S - Technique

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CLINICAL APPLICATION

328HE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY

OLUME 6 NUMBER 3 AUTUMN 2011

A Simple Way to Plan Implant

Positioning: The S-Technique

Sergio Piano, DDS

EAED Affiliate

Private Practice, Genoa, Italy

Correspondence to: Dr Sergio Piano

Viale Brigata Bisagno 4, 16129 Genoa, Italy

tel: +39-010-592578; e-mail: [email protected]


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3THE EUROPEAN JOURNAL OF ESTHETIC DENTI

VOLUME 6 NUMBER 3 AUTUMN

Abstract

This study presents a technique for im-

proving implant placements. As is wide-ly known, a correct positioning is essen-

tial in restoration-driven implants, as well

as in tilted implants in order to obtain

satisfactory final functional and esthetic

results.

To this end, some authors have em-

phasized the importance of using a di-

agnostic and/or surgical guide to plan

the exact implant position.

In practice, one of the clinical prob-

lems faced is how to check the accur-

acy of the template prior to initiating the

surgical phase. A simple method called

the S-Technique is proposed in order

to evaluate and to change, if necessary,the projected position of the implants

by way of metal rods as radiopaque

markers. This device is easy to produce

and is cost-saving to the clinician and,

therefore, to the patient. Furthermore, in

specific patients, this method could al-

so decrease the need for computerized

tomography scans and/or radiographs,

thus reducing health risks for the patient.

(Eur J Esthet Dent 2011;6:328341)




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Introduction

Implantology has made great advances

in the last few years, both in regard toesthetics and reliability. An essential

prerequisite of effective therapy is the

establishment of an accurate diagnosis

and precise planning.1,2 Nevertheless,

it is equally important to apply all the in-

formation collected during the project

phase to the actual treatment in the pa-

tients mouth.

To this end, a diagnostic wax-up is

usually used to make a diagnostic or

surgical template to plan or to check the

exact implant position in line with the ini-

tial treatment plan.3,4

With the correct implant position, sev-

eral goals can be reached. That is, to

simplify the treatment, reduce the trauma

and guarantee the patients comfort

whilst obtaining satisfactory final func-

tional and esthetic results.5

On a more specific level, a precise

positioning is often required to either ob-

tain a correct final rehabilitation by way

of an axial position of the implants (resto-

ration-driven implants)6 or to avoid ana-

tomical structures such as the maxillary

sinus, the alveolar nerve, or adjacent

teeth by way of a non-axial positioning

of the implants (tilted implants).7

Both of these above concepts are

well supported in dental literature. As

suggested by recent research, bone

re-absorption seems to have the sameincidence rate around straight or tilted

implants8 and prosthetic complications

do not appear to be increased by the an-

gling of the implant.9 Thus, the clinicians

choice of implant positioning should be

based on the specific situation of the

patient. A well-executed surgical guide

can successfully improve the way of in-

serting both axial and tilted implants.

A predictable procedure to obtain a

reliable template is to perform a compu-terized tomography (CT) scan exam with

a diagnostic stent in place. This method

allows the clinician to obtain precise 3-D

information on the correct positioning

of the implants. This approach is also

frequently used in certain patients, but

it must be considered that the level of

x-ray radiation is never negligible and,

therefore, could result in increased

health risks to the patient.

As a consequence, when anatomical

conditions are favorable (i.e. well-repre-

sented horizontal ridge width or regular

arch shape), it could be beneficial to

make a surgical stent without submitting

the patient to a high level of radiation.

From a practical point of view, in these

above-mentioned methods, often the

problem is how to verify the accuracy of

the template prior to starting the surgi-

cal intervention,10 when a CT scan is not

performed. For this task, the following

simple method called the S-Technique

can be used in order to evaluate and to

change, if necessary, the projected pos-

ition of the implants in order to obtain a

simplified surgical phase and high qual-

ity results.

Technique

Reproducing the diagnostic wax-up, an

acrylic resin template, with the shape of

the teeth to be replaced, is created. The

purpose is to produce a binding guide

only on the mesiodistal inclination (in

line with conventional two-dimensional

radiographs), allowing the clinician to


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use his expertise to vary the axis in the

buccolingual or buccopalatal direction

(not seen in intraoral radiographs). To

this aim, the half-buccal part of the resinteeth is removed (Fig 1). It is then possi-

ble to evaluate the mesiodistal direction

of the implant preparation by applying

metal rods (Fig 2) as radiopaque mark-

ers, with pieces of soft wax in a groove

chosen by the dental technician if the

implant axis is quite clear, or directly on

the buccal surface of the half-resin tooth

if the implant direction is difficult to esti-

mate (Fig 3). With the simple guidance

of an intraoral radiograph, this template

permits us to verify the exactness of the

mesiodistal direction of the preparation

(Fig 4) and allows for an easy evaluation

of the accuracy of the guide in relation

to adjacent structures. If the proposed

axis is not satisfactory, the metal rods

can be simply rotated and fixed again,

repeating the intraoral radiograph until

the correct position is obtained (Fig 5).

The fact that these metal rods can be ro-

tated around their axes in an S shape

has given the technique its name.

The concluding step is the refinement

of the guide by the dental lab based on

the clinicians final instructions (Fig 6).

Using this method, a correct position-

ing can be obtained (Figs 7 and 8) with-

out any contact whatsoever between the

implants and anatomical structures or

adjacent teeth. The stent exactly deter-

mines the position of the implant shoulderand suggests a guided, but not strictly

limiting, execution of the first cutting dur-

ing the surgical phase,11,12 as well as

allowing the clinician to possibly modify

the buccolingual or buccopalatal axis.13

The same approach can be taken

into account when, in a fully edentulous

Fig 1 The stent is produced by cutting the half-

buccal part of resin tooth; a groove is created only

where the implant axis is reasonably clear.

Fig 2 Metal rods used for checking the accuracy

of template as radiopaque markers.

Fig 3 By means of pieces of soft wax, the metal

rods are fixed on the stent, indicating the chosen

orientation.


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Fig 4 Radiograph with the surgical guide in pos-

ition: the metal rods show that the implant axes are

not ideal.

Fig 5 With the rotation of the markers, the correct

direction on the resulting radiograph is obtained.

Fig 6 The final axis position is marked by the den-

tal technician on the template.

Fig 7 The implants are positioned following the

indication of the guide.

Fig 8 The post-surgical radiograph (executed

with the template in position, provided with the metal

rods) confirm the exactness of the guide and the

consequent precision of implant positioning.

Fig 9 A U-shaped guide can be used for fully-

edentulous patients. Also in this patient, the applica-

tion of metal rods allows the determining of the right

axis of the implants related to anatomical obstacles.


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Figs 10 and 11 First patient study: initial situation with radiograph showing the presence of the maxillary

sinus as an anatomical obstacle to the positioning of the distal implant.

patient, the implants must be placed

closely to the maxillary sinuses in a

distally-tilted position. In this situation,

a U-shaped resin mold (Fig 9) is usedas a surgical guide; on the buccal side,

the metal rod is placed in the same way

as in the previous situation and a re-

sulting radiograph is used to check the

exactness of the implant axis in relation

to the maxillary sinus. If the orientation

is not correct, it is possible to move or

rotate the pin until the right position is

found. At this point, with the information

gathered, the technician is able to trans-

form the resin mold into the final surgical

template.

Clinical applications

considering two patient

studies

The first patient study is that of a female

subject who had compromised posterior

teeth in the left side of the maxilla (Figs 10

and 11) requiring implant replacements

in an area where the presence of the

maxillary sinus is an anatomical obs-

tacle. In order to avoid a complex surgi-

cal approach involving sinus elevation,a tilted implant was placed immediately

mesial to the anterior wall of the sinus.

To determine the correct position of the

implants, a stent was made and, using

a metal rod as shown above (Fig 12),

the axis of the distal implant was veri-

fied by means of a radiograph (Fig 13).

With this technique, it is easy to modify

an incorrect direction simply by rotating

the metal rod until the exact position is

obtained (Fig 14).

The resulting data allows the clinician

to define the appropriate implant axis

on the guide. In line with this device,

the surgical phase is thus performed

(Fig 15) and the implants placed in the

correct position.

The use of an angulated abutment on

the distal implant leads to the re-align-

ment of the prosthetic axis, and contrib-

utes to obtaining a final satisfactory re-

sult (Figs 16 to 19).


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Fig 14 Second attempt resulting in correctly an-

gled rod position.

Figs 16 and 17 Correctly angled abutments provide the right prosthetic position for the final fixed partial

denture.

Fig 15 Extraction of compromised tooth and in-

sertion of the two implants in line with the selected

axis position.

Fig 12 The guide with the applied metal rod as

seen on the model.

Fig 13 First attempt to find the correct position-

ing: the projected rod required further angling in

order to avoid the maxillary sinus.


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Fig 20 Second patient study: initial situation of

patients mouth, which is severely compromised.

Figs 21 and 22 A U-shaped guide is produced, and a position on which to attach the rod is selected.

A similar approach is considered in

the second patient study. In the maxilla

of a male patient (Fig 20) the remain-

ing roots were to be extracted and the

edentulous maxilla treated with fixed

rehabilitation. For the final prosthesis, a

Toronto fixed partial denture supported

by a reduced number of implants was

chosen; and, once again, it was neces-

sary to correctly tilt the implants so as

not to have contact with the sinuses, and

to avoid the use of cantilevers.

Figs 18 and 19 Final clinical and radiographical result.


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Fig 24 The pin is rotated: with the second radio-

graph, the appropriate angle is chosen in order to

avoid the maxillary sinus.

Fig 25 The same procedure is performed on the

opposite side until the right axis is obtained.

Fig 23 First attempt to determine the correct pos-

ition: it is necessary to rotate the pin.

Fig 26 Based on this information, the final guide

is produced and the technician is able to define the

groove for guiding implant placement.

A U-shaped resin base was produced

by the lab (Fig 21) and put in the patients

mouth after having positioned the metal

rods for the purpose of determining the

correct direction of cutting (Fig 22). Asseen above, the procedure was per-

formed by checking the ideal position

by means of taking a radiograph. In this

particular patient, the metal rod was

rotated and the correct axis checked

again (Figs 23 and 24). This same ap-

proach was carried out on the other side

(Fig 25) and the resulting data transmit-

ted to the Lab in order to refine the surgi-

cal guide (Fig 26).

Through the us of this guide, the im-

plants were placed correctly (Figs 27 to29) and could be immediately loaded

with a provisional screwed prosthe-

sis (Figs 30 and 31). The radiographic

images (Fig 32) show that the implants

were precisely tilted in order to avoid

any contact with the maxillary sinuses.


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Fig 28

Fig 29

Figs 27 to 29 In line with the guide, the implants

are placed in the right position.

Discussion

Precise planning is important for the

desired and correct positioning of im-plants.14 However, there are many clin-

ical situations where more than the usual

careful planning is required in order to

obtain satisfactory results, and it is in

these situations where the guide be-

comes crucial. For example, Belser et

al15 reported that, for the correct treat-

ment of esthetic situations, a carefully

executed surgical guide is mandatory.

Likewise, Leblebicioglu et al16 state that,

when a considerable number of implants

are to be inserted, the implant surgeon

should use a template, accurately work-

ing out each precise step involved. Fur-

thermore, Sclar17 and Oh et al18 rec-

ommend a well-tailored surgical guide,

fabricated with the aid of a radiographic

stent, as a key element in the success of

the flapless implant surgery technique.

Morand and Irinakis19 also underline the

importance of a well-projected template

for the correct insertion of the implants,

providing a rationale for the use of short

implants. Finally, when tilted implants

have to be positioned, Fortin et al20 pro-

pose the fabrication of a surgical tem-

plate to transfer the planned positions

to the bone with high accuracy in order

to avoid any contact with structures that

must remain untouched.

Moreover, the importance of the sur-

gical guide comes into play again incertain scenarios where, due to the

complexity of the local anatomy, surgi-

cal procedures are rendered even more

demanding. As described by van den

Bergh et al,21 sinus floor elevation is fre-

quently performed to solve the problem

of inadequate bone height in the lateral


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Figs 30 and 31 Immediate loading prosthesis after a few weeks of healing: easy access for oral hygiene

is highlighted.


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part of the maxilla, and, as critically ana-

lyzed by Chiapasco et al,22 several aug-

mentation procedures for the rehabilita-

tion of deficient edentulous ridges with

implants are often utilized.

These techniques are not always well

accepted by the patients due to the re-

sulting discomfort that is often experi-

enced. In addition, surgical complica-

tions following implant placements, such

as neuro-sensory disturbances, injuries

to adjacent teeth, penetration into the

maxillary sinus, or tissue emphysema,

can arise, especially with an increase in

the complexity of the surgery.23

For these reasons, when the anatom-

ical obstacles render the implant pos-

itioning difficult or complicated, one of

the treatment options could be to sim-

plify the surgical approach with a stra-

tegic positioning of the implants in theremaining bone regions by means of an

extremely accurate surgical template.

In an attempt to alleviate these implant

positioning difficulties, numerous types

of radiological, surgical, and combined

templates have been proposed. The

most accurate of these methods is the

use of an image-based surgical guide

and a 3-D computer-assisted planning

of oral implant surgery.24 However,

since this kind of approach implies a

high radiation dose, the added clinical

value provided by the images need to

outweigh the negative resulting health

risks. In fact, sometimes wrongly, even

less demanding cases are planned with

a CT-guided stent without considering

the importance of the increased radi-

ation exposure. Therefore, the choice of

planning technique should be carefully

evaluated in order to take into account

the pros and cons of each method.24

Concerning this, it is interesting to

underline the conclusion of the recent

systematic review by Jung et al25 on

computer technology applications in

surgical implant dentistry: There is not

yet evidence to suggest that computer-assisted surgery is superior to conven-

tional procedures in terms of safety,

outcomes, morbidity, or efficiency.

Moreover, in a review by BouSerhal et

al,26 regarding the image technique se-

lection for the preoperative planning, it

was stated that many clinical situations

Fig 32 The final radiographs confirming the accuracy of the positioning.


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demand the use of cross-sectional im-

aging techniques, but they are not re-

quired in patients in which the clinical

examination reveals sufficient bonewidth and where radiographic exami-

nations show adequate bone height.

Also guidelines introduced by EAO27

to avoid any over-use of radiographic

methods focused on the importance of

cross-sectional imaging while the use of

2-D imaging in minor and/or established

low-risk surgery should be left to the dis-

cretion of the clinician.

In these situations, one of the most

important aspects is to check the ac-

curacy of the stent produced by the

dental lab. Garber28 described the cor-

rect planning for implant placement as

a sequence of evaluations that, in the

last step, finishes with the insertion of

the implant in a predetermined pos-

ition using an appropriate template. It

is obvious that the last step determines

the success of all prior planning steps.

Controlling the accuracy of the device

(ie, with radiographs) becomes the final

and fundamental phase for achieving

the correct implant positioning.

In fact, a guide can only be appreci-

ated as a valuable tool if it is customized

to the specific anatomy of the patients

mouth and not only to the ideal position

of the teeth.29 A surgical guide that is

not well planned or tested may repre-

sent more of a limitation than an aid to

the implant treatment. When a guide ischosen, the possibility to check the ac-

curacy of the template prior to surgery

plays an important role in avoiding un-

foreseen complications or unsuccessful

results. Nevertheless, reducing the ra-

diation dose to the patient is an import-

ant aspect to take into account when apreoperative planning approach is se-

lected.

Conclusions

Concerning esthetic implant dentistry,

in the single-gap treatment as well as in

full-arch cases with multiple implants,

the precise positioning and angling of

implants is fundamental to achieving

the desired prosthetic result. Among

the different types of guide utilized for

this purpose, it is important to choose

a template that is easy to use and pro-

duce and one that allows the evaluation

of its accuracy prior to surgical interven-

tion. A simple, but accurate methodol-

ogy, such as the S-Technique, is key

to achieving these goals, as outlined

above.

It should also be noted that this ap-

proach is also cost-saving to the clin-

ician (and therefore to the patient) by

reducing the amount of the technicians

work involved and the clinicians chair-

time. Moreover, this method could de-

crease the necessity of CT scans and/or

radiographs while reducing health risks

for the patient.30

The S-Technique has been used for

several years in surgery with more thansatisfactory results, enhancing planning

procedures and simplifying surgical

phases.


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S - Technique