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                               MORPHOMETRY OF THE MANDIBLE OF GERMAN SHEPH
     Vol. 58 (1) 2003
                                                                             H. Alpak

                         Department of Anatomy, Faculty of Veterinary Medicine, University of Istanbul, 34854, Avcilar


     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.


  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

 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

    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).


 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

    Basal length-    7          7,42        0,027      8,53       0,0290       2,311 *

    Basal length-    7          4,33        0,037      6,15       0,0329       2,756 *

 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


  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.


  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.



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