Copyright r Blackwell Munksgaard
ENDODONTIC TOPICS 2005
Mechanical preparation of root canals: shaping goals, techniques and means
¨ MICHAEL HU LSMANN, OVE A. PETERS & PAUL M.H. DUMMER
Preparation of root canal systems includes both enlargement and shaping of the complex endodontic space together with its disinfection. Avariety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Although many reports on root canal preparation can be found in the literature, deﬁnitive scientiﬁc evidence on the quality and clinical appropriateness of different instruments and techniques remains elusive. To a large extent this is because of methodological problems, makingcomparisons among different investigations difﬁcult if not impossible. The ﬁrst section of this paper discusses the main problems with the methodology of research relating to root canal preparation while the remaining section critically reviews current endodontic instruments and shaping techniques.
Preparation of the root canal system is recognized as being one of the most importantstages in root canal treatment (1, 2). It includes the removal of vital and necrotic tissues from the root canal system, along with infected root dentine and, in cases of retreatment, the removal of metallic and non-metallic obstacles. It aims to prepare the canal space to facilitate disinfection by irrigants and medicaments. Thus, canal preparation is the essential phase that eliminatesinfection. Prevention of reinfection is then achieved through the provision of a ﬂuid-tight root canal ﬁlling and a coronal restoration. Although mechanical preparation and chemical disinfection cannot be considered separately and are commonly referred to as chemomechanical or biomechanical preparation the following review is intended to focus on the mechanical aspects of canal preparation cavity.Chemical disinfection by means of irrigation and medication will be reviewed separately in this issue.
History of root canal preparation
Although Fauchard (3), one of the founders of modern dentistry described instruments for trepanation of
teeth, preparation of root canals and cauterization of pulps in his book ‘Le chirurgien dentiste’, no systematic description of preparation of the root canalsystem could be found in the literature at that time. In a survey of endodontic instrumentation up to 1800, Lilley (4) concluded, that at the end of the 18th century ‘ . . . only primitive hand instruments and excavators, some iron cauter instruments and only very few thin and ﬂexible instruments for endodontic treatment had been available’. Indeed, Edward Maynard has been credited with thedevelopment of the ﬁrst endodontic hand instruments. Notching a round wire (in the beginning watch springs, later piano wires) he created small needles for extirpation of pulp tissue (5, 6). In 1852 Arthur used small ﬁles for root canal enlargement (6–9). Textbooks in the middle of the 19th century recommended that root canals should be enlarged with broaches: ‘But the best method of forming thesecanals, is with a three- or four-sided broach, tapering to a sharp point, and its inclination corresponding as far as possible, with that of the fang. This instrument is employed to enlarge the canal, and give it a regular shape’ (10). In 1885 the Gates Glidden drill and in 1915 the K-ﬁle were introduced. Although standardization of instruments had been proposed in
Mechanical preparation ofroot canals
1929 by Trebitsch and again by Ingle in 1958, ISO speciﬁcations for endodontic instruments were not published before 1974 (10). The ﬁrst description of the use of rotary devices seems to have been by Oltramare (11). He reported the use of ﬁne needles with a rectangular cross-section, which could be mounted into a dental handpiece. These needles were passively introduced into the root...