Long-term Survival of Straumann Dental Implants with TPS Surfaces: A Retrospective Study with a Follow-up of 12 to 23 Years Stephan T. Becker, MD, DMD, PhD;*1 Benedicta E. Beck-Broichsitter, MD, DMD;†1 Christian M. Rossmann, MD, DMD;* Eleonore Behrens, DMD;* Arne Jochens, PhD;‡ Jörg Wiltfang, MD, DMD, PhD§
ABSTRACT Purpose: The aim of this study was to evaluate the long-term dental implant survival rates of Straumann dental implants in a university hospital environment over 12 to 23 years. Materials and Methods: A total of 388 Straumann dental implants with titanium-sprayed surfaces (TPS) were inserted in 92 patients between 1988 and 1999 in the Department of Oral and Maxillofacial Surgery of the University Hospital SchleswigHolstein in Kiel, and they were reevaluated with standardized clinical and radiological exams. Kaplan–Meier analyses were performed for individual factors. Cox proportional hazard regression analysis was used to detect the factors influencing long-term implant failure. Results: The long-term implant survival rate was 88.03% after an observation time of 12.2 to 23.5 years. Cox regression revealed statistically significant influences of the International Team for Implantology (ITI) implantation type (p = .00354) and tobacco smoking (p = .01264) on implant failure. A proportion 82.8% of the patients with implant losses had a medical history of periodontitis. Peri-implantitis was diagnosed in 9.7% of the remaining implants in the long-term survey. Conclusions: This study emphasized the long-term rehabilitation capabilities of Straumann dental implants in complex cases. The survival rates after several years constitute important information for patients, as well as for clinicians, in deciding about different concepts of tooth replacement. Patient-related and technical factors – determined before implant placement – could help to predict the risk of implant loss. KEY WORDS: implantation type, implant diameter, peri-implantatitis, periodontitis, Straumann dental implants, survival, tobacco
INTRODUCTION
*Research assistant, Department of Oral and Maxillofacial Surgery, Schleswig-Holstein University Hospital, Kiel, Germany; †research assistant, Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; ‡Statistician, Institute of Medical Informatics and Statistics, SchleswigHolstein University Hospital, Kiel, Germany; §head of department, Department of Oral and Maxillofacial Surgery, Schleswig-Holstein University Hospital, Kiel, Germany
After Brånemark discovered the process of osseointegration and placed the first dental implant 45 years ago,1,2 a milestone was set for successful oral rehabilitation of the edentulous or partially edentulous patient.3,4 At the same time, dental implants are an increasingly viable alternative to conventional prosthodontic treatment options, with the latter supported by evidence-based data of up to 20 years.5–9 Regarding comparable long-term data concerning the outcomes of dental implants, several recently published articles have reported approximate 10-year survival rates between 90% and 98.8%,10–13 and another article even referred to survival rates of 100% after 12 years14 and
Corresponding Author: Dr. Benedicta E. Beck-Broichsitter, Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Campus Forschung Gebäude N27, Hamburg 20246, Germany; e-mail: [email protected] The authors negate any conflict of interest. 1 Equal contribution. © 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12334
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97.7% to 100% after 16 years.15 The number of articles published with 20-year perspectives remains relatively limited, but published articles have reported survival rates at consistently high levels of 89.5% to 99.2%.16–18 A dental implant fails in the absence of osseointegration during the initial stage of healing, whereas late implant failure occurs in the already healed and functionally loaded dental implant, the mechanical stability of which is compromised due to a continuous decrease in the osseointegrated implant surface. While peri-implant mucositis only affects the soft tissue surrounding the implant, and it remains reversible, periimplantitis is accompanied by additional vertical bone loss at the implant shoulder, which is believed not to be reversible.19 It has been estimated, that within a few years after implantation and initial bone remodeling, 1.4% to 6.6% of the inserted implants will develop peri-implantitis.10– 12,20 The risk of peri-implantitis increases with smoking and poor oral hygiene.21 With preexisting periodontitis, the incidence rate is four to five times higher.22 Further occurrences can arise in cases of osteoporosis and diabetes. The aim of this unicentric study was to evaluate systematically the long-term outcomes of Straumann dental implants with titanium-sprayed surfaces (TPS) in all indication classes, particularly in cases with severe atrophy of the alveolar ridge, considering implantations performed from 1988 to 1999 in the setting of the University Hospital of Kiel. MATERIALS AND METHODS Patient Recruitment Medical records were collected of patients who underwent insertion of Straumann dental implants in the Department of Oral and Maxillofacial Surgery of the Schleswig-Holstein University Hospital in Kiel from 1988 to 1999. Thereby, a total of 723 dental implants inserted in 155 patients were identified. These implants were primarily included, and the patients were contacted via postal mail or telephone. Ninety-two patients (59.35%; 56 women, 36 men) agreed to participate in the study. In these remaining 92 patients, 388 Straumann dental implants were inserted between 1988 and 1999 (average observation time 14 years 1 1.9 years). The subjects were partially and fully edentulous patients. The
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mean age at the follow-up examination was 65.9 years (standard deviation: 111.9 years). Medical Record Assessment Implantation types were defined according to the third ITI Consensus Conference, based on the time between tooth extraction and implantation23: Type I: Immediate implant placement in an extraction socket Type II: Early implant placement after 4 to 8 weeks after tooth removal Type III: Early implant placement after 12 to 16 weeks after tooth removal Type IV: Late implant placement more than 6 months after extraction Vertical and horizontal bone augmentation procedures (e.g., block augementation, sinus floor elevation) were further classified depending on the donor site and the origin of the augmentation material (autologous/ xenogenic). The length, diameter, and position of the implants were previously extracted from surgical reports in the medical records, as were in-house-treated implant failures and consecutive explantation procedures. The type of prosthodontic rehabilitation was classified into fixed prosthodontics (single crown, bridgework) and overdenture prostheses. Implant Therapy Three different surgeons in the department inserted all of the implants examined in this study, according to the manufacturers’ surgical recommendations. The implants were without exception solid screws with TPS. The patients received systemic antibiotics from the day of implant placement and an antibacterial mouth rinse from 7 to 10 days. Sutures were removed 7 to 10 days after implant insertion. All of the patients were instructed regarding how to maintain appropriate oral hygiene directly after implant insertion, and they were reinstructed after an uncovering procedure regarding how to proceed after prosthodontics rehabilitation. Clinical Assessment The patients were specifically asked about systemic diseases (e.g., diabetes mellitus), nicotine abuse, and a history of previously diagnosed periodontitis.
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One independent oral and maxillofacial surgeon (C.M.R.) performed the clinical follow-up examinations in the recalled patients. Full periodontal status was recorded, including probing pocket depths and recessions on four sites of each implant and the remaining teeth. Distances were measured to the nearest millimeter. To determine the status of oral hygiene objectively, bleeding on probing (BOP) was obtained, as well as pus suppuration while probing and signs of gingivitis. Marginal bone levels were measured on the distal and mesial sites of the implants on panoramic radiographs and were calculated based upon the known implant length, and thereby considering the magnification factors on the radiographs. Peri-implantitis was defined according to Ong and colleagues, based on peri-implant probing depth 35 mm, in addition to a positive BOP and/or suppuration and radiographic bone loss 32.5 mm or 33 exposed threads.24 Statistical Assessment R software was employed for the statistical data analyses.25 Descriptive statistics are reported for single factors. Overall implant survival was displayed in Kaplan–Meier plots, including 95% confidence intervals. To identify factors influencing implant survival time, a Cox proportional hazard regression model was applied.
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TABLE 1 Distribution Implants in-situ Position
1
2
3
4
5
6
7
Total
%
Maxilla Mandible
13 0
18 16
7 34
35 33
33 27
32 40
21 19
159 169
48.5 51.5
long-term evaluation and Cox regression analysis for the evaluation of risk factors. Considered alone, the longterm survival rate was 88.03%. Twenty-one implants (35% of all removed implants) were lost within 3 to 6 months, and 28 (46.7% of all removed implants) implants had to be removed within the first 12 months. At the reevaluation, 18.5% (61 implants) of the implants showed radiographic bone loss of 32.5 mm and 9.7% (32 implants) of all in situ implants showed clinical signs of periimplantitis, according to the criteria by Ong and colleagues.24 The distribution of implant loss classified by the presence of peri-implantitis is displayed in Table 3. Regarding the study cohort of 388 implants, a total of 245 (63.14%) were placed in patients with previously diagnosed periodontitis. Among these cases, the rate of implant loss was much higher (17 patients, 18.5%) compared with the patients without periodontitis (7 patients, 7.6%; see Table 4).
RESULTS Descriptive Statistical Evaluation All Implants. Among the 155 patients with 723 implants who were identified first and were contacted for follow-up examinations, 92 patients (59.35%; 56 women, 36 men) agreed to participate in the study, 29 patients (18.71%) refused for their health or personal reasons, 28 patients (18.07%) could not be contacted via postal mail or telephone, and 6 patients (3.87%) were deceased. In the remaining cohort (92 patients, 388 implants), 60 implants (15.5%) in 24 patients were lost at the time of clinical examination – 1 day to 15.5 years after implant insertion. Tables 1 and 2 display the distribution of remaining and lost implants, respectively, in the study cohort. The overall implant survival rate was 84.5% after an average observation time of 14 years (11.9 years). Twelve implants (20% of all of the removed implants) were categorized as early losses within 90 days after implantation and were therefore excluded from
Collective Description Of a total of 388 evaluated implants, 197 (50.8%) were placed in the maxilla and 191 (49.2%) in the mandible. A minimum of one and a maximum of 13 implants were placed per patient (median = 6). Regarding prosthetic rehabilitation, 58.5% of the implants were supplied with fixed restorations, while 84% of this proportion were single crowns, and 16% were bridgework. Of all of the implants, 41.5% served as removable prostheses. Augmentation procedures were performed in 55.4% of all of the implants, including sinus floor
TABLE 2 Distribution Implant Losses Position
1
2
3
4
5
6
7
Total
%
Maxilla Mandible
0 0
5 4
2 4
4 6
2 3
11 7
6 6
30 30
50 50
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TABLE 3 Four Field Matrix: Distribution of Peri-implantitis and Implant Loss among the Patients Peri-implantitis Periimplantitis + − Absolute
Loss + Loss − Absolute %
7 8 15 16.3
17 60 77 83.7
24 68 92
%
26.09 76.09 100
elevations, applying a mix of particulated autologous bone graft and bone replacement materials, as well as vertical and horizontal augmentations, using block grafts of autologous bone (e.g., iliac crest, linea oblique). The overall majority of bone grafts were harvested extraorally (68.8%), whereas in 6.8%, intraoral bone grafts were applied. Bone replacement materials were used in 25.6% of all of the implants with augmentation procedure (Figure 1). The majority of the implants (70.4%) were placed more than 6 months after tooth extraction and thus were Type IV implantations, according to the ITI Consensus. The remainder were immediate placements (Type I; 3.1%), early placements (Type II; 7.2%); and early placements with partial bone healing (Type III; 19.3%), as shown in Figure 2. Figure 3 provides the implant diameters and length distributions in this study, showing a preference for length of 12 or 14 mm and a preferred diameter of approximately 4 mm. Regarding peri-implant health, nearly all of the implants (97.6%) were well osseointegrated with no recordable movement. Grade I movements were recorded in three (0.9%) and grade II in five (1.5%) implants. BOP was negative in the majority (79.6%) of probed implants. Of all implants, 13.68% had a periimplant probing depth 35 mm.
Figure 1 Augmentation procedures were applied in the majority of patients in this study cohort. Extraoral bone grafting was further preferred to augment the jaw bone, followed by the use of bone replacement materials and intraorally harvested bone.
Nicotine abuse was determined in 21 (22.83%) of 92 patients. Twelve of these 21 (57.14%) patients, compared with 12 of 71 (16.9%) nonsmoking patients, lost at least one implant during the observation time (Table 5). One third of the patients who lost an implant had combined risk factors (nicotine abuse and periodontitis). Of all of the patients, 7.8% suffered from diabetes mellitus, but none of these lost implants. Cox Regression and Kaplan–Meier Analyses For regression analyses, a total of 383 implants were included, comprising 57 events (implant losses). A total of five observations had to be deleted due to incomplete data sets. Model selection proceeded from a Cox regression model that included sex, number of implants per patient, implantation site (anterior region: 13 to 23, 33 to 43; posterior region 14 to 17, 24 to 27, 34 to 37, and 44 to 47), implant diameter and implant length according to the range of distributions displayed in Figure 3, time after tooth loss (months), implantation type (according to the Consensus Conference), type of prosthesis (removable/fixed), augmentation (yes/no), cigarette smoking (yes/no), previous periodontitis (yes/no), and
TABLE 4 Four Field Matrix: Distribution of Periodontitis and Implant Loss among the Patients
Loss + Loss − Absolute %
Periodontitis +
Periodontitis −
17 21 38 41.30
7 47 54 58.70
Absolute
%
24 68 92
26.09 73.91 100
Figure 2 ITI implantation types in the study cohort.
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The exponent of the regression coefficient for implantation, which could be interpreted as a hazard ratio, was 3.1643. This finding indicated that, all other things being equal, implantation type II was estimated to have 3.2 times as high a failure rate as Type I, Type III had a 3.2 times as high a failure rate as Type II, and Type IV had a 3.2 times as high a failure rate as Type III. To evaluate the influence of augmentation procedure and implantation type on implant survival (data not shown), Fisher’s exact test was applied but there was no statistically significant correlation (p = .084). DISCUSSION
Figure 3 Distributions of implant diameters and implant lengths of all of the patients.
age (years) at insertion as independent variables. Here, implantation type was coded as a numerical variable according to the ITI consensus because we expected that these numbers correspond roughly to equidistant levels of risk. After stepwise backward selection, two variables were identified, which significantly influenced implant survival time (Table 6): cigarette smoking (p = .001264) and ITI implantation type (p = .00354). Figure 4 displays Kaplan–Meier estimates of implant survival, accounting for the previously identified influence factors. In particular, the figure shows long-term implant survival with 95% confidence intervals (Figure 4A), as well as survival according to ITI implantation type (Figure 4B).
TABLE 5 Four Field Matrix: Distribution of Nicotine Smoking and Implant Loss among the Patients
Loss + Loss − Absolute %
Nicotine +
Nicotine −
Absolute
%
12 9 15 22.83
12 59 77 77.17
24 68 92
26.09 76.09 100
Patients and clinicians must decide every day between prosthodontic restoration methods and implantsupported rehabilitation alternatives. Here, long-term data covering more than 10 years helped in the evaluation of treatment alternatives. In our study, the Kaplan– Meier estimate of the long-term survival rate was 88.03% after 12.2 to 23.5 years after implant insertion. The deviation of this survival rate, compared with the studies mentioned above, could depend on the specialization of the University Department of Oral and Maxillofacial Surgery meeting the specific requirements for the treatment of this special patient cohort. Another possible reason for the deviation of percentages in reports on long-term implant survival is that the majority of patients receiving implant treatment are of advanced age. In our study, nearly 60% of the patients in the original cohort agreed to participate in this follow-up. The survival rate gathered from this patient cohort might not reflect true implant survival. It must be estimated that, not considering deceased patients who might not have influenced long-term survival and who represented only 4% of all patients, information about implant survival and implant function was not available in the remaining 36% of the patient cohort. The data lacking from these patients might have led to a distortion of the results either way because these patients likely visited their dentists for check-ups and alleged implant losses might have been treated elsewhere. Therefore, it cannot be ruled out that the true long-term survival rate might have been lower than we reported in this study due to these dropped out patients. Another reason for the deviation when comparing the survival rates with the previously mentioned longterm studies might be the number of augmentation procedures in this cohort. In particular, the proportion of
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TABLE 6 Cox Regression Analyses
Nicotine ITI implantation type
Regression Coefficient
Exp (Regression Coefficient)
Lower 95% Confidence Limit
Upper 95% Confidence Limit
p Value
0.765 1.1277
2.1489 3.1643
1.178 1.459
3.920 6.863
.01264 .00354
extraorally harvested autologous bone indicated that the majority of the patients suffered from severe alveolar ridge atrophy as defined in the ITI implantation Type IV. Therefore, complex augmentation procedures were needed to restore the alveolar ridge, resulting in a progressively increased likelihood of complications, although bone augmentation procedures themselves were not identified as an influential factor in this study, whereas the ITI implantation type was identified as significantly influencing the long-term implant survival in Cox regression analysis. Comparing immediate and delayed implantation at maxillary molar sites, the 1-year success rate of delayed implantation was estimated at 93.2% of 123 cases, with exclusion of patients who smoke more than 10 cigarettes per day.26 In another multicenter study,27 a total of 143 patients with a total of 264 implants were prospectively evaluated, comparing immediate and delayed implant placement. The survival rate after 5 years was 92.4% for maxillary and 94.7% for mandibular inserted implants.
Regarding the implantation type, no difference in survival rate could be detected.27 In a systematic review performed by Clementini and colleagues, the implant survival and treatment success rates were evaluated after vertical and horizontal-guided bone regeneration. During follow-up periods of 1 to 5 years, implant survival ranged from 93.75% to 100%.28 In another study, the 1-year survival of delayed and immediate implantation with bone block grafts was evaluated, and resulting in a 100% survival rate for immediate and 96.9% for delayed implants.29 Here, the implant surface itself must be considered to be a decisive factor in the survival of dental implants, allowing for rapid healing directly after implant insertion and therefore subsequently stable osseointegration. In a study comparing the outcomes of AstraTech TiOblast and Brånemark implants with turned surfaces over a 12- to 15-year period, there was no significant difference found for implant survival or the prevalence of peri-implantitis, at 5% and 6%, respectively.30
Figure 4 Kaplan–Meier analyses including all of the implants with 95% confidence intervals (A), and further distinguished by ITI implantation type (B).
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Another study, also comparing AstraTech TiOblast and Brånemark implants with machine-etched surfaces, detected no effect of implant surface or design when assessing the rate of peri-implantitis and implant survival after 13 years, defining periimplantitis as 31 mm bone loss in the first year after implant insertion, in conjunction with BOP with or without suppuration.31 In contrast with these results, in another study, comparing Brånemark implants with turned surfaces against TiUnite surfaces, the mean bone level was significantly different in favor of the TiUnite surfaces, as well as showing significantly longer implant survival after a 10-year follow-up period.32 However, according to the literature, other additional influential factors, such as periodontitis and tobacco smoking, might put the implant survival at risk. Although Cox regression analysis did not reveal periodontitis to be a risk factor for implant loss on a single implant level in this cohort, another long-term study of Straumann dental implants revealed an association between peri-implant disease and periodontitis in 89 patients.33 In this context, particuarly in partially edentulous patients with a history of periodontitis, the periimplant tissue might be colonized by periodontally pathogen bacteria originating from pockets of the neighboring teeth, compared with edentulous patients receiving dental implants.34 A recently published long-term study revealed stable clinical and radiographic results 10 years after implantation of Frialit-2 dental implants in a department of periodontology, but tobacco-smoking patients were previously excluded, and a meticulous check-up examination protocol was followed after implant insertion.35 In our study cohort, cigarette smoking was identified as a risk factor for implant loss. A systematic review by Chambrone and colleagues evaluated the influence of tobacco smoking on implant survival after maxillary sinus augmentation.36 In accordance with our study, smoking was associated with implant failure in eight included studies, but interestingly, a correlation with implant failure could not be proved in this review, when studies were performed in a prospective manner.36 Because the definition of peri-implantitis is tied with the loss of vertical bone height at an implant, radiographs are necessary. In our study, panoramic radiographs were obtained, after implantation as well as during the follow-up examinations, in order to ensure
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comparability and, consequently, valid results if the length of the implant is known, and the measurements are close to the implant itself.37 However, due to the nature of the technique for panoramic radiography, the local resolution remains inferior compared with intraorally obtained radiographs.38 CONCLUSION This study emphasized that dental implants were capable of predictable long-term rehabilitation in the majority of even complex patient cases in the Department of Oral and Maxillofacial Surgery. An individual risk profile of patient-related factors and technical aspects remains important for long-term implant survival and should be considered with and communicated to the patient before implantation. REFERENCES 1. Branemark PI, Adell R, Albrektsson T, Lekholm U, Lundkvist S, Rockler B. Osseointegrated titanium fixtures in the treatment of edentulousness. Biomaterials 1983; 4:25– 28. 2. Branemark PI, Adell R, Breine U, Hansson BO, Lindstrom J, Ohlsson A. Intra-osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg 1969; 3:81–100. 3. Branemark PI, Hansson BO, Adell R, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977; 16:1–132. 4. Schroeder A, van der Zypen E, Stich H, Sutter F. The reactions of bone, connective tissue, and epithelium to endosteal implants with titanium-sprayed surfaces. J Maxillofac Surg 1981; 9:15–25. 5. Hammerle CH. Success and failure of fixed bridgework. Periodontol 2000 1994; 4:41–51. 6. Layton DM, Clarke M. A systematic review and metaanalysis of the survival of non-feldspathic porcelain veneers over 5 and 10 years. Int J Prosthodont 2013; 26:111–124. 7. Erpenstein H, Kerschbaum T, Halfin T. Long-term survival of cast-gold inlays in a specialized dental practice. Clin Oral Investig 2001; 5:162–166. 8. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: part 1. Outcome. Int J Prosthodont 2002; 15:439–445. 9. Karlsson S. Failures and length of service in fixed prosthodontics after long-term function. A longitudinal clinical study. Swed Dent J 1989; 13:185–192. 10. Ostman PO, Hellman M, Sennerby L. Ten years later. Results from a prospective single-centre clinical study on 121 oxidized (TiUnite) Branemark implants in 46 patients. Clin Implant Dent Relat Res 2012; 14:852–860.
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11. Fischer K, Stenberg T. Prospective 10-year cohort study based on a randomized controlled trial (RCT) on implant-supported full-arch maxillary prostheses. Part 1: sandblasted and acid-etched implants and mucosal tissue. Clin Implant Dent Relat Res 2012; 14:808–815. 12. Buser D, Janner SF, Wittneben JG, Bragger U, Ramseier CA, Salvi GE. 10-year survival and success rates of 511 titanium implants with a sandblasted and acid-etched surface: a retrospective study in 303 partially edentulous patients. Clin Implant Dent Relat Res 2012; 14:839–851. 13. Wittneben JG, Buser D, Salvi GE, Burgin W, Hicklin S, Bragger U. Complication and failure rates with implantsupported fixed dental prostheses and single crowns: a 10-year retrospective study. Clin Implant Dent Relat Res 2014; 16:356–364. 14. Vroom MG, Sipos P, de Lange GL, et al. Effect of surface topography of screw-shaped titanium implants in humans on clinical and radiographic parameters: a 12-year prospective study. Clin Oral Implants Res 2009; 20:1231– 1239. 15. Jacobs R, Pittayapat P, van Steenberghe D, et al. A splitmouth comparative study up to 16 years of two screwshaped titanium implant systems. J Clin Periodontol 2010; 37:1119–1127. 16. Chappuis V, Buser R, Bragger U, Bornstein MM, Salvi GE, Buser D. Long-term outcomes of dental implants with a titanium plasma-sprayed surface: a 20-year prospective case series study in partially edentulous patients. Clin Implant Dent Relat Res 2013; 15:780–790. 17. Ekelund JA, Lindquist LW, Carlsson GE, Jemt T. Implant treatment in the edentulous mandible: a prospective study on Branemark system implants over more than 20 years. Int J Prosthodont 2003; 16:602–608. 18. Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentulous jaws: a 20-year follow-up. Clin Implant Dent Relat Res 2008; 10:207–217. 19. Botero JE, Gonzalez AM, Mercado RA, Olave G, Contreras A. Subgingival microbiota in peri-implant mucosa lesions and adjacent teeth in partially edentulous patients. J Periodontol 2005; 76:1490–1495. 20. Roos-Jansaker AM, Lindahl C, Renvert H, Renvert S. Nineto fourteen-year follow-up of implant treatment. Part I: implant loss and associations to various factors. J Clin Periodontol 2006; 33:283–289. 21. Wiltfang J, Zernial O, Behrens E, Schlegel A, Warnke PH, Becker ST. Clin Implant Dent Relat Res. 2012 Jun; 14(3):421–427. doi: 10.1111/j.1708-8208.2009.00264.x. Epub 2010 Feb 3. 22. Karoussis IK, Salvi GE, Heitz-Mayfield LJ, Bragger U, Hammerle CH, Lang NP. Long-term implant prognosis in patients with and without a history of chronic periodontitis: a 10-year prospective cohort study of the ITI Dental Implant System. Clin Oral Implants Res 2003; 14:329–339.
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23. Hammerle CH, Chen ST, Wilson TG Jr. Consensus statements and recommended clinical procedures regarding the placement of implants in extraction sockets. Int J Oral Maxillofac Implants 2004; 19(Suppl):26–28. 24. Ong CT, Ivanovski S, Needleman IG, et al. Systematic review of implant outcomes in treated periodontitis subjects. J Clin Periodontol 2008; 35:438–462. 25. Team RDC. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing, 2011. 26. Penarrocha-Oltra D, Demarchi CL, Maestre-Ferrin L, Penarrocha-Diago M. Comparison of immediate and delayed implants in the maxillary molar region: a retrospective study of 123 implants. Int J Oral Maxillofac Implants 2012; 27:604–610. 27. Polizzi G, Grunder U, Goene R, et al. Immediate and delayed implant placement into extraction sockets: a 5-year report. Clin Implant Dent Relat Res 2000; 2:93–99. 28. Clementini M, Morlupi A, Canullo L, Agrestini C, Barlattani A. Success rate of dental implants inserted in horizontal and vertical guided bone regenerated areas: a systematic review. Int J Oral Maxillofac Surg 2012; 41:847– 852. 29. Penarrocha-Diago M, Aloy-Prosper A, Penarrocha-Oltra D, Guirado JL. Localized lateral alveolar ridge augmentation with block bone grafts: simultaneous versus delayed implant placement: a clinical and radiographic retrospective study. Int J Oral Maxillofac Implants 2013; 28:846–853. 30. Ravald N, Dahlgren S, Teiwik A, Grondahl K. Long-term evaluation of Astra Tech and Branemark implants in patients treated with full-arch bridges. Results after 12–15 years. Clin Oral Implants Res 2013; 24:1144–1151. 31. Renvert S, Lindahl C, Rutger Persson G. The incidence of peri-implantitis for two different implant systems over a period of thirteen years. J Clin Periodontol 2012; 39:1191– 1197. 32. Polizzi G, Gualini F, Friberg B. A two-center retrospective analysis of long-term clinical and radiologic data of TiUnite and turned implants placed in the same mouth. Int J Prosthodont 2013; 26:350–358. 33. Karoussis IK, Muller S, Salvi GE, Heitz-Mayfield LJ, Bragger U, Lang NP. Association between periodontal and peri-implant conditions: a 10-year prospective study. Clin Oral Implants Res 2004; 15:1–7. 34. Karbach J, Callaway A, Kwon YD, d’Hoedt B, Al-Nawas B. Comparison of five parameters as risk factors for perimucositis. Int J Oral Maxillofac Implants 2009; 24:491–496. 35. Meyle J, Gersok G, Boedeker RH, Gonzales JR. Long-term analysis of osseointegrated implants in non-smoker patients with a previous history of periodontitis. J Clin Periodontol 2014; 41:504–512. 36. Chambrone L, Preshaw PM, Ferreira JD, Rodrigues JA, Cassoni A, Shibli JA. Effects of tobacco smoking on the sur-
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vival rate of dental implants placed in areas of maxillary sinus floor augmentation: a systematic review. Clin Oral Implants Res. 2014 Apr; 25(4):408–416. doi: 10.1111/ clr.12186. Epub 2013 May 7. 37. Verhoeven JW, Cune MS. [Research methods in dentistry 9. Follow-up of permucosal implants in an edentate mandible
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using panoramic radiography]. Ned Tijdschr Tandheelkd 2005; 112:86–89. 38. Truhlar RS, Morris HF, Ochi S. A review of panoramic radiography and its potential use in implant dentistry. Implant Dent 1993; 2:122–130.
ABSTRACT Purpose: The aim of this study was to evaluate the long-term dental implant survival rates of Straumann dental implants in a university hospital environment over 12 to 23 years. Materials and Methods: A total of 388 Straumann dental implants with titanium-sprayed surfaces (TPS) were inserted in 92 patients between 1988 and 1999 in the Department of Oral and Maxillofacial Surgery of the University Hospital SchleswigHolstein in Kiel, and they were reevaluated with standardized clinical and radiological exams. Kaplan–Meier analyses were performed for individual factors. Cox proportional hazard regression analysis was used to detect the factors influencing long-term implant failure. Results: The long-term implant survival rate was 88.03% after an observation time of 12.2 to 23.5 years. Cox regression revealed statistically significant influences of the International Team for Implantology (ITI) implantation type (p = .00354) and tobacco smoking (p = .01264) on implant failure. A proportion 82.8% of the patients with implant losses had a medical history of periodontitis. Peri-implantitis was diagnosed in 9.7% of the remaining implants in the long-term survey. Conclusions: This study emphasized the long-term rehabilitation capabilities of Straumann dental implants in complex cases. The survival rates after several years constitute important information for patients, as well as for clinicians, in deciding about different concepts of tooth replacement. Patient-related and technical factors – determined before implant placement – could help to predict the risk of implant loss. KEY WORDS: implantation type, implant diameter, peri-implantatitis, periodontitis, Straumann dental implants, survival, tobacco
INTRODUCTION
*Research assistant, Department of Oral and Maxillofacial Surgery, Schleswig-Holstein University Hospital, Kiel, Germany; †research assistant, Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; ‡Statistician, Institute of Medical Informatics and Statistics, SchleswigHolstein University Hospital, Kiel, Germany; §head of department, Department of Oral and Maxillofacial Surgery, Schleswig-Holstein University Hospital, Kiel, Germany
After Brånemark discovered the process of osseointegration and placed the first dental implant 45 years ago,1,2 a milestone was set for successful oral rehabilitation of the edentulous or partially edentulous patient.3,4 At the same time, dental implants are an increasingly viable alternative to conventional prosthodontic treatment options, with the latter supported by evidence-based data of up to 20 years.5–9 Regarding comparable long-term data concerning the outcomes of dental implants, several recently published articles have reported approximate 10-year survival rates between 90% and 98.8%,10–13 and another article even referred to survival rates of 100% after 12 years14 and
Corresponding Author: Dr. Benedicta E. Beck-Broichsitter, Department of Oral and Maxillofacial Surgery, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Campus Forschung Gebäude N27, Hamburg 20246, Germany; e-mail: [email protected] The authors negate any conflict of interest. 1 Equal contribution. © 2015 Wiley Periodicals, Inc. DOI 10.1111/cid.12334
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97.7% to 100% after 16 years.15 The number of articles published with 20-year perspectives remains relatively limited, but published articles have reported survival rates at consistently high levels of 89.5% to 99.2%.16–18 A dental implant fails in the absence of osseointegration during the initial stage of healing, whereas late implant failure occurs in the already healed and functionally loaded dental implant, the mechanical stability of which is compromised due to a continuous decrease in the osseointegrated implant surface. While peri-implant mucositis only affects the soft tissue surrounding the implant, and it remains reversible, periimplantitis is accompanied by additional vertical bone loss at the implant shoulder, which is believed not to be reversible.19 It has been estimated, that within a few years after implantation and initial bone remodeling, 1.4% to 6.6% of the inserted implants will develop peri-implantitis.10– 12,20 The risk of peri-implantitis increases with smoking and poor oral hygiene.21 With preexisting periodontitis, the incidence rate is four to five times higher.22 Further occurrences can arise in cases of osteoporosis and diabetes. The aim of this unicentric study was to evaluate systematically the long-term outcomes of Straumann dental implants with titanium-sprayed surfaces (TPS) in all indication classes, particularly in cases with severe atrophy of the alveolar ridge, considering implantations performed from 1988 to 1999 in the setting of the University Hospital of Kiel. MATERIALS AND METHODS Patient Recruitment Medical records were collected of patients who underwent insertion of Straumann dental implants in the Department of Oral and Maxillofacial Surgery of the Schleswig-Holstein University Hospital in Kiel from 1988 to 1999. Thereby, a total of 723 dental implants inserted in 155 patients were identified. These implants were primarily included, and the patients were contacted via postal mail or telephone. Ninety-two patients (59.35%; 56 women, 36 men) agreed to participate in the study. In these remaining 92 patients, 388 Straumann dental implants were inserted between 1988 and 1999 (average observation time 14 years 1 1.9 years). The subjects were partially and fully edentulous patients. The
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mean age at the follow-up examination was 65.9 years (standard deviation: 111.9 years). Medical Record Assessment Implantation types were defined according to the third ITI Consensus Conference, based on the time between tooth extraction and implantation23: Type I: Immediate implant placement in an extraction socket Type II: Early implant placement after 4 to 8 weeks after tooth removal Type III: Early implant placement after 12 to 16 weeks after tooth removal Type IV: Late implant placement more than 6 months after extraction Vertical and horizontal bone augmentation procedures (e.g., block augementation, sinus floor elevation) were further classified depending on the donor site and the origin of the augmentation material (autologous/ xenogenic). The length, diameter, and position of the implants were previously extracted from surgical reports in the medical records, as were in-house-treated implant failures and consecutive explantation procedures. The type of prosthodontic rehabilitation was classified into fixed prosthodontics (single crown, bridgework) and overdenture prostheses. Implant Therapy Three different surgeons in the department inserted all of the implants examined in this study, according to the manufacturers’ surgical recommendations. The implants were without exception solid screws with TPS. The patients received systemic antibiotics from the day of implant placement and an antibacterial mouth rinse from 7 to 10 days. Sutures were removed 7 to 10 days after implant insertion. All of the patients were instructed regarding how to maintain appropriate oral hygiene directly after implant insertion, and they were reinstructed after an uncovering procedure regarding how to proceed after prosthodontics rehabilitation. Clinical Assessment The patients were specifically asked about systemic diseases (e.g., diabetes mellitus), nicotine abuse, and a history of previously diagnosed periodontitis.
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One independent oral and maxillofacial surgeon (C.M.R.) performed the clinical follow-up examinations in the recalled patients. Full periodontal status was recorded, including probing pocket depths and recessions on four sites of each implant and the remaining teeth. Distances were measured to the nearest millimeter. To determine the status of oral hygiene objectively, bleeding on probing (BOP) was obtained, as well as pus suppuration while probing and signs of gingivitis. Marginal bone levels were measured on the distal and mesial sites of the implants on panoramic radiographs and were calculated based upon the known implant length, and thereby considering the magnification factors on the radiographs. Peri-implantitis was defined according to Ong and colleagues, based on peri-implant probing depth 35 mm, in addition to a positive BOP and/or suppuration and radiographic bone loss 32.5 mm or 33 exposed threads.24 Statistical Assessment R software was employed for the statistical data analyses.25 Descriptive statistics are reported for single factors. Overall implant survival was displayed in Kaplan–Meier plots, including 95% confidence intervals. To identify factors influencing implant survival time, a Cox proportional hazard regression model was applied.
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TABLE 1 Distribution Implants in-situ Position
1
2
3
4
5
6
7
Total
%
Maxilla Mandible
13 0
18 16
7 34
35 33
33 27
32 40
21 19
159 169
48.5 51.5
long-term evaluation and Cox regression analysis for the evaluation of risk factors. Considered alone, the longterm survival rate was 88.03%. Twenty-one implants (35% of all removed implants) were lost within 3 to 6 months, and 28 (46.7% of all removed implants) implants had to be removed within the first 12 months. At the reevaluation, 18.5% (61 implants) of the implants showed radiographic bone loss of 32.5 mm and 9.7% (32 implants) of all in situ implants showed clinical signs of periimplantitis, according to the criteria by Ong and colleagues.24 The distribution of implant loss classified by the presence of peri-implantitis is displayed in Table 3. Regarding the study cohort of 388 implants, a total of 245 (63.14%) were placed in patients with previously diagnosed periodontitis. Among these cases, the rate of implant loss was much higher (17 patients, 18.5%) compared with the patients without periodontitis (7 patients, 7.6%; see Table 4).
RESULTS Descriptive Statistical Evaluation All Implants. Among the 155 patients with 723 implants who were identified first and were contacted for follow-up examinations, 92 patients (59.35%; 56 women, 36 men) agreed to participate in the study, 29 patients (18.71%) refused for their health or personal reasons, 28 patients (18.07%) could not be contacted via postal mail or telephone, and 6 patients (3.87%) were deceased. In the remaining cohort (92 patients, 388 implants), 60 implants (15.5%) in 24 patients were lost at the time of clinical examination – 1 day to 15.5 years after implant insertion. Tables 1 and 2 display the distribution of remaining and lost implants, respectively, in the study cohort. The overall implant survival rate was 84.5% after an average observation time of 14 years (11.9 years). Twelve implants (20% of all of the removed implants) were categorized as early losses within 90 days after implantation and were therefore excluded from
Collective Description Of a total of 388 evaluated implants, 197 (50.8%) were placed in the maxilla and 191 (49.2%) in the mandible. A minimum of one and a maximum of 13 implants were placed per patient (median = 6). Regarding prosthetic rehabilitation, 58.5% of the implants were supplied with fixed restorations, while 84% of this proportion were single crowns, and 16% were bridgework. Of all of the implants, 41.5% served as removable prostheses. Augmentation procedures were performed in 55.4% of all of the implants, including sinus floor
TABLE 2 Distribution Implant Losses Position
1
2
3
4
5
6
7
Total
%
Maxilla Mandible
0 0
5 4
2 4
4 6
2 3
11 7
6 6
30 30
50 50
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TABLE 3 Four Field Matrix: Distribution of Peri-implantitis and Implant Loss among the Patients Peri-implantitis Periimplantitis + − Absolute
Loss + Loss − Absolute %
7 8 15 16.3
17 60 77 83.7
24 68 92
%
26.09 76.09 100
elevations, applying a mix of particulated autologous bone graft and bone replacement materials, as well as vertical and horizontal augmentations, using block grafts of autologous bone (e.g., iliac crest, linea oblique). The overall majority of bone grafts were harvested extraorally (68.8%), whereas in 6.8%, intraoral bone grafts were applied. Bone replacement materials were used in 25.6% of all of the implants with augmentation procedure (Figure 1). The majority of the implants (70.4%) were placed more than 6 months after tooth extraction and thus were Type IV implantations, according to the ITI Consensus. The remainder were immediate placements (Type I; 3.1%), early placements (Type II; 7.2%); and early placements with partial bone healing (Type III; 19.3%), as shown in Figure 2. Figure 3 provides the implant diameters and length distributions in this study, showing a preference for length of 12 or 14 mm and a preferred diameter of approximately 4 mm. Regarding peri-implant health, nearly all of the implants (97.6%) were well osseointegrated with no recordable movement. Grade I movements were recorded in three (0.9%) and grade II in five (1.5%) implants. BOP was negative in the majority (79.6%) of probed implants. Of all implants, 13.68% had a periimplant probing depth 35 mm.
Figure 1 Augmentation procedures were applied in the majority of patients in this study cohort. Extraoral bone grafting was further preferred to augment the jaw bone, followed by the use of bone replacement materials and intraorally harvested bone.
Nicotine abuse was determined in 21 (22.83%) of 92 patients. Twelve of these 21 (57.14%) patients, compared with 12 of 71 (16.9%) nonsmoking patients, lost at least one implant during the observation time (Table 5). One third of the patients who lost an implant had combined risk factors (nicotine abuse and periodontitis). Of all of the patients, 7.8% suffered from diabetes mellitus, but none of these lost implants. Cox Regression and Kaplan–Meier Analyses For regression analyses, a total of 383 implants were included, comprising 57 events (implant losses). A total of five observations had to be deleted due to incomplete data sets. Model selection proceeded from a Cox regression model that included sex, number of implants per patient, implantation site (anterior region: 13 to 23, 33 to 43; posterior region 14 to 17, 24 to 27, 34 to 37, and 44 to 47), implant diameter and implant length according to the range of distributions displayed in Figure 3, time after tooth loss (months), implantation type (according to the Consensus Conference), type of prosthesis (removable/fixed), augmentation (yes/no), cigarette smoking (yes/no), previous periodontitis (yes/no), and
TABLE 4 Four Field Matrix: Distribution of Periodontitis and Implant Loss among the Patients
Loss + Loss − Absolute %
Periodontitis +
Periodontitis −
17 21 38 41.30
7 47 54 58.70
Absolute
%
24 68 92
26.09 73.91 100
Figure 2 ITI implantation types in the study cohort.
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The exponent of the regression coefficient for implantation, which could be interpreted as a hazard ratio, was 3.1643. This finding indicated that, all other things being equal, implantation type II was estimated to have 3.2 times as high a failure rate as Type I, Type III had a 3.2 times as high a failure rate as Type II, and Type IV had a 3.2 times as high a failure rate as Type III. To evaluate the influence of augmentation procedure and implantation type on implant survival (data not shown), Fisher’s exact test was applied but there was no statistically significant correlation (p = .084). DISCUSSION
Figure 3 Distributions of implant diameters and implant lengths of all of the patients.
age (years) at insertion as independent variables. Here, implantation type was coded as a numerical variable according to the ITI consensus because we expected that these numbers correspond roughly to equidistant levels of risk. After stepwise backward selection, two variables were identified, which significantly influenced implant survival time (Table 6): cigarette smoking (p = .001264) and ITI implantation type (p = .00354). Figure 4 displays Kaplan–Meier estimates of implant survival, accounting for the previously identified influence factors. In particular, the figure shows long-term implant survival with 95% confidence intervals (Figure 4A), as well as survival according to ITI implantation type (Figure 4B).
TABLE 5 Four Field Matrix: Distribution of Nicotine Smoking and Implant Loss among the Patients
Loss + Loss − Absolute %
Nicotine +
Nicotine −
Absolute
%
12 9 15 22.83
12 59 77 77.17
24 68 92
26.09 76.09 100
Patients and clinicians must decide every day between prosthodontic restoration methods and implantsupported rehabilitation alternatives. Here, long-term data covering more than 10 years helped in the evaluation of treatment alternatives. In our study, the Kaplan– Meier estimate of the long-term survival rate was 88.03% after 12.2 to 23.5 years after implant insertion. The deviation of this survival rate, compared with the studies mentioned above, could depend on the specialization of the University Department of Oral and Maxillofacial Surgery meeting the specific requirements for the treatment of this special patient cohort. Another possible reason for the deviation of percentages in reports on long-term implant survival is that the majority of patients receiving implant treatment are of advanced age. In our study, nearly 60% of the patients in the original cohort agreed to participate in this follow-up. The survival rate gathered from this patient cohort might not reflect true implant survival. It must be estimated that, not considering deceased patients who might not have influenced long-term survival and who represented only 4% of all patients, information about implant survival and implant function was not available in the remaining 36% of the patient cohort. The data lacking from these patients might have led to a distortion of the results either way because these patients likely visited their dentists for check-ups and alleged implant losses might have been treated elsewhere. Therefore, it cannot be ruled out that the true long-term survival rate might have been lower than we reported in this study due to these dropped out patients. Another reason for the deviation when comparing the survival rates with the previously mentioned longterm studies might be the number of augmentation procedures in this cohort. In particular, the proportion of
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TABLE 6 Cox Regression Analyses
Nicotine ITI implantation type
Regression Coefficient
Exp (Regression Coefficient)
Lower 95% Confidence Limit
Upper 95% Confidence Limit
p Value
0.765 1.1277
2.1489 3.1643
1.178 1.459
3.920 6.863
.01264 .00354
extraorally harvested autologous bone indicated that the majority of the patients suffered from severe alveolar ridge atrophy as defined in the ITI implantation Type IV. Therefore, complex augmentation procedures were needed to restore the alveolar ridge, resulting in a progressively increased likelihood of complications, although bone augmentation procedures themselves were not identified as an influential factor in this study, whereas the ITI implantation type was identified as significantly influencing the long-term implant survival in Cox regression analysis. Comparing immediate and delayed implantation at maxillary molar sites, the 1-year success rate of delayed implantation was estimated at 93.2% of 123 cases, with exclusion of patients who smoke more than 10 cigarettes per day.26 In another multicenter study,27 a total of 143 patients with a total of 264 implants were prospectively evaluated, comparing immediate and delayed implant placement. The survival rate after 5 years was 92.4% for maxillary and 94.7% for mandibular inserted implants.
Regarding the implantation type, no difference in survival rate could be detected.27 In a systematic review performed by Clementini and colleagues, the implant survival and treatment success rates were evaluated after vertical and horizontal-guided bone regeneration. During follow-up periods of 1 to 5 years, implant survival ranged from 93.75% to 100%.28 In another study, the 1-year survival of delayed and immediate implantation with bone block grafts was evaluated, and resulting in a 100% survival rate for immediate and 96.9% for delayed implants.29 Here, the implant surface itself must be considered to be a decisive factor in the survival of dental implants, allowing for rapid healing directly after implant insertion and therefore subsequently stable osseointegration. In a study comparing the outcomes of AstraTech TiOblast and Brånemark implants with turned surfaces over a 12- to 15-year period, there was no significant difference found for implant survival or the prevalence of peri-implantitis, at 5% and 6%, respectively.30
Figure 4 Kaplan–Meier analyses including all of the implants with 95% confidence intervals (A), and further distinguished by ITI implantation type (B).
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Another study, also comparing AstraTech TiOblast and Brånemark implants with machine-etched surfaces, detected no effect of implant surface or design when assessing the rate of peri-implantitis and implant survival after 13 years, defining periimplantitis as 31 mm bone loss in the first year after implant insertion, in conjunction with BOP with or without suppuration.31 In contrast with these results, in another study, comparing Brånemark implants with turned surfaces against TiUnite surfaces, the mean bone level was significantly different in favor of the TiUnite surfaces, as well as showing significantly longer implant survival after a 10-year follow-up period.32 However, according to the literature, other additional influential factors, such as periodontitis and tobacco smoking, might put the implant survival at risk. Although Cox regression analysis did not reveal periodontitis to be a risk factor for implant loss on a single implant level in this cohort, another long-term study of Straumann dental implants revealed an association between peri-implant disease and periodontitis in 89 patients.33 In this context, particuarly in partially edentulous patients with a history of periodontitis, the periimplant tissue might be colonized by periodontally pathogen bacteria originating from pockets of the neighboring teeth, compared with edentulous patients receiving dental implants.34 A recently published long-term study revealed stable clinical and radiographic results 10 years after implantation of Frialit-2 dental implants in a department of periodontology, but tobacco-smoking patients were previously excluded, and a meticulous check-up examination protocol was followed after implant insertion.35 In our study cohort, cigarette smoking was identified as a risk factor for implant loss. A systematic review by Chambrone and colleagues evaluated the influence of tobacco smoking on implant survival after maxillary sinus augmentation.36 In accordance with our study, smoking was associated with implant failure in eight included studies, but interestingly, a correlation with implant failure could not be proved in this review, when studies were performed in a prospective manner.36 Because the definition of peri-implantitis is tied with the loss of vertical bone height at an implant, radiographs are necessary. In our study, panoramic radiographs were obtained, after implantation as well as during the follow-up examinations, in order to ensure
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comparability and, consequently, valid results if the length of the implant is known, and the measurements are close to the implant itself.37 However, due to the nature of the technique for panoramic radiography, the local resolution remains inferior compared with intraorally obtained radiographs.38 CONCLUSION This study emphasized that dental implants were capable of predictable long-term rehabilitation in the majority of even complex patient cases in the Department of Oral and Maxillofacial Surgery. An individual risk profile of patient-related factors and technical aspects remains important for long-term implant survival and should be considered with and communicated to the patient before implantation. REFERENCES 1. Branemark PI, Adell R, Albrektsson T, Lekholm U, Lundkvist S, Rockler B. Osseointegrated titanium fixtures in the treatment of edentulousness. Biomaterials 1983; 4:25– 28. 2. Branemark PI, Adell R, Breine U, Hansson BO, Lindstrom J, Ohlsson A. Intra-osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg 1969; 3:81–100. 3. Branemark PI, Hansson BO, Adell R, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977; 16:1–132. 4. Schroeder A, van der Zypen E, Stich H, Sutter F. The reactions of bone, connective tissue, and epithelium to endosteal implants with titanium-sprayed surfaces. J Maxillofac Surg 1981; 9:15–25. 5. Hammerle CH. Success and failure of fixed bridgework. Periodontol 2000 1994; 4:41–51. 6. Layton DM, Clarke M. A systematic review and metaanalysis of the survival of non-feldspathic porcelain veneers over 5 and 10 years. Int J Prosthodont 2013; 26:111–124. 7. Erpenstein H, Kerschbaum T, Halfin T. Long-term survival of cast-gold inlays in a specialized dental practice. Clin Oral Investig 2001; 5:162–166. 8. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: part 1. Outcome. Int J Prosthodont 2002; 15:439–445. 9. Karlsson S. Failures and length of service in fixed prosthodontics after long-term function. A longitudinal clinical study. Swed Dent J 1989; 13:185–192. 10. Ostman PO, Hellman M, Sennerby L. Ten years later. Results from a prospective single-centre clinical study on 121 oxidized (TiUnite) Branemark implants in 46 patients. Clin Implant Dent Relat Res 2012; 14:852–860.
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11. Fischer K, Stenberg T. Prospective 10-year cohort study based on a randomized controlled trial (RCT) on implant-supported full-arch maxillary prostheses. Part 1: sandblasted and acid-etched implants and mucosal tissue. Clin Implant Dent Relat Res 2012; 14:808–815. 12. Buser D, Janner SF, Wittneben JG, Bragger U, Ramseier CA, Salvi GE. 10-year survival and success rates of 511 titanium implants with a sandblasted and acid-etched surface: a retrospective study in 303 partially edentulous patients. Clin Implant Dent Relat Res 2012; 14:839–851. 13. Wittneben JG, Buser D, Salvi GE, Burgin W, Hicklin S, Bragger U. Complication and failure rates with implantsupported fixed dental prostheses and single crowns: a 10-year retrospective study. Clin Implant Dent Relat Res 2014; 16:356–364. 14. Vroom MG, Sipos P, de Lange GL, et al. Effect of surface topography of screw-shaped titanium implants in humans on clinical and radiographic parameters: a 12-year prospective study. Clin Oral Implants Res 2009; 20:1231– 1239. 15. Jacobs R, Pittayapat P, van Steenberghe D, et al. A splitmouth comparative study up to 16 years of two screwshaped titanium implant systems. J Clin Periodontol 2010; 37:1119–1127. 16. Chappuis V, Buser R, Bragger U, Bornstein MM, Salvi GE, Buser D. Long-term outcomes of dental implants with a titanium plasma-sprayed surface: a 20-year prospective case series study in partially edentulous patients. Clin Implant Dent Relat Res 2013; 15:780–790. 17. Ekelund JA, Lindquist LW, Carlsson GE, Jemt T. Implant treatment in the edentulous mandible: a prospective study on Branemark system implants over more than 20 years. Int J Prosthodont 2003; 16:602–608. 18. Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentulous jaws: a 20-year follow-up. Clin Implant Dent Relat Res 2008; 10:207–217. 19. Botero JE, Gonzalez AM, Mercado RA, Olave G, Contreras A. Subgingival microbiota in peri-implant mucosa lesions and adjacent teeth in partially edentulous patients. J Periodontol 2005; 76:1490–1495. 20. Roos-Jansaker AM, Lindahl C, Renvert H, Renvert S. Nineto fourteen-year follow-up of implant treatment. Part I: implant loss and associations to various factors. J Clin Periodontol 2006; 33:283–289. 21. Wiltfang J, Zernial O, Behrens E, Schlegel A, Warnke PH, Becker ST. Clin Implant Dent Relat Res. 2012 Jun; 14(3):421–427. doi: 10.1111/j.1708-8208.2009.00264.x. Epub 2010 Feb 3. 22. Karoussis IK, Salvi GE, Heitz-Mayfield LJ, Bragger U, Hammerle CH, Lang NP. Long-term implant prognosis in patients with and without a history of chronic periodontitis: a 10-year prospective cohort study of the ITI Dental Implant System. Clin Oral Implants Res 2003; 14:329–339.
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23. Hammerle CH, Chen ST, Wilson TG Jr. Consensus statements and recommended clinical procedures regarding the placement of implants in extraction sockets. Int J Oral Maxillofac Implants 2004; 19(Suppl):26–28. 24. Ong CT, Ivanovski S, Needleman IG, et al. Systematic review of implant outcomes in treated periodontitis subjects. J Clin Periodontol 2008; 35:438–462. 25. Team RDC. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing, 2011. 26. Penarrocha-Oltra D, Demarchi CL, Maestre-Ferrin L, Penarrocha-Diago M. Comparison of immediate and delayed implants in the maxillary molar region: a retrospective study of 123 implants. Int J Oral Maxillofac Implants 2012; 27:604–610. 27. Polizzi G, Grunder U, Goene R, et al. Immediate and delayed implant placement into extraction sockets: a 5-year report. Clin Implant Dent Relat Res 2000; 2:93–99. 28. Clementini M, Morlupi A, Canullo L, Agrestini C, Barlattani A. Success rate of dental implants inserted in horizontal and vertical guided bone regenerated areas: a systematic review. Int J Oral Maxillofac Surg 2012; 41:847– 852. 29. Penarrocha-Diago M, Aloy-Prosper A, Penarrocha-Oltra D, Guirado JL. Localized lateral alveolar ridge augmentation with block bone grafts: simultaneous versus delayed implant placement: a clinical and radiographic retrospective study. Int J Oral Maxillofac Implants 2013; 28:846–853. 30. Ravald N, Dahlgren S, Teiwik A, Grondahl K. Long-term evaluation of Astra Tech and Branemark implants in patients treated with full-arch bridges. Results after 12–15 years. Clin Oral Implants Res 2013; 24:1144–1151. 31. Renvert S, Lindahl C, Rutger Persson G. The incidence of peri-implantitis for two different implant systems over a period of thirteen years. J Clin Periodontol 2012; 39:1191– 1197. 32. Polizzi G, Gualini F, Friberg B. A two-center retrospective analysis of long-term clinical and radiologic data of TiUnite and turned implants placed in the same mouth. Int J Prosthodont 2013; 26:350–358. 33. Karoussis IK, Muller S, Salvi GE, Heitz-Mayfield LJ, Bragger U, Lang NP. Association between periodontal and peri-implant conditions: a 10-year prospective study. Clin Oral Implants Res 2004; 15:1–7. 34. Karbach J, Callaway A, Kwon YD, d’Hoedt B, Al-Nawas B. Comparison of five parameters as risk factors for perimucositis. Int J Oral Maxillofac Implants 2009; 24:491–496. 35. Meyle J, Gersok G, Boedeker RH, Gonzales JR. Long-term analysis of osseointegrated implants in non-smoker patients with a previous history of periodontitis. J Clin Periodontol 2014; 41:504–512. 36. Chambrone L, Preshaw PM, Ferreira JD, Rodrigues JA, Cassoni A, Shibli JA. Effects of tobacco smoking on the sur-
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vival rate of dental implants placed in areas of maxillary sinus floor augmentation: a systematic review. Clin Oral Implants Res. 2014 Apr; 25(4):408–416. doi: 10.1111/ clr.12186. Epub 2013 May 7. 37. Verhoeven JW, Cune MS. [Research methods in dentistry 9. Follow-up of permucosal implants in an edentate mandible
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using panoramic radiography]. Ned Tijdschr Tandheelkd 2005; 112:86–89. 38. Truhlar RS, Morris HF, Ochi S. A review of panoramic radiography and its potential use in implant dentistry. Implant Dent 1993; 2:122–130.
