In Vitro Accuracy of a New Geometric Approach to Guided Surgery INTRODUCTION Implant surgical guides use cone beam computed tomography (CBCT) to increase the accuracy of implant placement & reduce errors involved with angulation & position of the implants. Disadvantages of these guides may be additional costs, fabrication time & accuracy. An alternative model-based technique is proposed that enables “in-house” fabrication of a diagnostic guide. Using information from CBCT images the angle & linear position of the guide sleeves are evaluated, corrected & the guide is refabricated. Phillips, Stephen ; Carneiro, Leandro; Meitner, Sean OBJECTIVE To evaluate the accuracy of the corrections & fabrication of surgical guides using a geometric approach in an In Vitro model with Invivo5 software. Annual Meeting · March 15-18 2017 · Orlando, Florida
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In Vitro Accuracy of a New Geometric Approach to Guided Surgery
INTRODUCTION
Implant surgical guides use cone beam computed tomography (CBCT) to increase the accuracy of implant placement & reduce errors involved with angulation & position of the implants.
Disadvantages of these guides may be additional costs, fabrication time & accuracy.
An alternative model-based technique is proposed that enables “in-house” fabrication of a diagnostic guide. Using information from CBCT images the angle & linear position of the guide sleeves are evaluated, corrected & the guide is refabricated.
Phillips, Stephen; Carneiro, Leandro; Meitner, Sean
OBJECTIVE
To evaluate the accuracy of the corrections & fabrication of surgical guides using a geometric approach in an In Vitro model with Invivo5 software.
Annual Meeting · March 15-18 2017 · Orlando, Florida
Verification Jigs (V Jigs) were made by connecting the 3 mm guide sleeves with light cured resin. All metal guide posts were removed prior to cone beam X-ray evaluation of the arch forms to minimize scatter.
Four identical arch forms were milled from acrylic blocks on a CNC Lathe, each with 12 root form sites 1/4” or 3/8” diameter for a total of 48.
3 X 30 mm metal guide posts were inserted into the holes in the PEEK root form inserts. 6 additional parallel holes were milled in the arch forms & 3 mm radiolucent Delrin® posts were placed medial to the test sites.
The V Jigs remained on the 6 parallel Delrin posts & CBCT images were taken, to determine the initial angles of the guide sleeves & virtual implants in 3 planes.
3 mm i.d. cylindrical metal guide sleeves were placed on the 18 guide posts in each arch form.
Root form inserts were made from Poly ethyl ethyl ketone (PEEK) on a CNC Lathe.
3/32” holes were milled in the inserts at arbitrary angles from 2° to 32° to the long axis of the inserts.
Sites were divided into 2 groups: 22 sites 0º - 11° & 26 sites 11º - 32º.
Inserts were secured in the arch forms with lock washers & screws.
MATERIALS and METHODS
MATERIALS and METHODS
Invivo5 Images of a 3 mm virtual implant aligned with guide sleeves.
Linear Corrections made using offset guide posts.
New guide sleeves were placed over the corrected guide posts.
axial cross sectionaltangential
▪ EVALUATE IN THREE PLANES ▪
Angle Corrections made in 2 planes using a bending tool calibrated in degrees.
▪ RE-FABRICATE ▪
New V Jigs were made connecting the new guide sleeves in each arch form for 2nd
cone-beam X-ray.
A 2 mm offset guide post corrected 29° distal & 7° buccal.
The accuracy of the angle & linear correction of the guide sleeves in the new V Jigs were determined with Invivo5 software.
Group 1: 0° - 11° - MEAN: 0.35 mm SD: 0.22 mm RANGE: 0.1 – 0.71 mm
Group 2: 11° - 32° - MEAN: 0.59 mm SD: 0.37 mm RANGE: 0.0 – 1.51 mm
Group 1: 0° - 11° - MEAN: 0.43 mm SD: 0.34 mm RANGE: 0.2 – 1.60 mm
Group 2: 11° - 32° - MEAN: 0.58 mm SD: 0.40 mm RANGE: 0.2 – 1.86 mm
ALL 48 SITES - MEAN ANGLE ERROR: 1.19° SD: 1.04° RANGE: 0.02° - 5.83°.
Angle measurements were made from the long axis of the guide sleeve & virtual implant to a vertical plane. (90° to the horizontal surface of the arch form base)
Initial Angle from Vertical
Entry Point Linear Error
Apical Linear Error
In the PROCEEDINGS OF THE FIFTH ITI CONSENSUS CONFERENCE, the Tahmaseb et al article, Computer Technology Applications in Surgical Implant Dentistry: Int J Oral Maxillofacial Implants 2014,29 Supplement. 25-42. A Systematic Review included 24 accuracy studies, 1530 sites. A meta regression analyses was performed to summarize the accuracy of static implant guided surgery studies. A summary of the results of the accuracy studies revealed a mean angular deviations from 1.49° - 8.54° with a maximum of 21° compared to 1.19° with a maximum of 5.83°. The mean linear error at the entry point of the studies varied 0.15 mm - 1.7 mm with a maximum deviation of 4.5 mm compared to 0.59 mm with a maximum of 1.51 mm in this study.The mean linear error at the apex varied from 0.28 mm - 2.99 mm with a maximum deviation of 7.1 mm
compared to 0.58 mm with a maximum of 1.86 mm in this study.
DISCUSSION & CONCLUSION
The In Vitro Accuracy of a New Geometric Approach described in this study suggests a greater degree of accuracy may be attainable to the accuracy previously reported in other In Vitro studies or In Vivo studies of computer generated static surgical guides.
However, guided osteotomy preparation is only an indication of the planned implant position and not necessarily an indication of the actual implant placement because implants still can be inserted in deviant positions to the long axis of the osteotomy. The use of multiple guide sleeves and guided implant placement are important steps in increasing the accuracy.
