Factors influencing root canal retreatment strategies by general practitioners and specialists in Australia.

doi:10.1111/iej.12330

Factors influencing root canal retreatment strategies by general practitioners and specialists in Australia

G. L. Wenteler, C. Sathorn & P. Parashos Melbourne Dental School, University of Melbourne, Melbourne, Vic, Australia

Abstract Wenteler

GL, Sathorn

C, Parashos

P. Factors

influencing root canal retreatment strategies by general practitioners

and

specialists

in

Australia.

International

Endodontic Journal.

Aim To evaluate the effect of tooth radiographic features on root canal retreatment strategies used by general dental practitioners and dental specialists in Australia. Methods A descriptive survey study comprising a web-based questionnaire was sent to general dental practitioners and specialists. The questionnaire diagrammatically represented six different clinical scenarios with variables including type of coronal restoration, quality of root filling and the size and presence of a periapical radiolucency. Treatment options included no treatment, orthograde retreatment, periapical surgery and replacement with an implant. For each of the six scenarios, the participant was asked to select a minimum size cut-off point where treatment would be initiated and also indicate the preferred treatment option. Results A total of 639 questionnaires were submitted online. In teeth without a cast core restoration, the quality of root filling influenced the selection of no treatment as an option (P < 0.001). The presence of a cast post/core restoration influenced both the treatment cut-off point and treatment option, with

more practitioners selecting larger lesions as cut-off points (P < 0.001) and more treatment options involving both implant placement (P < 0.001) and periapical surgery (P < 0.001). With more complex treatment planning (i.e. cast post/core restorations and inadequate root filling), general practitioners proposed implant placement more readily compared with specialists (P < 0.001). Conclusions General practitioners and specialists vary their root canal retreatment strategies according to quality of root filling and type of coronal restoration. Whilst all clinical scenarios could be managed by contemporary endodontic techniques, teeth were still treatment planned for extraction and replacement with an implant. This may be due to the fact that implants are heavily marketed by the dental industry and with more stringent outcome criteria applied to the assessment of root canal treatment compared with implant placement, evidence-based decision-making may be distorted. Future emphasis should be placed on changing practitioners’ attitudes towards the retention of salvageable teeth by contemporary endodontic measures. Keywords: decision-making, endodontic retreatment strategies, endodontic treatment, implant placement, root canal retreatment, treatment planning. Received 17 March 2014; accepted 31 May 2014

Introduction Correspondence: Peter Parashos, Melbourne Dental School, University of Melbourne, 720 Swanston Street, Melbourne, Vic. 3010, Australia (Tel.: +61 3 9341 1472; fax: +61 3 9341 1595; e-mail: [email protected]).

© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd

A fundamental principle in traditional dental practice has been the preservation and rehabilitation of natural teeth. Root canal treatment procedures have played a key role in this context in the retention and

International Endodontic Journal

1

Root canal retreatment strategies in Australia Wenteler et al.

restoration of teeth affected by pulpal and/or periapical pathosis (Friedman 2002, Ørstavik & Pitt Ford 2008). The extraction of teeth has generally been considered undesirable and as a treatment of last resort due to the limitations of prosthodontic replacements such as bridges and removable prostheses (Lewis 1996, Dawson & Cardaci 2006). In recent years, however, this paradigm has been challenged by emerging trends in implant dentistry, with implant replacements being touted as equal to, or even superior to, the preservation of natural teeth (Felton 2005, Thomas & Beagle 2006, Vozza et al. 2011). This has led to concern within endodontic circles regarding the extraction of teeth that may otherwise be managed with sound contemporary endodontic and prosthodontic treatment procedures. When discussing and deciding on a suitable treatment plan for a patient, whether it is root canal treatment, retreatment or implant placement, important factors in decision-making are the clinical outcome and prognosis of the treatment. Comparing the clinical outcome between root canal retreatment or periapical surgery and implants can be problematic as the two treatment modalities address different clinical scenarios (Iqbal & Kim 2007). Implant placement requires the absence of disease, whereas root canal treatment addresses the presence of disease. The role of microorganisms in the pathogenesis of apical periodontitis has been well documented (Kakehashi et al. 1965, Bergenholtz 1974, Sundqvist 1976, M€ oller et al. 1981) and as such, endodontic treatment is directed towards the reduction, entombment and prevention of re-establishment of bacteria within the root canal system and subsequently the prevention and elimination of apical periodontitis (Dawson & Cardaci 2006, Sp angberg 2006, Torabinejad & Goodacre 2006). In contrast, the placement of dental implants is not directed at resolving periapical periodontitis but rather replacing a missing tooth that has been extracted. The tooth may have been extracted as a result of unresolved apical periodontitis or other reasons. Clinicians frequently face the dilemma of whether to endodontically retreat and retain a tooth with an uncertain prognosis or to extract and potentially replace it with a dental implant (Bader 2002). Dentists make the decision for extracting a tooth on the basis of multiple risk factors (Torabinejad & Goodacre 2006) including endodontic and periodontal criteria, remaining tooth structure, restorability with core

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build-ups and post/cores, extent of previous restorations as well as the perceived strategic value of a tooth within the dentition (John et al. 2007). Even though the literature shows evidence of similar outcomes of implant placement and root canal treatment (Doyle et al. 2006, White et al. 2006, Hannaban & Eleazer 2008, Setzer & Kim 2014), much more stringent outcome criteria are usually applied to the assessment of root canal treatment (White et al. 2006, Iqbal & Kim 2007). On the other hand, the use of less stringent criteria in implant studies (generally simple survival) may inherently translate to higher success rates compromising evidence-based decision-making. The aim of this study was to determine whether teeth, that are salvageable by contemporary endodontic techniques, are being treatment planned for extraction and replacement with implants by general practitioners and certain specialities.

Materials and methods Ethics approval was obtained from The University of Melbourne Human Research Ethics Committee (ID 1237449). In order to obtain the most representative population, the decision was made to include general dentists and dental specialists involved in treatment planning and decision-making processes when choosing between implants and root canal retreatment. Specialists included endodontists, periodontists, prosthodontists and oral and maxillofacial surgeons. Using the mathematical formula presented by Dillman (2000), the minimal sample size required to be statistically significant was calculated at 926. A descriptive survey study comprising a web-based questionnaire was sent to the research population sample that included general dental practitioners registered with the Australian Dental Association (ADA Inc., St Leonards, Australia) and specialists registered with the Australian and New Zealand Academy of Endodontists (ANZAE), the Australian and New Zealand Academy of Oral & Maxillofacial Surgeons (ANZAOMS), the Australian and New Zealand Academy of Periodontists (ANZAP) and the Academy of Australian and New Zealand Prosthodontists (AANZP). Due to the privacy policy of the ADA Inc., the electronic link to the web-based software (SurveyMonkeyâ) could not be emailed to their member list. Instead, the link to the web-based questionnaire was advertised in the monthly newsletter (ADA News Bulletin) distributed to all the members. This was performed for a period of 5 months from July 2012 to November 2012.


Wenteler et al. Root canal retreatment strategies in Australia

All the relevant specialist academies agreed to voluntarily participate except ANZAOMS who never replied to any correspondence. Most of the academy members would also have been members of the ADA Inc., and the same advertisement used in the ADA Inc. Newsletter was sent to the members of the academies inviting them to participate in the survey. In order to increase the response rates, a single nonmonetary lottery prize was offered in the form of an iPad. Participants were provided with an email address and asked to forward their contact details via email. This ensured that the identity of the participant was independent of the survey and that the anonymity of the completed questionnaire was ensured. An independent person drew the winner from the reply emails. The questionnaire diagrammatically represented six different clinical situations (Fig. 1). The clinical variables included coronal restoration, quality of root filling and the size and presence of a periapical radiolucency. The coronal restoration included – conservative palatal access restoration and a cast post/core restoration. The qualities of the root fillings included – adequate density and length, defective density and length, and overfill. The five different periapical health status scenarios included – no lesion, widened contour, small lesion, medium-sized lesion and large lesion. Treatment options included – no treatment, orthograde retreatment, periapical surgery and replacement by an implant (Fig. 2). For each of the six scenarios, participants were asked to select a minimum size cut-off point where they perceived that treatment would be initiated and their preferred treatment option. The clinical history for all the scenarios was the same and included a middle-aged patient in good health that presented free from any symptoms. The tooth depicted in the scenarios was a maxillary central incisor with a root filling that was completed 5 years previously. The restoration in the tooth was sound and did not require further treatment. The patient had no other dental problems, and no other dental treatment was planned. Statistical analysis included tests used for matched pair analysis and contingency tables. McNemar’s test was used for comparing scenarios for the same individuals (to test whether their responses were different between scenarios). Fisher’s exact test was used to compare the responses of different individuals (to test the association between their characteristics and their responses).


Results A total of 639 questionnaires were submitted online (490 general practitioners, 51 Endodontists, 21 Periodontists, 33 Prosthodontists and 44 others including Orthodontists, Special Needs Dentists, Oral Medicine Specialists and Postgraduate Students). Due to the privacy policies of all the relevant societies and academies, it was not known to how many practitioners the questionnaire was distributed and consequently an exact response rate could not be calculated. However, based on Dillman (2000), a response rate of 639 (69%) of the calculated sample size of 926 was achieved. In teeth without a cast post/core restoration (Scenarios 1, 2 and 3), the majority of practitioners (43.2–43.8%) (P < 0.001) selected root canal retreatment in teeth with a small periapical lesion (Fig. 3). In teeth with a root filling of inadequate length and density (Scenario 3), practitioners were more likely to propose retreatment at a lower cut-off point (P < 0.001) with 30% of practitioners selecting treatment at a widened PDL space and no lesion compared with 9% seen in Scenarios 1 and 2. The quality of root filling had an influence in the selection of no treatment (P < 0.001) with adequate root filling (Scenarios 1 and 4) attracting no treatment more readily. The quality of root filling appeared not to influence the treatment option when choosing between root canal retreatment and replacement by an implant, with only 1.1–1.7% of practitioners selecting replacement with an implant in teeth without a cast post/ core restoration (Scenarios 1, 2 and 3) (Fig. 4). When choosing between orthograde retreatment and periapical surgery in teeth without a cast post/core restoration (Scenarios 1, 2 and 3), the quality of root filling seemed to have an influence with overfill (Scenario 2) attracting periapical surgery more readily (P < 0.001) (Fig. 4). The presence of a cast post/core restoration (Scenarios 4, 5 and 6) seemed to influence the selection of the minimum treatment cut-off with more practitioners selecting larger lesions (medium and large) (P < 0.001). The presence of a cast post/core restoration also influenced the selection of treatment options when choosing between implants and root canal retreatment (P < 0.001), with 20.2–24.8% of practitioners selecting implant placement as a treatment option in teeth with cast post/core restorations (Scenarios 4, 5 and 6) vs. 1.1–1.7% of practitioners selecting implant placement as a treatment option in


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(a)

(b)

(c)

(d)

(e)

Scenario 1- Adequate root filling in terms of length and density

(a)

(b)

(c)

(d)

(e)

Scenario 2 – Overfill

(a)

(b)

(c)

(d)

(e)

Scenario 3 - Inadequate root filling in terms of length and density

(a)

(b)

(c)

(d)

(e)

Scenario 4 - Adequate root filling in combination with cast post and core

(a)

(b)

(c)

(d)

(e)

Scenario 5 - Overfill in combination with cast post and core

(a)

(b)

(c)

(d)

(e)

Scenario 6 - Inadequate root filling in combination with cast post and core Figure 1 Six different clinical scenarios represented diagrammatically. Scenario 1 – adequate root filling in terms of length and

density. Scenario 2 – overfill. Scenario 3 – inadequate root filling in terms of length and density. Scenario 4 – adequate root filling in combination with cast post and core. Scenario 5 – overfill in combination with cast post and core. Scenario 6 – inadequate root filling in combination with cast post and core.

4




(a)

(b)

(c)

Figure 2 Different treatment options presented diagrammatically; (a) Nonsurgical retreatment; (b) Surgical retreatment; (c) Extraction and replacement with implant.

teeth without a cast post/core restoration (Scenarios 1, 2 and 3) (Fig. 4). This was also the case when choosing between orthograde retreatment and periapical surgery (P < 0.001), with 35.6–60.9% of practitioners selecting periapical surgery as a treatment option in teeth with a cast post/core restoration (Scenarios 4, 5 and 6) vs. 1.1–20.4% of practitioners selecting periapical surgery as a treatment option in teeth without a cast post/core restoration (Scenarios 1, 2 and 3) (Fig. 4). The presence of an overfilling also attracted periapical surgery more readily as a retreatment option irrespective of whether the tooth was restored with a cast post/core restoration or not (P < 0.001). Compared with the endodontists, general practitioners were far more likely to select implant placement in teeth with a cast post/core restoration (P < 0.001) (Fig. 5). General practitioners were also more likely to suggest implant placement compared with the other specialities although it was not statistically significant, which may have been due to the small sample sizes

Figure 3 Treatment cut-off selected by all practitioners (specialists and general practitioners).

Figure 4 Treatment type selected by all practitioners (specialists and general practitioners).



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in the specialities. Amongst the endodontists surveyed, only a single endodontist suggested implant placement for scenario 5 (Fig. 6). Implant placement was selected by periodontists and prosthodontists only for teeth restored with a cast core restoration. Prosth-

odontists suggested implant placement more readily compared with periodontists even though it was not statistically significant (Figs 7 and 8). This may be due to the lack of statistical power given the small sample size.

Figure 5 Treatment type selected by general practitioners.

Figure 6 Treatment type selected by endodontists.

Figure 7 Treatment type selected by periodontists.

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100 90 80 70 60 Non surgical retreatment (%)

50

Surgical retreatment (%)

40

Implant placement (%)

30 20 10 0 Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Scenario 6

Figure 8 Treatment type selected by prosthodontists.

Discussion Traditional approaches used to assess knowledge, views and attitudes of healthcare professionals have included face-to-face or telephone interviews and hardcopy questionnaires (Van Gelder et al. 2010). These approaches, however, increasingly fail to generate qualitatively good results within financial parameters (Ekman & Litton 2006). The Internet is increasingly used as a tool and object for survey studies. The potential to use the Internet as a research tool and not merely an information resource is growing as more healthcare professionals have access to the web (Braithwaite 2003). Web-based questionnaires may be an attractive alternative to the traditional methods of data collection but one of the main disadvantages is the relatively high nonresponse rates compared with traditional modes of data collection (Wyatt 2000, Van Gelder et al. 2010). Even with a nonmonetary prize offered in the present study (Thomson et al. 2004, VanGeest et al. 2007) and several reminders (Edwards et al. 2009) by the relevant academies, responses failed to reach the ideal 926 required for representation of the research population (Dillman 2000). This has also been reflected in the endodontic literature with studies showing very low response rates of 41% (Creasy et al. 2009), 28% (Dutner et al. 2012) and 15% (Azarpazhooh et al. 2013). Consequently, the response rate of 69% achieved in the present study was excellent in comparison. Comparison of demographic data between responders and nonresponders was not possible in the present study because it was web-based; hence, an assessment of


nonresponse bias was also not possible. In any case, nonresponse seems to involve a complex interaction of questionnaire design factors and behavioural issues that may make the effect of nonresponse bias unpredictable (Parashos et al. 2005). The outcome of endodontic therapy has primarily been assessed on the basis of clinical follow-up studies, assessing the radiographic resolution of apical periodontitis. Strindberg (1956) proposed a system based primarily on the presence or absence of radiographic rarefactions at the apex of the root. He considered periapical disease as a non-gradable concept being represented by a persistent periapical radiolucency of any size or appearance and that the only satisfactory post-treatment sequelae combined a symptom-free patient with absence of periradicular radiolucency. Only cases fulfilling these criteria were classified as successful, and subsequently, all others were considered failures, and intervention was indicated at the first sign of radiolucency. However, this system does not take into account the biological aspects of disease and the dynamics of periapical healing and that it may take the lesions several years to heal (Ørstavik 1996, Molven et al. 2002, Huumonen & Ørstavik 2013). Even though the Strindberg (1956) classification of periapical disease has been used extensively in research and dental education, there is a high interindividual variation amongst practitioners in terms of their clinical management of periapical radiolucencies associated with endodontically treated teeth (Reit & Gr€ ondahl 1988, Petersson et al. 1989, H€ ulsmann 1994, Aryanpour 2000, Reit & Kvist 2002). The present study did not state a preoperative periapical


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status but did specify a 5-year time frame for the scenario; if the lesion was healing, it would very likely have healed by 4 years (Ørstavik 1996). Whilst there may be uncommon exceptions (Molven et al. 2002), they should not be the basis for general decisions; rather higher probability situations should guide decision-making. In an attempt to explain the high interindividual variation in clinical retreatment strategies, Kvist et al. (1994) suggested a different concept to that of Strindberg (1956). Instead of periapical disease as a nongradable concept being either present or absent, they proposed the Praxis Concept. This concept assumes that practitioners consider periapical health and disease as a continuum and that periapical disease is perceived at different stages on a continuous health scale, based on their radiographic appearance. Based on this concept, a larger radiolucency is therefore thought to represent a more serious condition than a smaller one. This gradable concept can also been seen in the present study with practitioners varying their treatment cut-off points. In teeth with a poor quality root filling, practitioners were far more likely to select treatment at a lower cut-off point, whereas teeth with a good quality root filling were more likely to receive no treatment as the treatment plan. Although there is evidence that supports the fact that larger periapical lesions tend to be associated with higher bacterial counts (Sundqvist 1976), more prevalent biofilm formation (Ricucci & Siqueira 2010) and polymicrobial as opposed to mono-infections (Fabricius et al. 1982), the size of lesion does not influence the healing of periapical lesions (Ørstavik 1996, Huumonen & Ørstavik 2013). Variations in root canal retreatment behaviour may therefore be regarded as the result of the individual’s choice of different cut-off points for the prescription on the health continuum. The Praxis Concept hypothesises that an individual’s placement of the cut-off point on the periapical health continuum to a large extent is dependent on the practitioner’s personal values (Kvist et al. 1994). This implies that practitioners may agree on facts such as potential for periapical healing, costs and risks of different management strategies of a certain case, but still make different choices amongst opted alternatives due to the variability of their personal values and background (Reit & Kvist 2002). This variation in treatment planning was also seen in this study with practitioners varying treatment cut-off points and treatment options depending on the quality of root filling and

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restoration even though the disease process (the presence and size of a periapical radiolucency) remained unchanged through all the scenarios. The decision to undertake either orthograde retreatment or surgery depends on various factors including the aetiology of the post-treatment disease, the accessibility to the root canal system, soft tissue considerations and other risks involved. Nonsurgical retreatment, when possible, often is the first choice for attempting to correct obvious deficiencies in previous treatment. The quality of previous treatment is an influential factor on the healing outcome of retreatment procedures. Pooled data from the Toronto Study Phase 1–4 (Farzaneh et al. 2004, De Chevigny et al. 2008) indicated that the quality of previous root filling (the length and density) was the most important outcome predictor. These studies showed that when the previous root filling was inadequate, 86% healed compared with only 50% healing when the previous root filling was adequate. This finding concurred with the study by Sundqvist et al. (1998) that showed that poorly treated root canals yield similar bacterial cultures as primary infections, and a welltreated root canal would have fewer bacterial species but more resilient bacteria inside the canal. If these residual microorganisms remain completely entombed within the root canal system, periradicular healing should occur, and it can therefore be concluded that orthograde retreatment would be the treatment of choice in inadequately root filled teeth provided the coronal seal is adequate. This was reflected in the data with 97.8% of all practitioners selecting orthograde retreatment for inadequate root filled teeth restored without a cast post/core restoration (Fig. 1, Scenario 3). Interestingly, if teeth were restored with a cast post/core restoration in combination with an inadequate root filling, this was the most likely scenario to have been extracted and replaced with an implant. This was seen in all practitioner groups except endodontists. Accessibility to the root canal system also plays an important role in treatment decisions. The presence of a post within the canal will restrict coronal access to the root canal system. With post removal, risk factors include root fracture, loss of dentine around the post and root perforation. A survey of American endodontists (Stamos & Gutmann 1993) showed a high number of the respondents thought post removal devices were too dangerous, could not be used universally or they did not work. The presence of a post in a root was also a common reason for respondents to recom-



mend periapical surgery to treat failed cases rather than attempting to remove the post and complete root canal retreatment. However, posts can be removed safely and predictably (Smith 2001, Abbott 2002). Even though posts could be predictably removed from the canal, in this study, practitioners were more likely to select larger lesions as cut-off points and were also more likely to select surgery or implant placement in teeth restored with a post core and crown. With implant and root canal treatments both being highly predictable procedures, arguments are often made that one treatment is more predictable than the other. Both the endodontic literature (Doyle et al. 2006) and the periodontal literature (Vozza et al. 2011) have advocated that their respective disciplines are superior and to make an objective evidence-based decision can be difficult. Recently, there has been an emerging trend that either dentists or their patients prefer the placement of implants rather than the retention of teeth by root canal treatment (Bigras et al. 2008, Di Fiore et al. 2008, Azarpazhooh et al. 2013). A recent survey of general practitioners and specialists found that this was even more relevant for teeth requiring root canal retreatment (Azarpazhooh et al. 2013). The selection for replacement of teeth with an implant increased from 9.5% (for teeth requiring initial root canal treatment) to 25% (for teeth requiring retreatment) and was seen in all groups (general practitioners and specialists) except endodontists. In the present study, all except one endodontist surveyed selected root canal retreatment rather than implant placement, suggesting that the clinical situations depicted in the survey could be managed by contemporary endodontic treatment. This corresponds with Bigras et al. (2008) where the authors compared the clinical decision-making choices of general dentists, prosthodontists, endodontists, oral surgeons and periodontists when presented with endodontics-related patient scenarios. When asked whether to endodontically retreat (nonsurgical and surgical retreatment choices) or replace the specific tooth with an implant, the retreatment option was selected by 96% of the endodontists, 48% of the general dentists, 36% of the prosthodontists, 31% of the oral surgeons and 24% of the periodontists. Extraction and implant placement was the most common choice for all groups except endodontists and general dentists. Recently, Von Arx et al. (2014) confirmed that apical surgery was the most frequently made treatment decision in teeth referred to a specialist in apical surgery; hence, operator bias can


influence treatment choices. Interestingly, in the present study, periodontists were the second least likely to suggest implant placement. Typically periodontists would manage the biological complications associated with implants. With increasingly more implants being placed over the last decade, inherently, biological complications will also be more frequent. This may have an influence on the treatment planning of periodontists explaining the low numbers of implant placement suggested by periodontists. The selection of implant placement was found to be evenly spread amongst practitioners qualifying at different time periods in contrast to Di Fiore et al. (2008) that showed more recent graduates selected implants more frequently than less recent graduates. With the compulsory introduction of CPD to all dental professionals in Australia in 2010, this might be a reflection of wider exposure of all practitioners to lectures and advertising pertaining to implant placement. Similar to Di Fiore et al. (2008), there was an increase in the selection of implants, for all participant groups, as the prosthetic and endodontic complexities of the clinical situations increased. Judging from the responses, even though endodontists indicated that the majority of cases could and probably should be managed by contemporary root canal retreatment options, a large number of general practitioners and other specialities suggested implant placement rather than root canal retreatment. This is concerning especially as the clinical scenario included asymptomatic functional teeth. Although implants are an excellent treatment option for teeth that are not retainable, emphasis should be placed on maintaining teeth that could be managed by contemporary endodontic techniques (Cohn 2005, Dawson & Cardaci 2006, Doyle et al. 2006, Sp angberg 2006, Thomas & Beagle 2006, Iqbal & Kim 2007).

Conclusion This study showed that dental practitioners in general varied their endodontic retreatment strategies according to quality of root filling and type of coronal restoration. General practitioners were significantly more likely to suggest replacement of a tooth with an implant compared with specialists where the tooth was restored with a cast post/core. Endodontists were significantly less likely to suggest implant placement compared with prosthodontists and periodontists. Even though all clinical scenarios could be managed by contemporary endodontic techniques, teeth were


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still treatment planned for extraction and replacement with an implant by disciplines other than endodontics. This may be due to the fact that implants are heavily marketed by the dental industry and with more stringent outcome criteria applied to the assessment of root canal treatment compared with implant placement, evidence-based decision-making may be distorted. Future emphasis should be placed on changing practitioners’ attitudes towards the retention of salvageable teeth by contemporary endodontic measures.

Acknowledgements The authors would like to thank the Melbourne Dental School, Australian Dental Research Foundation (ADRF), Australian Society of Endodontology (ASE Inc.) and Dentsply Australia, for generously providing funding and Dr. Sandy Clark, Statistical Consulting Centre, University of Melbourne for providing statistical support.

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Factors influencing general practitioners' referral decisions.

Medical decision making by general practitioners and specialists.

Factors influencing early retirement intentions in Australian rural general practitioners.

Factors associated with sickness certification of injured workers by General Practitioners in Victoria, Australia.

Endodontic retreatment: a rational approach to root canal reinstrumentation.

A study of communication between general practitioners and specialists.

Comparison of ProTaper and Mtwo retreatment systems in the removal of resin-based root canal obturation materials during retreatment.

Comparison of clinical management of young and elderly asthmatics by respiratory specialists and general practitioners.

General practitioners and sickness certification for injury in Australia.

Factors influencing general practitioners' decisions about cardiovascular disease risk reassessment: findings from experimental and interview studies.

Factors influencing general practitioners' management of psychosocial and physical problems: a study using case vignettes.

Efficacy of protaper next and protaper universal retreatment systems in removing gutta-percha in curved root canals during root canal retreatment.

Factors influencing the location of rural general practitioners. A study in Washington state.

Factors influencing patients' contract choice with general practitioners in Shanghai: a preliminary study.

Efficacy of Different Methods for Removing Root Canal Filling Material in Retreatment - An In-vitro Study.

Study of drug-drug interactions in prescriptions of general practitioners and specialists in iran 2007-2009.

Trends in sickness certification of injured workers by general practitioners in Victoria, Australia.

Endodontic retreatment of a mandibular first molar with five root canal systems: an important clinical lesson.

Dental fees charged by general practitioners and selected specialists in the United States, 1977. Bureau of Economic Research and Statistics.

Intraprofessional collaboration and learning between specialists and general practitioners during postgraduate training: a qualitative study.

The Willingness-to-Pay for General Practitioners in Contractual Service and Influencing Factors among Empty Nesters in Chongqing, China.

A Prescription for Resistance: Management of Staphylococcal Skin Abscesses by General Practitioners in Australia.

Various strategies for pain-free root canal treatment.

The rural pipeline to longer-term rural practice: General practitioners and specialists.