Dental Tribune Indian Edition

22 Dental Tribune Indian Edition - April 2013Trends & Applications a tooth can be demonstrated when viewed from the incisal perspective. A study by Yammamoto demonstrates this well (Figs. 13–15). From the inci­ sal perspective, the relative flatness of the square shape, the concavity of the triangular shape and the convexity of the ovoid shape is apparent. Another decisive aspect of a suc­ cessful natural reproduction is the design of the marginal ridges or line angles, which has an effect on the 3D appearance of the tooth. Besides the shape and the width of the tooth crown, the width of the root is also a decisive factor. Up to now, I have restricted the consideration of the tooth to the labial and incisal view. In order to be able to replicate the 3D appearance of the tooth, we must also consider the labial curva­ ture of the tooth (Figs. 16–18). From this point of view, the incisal trian­ gle features can also be divided into the three basic components. For each individual case, it is then necessa­ ry to derive the respective hybrid shape. After this has been considered, the following types can be derived from the mesial view: The oval anatomy type • The two well­developed labial mar­ ginal ridges are the key characteri­ stic feature of this anatomy type. • A strong labial depression and a wide labial transitional surface are present. The difference between the mesio­ and the disto­approxi­ mal surface is noticeable. The di­ stal face is wider than the mesial. • The growth lobes are generally not very prominent with this tooth sha­ pe type. The three­angled anatomy type • The mesial and distal marginal ridges are again distinct but not as strong as with the oval anatomy type. • The labial surfaces are relatively wide, without a noticeable differen­ ce in width between the mesial and the distal. • The labial and proximal growth lo­ bes are prominent. The square anatomy type • The characteristic feature of this anatomy type is the indistinct mar­ ginal ridges, which can sometimes cause a rather plain look. • A well­developed central marginal ridge is present, which appears qui­ te prominent when viewed from the incisal edge. • The labial and approximal depres­ sions are somewhat strongly deve­ loped, although not as strongly as with the triangular type. The marginal ridges or line angles develop in the sulcus and run parallel to the basic outer shape of the tooth towards the incisal edge. At the in­ cisal aspect, the progression of the marginal ridges differs between una­ braded juvenile teeth and worn aged teeth (Figs. 19–24). These different morphological characteristics are evident in the case of adjacent teeth, which makes the reconstruction of a single tooth quite easy. A great deal of information is needed in order to rebuild the shape of a tooth and to recreate a natural, harmonious look. It becomes more complicated when it is necessary to replace the who­ le anterior segment or the dentition in an entire jaw. For this reason, the knowledge of the anatomical features of the single tooth is very important. A further aid for determining the definitive width of the teeth is the width of the nose base, which agrees in most cases with the width of the front teeth (Figs. 25–27). In his theory, Gerber suggests, amongst other things, that from an embryogenetic view the proportion of the nose base and the width of the nose root can be determined (Figs. 28–31). When it comes to determining the length of the anteriors, some clues can be derived from the age of the patient. The lip type is of great importance here. In vertical perspective, we di­ stinguish between a full and thin lip and/or between a long and short up­ per lip (Figs. 32–34). Patients with short upper lips expose more of their teeth than patients with longer upper lips. The lips outline the space that is subdivided by the arrangement of the teeth, which typically determines certain aesthetic key factors. One can achieve harmony with the remaining parts of the oral region by weakening or intensifying the visible tooth areas. Conclusion In this article, I have only paid attention to the upper anteriors. The main reason for this is that the upper anteriors are aesthetically much more significant than the lower anteriors. The different shapes of teeth can be observed on both the upper and lower anteriors from the facial, mesial and distal aspects. This method for achieving aesthetic harmony can be summarised as: 1. analysis of the facial parts, i.e., face shape type; 2. analysis of the dento­facial parts, i.e., lip–nose type; and 3. analysis of the intra­oral area, i.e. bite situation and remaining dentition. DT Fig. 25: The nose base determines the width of the upper anterior teeth (Gerber).—Fig. 26: The average nose type correlates with the average width of anterior acrylic teeth.— Fig. 27: A narrow nose base is an indication of slender anteriors. Fig 25 Fig 26 Fig 27 Fig. 28–31: These images show just a few of the many dento-facial varieties that can be found in nature. Fig 28 Fig 30 Fig 29 Fig 31 Fig. 32: Very full lips suggest long upper anteriors.—Fig. 33: The standard lip type.—Fig. 34: The shallow lip type suggests relatively short anteriors. This is also due to the small distance between the nose and the upper lip. Fig 32 Fig 33 Fig 34 Björn Maier is a Ma­ ster Dental Technician at the Polyclinic of Pro­ sthodontics, Ludwig­ Maximilians­Universi­ ty. He can be contacted at info@bjoern­maier.com. Contact Info ← DT page 21