Common dental photography errors Part 1

 I'm continuing the theme of photography and records with this post with a few of the most common photography errors that I have made and learned from, but still make from time to time. These errors may harm the diagnostic quality of the photos. If we are going to the effort of capturing the photos in the first place it is important that we try our best to make them the best quality and as useful as they can be. 

I made a post previously about some basic camera settings which may be useful for complete camera newbies: https://dental-tidbits.blogspot.com/2020/04/basics-of-photography.html 

• Buccal shots should be perpendicular to the teeth  

This is one I learned at the Orthoed Minimasters. For orthodontically diagnostic images, the buccal shots must show the canine and molar relationship accurately. This means that the photos should be taken perpendicular to the posterior plane of occlusion. Most commonly, the buccal shots are taken angled from the anterior as we are trying to get around the cheek to capture as much of the posterior teeth as possible. the images below are screenshots of an intraoral scan of the same patient from different angles. 

This view is angled from the anterior direction and is not perpendicular to the posterior teeth. We have all the details of the teeth and this is sufficient for diagnostic purposes. For orthodontic purposes, it gives a false representation of the molar and canine classification. The canine and molars look like a good class 1 relationship here, but if you look at the premolars, you begin to suspect that there is not a class 1 relationship, as well as the retrusive upper incisors which may indicate a compensated class 2 relationship.

This screenshot is of the same patient with the view perpendicular to the posterior teeth. For general diagnostic purposes, there is less information about the anterior teeth but that can be gained from the frontal view. The canine and molar classification can be clearly seen as a 1/2 unit class 2 relationship. This is the more accurate view for orthodontic records.

The proper way of capturing this view is to use a buccal mirror on the photographed side and a cheek retractor on the opposite side to stop the lip from folding into the image. The mirror can be swung out to retract the cheek and get the right angle of the posterior teeth. This can be seen in the photo below. I don't use mirror shots to capture the buccal segments.  Instead, I get the assistant to retract as much as they can with the cheek retractors and take the photo directly. When trying to get the image perpendicular to the posterior teeth, I will usually lose the image of the molars if the assistant is not pulling hard enough or the patient has very tight cheeks. I prefer the shorter height and longer V shaped retractors as the taller C shaped retractors will leave less slack to pull the cheek posteriorly.

Set up for a buccal mirror shot. For orthodontic records I would want to swing the mirror out further to the side or position the camera more around the left side of the patient to get more of a perpendicular photo. 

 V shaped retractions on the left and C shaped retractors on the right. The C shaped retractors are useful to show the anterior areas as it holds the lips more open but for the posterior segments I prefer the V shaped retracts as the sharper angle in the centre of the retractor can more efficiently pull on the cheek and the shorted vertical dimension leaves more slack on the lips so that the cheek can be pulled further.

A frontal retracted photo. One side has V shaped retractors, one side has C shaped retractors. The left side of the image has more vertical retraction so we can see more of the anterior soft tissue, the right side of the image has more hotizontal retraction so I can see more of the molar and cheek area. I prefer to have more horizontal retraction

C shaped retractors: The camera should have been positioned a bit more distal as the view is not quite perpendicular

A more V shaped retractor: The angle is a bit better but not perfect

A good perpendicular shot showing the buccal relationships, however the trade off of the sharper angle is that the whole of the upper molar isn't captured in the photo

 

• Scratched mirrors 

This point speaks for itself. Don't use scratched mirrors. One practice I work at is terrible for scratched mirrors. They never throw anything out no matter how damaged they are. Look at the photos below and you can see how the diagnostic value of the photo is harmed by the scratches on the mirror. There is still lots of information there but the scratches are a distraction. When I am showing my patient's their photos, they always have to ask "What's that?" in reference to the scratches and I waste time and effort every time. More importantly, they are distracted from the proper message I am trying to convey to them. If there are badly scratched mirrors, separate them from the stock and use them for restorative procedures. Ensure there is a good system in place to avoid scratches to new mirrors. The mirrors should not come in contact with any hard instruments, shouldn't go through the ultrasonic cleaner and should be handled wit the utmost care.

 

• Check your exposure settings prior to the shot: 

The three settings we can alter to affect the exposure are shutter speed, ISO and Aperture. I leave my shutter speed at 1/160, ISO at 100 and I alter aperture depending on the requirements of the photo. f/18-22 for intraoral shots and f/5.6-8 for extraoral shots depending on how much of the patient I am capturing.

 

Probably the two most important consequences of incorrect settings are the brightness of the image and the depth of field of focus of the image. 

 

Regarding the brightness of the image, if you are shooting with a flash in ETTL mode, the brightness of the image may matter less as the flash will output more or less power to compensate for the exposure settings. For example, if you are taking a full face photo with the aperture set to f/22, the aperture of the lens will be small so less light will get in and the photo may end up dark. The camera will recognise this and communicate to the flash to push out more power and this will balance the exposure to the correct level. If your flash is not particularly powerful, the photo will still turn out dark as the flash's maximum power will be output and it will still not be enough to correctly expose the image.

The depth of field however is something that can't be compensated for. If you shoot an extraoral shot at aperture f/22, the photo will turn out dark but this can be compensated for post production in an photo editing software. The worst situation is when you shoot intraoral photos where you need good depth of field with a wide aperture e.g f.8. There will be more light let into the lens so the flash will compensate by reducing the light output. So the photo will look correctly exposed. However, the depth of field will be reduced so that less of the photo will be in focus. For intraoral shots, we need as large of a depth of field as possible as we want to capture the front and the back of the arch in focus to capture a diagnostic level of quality. 

 

Commonly, the staff I have worked with who don't understand the settings just use whatever settings were last set on the camera. Below is an example of intraoral shots that were taken with extraoral settings (f/6.3)

 

Frontal retracted shot: The anterior teeth are in focus but the posterior teeth are blurry

Right side retracted shot: Detail is lost as the posterior teeth are not in focus

Upper occlusal mirror shot: Here the focaus point would have been in the centre of the frame so the hard palate is in focus. As the molars are similar in distance to the palate they are in focus but the incisors in the mirror are much further away from the camera lens they are out of focus. In this photo, the camera is too far from the subject as there is too much outside of the mouth that is visible. Interestingly though, the further the camera is from the subject, the deeper the depth of focus will be so in this case it will have improved the image's focus. However the aperture setting was too far off for the image to be acceptable.

• Make sure your memory card is inserted

This happens to me all the time. I take the memory card out to upload the recent photos onto the computer and I forget to reinsert the card. Come the next patient and if I'm lucky, when I take the first photo I will see the popup on the camera screen that the card is not inserted but I have once or twice taken a full series of photos before realising the card was out and then had to retake the photos. I know some newer mirrorless cameras have two SD card slots which may eliminate this problem but it just makes sense to get in the habit of replacing the SD card into the camera when the photos have been uploaded.

 I will continue this is a part 2 post when I get more time.