Holograms in orthodontics: a universal system for the production, development, and illumination of holograms for the storage and analysis of dental casts.

It is well known that working with plaster study models has a great amount of disadvantages. Many studies have been carried out to eliminate these problems seeking substitutes or alternate working techniques. A small number of research teams have developed some holographic based systems applied to orthodontics. The purpose of this report is to provide clinicians with a universal holographic system that does not require prior technical knowledge of holographic science. An easy-to-use technique is presented in a user-friendly environment by including an automatic developer. The holograms obtained permit three dimensional model analysis, superimpositions, and storage. The system has been evaluated by comparing canine distance and maxillary depth measurements (center of midpalatine raphe to maxillary canine) obtained from models and their corresponding holograms. A statistically based study on the repetition of means was carried out. The precision obtained from hologram measurements falls between 0.05 and 0.2 mm. Depth measurements from holograms produce larger values than those made on models. This is due to the fact that the wavelength of the holograms is different than the one used on the laser source. The differences are clinically insignificant. Dental casts made of plaster are commonly used to aid orthodontic diagnostics. They are easy to make, give precise information for clinical purposes, and the material is very inexpensive. They do, however, present several disadvantages: The casts are heavy and fragile, and they require a lot of storage space. The increased popularity of orthodontic treatment and the growing number of patients has also led to an increase in legal actions and complaints. Many scientific societies and authors strongly recommend that practitioners retain orthodontic records throughout their entire careers. 1 To date, few methods have been proposed to overcome the above-mentioned disadvantages and to create a more ideal registered system to take the place of dental casts. Photography has been in use for a long time and techniques such as photocopying, video images, and computers are being used, all with limited success. One promising technique is holography. 2 Holography uses laser light to reproduce a very highquality, three-dimensional image of a cast. The resulting hologram has many applications and clinical advantages. Different authors have studied the analysis of dental casts with holograms. A comparison of measurements taken from holograms show some discrepancies when compared with those taken from the original casts, particularly when measuring depth. 3-s Good results have, however, been obtained when holograms are used in actual clinical situations. Positive results have also been accomplished with holograms in the study of epidemiologic indexes (PAR index and Summers index) ¢.7 Despite the recommendations of scientific societies to retain casts for a long time, a survey has shown that most orthodontists do not store their casts indefinitely as suggested. Holograms may be used for storage purposes. 8 Previously mentioned studies have indicated thatholograms could provide considerable clinical advantages. This article presents a technique, the New Universal System, that uses a new holocamera, a visualization system that permits precise three dimensional measurements, and a special instrument to develop holo-