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Accuracy of Two Stereolithographic
Guide Systems for Computer-Aided
Implant Placement: A Computed
Tomography-Based Clinical
Comparative Study
Volkan Arısan,* Z. Cuneyt Karabuda,* and Tayfun O
¨zdemir*
Background: Stereolithographic surgical guides provide
significant benefits during the simultaneous placement of
multiple implants with regard to the final prosthetic plan.
However, deviation from the planning poses a significant
risk. Deviations of implants that were placed by bone-,
tooth-, and mucosa-supported stereolithographic surgical
guides were examined in this study.
Methods: After enrolling 54 eligible patients, 294 implants
were planned on cone-beam computerized tomography
CB(CT)-derived images. Sixty guides, both single- and multi-
ple-type, were produced using two commercial systems. Mu-
cosa-supported guides were fixed with osteosynthesis screws.
Implants were inserted, and at the end of osseointegration pe-
riod, a new CB(CT) scan was performed. Preoperative plan-
ning was merged with the new CB(CT) data to identify the
deviations between the planned and placed implants for
each support type and manufacturer. The Kruskal-Wallis
and Mann-Whitney U tests were used for comparison
(P<0.05).
Results: There were no damage-related complications in
any critical anatomy. Implants that were placed by bone-
supported guides had the highest mean deviations (5.0–
1.66angular, and 1.70 –0.52 mm and 1.99 –0.64 mm for
implant shoulder and tip, respectively), whereas the lowest
deviations were measured in implants that were placed by mu-
cosa-supported guides (2.9–0.39angular, and 0.7 –0.13
mm and 0.76 –0.15 mm for implant shoulder and tip, respec-
tively).
Conclusions: Computer-aided planning and manufacturing
surgical guides in accordance with CB(CT) images may help
clinicians place implants. Rigid screw fixation of a single guide
incorporating metal sleeves and a special drill kit further min-
imizes deviations. J Periodontol 2010;81:43-51.
KEY WORDS
Dental implants; surgery, computer-assisted; tomography.
The placement of dental implants
requires precise planning that con-
siders the vital anatomic struc-
tures and restorative goals. The ideal
insertion of multiple implants is chal-
lenging, especially in full edentulous
jaws that lack anatomical landmarks
(e.g., tooth or extraction socket) for the
surgeon’s reference. Diagnosis and
planning using tomography scanning
can be performed, but transferring the
exact plan to the surgical field is not
possible without the use of stereolitho-
graphic guides.
Many stereolithographic guides have
been demonstrated to obtain satisfactory
outcomes.
1-9
Alveolar bone (after a flap
exposure) was the choice of support in
earlier stereolithographic guides, but
there was no depth control of the osteo-
tomy drills.
10
Tooth- or mucosa-supported
guides were then used to insert implants
without the need for flap elevation,
11,12
generating benefits, such as less pain,
edema, and postoperative discomfort.
Hence, the use of a single guide is fa-
vored over multiple guides that must
change for each drill diameter through-
out the surgery.
The use of special drills that have stop-
pers in combination with prefabricated
metal sleeves has allowed the depth
* Departmentof Oral Implant ology, Faculty of Dentistry, Istanbul University, Capa, Istanbul,
Turkey.
indicates supplementary slide presentation (with audio) in the online Journal of
Periodontology. doi: 10.1902/jop.2009.090348
J Periodontol • January 2010
43
and location of drills to be controlled during osteo-
tomy.
13
The accuracy of placed implants, compared
with the planned implants, was a significant concern
for all guide systems.
14
However, the precision of
different systems and guide types under consistent
clinical conditions was not assessed. In this study,
the accuracy of two stereolithographic surgical guide
systems by support type (i.e., bone, tooth, and mu-
cosa) was analyzed and compared.
MATERIALS AND METHODS
Fifty-four patients (38 females and 16 males) who ap-
plied for treatment of tooth loss to the Department of
Oral Implantology, Faculty of Dentistry, Istanbul Uni-
versity, between September 2005 and April 2009
were included in this study. The study was approved
by the local ethical committee and conducted in ac-
cordance with the Helsinki Declaration of 1975, as re-
vised in 2000. The mean age of the patient group was
48.4 (range: 28 to 73) years. Patients with unhealthy
systemic health status, parafunctional habits, poor
oral hygiene, severe alveolar bone deficiencies, un-
controlled diabetes, current irradiation to the head
or neck, psychological disorders, or alcohol, tobacco,
or drug abuse were excluded. Patients gave their
written consent. After the clinical examination, a radi-
opaque scan prosthesis that represented the final
prosthetic outline was produced using an acrylic
and 10% barium sulfate mixture with prefabricated
radiopaque teeth. In full edentulous jaws, the scan
prosthesis was duplicated (acrylic and 10% barium
sulfate mixture) from the existing denture if it repre-
sented the final prosthetic outcome.
Diagnostic Computed Tomography (CT) Imaging
A cone-beam CT (CB[CT]) device
†
with an amor-
phous silicon flat-panel image detector was used for
preoperative imaging. At the loading stage, a new
CB(CT) image was obtained to measure the accuracy
of the implant positions compared with the preopera-
tive planning. All images were obtained using the
standard setup of 120 kilovolt (peak), 3.8 mA with
an exposure time of 40 seconds. After CB(CT) imag-
ing and data acquisition, segmentation of bone and
tooth (if it existed) and scanning prosthesis were per-
formed by an technician who was trained in post-
CB(CT) imaging analysis and segmentation, using
two software programs.
‡§
Surgical Guide Systems
Bone-, tooth-, and mucosa-supported surgical
guides from two commercial manufacturers (system I
i
and system II
¶
) were used in this study. Bone-
supported guides consisted of multiple guides that
were manufactured according to the sequential drill
diameters that were planned for the implant osteo-
tomy. Metal cylinder tubes in the guides determined
the location of the osteotomy. Bone-supported
guides did not have any depth control or stops for
the osteotomy, and the depth of the osteotomy re-
quired visual control by the surgeon carrying out
the drilling. Tooth- and mucosa-supported guides
consisted of single guides that included depth con-
trol. The bone-supported guides required an open
flap reflection; the mucosa- and tooth-supported
guides did not require flap reflection but used a flap-
less/transmucosal approach.
In system I, a slide gauge and tube mechanism
(key lock) controlled the osteotomy, which was de-
signed using software
#
and realistic models of surgi-
cal handpieces and drills (obtained with an optical
scanner**). In system II, a special drill kit that was
used with a changeable metal sleeve controlled the
osteotomy. All guides were manufactured by rapid
prototyping machines accordingtothestereolithog-
raphy principle (Fig. 1).
Computer-Aided Implant Planning
Segmented CB(CT) data were loaded onto personal
computers with the aforementioned software. Im-
plants were planned according to the CB(CT) images
and three-dimensional (3D) reconstruction of the
CB(CT) datasets with regard to the optimal relation
of the scan prosthesis and surrounding anatomy.
The diameter and length of planned implants were
between 3.5 and 4 mm and between 8 and 13 mm, re-
spectively. Jaws that had sufficient alveolar width
(>4.5 mm) were selected for mucosa-supported
guides. For stability, three 2-mm osteosynthesis
screws were also planned on mucosa-supported
guides.
Partially edentulous jaws that had at least one
healthy tooth in the cross-arches were selected for
tooth-supported guides. The remaining jaws were al-
located for bone-supported guides. The guide and im-
plant brands in the study population were equally
distributed in a random manner after the allocation
of patients according to the guide support type. Im-
plant brands were not combined in the same patient.
Computer-aided planning records were generated,
and the final position of the implants in the software
was saved for postoperative comparison. A total of
294 (145 parallel-walled narrow tip form
††
and 149
tapered form
‡‡
) screw-type, self-tapping implants
were planned on 60 surgical guides (system I: 10
† ILUMA, IMTEC Imaging, Ardmore, OK.
‡ Stent CAD, Media Lab, La Spezia, Italy.
§ SimPlant Pro, Materialise Dental, Leuven, Belgium.
iAytasarim (Classic and Otede systems), Kos-gep, ODTU, Ankara,
Turkey.
¶ SimPlant (SurgiGuide and SAFE systems), Materialise Dental.
# Catia, Dassault Systems, Ve
´lizy-Villacoublay Cedex, France.
** Atos So GOM, Braunschweig, Germany.
†† SPI, Element, Thommen Medical, Waldenburg, Switzerland.
‡‡ Xive, DENTSPLY Friadent, Mannheim, Germany.
Accuracy of Two Stereolithographic Guide Systems Volume 81 • Number 1
44
bone-, 10 tooth-, and eight mucosa-supported guides;
system II: 10 bone-, 11 tooth-, and 11 mucosa-
supported guides).
Implant Surgery
After the administration of local anesthesia, a large
flap was elevated and extended beyond the margins
of the bone-supported guides to prevent interference.
Care was taken to ensure the proper seating of the
bone-supported guides on the alveolar bone after
every guide change during the surgery. Tooth-sup-
ported guides were seated and stabilized with the help
of natural teeth. Mucosa-supported guides were
seated over the mucosa using a previously prepared
occlusal bite registration and fixed through previously
planned osteosynthesis screw holes to the underlying
alveolar bone.
Osteotomy was completed according to the drill
sequence of the implant systems, except for system
II tooth- and mucosa-supported guides, which were
used with a special mucotome and 2-mm pilot and
3.15-mm final drill kits. When system II mucosa-
and tooth-supported guides were used, implants were
inserted through the guide by a torque-controlled
surgical handpiece. In the remaining cases, implants
were inserted by a torque-controlled handpiece after
the removal of the guide from the mouth. After the
cover screws or gingival formers were fastened, im-
plants were left to osseointegrate for 1.5 to 5 months,
depending on the anatomical location. All surgeries
were performed by three surgeons with ‡5 years of
experience in implant-placement surgery.
Image Fusion and Measure of the Deviations
A special image-processing software
§§
was used to
match preoperative planning images with postopera-
tive data, using the criteria described by Maes et al.
15
The planning and loading-stage CB(CT) datasets
were converted and imported into the software. Base
(planning) and match (loading-stage CB[CT]) image
series were visualized using the ‘‘3D voxel registra-
tion’’ tool. The two datasets were first fused with the
automated ‘‘register’’ tool. The software allows one
to check and evaluate the correct registration of both
images in the transverse, coronal, and sagittal planes
in the ‘‘fused’’ column window that is placed between
the dataset panes. If the registration was unsuccess-
ful, the images were manually registered using the
‘‘manual,’’ ‘‘threshold,’’ and ‘‘transformation’’ tools.
Implants and the remaining anatomical structures in
the planning- and loading-stage CB(CT) data were
rendered as 3D volumes using the ‘‘render volume’’
tool. Finally, the bone (and teeth, if they existed)
volume was removed, leaving the planned and placed
implant volumes superimposed on the identical
3D spatial image. Merged images were exported
to the planning software. The removal of the bone
(and teeth, if they existed) volume from the 3D
Figure 1.
Systems I (A) and II (B) bone-supported guides consist of multiple guides, including successive drill tubes prepared according to the implant system’s surgical
drill diameters. The surgery proceeds through the successive change of guides after the use of each drill. System I tooth- (C) and mucosa-supported (D)
guides consist of a single guide with direction tubes (arrows) and a custom-manufactured handpiece slide gauge (asterisk). The handpiece slide gauge firmly
attaches tothe head of the contrangle and guides the direction and depthof the osteotomy with the help of an exact-fitting triangle tube slide attached to the
surgical guide. System II tooth- (E) and mucosa-supported (F) guides consist of a single guide, including two metal cylinders, one of which is fixed in the guide
(arrows) and the other of which is changeable (asterisks) according to the special mucotome and drill kit. Mucosa-supported guides were fixed to the
underlying bone with osteosynthesis screws, which were determined using the planning software.
§§ Analyze 9.0, AnalyzeDirect, Lenexa, KS.
J Periodontol • January 2010 Arısan, Karabuda, O
¨zdemir
45
reconstructed model allowed the visualization of the
planned (realistic) and placed (rendered) 3D implant
volumes in different colors. Two points (in the x, y,
and z coordinates) in the implant shoulder and tip
for the planned and placed implants were determined
in the 3D implant volumes. These two points were
connected by a line constituting the ‘‘axis’’ of the im-
plants. Using the pan and zoom features of the soft-
ware, the fused implant volumes were rotated and
magnified at the shoulder, tip, and horizontal aspects
for measurement. Angular deviation (angle between
the axis of the planned and placed implants) and lin-
ear deviation at the implant shoulder (distance be-
tween the coronal centers of the planned and placed
implants) and implant tip (distance between the cen-
ter tip of the planned and placed implants) were mea-
sured (Fig. 2). Measurements were taken on 2 days,
and the averages were recorded.
Statistical Analyses
Sample distribution was not normal in some datasets,
which was determined by the D’Agostino and Pearson
omnibus normality test. The Kruskal-Wallis test with
the Dunn multiple-comparison post test was per-
formed to compare the angular and linear deviations
of implants between guide system and support types.
Deviations of implants according to brands and im-
plants, placed in the maxilla and mandible, were
also compared within the systems using the Mann-
Whitney U test. A logarithmic transformation (square
root) was also performed for non-normal datasets,
and parametric tests (one-way analysis of variance
and ttest) were performed on the aforementioned
comparisons. Both tests yielded similar results and
were confirmatory. All tests were performed using
a software package
ii
on a personal computer, and
P<0.05 was accepted as the level of statistical sig-
nificance.
RESULTS
A total of 294 implants were uneventfully placed
as planned using the software program. Two guides
were fractured during surgery, and the two corre-
sponding patients were excluded from deviation mea-
surements. There was no anesthesia, paresthesia, or
complication to the anatomy related to inaccurately
placed implants.
As the result of one patient who was lost to follow-up
and three early-term implant failures, deviation was
measured in 279 implants. The angular and linear
deviations of implants, based on guide system and
support type, are presented in Table 1 and Figures
3 and 4. The highest mean deviations (5–1.66
and 4.73–1.28angular, 1.70 –0.52 mm and
1.56 –0.25 mm at the implant shoulder, and 1.99 –
0.64 mm and 1.86 –0.4 mm at the implant tip for
systems I and II, respectively) were observed in im-
plants that were placed using bone-supported guides.
There was no statistically significant difference in
the angular and linear deviations between systems I
and II bone-supported guides.
A comparison of the mean deviations of implants
that were placed using tooth-supported guides and
systems I and II revealed that the angular deviation
was 3.5–1.38and 3.39–0.84and the linear de-
viation was 1.31 –0.59 mm and 0.81 –0.33 mm
at the implant shoulder and 1.62 –0.54 mm and
1.01 –0.4 mm at the implant tip, respectively. Linear
Figure 2.
The match between plannedand placed implants. A) Degree: angle difference;shoulder: distance between the centers of the implant shoulders; tip: distance
between the centers of the implant tips. B) Deviation measurement on fused 3D images of presurgical planning and postsurgical CB(CT) scan.
ii GraphPad Prism version 5.00 for Windows, GraphPad Software, San
Diego, CA.
Accuracy of Two Stereolithographic Guide Systems Volume 81 • Number 1
46
deviation differences for implants placed using tooth-
supported guides and systems I and II were sta-
tistically significant. The mean angular and linear
deviations of implants that were placed using system
I mucosa-supported guides were 4.23–0.72and
1.24 –0.51 mm at the implant shoulder and 1.4 –
0.47 mm at the tip, respectively. The smallest angular
and linear deviations were observed for system II
mucosa-supported guides (2.9–0.39and 0.7 –
0.13 mm at the implant shoulder and 0.76 –
0.15 mm at the implant tip), which differed signifi-
cantly from the other guides (Table 2).
The maximum deviation (7.84angular and 3.48
mm at the implant shoulder and 3.8 mm at the im-
plant tip) was measured in implants that were placed
with the system I bone-supported guide, whereas the
minimum deviation (0.8angular and 0.2 mm at
the implant shoulder and 0.4 mm at the implant tip)
was observed for implants placed using the sys-
tem II mucosa-supported guide. The mean linear
deviation at the implant tip was higher than at the
implant shoulder for all guides.
Implants that were placed with single guides (tooth-
and mucosa-supported) had significantly lower
deviations than implants that were placed using
bone-supported multiple guides. Differences in the
angular and linear deviation among system II bone-,
tooth-, and mucosa-supported guides were statisti-
cally significant, except for the shoulder deviation
between tooth- and mucosa-supported guides (Table
3). There were no statistically significant differences
in deviation between implant brands (P<0.08) or
between the maxilla and the mandible (P>0.1) for
any system.
DISCUSSION
As applications for dental implants have increased, so
has the need for ongoing, successful treatment re-
sults. Computer-assisted implant planning on 3D
models allows the optimal assessment and investiga-
tion for implant placement, which is often difficult to
predict prior to the initiation of care. The use of stereo-
lithographic guides for the placement of dental im-
plants is designed to provide greater control and
eliminate the risks that are involved in standard im-
plant surgery. However, the risk for deviation (transfer
error from the software-planning stage to the surgical
field) remains substantial. Analog
16,17
and digital
methods
18,19
have been used to measure deviations,
which makes it difficult to compare results. In vitro
studies are free of confounding clinical factors that
cause movement of the guide and restriction of access
during surgery and increase the deviation. When
a system is applied clinically, the maximum deviation
(which is often not reported in the literature) should be
taken into account, because the incidental contact of
the implant body with any critical anatomical struc-
ture can cause serious complications.
20
In the present study, the angular and linear devia-
tions of implants that were placed by bone-, tooth-,
Ta b l e 1 .
Angular and Linear Deviations of Implants Placed Using Systems I and II Guides
Deviations Guide System Minimum Maximum Mean –SD Guide
Angular deviation () System I 1.2 8.2 5.0 –1.66 Bone-supported
System II 2.9 6.9 4.73 –1.28 Bone-supported
System I 0.9 5.9 3.5 –1.38 Tooth-supported
System II 1.4 4.6 3.39 –0.84 Tooth-supported
System I 2.1 6 4.23 –0.72 Mucosa-supported
System II 0.8 3.5 2.9 –0.39 Mucosa-supported
Linear deviation (mm) Implant shoulder System I 1.2 3.48 1.70 –0.52 Bone-supported
System II 1.1 2.1 1.56 –0.25 Bone-supported
System I 0.6 2.9 1.31 –0.59 Tooth-supported
System II 0.33 1.6 0.81 –0.33 Tooth-supported
System I 0.5 2.7 1.24 –0.51 Mucosa-supported
System II 0.2 0.83 0.7 –0.13 Mucosa-supported
Implant tip System I 1.18 3.8 1.99 –0.64 Bone-supported
System II 1.44 2.6 1.86 –0.4 Bone-supported
System I 0.78 3.4 1.62 –0.54 Tooth-supported
System II 0.29 1.72 1.01 –0.40 Tooth-supported
System I 0.8 2.83 1.4 –0.47 Mucosa-supported
System II 0.4 0.99 0.76 –0.15 Mucosa-supported
J Periodontol • January 2010 Arısan, Karabuda, O
¨zdemir
47
and mucosa-supported stereolithographic guides
from two commercial manufacturers were assessed.
Although the use of system I bone-supported guides
has been demonstrated in flapless surgeries (mucosa
supported),
11,19,21
these guides were used only in
open surgeries for better control of osteotomy depth
and alignment of the drill entry with the use of succes-
sive guides. Previous articles
19,22
reported a range of
4.63to 5.1for angular deviation, 1.28 to 1.57 mm
for linear deviation in the implant shoulder, and 1.3
to 1.6 mm for linear deviation in the implant tip for
system I bone-supported guides, whereas for sys-
tem II bone-supported guides, the values were
7.25to 10, 1.45 to 1.50 mm, and 2.99 to 4.7 mm,
respectively.
1,23
A human cadaver study by van Steenberghe
et al.,
24
with preoperative data and postoperative
CT scans, compared the deviations of six zygoma
implants that were placed using bone-supported
drilling guides. The angular deviation ranged from
0.61to 6.93, and the linear deviation ranged from
0.8 to 7.9 mm in the entry point to the maxilla and
from 0.2 to 6 mm in the exit at the zygoma. Another
recent in vivo study
21
reported a range of 0.7
to 24.9for angular deviation and 0.2 to 6.5 mm
(shoulder) and 0.0 to 6.9 (tip) mm for linear devia-
tions in 89 implants that were placed with system II,
multi-type guides, as in the present study. Deviation
values of the bone-supported guides that were used
in this study are consistent with those of previous
reports
19,21,23,24
, and there was no statistically signif-
icant difference between systems I and II. Occasion-
ally, the pilot drill slid out from the thin
cortical plane when using the bone-
supported guides. The increased devia-
tions in bone-supported guides may be
related to this phenomenon.
However, maximum error values
(depicted as dot outliers in Figs. 3 and
4) should be considered for any clinical
circumstance. The lack of depth stops
in systems I and II bone-supported
guides demands further attention from
the surgeon, and it can increase linear
deviations. Furthermore, changing the
guide after the use of each drill can also
cause deviations. The authors agree
that the use of multiple guide systems
that lack depth control should be re-
stricted to open surgeries only.
The use of a single guide throughout
an osteotomy has been recommended
to reduce deviations.
14
Integration of
a depth-control mechanism can also
ensure a safe osteotomy and accurate
positioning of the implants. In a human
cadaver study by van Assche et al.,
18
an angular de-
viation of 0.7to 4and linear deviations of 0.3 to 2.3
mm (shoulder) and 0.3 to 2.4 mm (tip) were reported
in 12 implants that were placed by single guides with
depth control (used in this study as system II tooth-
and mucosa-supported guides). Smaller deviations
were observed with tooth-supported guides, and
screw fixation of the guide was recommended to re-
duce errors. Tooth-supported guides had lower an-
gular and linear deviations than bone-supported
guides; the differences were statistically significant
for both systems in this study. The lowest deviations
were reported for tooth-supported guides in several
Figure 3.
Box plots showing median quartile and extreme values (depicted as dot
outliers) for angular deviations of implants placed using systems I and II
guides. Blue: bone-supported guides; yellow: tooth-supported guides; red:
mucosa-supported guides.
Figure 4.
Box plots showing median, quartile, and extreme values (depicted as dot outliers) for linear
deviations in the shoulder and tip of implants placed using systems I and II guides. Blue: bone-
supported guides; yellow: tooth-supported guides; red: mucosa-supported guides.
Accuracy of Two Stereolithographic Guide Systems Volume 81 • Number 1
48
studies.
18,19,22
However, because of variations in the
stereolithographic systems and the number of exist-
ing teeth, it is difficult to make comparisons with the
results of this study. The authors conclude that the
use of two or more immobile teeth for the support of
single guides reduces deviations.
The deviations of implants that were placed by mu-
cosa-supported guides were lower in this study, most
likely as the result of the lack of interference or slight
guide movements in fully edentulous cases in which
the guides were firmly fixed by osteosynthesis screws.
The smallest deviations were observed for implants
that were placed using system II mucosa-supported
guides; the differences were statistically significant
compared to the other guides. More importantly, var-
iations from the mean were also minimal. The use of
a specific drill kit also probably contributed to this re-
sult.
13,25
In a cadaver and human study by van Steenberghe
et al.
9
using system II guides, a mean angular devia-
tion of 0.8–0.3(1.4maximum) and linear devia-
tions of 0.3 –0.1 mm at the implant shoulder (1.5
mm maximum) and 0.9 –0.3 mm at the implant tip
(3.8 mm maximum) were reported for 16 implants;
these data are comparable with the results from the
present study.
A recent clinical study by Valente et al.
21
demon-
strated better accuracy with regard to the apical
deviation of mucosa-supported guides compared
with tooth-supported guides and between completely
edentulous patients and partially edentulous patients.
Although the linear deviations using system I mucosa-
supported guides were slightly lower than when
using system I bone- and tooth-supported guides,
the differences were not statistically significant.
This result could be related to the insufficient rigidity
of the slide gauge and improper fit of the guide
on the mucosa because of interference with the slide
tubes. Because the use of mucosa-supported guides
is a blind technique, it is paramount to reduce
Ta b l e 2 .
Statistical Comparison of Deviation Differences Within Systems I and II
System I System II
Deviations
Bone- Versus
Tooth-
Supported
Bone- Versus
Mucosa-
Supported
Tooth- Versus
Mucosa-
Supported
Bone- Versus
Tooth-
Supported
Bone- Versus
Mucosa-
Supported
Tooth- Versus
Mucosa-
Supported
Angular deviation P<0.05 NS NS P<0.05 P<0.001 P<0.05
Linear deviation at implant
shoulder
P<0.05 P<0.05 NS P<0.05 P<0.001 NS
Linear deviation at implant tip NS P<0.05 NS P<0.001 P<0.001 P<0.05
NS, not statistically significant.
Ta b l e 3 .
Statistical Comparison of Deviation Differences Between Systems I and II
System II
Bone-Supported Tooth-Supported Mucosa-Supported
Angular Shoulder Tip Angular Shoulder Tip Angular Shoulder Tip
System I Bone-supported Angular NS – – P<0.001 – – P<0.001 – –
Shoulder – NS – – P<0.001 – – P<0.001 –
Tip – – NS – – P<0.001 – – P<0.001
Tooth-supported Angular P<0.05 – – NS – – P<0.001 – –
Shoulder – NS – – P<0.05 – – P<0.001 –
Tip – – NS – – P<0.05 – – P<0.001
Mucosa-supported Angular NS – – P<0.05 – – P<0.001 – –
Shoulder – P<0.05 – – P<0.001 – – P<0.05 –
Tip – – NS – – P<0.001 – – P<0.001
NS, not statistically significant.
J Periodontol • January 2010 Arısan, Karabuda, O
¨zdemir
49
deviations and maximum error values (outliers in
Figs. 3 and 4).
Another noteworthy finding was that the mean de-
viations in the implant tip were higher than in the
shoulder for all guides. Deviation at the shoulder
should be less, because of the lack of angular devia-
tion, which is added by drilling farther into the bone
in the implant tip. A confounding factor may be the
use of parallel-walled (cylindrical) or tapered-design
drills. The freedom of movement and possibility of de-
viation (especially on bone entry point) may be
greater in tapered-design drills. The deviation at the
tip of the implant may be more important, because
the tip is near critical anatomy.
The deviations that were investigated in this study
are generated from the cumulative sum of all errors
throughout the ‘‘computer-aided implant placement’’
cascade; they include CB(CT) imaging (acquisition
and reliability);
26
software planning (conversion, seg-
mentation, volume rendering, and manual removal of
artifacts); guide manufacturing (simulation software
or method before production, precision of the stereo-
lithographic machine, production and quality control,
rigidity and physical properties of the material used,
placement method and precision of the guide cylin-
ders, metal tubes, and verification of the guide);
9
proper guide positioning in the mouth (flap interven-
tion, improper or tilted seating, and resilience of the
anatomical structures that supported the guide);
guide fixation (angle, location, and the number fixa-
tion screws); rotational allowance of drills in tubes;
shape (straight or tapered) and sharpness of the drills;
first entry point;
21
and mouth opening. Improvement
in any stage of these factors can reduce deviations.
With the introduction of low-dose CB(CT), radia-
tion dose concerns that have been associated with
CT were diminished.
27,28
For instance, the effective
radiation dose of the CB(CT) scanner that was used
in this study was ;58 mSv,
29
compared with an esti-
mated 1,000 mSv with conventional CT.
28
Compared
with panoramic x-rays (23.2 mSv), the level of irradi-
ation that is associated with CB(CT) scanners can be
regarded as acceptable.
30
CONCLUSIONS
Computer-aided planning and manufacturing of sur-
gical guides in accordance with CB(CT) images can
help clinicians to place implants. Rigid screw fixation
of a single guide incorporating metal sleeves and
a special drill kit further minimizes deviations.
ACKNOWLEDGMENTS
The authors thank Dr. Sevda O
¨zel, Department of
Biostatistics, Faculty of Medicine, Istanbul University,
for her assistance with this study. All authors are
full-time academic staff and declare no conflicts of
interest in relation to any brand, device, or entity
mentioned in this study. This study was sponsored,
in part, by RISUS Medical (Turkish Branch of
Thommen Medical, SPI, Waldenburg, Switzerland)
and DENTSPLY Friadent (Istanbul).
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Correspondence: Dr. Volkan Arısan, Department of Oral
Implantology, Faculty of Dentistry, Istanbul University,
34390-Capa, Istanbul, Turkey. Fax: 90-212-5323254;
e-mail: varisan@istanbul.edu.tr.
Submitted June 17, 2009; accepted for publication August
12, 2009.
J Periodontol • January 2010 Arısan, Karabuda, O
¨zdemir
51
