patients with implant FCDPs, for every additional parameter included in the success criteria, the success rates dropped by an average of 7.2%. In the group of completely edentulous patients restored with IODs, the success rates dropped by an average of 6.9% for every parameter added. For the group of partially edentulous patients, success rates decreased by an average of 9.4% for every additional parameter included. Finally, in the group of patients restored with implant SCs, the success rates dropped by an average of 4.1% for every parameter added. Discussion A clinical trial will usually define or specify a primary endpoint as a measure of success of the therapy investigated. This is not common in the dental implant literature, where survival/success rates of single parameters are often presented. Marginal bone levels, measured with periapical radiographs, are a commonly used parameter for the assessment of implant success. Several implant systems with a roughened surface demonstrate progressive crestal bone loss and consequently ongoing loss of implants even after 5 or more yrs. However, the introduction of new implant surfaces and prosthetic connections has added new dimensions to implant dentistry. Roughened-surface implants have proved to have a higher survival rate than machined-surface implants (Lambert et al., ). Platform switching and inward shifting of the connection microgap have been shown to reduce crestal bone remodeling (Prosper et al., ; Trammell et al., ). Thus, peri-implant bone remodeling, universally accepted as being up to 2 mm during the first year of function, followed by a maximum of 0.2 mm annually thereafter, may now be subject to question as a reliable success criterion. These examples of single parameters used as success criteria could be defined as surrogate endpoints, often to compensate for the lack of well-defined

5 J Dent Res X(X) XXXX Success Criteria in Implant Dentistry 5 Table 2. Success Criteria as Described in All Selected Success Criteria FCDP (8 articles) FPD (12 articles) IOD (7 articles) SC (14 articles) Implant level Pain Bone loss at 1st year < 1.5 mm Annual bone loss < 0.2 mm thereafter Radiolucency Mobility Infection Peri-implant soft tissue Probing depth > 3 mm Suppuration Bleeding Swelling Plaque Index Width of keratinized mucosa > 1.5 mm Recession Prosthetic level Minor complications (chairside approach) Major complications/failures Esthetics Functional Patient satisfaction Discomfort/paresthesia Satisfaction with appearance Ability to chew Ability to taste General satisfaction Table 3. Percentage of Reporting on Each of the Four Main Categories Identified as Parameters for Success Parameters FCDP (8 articles) FPD (12 articles) IOD (7 articles) SC (14 articles) Implant level Peri-implant soft-tissue level Prosthetic level Patient satisfaction level FCDP, implant fixed complete dental prosthesis; FPD, implant fixed partial denture; IOD, implant overdenture; SC, implant single crown. primary outcomes. For instance, bone loss or any other finding alone within an implant prosthetic rehabilitation should not be considered as the primary outcome when success is assessed. In contrast, it appears inaccurate to assess several outcomes separately when the implant-prosthetic complex as a whole is necessary for successful oral rehabilitation. Instead, current advances in contemporary oral implantology, coupled with patients high treatment expectations, underline the necessity for more comprehensive definition of success criteria for implant/prosthodontics procedures. It seems evident that implant survival rates per se, without consideration of a clinical outcome that reports on the implant/prosthodontic complex as a whole rather than its individual aspects, would no longer suffice to assess the clinical efficiency of current implant prosthetic methodologies. Gallucci et al. proposed success criteria for implant FCDPs based on implant, peri-implant tissues, prosthodontic, and subjective parameters (Gallucci et al., a). They reported a 95.5% survival rate vs. an 86.7% success rate when their proposed success criteria were applied. FCDPs were deemed as successful when a total of four or fewer complications (mild or moderate severity) were encountered, and these could be addressed chair-side in a single visit. Additionally, patient satisfaction with overall treatment was rated good or excellent for the treatment outcome to be considered successful. Well-defined criteria should ideally be used for reporting and assessing outcomes as well as biological and technical complications (Eckert et al., 2005). A systematic review showed that as much as 38.7% of all implant-supported FPDs for partially edentulous patients had some type of complication during an observation period of at least 5 yrs (Pjetursson et al., ). This highlights the importance of including prosthetic outcomes in analyses of the overall success of implant dentistry. In this systematic review, the four most frequently used parameters for measuring outcomes with dental implants were

6 6 Papaspyridakos et al. J Dent Res X(X) XXXX Table 4. According to the Number of Parameters Included for Assessment FCDP (8 articles) FPD (12 articles) IOD (7 articles) SC (14 articles) # of Parameters Included for Assessment of 1 8 (100%) 97.3%-100% 12 (100%) 92.5%-100% 7 (100%) 63.8%-98.7% 14 (100%) 75.6%-100% 2 None None 3 (25%) 98.7%-100% 2 (29%) 74.5%-88.2% 6 (43%) 96%-99.1% 3 5 (62.5%) 92.7%-100% 5 (42%) 95.3%-98.8% 3 (43%) 83.3%-98% 5 (36%) 89%-100% 4 2 (25%) 63.8%-86.7% 2 (17%) 57.7%-63.8% 1 (14%) 63.8% 1 (7%) 75.6% related to the implant level, peri-implant soft-tissue level, prosthesis level, and the patient s subjective assessment. The reported success rate consistently decreased when the number of parameters included for assessment of success was increased (Table 4). When an additional success parameter was included in the outcome assessment, then the success rate dropped significantly for all four groups of patients. This is of paramount importance when it comes to selecting a treatment plan. Only a few of the currently used protocols have been assessed with comprehensive success criteria and therefore can be considered to have some degree of scientific or clinical validation (Gallucci et al., b). The four most frequently used parameters for assessing success were identified through the full-text reading and were related to implant level, peri-implant soft tissue, prosthesis, and patient s subjective evaluation. These parameters were the most commonly used in the dental literature that was systematically reviewed. An attempt to list these parameters in the order of importance seems difficult, because successful osseointegration as the baseline and milestone of implant therapy cannot be directly compared with patient satisfaction, which is equally important. Another issue that needs to be addressed is a patient-centered outcome and patient satisfaction with prosthesis. A classification of treatment outcomes with dental implant therapy has been previously proposed (Guckes et al., 1996). This classification, in addition to implant longevity/survival, included patientcentered aspects of the treatment outcome, namely, physiological, psychological, and economic impact. For the assessment of esthetic outcomes, objective criteria like Pink Esthetic Scores (PES) and White Esthetic Scores (WES) have been proposed, but these do not reflect the patient s subjective opinion about the outcome of therapy (Furhauser et al., 2005; Belser et al., ). The clinician s objective evaluation and the patient s subjective perception of a successful outcome often do not agree (Vilhjalmsson et al., 2011). According to Levi et al., patient satisfaction with overall treatment should be rated good or excellent for the treatment outcome to be considered successful (Levi et al., 2003). Esthetics is also very important in dentistry, underscoring the necessity for the inclusion of more factors in the success criteria assessment for implant prostheses. The focus has shifted from implant survival to the creation of lifelike implant restorations with natural-looking peri-implant soft tissues. Through the years, multiple modifications have been made to include other parameters such as esthetics as a method to measure success. Future Directions For Research Clinical studies included in the systematic review mainly used implant and peri-implant soft-tissue parameters for measuring success, while the prosthesis assessment and patient satisfaction parameters were least used. Success in implant dentistry should ideally evaluate a long-term primary outcome of an implant-prosthetic complex as a whole. ACKNOWLEDGMENTS This study was supported by the Department of Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine. 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