Introduction: Prevalence of Fractured Instruments

Fig. 1.1

Fragments of various endodontic instruments
Fig. 1.2

(a) Fragment of an irrigation needle in the mesiobuccal root canal of a maxillary molar. (b) Fragment of the notched end of an irrigation needle in a mandibular canine
Fig. 1.3

Fragments of Lentulo spiral fillers
Fig. 1.4

(a) Root canal with an instrument fragment and a silver point fragment . (b) Mandibular molar with an instrument fragment in the distal canal and three metallic particles in the mesial canals, possibly fragments of silver points
Fig. 1.5

Fragments of: (a) Endodontic explorer . (b) Spreader . (c) Bur. (d) Gates Glidden bur (with permission from Lambrianidis 2001)
Fig. 1.6

Fragment of a prefabricated metal post
Fig. 1.7

(a) Amalgam particles in the distal root canal and an instrument fragment in the mesiobuccal canal of a second right mandibular molar. (b, c) Amalgam particles in the mesial root of suboptimally filled first mandibular left molars
More infrequently, the presence of foreign objects within the root canal is attributed to patient’s related manipulations outside the dental surgery (Figs. 1.8 and 1.9) . There are several reports related to foreign object placement into exposed pulp cavities by patients either in an effort to alleviate mid-treatment pain by exposing the chamber or as a habit. Foreign objects lodged as a habit are more commonly seen in children, as the latter often place a variety of foreign particles in their mouths. Wooden or metallic objects , such as toothpicks, sewing needles, safety pins, hat pins, dressmaker pins, stapler pins, crayons, pencil leads, toothbrush bristles, food remnants, and pieces of nails, are among the various objects of these etiologies found in the root canal of permanent teeth (Grossman 1974, Zillich and Pickens 1982, Turner 1983, Shay 1985, Chenail and Teplitsky 1987, Walvekar et al. 1995, Srivastava and Vineeta 2001, Nadkarni et al. 2002, McAuliffe et al. 2005, Aduri et al. 2009, Kalyan and Sajjan 2010, Chand et al. 2013, Patil et al. 2015). Their dimensions vary greatly. A case has been described with two objects, an 8 mm-long watch hand and a 5 mm-long pencil lead (Ozsezer et al. 2006). Moreover cases of foreign objects found in the deciduous teeth have also been described (Holla et al. 2010; Singh Dhull et al. 2013). These foreign objects, regardless of their nature, size, and location, may act as a potential source of infection. Therefore, a detailed dental history and clinical and radiographic examination are necessary to come to a conclusion about their nature, size, and location and proceed to their management accordingly.

Fig. 1.8

Sewing needle in root canal (with permission from Lambrianidis 2001)
Fig. 1.9

(a) Stapler pin placed for fun in the root canal of a maxillary central incisor of an 8-years old boy. (b) Fragment of an interdental brush in an exposed maxillary central incisor of a 32-year-old man advised by his general dental practitioner to “clean” the canal with this brush after each meal

1.2 Incidence of Fractured Instruments

In spite of the plethora of considerable metallurgical improvements in instrument design, alloy composition, and manufacturing process, file failure during instrumentation remains a primary concern. Endodontic instruments are the foreign objects most frequently found in the root canal either in retreatment cases or as a mishap in initial treatments. A literature review revealed a prevalence of retained fractured instruments of between 0.7 and 7.4% in teeth undergoing root canal treatment (RCT) (Crump and Natkin 1970; Hülsmann and Schinkel 1999; Spili et al. 2005; Iqbal et al. 2006; Parashos and Messer 2006; Cheung et al. 2007).
Instrument fracture is an undesirable and troublesome incident during RCT that frustrates both practitioners and patients. It can happen even to experienced clinicians following the most appropriate preventive measures. Instrument fracture may occur in both anterior and posterior teeth, but it is most frequently reported in molars (Iqbal et al. 2006; Wu et al. 2011; Ungerechts et al. 2014), with similar instrument fracture rates for the maxilla and the mandible (Iqbal et al. 2006; Tzanetakis et al. 2008; Ungerechts et al. 2014). Among molars, it is particularly reported as occurring in the mesial roots of mandibular molars (Molyvdas et al. 1992; Hülsmann and Schinkel 1999; Ward et al. 2003).
The vast majority of instrument fracture occurs in the apical third of the root canal (Molyvdas et al. 1992; Yared et al. 2000; Al-Fouzan 2003; Ankrum et al. 2004; Di Fiore et al. 2006; Iqbal et al. 2006; Tzanetakis et al. 2008; Ungerechts et al. 2014; Wang et al. 2014). The probability of file fracture in the apical area was estimated to be 33 times greater compared to the coronal third of the canal and almost six times greater when compared to the middle third of the root canal (Iqbal et al. 2006).
The incidence of endodontic instrument fracture is still an area of uncertainty, firstly because the numerous studies that have assessed this phenomenon offer varying and sometimes conflicting results and, secondly and most importantly, because incidence rates result from studies with several noncomparable methodologies.
The overall reported incidence rate of fractured hand instruments range between 0.25 and 6% (Crump and Natkin 1970; Hülsmann and Schinkel 1999; Spili et al. 2005; Iqbal et al. 2006). The incidence of SS hand instrument fracture among undergraduate students has been reported to be 1.8% (Kerekes and Tronstad 1979) on a tooth level and 1.3% on a root level (Sjogren et al. 1990). A lower percentage of 1% on a tooth level was reported in a retrospective investigation of the incidence of hand instrument (SS and NiTi) fracture during conservative RCT performed by undergraduate dental students over a 10-year period at the University of Bergen in Norway (Ungerechts et al. 2014). The introduction of NiTi instruments, which nowadays have become a mainstay in the vast majority of endodontic and general practices and have added a new dimension to the practice of endodontics, despite their undeniably favorable qualities, has not resulted in an elimination of the problem. The common perception is that NiTi rotary instruments have a higher failure incidence than SS hand instruments (Barbakow and Lutz 1997; Cheung et al. 2005; Iqbal et al. 2006; Wolcott et al. 2006). In contrast (Parashos and Messer 2006), based on the best available clinical evidence, they state that the frequency of fracture of rotary NiTi instruments may actually be lower than that for SS hand files. The incidence rate of fractured rotary NiTi instruments varies greatly according to the type of instrument (brand, size, taper, cross-sectional shape, and instrument design), the assessment of fracture incidence, the operator, the methodology used, and several other variables that differ among the experimental works. These differences are clearly evident in studies that have investigated the fracture incidence of rotary instruments after clinical use (Table 1.1), as well as in ex vivo studies (Table 1.2). A very low fracture incidence was found with instruments with a reciprocation motion, namely, the reciprocating WaveOne files (Cunha et al. 2014) and the Reciproc instruments (Plotino et al. 2015).

Table 1.1

Summary of characteristics of the studies on reported fracture incidence of endodontic instruments after clinical use (in chronological order)
Author(s) and year of publication
Fractured incidence (%)
Type of instrumenta
Type of practice
Information on operators
No of files used
No of uses
No of teeth/roots/root canals
Bueno et al. (2017)
WaveOne primary
Reciproc R25
60 WaveOne
60 Reciproc R25
Preparation of root canals cin up to 3 posterior teeth
358 teeth
1130 root canals
• 2.5%(3/120) in relation to instruments used
• 0.26% (3/110) in relation to r.c. treated
• 0.84% (3/358) in relation to teeth
Shen et al. (2016)
WaveOne files
 – 137 small
 – 249 primary
 – 52 large
Four specialist clinics and one graduate program
Endodontists and postgraduate students
438 files in total
0.5% (2/438) overall instrument fracture
• 0.7% (1/137) small files
• 0.4% (1/249) primary files
• No fractures in large files
Rodrigues et al. (2016)
Reciproc R25, R40, R50
No glide path
Private practice
673 r.c. in total
454 narrow (R25)
135 medium (R40)
84 large (R50)
0.44% (3/673) overall
• 0.66% (3/454) narrow r.c
• No fractures in medium r.c.
• No fractures in large r.c.
Plotino et al. (2015)
Three operators
1696 files
3780 r.c. (3023 initial treatments & 757 retreatments)
0.47% (8/1696) overall in relation to the number of instruments used and 0.21% (8/3780) overall in relation to the number of the r.c. treated
• 0.13% (5/3023) in relation to the number of r.c. shaped in initial treatments
• 0.08% (3/757) in relation to the number of r.c. shaped in retreatments
Solomonov et al. (2015)
Private practice
Endodontists and general practitioners
0.6% (15/2517)
Wang et al. (2014)
Nanjing Stomatology Hospital
24,108 r.c. of 11,036 teeth
• 2.2% (245/11,036)
in relation to the number of teeth
• 1.0% (255/24,108) in relation to the number of r.c.
Ungerechts et al. (2014)
Hand instruments (SS & NiTi)
Dent. clinic, Univ. Bergen, Norway
Undergraduate students
Retrospective review of 3854 assessment forms filled out for each RCT over a 10-year period
1.0% (38/3854) overall incidence on a tooth level
Cunha et al. (2014)
Four experienced and calibrated endodontists
711 posterior teeth (2215 r.c.)
0.42% (3/711) in relation to teeth treated
0.13% (3/2215) in relation to the number of r.c. shaped
Shen et al. (2012)
ProFile Vortex
Faculty Dent. Univ. British Columbia, Canada
Undergraduate students
2203 files
Singe use
0.045% (1/2203) in relation to instruments discarded
Ehrhardt et al. (2012)
Dept. Endod. Sao Leopoldo Mandic Dent. Research Center
Six calibrated endodontists
556 mandibular and maxillary molars and bicuspids
1.98% (11/556) in relation to teeth treated
Wu et al. (2011)
ProTaper Universal rotary instruments
Dept. Endod. Stomatology
School, Nanjing Medical Univ. Jiangsu, China
One file for 3 molars or 10 premolars or 30 anterior teeth or one file single use for very complex or severely curved r.c.
6154 r.c. of 2654 teeth
2.6% (70/2654) overall instrument fracture in relation to teeth treated
1.1% (70/6154) in relation to the number of r.c. shaped
Inan and Gonulol (2009)
Univ. Samsun, Turkey
Ten trained operators
593 files collected and examined after clinical use over 12 months
Fracture determined by measuring the difference in length
16% (95/ 593)
Shen et al. (2009a)
ProTaper rotary
ProTaper hand
K3 files
Three Univ. endodontic clinics in China
1682 files
Instruments were discarded when they had reached the designated number of uses (different among the three clinics) or when they were worn, fractured, or with any other discernible defect
5% (79/1682) overall
• 5.3% (59/1108) ProTaper rotary
• 4% (11/280) ProTaper hand
• 3% (9/294) K3
Shen et al. (2009b)
Faculty Dent. Univ. British Columbia, Canada
Undergraduate students
3706 files
Each set for three uses
0.3% (12/3706) in relation to the instruments discarded
(Shen et al. (2009c)
ProFile 0.04
ProFile Series 29/0.04
Private practice
1071 ProFile 0.04
432 ProFile Series 29/0.04
1895 ProTaper
Single use
No fracture of ProFile 0.04
0.26% (5/1895) of ProTaper
Tzanetakis et al. (2008)
Ten Hero instruments
Nine ProFile
Six ProTaper
Two GT files
One Lentulo
28 in total
Dent. School, Athens, Greece
Endodontic postgraduate students
2180 teeth (4897 r.c.)
1.33% (28/2098) overall
• 1.88% (18/959) in retreatment cases
• 0.88% (10/1139) in initial treatments
Cheung et al. 2007)
ProTaper system
Stomatological School and Hospital, Wuhan Univ. China
Four trained dentists
726 files (401 hand and 325 engine driven)
14% (58/401) of hand-discarded instruments
14% (44/325) of engine-driven-discarded instruments
Wei et al. (2007)
College Stomatology, Sun Yat-sen Univ. China
Endodontic clinic
774 files
One file for 30 canals, one file single use in severely curved canals or when cutting efficiency was reduced or when any visible defect was detected
12.9% (100/774) overall incidence
• 88% (88/110) flexural fatigue cases no plastic defects
• 12%(12/100 torsional failure
Iqbal et al. (2006)
 – 49 ProFiles series 29
 – 10 ProFiles GTs
 – 3 LightSpeed
 – 5 ProTaper
 – 2K3 Endo files
69 NiTi in total
+12 SS
Univ. Pennsylvania, School Dent. Medicine
4865 molars and premolars
1.66% (81/4865) overall
• NiTi 1.68%(69/4865)
• SS 0.25% (12/4865)
in relation to teeth treated
Shen et al. (2006)
School Stomatology, Wuhan Univ. China
Four trained dentists
166 ProFile and 325 ProTaper
7% (12/166) for ProFile
• Flexural fatigue 4.8%(8/166)
• Torsional fatigue
2.4% (4/166)
14%(45/325) for ProTaper
• Flexural fatigue 13.2%(43/325)
• Torsional fatigue 0.6% (2/325)
Wolcott et al. (2006)
Endodontic group practice
Five Εndodontists
4652 r.c.
2.4% (113/4652) in relation to r.c. treated
Di Fiore et al. (2006)
GT Rotary
N. York Univ. College Dent. Post Graduate Endodontic Clinic
11 second-year endodontic residents
6661 files in total
3181 r.c. in 1403 teeth
0.39% (26/6661) overall incidence of fracture for all instruments used
• 0.82% (26/3181) in relation to the r.c. treated
• 1.9% (26/1403) in relation to teeth treated
Knowles et al. (2006)
Creighton Univ. Medical Center School Dent.
Graduate students
3543 canals
1.3% (46/3543) in relation to the number of r.c. shaped
Alapati et al. (2005)
ProFile GT
The Ohio State Univ. and Univ. Texas Dental Branch at Houston
Graduate endodontic clinics
822 files
6–8 uses
8%(14/175) of discarded ProFile
• 3% (16/595) of discarded ProFile GT
• 23%(12/52) of discarded ProTaper
Peng et al. (2005)
ProTaper S1
Endodontic clinic, Stomatological School, China
Endodontic clinic
122 files
One file for 4 molars or 20 premolars or 50 incisors or 50 canines or 1 file for a single use in very complex, severely curved, or calcified r.c.
23% (28/122) of discarded ProTaper S1
Cheung et al. (2005)
Same material and results as (Peng et al. 2005)
Parashos et al. (2004)
GT, Orifice Shapers, ProFiles, ProTaper Quantec, Quantec Flare HERO
Practices in 4 countries
14 endodontists
7159 files
5% (353/7159) overall
• 1.5% (103/7159) torsional
• 3.5% (250/7159) flexural)
of discarded instruments
Al-Fouzan (2003)
ProFile 0.04
Private practice
Two endodontists
449 files in total
419 maxillary and mandibular first and second molars (1457 r.c.)
4.6% (21/449) in relation to instruments used
• 5% (21/419) in relation to molars treated
• 1.4% (21/1457) in relation to r.c. treated
Arens et al. (2003)
ProFile Series 29/0.04
Private practice
786 files
New instruments used during a single-patient visit
0.89% (7/786) in relation to instruments used
Yared et al. (2000)
(0.06 taper)
13 sets of files (#40–15)
One set for 4 molars
52 molars
No fracture
Sattapan et al. (2000)
Quantec engine driven
NiTi files
Private practice
378 files discarded during normal clinical use over a 6-month period
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Oct 21, 2018 | Posted by in Endodontics | Comments Off on Introduction: Prevalence of Fractured Instruments
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