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International Journal of Computerized Dentistry 2020;23(2):1–10 1
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Ralf Krug, Sebastian Reich, Thomas Connert, Stefan Kess, Sebastian Soliman, Marcel Reymus,
Gabriel Krastl
Guided endodontics: a comparative in vitro study on the accuracy
and effort of two different planning workflows
Abstract
Aim: To compare the accuracy and effort of digital workflow
for guided endodontic access (GEA) procedures using two
different software applications in 3D-printed teeth modeled
to simulate pulp canal obliteration (PCO) in vitro.
Materials and methods: 32 3D-printed incisors with simulat-
ed PCO were fabricated and mounted, four each on maxillary
and mandibular study arches. Cone beam computed tomog-
raphy (CBCT) and 3D surface scans were matched and used to
virtually plan and prepare GEA by one operator using two
different methods: 1) CoDiagnostiX (CDX, Dental Wings) with
3D-printed templates, and 2) Sicat Endo (SE, Sicat) with sub-
tractive CAD/CAM-manufactured templates. Postoperative
CBCT and virtual planning data were superimposed for
analysis. Accuracy was assessed by measuring the discrepan-
cies between planned and prepared cavities at the tip of the
bur (three spatial dimensions, 3D vector, angle). Virtual plan-
ning effort was defined as the time and number of computer
clicks. A 95% confidence interval (CI) was computed for each
sample.
Results: SE successfully located root canals for GEA in 16/16
cases (100%) and CDX in 15/16 cases (94%). SE resulted in less
mean deviation at the tip of the bur with regard to distance in
the labial-oral direction (0.12 mm), 3D vector (0.35 mm), and
angle (0.68 degrees) compared with CDX (0.54 mm, 0.74 mm,
1.57 degrees, respectively; P < 0.001). CDX required less mean
planning time and effort for each four-tooth arch (10 min 50 s,
107 clicks) than SE (20 min 28 s, 341 clicks; P < 0.05).
Conclusions: Both methods enabled rapid drill path plan-
ning, a predictable GEA procedure, and the reliable location
of root canals in teeth with PCO without perforation.
Keywords: 3D printing, access cavity, accuracy, calcic meta-
morphosis, guided endodontics, pulp canal obliteration, root
canal treatment, template
Introduction
Access cavity preparation in teeth with pulp canal oblitera-
tion (PCO) and apical periodontitis is a challenging, time-con-
suming, and technically demanding procedure that requires
high-level equipment such as a dental microscope, ultrasonic
instruments, and cone beam computed tomography (CBCT).1
The conventional endodontic approach may result in compli-
cations such as altered root canal geometry or the substantial
loss of dental hard tissue.2 This may significantly weaken the
affected tooth and can ultimately lead to root perforation or
tooth fracture.3–6
The guided endodontic access (GEA) approach to locating
and accessing calcified root canals appears to be a promising
way to prevent such complications.7-10 Two ex vivo studies
demonstrated that guided endodontics is an impressive ap-
proach that is reliable, accurate and operator-independ-
ent.7,11 A more recent study found significantly less substance
loss and a shorter treatment duration for guided versus con-
ventional access cavity preparations in 3D-printed teeth.2
Several clinical cases have shown that the GEA procedure can
be successfully used to treat anterior and posterior teeth with
PCO and apical periodontitis.8,12-15 In one clinical study, guid-
ed root canal treatment allowed the successful location and
negotiation of all root canals in 50 single-rooted teeth with
PCO.14 Furthermore, equipment for the GEA procedure has
been miniaturized, and it was shown to be beneficial even in
narrow-rooted teeth such as mandibular incisors.11,12 One
group demonstrated the possibility of overcoming the prob-
lem of limited interocclusal space in the posterior region as
well as performing GEA preparation in a molar with PCO by
transforming the virtual drill path into a composite-based
intracoronal guide.15
However, special virtual planning software is needed to
position the drill paths and design the templates needed for
GEA. Two commercial software solutions for guided endo-
dontics are currently well established: CoDiagnostiX (CDX;
Dental Wings GmbH, Chemnitz, Germany) and Sicat Endo (SE;
Sicat GmbH, Bonn, Germany). While CDX was originally
designed for implant dentistry and uses an add-on tool to
International Journal of Computerized Dentistry 2020;23(2):1–10
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superimpose the axis of the bur onto the axis of the root
canal, SE was specifically designed for the treatment of com-
plex and challenging endodontic cases.
The present in vitro study was designed to compare the
accuracy and effort of the GEA workflow using CDX versus SE
for root canal location in study models with 3D-printed inci-
sors with simulated PCO. Accuracy was measured as the devi-
ation between the planned and prepared cavities at the tip of
the bur in terms of distance in three dimensions, 3D vector,
and angle, and effort was measured as the time and the num-
ber of computer clicks required for virtual planning.
Materials and methods
3D-printed teeth and study models
Thirty-two 3D-printed incisor teeth with simulated PCO
were fabricated based on selected radiograph micro-com-
puted tomography (µCT) data sets (voxel size: 27 µm) for
one maxillary central, one maxillary lateral, and one man-
dibular central human incisor with PCO captured with an
Inveon Multimodality Single-Photon Emission Computed
Tomography scanner (Siemens Preclinical Solutions, Knox-
ville, TN, USA). Inveon Acquisition Workplace Version 1.4.3.6
was used for to capture and reconstruct the image data. The
corresponding DICOM data sets were segmented and
exported as STL data sets using ITK-SNAP 3.6 freeware
(www.itksnap.org) and then imported to the open-source
3D creation suite Blender 2.78 (www.blender.org) for ana-
tomical adaptation. The root canals were digitally modified
to obtain 3D-printed teeth with a coronal-apical length of
5 mm and a diameter of 0.25 mm (Fig 1).
The operator captured mirror images around the longitu-
dinal axis of selected teeth to achieve chiral symmetry of
teeth in each quadrant. Each arch contained four maxillary or
four mandibular incisors. The reliable printability of the mod-
ified data sets was evaluated using Autodesk Netfabb
14.0.23.0 (www.autodesk.de). All teeth were 3D printed using
the digital light processing (DLP)-based Solflex 350 printer
and V-Print 3D printing resin (both from Voco, Cuxhaven, Ger-
many). Subsequently, the teeth were soaked in isopropanol
for 5 min, followed by standardized centrifugation to pre-
serve the apical patency of the root canals.
Four maxillary incisors (teeth 12 to 22) and four mandibu-
lar incisors (teeth 32 to 42) each were mounted on study arch-
es to yield four identical jaw models. Three prefabricated
teeth – one canine and two premolars (ANA-4 Z; Frasaco
GmbH, Tettnang, Germany) – were additionally mounted in
each quadrant to stabilize the template while performing the
GEA procedure. The arches were stabilized by adding a
2-mm–thick layer of cold-curing polymer denture base resin
(Paladur, Kulzer) to the cervical and interradicular areas of
each tooth. The root surfaces were left uncovered to facilitate
adequate CBCT imaging. The roots were embedded into
putty silicone (Fifty-Fifty 95 putty; Klasse 4 Dental GmbH,
Augsburg, Germany) to obtain a removable base for the
model. Each prepared model was secured onto a phantom
head using holders (Fig 2). CDX and SE were used for GEA cav-
ity planning and preparation for four study models each (two
maxillary and two mandibular arches).
Preoperative scans
For each model, a preoperative CBCT scan with a voxel size of
80 µm was acquired in high-definition mode using the
Orthophos SL 3D scanner (Dentsply Sirona, Bensheim, Ger-
many) and stored as a DICOM file. STL files of the surface data
were then created using a 3D intraoral scanner (Dental Wings
Intraoral Scanner; Dental Wings GmbH).
Virtual planning
CDX and Sicat Endo were used to virtually plan the GEA pro-
cedures for four study arches each, as described by Connert
et al.2,11,12 In the case of CDX, STL and DICOM data for four
study arches (two maxillary, two mandibular) were uploaded
to the CoDiagnostiX software (Version 9.2; Dental Wings
GmbH) and matched by aligning the contours of the teeth. A
virtual image of a bur with a diameter of 1.0 mm (Gebr. Bras-
seler GmbH & Co KG, Lemgo, Germany) was superimposed on
the matched data to virtually access the orifice of the root
canal. The position was checked in three dimensions. After-
wards, a virtual sleeve with an inner diameter of 1.0 mm was
placed. Next, a drill guide template was designed, 3D printed
(Objet Eden260V; material: MED610; Stratasys Ltd, Minneapo-
lis, MN, USA) and fitted with custom metallic sleeves (ste-
co-system-technik GmbH & Co. KG, Hamburg, Germany) to
yield the final template (Figs 3 and 4).
Likewise, Sicat Endo was used according to the manufac-
turer’s instructions to virtually plan the GEA procedure for the
other four study arches under analogous conditions (Figs 5
and 6).
The investigator recorded the time and the number of
computer clicks required to plan the drill paths and place the
drilling sleeves for each software application and each four-
tooth arch.
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Krug et al
Fig 1 Radiographs of 3D-printed incisors with simulated
calcification in the coronal and central third of the root canal; the
root canal space in the apical third was limited to a maximum
diameter of 0.25 mm.
Fig 2 Study model with template positioned on the 3D-printed
study teeth; the adjacent prefabricated teeth were used to
facilitate GEA cavity preparation. A holder was used to secure the
model onto a removable base on a phantom head.
Fig 3 Virtual drill path planning and sleeve placement in
maxillary incisors using CoDiagnostiX software.
Fig 4 Representative cross-sections verifying the tangential and
axial positions of the drill relative to the root canal; 3D view with
the template and radiographic view without it, as computed
using CoDiagnostiX software.
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Template manufacturing
Additive manufacturing (CDX)
3D printing of templates designed with the CDX software was
outsourced to a specialized laboratory (Implantec Dentalla-
bor GmbH, Amstetten, Germany). The templates were fabri-
cated using a Stratasys Eden 260V/ 260V Dental 3D printer
with PolyJet, a 3D-printing technology that jets curable liquid
photopolymer onto a build tray to produce parts in horizon-
tal layers with a minimum thickness of 16 µm. The laboratory
performs ultraviolet calibration of the 3D printer, weight cali-
bration of the print heads, and pattern tests routinely as part
of process-oriented quality management. Additionally, the
dimensional accuracy of the pattern template was checked,
the fit of the sleeve was evaluated with a test specimen, and a
dimension check of the hole for the sleeve was performed.
Subtractive manufacturing (Sicat Endo)
All templates planned with Sicat Endo were fabricated using
industry-standard five-axis milling machines within a
ISO13485-certified process. All sleeve positions were verified
individually by means of tactile coordinate measurement
machines (Zeiss; Oberkochen, Germany).
Access cavity preparation
One operator (SR) performed coronal access cavity prepar-
ation on all 3D-printed study teeth using the GEA approach.
For this purpose, the models were mounted on a dental
manikin (P-6; Frasaco GmbH) that was secured on a dental
chair (Teneo; Dentsply Sirona, York, PA, USA) to imitate the
clinical environment. CBCT scans and digital periapical radi-
ographs were used as diagnostic tools during the proced-
Fig 5 Representative cross-sections verifying the axial, tangen-
tial and sagittal positions of the drill relative to the root canal in
the Sicat Endo software.
Fig 6 Virtual planning of the drill paths and sleeve placement
into the mandibular incisors using Sicat Endo.
Fig 7 Straight-line access to the root canal was established by preparing a small plateau perpendicular to the drill path, placing the
template in position, and using a bur to perform the GEA procedure in the 3D-printed maxillary teeth (a), and mandibular teeth (b).
ab
International Journal of Computerized Dentistry 2020;23(2):1–10 5
Krug et al
ure. In order to establish adequate straight-line access for
GEA, the operator prepared a small plateau perpendicular
to the planned drill path, which extended up to a depth of
2 mm. The point of entry was marked on each 3D-printed
incisor by staining the tip of the bur before placing the tem-
plate with the bur on the model. The plateau was created
using a high-speed contra-angle handpiece (1:5, Kavo Mas-
ter Series; Kavo Dental GmbH, Biberach, Germany) with a
cylindrical diamond bur with rounded edges (837KR; Inten-
siv SA, Montagnola, Switzerland). Finally, the operator used
the appropriate 3D-printed template and bur to perform
the GEA procedure as described by Connert et al2 ,11,12 (Figs
2 and 7). If the root canal was successfully accessed and
negotiated, a periapical radiograph was taken with a K file
to verify the result.
Postoperative scan
Pre- and postoperative CBCT scans of each model were
uploaded to the CDX software and superimposed. A built-in
tool was used to mark the tip of the bur and measure the
deviation between the planned and prepared cavities in
three dimensions in terms of distance (mm), 3D vector (mm),
and angle (degree) (Fig 8). The 3D vector was calculated from
the mesiodistal (x), labial-oral (y), and coronal-apical (z) dis-
tances taking the radical (x2 + y2 + z2). The tip of the bur
regarding the planned cavity marked the zero point of the 3D
coordinate system.
Statistical analysis
A descriptive analysis of the data generated by each planning
method was performed using the following variables: success
of root canal detection (yes/no), deviation between the
planned and prepared access cavities at the tip of the bur in
terms of distance in three dimensions, 3D vector and angle as
well as planning effort (time and number of computer clicks
required). Inferences drawn by inductive statistics were based
on the assumption of independent samples. Two-level
analysis was performed using an independent samples ttest
and Levene’s test for homogeneity of variance. Six-level
analysis was conducted by one-way analysis of variance
(ANOVA). The degree of freedom (df), tvalue, 95% confidence
interval (CI), and effect size (Cohen’s d) values were calculat-
ed. SPSS Statistics (Version 25 Premium; IBM, USA) was used
to identify statistically significant differences. The level of sig-
nificance was set at α = 0.05.
Fig 8 Virtual planning
image (a) and radiograph
(b) illustrating the 3D
measurement of deviation
between the virtually
planned (blue) and
prepared (red) access
cavities at the tip of the bur. a b
Results
The accuracy of the two methods was measured three-di-
mensionally as the mean deviation between the planned
from prepared access cavity at the tip of the bur in terms of
distance, 3D vector, and angle. The mean distance deviation
in the labial-oral dimension was 0.54 mm (95% CI: 0.37 to
0.71 mm) with CDX, and 0.12 mm (95% CI: 0.06 to 0.18 mm)
with SE. The mean 3D vector deviation was 0.74 mm with CDX
(95% CI: 0.60 to 0.87 mm), and 0.35 mm with SE (95% CI: 0.26
to 0.43 mm). Finally, the mean angle of deviation was 1.57
degrees (1.16 to 1.97 degrees) with CDX, and 0.68 degrees
(0.47 to 0.90 degrees) with SE (Table 1; Figs 9 and 10).
The mean virtual planning time required for each four-
tooth arch was 10 min 50 s (95% CI: 4 min 16 s to 17 min 24 s)
with CDX, and 20 min 28 s (95% CI: 11 min 2 s to 29 min 54 s)
with SE. The mean number of computer clicks was 107 (95%
CI: 62 to 151), and 341 (95% CI: 208 to 473) with CDX and SE,
respectively (Figs 11 and 12).
Finally, the number of root canals successfully accessed
and negotiated was 15 of 16 (93.8%) with CDX and 16 of 16
(100%) with SE.
Discussion
This is the first study comparing the technical accuracy and
effort of two well-established, commercially available virtual
planning software applications for the GEA procedure. In
agreement with our results, a few preclinical studies, several
case reports, and one observational study using various guid-
ed approaches to endodontic access cavity preparation or
apical surgery also highlight the high accuracy and success of
this approach.16
In this in vitro study, we compared the technical accuracy
and effort of two different software applications when uti-
International Journal of Computerized Dentistry 2020;23(2):1–10
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1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
Deviation (mm)
3D-vector
1
CDX Sicat Endo
Fig 9 Distribution of 3D vector deviation between planned and
prepared access cavities at the tip of the bur for CoDiagnostiX
(CDX) versus Sicat Endo.
Angle
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Deviation (degree)
1
CDX Sicat Endo
Fig 10 Distribution of angle deviation between planned and
prepared access cavities at the tip of the bur for CoDiagnostiX
(CDX) versus Sicat Endo.
36:00
28:48
21:36
14:24
07:12
00:00
Planning duration (min:s)
Planning duration
1
CDX Sicat Endo
500
450
400
350
300
250
200
150
100
50
0
Number of computer clicks
Computer clicks
1
CDX Sicat Endo
Fig 11 Distribution of values for virtual planning time per four-
tooth arch required with CoDiagnostiX (CDX) versus Sicat Endo.
Fig 12 Distribution of the number of computer clicks per
four-tooth arch with CoDiagnostix (CDX) versus Sicat Endo.
Tab le 1 Guided endodontics outcomes achieved using CoDiagnostiX (Dental Wings GmbH) versus Sicat Endo (Sicat GmbH)
Outcome measures CoDiagnostiX (n = 16) Sicat Endo (n = 16)
P
dM SD CI 95% M SD CI 95%
Deviations per tooth
Distances (mm)
Mesiodistal 0.27 0.22 0.15–0.39 0.15 0.09 0.11–0.22 0.06
Labial-oral 0.54 0.32 0.37–0.71 0.12 0.11 0.06–0.18 < 0.001*** 1.35
Coronal-apical 0.25 0.19 0.15–0.35 0.25 0.18 0.15–0.35 0.99
3D vector (mm) 0.74 0.26 0.60–0.87 0.35 0.17 0.26–0.43 < 0.001*** 1.78
Angle (degrees) 1.57 0.76 1.16–1.97 0.68 0.41 0.47–0.90 < 0.001*** 1.46
Planning effort per each four-tooth arch
Planning time (min:s) 10:50 4:08 4:16–17:24 20:28 5:56 11:02–29:54 0.037* 1.89
Number of CC (n) 107 28.03 62–151 341 83.26 208–473 0.002** 3.77
Accuracy was measured as the mean deviation between planned and prepared access cavities at the tip of the bur in terms of distance in three
dimensions, 3D vec tor, and angle. Virtual planning effort was measured as the time and number of computer clicks required per four-tooth study arch
(M: mean; SD: standard deviation; CC: computer click; CI: confidence interval; P = P value; d: Cohen’s d effect size; *: P < 0.05; **: P < 0.01; ***: P < 0.0 01).
International Journal of Computerized Dentistry 2020;23(2):1–10 7
Krug et al
lized to plan GEA procedures in 3D-printed teeth with simu-
lated PCO. Accuracy was measured as deviation between the
planned and prepared access cavity, and effort was defined
as the time and number of computer clicks required for virtu-
al planning. The results indicate that both software applica-
tions enable rapid and reliable access to calcified root canals.
However, compared with CDX, the use of Sicat Endo for GEA
planning resulted in significantly less deviation between the
planned and prepared access cavities in terms of labial-oral
distance, 3D vector, and angle at the tip of the bur. With both
software applications, the overall deviations between the
planned and prepared access cavities at the tip of the bur
were < 0.9 mm for distance in three dimensions and 3D vec-
tor, and overall angle deviation was < 2 degrees.
Furthermore, the virtual planning effort, defined as the
time and number of clicks required for GEA planning, was
substantially less for CDX than for SE.
The GEA procedure is known to facilitate the location and
negotiation of root canals in teeth with obliterated pulp
canals in need of endodontic treatment, and it was reported
to achieve a success rate of 100% in 50 cases treated in a clin-
ical setting.14 Various ex vivo studies have demonstrated the
successful application of a guided endodontics technique in
mandibular incisors,11 maxillary anterior teeth and pre-
molars,7 and in teeth of various types, including molars.9 In
the present in vitro study, CDX failed to locate 1 of 16 root
canals with simulated calcification. Connert et al2 revealed
that utilization of the GEA procedure in 3D-printed teeth
does not invariably result in success: it was found that only 22
of 24 root canals were negotiable. Compared with natural cal-
cified teeth, access preparation in the apical part of 3D-print-
ed teeth may be more challenging. The existence of narrow
root canals can always be confirmed by histological evalu-
ation in extracted teeth that appear radiographically to have
totally obliterated pulp canals.17 However, in the artificial
teeth studied here, the calcified part of the root canal was
fully blocked by 3D printing resin. Furthermore, because fixa-
tion of the artificial teeth was only performed in the cervical
region, slight tooth mobility might have occurred and thus
decreased the accuracy of GEA in our experimental setting
compared with a clinical setting.
This in vitro study was adapted from the method pro-
posed by Connert et al2 in an attempt to simulate clinical
conditions as realistically as possible by using 3D-printed
teeth that were identical to natural incisors. However, the
use of 3D-printed teeth is subject to several limitations. The
physical properties of human dentin, a biological material, is
hard to imitate with 3D printing resin. As a result, 3D-printed
teeth tend to have less stiffness and hardness than natural
teeth18 (Martens Hardness: V-Print ee 139,8 ± 12.87 MPa vs
Dentin 499.9 ± 46,41 MPa). Further, the 3D printing resin
used in this study is a homogenous material without any var-
iations in color or consistency. Thus, the advantage of an
anatomical alignment helping the clinician determine where
the drill path should be placed is missing. Although the high
level of standardization used to compare the GEA proced-
ures performed using the two different software applica-
tions can be considered an advantage, the fact that the
designed root canals were very short and only negotiable
close to the apex resulted in a high level of difficulty.2 Ana-
tomical features such as landmarks and color that change in
the dentinal hard tissue, which are common in human teeth
with PCO, might make it easier to locate calcified root canals
by the conventional technique. During the GEA procedure,
these features might not be readily visible because, obvious-
ly, the view of the prepared cavity through a guided drill
path is limited in both human and 3D-printed teeth. More-
over, in cases where the drill entry point was on a curved
area near the incisal edges of the artificial teeth, a plateau
was prepared perpendicular to the planned drill path to
avoid misalignment of the bur. This is in accordance with the
clinical situation: initially, due to its considerable hardness
(260 HV),19 the overlying enamel has to be removed prior to
guided access cavity preparation through calcified dentin.7
The accuracy of access cavity planning and preparation
in this study could have been affected by the accuracy of
the fabricated drill guide templates, the accuracy of fit of
the drilling sleeves, and the accuracy of sleeve-guided drill-
ing during cavity preparation. While the sleeves and the
drills are produced by metal process manufacturing, which
is a well-known industrial production process achieving
high-precision instruments, the template production pro-
cess was just developed within the last two decades. Initial-
ly designed for advanced implant dentistry, the process was
adapted for clinical use in guided endodontics only a few
years ago.8,20 Besides conventional manual fabrication, both
subtractive computer-aided design and computer-aided
manufacturing (CAD/CAM) and additive 3D-printing are
appropriate for accurate template production. One study
evaluating data from 13 patients revealed significant differ-
ences between conventional thermoformed and 3D-printed
surgical guides: based on the 3D geometry of the implant
sleeve, the mean discrepancy of the angle was found to be
3.48 degrees.21 Another study evaluating the accuracy of
virtually designed and 3D-printed surgical templates
planned with the CDX software found that, in the center of
International Journal of Computerized Dentistry 2020;23(2):1–10
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the sleeve bases, the mean angular deviation was
1.5 degrees (range: 0.4 to 3.3 degrees) compared with the
virtual positions.22 Conversely, one review suggests that
there were no statistically significant differences between
the results of different studies, including clinical and in vitro
studies, with regard to the accuracy of different methods of
template fabrication for guided implant surgery.23 A more
recent systematic review and meta-analysis of clinical fac-
tors affecting the accuracy of guided implant surgery con-
cluded that the position and fixation of the guide may have
a substantial impact on the accuracy of computer-guided
implant surgery.24
To the best of the present authors’ knowledge, compara-
ble studies comparing deviation between different types of
drill guides for endodontics are lacking. However, the appli-
cation of a comparable technique using a drill guided by a
sleeve is presumed to be a critical success factor. The present
study demonstrates that templates fabricated by both sub-
tractive CAD/CAM (for Sicat Endo) and additive 3D printing
(for CDX) are highly accurate. However, the observed differ-
ences in mean deviation at the tip of the bur might have
been influenced by the method of guide fabrication, where
CAD/CAM may have a slight advantage. From a technical
point of view, additive manufacturing differs substantially
from milling. An additively manufactured object is built up
layer by layer, whereas a milled object is cut out of a prefab-
ricated block. The accuracy of a 3D-printed object depends
on how accurately the single layers of printing material are
connected to each other. If the long axis of the object is ori-
ented vertically to the printer platform, more layers of mater-
ial are needed to reproduce the object, and the summation
effect of repeated errors causes inaccuracies to increase.25
However, if the orientation of the object is horizontal, over-
curing of some layers might occur, leading to inaccuracies
due to inhomogeneous polymerization.26 The accuracy of a
milling procedure, on the other hand, is determined by the
diameter of the smallest bur used. When milling concave
surfaces like the intaglios of splints, the radius of the bur
must be smaller than the radius to be milled to ensure that
the piece does not have an oversized geometry.27 One in
vitro study investigating the accuracy of additively manufac-
tured versus milled templates for guided implant surgery
revealed higher accuracy of the latter.28 This is in accordance
with the results of the present study, but our data represent
only theoretical results. In clinical practice, patient- and
treatment-related factors result in various inaccuracies that
may outweigh those of the method of template fabrication
when high manufacturing standards are maintained. Several
factors may influence the accuracy of the GEA. First, the
image quality is dependent on the CBCT device and the
voxel size used. Furthermore, under clinical conditions
motion artefacts even if caused by breathing or muscle
tonus, may decrease accuracy. However, there is substantial
evidence, that GEA can be successfully applied under clinical
conditions despite these limitations.12-15
Ideally, the amount of operator effort required to plan the
drill path using appropriate software should be as low as pos-
sible. The initial purchase of any new software application or
specific add-on tool must be followed by applying the new
technique and evaluating its benefit potential for specific
clinical indications. The present study showed that the Sicat
Endo workflow requires significantly more effort, measured
as the time and number of computer clicks required for plan-
ning the drill path, compared with the CDX workflow. In both
cases, however, the mean time required for virtual planning
of the GEA procedure was < 7.5 min (range: 2.71 to 5.12 min)
per tooth, irrespective of the type of software used. One in
vitro study estimated that the mean treatment time, includ-
ing planning and preparation, is approximately 10 min per
tooth.11 Last but not least, convenient software solutions
without a steep learning curve seem to be mandatory for
realizing an efficient digital workflow for implementing the
GEA procedure in routine daily practice.
Conclusions
Both software packages for GEA planning enabled rapid
planning of the drill path, predictable access cavity prepar-
ation, and reliable location of root canals in teeth with simu-
lated calcification without the incidence of perforation. In
conclusion, both software applications tested in this study
facilitate the accurate and time-saving location and endo-
dontic treatment of calcified root canals according to the GEA
approach in vitro.
Acknowledgements
The authors declare no conflicts of interests relating to this
study. The authors thank Dr. Andrea Beinicke from the
Department of Psychology, Work & Organizational Psycholo-
gy, University of Würzburg (Würzburg, Germany) for her ded-
icated support in performing the statistical analyses. Sicat
GmbH (Bonn, Germany) provided the Sicat Suite software
with licensed access guides, and funded the manufacturing
of the study models and templates.
International Journal of Computerized Dentistry 2020;23(2):1–10 9
Krug et al
References
1. Kiefner P, Connert T, ElAyouti A, Weiger R. Treatment of calcified root
canals in elderly people: a clinical study about the accessibility, the
time needed and the outcome with a three-year follow-up. Gerodon-
to logy 2017; 34:164 –170.
2. Connert T, Krug R, Eggmann F, et al. Guided endodontics versus con-
ventional access cavit y preparation: a comparative stu dy on substance
loss using 3-dimensional- printed teeth. J Endod 2019;45:327–331.
3. Cvek M, Granath L, Lundberg M. Failures and healing in endodonti-
cally treated non-vital anterior teeth with posttraumatically reduced
pulpal lumen. Ac ta Odontol Scand 1982;40:223–228.
4. Krishan R, Paque F, Ossareh A, Kishen A, Dao T, Friedman S. Impac ts
of conservative endodontic c avity on root canal instrumentation effi-
cacy and resistance to fracture assessed in incisors, premolars, and
molars. J Endod 2014;40:1160–1166.
5. Plotino G, Grande NM, Isufi A, et al. Fracture strength of endodonti-
cally treated teeth with different access cavity designs. J Endod
2017;43:995–1000.
6. Wilcox LR, Roskelley C, Sutton T. The relationship of root canal
enlargement to finger-spreader induced vertical root fracture.
J Endod 1997;23:533–534.
7. Zehnder MS, Connert T, Weiger R, Krastl G, Kühl S. Guided endodon-
tics: accurac y of a novel method for guided access cavity preparation
and root canal location. Int Endod J 2016;49:966–972.
8. Krastl G, Zehnder MS, Connert T, Weiger R, Kühl S. Guided Endodon-
tics: a novel treatment approach for teeth with pulp canal calcifica-
tion and apical pathology. Dent Traumatol 2016;32:240–246.
9. Buchgreitz J, Buchgreitz M, Mor tensen D, Bjorndal L. Guided access
cavity preparation using cone -beam computed tomography and
optical surface scans – an ex vivo study. Int Endod J 2016;49:790–795.
10. van der Meer WJ, Vissink A, Ng YL, Gulabivala K. 3D Computer aided
treatment planning in endodontics. J Dent 2016;45:67–72.
11. Connert T, Zehnder MS, Weiger R, Kühl S, Krastl G. Microguided endo -
dontics: accurac y of a miniaturized technique for apically extended
access cavity preparation in anterior teeth. J Endod 2017;43:787–790.
12. Connert T, Zehnder MS, Amato M, Weiger R, Kühl S, Krastl G. Microgu-
ided endodontics: a method to achieve minimally invasive access cav-
ity preparation and root canal location in mandibular incisors using a
novel computer-guided technique. Int Endod J 2018;51:247–255.
13. Mena-Alvarez J, Rico-Romano C, Lobo -Galindo AB, Zubizarreta-Ma-
cho A. Endodontic treatment of dens evaginatus by performing a
splint guided access cavity. J Esthet Restor Dent 2017;29:396–402.
14. Buchgreitz J, Buchgreitz M, Bjorndal L. Guided root canal preparation
using cone beam computed tomography and optical sur face scans –
an observational study of pulp space obliteration and drill path
depth in 50 patients. Int Endod J 2019;52:559–568.
15. Buchgreitz J, Buchgreitz M, Bjorndal L. Guided endodontics modified
for treating molars by using an intracoronal guide technique.
J Endod 2019;45:818–823.
16. Moreno-Rabie C, Torres A, Lambrechts P, Jacobs R. Clinical applica-
tions, accuracy, and limitations of guided endodontics: a systematic
review. Int Endod J 2020;53: 214–231.
17. de Cleen M. Obliteration of pulp canal space after concussion and
subluxation: endodontic considerations. Quintessence Int
2002;33:661–669.
18. Reymus M, Fotiadou C, Kessler A, Heck K, Hickel R, Diegritz C. 3D
printed replicas for endodontic education. Int Endod J 2019;52:
123 –13 0.
19. Wongkhantee S, Patanapiradej V, Maneenut C, Tantbirojn D. Effect of
acidic food and drinks on surface hardness of enamel, dentine, and
tooth-coloured filling materials. J Dent 2006;34:214–220.
20. Schneider D, Marquardt P, Zwahlen M, Jung RE. A systematic review
on the accuracy and the clinical outcome of computer-guided tem-
plate-based implant dentistry. Clin Oral Implants Res 2009;20:73–86.
21. Matta RE, Bergauer B, Adler W, Wichmann M, Nickenig HJ. The imp act
of the fabrication method on the three-dimensional accuracy of an
implant surgery template. J Craniomaxillofac Surg 2017;45:804–808.
22. Kühl S, Payer M , Zitzmann NU, Lambrecht JT, Filippi A. Technical accu-
racy of printed surgical templates for guided implant surgery with
the coDiagnostiX software. Clin Implant Dent Relat Res 2015;17:
177–182.
23. Jung RE, Schneider D, Ganeles J, et al. Computer technology applica-
tions in surgical implant dentistr y: a systematic review. Int J Oral Max-
illofac Implants 2009;24:92–109.
24. Zhou W, Liu Z, Song L, Kuo CL, Shafer DM. Clinical factors affecting
the accuracy of guided implant surgery – a systematic review and
meta-analysis. J Evid Based Dent Pract 2018;18:28–40.
25. Vasques M, L aganá D. Accuracy and internal fit of 3D printed occlusal
splint, according to the printing position. Clin Lab Res Dent 2018:1–6.
26. Barclift MW, Williams CB. Examining variability in the mechanical
properties of parts manufactured via polyjet direct 3D printing.
International Solid Freeform Fabrication Symposium: University of
Texas at Austin, Texas, 2012:6–8.
27. Schaefer O, Kuepper H, Thompson GA, Cachovan G, Hefti AF,
Guentsch A. Effect of CNC-milling on the marginal and internal fit of
dental ceramics: a pilot study. Dent Mater 2013;29:851–858.
28. Park JM , Yi TK, Koak JY, Kim SK, Park EJ, Heo SJ. Comparison of fi ve-ax-
is milling and rapid prototyping for implant surgical templates. Int
J Oral Maxillofac Implants 2014;29:374–383.
International Journal of Computerized Dentistry 2020;23(2):1–10
10
SCIENCE
Guided Endodontics: Eine In-vitro-Vergleichsstudie zur Genauigkeit und zum
Planungsaufwand zwei verschiedener Softwaresysteme
Schlüsselwörter: 3-D-Druck, Bohrschablone, Genauigkeit, Guided Endodontics, Kalzifikation, Obliteration, Trepanation,
Wurzelkanalbehandlung
Zusammenfassung
Ziel: Die Genauigkeit und den Planungsaufwand für den computergestützten Arbeitsablauf der Guided-Endodontics-
Technik (GET) von zwei verschiedenen Softwaresystemen bei 3-D-gedruckten Zähnen mit simulierter Wurzelkanaloblite-
ration in vitro zu vergleichen.
Material und Methoden: Von 32 3-D-gedruckten Frontzähnen mit simulierter Wurzelkanalobliteration wurden jeweils
vier in einem Zahnbogen für Ober- und Unterkiefer angeordnet. Die Datensätze von 3-D-Bildgebung und Oberflächen-
scan dieser Zahnmodelle wurden fusioniert. Es erfolgte die virtuelle Planung und Durchführung der GET durch einen
Behandler anhand zwei verschiedener Systeme: 1.) CoDiagnostiX (CDX, Dental Wings) mit 3-D-gedruckten Bohrschablo-
nen oder 2.) Sicat Endo (SE, Sicat) mit CAD/CAM-gefrästen Bohrschablonen. Die Daten der postoperativen Bildgebung
wurden mit denen der virtuellen Planung zur Analyse überlagert. Die Genauigkeit wurde anhand der Abweichungen von
geplanter zu präparierter Kavität an der Bohrerspitze (in drei Dimensionen, als 3-D-Vektor und Winkel) gemessen. Der
virtuelle Planungsaufwand wurde anhand der aufgewendeten Zeit und der Anzahl der Computerklicks bestimmt. Für
jede Stichprobe wurde das 95%-Konfidenzintervall bestimmt.
Ergebnisse: Mittels SE wurde die GET in allen 16 Wurzelkanälen (100 %) der Zähne erfolgreich angewendet, mittels CDX
in 15 von 16 Fällen (94 %). Es zeigten sich für SE signifikant geringere durchschnittliche Abweichungen an der Bohrerspit-
ze in labial-oraler Richtung von 0,12 mm, für den 3-D-Vektor von 0,35 mm und den Winkel von 0,68° im Vergleich zu den
Abweichungen für CDX (0,54 mm, 0,74 mm, 1,57°; p < 0,001). Sowohl die durchschnittliche Planungszeit als auch der Auf-
wand pro Zahnmodell war für CDX (10 min 50 s, 107 Klicks) geringer als für SE (20 min 28 s, 341 Klicks; p < 0,05).
Schlussfolgerung: Beide Systeme (CDX und SE) ermöglichten die zügige Planung des Bohrpfads, die sichere GET und das
zuverlässige Auffinden obliterierter Wurzelkanäle ohne Perforation.
Ralf Krug, Dr. med. dent.
Status?, Department of Conser vative Dentistry
and Periodontology, Center of Dental Traumatol-
ogy, University Hospital of Würzburg, University
of Würzburg, Würzburg, Germany
Sebastian Reich [author, please supply qualifications]
Status?, Department of Conser vative Dentistry
and Periodontology, Center of Dental Traumatol-
ogy, University Hospital of Würzburg, University
of Würzburg, Würzburg, Germany
Thomas Connert, Dr. med. dent.
Status?, Department of Periodontology, Endodon-
tology and Cariology, University Centre for Dental
Medicine, Universit y of Basel, Basel, Switzerland
Stefan Kess [author, please supply qualifications]
Status?, Department of Orthodontics, University
Hospital of Würzburg, University of Würzburg,
Würzburg, Germany
Sebastian Soliman, Dr. med. dent.
Status?, Department of Conser vative Dentistry
and Periodontology, Center of Dental Traumatol-
ogy, University Hospital of Würzburg, University
of Würzburg, Würzburg, Germany
Status?, Marcel Reymus, Dr. med. dent.
Department of Conservative Dentistry and
Periodontology, Ludwig-Maximilians-University
of Munich, Munich, Germany
Status?, Gabriel Krastl, Prof. Dr. med. dent.
Department of Conservative Dentistry and
Periodontology, Center of Dental Traumatology,
University Hospital of Würzburg, University of
Würzburg, Würzburg, Germany
Ralf Krug
Address Dr. Ralf Krug, Department of Conser vative Dentistry and Periodontology, Universit y Hospital of Würzburg, University of Würzburg,
Pleicherwall 2, 97070 Würzburg, Germany; Tel: +49 931 201 74828; E-mail: krug_r@uk w.de
