CAD/CAM in dentistry.

Abstract

A series of closely linked steps are required to make a fixed dental . prosthesis. After any preparation, the dentist m ust take an im pression of the prepared tooth, together w ith adjacent and opposing teeth, using elastic im pres­ sion m aterial. T h is im pression is used to obtain a hard stone model, and a wax pattern of the crown or inlay is carved. T h e actual cast restoration is ob ta ined by using the “ lost wax m ethod.” R egard less of the advanced sta te of this 300-year-old technique, inform ation m ust still be transferred by hand from the im p ress io n to the f in ish ed crow n via a series of materials, each of which may induce error in the final castings. T h is system of casting does n o t allow us to take ad v an tag e of trem en d o u s advances in com puters and robotics. For these reasons, we introduced CAD-CAM tech n o lo g ies to the d en ta l p ro fe ssio n in 1971. Early studies have been m ore exper­ im ental and theoretical than c lin ica l.1 4 A lthough these ou tstanding works have been c o n su lte d , we have stressed the c l in ic a l aspects of a p p l ic a tio n ra th e r than the fundam ental.5,6 In 1979, H e it lin g e r an d R o d d e r,7 followed by M oermann and Brandestini8 in 1980, began to share this approach. T he former researchers m illed the equiv­ alent of the stone model used by a dental te c h n ic ia n to m ake the crow n, in lay , o r p o n tic , w h ile the la tte r team took a s in g le p ic tu re an d m ille d o n ly the in te rn a l surfaces of the in lay . D u rin g the next 5 years, little was heard. T he f irs t d en ta l CAD-CAM p ro to ty p e was presented at the G aranciere conference (France) in 1983,9 an d the first crown was publicly m illed and installed in a m outh w ithout any laboratory involve­ m e n t in 1985.10 T h o u g h 1985 was a decisive year for com puter-aided dentist­ ry, there was still a long way to go. Several engineers took 2 hou rs5 to operate the f irs t u sab le system in a d en ta l office. Nevertheless, this dem onstration at the French Congress11-13 vindicated principles established 14 years earlier. T w o new names appeared at this time, the A oki team in J a p a n 14 a n d D iane Rekow at the University of M innesota.15,16 Dr. R ekow chose a p h o to g ra m m e tr ic m ethod to acquire the th ird dim ension and used the princip le of the theoretical tooth, which we had established earlier,5 for her second and th ird steps. It should also be m entioned that Reggie C audill, a t the U niversity of A labam a,17 started a project aim ed in the same direction. In this paper, a system that is already functional in dental offices in France— the D uret system, developed by H ennson In te rn a tio n a l (Los Angeles) under ou r direct supervision—is described.