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CAST-BASED GUIDED IMPLANT PLACEMENT: A NOVEL TECHNIQUE

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com


SURGICAL GUIDEGPT 8: a guide used to assist in proper

surgical placement and angulation of dental implants.

DESIGNS: Nonlimiting, Partially limiting, Completely limiting


• Designs of surgical guides:

Nonlimiting design provides the surgeon an indication as to where the proposed prosthesis is in

relation to the selected implant site. Partially limiting design offers the

possibility to have a guide sleeve direct the first drill used for the osteotomy.

The remainder of the osteotomy and implant placement is then finished freehand by the surgeon.


The completely limiting design restricts all of the instruments used for the osteotomy in a buccolingual and mesiodistal plane.

The addition of drill stops limits the depth of the preparation and, thus, the positioning of the prosthetic

table of the implant. As the surgical guides become more restrictive,

the ease and precision of implant placement is enhanced.

Information acquired in the preoperative planning phase is

transferred to the surgical guide.


If a completely restrictive guide is relied upon during implant placement, the surgeon must ensure that the clinical data has been accurately transferred to the surgical guide.

Guides that are not completely restrictive require interoperative radiographs to confirm the mesiodistal trajectory; the initial twist drill.

Since, with guides that are not completely restrictive, the exact position of the implant is not known before surgery, the prefabrication of a provisional restoration might be less precise compared to a provisional restoration developed following the fabrication of the completely restrictive guide.


Bone sounding has been used in clinical dentistry to acquire an understanding of the thickness of the soft tissue overlying the bone.

By subtracting the thickness of the soft tissues from the total width of the alveolar ridge, an estimation can be made of the bone volume at the measured sites.

Within this volume of bone, the correct position of the dental implant can be established.


When determining the position of a dental implant, 3 axes must considered separately.

The x-axis is clinically the mesiodistal plane,

the y-axis represents the buccolingual plane, and

the z-axis determines the length at the apex of the implant

and the depth of the prosthetic table at the top of the implant.


When considering the position of the implant in the mesiodistal plane, the proximity to the adjacent teeth is the greatest limiting determinant, followed by the requirements of the prosthetic reconstruction.

In the buccolingual direction, available bone volume, again in combination with the prosthesis, will guide the desired implant location.

Considering the final axis, the position of the top of the implant is based on clinical parameters and desires, while the length of the implant is generally set by the proximity to anatomic structures or body cavities.


This article demonstrates a combination of analog techniques to produce a surgical guide, allowing placement of a dental implant in a precise predetermined position.

The surgical guide is then used, following established guided surgery protocols, to place a dental implant.

The surgery is a flapless procedure, improving patient comfort.

Since the implant position relative to the surrounding dentition is known, a provisional restoration and, if desired, the definitive abutment, can be prefabricated, so that it can be inserted at the time of surgery if an immediate provisional restoration is desired.


TECHNIQUEData acquisition:1. Select a stock impression tray2. Palpate the area of the proposed implant site and

determine if there are areas susceptible for soft tissue deformation.

3. Apply a utility wax strip to the tray, to create positive pressure on the easily deformed areas.

4. Use irreversible hydrocolloid to make the impression.5. Use a pinless tray and die system to section the cast,

and reposition the sections in the correct spatial relationship.

6. Create a cast by casting the impression with, low-viscosity, casting vinyl polysiloxane (VPS), while casting the base with a medium-viscosity VPS material.


• 7. Remove the impression from the cast once the material has polymerized.

8. Make a partial overimpression over the soft tissue area and adjacent teeth of the proposed implant site with a stiff VPS material.

9. Fit a sterile (27 G) dental needle with an endodontic rubber stop at the apex of the needle.

Crestal penetration of measuring needle


10. Anesthetize the patient as needed. Make the first measurement at the crest of the edentulous ridge.

11. Remove the needle from the measured site and record the distance between the apex of the needle and the rubber stop, as the thickness of the soft tissue at the crest.

12. Make the second measurement on the buccal surface at the most apical part of the proposed implant site which is still accessible.

13. Make the third measurement in a similar position on the lingual surface, while measurements 4 & 5 are made in between the crest and most apical portion.


Transfer of clinical data to the cast14. Make a periapical radiograph of the proposed

site in such a way that foreshortening or elongation is prevented and the image is dimensionally true, while capturing the apices of the adjacent teeth as much as possible.

15. Adjust the digital image using an image manipulation program to create a true1:1 image.

17. On the modified radiograph, use scissors to cut out the bone between the root structures and the occlusal surface of the teeth.

18. Place the modified radiograph on the cast, to coincide with the occlusal and interproximal surfaces onthe cast.


19. Outline the position of the root structures on the cast with a pen. Mark the area available for implant placement in the mesiodistal direction.

20. Mark the best position for the midline of the proposed implant.

21. Remove the cast from the Accu-Trac.

22. Cut the cast exactly in the selected plane with a large 45-mm diamond-coated disk.

Transposition of root structure onto cast

Cast sectioned at proposed axis of implant


23. Select 1 portion of the sectioned cast to transfer the clinical tissue depth measurements.

24. Mark the depths on the cast in positions similar to those from which they were acquired clinically.

25. Connect the marking points, and mark with red ink the tissue surface above the line. Visualize the underlying area of the available bone volume in the buccolingual plane.

26. Select the implant diameter based on the availability of bone in both the mesiodistal and buccolingual planes.

27. Determine the axis for the buccolingual plane, guided by the availability of bone and the prosthetic reconstruction.

28. Mark the axis on the cast. Transfer the position of the axis onto the gingival crest, as this will later indicate the starting point for the cast osteotomy.


29. Mark the depth of the implant platform with a horizontal line perpendicular to the implant axis. Follow the parameters as determined by the available bone and the emergence profile of the prosthetic crown; most often this will range from 2 to 3 mm from the proposed buccal marginal gingival border.

30. Place the marked cast piece back into the Accu-Trac tray and place both onto a survey table. Orient the cast to the previously identified path of insertion.

31. Place a drill bit, the size of the selected implant diameter, in the chuck of a drill press.

32. Lower the press, to place the drill at the height of the cast on the surveyor table.


33. Unlock the table, and place the sectioned part of the cast against the drill to transfer the mesiodistal plane• 34. Rotate the table to coincide

with the marking of the buccolingual axis, while taking care to not change the previously established mesiodistal plane.

35. Lock the surveyor table, and confirm both planes to be parallel with the drill bit.

36. Remove the Accu-Trac tray from the surveyor table, and reposition the remaining section of the cast in the tray. Close the hinges of the tray so the sections again relate to each other as before sectioning.

Orientation of drill bit for mesiodistal plane.

Orientation of drill bit for buccolingual plane.


37. Place the Accu-Trac tray back onto the surveyor table, then move the cast under the drill bit. Lower the drill on the marking on the crest, indicating the buccolingual axis.

38. Make the cast osteotomy at a depth slightly deeper than the length of the implant laboratory analog.

39. Remove the Accu-Trac tray from the surveyor table, open and remove 1 section of the cast. Visually inspect the buccolingual cast osteotomy as made and reaffirm that it is correct before proceeding.

40. Position a laboratory implant analog in the section of the cast osteotomy, with the platform at the previously selected depth. Secure with cyanoacrylate glue.

Occlusal view of completed cast osteotomy.

Laboratory analog at selected platform depth.


41. Coat the contralateral part of the cast osteotomy with cyanoacrylate glue, mate the cast sections in the Accu-Trac tray, and close the tray.

42. Remove the area above the analog and between the adjacent teeth with a scalpel to start the creation of simulated gingival tissue.

43. Place a 2-mm healing cap onto the analog.

44. Perforate the previously made, preoperative, stiff VPS impression at opposing sites and reposition the preoperative impression on the cast.

45. Inject a heavy-body polyether impression material. Once the material has polymerized, cut the soft tissue mask to simulate the desired emergence profile.

Platform placed 2 mm below proposed buccal free gingival margin.


Transfer of the cast information to the surgical guide

46. Select a guide sleeve consistent with the selected implant width. Weld 2 sections, 10 cm by 0.5 mm, of metal wire to the lateral sides of the sleeve.

47. Assemble a laboratory guide pin onto the laboratory analog in the cast.

48. Bend the wires to create a framework around the teeth.

49. Place a 2-cm section of polyethylene tubing over the top of the laboratory guided cylinder pin to prevent overflow of the VPS material over the top of the guide sleeve.

Modified sleeve positioned on laboratory pin.

Wires bent to create supporting framework.


50. Isolate the cast with a spray of separator, as both materials are VPS and otherwise will bind together.

51. Perforate a small disposable plastic impression tray so that it will fit over the tubing.

52. Inject a stiff VPS occlusal record registration material, surrounding the teeth and the guided cylinder. Place the plastic impression tray over the tubing and VPS.

53. Upon the completion of polymerization, unscrew and disassemble the guided laboratory pin.

54. Remove the buccal and lingual walls next to the guide sleeve to create access for the clinical surgical instrumentation.

Application of stiff VPS.

Completed surgical guide; note relationship withlaboratory analog and future implant platform.


55. Place the completed surgical guide intraorally and make a periapical radiograph parallel to the occlusal portion of the sleeve.

56. Extend the lateral borders of the sleeve on the radiograph and confirm the correctness of the mesiodistal trajectory.

57. Fabricate the provisional restoration or definitive abutment-provisional restoration combination, since the exact position of the implant is known before the surgery. Mark the position of the orientation lobe of the analog to the surgical guide.

Radiograph to confirm correctness of mesiodistal trajectory.

Provisional restoration premade on cast previously used for surgical guide fabrication.


Implant placement surgery58. Prepare and anesthetize

the patient as needed.59. Place the surgical guide

and introduce the tissue punching drill with water irrigation through the sleeve. Puncture the soft tissue and create a starting point for the osteotomy.

60. Place a 2-mm drill guide in the sleeve, to allow precise guidance of the 2-mm drill.

61. Place a drill stop on the 2-mm and subsequent drills at the implant length plus 10 mm, per the system requirements.

Tissue perforation start drill guided through surgical guide.

Twist drill with limiting depth stop, guided through surgical guide.


62. Gradually enlarge the osteotomy, depending on the diameter and the resistance of the bone, to the appropriate size. Guide each drill by the corresponding drill guide.

63. Place the implant on the guided implant mount, and introduce it through the guide into the osteotomy. Ensure that the implant mating surface is in the same orientation intraorally as on the cast, so that the abutment or screw provisional will be correctly orientated.

Relationship of dental implant to surgical guide and, thus, intraoral situation.

Hand torquing of implant; note position of internal lobe markings.


64. Remove the implant mount and use a tissue punch to clean soft tissue tags that might interfere with the seating of the prosthetic components.

65. Place the screw-retained provisional restoration or abutment/provisional restoration combination if sufficient initial stability (35 N/cm) is obtained, as indicated by the insertion torque device.

66. Ensure that the provisional restoration does not have interproximal and occlusal contact, as to limit excess motion during the osseointegration healing period.

Postoperative radiograph.

Provisional restoration in place. Note lack of occlusal and interproximal contacts.


DISCUSSIONConventional impressions are cast in a dental stone.

While this is a viable technique, this article proposes the use of a stiff VPS.

The material allows for the creation of a cast with acceptable accuracy, in an expedient manner.

In addition, the properties of the VPS material allow for easy handling during the remainder of the process.

Since the cast must be transversely cut, a system to reposition the cast pieces back into the correct relationship is used.

Traditionally, pin systems are used for sectioned casts, but if the cast is fabricated in the dental office, a pinless system, like that described, may facilitate the process.


SUMMARYCast-based guided implant surgery allows for

the precise placement of dental implants with the possibility to continue with an immediate load protocol.

The fast flapless procedure allows for minimal patient discomfort, while attaining a high level of precision.

This article describes the unique use of VPS material for the fabrication of the cast and the surgical guide.


Thank you

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jcccc1 / orthodontic courses by indian dental academy

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