fabrication of a surgical implant template with guide tubes

8/3/2019 Fabrication of a Surgical Implant Template With Guide Tubes

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Fabrication of a Surgical Implant Template With

Guide Tubes

Written by Jeremy Montrose, DDSThursday, 01 January 2004 00:00

Restorative dentists have an essential role in the diagnosis of the restorative needs of

patients treated with dental implants.1 An implant template is the means of communication

used to transfer positioning requirements to the surgeon, who can then place the implants in

positions that allow for ideal restoration of the occlusion. 2 Templates are necessary even for

single implants.3

According to Misch, the surgical template dictates to the surgeon the implant placement that

offers the best combination of (1) support for the repetitive forces of occlusion, (2)aesthetics, and (3) hygienic requirements.4 A well-designed template can reduce surgical

time, improve the accuracy of implant placement, reduce the need for expensive, vector-

changing abutments, and improve the aesthetic emergence profile of the restoration.

There are a variety of template types, ranging in sophistication and cost from inexpensive

vacuum-form shells to computerized tomography (CT)/computer-derived templates. The

following types of implant templates have been used:

Restorative implant templates indicate the shape and position of the proposed restoration(s)but do not dictate the osteotomy path for the surgeon. These are generated from diagnostic

models and generally include (1) vacuum-form duplicates of diagnostic models, (2) acrylic

resin material based on a diagnostic wax-up, or (3) direct resin adaptation to the diagnostic

model. Each of these templates cover the occlusal tables of adjacent teeth for support. The

proposed implant site is often represented in acrylic on the restorative template by the facial

surface of the desired restoration or by the intact acrylic representation of the entire

proposed restoration for the surgeon to manipulate as is appropriate.

The advantages of restorative templates are their ease of fabrication, commonly availablematerials and techniques, and low cost. The disadvantage of the restorative template is that

it does not dictate the position of the osteotomy.

Surgical implant templates may also indicate the shape of the proposed final restoration but

dictate the osteotomy as well. They are generally based on CT scan data and computer-

driven design and fabrication. In this category, a CT scan is taken of the patient's jaw. The

implant surgery is planned using CT scan, and a computer-assisted process relates the

proposed axial and depth alignment. Surgical CT-based templates are generally fabricated

by 1 of 2 processes: (1) CAD/CAM (Computer-Assisted-Design-Computer-AssistedManufacture) milling, and (2) stereo-lithography.


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The advantages of using surgical templates include predictability of placing implants in

proper alignment, avoiding injury of adjacent structures (teeth, sinuses, or cortical plates),

and reduced surgical time,5 with corresponding improvement in postoperative healing. The

disadvantages of using surgical templates are the higher start-up costs of computer software

and the learning curve associated with reading CT scans and creating the correct treatment

plan. Furthermore, dentists might hesitate to utilize surgical templates because of the added

expense and inconvenience to the patient, especially for less involved cases.

Therefore, restorative templates are quite simple, while surgical templates are more

complex. The effort the restorative dentist invests in designing and fabricating an implant

template, and the type of template selected, should reflect information that should be

transferred to the implant surgeon to assure a successful prosthetic outcome.

For implant treatment consisting of one to a few implants, dentists may be able tocommunicate the necessary information adequately with the simpler restorative template.

Nevertheless, relatively simple cases can have only a small margin of error. Each implant

and restoration has a set of challenges determined by location, hard- and soft-tissue

anatomy, spacing between adjacent teeth, and other aspects of local anatomy involving

location of neurovascular bundles, sinuses, and cortical plates of bone. Predetermining the

appropriate osteotomy path for the surgeon could greatly assist the surgical procedure.

A type of template that is seldom used but has advantages of both the restorative and

surgical templates is the surgical guide-tube template. It is fabricated as a restorativetemplate with a hard resin material that rests on the occlusal table of adjacent teeth. As

opposed to relying on a CT scan, the restorative and surgical considerations are related by

bone mapping and radiographic verification.

This article will present a technique for fabricating guide-tube templates, including

verification of accuracy and guidelines for use during implant surgery.

MATERIALS AND METHODS

Figure 1. Surgical guide-tubes

(Stent Guide Tubes, 3i Implant

Innovations Corp).


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Guide-tubes are prefabricated, stainless steel, radiopaque tubes that can be obtained from

implant manufacturers (eg, Stent Guide Tubes, 3i Implant Innovations, Figure 1). They are

manufactured with only a single internal diameter of approximately 2.3 mm, which

accommodates only the initial size osteotomy burs, and a length of 10 mm that can be

trimmed to fit the thickness of the template or to accommodate the vertical space necessary

for the surgical handpiece. The guide-tubes are embedded into acrylic models via laboratory

acrylic processing or by a direct acrylic process on models.

Implant surgery begins with the creation of a small diameter osteotomy. Guide-tubes will

dictate the path of these initial burs. After the initial osteotomy is prepared, the template is

removed from the mouth and subsequent larger diameter burs tend to follow the path initially

created. To relate the access tube properly in the buccal-palatal/lingual dimension of bone,

one additional diagnostic step (bone mapping) is necessary to predetermine the outer

dimensions of the cortical plates of the implant site.

When evaluating the patient clinically, the buccal-palatal/lingual dimension of the edentulous

site is sounded or bone-mapped to determine the depth of the soft tissue covering bone at

the implant site.6,7 Several drops of anesthetic are placed, a periodontal probe is inserted

horizontally through the soft tissue to the bone, and the depth is recorded for transfer to the

diagnostic models. This is repeated in 3-mm vertical steps on both sides of the edentulous

space, moving apically so that the approximate buccal-palatal/lingual dimensions are

determined. This helps to create a safer osteotomy by allowing the osteotomy to be aligned

within the cortices, thereby avoiding penetration of the cortical plates. If there is a substantial

amount of bone in this direction, the decision regarding where to place the guide-tube in the

buccal-palatal/lingual plane will be based on the requirements of the final restoration (type of

retention, aesthetic needs, and diameter of the implant). If there is not a substantial amount

of bone in this direction, the only option will be to center the guide-tube in the middle of the

bone. The mesial-distal position and axial angulation are later verified after the template is

processed.

The fabrication process is similar for a device to be used with a single implant or multiple

implants. For descriptive purposes, a template based on replacement of a single tooth, with

teeth on each side, will be described.

Figure 2. Guide-tube placed Figure 3. Centered guide-tube,


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into the center of the

edentulous space.

occlusal view.

Figure 4. Surgical guide-tube

template on the diagnostic

model.

Figure 5. Template in place

intraorally at the time of

radiographic verification.

In the laboratory, a guide-tube is placed onto the model with the center of the tube in the

ideal position for the specific needs of the proposed restoration and within the buccal-

palatal/lingual axial limitations of the bone as determined by bone mapping (Figures 2 and

3). At this point, the template is processed using resin with the guide-tube in place (Figures 4

and 5). For short span templates where only 1 or 2 implants will be placed with adjacent

teeth existing on both sides, a visible light-cured material (Triad TranSheet Material,

DENTSPLY/Trubyte) with the model coated to allow release of the template can be used for

direct, in-office fabrication. For longer edentulous spans, a stronger laboratory processed

dense acrylic template should be made. For either the direct in-office technique or the

laboratory processed technique the template should be made thick enough to prevent

distortion or fracture.

Figure 6. Radiographicverification indicating the

guide-tube is properly

positioned.

Figure 7. Ideal implantplacement of 4.0 x 13-mm 3i

Osseotite Certain NT implant

(3i Implant Innovations).

Verification of the correct mesial-distal angulation of the guide-tube within the template is

accomplished radiographically (Figure 6). The template is placed onto the teeth and a

bitewing radiograph is taken. A pencil line is drawn on the developed film through the center

of the guide-tube and extended apically through the projected osteotomy path. The pencil

line should be centered between adjacent clinical crowns, and as the line extends apically,

the adjacent roots should not be contacted. The desired depth of the implant along the


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pencil line should not violate the local anatomy, including neurovascular bundles or sinuses,

and should be short of those anatomical structures by a distance mutually agreed upon by

the restorative dentist and surgeon (Figures 6 and 7).

Figure 8. The osteotomypathway projected through this

guide-tube is poorly centered

between adjacent roots.

Figure 9. The corrected guide-tube position indicating the

appropriate osteotomy

pathway.

Figure 10. A Gelb

Radiographic guide pin in

place indicating an appropriate

initial osteotomy.

Figure 11. A properly

positioned 4.0 x 13-mm 3i

Osseotite external hex implant

(3i Implant Innovations Corp).

If the guide-tube does not project a safe osteotomy path, it can be modified in the same

clinical visit (Figures 8 through 11). A hemostat is used to grip the tube portion that extends

out of the template, and the tube is removed and placed aside. The hole that remains in the

template is broadened to accommodate the axial correction of the guide-tube in the mesial-

distal plane only. The guide-tube is placed into the now-corrected position, luted with acrylic

or flowable composite, and then cured. The template is again placed onto the teeth, and

another radiograph is exposed to verify that the guide-tube is correctly positioned.

The template with the corrected guide-tube is now complete. The buccal-palatal/lingual

position was determined by bone mapping, and the mesial-distal position was determined

radiographically. The verified template, the radiograph, and the bone-mapping data are sent

to the surgeon.


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Once the basic surgical guide-tube template methodology described above is mastered by

the clinician, helpful variations can be introduced.

Figure 12. A second

provisional restoration

template seated on articulated

models. The shape of the

previously unprepared teethwas preserved in this template

and assisted in the positioning

of the guide-tube.

Figure 13. An occlusal view of

the pontic site with space to

accommodate the guide-tube.

Figure 14. The guide-tube in

place with a 2.0-mm diameter

surgical twist bur in position,

demonstrating how it is

extended through the surgical

guide-tube template during

surgery.

Figure 15. Radiographic

verification of the guide-tube

indicates an improper

osteotomy pathway.

Figure 16. The second

radiograph of the corrected

guide-tube position indicates

the correct osteotomy path.

Figure 17. A well-positioned

3.25 x 15-mm Osseotite

implant (3i Implant

Innovations) in a site limited

by the curvature of the canineroot and the mesial root


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projection of tooth No. 13.

In a situation where a failed bridge must be removed, the restorative dentist can fabricate

both a provisional restoration and a surgical template at the same clinical visit if implants are

included in the treatment plan. In this situation (Figures 12 through 17), a preoperativeimpression of the area of the failed bridge is taken using a bite tray (Triple-Tray, Premier

Dental Products) with a polyether impression material (Impregum, 3M ESPE AG). After

bridge removal, caries control, and preparation of the abutment teeth, a bis-acrylic

provisional material (Protemp 3 Garant, 3M ESPE AG) is injected into this impression and

then seated on the prepared teeth. Following conventional techniques for fabricating and

finishing the first provisional bridge, a second provisional bridge is fabricated and properly

adjusted. Before the patient is dismissed, the edentulous site is bone-mapped. Alginate

impressions of the prepared teeth, the opposing arch, and a bite registration are made. The

first provisional bridge is cemented, and the patient is dismissed. The second provisional willfit the articulated models.

This second provisional bridge can be converted to a surgical guide-tube template. This

approach offers significant benefits. First, in contrast to when natural teeth are present, once

a bridge is removed, the abutment teeth provide little reference relating to the local anatomy.

However, if the shape of the previous bridge is preserved in the second provisional

restorationand if that restoration is well-seated on the articulated modelsthe radiographs

can assist the dentist in positioning the guide-tube(s).

In Figures 12 through 17, note the limiting local anatomy in the tooth No. 12 implant surgery

site, where the apical third of the canine root vectors sharply to the distal and there is a

mesial root projection associated with tooth No. 13. Preoperatively positioning and verifying

the guide-tube in this template facilitated safe and predictable implant placement and

restoration. Furthermore, the provisional surgical template technique utilizes the tooth

morphology (the pontics of the failed bridge) and may allow the clinician to bypass the dental

laboratory for diagnostic template fabrication. This will facilitate prompt scheduling of the

patient for implant surgery.

Although the surgical guide-tube template is relatively easy to fabricate, accuracy during all

phases of fabrication is essential. Any compromise in the accuracy of the measurements or

fabrication will increase the likelihood of error or abandonment of the template at the time of

surgery. Therefore, a review of potential problems and how these can be prevented is

helpful.

POTENTIAL PROBLEMS

The template must accurately fit so it can be placed on the teeth in a reproducible manner. It

should be stable and retentive, even when not held in place. A radiograph of the template


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should be taken and bone mapping accomplished as previously described. Furthermore, the

device should be polished to avoid rough surfaces that are difficult to disinfect or sterilize.

Communication between the restorative dentist and surgeon is essential. After fabrication of

the template, it should be determined in advance how to disinfect or sterilize the template.The heat of an autoclave would deform the acrylic. Patients should never manipulate the

template or have the template in their mouth unless under supervision. This reduces the

likelihood of them inadvertently deforming the template.

Figure 18. An initial 2.0-mm

diameter implant bur attached

to a latch-head handpiece

resting in a guide-tube

template on the model. The

necessary vertical space is

illustrated.

Other suggestions pertain to the surgical procedure. The guide-tube template can add

significant vertical length to what is required by the surgical handpiece and burs (Figure 18).

The surgeon should be informed of this well in advance of the surgery so that appropriate-

length burs are available. The template itself can be reduced from the occlusal surface to

reduce the interarch dimension, thereby accommodating both the handpiece and bur.

The template, even when fabricated with a rigid acrylic base, can move off the occlusal table

if the surgeon encounters dense bone. When this occurs, the osteotomy bur deflects against

the inner wall of the guide-tube. The lever-arm force generated by the relatively long

handpiece causes the entire template to be lifted off the teeth, even though the surgeon may

feel that the template is firmly in place. The same problem can be encountered when

preparing a tooth socket during immediate implant placement or even after an extraction site

has healed. The dense lamina dura of the socket wall can easily reroute the bur, creating a

torquing force against the inner walls of the guide-tube, lifting the template out of place.

This problem can be prevented. The surgeon should first create a partial-length osteotomy

that is short of the ideal length. Before exposing a radiograph with the guide pin in place, the

bur should be removed from the handpiece and reseated through the template into the

osteotomy preparation. This will allow verification of passive placement through the guide-


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tube without displacement of the template. The reason for detaching the bur from the

handpiece is to remove the lever-arm effect of the handpiece.

If the template lifts up during drilling or if at verification the bur does not seat passively

through the guide-tube, modification of the initial osteotomy toward the correct path isneeded. This should be performed without the template in place. Since osteotomy burs are

generally end-cutting instruments, a side-cutting correction bur should be used (eg, the

Lindemann Bur, Salvin Corp).

Figure 19. A denture style

surgical guide-tube template.

Figure 20. The denture style

surgical guide-tube template

facilitated the proper

positioning of these 3i

Osseotite external hex

implants. View during surgery,

before removal of the surgical

mounts.

Another use of guide-tubes is demonstrated in Figures 19 and 20. A CT scan indicated

abundant buccal-palatal bone for implant placement for a treatment plan consisting of an

acrylic/noble metal, screwed-down, fixed hybrid full arch prosthesis. The implants were to be

placed on half arch at a time to allow the remaining teeth to strategically support the existing

prosthesis. A denture tooth setup was fabricated and approved by the patient. The setup

was duplicated in clear acrylic in a denture duplicating flask (Lang Denture Duplicator, Lang

Dental Mfg Co) and re-mounted on the articulator. A surgical guide-tube template was

created. Guide-tubes were positioned for implants that are suitable for the anatomy and

future prosthesis. Figure 19 shows the surgical template after the guide-tubes were luted

with flowable composite and before polishing. Figure 20 shows the properly positioned

implants just prior to removal of the blue colored "surgical mounts." This particular brand of

implants is packaged with these devices attached to the implant. The surgical mounts enable

the sterile transfer of the implants from the package to the osteotomy sites. The surgical

mounts were subsequently removed. The healing (cover) screws were placed and the site

was sutured closed for a 4 month healing period (#I Osseotite External Hex implants, 3i

Implant Innovations Corp).


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DISCUSSION

A surgical guide-tube template allows the implant team to plan preoperatively for proper

positioning of implants and represents a prescription for the projected osteotomy to avoid

damage to adjacent roots or compromise of important anatomic structures.

There is a learning curve with this technique which will be reduced if the restorative dentist

and implant surgeon discuss the fabrication process, discuss how to avoid potential errors,

and if they understand their respective challenges in bringing the case to a satisfactory

prosthetic conclusion, since they both contribute to the successful outcome.8

This author considers the surgical guide-tube template to be a more informative

communication tool than a restorative template, but it is important to emphasize that it is not

appropriate for all cases. The use of the surgical guide-tube template should be limited toclinical situations where the majority of the implant dimension can be predetermined through

bone mapping and radiographic verification. For cases where the entire surgical path must

be preoperatively verified, a CT scan surgical template is generally needed.

The expense and time the restorative dentist chooses to invest in designing and fabricating

implant templates, and the type of template selected, should be a reflection of the amount

and type of information needed to be transferred to the implant surgeon to assure a

successful prosthetic outcome.

There is no single template technique that fulfills all the needs of the implant team. Simple

restorative templates and surgical templates all have their place in the modern dental

practice. CT scan-derived templates are very useful but are also technique sensitive, and

clinical application requires a substantial learning curve. The benefits of surgical guide-tube

templates are their low cost, readily available materials, minimal time for fabrication, and

reduced radiation exposure.

CONCLUSION

This article has described the fabrication and clinical use of the surgical guide-tube template.

The use of templates is associated with greater precision in implant rehabilitation. A simple

referral to the implant surgeon without advanced planning and involvement of the restorative

dentist can greatly reduce the effectiveness of implant therapy.

Acknowledgment

The author would like to thank Mr. Wayne Szara of 3i Implant Innovations for his dedicated

effort in diligently and accurately responding to implant inquiries. He can be reached at (800)

342-5454. And William "Coach" Bartosiak of North American Dental Laboratory is


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responsible for all restorations placed by the author and is a wellspring of knowledge in

implant dentistry. He can be reached at his office at (847) 982-9788.

References

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implants. J Prosthet Dent. 2001;85:26-29.

2. El Askary, Abd El Salam. Reconstructive Aesthetic Implant Surgery. Ames, Iowa:

Blackwell Munksgaard; 2003:2:33-34.

3. Cranin AN. Root form implant prosthodontics: Single tooth implant restorations. In: Cranin

AN, Klein M, Simons M, Simons A, eds.Atlas of Oral Implantology., 2nd ed. St. Louis, MO:

CV Mosby; 1999:58-67.

4. Misch, CE, Dietsch-Misch, F.; Diagnostic casts, preimplant prosthodontics and surgical

templates. In: Misch, CE.: Contemporary Implant Dentistry., 2nd ed. St. Louis, MO: CV

Mosby; 1999:58-67.

5. Benjamin, LS. The evolution of multiplanar diagnostic imaging: predictable transfer of

preoperative analysis to the surgical site. J Oral Implantol., 2002;Vol. 285( No.3):135-144.,

2002

6. Flanagan DF. A method for estimating preoperative bone volume for implant surgery. J

Oral Implantol. 2000;26:262-266.

7. Wilson DEJ. Ridge mapping for determination of alveolar ridge width,. Int J Oral Maxillofac

Implants. 1989;4:41-43, 1989.

8. Small, BW. Surgical templates for function and esthetics in dental implants. Gen Dent.,

2001 Jan-Feb;49(1):30-32,34.

fabrication of a surgical implant template with guide tubes

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