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The Effects of Scan Pattern on the Trueness and Precision of Six Intraoral Impression Systems

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Title: The Effects of Scan Pattern on the Trueness and Precision of Six Intraoral Impression Systems

 

Author(s): Todd Cleary and Ravi Patel

 

Mentor: Dr. Wally Renné

 

Objective:  To evaluate the effect scan pattern has on the trueness and precision of six intraoral digital impression systems 

 

Background:  Companies who make digital impression systems often recommend a scan pattern specific for their system.  Every clinical scanning scenario is different and may require a different approach.  The aim of this project was to determine how scan pattern affects accuracy.

 

Methods:   Six digital impression systems were evaluated:  CEREC Omnicam (CO), Planmeca Emerald (PE), Planscan (PS), TRIOS 3 (3S), Itero Element (IE), and True Definition (TD).  A custom model was created by Dr. Renné and a master digital model was then fabricated.  Experimental scans were taken with each of the six digital impression systems of each of the scan patterns.  The scan patterns were selected based on the recommendations of the manufacturers of each digital impression system.  Scan pattern one (SP1) began at the maxillary second molar and scanned the occlusal surfaces of the sextant, followed by the buccal surfaces from anterior to posterior and concluded with the lingual surfaces from posterior to anterior.  Scan pattern two (SP2) began at the cuspid and scanned the lingual surfaces first, followed by the occlusal surfaces from posterior to anterior and concluded with the buccal surfaces from anterior to posterior.  Scan pattern three (SP3) began at the cuspid and scanned the occlusal surfaces first from anterior to posterior and then concluded by alternately rolling from buccal to lingual to buccal from posterior to anterior.  Scan pattern four (SP4) began at the second molar and scanned the buccal surfaces first from posterior to anterior, then the occlusal surfaces from posterior to anterior, then the lingual surfaces from posterior to anterior and concluded with a wave scan beginning at the buccal of the second molar and terminating at the lingual surface of the cuspid.  Scan pattern five (SP5) begins at the cuspid and involves alternately rolling from buccal to lingual to buccal from anterior to posterior.  Each scan pattern was repeated five times to create the files that were compared to the master model using Geomagic.  These values were then averaged to determine trueness and precision.  The data collected was forwarded to a statistician to conduct a statistical analysis to ensure the significance of the data.

 

Results:  The scan pattern did not affect the trueness or precision of any of the six scanners tested except for the CEREC Omnicam where the scan pattern two was significantly better than scan pattern three (p=.0360).  For all other impression systems, the scan pattern did not affect trueness or precision.   The rankings for trueness, from most true to least for sextant scan were:  PS>PE>TD>IE>3S>CO.  The rankings for precision, from most precise to least for sextant scans were:  3S> TD>IE>PE>PS>CO.

 

Conclusions: 

  1. The CEREC Omnicam using scan pattern 2 compared to scan pattern 3 presented the only statistical difference of the trueness or precision.
  2. For all the other scanners the scan pattern did not affect trueness or precision.
  3. For sextant scanning, only one statistically significant variant was found for one of the six scanners in which a difference in scan pattern affected accuracy.  Verifies that scan pattern or sequence will not affect the trueness and precision of the generated model with this one exception.

 

Acknowledgements:  Thanks to Dr. Wally Renné for his help and guidance and also to Geomagic Control X by 3D Systems for providing the comparison software used for this study. 

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