Other Free Encyclopedias » Online Encyclopedia » Encyclopedia - Featured Articles » Contributed Topics from A-E

Dental Photography - Technical Equipment, Camera body, Macro lens, Flash, Other Considerations, Standard Views

results teeth intraoral illumination

WOLFGANG BENGEL, DDS
Dentist

Dental photography deals with the special photographic procedures associated with dentistry. There are some specific challenges in this field, which justify it as a specialty within medical photography. The aim is to document the state and changes in teeth, mucous membranes of the mouth, and the perioral region under conditions that can be readily reproduced.

In intraoral photography one of the main problems is difficult access to the objects to be photographed, which are hidden in the oral cavity. This makes illumination difficult and special equipment is needed to create good images. Other problems are the highly reflective areas in the mouth and objects that show big differences in brightness, which leads to exposure difficulties. As the main purpose of taking photos is documentation, a certain standardization is necessary with respect to framing, inclination of the camera, magnification ratio, and illumination. In addition, objects of interest are tiny, which means working in the macrophotography regime, where magnification ratio, depth of field, perspective distortion, illumination, etc., become important. At the highest magnification ratios we need lighting that shows the outline of the object, the surface texture, the color, and even some inner structures of our semitransparent teeth as well.

Technical Equipment

The camera system mainly used for dental photography consists of an SLR camera (today normally a digital one), a macro lens, and a flash.

Camera body

Every major camera manufacturer offers one or more camera bodies for the advanced amateur, many of which are suitable for dental photography. More expensive professional bodies and cameras with full-format digital sensors are not absolutely necessary for use in dentistry. A resolution of 6 megapixels is sufficient for most purposes. A viewfinder screen with a grid is very helpful for aligning the camera to get reproducible results.

Macro lens

The reproduction ratio required for dental work may be approximately 1:3 (perioral region) as defined on the chip size and 2:1 (upper middle incisors filling the frame, or individual molar). In conventional film dental photography, a 100mm macro lens was the recommended standard lens. Because most digital cameras use smaller detectors than film, a lens factor (typically 1.5) has to be taken into account, so a 60mm macro lens will also work and will produce a different working distance. The advantage of a shorter focal length is that the whole system is rather small. Because of the short object distance, a macro flash or a ring flash should be used in combination with a 60mm lens. A twin flash will create problems when combined with a 60 mm lens because of the lighting angle.

Flash

As intraoral photography is photography within a cavity, a ring flash or ring flash-like macro flash is widely used. An inexperienced user will quickly achieve good results with such a flash, even when taking shots of the especially challenging molar regions. The disadvantage of ring flash lighting is that results mostly lack image plasticity and look rather flat. Better results can be obtained when using twin flash systems. Their light output is higher, which results in larger depth of field and illumination shows more three-dimensionality. A disadvantage of using twin flashes is that for every single shot, the position of the reflectors has to be checked and corrected.

Other Considerations

Important accessories for intraoral photography are lip and cheek retractors, photographic mirrors, and contrasters, which are black backgrounds placed behind the teeth to improve image composition and eliminate distracting background. Mirrors may be made of metal or (better) surface-coated glass, and cutting off one end of the retractor facilitates mirror photography, especially the occlusal views. Mirrors with plastic or metal handles are easier to use. These mirrors create their reflection from the top surface rather than the traditional rear surface.

Standard Views

Reproducible conditions for photography are sensible because they save time and achieve consistent results. For these reasons it makes sense to take the basic intraoral views in a standardized approach. The essentials of this are that the optical axis should run through the occlusal (bite) plane—photographing from below distorts the perspective of the incisors. In lateral views, photographs should be perpendicular to lateral teeth (with the aid of a mirror), and occlusal views should be as near perpendicular to the camera as possible (also with the aid of a mirror). Finally, the occlusion plane should be parallel to the horizontal frame of the photograph.

The correct orientation is an important factor in producing reproducible images and to improve perception. The basic intraoral views can differ for an orthodontist, who specializes in the prevention or correction of irregularities of the teeth, and the periodontist, who deals with the treatment of the gums, soft tissues, and bones that support the teeth. However, it is important to continue to follow the same standardized procedure once chosen.

Other, often-used special fields of dental photography are basic techniques such as copy work, generating teaching visuals, portrait photography, object photography, and photography in the operating theater. Here the general guidelines of the specialties have to be followed. In portrait photography, standardization is mandatory: Framing, camera position, patient position, and illumination should be reproducible.

The main problems of dental object photography are that objects of interest are tiny in most cases and some are highly reflective polished metal. Others have a very low object contrast (e.g., white casts) or are semitransparent. Beside general problems of macrophotography, innovative lighting techniques (light tent, transmitted light, etc.) have to be used for optimum results. Finally, in dental surgery, access to the operating field is difficult and it is not easy to get a clean and dry situation. Thus, even with modern techniques and equipment, dental photography is challenging.

Deposition [next] [back] Dennis, Gary C.(1950–) - Surgeon, educator, Begins Teaching Medicine, Becomes Healthcare Advocate, Chronology, Power Couple Achieves

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or

Vote down Vote up

12 months ago

I agree. I use just 6 mpx all the time for my dental photographs. They were even published by my house editorial three months ago.