PEDIATRICDl~NTISTRY/Copyright © "i989 by The AmericanAcademy of Pediatric Dentistry Volume 11, Number3 Association of taurodontism with hypodontia: a controlled study W. Kim Seow, BDS, MDSc, PhD, FRACDS P.Y. Lai, BDSc Abstract Although taurodontism has been reported in many been suggested for both taurodontism (Jorgenson 1982; syndromeswhich also lea t u re hypodontia, there have been no Hamneret al. 1964) as well as hypodontia (Barjian 1960), previous investigations on the prevalence of taurodontismin it is likely that these two traits may be associated. patients with hypodontia. Using a novel biometric methodfor Further support of this concept is the fact that the assessment of taurodontism, we found that 34.8%of 66 taurodontism also may be observed in amelogenesis patients with hypodontia had at least one mandibularfirst imperfecta (Witkop and Sauk 1971), a defect permanent molar which showed taurodontism compared to ectodermal origin. In this study we investigated the only 7.5% of a control group without hypodontia. The trait prevalence of taurodontism in a group of children with may be seen both unilaterally and bilaterally and is most hypodontia compared to a control group. To establish frequently seen in patients with multiple missing teeth. The the diagnosis of taurodontism objectivity, a novel results indicate that clinicians should be alerted to the biometric technique was employed. possibility of taurodontism with its accompanyingclinical difficulties in patients with hypodontia. Materials and methods Introduction Patients with hypodontia Randomscreening of 1032 patient records which had The term taurodontism was first used by Keith in panoramic radiographs from the pediatric dental clinic 1913 to describe the molars of Neanderthal human at the University of Queensland Dental School revealed fossils which "had a tendency for the body of the tooth that 66 patients (6.4%) had agenesis of at least one tooth. to enlarge at the expense of the roots." This trait, which There were 37 males and 29 females, and their mean age is of significance to dental clinicians, is also of interest to at the time of radiography was 11.08 + 2.9 years (range anthropologists in the determination of the evolution of 5-19 years). All the patients were Caucasian and had man (Shaw 1928; Jorgenson 1982). hypodontia as an isolated trait, and did not suffer these Taurodontism has been reported as an isolated trait defects as part of an overall syndrome. in many case reports (Lunt 1954; Album 1958; Mangion 1962; Hamner et al. 1964; Metro 1965; Regattieri and Control patients Llewellyn 1972; Durr et al. 1980; Seowet al. 1985) which For every patient with hypodontia, a control was may have a familial tendency. In addition, selected who matched the study case for both gender taurodontism has been documented as a manifestation and the age at which the panoramic radiograph was of multiple-system malformation syndromes, taken. All control patients were shown to have a full including the tricho-dento-osseous (TDO) syndrome permanent dentition from the radiographs. In addition, (Lichtenstein et al. 1972), Kleinfelter syndrome(Stewart they did not suffer from any defects which may be 1974), otodental dysplasia (Levin et al. 1975), features of medical syndromes. ectodermal dysplasia (Stevnick et al. 1972), and Down Selection of molar tooth for measurement syndrome (Jaspers 1981). The mandibular first permanent molar was selected However, although missing teeth may be an as the tooth for analysis for several reasons. First, the associated feature in manyof the cases of taurodontism first molar is considered the most stable tooth of the cited in the literature, there have been no previous series; hence, any change in its morphology may studies investigating the prevalence of taurodontism in indicate a true change of the molar series. In particular, hypodontia in general. As an ectodermal origin has the cuneiform single-rooted molar which is not 214 TAURODONTISM AND HYPODONTIA: SEOW AND LAI considered a form of taurodontism (Blumberg et al. Similarly, the length R was determined along the same 1971) is rarely seen in the first molar, thus eliminating vertical axis from the furcation to the root apex. possible errors from misdiagnosis. Second, the entire Validation of method outline of this tooth usually is evident clearly on the As panoramic radiographs may be associated with panoramic radiograph in contrast to the maxillary distortions (Pilo 1987; Balis 1981), we compared the molars where the root apices usually are obscured by accuracy of the images of mandibular first permanent the zygomaticbone; hence, lengths of the roots are easily molars on the panoramic radiographs with the images determined. Finally, this first permanent molar is of the same teeth on periapical radiographs taken with usually the only fully developed molar in the age group the parallel long-cone technique. The radiographs of under study. twenty patients (11 females, 9 males) whowere not part Tooth measurements of the study population were used for analysis. All The outline of mandibular first permanent molar patients had a panoramic radiograph taken at about the teeth first was traced from the panoramic radiograph same time as a long-cone periapical radiograph of a onto transparent paper from which measurements were mandibular first permanent molar. As the latter taken. The parts of each tooth comprising the crown, technique is associated with minimal distortion, body, and root were identified using the following comparison of CB:Rratios in the mandibular first molar definitions: Crown (C) - from the deepest part between the two techniques may determine possible occlusal surface to the cementoenamel junction (CEJ); discrepancies due to distortion on the panoramic Body(B)--from the CEJ to the root furcation; Root (R) radiographs. from the root furcation to the apices (Keith 1913; Shaw The results (Table 1) showed that the mean 1928; Mena 1971). Figure 1 shows these anatomical difference in CB:Rratio in the mandibular first molar divisions on a taurodontic molar. between the two techniques was not statistically The lengths of the crown plus body (CB) as well as the significant (P > 0.1), indicating that for this tooth root (R) were measured as shownin Fig 1. The CBof the tooth was determined by drawing an occlusal line TABLE1. Comparison of Crown-Bodyto Root Ratios through the deepest pit which is parallel to another line (CB:R) using Panoramic (PAN)vs Periapical (PA) joining the cusp tips (Fig 1). The length was determined Cone Techniques along a vertical axis drawnat right angles to the occlusal CB:Rof Mandibular First line measured from the deepest pit to the furcation. Permanent Molar Difference Patient Panoramic* Parallel Technique in CB:R No. (PAN) Periapical (PA) "PAN Minus PA) 1 0.76 0.77 -0.01 2 1.05 1.10 -0.05 3 1.26 1.29 - 0.03 4 0.93 1.00 - 0.07 5 0.95 1.00 - 0.05 Crown 6 1.04 1.05 - 0.01 7 0.75 0.88 - 0.13 CB (C) 8 0.81 0.95 -0.14 9 1.00 1.00 0.00 Body 10 0.91 0.94 - 0.03 (B) 11 0.94 0.95 - 0.01 12 1.00 1.00 0.00 R 13 1.27 1.22 + 0.05 Root 14 0.79 0.82 - 0.03 15 0.93 0.90 + 0.03 16 1.09 1.03 + 0.06 17 0.74 0.74 0.00 18 0.79 0.82 - 0.03 Fig 1. Measurementsof crown and root lengthson a mandibular 19 0.93 0.90 - 0.03 first permanentmolar. The crown-body(CB) length was 20 1.09 1.03 + 0.06 determinedby drawingan occlusal line throughthe deepestpit Mean 0.95 -+ 0.15 0.97 -+ 0.13 -0.02 + 0.06 whichis parallelto anotherline joiningthe cusptips. Thelength -+ SD wasdetermined along a vertical axis drawnat right anglesto the occlusalline measuredfrom the deepestpit to the furcation. The mean difference between the two techniques is not statistically significant (P > 0.1) Similarly, the root ,~R)length wasdetermined a~ong the same * The panoramic technique used in this study is described in the vertical axis fromthe furcationto the root apex. text. PEDIATRIC DENTISTRY:SEPTEMBER, 1989 ~ VOLUME11, NUMBER3 215 selected, the panoramic radiograph is closely ratio of slightly less than 1:1 (i.e., < 1:1.1) wasconsidered equivalent to the long-cone periapical radiograph for to be within normal limits. the diagnosis of taurodontism using our biometric According to Shaw (1928), taurodontism occurs method. varying degrees that may be classified in increasing order of severity as hypotaurodontism, Statistical analysis mesotaurodontism, and hypertaurodontism. As these The Student’s t-test and the X2 test as appropriate, distinctions usually were determined subjectively were used for statistical analysis of the data. previously, we attempted an objective classification based on the CB:Rratio. Mandibular first permanent molars first were Results classified subjectively into these 3 groups by visual Prevalence of taurodontism in hypodontia and examination of panoramic radiographs. Mean CB:R control groups ratios were obtained for each putative group of Table 2 shows the prevalence of taurodontism of the taurodontism. From these preliminary measurements, mandibular first permanent molar in the hypodontia it was determined that CB:Rratios of the range 1.10 - group compared with the control group. As shown in 1.29 be classified as the hypotaurodont group, those in the table, taurodontism was diagnosed in 34.8% of the range 1.30 - 2.00 as the mesotaurodont group, and hypodontia patients compared with only 7.5% of those > 2.00 as the hypertaurodont group. Figure 2 control, the difference being statistically significant (P shows a diagrammatic representation of these classes of 0.001). taurodontism. The prevalence of taurodontism was further The prevalence of the 3 groups of taurodontism analyzed according to sex (Table 3).