- Email: [email protected]
Survey of dentists to determine contemporary use of endodontic posts
RESEARCH AND EDUCATION
Survey of dentists to determine contemporary use of endodontic posts Sumitha N. Ahmed, BDS, MS,a Terry E. Donovan, DDS,b and Taneet Ghuman, BDS, MSc Dentists are regularly required ABSTRACT to decide whether to retain Statement of problem. Although the scientific literature provides sound decision-making tools for and restore an extensively the restoration of endodontically treated teeth, dentists have different opinions on the rationale for damaged tooth or to extract it the use of endodontic posts (dowels) and selection of post systems. The decision to place a post is and replace it with an implantat times contrary to the literature. Updated information on the treatment of endodontically treated teeth among general dentists is lacking. supported restoration.1 This decision can be difficult and Purpose. The purpose of this survey was to gain insight into the rationale for choice of endodontic must be made by the dentist posts and the different endodontic post systems currently used by dental practitioners. Post and core restorations distribute stress and replace missing tooth structure in endodontically treated and an informed patient on a teeth. Guidelines exist to help select post systems. With the advent of new materials, prefabricated tooth by tooth basis. If the posts have gained popularity among dentists. However, cast-metal post-and-core systems are still decision is to perform endconsidered the gold standard. odontic therapy and retain the Material and methods. Surveys were distributed to dentists attending continuing education tooth, additional decisions are meetings in the United States, Canada, Scotland, Ireland, and Greece. The questions addressed required regarding the optiyears of practice, specialty training, and brand, type, shape, and material of the endodontic post mum protocol for restoring the systems used. tooth. Not all endodontically Results. Descriptive statistical analysis was used to assess the percentage of respondents. Ninetytreated teeth (ETT) need a two percent of the participants were general practitioners with 25.94 ±13.35 years of experience. post-and-core and coronal The majority agreed upon using endodontic posts when insufficient coronal tooth structure restoration. This decision remains and for stress distribution. Passive, parallel posts were the most commonly reported largely depends on the type and shape. With regard to post material, fiber posts were the most frequently used (72.2%), amount of remaining tooth followed by prefabricated alloys (38.6%), cast-metal posts (33.9%), prefabricated titanium posts structure. Some of the treat(30.1%), and stainless-steel posts (21.7%). For cementation, resin-modified glass ionomer (40%) ment options for replacing was most frequently used, followed by self-adhesive resin (29.6%). missing tooth structure and Conclusions. The majority of the practitioners used fiber posts. This may be because, in terms of retaining the coronal restorafracture, they compare favorably with cast-metal post and core, although little evidence in the tion included active versus literature validates this claim. (J Prosthet Dent 2016;-:---) passive posts (dowels), custom cast posts and cores versus prefabricated posts and direct and 50% after 5 years. The major cause of failure with an cores, metal versus flexible posts, serrated versus smooth active post is root fracture.2 Standlee et al,3 in a phoposts, and parallel-sided versus tapered posts. toelastic study, demonstrated the increase in stress-strain Active posts may increase stress on root dentin. Metal patterns when active metal posts were seated into the screws have a reported survival rate of 76% after 1 year canal space.
a
Assistant Professor, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC. Professor and Section Chair, Biomaterials, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC. c Clinical Assistant Professor, ECU School of Dental Medicine, Greeneville, NC. b
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Table 1. Types of posts used by reporting dentists
Clinical Implications
Type of Endodontic Post Material
Even in the presence of evidence, considerable disagreement and/or confusion seems to exist amongst dentists regarding the functions of an endodontic post, when a post should be used, and what type of post should be used.
Fiber post
One of the rationales for placing a flexible post instead of a rigid post is that when the tooth breaks, the mode of fracture is more favorable and the tooth may be re-restored.4,5 However, survival rates of cast metal posts, especially in anterior teeth, have been found to be better than those of flexible posts.6 In terms of the retention of posts, with the improved physical properties of cements, the post diameter and fit are less important than the design and length of the post.7-9 Longer posts provide better stress distribution. Post length should be about two-thirds the length of the root.10 However, the necessity for an apical seal of 4 to 5 mm takes precedence over the need for post length.11 Regardless of the type and design of the post, the need for a 1.5- to 2-mm ferrule is also necessary for clinical success. Libman and Nicholls12 showed that teeth restored with cast posts and cores and complete crowns failed at a significantly lower number of load cycles when the ferrule length was less than 1.5 to 2 mm. Also, tapered posts have a higher failure rate than parallel-sided posts.13,14 Even in the presence of evidence, considerable disagreement and/or confusion seems to exist amongst dentists regarding the functions of a post, when posts should be used, and what types of post should be used.15-18 This difference in opinion among practicing dentists has also been documented through surveybased studies.19-23 Based on the results of these studies, and contrary to the scientific evidence, a large number of dentists are of the opinion that a post reinforces an endodontically treated tooth.24,25 With an increasing number of continuing education courses and meetings, and high attendance at these meetings, the knowledge base of practicing dentists may have changed from that reported in previous surveys. Our hypothesis is that dentists now understand that posts do not reinforce ETT and that they make evidencebased decisions in their selection of post systems. MATERIAL AND METHODS The proposal for the study was submitted to the University of North Carolina Institutional Review Board approval process (IRB# 14-2517) and was determined as Not Human Subject Research (NHSR). Dentists attending continuing education courses in 5 countries (USA, Canada, Scotland, Ireland, Greece),
THE JOURNAL OF PROSTHETIC DENTISTRY
Percentage Use Among Respondents (%) 72.2
Prefabricated titanium
30.1
Stainless steel
21.7
Prefabricated alloy
38.6
Cast metal
33.9
including 10 U.S. states (Indiana, Wisconsin, New Jersey, Kentucky, Colorado, Utah, Texas, South Carolina, North Carolina, and Hawaii) and 1 Canadian province (Ontario) were asked to complete a 2-page survey. The survey is displayed in Supplemental Figure 1. One thousand and eight dentists completed the survey. Participants were asked the number of years they had served in the profession and whether they were general dentists or specialists. They were also asked to select what they believed were appropriate functions of a post. They were asked questions related to the design of the posts they used and the materials used to fabricate the posts. Finally, they were given a list of commercially available prefabricated flexible and rigid posts and asked to identify which of these posts they used in their practices. Descriptive statistical analysis was used to assess the percentage of respondents in each category. Data were analyzed according to the number of years in practice and also by geographic location. RESULTS One thousand and eight dentists completed the survey, with 67% being from North America. The mean time in service as a practicing dentist was 26 years. Ninety-two percent of the respondents were general practitioners. When asked, “What are the functions of a post?” 88% responded “retention of the core,” 22% said “stress distribution,” and 26% included “reinforcement of tooth structure,” as a function. Active screw posts were used by 11.6% of responding dentists, while 76.5% reported using passive posts. Tapered posts were used by 42.5% of reporting dentists, and 50.2% reported they used parallel-sided posts. Custom cast post and core restorations were placed by 34% of respondents. Prefabricated posts were used by 85.9% of responding dentists, and they reported using prefabricated posts in 51.4% of restored ETT (Table 1). Fiber posts were used by 72.2% of the dentists, while 30.2% reported using prefabricated titanium posts and 21.7% used prefabricated stainless steel posts. Six different cements were used for posts; 39.9% used resin modified glass ionomer, 29.7% used self-adhesive resin, 20% used self-etching resin cement, 17.1% used totaletch resin, 16% used glass ionomer, and 6.4% used zinc phosphate cement (Table 2). Ahmed et al
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Table 2. Types of cements used by reporting dentists Type of Cement
Use Among Respondents (%)
Glass ionomer
16.0
Total etch resin
17.1
Self-adhesive resin
29.7
Resin modified glass ionomer
39.9
Zinc phosphate
6.4
Self-etching resin cement
20.0
Twenty-four different commercially available prefabricated fiber posts were used by the respondents, with the most popular being the Parapost Fiber Lux Post System; Coltène/Whaledent). Twenty-six percent of dentists reported using this post system. Twenty-seven different commercially available prefabricated metal post systems were used by respondents. The most popular system was the Parapost system XH, XT, and XP; Coltène/Whaledent, which was used by 42.3% of dentists. The Flexi-Post Systems (Flexi-Flange, Flexi-Titanium, and Flexi-Stainless Steel; Essential Dental Systems) were used by 24.7% of responding dentists. DISCUSSION This survey involved 1008 dentists who were attending continuing education events at various venues. It might be assumed that this represents a better than average cohort of practicing dentists because they were voluntarily involved with continuing dental education, but that fact cannot be validated. It does involve a broad crosssection of dentists coming from 5 countries and 10 different states in the United States. The dentists had a mean time in practice of more than 26 years, which indicates they had considerable practice experience. The data gathered is likely representative of what dentists are currently using to restore ETT. Eighty-eight percent of dentists correctly recognized that the primary function of an endodontic post is to retain the core material. This is an improvement on comparable studies in Sweden (29%), Switzerland (50%), Germany (53%), United Kingdom (25%), and the United States (59%), which reported that dentists believed that a post reinforced ETT and reduced the risk of fracture.19-23 However, 26% still continue to cling to the old idea that posts are necessary to reinforce tooth structure despite extensive evidence that posts do nothing to reinforce the tooth.24,25 Dentists are using a variety of approaches for restoring ETT. More than 33% of responding dentists said they were still using custom cast posts and cores, which may indicate that they are still restoring extensively damaged teeth or they preferred this type of post over the others. Prefabricated posts were used by 86% of dentists, with 72% using flexible posts and 52% using Ahmed et al
rigid metal posts. In previous surveys of this nature, the majority of dentists in Sweden and the United States used cast posts.19,23 The current survey did not determine the intraoral location of use of flexible posts and rigid posts. Nonetheless, the authors are concerned about the extensive use of flexible posts to restore ETT. Clinical studies related to flexible posts have yielded equivocal results. Fredriksson et al4 reported on 236 ETT restored with carbon fiber posts and had a failure rate of 2% at 32 months. Segerstrom et al5 followed this same cohort of patients and reported a failure rate of 35% at 6.7 years. The primary mechanism of failure was loosening of the post due to the flexure of the resin cement and the subsequent hydrolytic breakdown of the polymer holding the fiber posts together. Naumann et al16-18 found a 4.6% failure rate per year of ETT restored with glass fiber posts, which equals 46% at 10 years. The failure rate specifically on anterior teeth was 6.7% per year, 67% at 10 years. These data suggest that flexible posts should not be used with anterior teeth. Conversely, Ferrari et al26 found a survival rate of 90% at 7 to 11 years using 3 types of posts and a sample size of 1304 teeth. No criteria were given for when a post was placed, so many of the ETT treated may not have actually required a post. One of the rationales for placing a flexible post instead of a rigid post is that when the tooth breaks, the mode of fracture is more favorable and the tooth may be able to be re-restored. While this is partially true, most fractures seem to occur at the neck of the tooth, and while it is possible to restore the retained root, in that situation many clinicians would recommend extraction and implant placement. Seventy-six percent of the participants reported the use of passive posts. The use of parallel versus tapered posts was 42.46% and 50.2%, respectively. As discussed earlier, active posts are known to increase the stress on root dentin, resulting in root fracture.2,3 Although the current study did not specifically enquire into the use of screw design posts, another survey conducted in the United States in the early 1990s showed that this design was less frequently used.23 Six different cements were used to cement posts, with the most common being resin modified glass ionomer (40%). Resin-based cements are clearly indicated for flexible posts and metal posts can be cemented with any of the cements listed. Clearly, dentists are using a wide variety of approaches and materials to restore ETT. Both active and passive posts are being used, as well as custom cast post and cores and prefabricated posts. With prefabricated posts, a wide variety of both flexible and rigid posts are used along with 6 different luting agents. Whether this is a good or bad situation is a matter of conjecture. The plethora of materials and approaches is likely a result of
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the limited evidence base for restoring ETT. Very few clinical trials evaluating post performance clearly indicate when posts are used, making it impossible to determine whether the use of the studied post had any impact on the outcome. The limited evidence base may also result in a lack of conformity and consensus in teaching the topic in dental schools, which could contribute to the lack of consensus in the treatment protocols used by dentists. A survey of dental schools to determine what is currently being taught would be informative. Although the survey participants included dentists from 5 countries and 10 US states, 1008 respondents is a small sample from which to draw conclusions about practices based on geographic regions. Even so, the study gives us an insight into the materials that dentists are currently using to restore ETT. Because of the unequal distribution of the respondents across the geographic regions where the survey was distributed, a statistically significant difference or trend in the use of post systems between the dentists in different countries could not be determined. Another limitation of the study, as in the case of previous surveys of this nature, is that the quantitative evidence provided in the study are estimates given by participating dentists rather than actual clinical figures. CONCLUSIONS Within the limitations of the study, the major findings of the survey were as follows: 1. Most dentists (88%) understood the main function of a post in ETT is to retain the core. 2. Most dentists reported they used passive posts (76%). 3. More than 40% of dentists continue to place custom cast post and cores, and the majority (86%) use prefabricated posts. 4. Fiber posts are used by 72% of dentists. 5. Six different types of cements are used for posts. REFERENCES 1. Gatten DL, Riedy CA, Hong SK, Johnson JD, Cobenca N. Quality of life of endodontically treated versus implant treated patients: a university-based qualitative research study. J Endo 2011;37:903-9. 2. Schmitter M, Rammelsberg P, Gabbert O, Ohlmann B. Influence of clinical baseline findings on the survival of 2 post systems: a randomized clinical trial. Int J Prosthodont 2007;20:173-8. 3. Standlee JP, Caputo AA, Holcomb J, Trabert KC. The retentive and stressdistributing properties of a threaded endodontic dowel. J Prosthet Dent 1980;44:398-404. 4. Fredriksson M, Astback J, Pamenius M, Arvidson K. A retrospective study of 236 patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent 1998;80:151-7.
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5. Segerstrom S, Astback J, Ekstrand KD. A retrospective long term study of teeth restored with prefabricated carbon fiber reinforced epoxy resin posts. Swed Dent J 2006;30:1-8. 6. Jung RE, Kalkstein O, Sailer I, Roos M, Hämmerle CH. A comparison of composite post buildups and cast gold post-and-core buildups for the restoration of nonvital teeth after 5 to 10 years. Int J Prosthodont 2007;20: 63-9. 7. Bitter K, Eirich W, Neumann K, Weiger R, Krastl G. Effect of cleaning method, luting agent and preparation procedure on the retention of fibre posts. Int Endod J 2012;45:1116-26. 8. Perdigão J, Gomes G, Augusto V. The effect of dowel space on the bond strengths of fiber posts. J Prosthodont 2007;16:154-64. 9. Standlee JP, Caputo AA, Hanson EC. Retention of endodontic dowels: Effects of cement, dowel length, diameter, and design. J Prosthet Dent 1978;39: 401-5. 10. Morgano SM, Rodrigues AHC, Sabrosa CE. Restoration of endodontically treated teeth. Dent Clin N Am 2004;48:397-416. 11. Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet Dent 1984;51:780-4. 12. Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont 1995;8:155-61. 13. Torbjörner A, Karlsson S, Ödman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995;73:439-44. 14. Morgano SM, Brackett SE. Foundation restorations in fixed prosthodontics: current knowledge and future needs. J Prosthet Dent 1999;82:643-57. 15. Gomez-Polo M, Llido B, Rivero A, del Rio J, Celemin A. A 10-year retrospective study of the survival rate of teeth restored with metal prefabricated posts versus cast metal posts and cores. J Dent 2010;38:916-20. 16. Naumann M, Koelpin M, Beuer F, Meyer-Lueckel H. 10-year survival evaluation for glass-fiber-supported postendodontic restoration: a prospective observational clinical study. J Endod 2012;38:432-5. 17. Naumann M, Blankenstein F, Kiebling F, Dietrich T. Risk factors for failure of glass fiber-reinforced composite post restorations: a prospective observational clinical study. Eur J Oral Sci 2005;113:519-24. 18. Naumann M, Sterzenbach G, Alexandra F, Dietrich T. Randomized controlled clinical pilot trial of titanium vs. glass fiber prefabricated posts: preliminary results after up to 3 years. Int J Prosthodont 2007;20:499-503. 19. Eckerbom M, Magnusson T. Restoring endodontically treated teeth: a survey of current opinions among board-certified prosthodontists and general dental practitioners in Sweden. Int J Prosthodont 2001;14:245-9. 20. Kon M, Zitzmann NU, Weiger R, Krastl G. Postendodontic restoration: a survey among dentists in Switzerland. Schweizer Monatsschrift fur Zahnmedizin 2013;123:1076-88. 21. Naumann M, Kiessling S, Seemann R. Treatment concepts for restoration of endodontically treated teeth: a nationwide survey of dentists in Germany. J Prosthet Dent 2006;96:332-8. 22. Seow LL, Toh CG, Wilson NH. A survey of current practices among general dental practitioners in Manchester in 2002. Primary Dental Care 2003;10: 87-92. 23. Morgano SM, Hashem AF, Fotoohi K, Rose L. A nationwide survey of contemporary philosophies and techniques of restoring endodontically treated teeth. J Prosthet Dent 1994;72:259-67. 24. Lovdahl PE, Nicholls JI. Pin-retained amalgam cores vs. cast-gold dowelcores. J Prosthet Dent 1977;38:507-14. 25. Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J Prosthet Dent 1979;42: 39-44. 26. Ferrari M, Cagidiaco MC, Goracci C, Vichi A, Mason PN, Radovic I, et al. Long-term retrospective study of the clinical performance of fiber posts. Am J Dent 2007;20:287-91. Corresponding author: Dr Sumitha Nazar Ahmed Department of Operative Dentistry UNC School of Dentistry Chapel Hill, NC Email: [email protected] Acknowledgments The authors thank Dr Ceib Phillips for her support in creating the teleform survey and help with the statistical analysis. Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.
Ahmed et al
Survey of dentists to determine contemporary use of endodontic posts Sumitha N. Ahmed, BDS, MS,a Terry E. Donovan, DDS,b and Taneet Ghuman, BDS, MSc Dentists are regularly required ABSTRACT to decide whether to retain Statement of problem. Although the scientific literature provides sound decision-making tools for and restore an extensively the restoration of endodontically treated teeth, dentists have different opinions on the rationale for damaged tooth or to extract it the use of endodontic posts (dowels) and selection of post systems. The decision to place a post is and replace it with an implantat times contrary to the literature. Updated information on the treatment of endodontically treated teeth among general dentists is lacking. supported restoration.1 This decision can be difficult and Purpose. The purpose of this survey was to gain insight into the rationale for choice of endodontic must be made by the dentist posts and the different endodontic post systems currently used by dental practitioners. Post and core restorations distribute stress and replace missing tooth structure in endodontically treated and an informed patient on a teeth. Guidelines exist to help select post systems. With the advent of new materials, prefabricated tooth by tooth basis. If the posts have gained popularity among dentists. However, cast-metal post-and-core systems are still decision is to perform endconsidered the gold standard. odontic therapy and retain the Material and methods. Surveys were distributed to dentists attending continuing education tooth, additional decisions are meetings in the United States, Canada, Scotland, Ireland, and Greece. The questions addressed required regarding the optiyears of practice, specialty training, and brand, type, shape, and material of the endodontic post mum protocol for restoring the systems used. tooth. Not all endodontically Results. Descriptive statistical analysis was used to assess the percentage of respondents. Ninetytreated teeth (ETT) need a two percent of the participants were general practitioners with 25.94 ±13.35 years of experience. post-and-core and coronal The majority agreed upon using endodontic posts when insufficient coronal tooth structure restoration. This decision remains and for stress distribution. Passive, parallel posts were the most commonly reported largely depends on the type and shape. With regard to post material, fiber posts were the most frequently used (72.2%), amount of remaining tooth followed by prefabricated alloys (38.6%), cast-metal posts (33.9%), prefabricated titanium posts structure. Some of the treat(30.1%), and stainless-steel posts (21.7%). For cementation, resin-modified glass ionomer (40%) ment options for replacing was most frequently used, followed by self-adhesive resin (29.6%). missing tooth structure and Conclusions. The majority of the practitioners used fiber posts. This may be because, in terms of retaining the coronal restorafracture, they compare favorably with cast-metal post and core, although little evidence in the tion included active versus literature validates this claim. (J Prosthet Dent 2016;-:---) passive posts (dowels), custom cast posts and cores versus prefabricated posts and direct and 50% after 5 years. The major cause of failure with an cores, metal versus flexible posts, serrated versus smooth active post is root fracture.2 Standlee et al,3 in a phoposts, and parallel-sided versus tapered posts. toelastic study, demonstrated the increase in stress-strain Active posts may increase stress on root dentin. Metal patterns when active metal posts were seated into the screws have a reported survival rate of 76% after 1 year canal space.
a
Assistant Professor, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC. Professor and Section Chair, Biomaterials, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC. c Clinical Assistant Professor, ECU School of Dental Medicine, Greeneville, NC. b
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Table 1. Types of posts used by reporting dentists
Clinical Implications
Type of Endodontic Post Material
Even in the presence of evidence, considerable disagreement and/or confusion seems to exist amongst dentists regarding the functions of an endodontic post, when a post should be used, and what type of post should be used.
Fiber post
One of the rationales for placing a flexible post instead of a rigid post is that when the tooth breaks, the mode of fracture is more favorable and the tooth may be re-restored.4,5 However, survival rates of cast metal posts, especially in anterior teeth, have been found to be better than those of flexible posts.6 In terms of the retention of posts, with the improved physical properties of cements, the post diameter and fit are less important than the design and length of the post.7-9 Longer posts provide better stress distribution. Post length should be about two-thirds the length of the root.10 However, the necessity for an apical seal of 4 to 5 mm takes precedence over the need for post length.11 Regardless of the type and design of the post, the need for a 1.5- to 2-mm ferrule is also necessary for clinical success. Libman and Nicholls12 showed that teeth restored with cast posts and cores and complete crowns failed at a significantly lower number of load cycles when the ferrule length was less than 1.5 to 2 mm. Also, tapered posts have a higher failure rate than parallel-sided posts.13,14 Even in the presence of evidence, considerable disagreement and/or confusion seems to exist amongst dentists regarding the functions of a post, when posts should be used, and what types of post should be used.15-18 This difference in opinion among practicing dentists has also been documented through surveybased studies.19-23 Based on the results of these studies, and contrary to the scientific evidence, a large number of dentists are of the opinion that a post reinforces an endodontically treated tooth.24,25 With an increasing number of continuing education courses and meetings, and high attendance at these meetings, the knowledge base of practicing dentists may have changed from that reported in previous surveys. Our hypothesis is that dentists now understand that posts do not reinforce ETT and that they make evidencebased decisions in their selection of post systems. MATERIAL AND METHODS The proposal for the study was submitted to the University of North Carolina Institutional Review Board approval process (IRB# 14-2517) and was determined as Not Human Subject Research (NHSR). Dentists attending continuing education courses in 5 countries (USA, Canada, Scotland, Ireland, Greece),
THE JOURNAL OF PROSTHETIC DENTISTRY
Percentage Use Among Respondents (%) 72.2
Prefabricated titanium
30.1
Stainless steel
21.7
Prefabricated alloy
38.6
Cast metal
33.9
including 10 U.S. states (Indiana, Wisconsin, New Jersey, Kentucky, Colorado, Utah, Texas, South Carolina, North Carolina, and Hawaii) and 1 Canadian province (Ontario) were asked to complete a 2-page survey. The survey is displayed in Supplemental Figure 1. One thousand and eight dentists completed the survey. Participants were asked the number of years they had served in the profession and whether they were general dentists or specialists. They were also asked to select what they believed were appropriate functions of a post. They were asked questions related to the design of the posts they used and the materials used to fabricate the posts. Finally, they were given a list of commercially available prefabricated flexible and rigid posts and asked to identify which of these posts they used in their practices. Descriptive statistical analysis was used to assess the percentage of respondents in each category. Data were analyzed according to the number of years in practice and also by geographic location. RESULTS One thousand and eight dentists completed the survey, with 67% being from North America. The mean time in service as a practicing dentist was 26 years. Ninety-two percent of the respondents were general practitioners. When asked, “What are the functions of a post?” 88% responded “retention of the core,” 22% said “stress distribution,” and 26% included “reinforcement of tooth structure,” as a function. Active screw posts were used by 11.6% of responding dentists, while 76.5% reported using passive posts. Tapered posts were used by 42.5% of reporting dentists, and 50.2% reported they used parallel-sided posts. Custom cast post and core restorations were placed by 34% of respondents. Prefabricated posts were used by 85.9% of responding dentists, and they reported using prefabricated posts in 51.4% of restored ETT (Table 1). Fiber posts were used by 72.2% of the dentists, while 30.2% reported using prefabricated titanium posts and 21.7% used prefabricated stainless steel posts. Six different cements were used for posts; 39.9% used resin modified glass ionomer, 29.7% used self-adhesive resin, 20% used self-etching resin cement, 17.1% used totaletch resin, 16% used glass ionomer, and 6.4% used zinc phosphate cement (Table 2). Ahmed et al
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Table 2. Types of cements used by reporting dentists Type of Cement
Use Among Respondents (%)
Glass ionomer
16.0
Total etch resin
17.1
Self-adhesive resin
29.7
Resin modified glass ionomer
39.9
Zinc phosphate
6.4
Self-etching resin cement
20.0
Twenty-four different commercially available prefabricated fiber posts were used by the respondents, with the most popular being the Parapost Fiber Lux Post System; Coltène/Whaledent). Twenty-six percent of dentists reported using this post system. Twenty-seven different commercially available prefabricated metal post systems were used by respondents. The most popular system was the Parapost system XH, XT, and XP; Coltène/Whaledent, which was used by 42.3% of dentists. The Flexi-Post Systems (Flexi-Flange, Flexi-Titanium, and Flexi-Stainless Steel; Essential Dental Systems) were used by 24.7% of responding dentists. DISCUSSION This survey involved 1008 dentists who were attending continuing education events at various venues. It might be assumed that this represents a better than average cohort of practicing dentists because they were voluntarily involved with continuing dental education, but that fact cannot be validated. It does involve a broad crosssection of dentists coming from 5 countries and 10 different states in the United States. The dentists had a mean time in practice of more than 26 years, which indicates they had considerable practice experience. The data gathered is likely representative of what dentists are currently using to restore ETT. Eighty-eight percent of dentists correctly recognized that the primary function of an endodontic post is to retain the core material. This is an improvement on comparable studies in Sweden (29%), Switzerland (50%), Germany (53%), United Kingdom (25%), and the United States (59%), which reported that dentists believed that a post reinforced ETT and reduced the risk of fracture.19-23 However, 26% still continue to cling to the old idea that posts are necessary to reinforce tooth structure despite extensive evidence that posts do nothing to reinforce the tooth.24,25 Dentists are using a variety of approaches for restoring ETT. More than 33% of responding dentists said they were still using custom cast posts and cores, which may indicate that they are still restoring extensively damaged teeth or they preferred this type of post over the others. Prefabricated posts were used by 86% of dentists, with 72% using flexible posts and 52% using Ahmed et al
rigid metal posts. In previous surveys of this nature, the majority of dentists in Sweden and the United States used cast posts.19,23 The current survey did not determine the intraoral location of use of flexible posts and rigid posts. Nonetheless, the authors are concerned about the extensive use of flexible posts to restore ETT. Clinical studies related to flexible posts have yielded equivocal results. Fredriksson et al4 reported on 236 ETT restored with carbon fiber posts and had a failure rate of 2% at 32 months. Segerstrom et al5 followed this same cohort of patients and reported a failure rate of 35% at 6.7 years. The primary mechanism of failure was loosening of the post due to the flexure of the resin cement and the subsequent hydrolytic breakdown of the polymer holding the fiber posts together. Naumann et al16-18 found a 4.6% failure rate per year of ETT restored with glass fiber posts, which equals 46% at 10 years. The failure rate specifically on anterior teeth was 6.7% per year, 67% at 10 years. These data suggest that flexible posts should not be used with anterior teeth. Conversely, Ferrari et al26 found a survival rate of 90% at 7 to 11 years using 3 types of posts and a sample size of 1304 teeth. No criteria were given for when a post was placed, so many of the ETT treated may not have actually required a post. One of the rationales for placing a flexible post instead of a rigid post is that when the tooth breaks, the mode of fracture is more favorable and the tooth may be able to be re-restored. While this is partially true, most fractures seem to occur at the neck of the tooth, and while it is possible to restore the retained root, in that situation many clinicians would recommend extraction and implant placement. Seventy-six percent of the participants reported the use of passive posts. The use of parallel versus tapered posts was 42.46% and 50.2%, respectively. As discussed earlier, active posts are known to increase the stress on root dentin, resulting in root fracture.2,3 Although the current study did not specifically enquire into the use of screw design posts, another survey conducted in the United States in the early 1990s showed that this design was less frequently used.23 Six different cements were used to cement posts, with the most common being resin modified glass ionomer (40%). Resin-based cements are clearly indicated for flexible posts and metal posts can be cemented with any of the cements listed. Clearly, dentists are using a wide variety of approaches and materials to restore ETT. Both active and passive posts are being used, as well as custom cast post and cores and prefabricated posts. With prefabricated posts, a wide variety of both flexible and rigid posts are used along with 6 different luting agents. Whether this is a good or bad situation is a matter of conjecture. The plethora of materials and approaches is likely a result of
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the limited evidence base for restoring ETT. Very few clinical trials evaluating post performance clearly indicate when posts are used, making it impossible to determine whether the use of the studied post had any impact on the outcome. The limited evidence base may also result in a lack of conformity and consensus in teaching the topic in dental schools, which could contribute to the lack of consensus in the treatment protocols used by dentists. A survey of dental schools to determine what is currently being taught would be informative. Although the survey participants included dentists from 5 countries and 10 US states, 1008 respondents is a small sample from which to draw conclusions about practices based on geographic regions. Even so, the study gives us an insight into the materials that dentists are currently using to restore ETT. Because of the unequal distribution of the respondents across the geographic regions where the survey was distributed, a statistically significant difference or trend in the use of post systems between the dentists in different countries could not be determined. Another limitation of the study, as in the case of previous surveys of this nature, is that the quantitative evidence provided in the study are estimates given by participating dentists rather than actual clinical figures. CONCLUSIONS Within the limitations of the study, the major findings of the survey were as follows: 1. Most dentists (88%) understood the main function of a post in ETT is to retain the core. 2. Most dentists reported they used passive posts (76%). 3. More than 40% of dentists continue to place custom cast post and cores, and the majority (86%) use prefabricated posts. 4. Fiber posts are used by 72% of dentists. 5. Six different types of cements are used for posts. REFERENCES 1. Gatten DL, Riedy CA, Hong SK, Johnson JD, Cobenca N. Quality of life of endodontically treated versus implant treated patients: a university-based qualitative research study. J Endo 2011;37:903-9. 2. Schmitter M, Rammelsberg P, Gabbert O, Ohlmann B. Influence of clinical baseline findings on the survival of 2 post systems: a randomized clinical trial. Int J Prosthodont 2007;20:173-8. 3. Standlee JP, Caputo AA, Holcomb J, Trabert KC. The retentive and stressdistributing properties of a threaded endodontic dowel. J Prosthet Dent 1980;44:398-404. 4. Fredriksson M, Astback J, Pamenius M, Arvidson K. A retrospective study of 236 patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J Prosthet Dent 1998;80:151-7.
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5. Segerstrom S, Astback J, Ekstrand KD. A retrospective long term study of teeth restored with prefabricated carbon fiber reinforced epoxy resin posts. Swed Dent J 2006;30:1-8. 6. Jung RE, Kalkstein O, Sailer I, Roos M, Hämmerle CH. A comparison of composite post buildups and cast gold post-and-core buildups for the restoration of nonvital teeth after 5 to 10 years. Int J Prosthodont 2007;20: 63-9. 7. Bitter K, Eirich W, Neumann K, Weiger R, Krastl G. Effect of cleaning method, luting agent and preparation procedure on the retention of fibre posts. Int Endod J 2012;45:1116-26. 8. Perdigão J, Gomes G, Augusto V. The effect of dowel space on the bond strengths of fiber posts. J Prosthodont 2007;16:154-64. 9. Standlee JP, Caputo AA, Hanson EC. Retention of endodontic dowels: Effects of cement, dowel length, diameter, and design. J Prosthet Dent 1978;39: 401-5. 10. Morgano SM, Rodrigues AHC, Sabrosa CE. Restoration of endodontically treated teeth. Dent Clin N Am 2004;48:397-416. 11. Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet Dent 1984;51:780-4. 12. Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont 1995;8:155-61. 13. Torbjörner A, Karlsson S, Ödman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995;73:439-44. 14. Morgano SM, Brackett SE. Foundation restorations in fixed prosthodontics: current knowledge and future needs. J Prosthet Dent 1999;82:643-57. 15. Gomez-Polo M, Llido B, Rivero A, del Rio J, Celemin A. A 10-year retrospective study of the survival rate of teeth restored with metal prefabricated posts versus cast metal posts and cores. J Dent 2010;38:916-20. 16. Naumann M, Koelpin M, Beuer F, Meyer-Lueckel H. 10-year survival evaluation for glass-fiber-supported postendodontic restoration: a prospective observational clinical study. J Endod 2012;38:432-5. 17. Naumann M, Blankenstein F, Kiebling F, Dietrich T. Risk factors for failure of glass fiber-reinforced composite post restorations: a prospective observational clinical study. Eur J Oral Sci 2005;113:519-24. 18. Naumann M, Sterzenbach G, Alexandra F, Dietrich T. Randomized controlled clinical pilot trial of titanium vs. glass fiber prefabricated posts: preliminary results after up to 3 years. Int J Prosthodont 2007;20:499-503. 19. Eckerbom M, Magnusson T. Restoring endodontically treated teeth: a survey of current opinions among board-certified prosthodontists and general dental practitioners in Sweden. Int J Prosthodont 2001;14:245-9. 20. Kon M, Zitzmann NU, Weiger R, Krastl G. Postendodontic restoration: a survey among dentists in Switzerland. Schweizer Monatsschrift fur Zahnmedizin 2013;123:1076-88. 21. Naumann M, Kiessling S, Seemann R. Treatment concepts for restoration of endodontically treated teeth: a nationwide survey of dentists in Germany. J Prosthet Dent 2006;96:332-8. 22. Seow LL, Toh CG, Wilson NH. A survey of current practices among general dental practitioners in Manchester in 2002. Primary Dental Care 2003;10: 87-92. 23. Morgano SM, Hashem AF, Fotoohi K, Rose L. A nationwide survey of contemporary philosophies and techniques of restoring endodontically treated teeth. J Prosthet Dent 1994;72:259-67. 24. Lovdahl PE, Nicholls JI. Pin-retained amalgam cores vs. cast-gold dowelcores. J Prosthet Dent 1977;38:507-14. 25. Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J Prosthet Dent 1979;42: 39-44. 26. Ferrari M, Cagidiaco MC, Goracci C, Vichi A, Mason PN, Radovic I, et al. Long-term retrospective study of the clinical performance of fiber posts. Am J Dent 2007;20:287-91. Corresponding author: Dr Sumitha Nazar Ahmed Department of Operative Dentistry UNC School of Dentistry Chapel Hill, NC Email: [email protected] Acknowledgments The authors thank Dr Ceib Phillips for her support in creating the teleform survey and help with the statistical analysis. Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.
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