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Abdollahi, et al.: Antibacterial effects of 940 nm diode laser
a suitable substance. In recent studies, the success in cases with microbial resistance and penetration to
rate was reported at 95% for teeth with pulpitis and the root canal dentin and accessory canals. [19‑21] Since
85% for necrotic teeth. [2,4] Numerous studies have limited studies have investigated the antibacterial
shown that the prognosis of apical periodontitis after effects of 940 nm diode laser on E. faecalis in the
endodontic treatment is poorer in the presence of root canal, this study aimed to evaluate the effect
live bacteria. [5,6] Therefore, microorganisms play a of 940 nm diode laser compared to conventional
significant role in endodontic treatment failures, [7,8] detergents against E. faecalis.
and chemical root canal cleaning is necessary
in addition to mechanical preparation. [8,9] Ideal MATERIALS AND METHODS
chemical preparation with sodium hypochlorite
involves dissolving vital and necrotic tissues and This in vitro study was approved by the Research
removing bacteria, but the dentinal tubules cannot be Ethics Committee of Urmia University of Medical
sterilized. [10] Sciences, Urmia, Iran (IR.UMSU.REC.1399.243).
This in vitro study was performed in the Dental
Enterococcus faecalis is particularly important in the Faculty of Urmia University of Medical Sciences.
failure of endodontic treatment. [11,12] The prevalence of We selected 65 extracted human single‑rooted teeth.
this microorganism in cases of endodontic failure is Filled root canals and root canals with caries and
22%–77%. Due to its ability to survive at pH = 11.5, morphological complexities were excluded. The teeth
[13]
this microorganism can resist calcium hydroxide, had been extracted due to periodontal disease. The
which is used as an intracanal medication between inclusion criteria consisted of fully developed single
treatment sessions. E. faecalis can resist starvation roots without caries, previous endodontic treatment,
[14]
for a long time and grow alone in treated root canals and anomalies. Furthermore, teeth with cracks and
without supporting coexistent bacteria. Many calcifications in radiographic views were excluded.
[15]
studies have shown that the preparation of root canals After extraction, for better disinfection, the teeth
with manual and rotary file systems of nickel–titanium were stored in 3% chloramine T solution at 4°C
or stainless steel cannot sufficiently prepare and for 1 month. The root surfaces were cleaned with
clean the root canals. [16,17] However, when detergents ultrasonic tips to remove residual periodontal soft
are used in chemical preparation, with sodium tissues. Using a diamond disk (D and Z, Switzerland)
hypochlorite as the most commonly used one, it is and handpiece with a speed of 40,000 rpm without
impossible to completely remove the microorganisms water cooling, the tooth crowns were separated at
from the dentinal tubules. Therefore, in cases the cementoenamel junction. The working length
[18]
of microbial resistance to conventional treatment was determined using a #25 K‑Flexofile (Dentsply,
methods, lasers can be effective as an auxiliary Maillefer, Ballaigues, Switzerland), 1 mm from the
method to kill and reduce the microorganisms. The apical foramen. The crown‑down technique was
[19]
excellent antibacterial effect of diode laser irradiation applied for root canal instrumentation. The coronal
can be attributed to its greater penetration depth (up two‑thirds of the canals were prepared with #4 and #3
to 1000 μm into dentinal tubules) compared to the Gates‑Glidden drills (Dentsply, Maillefer, Ballaigues,
penetration power of chemical disinfectants, which is Switzerland), followed by the use of Sx, S1, S2, F1,
limited to 100 μm. [20] F2, and F3 Protaper rotary instruments (Dentsply,
One of the most popular lasers in endodontics Maillefer, Ballaigues, Switzerland). A master apical
is the diode laser. This laser effectively removes file of #40 was considered for all the root canals.
the smear layer and disinfects the primary and Each root canal was irrigated with 1 mL of normal
saline solution (Daru Pakhsh, Tehran, Iran) during the
accessory root canals. Diode lasers are available root canal preparation. The smear layer was removed
[21]
in four wavelengths: 810–830, 940, and 980 nm. The
antibacterial quality of diode lasers is attributed to the using 1 mL of 17% ethylenediaminetetraacetic
acid (Pulpdent Corp., Watertown, MA, USA) for
thermal effect and temperature increase in root canals 3 min, followed by a final rinse with 1 mL of 5.25%
during radiation. [22] NaOCl (Taj Corp, Tehran, IRI) for 3 min. Finally,
To date, none of the available irrigants have the the root canals were irrigated with 5 mL of saline
ideal necessities for achieving successful endodontic solution and dried with #40 paper cones (Aria Dent,
treatment. Furthermore, diode lasers are more effective Tehran, Iran). The apical foramina were sealed with

2 Dental Research Journal / 2024