An Accuracy Study of Computer-Planned Implant Placement in the Augmented Maxilla Using Mucosa-Supported Surgical Templates

An Accuracy Study of Computer-Planned ImplantPlacement in the Augmented Maxilla UsingMucosa-Supported Surgical TemplatesLuc M. Verhamme, MSc, BEng;* Gert J. Meijer, DMD, PhD;*,† Stefaan J. Bergé, MD, DMD, PhD;*

Rik A. Soehardi, MD, DMD, PhD;* Tong Xi, MD, DMD;* Anton F.J. de Haan, MSc;‡ Filip Schutyser, Msc;§

Thomas J.J. Maal, MSc, PhD*

ABSTRACT

Purpose: The purpose of this study was to determine the clinically relevant accuracy of implant placement in the augmentedmaxilla using computer planning and a mucosa-supported surgical template.

Materials and Methods: Twenty-five consecutive edentulous patients with an extreme maxillar alveolar ridge resorptionwere treated with a bone augmentation procedure. In a second stage, six Brånemark MkIII Groovy (Nobel Biocare®,Zürich, Switzerland) implants were installed. Preoperatively, a cone beam computer tomography (CBCT) scan wasacquired, followed by virtual implant planning and flapless implant placement using a surgical template. A postoperativeCBCT scan was acquired and registered to the preoperative scan. The Implant Position Orthogonal Projection validationmethod was applied to measure implant deviations in both the buccolingual and mesio-distal plane. The influence offixation pins and the position on the dental arch were investigated with regard to implant deviations, and rotations andtranslations of the surgical template.

Results: One hundred fifty implants were installed. In mesio-distal direction, a mean implant deviation of 1.50 mm wasscored at the implant tip, 1.27 mm at the shoulder, −0.60 mm in depth, as well as a mean deviation of angulation of 2.50°.In buccolingual direction, a mean implant deviation of 0.99 mm was found at the implant tip, 0.76 mm at the implantshoulder, −0.57 mm in depth, and a deviation of angulation of 2.48°. Of all implants, 53% was placed too superficialcompared with the planning. The use of fixation pins and implant deviations in both buccal and mesial directions as alsofor rotations and translation of the surgical template showed statistically significant differences.

Conclusions: Computer-aided implant planning showed to be a clinically relevant tool. However, this study emphasizes thatthe surgeon should take into account that deviations are larger compared with implant placement without augmentationprocedure. Deviations are mainly caused by angulations and translations of the surgical template.

KEY WORDS: accuracy, atrophic maxilla, bone augmentation, CAD/CAM technology, computer-assisted, cone beam CT,edentulous maxilla, flapless implant surgery, sinus floor elevation, surgical guides

INTRODUCTION

Maxillar edentulous patients may suffer from extreme

alveolar ridge resorption. In those cases, even using

state-of-the-art virtual implant planning systems like

image-guided navigation and surgical templates, it is

often impossible to find a stable osseous environment

for implant placement. To create a stable bone bed

allowing implant placement, a bone augmentation

procedure is advised. As this procedure changes the

soft tissue anatomy seriously, the effect on accuracy of

*Department of Oral and Maxillofacial Surgery, Radboud UniversityNijmegen Medical Centre, Nijmegen, The Netherlands; †Departmentof Implantology and Periodontology, Radboud University NijmegenMedical Centre, Nijmegen, The Netherlands; ‡Department for HealthEvidence, Biostatistics group, Radboud University Nijmegen MedicalCentre, Nijmegen, The Netherlands; §Nobel Biocare c/o Medicim NV,Mechelen, Belgium

Corresponding Author: Mr. Luc Verhamme, Department of Oral andMaxillofacial Surgery, Radboud University Nijmegen Medical Centre,P.O. Box 9101, 6500 HB Nijmegen, 590, The Netherlands; e-mail:[email protected]

© 2014 Wiley Periodicals, Inc.

DOI 10.1111/cid.12230

1

mucosa-supported surgical templates should be studied

thoroughly. To the best knowledge of the authors, no

other studies on implant accuracy after augmentation of

the maxilla are previously reported.

AIM

The aim of this study is to evaluate the accuracy of

virtually planned implants in the augmented maxilla in

a clinically relevant manner.

MATERIALS AND METHODS

Patients

In this prospective study, 25 edentulous patients were

enrolled. All patients showed extreme atrophy of their

edentulous upper jaws; the height and/or width of the

alveolar ridge were less than 5 mm.

Augmentation Procedure

Harvesting Iliac Bone Grafts. All surgical procedures

were performed by one and the same surgeon (G.J.M.).

As iliac crest bone grafts were harvested, surgery was

performed under general anesthesia, implicating a two-

stage procedure; 6 months after the augmentation, the

implants were installed.

Patients were placed in a supine position with a hip

roll placed to expose the anterior superior iliac spine

(ASIS). While stretching the skin in a supero-medial

direction, an incision was made 1.5 cm posterior to the

ASIS to reduce the risk of injury to the lateral cutaneous

femoral nerve. After exposing its medial cortex, instead

of harvesting one mono-cortical corticocancellous

bone graft, four vertically orientated bone strips were

removed using reciprocating surgical saw. Hereafter,

additional cancellous bone chips were scraped out with

curettes. After applying Ostene™ (Apatech Limited,

Hertfordshire, UK), a resorbable bone wax, a hemostatic

material (Spongostan™, Ferrosan Medical Devices A/S,

Søborg, Denmark) was applied at the donor site. Sub-

sequently, the wound was closed in layers.

Maxillary Augmentation Procedure. After infiltration

with a local anesthetic (Ultracain® D-S forte, Sanofi-

Aventis, Gouda, the Netherlands) containing epineph-

rine as a vasoconstrictor, the palatal mucosa was incised,

just below and parallel to the top of the alveolar crest.

In the second molar region, a vertical releasing incision

was made. First, a sinus floor elevation procedure was

performed.1,2 The created sinus cavities were filled with

cancellous bone chips. To broaden the alveolar ridge, the

harvested corticocancellous bone strips were positioned

in an imbricated manner and fixated with osteosyn-

thesis screws (2.0 mm Champy-System, KLS Martin,

Tüttingen, Germany). Before closure, the base of the

periosteal flap was incised horizontally to enable ten-

sionless closure of the soft tissues after fixation of the

bone strips.

Scanning Procedure

One month before implant installation, cone beam

computed tomography (CBCT) scans were acquired

using the i-CAT® 3D Imaging System (Imaging Sciences

International Inc., Hatfield, PA, USA) according to the

double scan procedure.3 As such, the relation between

bony structures and the denture (and later surgical

template) was acquired.3,4 In case of a nonoptimal fit

between reconstructed maxilla and denture, the latter

was relined first. Both CBCT scans were acquired using

a setting of 120 kV peak, pulses of 3–8 mA, 8 cm scan

height, exposure time of 20 seconds and were recon-

structed with 0.3 mm isotropic voxel size. While scan-

ning, no bite index was used.

Both scans were then loaded into the Procera Clini-

cal Design® software (Nobel Biocare®, Zürich, Switzer-

land), and three-dimensional reconstructions of the

bony structures and denture were created and registered.

Implant Planning

Six Brånemark MkIII Groovy (Nobel Biocare) implants

were planned using the Procera Clinical Design software

(Nobel Biocare) with respect to the available bone

volume and prosthetic aspects. All implants were

planned in such a way that at least the tip of the implants

was positioned in the original maxillary bone. In addi-

tion, a minimum of at least 2 mm buccal and palatal

bone should be present around the implant. The plan-

ning and use of fixation pins were applied in the first

cases but abandoned in more recent cases as they hin-

dered surgeons in their performance. Based on this

virtual planning, a stereolithographic surgical template

was ordered from Nobel Biocare® (Gothenburg,

Sweden).5,6

Implant Placement

During the implant placement procedure, all patients

received general nasotracheal anesthesia. To avoid

2 Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014

interference with the swelling initiated by using addi-

tional local anesthesia, such was not applied. The osteo-

synthesis screws installed during the augmentation

procedure were removed through small incision at the

head of the screws. Implant installation was performed

according to the NobelGuide® procedure. If possible,

fixation pins were used, connecting the template to the

underlying bone. However, in particular cases, the pins

hindered implant installation. If so, the surgical tem-

plate was held in position only by giving digital pressure

with the middle finger and/or forefinger to the central

palatal part of the surgical template.

An augmentation procedure, using bone blocks,

automatically implicates an increase in bone volume

that had to be protected by the buccal mucosa. This also

results in a shift of the keratinized mucosa to the palatal

side. After placement of the implants, independently of

the fat, an extra surgical procedure is needed to bring the

keratinized mucosa to the buccal side of the implant.

Implant Validation

A postoperative CBCT scan was acquired within 2 weeks

after implant installation. This was performed using the

same settings as the preoperative scan. Both scans were

imported into the NobelGuide Validation software

(version 2.0.0.4, Medicim NV, Mechelen, Belgium) and

processed. Subsequently, the implant coordinates of the

implant tip and shoulder were calculated in the three-

dimensional space. Using the Implant Orthogonal

Projection validation method,4 the clinically rele-

vant implant deviations in the mesio-distal (MD) and

buccolingual (BL) direction were calculated. The vari-

ables “implant tip,” “implant shoulder,” “angulation,”

and “depth” were then calculated, both in three-

dimensional and in BL and MD directions.

Translations and Rotation of theSurgical Template

Possible rotations and translations of the surgical

template during surgery were tracked postoperatively.

The postoperative implant positions were, as a whole,

rotated and translated back to the planned implant posi-

tion using the Iterative Closest Point computer algo-

rithm.7 This algorithm searches for a best fit between the

two implant sets and from these results, the rotations

around the X, Y, and Z axes (pitch, roll, and yaw, respec-

tively) and translations of the template were calculated

as Euler angles (Figure 1).

It was therefore assumed that interimplant dis-

tances stayed equal in both planning and postoperative

situation.

Evaluation

Both the deviations between planned and postoperative

implant placement as well rotations and translations of

the surgical template were evaluated for implant place-

ment with or without fixation pins. In addition, it was

evaluated whether the implant tip and implant shoulder

moved in a BL, MD, or diagonal way. If both implant

tip and shoulder moved in the same direction, this

was interpreted as a complete movement. When tip and

shoulder moved in an opposite direction, this was con-

sidered as diagonal movement. For all movements, a

deviation threshold value of 0.5 mm was used.

Statistical Analysis

Linear mixed models were involved to analyze the in-

fluence of the implant parameters on the deviations

between planned and postoperative implant positions.

In this model, a random patient intercept was used with

the influence of implant characteristics as a fixed factor.

When a statistically significant effect was found for a

factor, a Bonferroni pair wise comparison was per-

formed to evaluate between which factors (e.g., buccal vs

lingual vs diagonal, fixation pins vs no fixation pins, etc.)

a specific statistically significant difference occurred.8

Following factors were analyzed separately to inves-

tigate their influence on the implant deviation para-

meter: BL position, MD position, position on dental

arch, use of fixation pins, implant length, rotations of

the surgical template, and translations of the surgical

Figure 1 Pitch (A), roll (B), and yaw (C) between the plannedimplant positions (green) compared with the installed implantpositions (blue).

Accuracy of Implant Placement in the Augmented Maxilla 3

template. All statistical analyses were performed using

SAS (SAS Institute Inc., Cary, NC, USA). Statistical com-

parisons were considered statistically significant when

the p value was <.05.

RESULTS

A total of 150 implants were installed in 25 patients (13

females, 12 males) with ages ranging from 45 to 79 years

and a mean age of 59.1 years. Fixation pins were used

in 11 patients, while in 14 cases, no fixation pins were

applied (Table 1).

Mean deviations at the implant tip were

1.494 mm 1 0.238 in MD direction, 0.987 mm 1 0.142

in BL direction, and 2.288 mm 1 0.269 in three-

dimensional direction. Mean deviations at the implant

shoulder were 1.270 mm 1 0.217 in MD direction,

0.757 mm 1 0.092 in BL direction, and 1.963 mm 1

0.232 in three-dimensional direction. Mean angular

deviations were 2.504° 1 0.292 in MD direction,

2.484° 1 0.290 in BL direction, and 3.926° 1 0.414 in

three-dimensional direction. Mean depth deviations

were −0.602 mm 1 0.161 in MD direction, −0.571 mm 1

0.148 in BL direction, and −0.584 mm 1 0.155 in three-

dimensional direction.

An overview of mean implant deviations including

95% confidence intervals is provided in Table 2 and

Figure 2.

The implant position on the dental arch showed no

statistical significant difference for any variable. The use

of fixation pins only showed a statistical significant dif-

ference for a BL implant shoulder deviation (p = .0465).

Implant length showed a statistical significant difference

for angular deviation in MD direction (p = .0256).

For the effect of BL position, statistically significant

differences were seen at the implant tip (p range 2 .0001

TABLE 1 Subdivision of the Total Number ofImplants per Effect

Effectn

Implants Percentage

Buccolingual

deviation

Less than 0.5 mm 43 28.7%

Buccal >0.5 mm 51 34.0%

Lingual >0.5 mm 42 28.0%

Diagonal >0.5 mm 14 9.3%

Mesio-distal

deviation

Less than 0.5 mm 28 18.7%

Mesial >0.5 mm 90 60.0%

Distal >0.5 mm 25 16.7%

Diagonal >0.5 mm 7 4.7%

Position on

dental arch

Regions 13–14 25 16.7%

Regions 14–15 25 16.7%

Regions 15–16 25 16.7%

Regions 23–24 25 16.7%

Regions 24–25 25 16.7%

Regions 25–26 25 16.7%

Use of fixation

pins

Pins 66 44.0%

No Pins 84 56.0%

Implant length 8.5 mm 0 0.0%

10.0 mm 28 18.7%

11.5 mm 65 43.3%

13.0 mm 48 32.0%

15.0 mm 9 6.0%

TABLE 2 Mean Deviations and Mesio-Distal (MD), Buccolingual (BL), Three-Dimensional Deviations

MD BL Three-Dimensional

Tip (mm) Mean 1.494 0.987 2.288

95% CI 0.466 0.279 0.528

Max 7.231 4.720 8.729

Shoulder (mm) Mean 1.270 0.757 1.963

95% CI 0.425 0.180 0.4553

Max 7.060 3.088 7.815

Angle (°) Mean 2.5041 2.484 3.926

95% CI 0.573 0.568 0.812

Max 12.834 19.057 19.781

Depth (mm) Mean −0.602 −0.571 −0.584

95% CI 0.315 0.291 0.304

Max −4.119 −4.102 −4.107

CI = confidence interval.

4 Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014

to .0298), shoulder (p range 2 .0001 to .0465), and

angular (p range 2 .0001 to .0385) deviations between

the virtually planned implant positions and actually

placed implant positions.

For the effect of MD position, statistically signifi-

cant differences were seen at the implant tip (p range 2

.0001 to .0388), shoulder (p range = .0001 to .0193),

angular (p range 2 .0001 to .0006), and implant place-

ment depth (p = .0433) deviations.

For the outcome of depth deviation, 23.7% of all

implants were placed >0.5 mm too deep, 52.7% were

placed >0.5 mm too superficial, and 23.6% were placed

within a margin of 0.5 mm.

Rotations of the surgical template showed no statis-

tically significant differences for the pitch direction of

rotation. Roll showed a statistical significant difference

for angular deviation in the MD direction (p = .0089).

Yaw showed statistically significant differences at

implant tip (p = .0248) and angular deviation (p =.0249) in the BL direction and angular deviation

(p = .0451) in the MD direction (Table 3).

Translations of the surgical template in medial-

lateral direction showed statistically significant differ-

ences at implant tip (p = .0048) and implant shoulder

(p = .0028) in the BL direction. In MD direction, statis-

tically significant differences were found for the implant

tip (p = .0345).

Translation of the surgical template in anterior-

posterior direction showed statistically significant differ-

ences at implant tip (p = .0164) and implant shoulder

(p = .0040) in the BL direction and no statistically sig-

nificant differences in the MD direction.

Translations of the surgical template in cranial-

caudal direction showed statistically significant differ-

ences at implant depth deviation (p = .0001) in the BL

direction and the implant angular (p = .0113) and depth

deviation (p = .0001) in MD direction (Table 4).

DISCUSSION

Computer-aided implant planning based on CBCT

combined with stereolithographic surgical templates for

implant placement showed favorable results over the last

years in terms of accuracy, implant survival rates, and

patient friendliness.9–11

Figure 2 Graphical overview of the mean deviation results and95% confidence interval in buccolingual, mesio-distal, andthree-dimensional directions.

TABLE 3 Overview of Rotational Deviations of theSurgical Template

Pitch (°) Roll (°) Yaw (°)

Mean > 0 1.96 1.27 1.61

Mean < 0 N/A −1.27 N/A

Minimum 0.30 −4.79 0.18

Maximum 5.98 4.42 4.94

Positive pitch represents the implant tip rotated in distal direction; posi-tive roll represents a clockwise rotation from the patients’ perspective;positive yaw represents a counter-clockwise rotation from the patients’perspective.N/A = not applicable.

Accuracy of Implant Placement in the Augmented Maxilla 5

To the best knowledge of the authors, no studies

were performed on the accuracy of virtually planned

implant placement in the fully edentulous maxilla

after an augmentation procedure. Also, in contrast to

many other accuracy studies without augmentation

procedure,5,12–26 the result of this study was interpreted

in a clinically relevant manner by decomposing three-

dimensional results into the BL and MD directions.

System Accuracy

From patient scan to validation of implant accuracy,

many factors of inaccuracy are introduced in the stages

of image acquisition,27–31 image processing and plan-

ning,4,32 the production of surgical templates,4,27,33,34

during implant placement,4,16,35,36 and in the validation

process.4,37

With regard to surgical instruments used during

implant placement, most authors agree that deviations

are introduced because of discrepancy between the

template sleeve, drill guide, and drill, which is needed to

prevent too much friction between the instruments.

Koop and colleagues35 and Van Assche and Quirynen38

notice that a parallel and central positioning of the drill

guide is crucial. However, a limited mouth opening

might cause the drill head to be inclined more mesial or

palatinal.38–40

To reduce these systematic deviations, among

others, Koop and colleagues35 investigated the tolerance

within the sleeve inserts of different surgical guides and

advise to use longer drill sleeves and inserts to improve

accuracy. This will surely reduce the deviation caused by

angulation between the drill and drill guidance sleeve,

but at the same time will require a larger mouth opening

to introduce the drill and, as such, introduce new devia-

tion as previously mentioned.

Cassetta and colleagues41 did perform research on

reducing the error induced by the mechanical compo-

nents. To reduce the error that is introduced between

the drill and the drill guide, they introduced a guiding

system fixed to the drill head.

In literature, no other studies performed calcula-

tions on the improper position of the surgical template.

However, the method used in this publication to

perform these calculations also influences the final

outcome. The used Euler rotations are noncommutative,

meaning that the order (pitch – roll – yaw) at which the

angles are applied does matter. Using a different order

(e.g., yaw – roll – pitch) with the same angles would

yield a different result. This means that when comparing

the angular deviations of the surgical template of this

study with future studies, the order of angles should be

taken into account to make an objective comparison.

The assumption that interimplant distance is equal

between the planning and postoperative situation is not

valid for any of the cases. In some cases, one implant

has slightly larger deviations or in a different direction

than the other implants. It was assumed that this does

not significantly influence the results. Furthermore, the

main intention of evaluating rotations and translations

of the surgical template was not to obtain exact values

for angular and translational motion of specific

implants, but to obtain more knowledge of the move-

ments of the surgical template during surgery during

implant placement in an augmented maxilla.

Fixation Pins

As of all tip and shoulder deviation in both BL and MD

directions, only for the shoulder deviation in BL direc-

tion a slightly statistical significant difference was found

for the use of fixation pins. This means that this study

is consistent with the authors’ accuracy study on the

placement of two or four implants in the edentulous

maxilla.40 It was found that fixation pins provide no

additional stability to the surgical template and there-

fore do not result in a more accurate transfer from

implant planning to implant placement. This could

possibly be caused by the resilience of the mucosa or

fixation of the surgical template with a small deviation

from the planned location.

Similar to the previous accuracy study by Verhamme

and colleagues,42 no bite index was used because of the

absence or poor fit of a denture in the mandible and the

use of general anesthesia with muscle relaxants. By not

using fixation pins, the surgeon has the advantage to

continuously receive haptic feedback of the position of

TABLE 4 Overview of Translational Deviations ofthe Surgical Template

MeanMedial/Lateral(mm)

MeanAnterior/Posterior

(mm)

MeanCranial/Caudal(mm)

Right/anterior/caudal 2.61 2.66 3.88

Left/posterior/cranial 1.40 3.38 2.50

Minimum −3.88 −11.36 −6.54

Maximum 12.75 11.55 8.13

6 Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014

the surgical template and is not hindered by the fixation

pins during surgery.

Some studies describe that the position of the

fixation pins is very critical with respect to placements

in anterior/posterior region,14,16,17 but a very limited

number of studies compared the accuracy of implant

placement in relation with the use of fixation pins. In the

study of Cassetta and colleagues,43 the use of fixation

pins was investigated as part of the discussion on intrin-

sic error of Simplant® stereolithographic surgical tem-

plates. They found a statistically significant difference

in angular deviation between the use of at least three

fixation pins (SAFE System®, Fixed, Materialise Dental

N.V., Leuven, Belgium) compared with no fixation pins.

At first, it is doubtful how accurate the calculation of

implant deviation is, as three-dimensional deviations

were calculated instead of more clinically relevant

results. Furthermore, the population in the Cassetta

study consists of both fully and partial edentulous

patients receiving implants in both the maxilla and

mandible.

Finally, as also mentioned by Vrielinck and col-

leagues,25 it is of major importance that when fixation

pins are placed, this should be performed with an evenly

distributed pressure to keep the surgical template pro-

perly balanced.

Implant Deviations

Depth. In the present study, more than half of the

implants were placed >0.5 mm too superficial. This

could be the result of drilling debris in the bone cavi-

ties or a problem with regard to setting the optimal

threshold value while generating the three-dimensional

model of the surgical template that will be used in

the stereolithographic printing process.40 However, as

reported by Van Assche and colleagues,36 limited infor-

mation is available on depth deviation when using a

virtual implant planning system for implant placement.

When depth information is available, it is often unclear

how the depth deviation is exactly calculated and how

clinically relevant the specific method for calculating the

depth deviation is.

Cassetta and colleagues43 investigated depth devia-

tion of 111 implants in both the maxilla and mandible

using preoperative and postoperative computer tomog-

raphy scans and measured the bone density at the

implant location. Consistent with the results of the

present study, they found that most of the implants were

placed too superficial. Cassetta and colleagues also found

a significant linear correlation between depth deviation

and bone density. This was not evaluated in the present

study, as this was based on CBCT data, making it inca-

pable for proper bone density measurements.

In contrast to the results of the present study,

Stubinger and colleagues found a statistically significant

difference between depth deviations compared with

mesial or more distal implant locations. A larger depth

deviation was found for implants placed more distally.

BL and MD Deviations. To broaden the alveolar ridge,

harvested corticocancellous bone strips were positioned

at the buccal side of the original alveolar ridge. To allow

tensionless closure of the soft tissues, the periosteal base

of the raised mucoperiosteal flap was incised horizon-

tally. A negative side effect is that the buccal vestibule

becomes less deepened, providing less support to the

surgical template.

During implant planning, it was attempted to plan

the implant tip within the original bone of the resorbed

maxilla and in general, to surround the implant by at

least 2 mm of bone. The results showed an almost equal

deviation for both the implant tip and shoulder devia-

tion. In BL direction, some of these deviations are in the

opposite direction for tip and shoulder and previously

described as diagonal implant placement. In BL direc-

tion, more implants were placed in a diagonal fashion

compared with the MD direction. This might be caused

by deflection/angulation of the drill by the cortical bone

at the border between augmented bone and original

bone (Figure 3).

At the implant tip, in MD direction, larger deviations

were found compared with BL direction. This might be

caused by the rotations of the surgical template.

Figure 3 Difference between planned and actual drillingsituation in both non-augmented and augmented maxilla. A,Drilling in a conventional non-augmented maxilla; B1, Planneddrilling procedure in an augmented maxilla; B2, Actual drillingsituation in an augmented maxilla with the drilling directionbeing changed by the cortical outline of the maxilla.

Accuracy of Implant Placement in the Augmented Maxilla 7

Rotations and Translations of the Surgical Template.

Pitch and roll of the surgical template showed no statis-

tically significant differences for any of the implants

deviation parameters. This is logical, as the rotations, if

not too obvious, take place in line with the implant.

Looking at the yaw of the surgical template, statistically

significant differences were found for most deviation

parameters except depth. This can be explained as yaw

is a movement in the axial plane, and thus mainly per-

pendicular to the direction of implant placement.

For all cases, pitch was only seen in one direction

with the implant tip deviation more too dorsal com-

pared with the planned implant position. This corre-

sponds to a larger deviation at the implant tip and

angular deviation in MD direction. Also, the yaw devia-

tion seemed to appear in only one direction (to the left).

This could possibly be caused by both surgeons who

performed the procedure being right handed and so

always applying tension to the template in a specific

direction.

Translation in both posterior/anterior and medial/

lateral direction of the surgical template showed

statistically significant differences for implant tip and

shoulder deviations in almost all directions (BL and

MD). This can be explained by the fact that BL measure-

ment are orientated in a more posterior/anterior direc-

tion in the front region of the dental arch and more

medial/lateral in the rear regions of the dental arch. The

inverse counts for the MD direction, meaning that again

the direction of the measurement is partly perpendicu-

lar to the direction of translation.

Implant Position on the Dental Arch. In this study,

no tendency or significant differences were found for

implant position on the dental arch. Other studies17 cor-

roborate these findings and did not find a statistically

significant difference for implant position on the dental

arch. Cassetta and colleagues43 did found a significant

difference between the maxilla and mandible for the

angular deviation, but did not report a significant

difference within the arch.

The present study showed larger deviations in MD

direction as compared with the previous study executed

in non-augmented edentulous patient (Figure 4); this

might be related to the large pitch of the surgical tem-

plate. Also, the combination of using more implants

with a longer length will result in a larger tip deviation in

MD direction. Depth deviations showed to be slightly

smaller and so more accurate. In general, 95% confi-

dence intervals and maximum deviations were larger

compared with the previous study; this might be caused

by the drill shifting away at the transition of original

cortical bone to the more spongious augmented bone.

CONCLUSION

When an augmentation procedure is needed to allow

implant placement in the edentulous maxilla, computer-

aided implant planning using surgical templates showed

to be a clinically relevant tool. This study emphasizes

that the surgeon should take into account that devia-

tions are larger compared with implant placement

without augmentation procedure. Deviations are mainly

caused by angulations and translations of the surgi-

cal template. Nevertheless, computer-aided implant

planning of the augmented maxilla seems a useful

method to perform transmucosal implant placement.

Figure 4 Graphical comparison between this study and theauthors’ previous study on implant accuracy after placementof two to four implants in the fully edentulous maxilla.

8 Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014

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10 Clinical Implant Dentistry and Related Research, Volume *, Number *, 2014