ISRAEL JOURNAL OF VETERINARY MEDICINE MORPHOMETRY OF THE MANDIBLE OF GERMAN SHEPH (ALSATIAN) PUPPIES USING COMPUTED TOMOGRAPHIC Vol. 58 (1) 2003 H. Alpak Department of Anatomy, Faculty of Veterinary Medicine, University of Istanbul, 34854, Avcilar Abstract A group of 14 male German shepherd puppies were divided into two treatment groups. The first c days old puppies and the second of 120 days old. Scanograms of the sagittal plane were made anaesthesia. Osteometric measurements were taken on the scanograms, each demonstrating the maxim In order to reveal the morphometric changes in the mandibula, the inferior angles formed between measurement points on the scanograms were calculated. Regarding the angles, a rise in angle A and falls in B and C occured as puppies grew older. The diff angle A of the first and second groups was statistically significant (p< 0.001). The correlation betwe and B and B and C were highly negative. In conclusion, the angles at the infradental points of two age German shepherd puppies have been examined and attempts were made to clarify the position and cou of the mandibulae of these animals. Introduction Malocclusion is defined as an abnormality in the apposition of the teeth. This is a state that makes it difficult for the animal to grasp and chew its food. The most important types of malocclusion in some canine breeds are mandibular prognathism and brachygnathism. In the former, the mandibula is longer than the maxilla and is observed to project forward (1). In the latter, the mandibula is shorter than the upper jaw. Maxillar protrusion often results in the formation of an abnormally short mandibula (2). This is an anomaly widely encountered Collies and Dachshunds (2), and justifies detailed morphological and anatomical analyses of the mandibula in the evaluation of these types of malocclusion. To examine the correlation between the structural morphology of the mandibula and mastication types, various comparative studies have been performed on many species of mammals (3). Normal and pathological bony structures have also been examined radiologically and morphologically (4). However, there are relatively few studies carried out on individual dog breeds. Computed Tomography (CT), presents images of high resolution and several surveys on canine brain anatomy have been performed (5,6). This technique has also enabled researchers to measure more accurately on the cranial volume of these animals (7,8). Morphometric analysis of the mandibula of 45 and 100 day old German shepherds puppies whose development is dolichocephalic (9,10), showed these ages of dogs did not have malocclusion of either type (11). This CT study entails to measuring direct osteometry and different measurement points have been determined on CT scanograms. Osteometric measurements and examination of the angles between the points were measured resulting in the analysis of malocclusion in German shepherd puppies. Materials and Methods A group of 14 male German shepherd puppies were included in this study. The puppies were divided into two groups of seven according to their age: the 100 days old and 120 days old. Scanograms of the sagittal plane were obtained under general anaesthesia (8). Following the determination of measurement points (11,12), osteometric measurements were made, each demonstrating the maximum mandibula (Figure 1). Fig. 1. Measurements of the mandibula. Id. Infradental; Bp. Basal point; Pc. Condylar point; 1. Basal length-2; 2. Basal length-1; 3. Maximum length of mandibula The following are the points between which osteometric measurements were taken: Infradentale (Id): the highest point of the gum between the two central incisors of the lower jaw, Basal point (Bp): the point above the basal edge of mandibula level with caudal edge of M1 alveolus, Condylar point (Pc): aboral edge of condylar process. The osteometric measurements taken were: maximum length of mandibula: distance from condylar point (Pc) to infradentale (Id), Basal length-1: distance between infradentale (Id) and the basal point (Bp), Basal length-2: distance from the basal point (Bp) to condylar point (Pc). In order to reveal the morphometric changes in the mandibula, the following angles formed between the osteometric measurement points on the scanograms were calculated. Angle A: angle between the maximum length of mandibula and basal length-1, Angle B: angle between basal length-1 and basal length-2, Angle C: angle between basal length-2 and the maximum length of mandibula. The osteometric and angular measurements allowed examination of the changes that occur with age. The mean and standard deviations (SD) of these measurements were calculated and analysed by t-test for significance. The correlation coefficients between the angles were also calculated and analysed statistically (13). Results The osteometric measurements, their mean and SD are given in Table 1, and were observed to increase with age. Table 1. Measurements and angles of the mandibula First group Second group Measuremen n Mean SD Mean SD t ts (cm) Maximum 7 10,5 0,031 12,99 0,1100 1,734NS length of mandibula Basal length- 7 7,42 0,027 8,53 0,0290 2,311 * 1 Basal length- 7 4,33 0,037 6,15 0,0329 2,756 * 2 Angles Angle A 7 19,00 0,354 23,10 0,418 8,213** Angle B 7 126,80 1,605 124,60 1,851 0,040NS Angle C 7 34,20 1,351 32,30 1,565 0,037NS * P < 0.05, ** p < 0.001, NS: Not significant A rise in angle A and falls in B and C were recorded, as puppies grew older. The difference between angles A of the first and second groups was statistically significant (p< 0.001). However, angles B and C did not correlate significantly. The correlation between the angles of A and B, and B and C were highly negative. Angles A and C, on the other hand, correlated positively. The correlation coefficients had a statistical significance (Table 2). Table 2. Correlation analysis of the angles First group Second group Angle A Angle B Angle C Angle A -0,7711NS 0,6543NS Angle B -0,7427NS -0,9860NS Angle C 0,6109NS -0,9839NS NS:Not significant Discussion If malocclusion is to be inspected properly, it is essential that the morphometry of the mandibula be thoroughly appreciated (11). Nevertheless, there are relatively few studies on malocclusion in dogs developing from puppyhood onwards. Mandibular morphometry was analysed in German shepherd puppies up to the age of 100 days, and the mean total length of mandibula in both was shown to be 91.17?11.297 mm (11). In this study, the mean of the same length was found to be 10.50?0.03 cm in the 100 days old group and 12.99?0.11 cm in the 120 days old one. The difference in age between the two groups explains the difference in mean mandibular length. The basal edge of mandibula in dogs is curve-shape. That explains why two other measurements were taken to reveal the variations occurring with age of this curve. The point above the basal edge level with the caudal edge of M1 alveolus was taken as the basis of this measurement. The next step was the calculation of the angles taking shape as the puppies grew. Of these, A increased with age, while angles B and C decreased. The front part of the mandibula smoothly bending upwards and the condylar process lengthening backwards demonstrated that the rear curve was diminishing. The difference between angle A of the first and second groups was statistically significant (p< 0.001). The correlation coefficients of the angles were in support of the below findings: The increase in the curve of the front part of the mandibula was in accordance with the growth of angle A and the decrease in the curve of the rear part of mandibula was in accordance with the decrease in angles B and C. Apart from the above, there was a highly negative correlation between angles A and B, which was taken as confirmation of the increase in the curve of the front part. The angle formed by the front edge of margo ventralis is greater in male German shepherd puppies than in females (p< 0.05) (11). In conclusion, the angles at their infradental points of two age groups of male German shepherd puppies have been examined, the position and course of the curve in the mandibulae of these animals were correlated. The data obtained from CT may serve as a reference in further studies on German shepherd puppies and in the evaluation of malocclusion in all types of breeds. Acknowledgements The authors would like to thank Assoc. Prof. Dr.Vedat Onar and Prof. Dr. K.Oya Kahvecioglu, Dr.Vedat Çebi (MD, Head of Bakırköy Radyotom & Radyomar Center) and Mr.Ibrahim Ekilen (Veterinary Intern Doctor) for their excellent technical assistance, and Mr. Cüneyt Bademcioglu for his invaluable contribution to the hard task of translating this article. LINKS TO OTHER ARTICLES IN THIS ISSUE References 1. Blood, D.C. and Studdert, V.P.: Bailliere’s Comprehensive Veterinary Dictionary. Bailliere Tindall. 1st Published. London, 1988. 2. Evans, H.E. and Christensen, G.C.: Miller’s Anatomy of the Dog. Saunders Co., Philadelphia, London, 1993. 3. Denoix, J.M.: Comparative anatomy of the mandible. Functional aspects. Bull. Assoc. Anat. (Nancy), 67: 395-419, 1983. 4. Eckerdal, O. and Waller, E.: Comparative and morphologic investigation of normal and genuine pathological bone structure of the mandbile. I. Literature review and description of a sectioning method. Swed. Dent. J. 6: 181-187, 1982. 5. Fike, J.R., Lecouteur, R.A. and Cann, C.E.: Anatomy of the canine brain using high resolution computed tomography. Vet. Radiol. 22: 236-243, 1981. 6. Kaufman, H.H., Cohen, G., Glass, T.F., Huchton, J.D., Pruessner, J.L., Ostrow, P.T., Andia-Waltenbaugh, A.M. and Dujovny, M.: Computed tomographic atlas of the dog brain. J. Comput. Tomogr. 4: 529-537, 1981. 7. Regedon, S., Franco, A., Garin, J.M., Robina, A. and Lignereux, Y.: Computerized Tomographic determination of the cranial volume of the dog applied to racial and sexual differentiation. Acta Anat. 142: 347-350, 1991. 8. Robina, A., Regedon, S., Guillen, M.T. and Lignereux, Y.: Utilization of computerized Tomography for the determination of the volume of the cranial cavity of the Galgo Hound. Acta Anat. 140: 108-111, 1991. 9. Brehm, H., Loeffler, K. and Komeyli, H.: Skull shape in the dog. Anat. Histol. Embryol. 14: 324-331, 1985. 10. Onar, V.: A morphometric study on the skull of the German shepherd dog (Alsatian). Anat. Histol. Embryol. 28: 253-256, 1999. 11. Onar, V., Kahvecioglu, O., Mutus, R. and Alpak, H.: Morphometric analysis of the mandible in German shepherd dogs. Turk. J. Vet. Anim. Sci. Suppl.2, 23: 329- 334, 1999. 12. Driesch, A von den.: A Guide to the Measurement of Animal Bones from Archaeological Sites. Peabody Museum Bulletin 1., Harward University, Massachusetts, 1976. 13.Evrim, M. and Günes, H.: Biometry. Veterinary Faculty Ed. No.81, Istanbul University, Istanbul, 1998. 1.