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One of the greatest advances in endodontic research is the micro-computed tomography (micro-CT). Micro-CT is based on multi-slice X-ray images that are digitally grouped into a three-dimensional (3D) image. In comparison to SEM, confocal microscopy and stereomicroscopy, the micro-CT has the advantage of providing tridimensional reconstructions without the requirement of sectioning the samples. Furthermore, the small voxel size of micro-CT result in higher resolution than cone-beam computed tomographic. Micro-CT can be used to evaluate volume and/or area using scanning pre and post endodontic treatment. In this work, some applications of micro-CT in endodontic research are presented.
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Applications of micro-computed tomography in endodontic research
M.A. Marciano*1, M.A.H. Duarte1, R. Ordinola-Zapata1, A. Del Carpio Perochena1, B.C. Cavenago1,
M.H. Villas-Bôas1, P.G. Minotti1, C.M. Bramante1 and I.G. Moraes1
1Department of Endodontics, Bauru Dental School, University of São Paulo, Al. Octávio Pinheiro Brisola, 9-75, 17012-
901, Bauru, SP, Brazil.
One of the greatest advances in endodontic research is the micro-computed tomography (micro-CT). Micro-CT is based on
multi-slice X-ray images that are digitally grouped into a three-dimensional (3D) image. In comparison to SEM, confocal
microscopy and stereomicroscopy, the micro-CT has the advantage of providing tridimensional reconstructions without
the requirement of sectioning the samples. Furthermore, the small voxel size of micro-CT result in higher resolution than
cone-beam computed tomographic. Micro-CT can be used to evaluate volume and/or area using scanning pre and post
endodontic treatment. In this work, some applications of micro-CT in endodontic research are presented.
Keywords Micro-computed tomography; Root canal treatment
1. Introduction
The results obtained from controlled studies support advances and enhancements in different fields of knowledge. The
development of novel technologies is required to amplify the excellence and consistency of scientific researches.
Endodontic treatment involves several steps, which can determine the success or failure of therapy. Cleaning and
shaping procedures are performed to eliminate microbial infection from root canal system [1]. This phase of treatment
is executed with manual or rotary instruments [2] associated with irrigating solutions [3]. After the reduction of
microorganisms from root canal system, an obturation material is used to completely fill the cleaned space and prevent
fluid infiltration [4, 5]. Several studies are performed to analyse the ability of materials and techniques accomplished
during endodontic therapy. However, there are limitations related to some methodologies used. The introduction of X-
ray micro-computed tomography has substantially improved perspectives of endodontic researches. This technology has
been widely applied to evaluate anatomy, techniques and materials related to the endodontic treatment [6-8].
The X-ray micro-computed tomography (micro-CT) was developed in the early of 1980s [9]. The micro-CT is a non-
invasive and non-destructive method to obtain two- and three-dimensional images [10]. Its operation is based on
multiple X-ray converging on the sample and captured by a sensor. The projected X-ray is converted into digital
images. The volumetric pixel (voxel) provided by micro-CT range in 5-50 μm [9]. Smaller voxel size generates image
with higher resolution. The distance of axial scanning step can be previously determined using software. This
adjustment determines the resolution of image obtained, but also affect the time of exposure. Decrease of the distance
between scanning steps demand longer time of X-ray exposure. Furthermore, the multiple images created require high
memory in a computer to store the dates [11]. Depending on the material to be scanned, it is necessary longer time of
scanning to make it visible.
Micro-CT present several advantages in comparison with other methods, but otherwise has some limitations.
Scanning electron microscopy, stereomicroscopy and confocal laser microscopy can be used for superficial analysis but
do not provide 3D images without the requisite of sectioning the samples. Contrary of these microscopic methods,
micro-CT allow the use of the same sample for different tests without destruction of the sample [12]. This characteristic
is very important particularly when is required to evaluate volume pre and post instrumentation, quality of root canal
obturation or removal of the material from root canal (retreatment). Others advantages of micro-CT are the possibility
of repeated scanning [13] and the manipulation of image using specific software. On the other hand, a limitation of
micro-CT is the impossibility of using for in vivo studies due to the radiation level of exposure. Moreover, micro-CT
permits the examination of specimens of limited size, which restrict some analysis. Instead, cone beam computed
tomography (CBCT) could be used in patients despite its lower resolution [14].
Some applications of micro-CT in endodontic research include the analysis of internal anatomy of teeth [6, 15, 16],
instrumentation of root canal [17], root canal fillings [18], retreatment [19], physical and biological properties of
materials. The success of endodontic therapy is directly related to the identification of all root canals for its adequate
cleaning [15].The analysis of internal anatomy is important for knowledge of the complexity of root canal system and
planning the treatment[15]. Instrumentation techniques and instruments are evaluated to improve the removal of
contamination from root canal. Root canal filling techniques and sealers should be appropriately adapted into root canal
walls and the quality of obturations is commonly studied. Microorganisms are the main cause of persistent apical
periodontitis and the retreatment is indicated in some cases to decontaminate the root canal system. The aim of this
work is to describe the applications of X-ray microtomography in endodontic research.
Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.)
2. Materials and Methods
2.1 Internal anatomy
To analyse the internal anatomy it is not necessary a specific prepare of tooth before scanning. Extracted tooth is stored
in 10% formalin solution. Tooth is positioned into a patten and scanned with a desktop x-ray micro focus CT scanner
(SkyScan 1174v2, SkyScan, Kontich, Belgium). The equipment scan by using 50 kV x-ray tube voltages, 800 μA anode
current, and a detector based on a Charge Coupled Device camera (CCD) of 1.3 Mp (1304 x 1024 pixel). This device
enables the scanning of the sample up to 15 mm height with isotropic spatial resolution, which may vary between 6-30
micrometres. Commonly, one sample is scanned at a time. The equipment has a 1 mm of aluminium filter positioned in
front of the X-ray source for changing the sensitivity of polychromatic radiation. This whole system is connected to a
computer used in the control, data acquisition, reconstruction and analysis of the attributes of the images. The image
capture parameters to use are variable according to the sample, in relation of a voxel size and degree rotation step. For
example to scanning a maxillary first molar with approximately 20 mm length, may use 22μm with 0.7-degree rotation
step using a 180-degree rotation, this parameter will provide suitable images for a study of the anatomy of the root canal
system. The result of this scanning consisted of 327 .tiff images.
All digital data produced must be elaborated by reconstruction software (NReconv1.6.4.8, SkyScan) to obtain cross
sectional, to resulting in complete representation of the internal microstructure of each sample. The CTan software
(CTan v1.11.10.0, SkyScan) is used to processing and analysis of the images, utilized for the linear or 3D
measurements. Initially by a binarization process, which uses the mathematical operations to change values of the
pixels of the sample to be analysed. In the binarization is separated from the segments that correspond to the dentin and
the root canal, in the case of evaluating the root canal anatomy, or the filling material and dentine, in the case of
evaluating the root canal filling. The binary values are adjusted according to the raw images. In this process it is
possible to divide the image into regions, recognizing them as objects independent of each other and background. To
get a binary image where black pixels represent the background and the regions of white pixels, the objects of analysis.
Different plug-ins can be used according to the desired analysis. In the CTan software, when were scanned two or more
samples, they are present in the same image but could be separated to individually analyse. This was limited to the area
of interest (ROI) for each sample and the new ROI data was saved in separate folders. For a qualitative evaluation, the
double team cubes algorithm may create samples of three-dimensional models, and P3G in the format from the program
CTVol v. (SkyScan, Kontich, Belgium), can be made realistic visualization of three-dimensional models.
2.2 Instrumentation
Conventional access to the root canal system is performed using high-speed diamond burs 1014 (Sorensen, SP, Brazil).
Initial micro-CT scanning (SkyScan 1174v2, SkyScan, Kontich, Belgium) is performed at this stage to compare the
volume of canal pre and post instrumentation. To analyse root canal shaping is suitable to use a high resolution with a
rotation step ranging in 0.5-1.0 μm. After scanning, the working length is established measuring the position of a size
10 K-file (DentsplyMaillefer, Ballaigues, Switzerland) when it reached the apical foramen and then subtracting 0.5 mm.
Then, the canals are negotiated a size 20 K-file. The root canals are shaped using a rotary system and 2 mL of 2.5%
sodium hypochlorite (NaOCl) to irrigate the canal. After instrumentation, the canals are irrigated with 2 mL of 2.5%
NaOCl for 1 min using passive ultrasonic irrigation with an intermittent flush technique. Then, the post instrumentation
scanning is performed and the scanning pre and post instrumentation overlapping. The same teeth and the initial micro-
CT scanning can be used to sequentially analyse the root canal filling.
2.3 Obturation and retreatment
Initially the root canals of the teeth are instrumented using endodontic instruments and 2.5% sodium hypochlorite
(NaOCl). At the end of the cleaning and shaping procedure, the canals are irrigated with an ultrasonic unit with 2 mL of
2.5% NaOCl for 1 minute, this procedure is repeated three times. Then, the root canals receive a final flush of 2 mL of
17% EDTA (pH 7.7) for 3 min. This procedure is performed to improve the adaptation of the filling materials to the
root canal walls and to allow the penetration of the sealer into dentinal tubules. Finally, the canals are washed with a
final rinse of 2 mL distilled water and dried with paper points. The root canals are filled using an endodontic sealer and
gutta-percha cones. Teeth are stored at 37oC with 100% humidity to allow the sealers to set completely. Root canal
fillings require a high-resolution image, resulting a long time of scanning. High-resolution is obtained with a rotation
step ranging in 0.3-0.6μm. After scanning the root canal filling, it is possible to use the same sample to analyse
retreatment. For this evaluation, the volume of the obturated canal is measured and, after removal of the filling material
the volume of residual material is measured. The volume of the root canal filling and the residual filling material are
Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.)
3. Results and Discussion
Novel technologies are continuously introduced to enhance endodontic researches. The X-ray micro-computed
tomography has been used to evaluate several stages related to the endodontic therapy [6, 18-20]. Micro-CT provides
high-resolution images that can be grouped creating a three-dimensional image, analysed using software [6]. The
opportunity of sequential analysis without the destruction of samples provided a new perspective to endodontic
researches. Thus, it is possible to subsequently evaluate the internal anatomy [6], to shape the root canals and verify the
cleaning ability [20], to obturate the canals and calculate the filled area [8] and then desobturate using a retreatment
system and analyse its effectiveness [19].
Anatomic complexities difficult cleaning procedure and sometimes are the main causes of failure of treatment [21,
22]. During a long time the analysis of internal anatomy was performed using diaphanization method. This technique
consisted in access of the pulp chamber, dissolution of pulp tissue with sodium hypochlorite, decalcification of
mineralized structure with hydrochloric acid and injection of gelatin coloured with dye into the root canal [23]. The
analysis using diaphanization can provide an idea of three-dimensional structure of root canals [23]. However, this
method is considered out-dated and has the disadvantage of do not allow further use of the sample. Others
methodologies have been used to evaluate the internal anatomy. Stereomicroscopy was used to examine the mesio-
buccal roots of maxillary first and second molars using serial sections of root [24]. Cone beam computed tomography
(CBCT) was used for clinical analysis of internal anatomy [15]. Recently, micro-CT has been used to study anatomical
complexities of the root canal system (Fig 1). Some specific complexities as C-shaped canals [16] and isthmuses [25]
can be verified using three-dimensional reconstructions (Fig. 2). Additionally, the volume of the canal can be measured
using the initial scan and used to compare after shaping procedure.
Fig. 1 The figures show a maxillary molar with a projection of enamel between the roots (enamel pearl). In (A) the external anatomy
is represented by a digital photography. In (B) the internal anatomy of the root canal can be identified in a micro-CT reconstruction
with different transparency gradations. In (C) the corresponding x-ray image provided by micro-CT allows the recognition of the root
canal and the enamel projection at the middle third of the tooth. The software allows the analysis of the tooth in vertical or horizontal
sections, without the necessity of the physical section of the sample.
Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.)
Fig. 2 Micro-CT reconstructions of a mandibular molar. In (A) the external anatomy is showed. In (B-C) the root canal can be
recognized and the anatomical complexities are easily identified in due to the transparency. It is possible to verify an isthmus area in
the mesial root.
Success of endodontic treatment is related to an adequate cleaning and shaping procedure to eliminate bacterial
infection from root canal system [1]. Micro-CT can be used to evaluate the ability of endodontic instruments to clean
the root canal system. The volume pre and post instrumentation are measured and the area cleaned by the instruments is
determined [26]. The analysis of instrumentation procedure can be performed using different methods. Bramante et
al.[27] have proposed a method to evaluate the instrumentation of the root canals. Teeth are moulded and sectioned
before the root canal shaping. Each slice could be removed and photographed. The slices are originally positioned and
the root canal instrumented. After shaping, the slices are again removed and photographed. The images of sections
before and after instrumentation are compared to determine the instrumented area. Most recent methodologies are used
in endodontic researches to evaluate the shaping procedure. Some of these techniques include stereomicroscope [28],
scanning electron microscope [29] and morphometric evaluation [30]. In general using these methods, some sections are
selected and the cleaned area measured. Contrary, micro-CT allows the analysis of the complete root canal without the
requirement of sectioning. Scans pre and post instrumentation can provide date of the volume of canal cleaned. It is also
possible to verify areas that were not reached by the instruments, and consequently pulp tissue has persisted [7] (Fig. 3).
Fig. 3 The figures in (A-B) show a micro-CT scanning of mesial root of a mandibular molar. In (A) are represented horizontal
sections at different levels of the mesial root. It is possible to identify some isthmus areas. In (B) the three-dimensional reconstruction
of the instrumented canals are shown. Green represents the areas cleaned by endodontic instruments and red represents the areas
untouched. It is possible to observe large areas of the root canals without instrumentation. The anatomical complexities had
compromised the adequate cleaning.
The filling of the decontaminated root canal must adapt to the root canal space, including accessory anatomy [4]. In
overall, obturation techniques are performed with gutta-percha associated with a sealer. An adequate root canal filling
should present higher volume of gutta-percha and a thin layer of sealer at sealer/dentin interface. The presence of voids
or gaps is not desirable for a satisfactory obturation due to the risk of fluid infiltration and consequent contamination of
the root canal system. Several methods have been used to evaluate the adaptation and quality of root canal fillings.
Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.)
Confocal laser scanning can be used to visualise sealer adaption by adding a fluorescent dye in the sealer [4]. This
method is recommended when is necessary to analyse interfacial adaptation and verify the presence of gaps at
sealer/dentin interface. Stereomicroscope can be also used to evaluate root canal fillings [31]. These two methods
require sectioning the samples before analysis. Leakage tests are another method to analyse the adaptability of filling
materials [32]. However, the models proposed are controversial and some authors indicated that they are not reliable
[33]. Micro-CT has been proposed to evaluate the quality of obturation techniques. The percentage of volume of voids
and gaps in the root canal can be calculated (Fig. 4). The analyses include demarcation of voids and gaps in the two-
dimensional slices and then the reconstruction in a three-dimensional image. This process is considered prolonged and
difficult, but very accurate. The main advantage of micro-CT to evaluate root canal fillings is the possibility of further
analysis. After study of obturation, the material can be removed using a retreatment system and the ability of
retreatment techniques studied [34, 35].
Fig. 4 Mesial root of a mandibular molar is represented in (A-B). The image (A) shows the root canal filling in yellow. The image
(B) shows the root canal filling in yellow and the areas of the root canal that were not filled by the gutta-percha or sealer in red.
Recently, other applications for micro-CT in endodontic research have been developed. Previous investigations
regarding the use of micro-CT to analyse solubility was performed. Volume pre and post immersion are used to
determine the solubility rate of the material. It is an alternative to conventional solubility test that is commonly used in
endodontic research [36] and can provide an accurate date of volume loss closer of clinical situation. Furthermore,
micro-CT has a potential to analyse the root canal instruments (Fig. 5). It can be possible to verify deformation of
instruments after several uses. Biological properties are not widely analysed with micro-CT, however it represent a
promissory application. Volume of apical lesions can be assessed with scanning of fixed tissues (Fig. 5).
Fig. 5 In (A) an endodontic instrument (Mtwo, VDW, Munich, Germany) scanned by using micro-CT. The figure in (B) shows a
dog’ tooth with an evident periapical lesion round roots. The filling material into the root canal can be identified by its radiopacity.
Tree-dimensional images can be also made with cone beam computed tomography (CBCT). This method is
considered non-destructive as the micro-CT. CBCT has been used in endodontic research to evaluate several variables
[14]. This equipment has the advantage to be faster for scanning in comparison with micro-CT, and consequently the
levels of radiation exposure are lower [37]. That characteristic of CBCT allows its use for clinical researches and in vivo
analysis in animals [38, 39]. Nonetheless, micro-CT has higher resolution due to the lower voxel size [37]. Many times,
for scientific researches it is more significant the resolution and quality of the image than the time required for the
analysis. Despite CBCT is indicated to in vivo analysis, micro-CT is better recommended for laboratory researches. It
can be concluded that micro-CT represent the ideal advice for laboratory researches. In comparison with microscopic
Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.)
methods of analysis, three-dimensional images provided by micro-CT are superior for laboratory analysis. The
limitation of not allows the use in patients; do not limit its use in endodontic research.
Acknowledgements The support by FAPESP (2010/16072-2) is gratefully acknowledged.
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Full-text available
Objectives: To evaluate if the incorporation of antimicrobial compounds to chelating agents or the use of chelating agents with antimicrobial activity as 7% maleic acid and peracetic acid show similar disinfection ability in comparison to conventional irrigants as sodium hypochlorite or iodine potassium iodide against biofilms developed on dentin. Materials and methods: The total bio-volume of live cells, the ratio of live cells and the substratum coverage of dentin infected intra-orally and treated with the irrigant solutions: MTAD, Qmix, Smear Clear, 7% maleic acid, 2% iodine potassium iodide, 4% peracetic acid, 2.5% and 5.25% sodium hypochlorite was measured by using confocal microscopy and the live/dead technique. Five samples were used for each irrigant solution. Results: Several endodontic irrigants containing antimicrobials as clorhexidine (Qmix), cetrimide (Smear Clear), maleic acid, iodine compounds or antibiotics (MTAD) lacked an effective antibiofilm activity when the dentin was infected intra-orally. The irrigant solutions 4% peracetic acid and 2.5-5.25% sodium hypochlorite decrease significantly the number of live bacteria in biofilms, providing also cleaner dentin surfaces (p < 0.05). Conclusions: Several chelating agents containing antimicrobials could not remove nor kill significantly biofilms developed on intra-orally infected dentin, with the exception of sodium hypochlorite and 4% peracetic acid. Dissolution ability is mandatory for an appropriate eradication of biofilms attached to dentin.
Full-text available
The goal of the present article is to illustrate and analyze the applications and the potential of microcomputed tomography (micro-CT) in the analysis of tooth anatomy and root canal morphology. The authors performed a micro-CT analysis of the following different teeth: maxillary first molars with a second canal in the mesiobuccal (MB) root, mandibular first molars with complex anatomy in the mesial root, premolars with single and double roots and with complicated apical anatomy. The hardware device used in this study was a desktop X-ray microfocus CT scanner (SkyScan 1072, SkyScan bvba, Aartselaar, Belgium). A specific software ResolveRT Amira (Visage Imaging) was used for the 3D analysis and imaging. The authors obtained three-dimensional images from 15 teeth. It was possible to precisely visualize and analyze external and internal anatomy of teeth, showing the finest details. Among the 5 upper molars analyzed, in three cases, the MB canals joined into one canal, while in the other two molars the two mesial canals were separate. Among the lower molars two of the five samples exhibited a single canal in the mesial root, which had a broad, flat appearance in a mesiodistal dimension. In the five premolar teeth, the canals were independent; however, the apical delta and ramifications of the root canals were quite complex. Micro-CT offers a simple and reproducible technique for 3D noninvasive assessment of the anatomy of root canal systems.
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The aim of this study was to determine the mesiodistal and buccolingual diameter, apical volume, and the presence of isthmuses at the apical level of mesial root canals of mandibular molars. Sixty extracted first and second mandibular molars were scanned by using a SkyScan 1076 micro-computed tomography system with a voxel size of 18 μm. The apical thirds of the samples were reconstructed to allow a perpendicular section of the apical third by using the multiplanar reconstruction tool of the OsiriX software. The mesiodistal and the buccolingual distances of root canals were measured between the 1- to 4-mm levels. The type of root canal isthmuses present at these levels was classified by using modified criteria of Hsu and Kim. The volume of the root canal anatomy between the 1- to 3-mm apical levels was obtained by using the CTAN-CTVOL software. The medians of the mesiodistal diameter at the 1-, 2-, 3-, and 4-mm levels in the mesiobuccal and mesiolingual canals were 0.22 and 0.23 mm, 0.27 and 0.27 mm, 0.30 and 0.30 mm, and 0.36 and 0.35 mm, respectively. The buccolingual lengths at the 1-, 2-, 3-, and 4-mm levels were 0.37-0.35 mm, 0.55-0.41 mm, 0.54-0.49 mm, and 0.54 and 0.60 mm, respectively. The presence of isthmuses was more prevalent at the 3- to 4-mm level. However, 27 cases presented complete or incomplete isthmuses at the 1-mm apical level. The mean of the volume of the apical third was 0.83 mm(3), with a minimum value of 0.02 and a maximum value of 2.4 mm(3). Mesial root canals of mandibular molars do not present a consistent pattern. A high variability of apical diameters exists. The presence of isthmuses at the apical third was not uncommon even at the 1-mm apical level.
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The aim of this study was to evaluate the root canal preparation in flat-oval canals treated with either rotary or self-adjusting file (SAF) by using micro-tomography analysis. Forty mandibular incisors were scanned before and after root canal instrumentation with rotary instruments (n = 20) or SAF (n = 20). Changes in canal volume, surface area, and cross-sectional geometry were compared with preoperative values. Data were compared by independent sample t test and χ(2) test between groups and paired sample t test within the group (α = 0.05). Overall, area, perimeter, roundness, and major and minor diameters revealed no statistical difference between groups (P > .05). In the coronal third, percentage of prepared root canal walls and mean increases of volume and area were significantly higher with SAF (92.0%, 1.44 ± 0.49 mm(3), 0.40 ± 0.14 mm(2), respectively) than rotary instrumentation (62.0%, 0.81 ± 0.45 mm(3), 0.23 ± 0.15 mm(2), respectively) (P < .05). SAF removed dentin layer from all around the canal, whereas rotary instrumentation showed substantial untouched areas. In the coronal third, mean increases of area and volume of the canal as well as the percentage of prepared walls were significantly higher with SAF than with rotary instrumentation. By using SAF instruments, flat-oval canals were homogenously and circumferentially prepared. The size of the SAF preparation in the apical third of the canal was equivalent to those prepared with #40 rotary file with a 0.02 taper.
The cleaning capacity of manual and rotary instrumentation techniques in mesial-distal flattened canals was studied by morphometric analysis. Twenty human mandibular incisors were divided into two groups of 10 teeth each: group 1, crown-down technique with rotary instrumentation using ProFile .04; group 2, crown-down technique with manual instrumentation using K-files. The teeth were evaluated with an optic microscope that was coupled to a computer to determine the percentage of root canal area with debris. The nonparametric Mann-Whitney U test showed a statistically significant difference at the level of 1% between the techniques. The manual technique was more efficient in cleaning mesial-distal flattened root canals than the rotary technique, although neither completely cleaned the root canal.
Roggendorf MJ, Legner M, Ebert J, Fillery E, Frankenberger R, Friedman S. Micro-CT evaluation of residual material in canals filled with Activ GP or GuttaFlow following removal with NiTi instruments. International Endodontic Journal, 43, 200–209, 2010. Aim To assess the efficacy of removing Activ GP or GuttaFlow from canals using NiTi instruments. Methodology Root canals in 55 extracted pre-molars were prepared to apical size 40, 0.04 taper. The teeth were imaged with micro-CT, and 30 teeth selected that had consistent apical size and taper of the shaped canals. They were randomly assigned to root filling with either the glass-ionomer-based ActivGP system (n = 15) or the polyvinylsiloxane-based GuttaFlow system (n = 15). After 2 weeks, canals were retreated stepwise with size 40–50 EndoSequence 0.04 taper instruments. Micro-CT scans (8 μm) were taken after use of each instrument to detect root filling residue in the coronal, middle and apical segment, and the retreatment time recorded. Residue, expressed as percentage of canal surface area, was compared between groups with t-tests, and within groups with repeated measures anova and Bonferroni-adjusted pairwise comparisons. Retreatment time was analysed with one-way anova. Results The percentage of sealer residue-coated canal surface was consistently highest (P < 0.001) in the apical third of canals, and it did not differ significantly between the two root filling groups. Stepwise enlargement from size 40 to 50 significantly decreased the amount of sealer residue in both groups (P < 0.001). Retreatment time did not differ significantly between groups. Conclusions Both root fillings with ActivGP and GuttaFlow were removed with nickel-titanium rotary instruments. Enlargement of canals up to two sizes beyond the pre-retreatment size was necessary to minimize the amount of sealer remaining.
Stern S, Patel S, Foschi F, Sherriff M, Mannocci F. Changes in centring and shaping ability using three nickel–titanium instrumentation techniques analysed by micro-computed tomography (μCT). International Endodontic Journal, 45, 514–523, 2012. Aim To compare the centring ability and the shaping ability of ProTaper (PT) files used in reciprocating motion and PT and Twisted Files (TF) used in continuous rotary motion, and to compare the volume changes obtained with the different instrumentation techniques using micro-computed tomography. Methodology Sixty mesial canals of thirty mandibular molars were randomly assigned to three instrumentation techniques: group 1, canals prepared with the PT series (up to F2) (n = 20); group 2, canals prepared with the F2 PT in reciprocating motion (n = 20); group 3 canals prepared with the TF series (size 25) (n = 20). Teeth were scanned pre- and post-operatively using micro-computed tomography to measure volume and shaping changes, and the obtained results were statistically analysed using parametric tests. Results The increase in canal volume obtained with the three instrumentation techniques was not significantly different. Canals were transported mostly towards the mesial aspect in the apical- and mid-third of the roots, and towards the furcal aspect coronally. No difference in the transportation and centring ratio was found between the techniques. There was no significant difference between the times of instrumentation (TF: 62.5 ± 5.4 s; PT: 60.6 ± 3.9 s; and F2 PT file in reciprocating motion: 51.0 ± 3.3 s). Conclusions ProTaper files used in reciprocating motion and PT and TF used in continuous rotary motion were capable of producing centred preparations with no substantial procedural errors.
To compare the efficacy of two rotary NiTi retreatment systems and Hedström files in removing filling material from curved root canals. Curved root canals of 57 extracted teeth were prepared using FlexMaster instruments and filled with gutta-percha and AH Plus. After determination of root canal curvatures and radii in two directions, the teeth were assigned to three identical groups (n = 19). The root fillings were removed with D-RaCe instruments, ProTaper Universal Retreatment instruments or Hedström files. Pre- and postoperative micro-CT imaging was used to assess the percentage of residual filling material as well as the amount of dentine removal. Working time and procedural errors were recorded. Data were analysed using analysis of covariance and analysis of variance procedures. D-RaCe instruments were significantly more effective than ProTaper Universal Retreatment instruments and Hedström files (P < 0.05). Hedström files removed significantly less dentine than the rotary NiTi systems (P < 0.0001). D-RaCe instruments were significantly faster compared to both other groups (P < 0.05). No procedural errors such as instrument fracture, blockage, ledging or perforation were detected in the Hedström group. In the ProTaper group, four instrument fractures and one lateral perforation were observed. Five instrument fractures were recorded for D-RaCe. D-RaCe instruments were associated with significantly less residual filling material than ProTaper Universal Retreatment instruments and hand files. Hedström files removed significantly less dentine than both rotary NiTi systems. Retreatment with rotary NiTi systems resulted in a high incidence of procedural errors.
Differences in bone density before and after endodontic treatment were examined in teeth with periapical lesions in Hounsfield units (HUs) by using cone beam computed tomography (CBCT). Sixteen patients requiring endodontic treatment for periapical lesions underwent CBCT scan before and after treatment. Their bone densities were calculated in HUs. The study included 16 lesions measuring 8-10 mm in diameter. HU measurements were taken from an area of 2.25 mm(2) on the CBCT images where the bone density was lowest, before and after treatment. The initial and final measurements were compared statistically by using paired samples statistics at the 5% significance level. The results of this study support the use of CBCT to measure bone density before and after endodontic treatment.
The aim of the study was to evaluate the radiopacity, solubility, flow, film thickness, setting time, and adaptation to the root canal walls of 3 epoxy resin-based sealers: AH Plus, Acroseal, and Adseal. Physical tests were performed following American National Standards Institute/American Dental Association's requirements. For interfacial adaptation analysis, 30 maxillary canines were shaped by using ProTaper instruments. The specimens were divided into 3 groups (n = 10): group 1, AH Plus; group 2, Acroseal; and group 3, Adseal. The sealers were mixed with rhodamine B dye, and the canals were filled by using the lateral compaction technique. The percentage of gaps and voids area was calculated at 2, 4, and 6 mm levels from the apex. Statistical evaluation was performed by using analysis of variance for physical analysis and nonparametric Kruskal-Wallis and Dunn tests for interfacial adaptation (P < .05). No statistical differences were found for adaptation, percentage of voids, solubility, flow, and film thickness among the sealers (P > .05). AH Plus was significantly more radiopaque (P < .05). For the setting time, there were statistical differences among all the studied sealers (P < .05). AH Plus, Acroseal, and Adseal presented similar root canal adaptation, solubility, flow, and film thickness. Statistical differences were found for radiopacity and setting time (P < .05).