[Oradlist] Simplant conversion and Icat studies

Thu Feb 14 15:37:05 PST 2008

I do a lot of Nobel Guide and simplant scans, on the Nobel Guides I have the software to do the conversion.

My experience with the NewTom is somewhat similar to that of Manon on the I-Cat.

What is important to remember is that the surgical guide is tissue supported.  The holes in the maxilla do not change the fit or accuracy of the guide.  The referring doctor should not be using a 3-D view as a radiographic diagnostic image.  You can remove so much bone in the 3D mode that it does relate well to the actual bone, your cross sections are much more accurate.

The 3D views that these software packages provide can be used to visualize surrounding teeth or teeth that have been simulated in the wax up for the radiographic guide.  The implants can be placed and aligned in these packages but it is much more accurate for the doctor to go back to the native software of the imaging device or to properly printed hard copy.

Given the nature and thickness of the cortical plate this is a much bigger problem in the maxilla than the mandible.

As far as the guide not being visible, the only time I have problems with this is when it has not been made according to the protocol provided by the software system manufacturer.

The imaging protocol is very similar between Simplant and Nobel Guide but the materials are critical to good imaging and each system have different preferred materials.  I cannot count how many cases I turned away due to guides that I can tell will not work.

I hope this helps.

Dan Halpert
Halpert Dental X-Ray 
  ----- Original Message ----- 
  From: Benson, Byron 
  To: Oral Radiology Discussion Group 
  Sent: Thursday, February 14, 2008 11:06 AM
  Subject: Re: [Oradlist] Simplant conversion and Icat studies

  Arun:

  In your response to Manon, you mentioned a relationship of FOV the accuracy of the gray level (HU) on CBCT.  Could you expound on that a bit and explain the relationship in a little more depth?  Can you predict how small an FOV would be required to closely approximate multidetector CTs?

  Thank you!

  Pete
  ------------------------------------------------------------ 
  Byron W. (Pete) Benson, D.D.S., M.S. 
  Diplomate, American Board of Oral & Maxillofacial Radiology 
  Diplomate, American Board of Oral Medicine 

  Professor & Director, Division of Radiology 
  Director, Oral & Maxillofacial Imaging Center 
  Texas A & M Health Science Center 
  Baylor College of Dentistry 
  3302 Gaston Avenue 
  Dallas, Texas 75246 
  Telephone: (214) 828-8393 - office; (214) 828-8479 - Imaging Center 
  Telefax: (214) 874-4551 or (214) 874-4557 
  Email:  Bbenson at bcd.tamhsc.edu 

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  From: oradlist-bounces at lists.ucla.edu [mailto:oradlist-bounces at lists.ucla.edu] On Behalf Of Singh, Arun
  Sent: Wednesday, February 13, 2008 3:50 PM
  To: Oral Radiology Discussion Group
  Subject: Re: [Oradlist] Simplant conversion and Icat studies

  This phenomenon is fairly common in CBCT, when it comes to maxilla with little bone and thin cortical plates. Primary culprits are diminished bone-soft tissue contrast due to scatter radiation (especially when bone is very thin), and volume averaging effect. You can minimize this problem by employing a smaller FOV (8cm height, or even 6cm if only 1 arch is required), which cuts down on the scatter significantly and reclaims some of the lost contrast, in addition to bringing the HU ranges closer to their medical CT counterparts.

  Arun

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  From: oradlist-bounces at lists.ucla.edu [mailto:oradlist-bounces at lists.ucla.edu] On Behalf Of Paquette Manon
  Sent: Wednesday, February 13, 2008 4:29 PM
  To: oradlist at lists.ucla.edu
  Subject: [Oradlist] Simplant conversion and Icat studies

  Dear all, 

  Have any of you had negative comments or problems with the conversion of I-cat studies with SIMPLANT master.  We are having problems with scans of the maxilla where especially there is no bone, or when hyperpneumatization of the maxillary sinuses leave the buccal and palatal plates very thin.  The bone structures are seen on the scan but when converted with SIMPLANT there are many wholes, fenestrations etc.  We tried to work with the Hounsfield unit scale on Simplant to get the maxilla more apparent but this increases the amount of noise in the image that we need to edit.  We have the same problem when the referent sends a radiographic stent that is made like a bleaching tray, very flexible plastic.  The stent is seen on the scan but not in SIMPLANT.  Our scanning protocol is FOV 13 cm, Time 20sec, 0.4 mm voxel.  Our Simplant representative in Montreal states that it is a problem with the ICAT software!?  I am already working with imaging sciences on this but would appreciate anyone's input and experience.

  Kindest regards,

  Manon Paquette, DMD, MS

  Associate professor

  Head of diagnostic imaging, emergency and diagnosis

  University of Montreal

  Faculty of dentistry

  514-343-6072

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