A pilot survey was sent to a group of local dentists whose feedback was incorporated into the final 35-questions survey. An invitation to participate in the online survey was e-mailed to all 149 dentists from different dental specialties, working in different clinical centers in Riyadh and are attending 26^th Saudi Dental Society International Dental Conference and 130 undergraduate students from different Dental Colleges in Riyadh. The study was conducted in Alfarabi College with ethical approval number 236/2015, consent was obtained from the participants.

This survey was divided into 3 categories in the following order [Table/Fig-1]:

SPSS software is used for this simple statistical analysis. Chi-square test and one-way ANOVA (analysis of variance) at the significance level of α=0.05 were performed to compare between results of questions (1-18) of postgraduate dentists and undergraduate dental students and analysing all results of remaining 17 questions for dentists only in Riyadh area all results are highly significant (p<0.0001).

One hundred eighteen out of one hundred forty nine dentist of different responded to the survey, representing a 79% response rate and the same number of students out of 130 responded also representing 90.7% response rate. 75% of dentist participants were females.

Results of demographic data, current professional status and experience years are presented in [Table/Fig-2]. The difference between genders was statistically significant (p < 0.0001)

Part I: Comparing first 18 questions answered by dentists and students

[Table/Fig-4]:

Most frequent files and alloy of manufacture with SEF.

[Table/Fig-5]:

Most frequent SEF size.

[Table/Fig-6]:

Which part and stage of root canal most commonly with SEF.

[Table/Fig-7]:

Most frequent causes of SEF.

(A) Most frequent files and alloy of manufacture with SEF. Statistically significant difference observed (P<0.0001). (B) Most frequent SEF size. Statistically significant difference observed (P<0.0001). (C) Most common part of root canal and stage of treatment affected by SEF. Statistically significant difference observed (P<0.0001). (D) Causes of SEF. Statistically significant difference observed (P<0.0001).

[Table/Fig-8]:

Root canal morphology as a cause of SEF.

[Table/Fig-9]:

Most common teeth with SEF.

[Table/Fig-10]:

Root canals with SEF. Management options for SEF

(A) Root canal anatomy and morphology as one cause of SEF. Statistically significant difference observed (p<0.0001). (B) Most frequently affected teeth with SEF. Statistically significant difference observed (p<0.0001). (C) Root canals with SEF. Statistically significant difference observed (p<0.0001). (D) Management options of SEF. Statistically significant difference observed (p<0.0001).

Part II: Analysing results of 17 questions for dentists only. Using chi-square test found that all results are highly significant (p<0.0001)

Treatment options:

Follow up and prognosis:

This is a cross-sectional and retrospective clinical study aimed to compare the incidence, factors contributing to separate endodontic files between dentists and undergraduates and analysing results of treatment options, management mishaps and prognosis of separated endodontic files during endodontic treatment among dentists in Riyadh area. The response rate among dentists was 79% and 90.7% among students. Every question had a different number of total respondents, suggesting that participants chose freely which questions they felt comfortable answering.

A 57.6% of dentists and 7.6% of dental students broke files during RCT. Gandevivala et al., reported that the prevalence of broken instruments during RCT ranges from 0.5% to 5% [2]. An 87% of dentists and 98% of students informed their patients about file separation that corresponds with Choksi et al., reported that the patient should be informed about SEF when breakage occurs clinically during root canal treatment (p<0.001) [20]. A 59% of dentists and 58% of students informed patients and completed treatment in another appointment while (41%) of dentists and (42%) of students. Informed patients and completed treatment in the same visit that corresponds with Simon et al., that reported if the location of SEF and canal contamination precludes easy removal or bypass, then treatment should be completed in the same visit, or it will be postponed to another appointment [11]. A 70% of dentists and 88% of students agree and thought that file separation impact and hinder proper preparation of root canal space corresponds with those of Choksi et al., and Vivekananda et al., [20,21].

The higher percentage of separation cases with dentists and students were of stainless steel files followed by Ni-Ti files and hand files followed by rotary files that against Mukhtar et al. , that reported that- the incidence of separated instruments has increased with the increased use of nickel-titanium (Ni-Ti) instruments hand or rotary [22] while Simon et al. , reported that Ni-Ti instruments are not more fragile than a stainless steel instrument of equivalent size [11]. Fractured instruments occurred long before the introduction of rotary Ni-Ti instruments. Small size files are more separated (81%) that corresponds with Choksi et al. , reported that small endodontic instruments (size 15, 20) are more prone to distortion as a result of stressing on their small cross sections [20]. Gencoglu and Helvacioglu reported that rotary instruments size #25.04 were the most fractured rotary instruments at a length of 2.5 mm because they are the most common MAF size [23]. (73%) of SEF were in apical third of root canal, (78%) of SEF during cleaning and shaping of root canal, (45%) of causes of SEF were root canal anatomy and (66%) occurred in curved canals (p<0.001) corresponds with Madarati et al., reported that the risk of SEF in the apical third of the canal is higher when compared to coronal and middle thirds that is because of most curved canals are narrow and the contact surface with the dentinal walls increases with curvature increase so that files undergo greater fatigue that lead to separation [24]. Choksi et al., reported that Curved and narrow canals have a higher risk of instrument fracture than straight and wide canals [20].

A 94% of SEF more separated in molars, 66% of SEF in Mesiobuccal canal followed by 24% Mesiolingual canal corresponding with Madarati et al., reported a higher prevalence of SEF has been reported in molars particularly in the mesial roots of mandibular molars [24].

Dentists and students faced SEF either referred cases to specialists (36%), successfully bypassed 31%, 27% successfully removed or 6% left inside root canal with true blockage. That corresponds with Gandevivala et al., reported that when an instrument fractures during root canal preparation [2], there are three basic management options: (i) Remove it; (ii) Bypass and seal it within the root canal; or (iii) block the root canal with it (p<0.0001).

A 44% of dentists bypassed SEF and 53% could successfully remove SEF from coronal third Gencoglu and Helvacioglu reported that 100% success rate for removal and bypassing the SEF obtained in coronal third of the all canals [23]. The success rate was the lowest in the apical third. A 42% of dentists could successfully remove SEF using ultrasonics under visualization of operating microscope while 23% successfully used conventional methods (p<0.0001) corresponding with Gencoglu and Helvacioglu which confirmed that ultrasonic with the aid of an operating dental microscope is more successful in removing fractured instruments than conventional methods [23]. A 71% of dentists used EDTA as a chelating agent during bypassing or removal of SEF corresponding with Jadhav that reported that the use of EDTA facilitate SEF negotiation with files as it is used to soften the root canal wall dentin around separated instruments [25].

All dentists in this study while trying to remove or bypass the separated instrument produced ledges, perforations, over enlargement of the canal, canal irregularities and apical transportation that corresponds with Choksi et al., that reported that attempting to remove or bypass SEF can lead to ledge formation, over enlargement, canal transportation and perforation [20].

(73%) of retained SEF cases showed good prognosis that against Gandevivala et al., reported that the fractured segment always accompanied with bacteria and dentine debris which considered as a foreign object that cause inflammation and so treatment failure [2]. But corresponding with Vivekananda et al., that reported that a retained instrument had no influence on the outcome of endodontic treatment, few studies have found reduced success rate [21].

A 69% of SEF cases showed good prognosis when separation happened after complete cleaning and shaping, 77% were with vital pulp tissue, 88% were with normal periapical tissue before separation and 68% of SEF found in the apical third of root canal (p<0.001). A 70% of poor prognosis cases were with periapical abcess before separation, 54% of SEF happened during canal negotiation stage that prevented complete cleaning and shaping, 55% of SEF were in the middle third of root canal beyond canal curvature or at its level, 82% of cases were with non-vital pulp tissue corresponding with Vivekananda et al. , that reported that the main prognostic factor in SEF cases is the presence or absence of a pre-operative periradicular pathosis [21].

Successful prognosis is affected by the evaluation of the pulp status, the root canal infection, the root canal anatomy, the position and type of fractured instrument and the amount of damage that would be caused to the remaining tooth structure. Chauhan et al., reported that a retained fractured instrument inside the root canal without complete obturation and coronal seal allows micro-organisms to penetrate inside the canal developing periapical lesion and so treatment failure [26].

Incidence of separated endodontic files (SEF) among dentists was higher than students this is due to the more cases they treat than students. The higher percent of students referred SEF cases while dentists tried to remove or bypass the SEF.

The higher percent of SEF were hand stainless steel more than Ni-Ti rotary files and of small size files. SEF more separated in apical third during root canal preparation due to root canal anatomy more of curved canals in molar teeth especially in mesiobuccal and mesiolingaul canals.

Dentists faced this problem reported that the most successful method for SEF removal was ultrasonics under visualization of operating microscope. They also successfully bypassed small size SEF using another small size files or left SEF inside the root canal and followed the cases but this depended on the pulp status, periapical tissue and lamina dura state before separation of the endodontic files. While trying to remove or bypass SEF dentists reported that the higher percentages of errors were ledges then perforations, over enlargement of root canal and apical transportation.

Dentists reported that the good prognosis cases were of vital pulp tissue, normal periapical tissue and lamina dura before separation problem occurs and all of poor prognosis cases were in contrary with these situations.