Dale A. Miles DDS, MS, FRCD
and PJ Jaquith RT

Introduction

I was trained in the "Mecca" of panoramic radiography in San Antonio in the early ‘80s. If only I’d met my mentors, Dr. Bob Langlais, Dr. Ole Langland and Dr. Charles Morris years before! In my graduate program I learned in a very quickly about all the benefits and advantages of this incredible radiographic modality. Until then, in my dental practice, I had made every positioning mistake ever described, and there was no one in the dental industry who knew why the errors occurred or how to correct them. There was little education in panoramic radiography taught at any dental school back then. Like much of the technology introduced in the marketplace for dentists, it’s there before we really understand it. As I’ve said publicly many times before, when I’ve lectured in Panoramic Radiology, "…the technology was introduced way ahead of the education!"

I had my own machine, a G.E. Panelipse, cutting edge at the time, when there were really only 2 machine choices in North America (the Panelipse and the Panorex), in my office in Canada in 1976. I actually elected to put that panoramic machine in the office BEFORE I set up a second operatory! It made incredible economic sense even then.

Today, dentists have an incredible array of panoramic x-ray machines to choose from, and the choice can seem daunting, especially since most dentists have had little or no training in panoramic radiology. Even recent graduates of most dental schools tell me they’ve never positioned a patient in a panoramic machine. Incredibly then, they expect their assistants, with just as little training (usually from the sales person), to produce excellent quality films. The task seems impossible. However, because today’s panoramic machines are so "smart", and loaded with technological advances, this seemingly impossible situation has been largely overcome. There are even a number of excellent "digital" panoramic machines. Of course, there are some VERY "low end" panoramic machines; inexpensive (read cheap) machines that are "marketed" to dentists who "just want a basic machine". However as a buyer, beware, because you get what you pay for! Let me explain.

Panoramic Basics

There are many advantages to panoramic radiography including:

• Excellent anatomical assessment
• Excellent evaluation of jaw fracture
• Excellent imaging of tooth development
• Excellent evaluation of maxillary sinus problems
• Excellent preliminary assessment of TM disorders*
• Excellent preliminary assessment of potential implant sites
• Reduced x-ray doses to patients compared to full mouth radiographs

* a panoramic radiograph by itself is not adequate to full assess problem. Other radiographic views are usually indicated to more fully demonstrate the change/anatomy.

In fact many of today’s more contemporary machines have software programs built into them to perform the assessments of implant sites and temporomandibular joint changes. These programs are simple and efficient and, in most cases, easy to master. The machines are "smart", and prompt you with error codes if you’ve entered in put incorrectly. For patient safety, these machines will not let you expose the patient if the settings are not correct.

The more advanced machines are also equipped with light guides to simplify correct positioning of the patient minimizing the minor positioning errors. Positioning errors tend to plague owners of more elementary machines. A great booklet on positioning errors and their correction can be obtained from the Eastman Kodak Company in Rochester, New York.¹ It is called "Successful Panoramic Radiology" and was produced from the educational material developed in San Antonio by my classmate at the time, Dr. Birgit Glass. Is available from your dental dealer or can be ordered from Kodak’s web site.

Common Positioning Errors

Patient too far Forward
Anterior teeth are "minimized" (narrower), spine is superimposed over condyles and/or ramus.This is a very common error with edentulous patients because they have no teeth to bite on the pin.


Patient too far backward
Anterior teeth are magnified and apices are blurred. In this case the chin was too far down as well. Sometimes there is more than 1 error on the film!

Patient’s chin too high
Curve of Spee flattened (reversed), and condyles are lost off edge of film. Palatal shadows more prominent.





Patient’s chin too low
Curve of Spee exaggerated. Distortion (elongation) of anterior mandible. Lower apices out of focal trough.

Patient’s head rotated
Patient’s right side structures are enlarged compared to left. Look at the first molars and rami. The patient’s head was turned (rotated) towards the left side or away from the film when the tube was on the right.

Patient’s head tilted
Patient’s head tilted up on their left side. The mandibular angle is higher on that side.

If any of these images look familiar, don’t be alarmed. Dentists and their staff make these errors every day. However, thanks to advances in technology, these errors are not nearly as common with newer, advanced machines.

Advantages of Full-Featured) Panoramic Machines

Many innovations are available on the high-tech, high-end or "full-featured" panoramic machines. These include, but are not limited to the following:

• More consistent image quality
• Light positioning guides for easier positioning
• Advanced software for specialized views (implant, TMJ, etc…)
• Custom collimators for different patient sizes
• Customizable focal troughs (the layer of sharp focus) for better image quality
• Programmable sectional views (example, sinus area only or just 3^rd molars)
• Automatic labeling of patient/office information
• Electronic attachment to insurance claims when using panoramic "digital" machines
• Upgradable to future advances in program software
  

If you are contemplating any procedures such as TMJ imaging, or implant site imaging, you cannot afford to overlook the more feature-rich panoramic machines such as those from Planmeca. Although they appear expensive at first glance, their imaging capabilities and clinical benefits are quite remarkable and will pay for themselves in a very brief period. For example, Planmeca’s DIMAX digital panoramic system allows for "real-time" image acquisition with the panoramic image appearing on the computer monitor as soon as you expose the patient.

An example of a panoramic radiograph from Planmeca

Figure 1

In addition the image resolution defined by the SNR (signal-to-noise ratio) is exceptional for digital panoramic machines. The signal is the disease or change you are looking for, the noise is everything that degrades the image and reduces the signal strength. Digital panoramics like he DIMAX have an excellent signal-to-noise ratio. This is because they capture the image at a very high image resolution (17 bit = 2¹⁷ or 131,072 gray levels!). This can result in line pair (lp) resolution (detail) of about 6 lp/mm! The digital panoramic produces a more pleasing image to the dentist that is rich with clinical information. Film-based panoramic images have a resolution of between 4-6 line pairs/mm. High-end, digital panoramic machines dramatically outperform conventional film-based machines and approach the spatial resolution of intraoral receptors. Like digital, intraoral systems, panoramic digital images can be enhanced by electronic image processing after the radiograph is taken! ²

In addition to the benefits of electronic image processing to enhance diagnostic features, full-featured panoramic machines allow dentists to produce cross-sectional images that are not obtainable with lower priced machines.

Figure 2 Lower molar implant site showing 3 separate views and mandibular canal. Examples courtesy of Planmeca, Inc.

Reduced X-ray Doses

A major benefit of the digital panoramic machines is the dramatically reduced x-ray dose to your patient. Patients will appreciate your investment in technology to reduce radiation and will refer other people to your practice. In addition, reducing the patient’s radiation burden is a continual goal for all of dentistry. There’s no better way to do it than to "go digital". Some manufacturers state a 70% reduction in x-ray dose with their digital panoramic machines.

A Simple Financial Example

Let’s say you spend $28,000 for a full-featured panoramic machine. If your typical charge for the film is $65, and you take 15 new films/week for 50 weeks, you will generate $48,750 in the first year in fees! This covers the total cost of the machine and you realize a profit of over $20,000. If you lease the machine over a 3- or 5-year period, you can generate excess revenue on a monthly basis to pay other bills! Check with your to see how you can realize additional tax benefits from the purchase. By the way, unless you’re buying a "digital" panoramic for $50,000 plus, the typical cost for most high-end panoramic machines is less than $25,000. If you are planning to upgrade your current panoramic or are a "first-time buyer", you should definitely consider full-featured panoramic x-ray machines like the Planmeca. Although they appear expensive at first glance, the imaging advantages and ease of use helps to pay for the device in a very short period.

"So, What About Digital?"

Despite the slow acceptance of digital technology by dentists, I for one, think that digital imaging is inevitable for our profession. Many manufacturers offer "digital" panoramic x-ray machines at $50,000 or more! Is it worth it?

Digital panoramic images are outstanding in detail, contrast and edge enhancement. The fact that you can perform image enhancements after the patient is exposed and improve diagnoses should at least be intriguing to you. Here is an example of a digital panoramic image.

DIMAX panoramic from Planmeca, Inc.

The image is visually more detailed then most traditional film-based panoramic images. The scale of contrast (latitude) is also wider than conventional films. Any dentist would love to show this image to a patient or colleague. Some manufacturers, like Planmeca, can easily "upgrade" their film-based machines to digital allowing current Planmeca panoramic x-ray owners to take advantage of this revolutionary technology and electronic image processing capabilities. These images can even be attached to insurance submittals electronically! This is really where our profession is headed, and will keep you ahead technologically.

Conclusions

In conclusion, because of the following observations:

• Panoramic machines are now much easier to place patients into correctly
• Many panoramic errors have all but been eliminated by contemporary machines
• Software programs provide excellent enhancements for clinical tasks such as imaging the temporomandibular joint or assessing pre-surgical implant sites
• Digital panoramic machines are available now for more advanced offices
  
• "You Get What You Pay For!"
• panoramic machines make excellent financial sense, just as they did 25 years ago for me – even as elementary as they were!

References

1. Successful Panoramic Radiography, Kodak Dental Radiography Series, 1991, Glass BJ, Editor
2. Miles DA, Langlais, RP and Parks ET: Digital X-rays Are Here; Why Then Aren’t You Using Them? CDA Journal, 27(12): 926-934, 1999.