Abstract
Few studies have examined the longevity of endodontically treated teeth in nonacademic clinical settings where most of the population receives its care. This study aimed to quantify the longevity of teeth treated endodontically in general dentistry practices and test the hypothesis that longevity significantly differed by the patient’s age, gender, dental insurance, geographic region, and placement of a crown and/or other restoration soon after root canal treatment (RCT). This retrospective study used deidentified data of patients who underwent RCT of permanent teeth through October 2015 in 99 general dentistry practices in the National Dental Practice-Based Research Network (Network). The data set included 46,702 patients and 71,283 RCT permanent teeth. The Kaplan–Meier (product limit) estimator was performed to estimate survival rate after the first RCT performed on a specific tooth. The Cox proportional hazards model was done to account for patient- and tooth-specific covariates. The overall median survival time was 11.1 y; 26% of RCT teeth survived beyond 20 y. Tooth type, presence of dental insurance any time during dental care, placement of crown and/or receiving a filling soon after RCT, and Network region were significant predictors of survival time (P < 0.0001). Gender and age were not statistically significant predictors in univariable analysis, but in multivariable analyses, gender was significant after accounting for other variables. This study of Network practices geographically distributed across the United States observed shorter longevity of endodontically treated permanent teeth than in previous community-based studies. Also, having a crown placed following an RCT was associated with 5.3 y longer median survival time. Teeth that received a filling soon after the RCT before the crown was placed had a median survival time of 20.1 y compared to RCT teeth with only a crown (11.4 y), only a filling (11.2 y), or no filling and no crown (6.5 y).
Keywords: retrospective studies, big data, dental informatics, data science, electronic health records, electronic dental record
Introduction
Root canal treatment (RCT) continues to be an important treatment to maintain natural teeth affected by pulpal or periapical diseases. Conserving the natural dentition and supporting essential oral functions throughout old age is a major goal of dental care with the increased life span of the population (Johnstone and Parashos 2015). Therefore, the need for long-term studies of endodontically treated teeth is essential (Pirani et al. 2015; Prati et al. 2018), especially in common, nonacademic clinical settings where most of the population receives its care. The establishment of practice-based research networks has enabled the study of treatment outcomes by accessing practices’ electronic dental treatment documentation.
Existing studies reported high success rates of endodontically treated teeth performed in academic and large health care settings and among insured populations (Ng et al. 2008; Paredes-Vieyra and Enriquez 2012; Jordal et al. 2014; Petersson et al. 2016; Chatzopoulos et al. 2018; Pirani et al. 2018). However, substantial variations exist in the definitions of treatment success in these studies. These definitions included radiographic evidence of periapical tissue healing following treatment, reduction in the periapical radiolucency, and tooth survival (Pirani et al. 2015; Gomes et al. 2017; Chatzopoulos et al. 2018). For example, the mean success rates ranged from 31% to 96% (Ng et al. 2007) when RCT success was defined as the absence of apical periodontitis clinically and radiographically. The mean success rates were 60% to 100% when success was based on defining success as a reduction in the periapical lesion size (Ng et al. 2007).
With the emergence of the single-tooth implant restoration as an alternative to RCT, tooth survival has become an important outcome by which to compare RCT success to single-tooth implant success (Chatzopoulos et al. 2018). Tooth survival is especially salient as an outcome given that RCT teeth can be lost for reasons other than just the RCT, such as caries, periodontal disease, tooth fractures, and prosthodontic failures that develop after RCT. Moreover, tooth survival rates can assist clinicians with assessing tooth-specific prognosis, treatment planning activities, and communicating these topics in lay language with patients. A meta-analysis of 31 studies revealed the pooled probability of tooth survival 8 to 10 y after RCT ranged from 86% to 93% (Ng et al. 2010). Subsequently, large studies using private or public claims data have reported 84% to 97% survival after 3 to 8 y of follow-up (Salehrabi and Rotstein 2004; Fransson et al. 2016).
While claims data provide important insights (Salehrabi and Rotstein 2004; Fransson et al. 2016), they have shortcomings (Hyman 2015). A key limitation is that their analysis only allows study of populations who have dental insurance. Other drawbacks typically include absence of diagnosis and an inability to evaluate the quality of the data due to limited information reported in claims data (Hyman 2015; Kebke et al. 2021). Furthermore, most RCT outcome studies have been performed in academic and specialty practice settings, which limits their generalizability to community-based general dentistry settings (Lee et al. 2012; Pirani et al. 2015; Chatzopoulos et al. 2018). Using electronic dental record (EDR) data gathered in community dental practices offers an opportunity to improve the generalizability of studies regarding the longevity of RCT teeth (Gilbert et al. 2010; Bernstein et al. 2012).
The National Dental Practice-Based Network (Network) offers a unique opportunity to use EDR data to obtain a national scope of long-term treatment outcomes (Gilbert et al. 2013). An assessment of the Network practices’ data (Thyvalikakath et al. 2020) demonstrated their feasibility to study the longevity of endodontically treated permanent teeth performed in these settings. The objective of this study was to 1) quantify the longevity of teeth treated endodontically in general dentistry practices and 2) test the hypothesis that longevity significantly differed by the patient’s age, gender, dental insurance status, placement of crown and/or other restoration soon after RCT, and geographic region. This study takes advantage of general dental practice data from 2 different EDR systems (Dentrix and EagleSoft), the procedures for which are described in detail in a published article (Thyvalikakath et al. 2020).
Methods
We recruited 99 Network practices that consisted of small group and solo general dentistry practices who had used Dentrix (Henry Schein One) or EagleSoft (Patterson Dental) for at least 5 y to maintain electronic clinical documentation of at least existing conditions and treatment performed. In addition, these practices performed at least 1 RCT on a permanent tooth in at least 50 patients, had follow-up data for at least 2 y, and continued performing these procedures between January 1, 2000, and October 31, 2015. As described in a previous article (Thyvalikakath et al. 2020), we received deidentified data of patients who underwent RCT of permanent teeth through October 2015 from these practices. This data set included 46,702 patients and 71,283 RCT permanent teeth, identified using procedure codes (D3310, D3320, D3330). The data required to perform survival analysis, such as the tooth type and dates of treatment, were present for all patients.
Descriptive statistics were performed to report patient demographics, number of patient records included from the 6 Network regions, and the number of RCT teeth by tooth type. For 85% of the individuals who had at least some post-RCT follow-up data, the Kaplan–Meier (product limit) estimator was performed to estimate the survival rate after the first RCT performed on a specific tooth. This method considered the right-censored data, which occurred if the patient did not receive a second RCT on the tooth. We also analyzed the data set with Cox proportional hazards models that account for multiple explanatory covariates: age, gender, tooth type (anterior, bicuspid, molar), presence of dental insurance, receipt of a crown and/or other restoration on the RCT-treated tooth soon after RCT, and Network region. No model selection was performed; variables included in the model were patient and tooth factors previously reported as possibly affecting RCT longevity and readily available within the EDR. Some individuals had more than 1 RCT performed on different teeth; to account for this correlation within the same patient, we considered the marginal Cox model for clustered data. The Tukey method was used to adjust for multiple comparisons. The data allowed us to account for a procedure on the same tooth, which might indicate that the subsequent procedure was a failure. These failure types included procedure codes (D3300s) for any endodontic treatment (including retreatment) after the first RCT code, apicoectomy (D3400s), root amputation (D3450), root extraction (D7250), simple (D7100s) and surgical (D7200s) tooth extraction, fixed prosthodontic pontics (D6200), dental implant body (D6010), and removable dentures that included the RCT tooth (D5000). In addition, specific conditions listed following the first RCT code—namely, missing tooth or crown, root tips, and retained root tips—were included as failure types. The following procedure codes that indicated restorations were included as covariates: amalgam restorations (D2100), resin restorations (D2300), inlays and onlays (D2500 and D2600), and core buildup with pin retention and cast post and core and prefabricated post in addition to crown (D2900). We analyzed the data using the software SAS, version 9.4 (SAS Institute). The methods described are in compliance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist for cohort studies.
Results
Tables 1 to 3 display the numbers of patients, tooth types, and follow-up periods included in the analyses. Appendix Table 1 displays the number of Network practices and number of teeth with the RCT procedure across the 6 regions.
Table 1.
Demographics of Patients Who Received a Root Canal Treatment (RCT) of Permanent Teeth in the 99 Network Practices through October 2015, by Age Group and Gender.
| Age Group, y | Female, n (%) | Male, n (%) | Total, N (%) |
|---|---|---|---|
| Less than 18 | 1,360 (52) | 1,280 (48) | 2,640 (6) |
| 18–44 | 11,989 (58) | 8,729 (42) | 20,718 (44) |
| 45–64 | 9,834 (54) | 8,267 (46) | 18,101 (39) |
| 65 or older | 2,636 (50) | 2,605 (50) | 5,241 (11) |
| Total | 25,819 (55) | 20,881 (45) | 46,700 (100) |
Table 3.
Electronic Dental Record Data Duration between First Root Canal Treatment and Last Visit and the Number of Patient Records and Teeth Present during Each Time Duration.
| Time, y | Number (%) of Patients (n = 46,700) | Number (%) of Teeth (n = 71,258) |
|---|---|---|
| 0 y (1 visit) | 3,627 (7.8) | 4,348 (6.1) |
| Up to 5 y | 2,858 (61.2) | 40,694 (57.11) |
| >5 and ≤10 y | 8,893 (19.0) | 15,211 (21.4) |
| >10 and ≤15 y | 4,319 (9.3) | 8,242 (11.6) |
| >15 and ≤20 y | 1,134 (2.4) | 2,446 (3.4) |
| >20 y | 142 (0.3) | 317 (0.4) |
While 15% of the patients did not report any follow-up after their first visit, 35% had an observation time up to 5 y, 40% from 6 to 15 y, and 11% more than 15 y.
Table 2.
Number of Root Canal Treated Permanent Teeth in the 99 General Dental Network Practices, by Tooth Type and Location (Maxillary and Mandibular Arches).
| Tooth Type | Maxillary, n (%) | Mandibular, n (%) | Total, N (%) |
|---|---|---|---|
| Anterior | 10,721 (76) | 3,419 (24) | 14,140 (20) |
| Premolar | 14,077 (59) | 9,630 (41) | 23,707 (33) |
| Molar | 14,318 (43) | 19,093 (57) | 33,411 (47) |
| Total | 39,116 (55) | 32,142 (45) | 71,258 (100) |
The overall median survival time was 11.1 y (10.7–11.5), with 26.1% of root canals estimated to survive beyond 20 y (Table 4 and Appendix Fig. 1a–h). Tooth type, presence of dental insurance, placement of crown after the RCT, having a filling soon after the RCT but prior to a crown, and Network region were all found to be significant predictors of survival time (P < 0.0001). Gender and age were not statistically significant predictors in the univariable analysis.
Table 4.
Kaplan–Meier Statistics Estimating the Survival Time of 71,258 Root Canal Treated Permanent Teeth in 46,700 Patients from 99 General Dentistry Network Practices.
| Variable | Level | Median (95% CI), y | P Value | Estimated Survival Percentage | ||
|---|---|---|---|---|---|---|
| 5 y | 10 y | 20 y | ||||
| Overall | 11.1 (10.7–11.5) | 75.4 (74.5–76.3) | 53.7 (52.2–55.2) | 26.1 (22.6–29.6) | ||
| Age, y | 18–44 | 10.5 (9.5–11.2) | 72.7 (70.7–74.7) | 52.1 (48.3–55.8) | NA | |
| 45–64 | 10.8 (10.4–11.6) | 75.6 (74.3–76.9) | 53.1 (51.0–55.2) | 23.3 (18.6–28.0) | ||
| 65 or Older | 10.7 (10.0–11.8) | 74.8 (73.1–76.4) | 52.4 (49.8–55.0) | 30.2 (25.1–35.2) | ||
| Less than 18a | 10.8 (NA) | 0.0621 | 63.6 (54.3–72.8) | 60.0 (49.0–71.1) | NA | |
| Gender | Male | 10.6 (9.9–11.2) | 74.4 (73.1–75.7) | 52.0 (49.8–54.1) | 21.9 (16.4–27.4) | |
| Female | 11.6 (11.0–12.1) | 0.059 | 76.2 (75.1–77.4) | 55.1 (53.2–57.1) | 29.7 (25.2–34.2) | |
| RCT tooth type | Anterior | 12.4 (11.5–13.3) | 79.4 (77.7–81.1) | 57.7 (54.7–60.6) | 27.5 (20.4–34.6) | |
| Premolar | 10.3 (9.7–11.0) | 73.6 (71.9–75.2) | 51.0 (48.4–53.7) | 27.7 (22.4–32.9) | ||
| Molar | 11.0 (10.5–11.7) | <0.0001 | 74.6 (73.3–75.0) | 53.4 (51.3–55.6) | 24.4 (18.8–29.9) | |
| Dental insurance | Yes | 10.6 (9.9–11.1) | 74.6 (73.1–75.9) | 51.8 (49.4–54.2) | 15.4 (8.8–22.0) | |
| No | 8.7 (8.0–9.1) | <0.0001 | 67.9 (65.9–70.0) | 42.9 (40.0–45.9) | NA | |
| Crown placed following RCT | Yes | 13.7 (13.0–14.5) | 85.7 (84.7–86.7) | 65.4 (63.3–67.5) | 35.0 (29.1–40.9) | |
| No | 8.4 (8.0–8.8) | <0.0001 | 65.6 (64.3–66.9) | 43.9 (41.2–45.0) | 18.5 (14.6–22.4) | |
| Filling before crown | Yes | 20.1 (15.5–24.7) | 92.3 (90.3–94.3) | 77.0 (72.2–81.7) | 51.0 (36.3–65.8) | |
| Crown only | 11.4 (10.9–12.0) | 77.2 (76.2–78.3) | 55.5 (53.7–57.3) | 26.8 (22.5–31.2) | ||
| Filling only | 11.2 (9.2–13.5) | 75.1 (73.5–78.7) | 52.6 (48.5–56.8) | 27.3 (17.4–37.2) | ||
| No filling and no crown | 6.5 (5.8–7.1) | <0.0001 | 55.9 (53.3–58.6) | 33.8 (30.3–37.4) | 8.3 (1.7–14.9) | |
| Network region | West | 8.7 (7.7–9.9) | 70.9 (67.9–73.9) | 43.0 (37.7–48.4) | NA | |
| Midwest | 11.2 (10.2–12.0) | 76.8 (74.8–78.9) | 54.1 (50.5–57.8) | 18.1 (8.9–27.3) | ||
| Southwest | 11.2 (10.1–12.4) | 75.9 (73.8–77.9) | 54.1 (50.6–57.5) | NA | ||
| South Central | 9.0 (8.3–9.7) | 69.7 (67.7–71.8) | 45.5 (42.2–48.8) | NA | ||
| South Atlantic | 9.1 (8.7–9.9) | 70.1 (67.9–72.3) | 45.8 (42.3–49.3) | 19.2 (13.0–25.4) | ||
| Northeast | 20.5 (18.6–22.4) | <0.0001 | 89.8 (88.3–91.3) | 76.1 (73.2–79.0) | 55.4 (48.4–62.4) | |
CI, confidence interval; NA, not available for this subgroup; RCT, root canal treatment.
More specifically, RCT premolars were found to have a median survival time of 10.3 y while anterior teeth had a median time of 12.4 y. Patients having dental insurance at some time during a patient’s EDR treatment history showed median survival times of RCTs of almost 2 y longer than those with no history of dental insurance. Having a crown placed after an RCT was associated with a 5.3-y longer median survival time, and having a filling placed after the RCT but before the crown showed a median survival time of 20.1 y compared to 11.4 y when only a crown was placed, 11.2 y when only a filling was placed, and 6.5 y when neither a filling nor crown was placed after the RCT. The Northeast region of the United States had a significantly longer median survival time (20.5 y) compared to the Midwest (11.2 y), Southwest (11.2 y), South Atlantic (9.1 y), South Central (9.0 y), and West (8.7 y) regions (Table 4 and Appendix Fig. 1a–h).
Multivariable analyses showed similar results (Table 5); however, gender was found to be significant when accounting for the other variables. Having RCT on an anterior tooth versus a premolar tooth or an anterior versus a molar showed similar hazard ratios. This indicates that a premolar or molar RCT is 1.64 (1.0 ÷ 0.61) times more likely to fail at any given time when compared with an anterior RCT. No difference was found between premolar and molar teeth (P = 0.9831). RCTs in male patients were found to be 1.1 times more likely to fail than female patients at any given time point (P = 0.006). Not having dental insurance indicates that a patient’s RCT is 1.2 (1.0 ÷ 0.83) times more likely to fail than those with dental insurance (P < 0.0001). No significant differences were found between the following regions by comparison: West versus Midwest (P = 0.9995), West versus Southwest (P = 0.9989), Midwest versus Southwest (P = 0.9475), and South Central versus South Atlantic (P = 0.9915). The largest difference was found between South Atlantic versus Northeast; a patient’s RCT in the South Atlantic region was 2.0 times more likely to fail than in the Northeast (P < 0.0001). Finally, an RCT with no final restoration versus 1 with a filling placed and later a crown was found to be 2.94 (1.0 ÷ 0.34) times more likely to fail at any given time point (P < 0.0001). Harrell’s concordance statistic estimate is 0.71.
Table 5.
Multivariable Cox Model for Root Canal Treated Teeth by Crown, Dental Insurance, Tooth Type, Gender, Filling before Crown, and Network Region.
| Covariate | Omnibus P Value | Level | Hazard Ratio (95% CI) | Adjusted P Value |
|---|---|---|---|---|
| Tooth type | <0.0001 | Anterior vs. premolar | 0.61 (0.54–0.69) | <0.0001 |
| Anterior vs. molar | 0.61 (0.55–0.69) | <0.0001 | ||
| Premolar vs. molar | 1.01 (0.92–1.10) | 0.9831 | ||
| Gender | 0.0066 | Female vs. male | 0.90 (0.83–0.97) | 0.0066 |
| Dental insurance | <0.0001 | Yes vs. no | 0.83 (0.77–0.90) | <0.0001 |
| Network region | <0.0001 | West vs. Midwest | 0.98 (0.83–1.14) | 0.9995 |
| West vs. Southwest | 1.03 (0.89–1.19) | 0.9989 | ||
| West vs. South Central | 0.79 (0.68–0.91) | 0.0190 | ||
| West vs. South Atlantic | 0.76 (0.64–0.90) | 0.0140 | ||
| West vs. Northeast | 1.52 (1.23–1.89) | 0.0016 | ||
| Midwest vs. Southwest | 1.06 (0.94–1.19) | 0.9475 | ||
| Midwest vs. South Central | 0.81 (0.72–0.91) | 0.0049 | ||
| Midwest vs. South Atlantic | 0.78 (0.68–0.90) | 0.0076 | ||
| Midwest vs. Northeast | 1.56 (1.29–1.90) | <0.0001 | ||
| Southwest vs. South Central | 0.77 (0.69–0.54) | <0.0001 | ||
| Southwest vs. South Atlantic | 0.74 (0.65–0.84) | <0.0001 | ||
| Southwest vs. Northeast | 1.48 (1.23–1.79) | 0.0006 | ||
| South Central vs. South Atlantic | 0.96 (0.84–1.10) | 0.9915 | ||
| South Central vs. Northeast | 1.93 (1.60–2.32) | <0.0001 | ||
| South Atlantic vs. Northeast | 2.00 (1.64–2.46) | <0.0001 | ||
| Crown | <0.0001 | Yes vs. no | 0.45 (0.41–0.50) | <0.0001 |
| Filling | <0.0001 | Filling before crown vs. crown only | 0.67 (0.54–0.85) | 0.0039 |
| Filling before crown vs. filling only | 0.92 (0.70–1.20) | 0.9171 | ||
| Filling before crown vs. no final restoration | 0.34 (0.29–0.48) | <0.0001 | ||
| Crown only vs. filling only | 1.36 (1.19–1.56) | <0.0001 |
Discussion
This study observed substantial tooth-specific longevity following RCT from general dentistry practices. It also demonstrated a strong association between this longevity and restoration of the tooth following RCT, as well as a gradient in longevity based on whether the tooth received a filling plus crown, a crown only, a filling only, or no restoration. The highest longevity was observed among RCT teeth that had a filling placed after the RCT but before a subsequent prosthetic crown was placed on the tooth.
These results suggest a lower survival time (median time of 11.1 y) of RCT teeth than previously reported in most studies. There are several reasons that might account for lower survival times observed in this study. These could include 1) larger heterogeneity of the participating practices and patient population in this study that had a national scope; 2) greater diversity due to its inclusion of both dentally insured and uninsured patient populations; 3) its inclusion of more dental codes than other studies that identify that the tooth was removed (fixed prosthodontic pontic, removable partial denture, implant body, tooth hemisection); 4) fewer crown placements among the patients who received RCT, owing to its inclusion of dentally uninsured patients; 5) differences in dental insurance coverage and procedures covered across the 6 network regions; 6) RCTs were done by general dentists rather than endodontic specialists in this study; and 7) regional differences in patients’ health literacy, follow-up care, and preventive behaviors.
Previous studies conducted in academic or specialist private practice settings and using dental insurance claims data reported higher survival rates. For example, large dental insurance claims data studies of RCT have reported 98% tooth survival at 1 y, 92% at 5 y, and 86% at 10 y (Burry et al. 2016); 97% tooth survival after 8 y (Salehrabi and Rotstein 2004); 94% after a mean follow-up time of 3.5 y (Lazarski et al. 2001); 84% at 3 y (Raedel et al. 2015); and 93% after 5 y (Chen et al. 2007). Studies conducted in community practice settings with incomplete dental insurance coverage have largely reported lower survival times than their counterparts (Tilashalski et al. 2004; Gilbert et al. 2010; Ng et al. 2010; Bernstein et al. 2012; Kebke et al. 2021), which is confirmed in this larger national study of RCT performed in community practices.
The current study was limited to general dentistry practices. Some previous studies observed longer survival times when RCT was done by endodontic specialists rather than general dentists (Alley et al. 2004; Burry et al. 2016), although others have not while acknowledging a more complex case mix for endodontists (Lazarski et al. 2001). A retrospective study from 1 general dentistry practice in Germany observed that 6% of 795 RCT teeth were extracted during a mean observation period of 4.5 y, although an eligibility criterion was that all teeth received a restoration within 6 months of the RCT (Skupien et al. 2013). Given that general dentists tend to refer teeth for which they anticipate more challenging treatment, survival times may be expected to be longer on average for RCT teeth treated by general dentists as compared to endodontists. Nevertheless, survival times are also dependent on multiple factors as described above.
It is also noteworthy that this study demonstrated that meaningful insights can be gained through the analysis of existing dental practice data from routine electronic dental records. Our use of dental practice data differs from other dental outcome studies in at least 2 important ways. First, because participating practices were geographically distributed across the United States, we were able to study a larger, more diverse set of patients. To the best of our knowledge, this study is the first to determine the survival rates of endodontically treated teeth with a large patient cohort of US community-based practices not limited to patients with dental insurance.
Our use of practice data gave us the means to compare outcomes between insured and noninsured patients. Anecdotal reports indicate significant geographic differences in dental insurance coverage. For instance, Medicaid in Indiana does not reimburse for crown placement, and although small companies may provide dental insurance to their employees in the Northeast United States, dental insurance may not be available for employees working in small companies in other Network regions, such as the South Atlantic, South Central, and Midwest regions. Thus, to improve health outcomes for all patients, it may be important to include both insured and noninsured patients. It is also possible that there are regional differences in case selection, such as the clinician’s decision to proceed with RCT on teeth that may be technically difficult or involved periodontally. A key finding from this study is the gradient in longevity based on whether the tooth received a filling plus crown, a crown only, a filling only, or no restoration. Comparable findings have been observed in insured populations (Chen et al. 2007) and a dental school clinic (Pratt et al. 2016).
Our study found longer survival times for RCTs performed on anterior teeth as compared to both premolars and molars (Table 5) but no significant difference between molars and premolars. Similar results have been observed in other studies in the literature (Lazarski et al. 2001), although 1 study observed higher longevity in multirooted teeth (Raedel et al. 2015), a systematic review reported mixed results (Ng et al. 2010), and a large study from Taiwan observed higher survival rates in anterior and premolar teeth as compared to molars (Chen et al. 2007).
The results also characterized differences in the survival time by age, gender, tooth type, placement of a crown following RCT, the patient’s dental insurance status, and Network region. All differences except by age were statistically significant. In the sections below, we highlight the clinical significance of these results, study strengths, limitations, and future work.
Females had significantly longer survival times for their RCTs, once other covariates had been considered. An insurance claims study observed no difference by gender (Lazarski et al. 2001), as did a study of dental school patients (Chatzopoulos et al. 2018) and a systematic review (Ng et al. 2010). The current study considered receipt of restorative care and dental insurance in the multivariable model, so we speculate that the gender difference could be due to higher adherence to treatment recommendations (e.g., follow-up care or dental hygiene) than males (Manteuffel et al. 2014; Siddiqui et al. 2021), but these data could not address this issue.
This study did have significant limitations. For example, we could not evaluate the association between longevity and certain practice and practitioner characteristics. Nor were practices calibrated or standardized in providing RCT or diagnostic methods used. Therefore, the possibility of unmeasured confounding variables exists. In addition, a substantial number of patients (27%) were missing insurance status (Thyvalikakath et al. 2020), and there was no information on patients’ race and ethnicity. We also could not include ratings about the quality of RCT such as obturation, root fill, placement of cast or prefabricated post, and radiologic evidence of periapical tissue healing. Nor did we have information on periodontal and periapical status at the time of RCT and whether the RCT teeth were taken out of occlusion as a sign of failed/failing RCT. We also could not obtain the reason(s) for the RCT, such as diagnosis, which is usually written in the clinical notes and not available as structured data. Last, although we determined the dental insurance status for a significant number of patients, we could not specifically determine the insurance reimbursement for RCT procedures or subsequent restorative procedures done on the RCT tooth.
Despite these limitations, our study provides a sound basis for conducting further investigations. Importantly, more research is needed regarding the factors that improve the prognosis following RCT. Such research studies should enable dental practitioners and patients to make better-informed decisions among dental treatment options, such as having a crown placed on the endodontically treated tooth versus only having a filling. We were also intrigued by the higher survival rates in the Northeast region compared to the other Network regions. We hypothesize that this is due to better dental insurance coverage and health literacy in the Northeast, but more investigation is needed. Future work should also include studying the practice-level variations in the survival analysis and studying the role of chronic medical conditions such as diabetes on the RCT survival time.
In addition to answering salient clinical questions, this study demonstrated that new clinical information already captured during the routine care process can be used to answer practical clinical questions to improve the quality of care. In the business arena, information that can be used to improve operations is highly valued and used whenever possible. The dental profession can operate in a similar manner, using the information to incorporate research and continuous quality improvement as essential components of everyday clinical practice (Gilbert et al. 2021).
Author Contributions
T. Thyvalikakath, contributed to conception, design, data acquisition, drafted and critically revised the manuscript; M. LaPradd, W.D. Duncan, contributed to design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript; Z. Siddiqui, contributed to design, data acquisition, analysis, and interpretation, drafted the manuscript; G. Eckert, contributed to conception, design, data acquisition, analysis, and interpretation, critically revised the manuscript; J.K. Medam, contributed to acquisition and data analysis, critically revised the manuscript; D.B. Rindal, contributed to conception, design, data acquisition and interpretation, critically revised the manuscript; M. Jurkovich, contributed to design, data analysis and interpretation, critically revised the manuscript; G.H. Gilbert, contributed to conception, design, data acquisition, analysis, and interpretation, drafted and critically revised the manuscript; National Dental PBRN Collaborative group, contributed to design, data acquisition, critically revised the manuscript. All authors gave final approval and agree to be accountable for all aspects of the work.
Supplemental Material
Supplemental material, sj-docx-1-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-2-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-3-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-4-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-5-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-6-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-7-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-8-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-9-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Acknowledgments
We gratefully acknowledge the practitioner participants who shared their data to conduct this study, without which this study would not have been possible. We also gratefully acknowledge the assistance of Neil Butler and Chris Wadsworth from Henry Schein and Ted Fruchtl and Jessica Knaus from Patterson Dental with extracting data from the network practices and the support of these 2 companies’ leadership for the study. We thank Dr. Anushri Rajapuri Singh for formatting the manuscript, and the Regenstrief Institute’s staff for their assistance with the project.
We are grateful to the network’s regional node coordinators, who function as the “face” of the network in recruiting, training, and interacting with the network’s practitioners (Midwest region: Tracy Shea, RDH, BSDH; West region: Stephanie Hodge, MA; Northeast region: Christine O’Brien, RDH; South Atlantic region: Hanna Knopf, BA, and Deborah McEdward, RDH, BS, CCRP; South Central region: Shermetria Massengale, MPH, CHES, and Ellen Sowell, BA; Southwest region: Stephanie Reyes, BA, Meredith Buchberg, MPH, and Colleen Dolan, MPH), as well as the network’s program manager (Andrea Mathews, BS, RDH) and program coordinator (Terri Jones)
Footnotes
A supplemental appendix to this article is available online.
Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by National Institutes of Health grants U19-DE-28717 and U19-DE-22516. Opinions and assertions contained herein are those of the authors and are not to be construed as necessarily representing the views of the respective organizations or the National Institutes of Health. This study was determined not to be human subjects research by the Indiana University Institutional Review Board (IRB). Approvals or exemptions were also obtained separately from the 6 network regions’ IRBs. The manuscript coauthors reported having no conflicts of interest. An Internet site devoted to details about the nation’s network is located at http://NationalDentalPBRN.org.
ORCID iDs: T. Thyvalikakath 
https://orcid.org/0000-0002-7294-2318
G. Eckert
https://orcid.org/0000-0001-7798-7155
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Associated Data
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Supplementary Materials
Supplemental material, sj-docx-1-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-2-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-3-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-4-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-5-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-6-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-7-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-8-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research
Supplemental material, sj-tiff-9-jdr-10.1177_00220345221093936 for Root Canal Treatment Survival Analysis in National Dental PBRN Practices by T. Thyvalikakath, M. LaPradd, Z. Siddiqui, W.D. Duncan, G. Eckert, J.K. Medam, D.B. Rindal, M. Jurkovich and G.H. Gilbert in Journal of Dental Research