Epidemiology of post-treatment

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1 Endodontic Topics 2016, 34, All rights reserved Epidemiology of post-treatment disease MICHAEL H ULSMANN 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ENDODONTIC TOPICS Endodontic treatment aims to eliminate or prevent diseases of the pulp and the apical periodontium. Although several strategies have been developed to combat pulpal and periapical inflammation and infection, success rates in endodontics still seem to range considerably below 100%. A critical review of epidemiological studies demonstrates that post-treatment endodontic disease needs to be acknowledged as a common outcome of endodontic treatment. The following review presents the data of available epidemiological studies from different continents and countries. The overall prevalence of post-endodontic apical lesions ranges clearly higher than the failure rates obtained from well-designed clinical studies demonstrating severe deficits in endodontic treatment in daily general dental practice. Received 31 May 2016; accepted 11 June Persistence and occurrence of apical periodontitis are among the main reasons for failure of endodontic treatment. According to Vire (1), endodontic, periodontal, and restorative reasons contribute equally to endodontic failure, each responsible for approximately one-third of all extractions following root canal treatment (RCT), indicating a high prevalence of post-treatment disease. The following review is limited to the epidemiology of treatment failure manifesting as the occurrence or persistence of post-treatment apical periodontitis. The reasons for treatment failure of endodontic origin in terms of occurrence or persistence of apical periodontitis have been intensively outlined by Siqueira (2), Friedman (3), and many other authors in reviews and in respective chapters in endodontic textbooks. Basically, the main reasons for posttreatment disease are either persistence of intraradicular infection (not sufficiently eliminated to achieve clinical and radiographical success/healing) or secondary infection/reinfection during primary treatment or as a result of coronal leakage (2,3). One of the main findings during the last decade is the fact that bacteria in post-treatment disease organize as biofilms with distinct bacterial communities presenting severe challenges during secondary treatment, which may be performed nonsurgically or surgically (4). The endodontic literature presents a number of prospective and retrospective longitudinal and crosssectional studies reporting on the prevalence and incidence of post-treatment disease. These studies differ widely in their study design, making comparison of the results difficult and frequently impossible. The difficulties of planning and performing epidemiological studies and of interpreting the results have been outlined in detail by Eriksen (5), who also criticized a lack of wellplanned epidemiological studies in endodontology. A sufficient database would allow us to answer some of the major unsolved questions in endodontology: What is the progression of endodontic diseases: pulpitis, pulp necrosis, apical periodontitis, posttreatment disease? Are there any effective strategies to prevent endodontic and post-treatment diseases? Are there specific typical differences or modulations of the diseases for certain groups/cohorts (age groups, gender, countries) requiring modification of preventive and operative strategies including modifications to the respective healthcare systems? 42

2 Epidemiology of post-treatment disease Do our current treatment strategies result in an acceptable rate of success and/or survival of diseased teeth? Can we observe improved success rates as a result of improved treatment techniques, instruments (e.g. dental microscope, NiTi instruments, ultrasonics, lasers), or materials? Terminology In the endodontic literature, several different terms can be found for apical periodontitis on root canal treated teeth: Post-treatment disease: This term has been suggested by Friedman (6) and includes both newly developing as well as persisting lesions, which can both have different origins. The concept includes the categories healed/healing and disease instead of success and failure and thus avoids claims of any personal responsibility attributed to the dentist or endodontist who performed the primary root canal treatment. The term especially is helpful and important for communication with the patient requiring further treatment by avoiding having to make the dentist/endodontist responsible for unsuccessful treatment. Persisting apical periodontitis: This term refers to periapical pathosis that does not resolve during the course of root canal treatment. Newly developing lesions are not included. Endodontic failure: This term describes cases with newly developed or persisting periapical disease. Functional: This term describes asymptomatic endodontically treated apical lesions demonstrating decreased size but incomplete healing. The use of this term may have a major impact on treatment decisions as the need for retreatment of such teeth is controversial. Methodological problems Epidemiological studies on the prevalence and incidence of post-treatment disease present with some major methodological problems: Selection of the population investigated: Many studies claim to be representative, but in several cases it remains unclear whether the selected group is actually representative and what representativity is claimed. In some cases the population is clearly defined, i.e. groups of a certain age, from rural communities or larger cities. In other studies patients of a certain dental office or a dental clinic have been investigated, being representative at best only for that particular office or clinic. To perform a study on a representative sample from a complete country, the establishment of a proper study design would require major support from demographic institutes. Most of the epidemiological studies presented in this review lack control groups that would allow comparisons on an international or even nationwide basis, making the results more narrative in nature than really analytic. In the end, many of the studies only allow for an estimation of the distance between the measured outcome and the maximum achievable outcome as demonstrated in prospective clinical studies. Finally, it can be discussed whether an epidemiological study on too large of a population will deliver adequately detailed and differentiated results. For example, results of nationwide studies may be helpful for dental insurance companies calculating member taxes and fees for certain treatments, as well as for considering the structure of a country s healthcare system, but would not have a major impact on treatment concepts. Target: The studies significantly differ in the definition of their target: health of the apical tissues, prevalence of apical periodontitis related to the technical quality of RCT, impact of intracanal posts, or radiographic quality of coronal restorations on apical tissue. Unit of measurement: The unit of measurement may be defined as the number of patients, number of teeth, or number of roots. of measurements: The number of patients and/or teeth included also differs over a wide range. Almost none of the studies present data on the number of included patients/teeth that would be necessary to gain representative results for the group under investigation (power statistics). Criteria for investigation: Different scores and criteria [e.g. periapical index (PAI), periapical probability index (PRI), binary scores] have been used in the reported studies, making comparisons even more difficult or even questionable. 43

3 H ulsmann Radiographic technique: Basically, two types of study material have been selected: full-mouth periapical or panoramic. For ethical reasons, taking only for epidemiological investigations is not possible, and so the majority of epidemiological studies are based on the evaluation of that are already present. As panoramic rather than full-mouth periapical are routinely taken in most dental offices or dental clinics during the patient s first visit, these are frequently selected for epidemiological studies even though they present less exact and detailed information on the periapical status of the teeth. It has repeatedly been described that cone beam computed tomography (CBCT) images disclose a significantly higher prevalence of apical periodontitis than any other type of radiograph including fullmouth periapical and panoramic. This difference has been estimated to be as high as 25 30%. Consequently, the results of epidemiological studies on the prevalence of posttreatment apical disease could be severely affected (7 11). Blinding and calibration of investigators: These important factors are not reported in sufficient detail in many publications. Some studies used the PAI (12) for scoring (13 20), which requires intensive training and calibration of the investigators, but usually no or only insufficient details of observer selection and calibration and of intraobserver reproducibility and interobserver agreement are included. Other studies used the PRI (21) for scoring (22 25). Time elapsed since RCT: Apical periodontitis requires sufficient time for healing and a lesion itself requires time to develop. In epidemiological studies, the time elapsed between endodontic treatment and the taking of remains unknown, resulting in an unknown proportion of lesions being in the state of healing, thus overestimating the rate of post-treatment disease. It has been recommended to judge success or failure approximately 2 years after treatment (26). As in cross-sectional epidemiological studies, if no information on the date of root canal treatment is collected, then a number of periapical lesions will be in the state of healing, thus overestimating the long-term prevalence of the disease. Prevalence of post-treatment apical periodontitis In most studies, the prevalence of apical periodontitis on teeth showing previous root canal treatment is investigated using a cross-sectional study design. Only data on prevalence are presented and discussed in this paper. Incidence of post-treatment apical periodontitis The majority of studies have been performed as prospective or retrospective longitudinal studies evaluating the success or failure of endodontic treatment by comparing pre- and post-treatment, thus monitoring the appearance of the periradicular tissues. Studies on success and failure rates of endodontic treatment, which present information on the incidence of post-treatment apical periodontitis, have already been intensely reviewed in this journal (3) as well as other journals (27,28). Cone beam computed tomography The advent of CBCT in endodontology to some degree has changed the view of periapical periodontitis. A number of well-designed studies have demonstrated a considerably higher prevalence of apical periodontitis than detected using conventional periapical (7 11). The difference has been figured to be approximately 20 30%, suggesting a significantly higher prevalence of apical pathology than reported in most of the epidemiological studies. Until now, no epidemiological study on the prevalence or incidence of post-treatment disease using a larger number of CBCT scans has been published. Only one study from Brazil evaluated the frequency of apical periodontitis using a limited number of 300 CBCTs (29). Prevalence of post-treatment disease The following survey of epidemiological studies on the frequency of post-treatment apical periodontitis is intended to present an overview on its distribution in several countries, thus outlining the frequency and severity of this kind of disease. Comparing the figures, a number of different aspects should be regarded important including: 44

4 Epidemiology of post-treatment disease type of national health system: private or public insurance; economic status of the country and its inhabitants; quality of endodontic education; availability of dental health supply for the group of people included in the study; and availability of endodontic specialists: number, standard, and distribution around the country. Concerning the different epidemiological studies, it should be noted that the aim of this review is to provide the reader with data on the epidemiology of post-endodontic disease rather than go into an indepth discussion of study designs, weaknesses, and strengths of single investigations. Table 1 summarizes the main results of some of these studies (30 82). U.S.A. and Canada U.S.A. In 1995, Buckley & Spangberg (30) investigated the prevalence and technical quality of endodontic treatment in an American subpopulation using fullmouth periapical of 208 randomly selected patients from a university dental school. Out of the endodontically treated teeth, which represented 5.5% of all teeth, 31.3% showed radiographic signs of apical periodontitis. Poor obturation quality (> 50%) and overfills (42.9%) were identified among others as risk factors for post-treatment disease. Canada Dugas et al. (31) examined the of 400 patients from the University of Toronto and 210 from the University of Saskatchewan, Canada, and reported the prevalence of root-filled apical periodontitis as being 44.3% and 50.7%, respectively. Asia Japan Full-mouth of 672 adult patients from a university dental hospital were evaluated; 21% of the teeth were root-filled and 40% of these were associated with apical periodontitis (32). South Korea In a study on 896 root-filled teeth, Kim (33) reported the prevalence of post-treatment apical disease to be 22.8%. South America Brazil In 300 patients, 33.1% of endodontically treated teeth on periapical exhibited signs of apical periodontitis, the majority of those (52%) in root canals with apical extrusion of filling material (34). The frequency of root-filled teeth for an adult population in Sao Luis, Brazil, was 5.9%, the prevalence of apical periodontitis was 11%, and the prevalence of post-treatment disease on root fillings was 42.5% (35). Paes da Silva Ramos Fernandes et al. (29) used CBCT images to detect apical periodontitis in a Brazilian subpopulation of an urban region in Sao Paulo, Brazil, and found apical lesions in 51.4% of the patients and 3.4% of the teeth. Of the root-filled teeth, those with underfilling showed a higher prevalence of post-treatment disease (78.1%) than those with overfilling (57.1%); adequate filling demonstrated apical pathosis in 19.1% of the cases. In 2014, another study was conducted in Brazil by Berlinck et al. (36). They detected apical periodontitis in 7.9% of 1,126 patients with 25,292 teeth (16.7% of the teeth). In this study, females showed a higher prevalence of apical pathology than males. The prevalence of apical lesions in root-filled teeth was as high as 16.7%. Colombia A study with 688 adults attending a dental school in Colombia revealed that apical periodontitis was present in 49% of root-filled teeth (37). Eastern Europe Poland In a cross-sectional study on 236 patients from Poland with 355 a history of endodontic treatment (282 root canal fillings and 73 45

5 H ulsmann Table 1: Survey on epidemiological studies on the prevalence of post-treatment endodontic disease Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Buckley & Spangberg U.S.A (30) mean ,272 full-mouth 4.1% 5.5% 2.5% 31.3% Dugas et al. Canada 2003 (31) 400 (Toronto) 210 (Saskatchewan) ,474 5,647 panoramic and periapical 44.3% 50.7% Tsuneishi et al. Japan 2005 (32) 672 mean 50 16,232 full-mouth 20.5% 1.5% 40% Kim South Korea 2010 (33) 896 RCT 896 panoramic 22.8% Cavalcante et al. Brazil 2003 (34) 300 mean ,375 periapical 6.0% 6.1% 42% 33.1% Tercas et al (35) 200 5,008 full-mouth 5.9% 11% 42.5 Ramos et al (29) 300 5,585 CBCT 3.4% 78.1% Berlinck et al (36) ,292 periapical 7.0% 16.7% Moreno et al. Colombia 2013 (37) 688 with RCT 1,086 49% Boltacz- Rzepkowska & Pawlicka Poland 2003 (38) periapical 282 RCT 73 pulpotomy RCT: 25% pulpotomy: 67% Kamberi et al. Kosovo 2011 (39) 193 4,131 panoramic 12.3% 2.3% 46.3% Matijevic et al. Croatia 2011 (40) 1462 panoramic 8.5% 8.5% 54.0% Persic et al (41) 163 with RCF 412 panoramic 47.3% 46

6 Epidemiology of post-treatment disease Table 1. Continued Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Ilic et al. Serbia 2014 (42) 153 3,526 panoramic 12.5% 51.8% Aleksejuniene et al. Lithuania 1999 (16) periapical 7.2.% 8.2% 6.8% pulpotomy 1.6% 35% 44% pulpotomy Jersa & Kundzina Latvia 2013 (43) 312 7,065 panoramic 7% 18% 31% RCT 49% pulpotomy Kabak & Abbott Belarus 2005 (44) 1,423 > 15 y 31,212 panoramic 12% 20% 45% Bergenholtz et al. Sweden 1973 (45) 240 full-mouth 1.4% 12.7% 31% Allard & Palmquist 1986 (46) 183 2, % 17.6% 27.1% Petersson et al (47) ,297 periapical 2% 31% RCT 54% piulpotomy Bergstr om et al (48) ,593 full-mouth 3.5% 6.5% 28.8% Eckerbom et al (49) 200 4,889 full-mouth 5.2% 13.9% 26.4% Petersson et al (50) 567 periapical 26% RCT 21% pulpotomy Odesj o et al (51) , % 8.6% 24.5% Ridell et al (52) periapical 52% 47

7 H ulsmann Table 1. Continued Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Eckerbom et al. Sweden 2007 (53) y follow-up 2,825 full-mouth 6.8% 17.7% 21.4% Frisk et al (54) 1,973 1,983 1,993 2, ,941 12,343 13,464 12,433 full-mouth full-mouth and panoramic different techniques different techniques 24.5% 23.8% 21.1% 24.6% Hansen & Johansen Norway 1976 (55) 111 2, % 3.4% 46.1% Eriksen et al (15) ,917 panoramic and intraoral 1.4% 3.4% 0.6% of the sample Eriksen et al (13) panoramic and intraoral 3.5% 6.0% 44% Eriksen et al (14) 1973: : : ,981 3,917 3,282 panoramic and intraoral 1.5% 1.4% 0.6% 3.4% 3.4% 1.3% 0.6% 0.8% 0.5% Kirkevang et al. Denmark 2000 (56) full-mouth periapical 52.3% 48

8 Epidemiology of post-treatment disease Table 1. Continued Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Kirkevang et al. Denmark 2001 (57) 358 people with RCT (1974/75) 244 people with RCT (1997/98) full-mouth periapical 50.7% diseased 57.6% diseased Kirkevang et al (58) 1997: : recall (77%) full-mouth periapcal 3% 3.7% 4.9% 5.6% 51.8% 44.1% Kirkevang et al (59) 2008: recall full-mouth periapical 4.2% %:(5 42.9% Huumonen et al. Finland 2016 (60) 5, ,635 panoramic 6.6% 12% adequate RF 25% inadequate RF Loftus et al. Ireland 2005 (61) ,427 panoramic 2% 1.6% 25% Saunders & Saunders Scotland 1997 (62) 340 8, % 5.6% 58.1% De Cleen et al. The Netherlands 1993 (63) 184 4,196 panoramic 2.3% 5.2% 39.2% Peters et al (64) 178 4,594 panoramic 2.5% 4.8% 24.1% DeMoor et al. Belgium 2000 (65) 206 4,617 panoramic 6.6% 6.8% 3.8% 1983: 14.4% 1992: 13.6% 49

9 H ulsmann Table 1. Continued Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Hommez et al. Belgium 2002 (66) 745 periapical 23.8% poor restoration Boucher et al. France 2002 (17) ,373 full-mouth periapical 19.1% 2.0% (PRI > 2) 29.7% (PRI > 2) Lupi-Pegurier et al (67) 344 7, % 18.9% 31.5% Tavares et al (19) 213 full-mouth periapical 33% Imfeld Switzerland 1991 (68) 142 elderly 66 2,004 intraoral 8.5% 20% 31% Sperr Austria 1970 (69) 61% H ulsmann et al. Germany 1991 (22) 200 panoramic 60% Schulte et al (70) 1930 panoramic 14.40% H ulsmann et al (23) full-mouth radographs 3.4% 3.75% 60.00% Klimek et al (71) 500 panoramic 56.9% Weiger et al (72) 323 7,897 periapical or panoramic 3% 2.70% 61% H ulsmann & Snezna 1998 (24) 200: 1976, 1983, 1989, % 50

10 Epidemiology of post-treatment disease Table 1. Continued Results Author(s) Country Year Ref of people Age (years) of teeth Evaluation technique teeth with RCT out Heppeler & H ulsmann Germany 2010 (25) 200 (each 1994 and 2004) panoramic 1994: 3.4% 2004: 4.8% PRI > 2: 3.4% PRI > 2: 4.4% PRI > 2: 44.3% PRI > 2: 41.5% Jimenez- Pinzon et al. Spain 2004 (18) ,453 full-mouth 4.2% 2.1% 2.9% 64.5% Marques et al. Portugal 1998 (73) ,446 panoramic 2.0% 1.5% 22% Sunay et al. Turkey 2007 (74) ,863 panoramic 4.2% 5.3% 1.5% 53.5% Gulsahi et al (75) , % 3.3% 18.2% Gencoglu et al (6) 400 9,460 panoramic and periapical 9.4% 73.9% Ozbas et al (77) , % 1.6% 38% Georgopoulou et al. Greece 2005 (78) ,664 full-mouth 13.6% 9.2% 60% Tolias et al (20) 319 (469 RCT) panoramic 62.3% Al-Omari et al. Jordan 2011 (79) 294 7,390 panoramic 11.6% 5.7% 87% Oginni et al. Nigeria 2015 (80) ,468 full-mouth 12.2% 41% Chala et al. Morocco 2011 (81) periapical 63.8% 39.5% Toure et al. Senegal 2008 (82) 208 6, % 2.6% 56.1% 51

11 H ulsmann pulpotomies), 25% of the root-filled teeth and 67% of a pulpotomy showed signs of periapical pathology (38). Good technical quality was associated with fewer periapical lesions. Kosovo In 2006 and 2007, Kamberi et al. (39) investigated the prevalence of root-filled teeth and apical periodontitis in 193 Kosovar adults attending a university clinic with a total of 4,131 teeth using panoramic and the PAI for scoring the radiographic appearance of the apical tissues. 2.3% of the teeth were endodontically treated and the prevalence of apical periodontitis was reported to be 12.3% of all teeth and 46% of the root-filled teeth. Croatia Two studies were published on the periapical status of root-filled teeth in Croatia (40,41). The prevalence of endodontically treated teeth detected in a total of 1,462 panoramic was 75.9% of the participants and 8.5% of all teeth. 17.8% of the teeth were already missing. Periapical disease (expressed as PAI scores > 2) was detected in 54.0% of the root-filled teeth (40). The authors argue that these results reflect the poor status of oral health in some Eastern European countries due, amongst other reasons, to long-lasting wars and civil wars in some of these countries (e.g. Kosovo, Serbia, Croatia). In the second study, the periapical status of two patient samples from university clinics in Croatia and Austria was compared in (41). Apical lesions were detected in 12.2% of 163 Croatians with 412 root-filled teeth. The prevalence of posttreatment disease in 101 Austrians with 430 rootfilled teeth was 22.1%. The reasons for these differences, as suggested by the authors, are different standards for tooth retention or extraction in both countries, with probably many apical periodontitis extracted without attempts at endodontic treatment in Croatia. A higher incidence of endodontic treatment of apical lesions inevitably will result in a higher number of rootfilled apical disease in a cross-sectional study. Serbia In a study from Serbia (42) on 153 adults with a total of 3,526 teeth, 12.5% presented with root fillings in the panoramic radiograph. The percentage of root-filled teeth showing posttreatment apical disease was 51.8%. Lithuania In a study on a randomly selected sample of year-old Lithuanian adults, 5.6% of all teeth were root-filled and radiographically showed posttreatment apical pathosis (16). The percentage of apical periodontitis in teeth that were not root-filled was 1.6%, whereas the number of root-filled teeth and the percentage of apical pathosis in root-filled teeth alone are not included. Evaluation was undertaken using panoramic and the PRI for scoring. Apical periodontitis occurred more frequently on teeth having undergone RCT than on out root fillings. Latvia In an urban population of 312 people in Riga, Latvia, apical periodontitis was detected in 72% of the participants. 18% of the 7,065 teeth were root-filled with 35% of incomplete fillings and 15% of complete fillings being associated with post-treatment apical disease (43). The group of incompletely filled teeth mainly comprised teeth treated with pulpotomy, probably using formaldehyde-containing materials. Belarus An investigation of 1,423 panoramic of patients of the Belarusian Medical University in Minsk, Belarus, revealed that 20% of all teeth demonstrated some filling material in the root canals and 45% of all root-filled teeth showed apical radiolucency (44). As a specific item of Eastern European countries, in some studies the appearance of radiographical signs of pulpotomies is reported. This may be related to pulpotomy techniques using formaldehyde-containing materials (so-called Russian Red) (40). 52

12 Epidemiology of post-treatment disease Scandinavia Sweden In 1986, Petersson et al. (47), in an evaluation of the of molars and premolars of 861 adults, detected apical periodontitis in 31% of the root-filled teeth, with a frequency of 7% for teeth with complete obturation and 45% for incompletely filled teeth. In a second study (50), evaluating 1,094 treatment plans submitted for approval to the dental insurance system between 1977 and 1979, a prevalence of apical periodontitis in a pulpotomy (n=195) of 21% and of 26% for rootfilled teeth (n=3,383) was reported. Additionally, 65% of teeth showing signs of apicectomy (n=40) were associated with apical lesions. In a follow-up study by the same group (83), mandibular premolars and molars (351 people) were radiographically investigated in 1974 and During this 11-year observation period, nearly equal numbers of teeth healed or developed apical lesions, resulting in a stable prevalence of apical pathology. The authors concluded that the results of cross-sectional studies provide reliable information about the success of root canal treatment in the group investigated. Comparing the apical status of mandibular premolars and molars in 1974 and 1985, the frequency of periapical lesions in root-filled teeth decreased from 35% to 31% and a clear improvement in the technical quality of root fillings was noted for that time interval (84,85). In another study, 117 out of 250 people (46.8%) presented with periapical periodontitis on one or more teeth (48); two-thirds of those were related to root fillings. Approximately 28.8% of the endodontically treated teeth were associated with apical radiolucencies. Apical excess of filling material was related to a higher frequency of apical lesions. Eckerbom et al. (49) investigated the frequency and technical standard of endodontic treatment in 200 patients from a general dental practice. Apical pathosis was found in full-mouth on 26.4% of the root-filled teeth. The number of apical lesions increased with age. In a follow-up study 20 years later (53) with 115 participants from the first examination, the prevalence of apical periodontitis in root canal treated teeth had increased from 17.3% to 21.4%. In a longitudinal study with an interval of 5 7 years, the same group (50) reported that the prevalence of apical lesions in root-filled teeth had slightly decreased from 26.4% to 21.5%, but the number of lesions in untreated teeth had increased. The authors stated that the improvement in the apical health of root-filled teeth could be related to an improvement in the technical quality of the root fillings. In 2006, Ridell et al. (52) investigated the relationship between the technical quality of root fillings and periapical health in adolescents and young adults. Radiographical signs of apical disease were found in 52% of the root-filled teeth, with an unchanged frequency in the control 1 year later. Norway Scoring the periapical status of a representative sample of 35-year-olds from Oslo, Norway, Eriksen et al. (15) detected apical lesions in 1.4% and root fillings in 3.4% of the teeth using panoramic and intraoral. 36% of the root-filled teeth were associated with apical pathosis. The prevalence of apical periodontitis for all teeth had not significantly changed between 1973 (1.5%) and 1984 (1.4%). The prevalence of root-filled teeth with apical lesions also remained stable (1973: 0.6% of all teeth, 1984: 0.8%). Comparing periapical health among 35-year-olds from Oslo, Norway, between 1973 and 1993, the prevalence of apical periodontitis had decreased from 1.5% (1973) and 1.4% (1984) to 0.6% (1993) (14). The prevalence of endodontic treatment showing apical pathosis decreased from 0.6% (1973) and 0.8% (1984) to 0.5% (1993). The improvement in periapical health seemed to be related to a general improvement in oral health in Norway during the observation period. In a random sample of year-old Norwegians from Oslo, apical lesions were observed in 3.5% of all teeth, but in 44% of the root-filled teeth (13). Denmark Kirkevang et al. (56 59) performed a number of different studies on the quality of root canal treatment and the periapical status of root-filled teeth. 53

13 H ulsmann In a study with 614 people on the periapical status of root-filled teeth, 52.3% were associated with periapical lesions. Length of obturation and quality of coronal restoration were the main factors influencing periapical health (56). They also demonstrated that no significant improvement in periapical health was achieved between 1974/75 and 1997/98. The frequency of root-filled teeth showing signs of apical periodontitis even increased from 50.7% to 57.6%, although the technical standard of the root fillings had improved (57). In a further longitudinal study, the periapical and endodontic status of 616 randomly selected people from Arhus, Denmark, was investigated using fullmouth periapical. 77% of these people were investigated again 16 years later, allowing some insight into the dynamics of healing and disease of root-filled teeth. The percentage of lesions following root canal treatment had decreased from 49% to 44.3%. 20% of the teeth diagnosed as being apically sound in 1987 developed an apical lesion, whereas 30% of the apical lesions on rootfilled teeth detected in 1987 healed by 2003, 60% of the lesions persisted, and 10% of the diseased teeth had been extracted by The authors concluded that observation time is a crucial factor and therefore cross-sectional studies should be interpreted with utmost caution regarding the success rates of treatment (58). When 327 randomly selected patients from a general Danish population with root fillings were reevaluated after 10 years, 13% of the initially present teeth had been extracted, 12% had received retreatment, and 42% were associated with apical radiolucency (86). The frequency of root-filled teeth with apical lesions in that study cohort slightly decreased from 1997 (51.8%) to 2003 (44.1%) and 2008 (42.9%) (59). Finland Teeth with apical periodontitis were detected in 27% of 5,335 people taking part in a nationwide survey. The prevalence of root fillings was reported to be 6.6% of the teeth, with apical periodontitis present in 12% of adequate root fillings and 25% in inadequate root fillings. In this study, apical lesions were more frequently detected in women than in men. Middle Europe Ireland In a sample of 302 people attending a dental clinic in Dublin, Ireland, 25% of the root-filled teeth presented with apical lesions compared to 2% in the entire sample and 1.6% in non-root-filled teeth (61). Scotland As reported by Saunders & Saunders (62), the prevalence of post-treatment apical periodontitis in Scotland was 58.1%. The Netherlands In 1993, DeCleen et al. (63) investigated the apical status and the prevalence of root canal treatment in 184 Dutch adults from the Department of Oral Surgery, Academic Medical Center, Amsterdam, The Netherlands, using panoramic. Of the endodontically treated teeth, 39.2% showed apical lesions compared to 5.2% of all non-endodontically treated teeth. In 2011, nearly 20 years later, Peters et al. (64) evaluated 178 with 4,594 teeth. 2.5% of all teeth exhibited signs of apical pathology; 4.8% were root-filled. Of the root-filled teeth, 24.1% showed apical lesions. Belgium Investigating the panoramic of 206 consecutive patients at the University of Gent, Belgium, a prevalence of apical periodontitis of 6.6% was observed; 6.8% of the teeth were treated endodontically with 40% demonstrating apical radiolucencies (65). In a further study (66) comprising 745 root-filled teeth conducted 2 years later, apical lesions were detected in 33% of the teeth in periapical. Statistical analysis revealed a significant influence of the quality of the coronal restoration on the prevalence of apical periodontitis. France In 2002, Boucher et al. (17) investigated the prevalence and technical quality of RCT in a French 54

14 Epidemiology of post-treatment disease subpopulation attending a single dental office in Paris, France. Full-mouth periapical from 208 consecutive patients were evaluated using the PAI for scoring the periapical tissues. The authors reported a high number of root fillings with insufficient technical quality in terms of position and density of the root canal obturation. Roots showing a good technical quality of obturation were associated with a significantly lower prevalence of apical periodontitis. Nevertheless, even in a radiographically good quality of obturation, apical pathosis was present in 15.7% of the cases (PRI > 2). In root posts, significantly more apical lesions were detected than in root-filled teeth without posts. Tavares et al. (19) investigated full-mouth periapical of 213 adults and detected post-treatment disease in 33% of the 1,035 root-filled teeth. The PAI was used for scoring in this study. Switzerland In 1991, Imfeld (68) published a study on the prevalence and quality of endodontic treatment in a group of elders in Z urich, Switzerland. The periapical region was scored using the periapical of year-olds. 64% of the root canal fillings were judged to be insufficient requiring retreatment. Apical pathosis was present in 8.5% of all teeth and in 31% of the root-filled teeth. In 1994, Schulte et al. (70) performed a study on patients of a university clinic and detected a frequency of apical periododontitis of 14.4% in 1983 and 13.6% in In another study on 200 full-mouth from patients at a periodontology department, 3.7% of the teeth were root-filled, with 60 of these probably or definitely showing periapical disease (23). Also in 1995, Klimek et al. (71) published a study comparing the prevalence of rootfilled teeth and apical periodontitis. From 1983 to 1991, the prevalence of root-filled teeth slightly increased from 3.2% to 4.6%. The prevalence of apical periodontitis on root-filled teeth in an adult German population was as high as 61% (72). Southern Europe Spain The prevalence of apical periodontitis and the frequency of endodontically treated teeth in a Spanish population were investigated by Jimenez- Pinzon et al. (18). Apical lesions were present in 61.1% of all people. The overall prevalence of apical periodontitis was 4.2%. For root-filled teeth, the percentage of apical lesions was as high as 64.5%; for non-root-filled teeth, only 2.9%. Portugal For Portugal, a prevalence of apical periodontitis of 15% of 69 root-filled teeth has been reported, the data resulting from an evaluation of 322 residents of Porto, Portugal. The quality of the root fillings was rated as being poor in 54% of the cases, demonstrating that poor radiographic quality of the filling did not necessarily result in post-treatment disease (73). Austria Sperr (69) investigated 500 patients from the University of Graz, Austria, and found 1,687 rootfilled 61% demonstrating post-treatment disease. Germany Turkey In an investigation of 375 patients of a dental university, 5.3% of all teeth (n=8,863) were rootfilled, with 53.3% demonstrating post-treatment disease. The frequency of apical lesions among all teeth was 4.2% (74). Gulsahi et al. (75) investigated 280 panoramic with 1,268 endodontically treated teeth; 41.5% of these showed post-treatment disease. Gencoglu et al. (76) examined 9,460 teeth in 400 patients. The prevalence of root-filled teeth was as low as 9.4%, with 73.9% demonstrating periapical lesions. For a Turkish subpopulation of 438 patients with 11,542 teeth, Ozbasß et al. (77) reported a prevalence of root fillings of 1.55% and of apical periodontitis of 1.68%. 38% of the root-filled teeth were associated with apical lesions. 55

15 H ulsmann Greece Georgopoulou et al. (78) studied a Greek population (320 patients from 16 to 77 years old, full-mouth, 7,664 teeth). 13.6% of the teeth had apical periodontitis, 9.2% were root-filled. 60% of the root-filled teeth showed radiographical signs of post-treatment disease. Tolias et al. (20) investigated 1,781 panoramic of military personnel taken from 1995 to For the first period ( ), 356 root-filled teeth were detected in 1,170 participants with 64.9% of the root-filled teeth demonstrating apical disease. For the second period ( ), fewer root-filled teeth were found (n=113 in 611 people) and the prevalence of apical periodontitis in root-filled teeth decreased to 55.8%. The prevalence of apical disease was negatively correlated to the quality and length of obturation. Whether these data indicate improvements in oral/dental health must remain speculative as no data are presented on the prevalence of missing teeth in these groups. It also should be noted that the study group was composed of participants not older than years of age with only a small percentage of women, making the results not representative for the entire population of the country. The authors point out that endodontic treatment in Greece is performed by general dentists with no special education in endodontology. Near East Jordan In a Jordanian subpopulation of 294 patients, 63% of participants showed root fillings (5.7% of the teeth) and 83.7% presented with apical periodontitis. 11% of the 7,390 teeth were associated with an apical lesion. The prevalence of posttreatment disease was 71.9%, the prevalence of lesions in out root canal treatment was 7.9% (79). Africa Nigeria Oginni et al. (80) investigated 756 patients from a university clinic and reported a frequency of 61% of the patients having root fillings and 67.2% presenting with apical periodontitis. The prevalence of post-treatment apical disease was 41%. Morocco Among adult patients from an endodontic clinic in Morocco, apical lesions were detected in 63.8% of all teeth and in 39.5% of the root-filled teeth (81). Senegal In their study on 208 patients, Toure et al. (82) reported that the prevalence of apical periodontitis in root-filled teeth was 56.1%. Factors affecting treatment outcome Posts The placement of intraradicular posts in some studies has been associated with a significantly higher prevalence of apical periodontitis (17,75). Coronal restoration Several studies have also confirmed a significant influence of the quality of the definite coronal restoration on the prevalence of apical lesions (19,66,71,87). In a study on 1,010 root-filled teeth, the prevalence of apical periodontitis was 81.9% for combined poor restoration and poor endodontics, whereas good endodontics and good restoration resulted in a prevalence of apical lesions of only 8.6% (88). It should be kept in mind that in those studies, the quality of the coronal restorations was evaluated only radiographically and not by clinical evaluation of the restoration with regard to (recurrent) caries and quality and integrity of restoration margins, adjustment of occlusion, approximal contacts, and many other criteria. In a study on 180 patients, good quality root canal fillings and coronal restorations also resulted in significantly less apical pathosis; the impact of the root filling was higher than that of the restoration (89). According to Tronstad et al. (90), the combination of good restoration and good 56

16 Epidemiology of post-treatment disease endodontics received the best state of periapical health; the combination of poor endodontics and poor restoration received the worst results. This was confirmed by a Brazilian study (91) reporting apical lesions on 50.3% of root-filled teeth, with a significantly higher success rate for good quality root canal fillings and coronal restorations and the worst results for a poor quality of both. Kirkevang et al. (56), Frisk et al. (92), and further studies confirmed an influence of the type of coronal restoration on the frequency of apical disease. Radiographic quality of treatment/ obturation The quality of endodontic treatment of course cannot be judged from post-operative. The evaluation of the post-treatment twodimensional radiographic quality of threedimensional root canal obturation, as performed in many epidemiological studies, therefore only represents a poor surrogate for treatment quality. The radiographic quality of root canal obturation in many studies has been associated with the prevalence of apical periodontitis (17,19,38,48,87). It should be kept in mind that root canal treatment in many cases has to be performed in preoperative apical periodontitis, which therefore should be considered the main reason for the presence (or better yet, the persistence) of apical lesions in crosssectional studies rather than the quality of the root canal filling. According to Kirkevang & Wenzel (93) (2003), root canal fillings per se as a result of preoperative pulpal or periradicular disease were identified as the most important risk factor for apical periodontitis. Trends From the studies reported above, no clear trend can be extrapolated, which is true even for countries with several published studies investigating apical health. Unfortunately, only a very limited number of repeated cross-sectional studies are available, not allowing any sound and really evidence-based conclusions on trends concerning the prevalence and incidence of post-treatment disease. The data are inconclusive and partially contradictory, ranging from improvement (20,71,84,94) to worsening (14,25,57), unchanged prevalence (70), or even varying from year to year (24). Well-designed and well-controlled studies on sufficiently large and representative samples are missing. Table 2 presents a survey of repeated crosssectional studies on post-treatment apical periodontitis as presented in the endodontic literature (20,24,25,70,71). In Sweden, in a study by Eckerbom et al. (94), the prevalence of post-treatment disease declined from 26.4% in 1975/76 to 21.5% in 1981/82. Nevertheless, the authors mentioned that the overall quality of endodontic treatment in the majority of cases looked poor. A second study by Petersson (84) confirmed this trend: in 1974 the prevalence of post-treatment apical pathology was 35%; in 1985, 31%. In Denmark, Kirkevang et al. (57) reported a slight increase in root-filled posttreatment apical periodontitis from 50.7% in 1974/ 75 to 57.6% in 1997/98, with a minor improvement in the overall radiographic quality of endodontic treatment. In Norway, the prevalence of root-filled apical lesions increased from 18% in 1973 to 25.6% in 1984 and to 38.1% in 1993 (14). According to the authors, this development is related to further improvements in other oral health parameters during that observation period, reflecting a general improvement in dental and oral health. Additionally, improvements in the quality of endodontic treatment in terms of length and completeness of obturation were observed during the study interval. In Greece, for a Greek subpopulation of military recruits, Tolias et al. (20) reported a decrease in the number of root-filled teeth and a decrease in the prevalence of apical periodontitis on root-filled teeth from 64.9% ( ) to 55.8% ( ). Improved quality of root fillings was also reported in that study. In Germany, Klimek et al. (71) reported a frequency of post-endodontic lesions of 56.9% in 1983 and 45.9% in patients were investigated for each year in that study. H ulsmann & Snezna (24) compared the prevalence and quality of root canal treated teeth in patients attending a university dental clinic between 1976 and panoramic from each 57

17 H ulsmann Table 2: Survey of repeated cross-sectional studies on changes in the prevalence of post-treatment apical periodontitis Country Authors Reference Year of publication Participants Year of investigation of participants Percentage of RCT and apical disease Greece Tolias et al. (20) 2012 Greek recruits years old , % 55.8% Sweden Eckerbom et al patients from a university dental clinic % 21.5% Petersson et al mandibular molars and premolars % 31% Denmark Kirkevang et al patients from a university dental clinic 1974/ / % 57.6%* Norway Eriksen et al year-old citizens of Oslo % 25.6% 38.1% Germany Schulte et al. (70) 1994 patients from a university dental clinic % 13.6% Klimek et al. (71) 1995 patients from a university dental clinic % 45.9% H ulsmann & Snezna (24) 1998 patients from a university dental clinic % 36.2% 56.5% 30.6% 19.7% 33.7% 25.7% 32.1% Heppeler & H ulsmann (25) 200 patients from a university dental clinic % 38.7% * significant 58

18 Epidemiology of post-treatment disease year were evaluated using the PRI as a scoring index. The prevalence of root-filled teeth was 2.6% in 1976, 4.1% in 1991, and 2.8% in 1993, not demonstrating any trend or development. The frequency of PRI scores 4 and 5 (apical lesion probably and definitely present, respectively) was 35.6% in 1976, 56.5% in 1983, 30.6% in 1985, 19.7% in 1987, and 32.1% in These widely differing figures do not allow any valid conclusions on developments in endodontic standards and quality of treatment but rather demonstrate that higher numbers of are necessary as well as clearly defined collectives of patients. Heppeler & H ulsmann (25) compared the prevalence of root canal fillings and apical periodontitis in 1994 and From each year, 200 panoramic of patients attending a university dental clinic were investigated using the PRI. The prevalence of root fillings increased from 3.4% to 4.8%, the prevalence of post-treatment apical pathology (scored as PRI 4 or 5) was 34.6% in 1994 and 38.7% in 2004, a non-significant difference. The contradictory results from Germany do not allow any conclusions concerning changes in the prevalence of post-treatment disease. Discussion It should be noted that this has been just a descriptive presentation of currently available data on the presence (in terms of prevalence and incidence) of post-endodontic disease rather than an analytical approach. It also should be noted that a direct comparison of the results of these numerous studies is not possible or helpful as the study designs show major variability (representativity and size of the population sample, type of, evaluation criteria, and numerous others). Many important details are missing in several of the cited publications, making it difficult or impossible to control the scientific value of the reported data. There are several factors with an unknown but probably high or even decisive impact on the data reported above. In addition to the state and standard of dental education and treatment under conditions of daily practice and the developmental standard of the healthcare system, the country itself with different degrees of access of the people to dental care will influence the prevalence of root-filled and without apical periodontitis. If a low number of root-filled teeth is correlated to a high number of missing teeth, this may be indicative of extraction being preferred over root canal treatment or retreatment. For example, retreatment in Germany is not financially supported by the insurance system, making extraction in many cases the cheaper option for the patient and a less interesting option than prosthetic restoration or implant reconstruction for the dentist. From a methodological point of view, it would be helpful to add information on the number of missing teeth to epidemiological studies on the prevalence of rootfilled teeth and apical periodontitis. The high prevalence of apical periodontitis in root-filled teeth, the increasing number of older patients, and the increasing demand of the patients to retain their natural teeth will result in an increase of retreatments. The high prevalence of posttreatment periodontitis can also be a result of the expanded indication to undertake the attempt to retain difficult-to-treat or sometimes even hopeless teeth. The main conclusions from this review are: Post-treatment apical periodontitis remains a clinical reality that needs to take many aspects into consideration: endodontic education, research, dental insurance, structure of the dental healthcare system, organization of the dental office (instruments, materials, time management), development of treatment strategies and instruments, and many more. Post-treatment disease shows a widely differing prevalence in different countries and different population samples, in some studies even within a country (e.g. urban/rural populations). It should be evaluated whether data on the prevalence and incidence of post-treatment apical inflammation in smaller and well-defined population samples are more helpful for establishing an adequate structure to a dental healthcare system than studies on large samples with unclear representativity. With only few exceptions (20) (Tolias et al. for a Greek subpopulation of military recruits), no improvement of periapical health in root-filled teeth was observed over the years despite a number of biological, technical, and therapeutic 59