|Year : 2009 | Volume
| Issue : 2 | Page : 201-205
|The relationship between overjet size and dentoalveolar compensation
Nadia Lashin Soliman1, Mona Mahmoud El-Batran1, Ahmed Wael Abou-Zeid2, Azza Mohamed Sarry El-Din2, Moushira Erfan Zaki2
1 Department of Oral Medicine and Dental Surgery Research, National Research Centre, 33, El-Tahrir St., Dokki, Cairo, Egypt
2 Biological Anthropology National Research Centre, 33, El-Tahrir St., Dokki, Cairo, Egypt
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|Date of Submission||15-Dec-2007|
|Date of Decision||25-Apr-2008|
|Date of Acceptance||07-Jul-2008|
|Date of Web Publication||23-Jun-2009|
| Abstract|| |
Background : The purpose of this study was to investigate the effect of overjet size and the dento-alveolar compensation in subjects with normal class I molar relationship.
Materials and Methods: Lateral cephalometric head records of 59 Egyptian children (34 boys and 25 girls) aged 7.5 to 10.5 years with mean age of 8.69±0.73. All had normal class I type of occlusion. The sample was classified into four quartiles according to the overjet size and the cephalometric analysis was based on seven linear and eight angular measurements using a dental tracer programme.
Results: showed that, in spite of presence of high significant over jet size differences between the groups; there was no significant differences in all the studied parameters were found. Applying the least significant differences (LSD) test and coefficient correlations between the studied parameters clarifying that there was a significant differences in angular measurements (SN-AB, SN-Occl, I-I, I-ML, I-NB).
Conclusion: during transitional dentition there was a sufficient dento-alveolar adaptation to growth changes in the saggittal jaw relation ship to attain normal class I type of occlusion. This compensation is pronounced in angular parameters and clustered in the lower arches particularly in incisal area.
Keywords: Dento-alveolar, normal occlusion, overjet size
|How to cite this article:|
Soliman NL, El-Batran MM, Abou-Zeid AW, Sarry El-Din AM, Zaki ME. The relationship between overjet size and dentoalveolar compensation. Indian J Dent Res 2009;20:201-5
Studying the relationship during the growth process of maxillo-facial and dentoalveolar structures would be useful in enhancing the accuracy of prediction of maturational changes.
|How to cite this URL:|
Soliman NL, El-Batran MM, Abou-Zeid AW, Sarry El-Din AM, Zaki ME. The relationship between overjet size and dentoalveolar compensation. Indian J Dent Res [serial online] 2009 [cited 2019 Nov 13];20:201-5. Available from: http://www.ijdr.in/text.asp?2009/20/2/201/52900
Co-ordination of the development of the upper and lower arches is not always ideal. However for the achievement and maintenance of good normal relationship between upper and lower dental arches, certain mechanisms therefore, are needed to co-ordinate the eruption and position of the teeth relative to their basal bone. , This is what is called "dentoalveolar compensation" and can be defined as a system which attempts to maintain normal inter arch relationships.
Despite some variation in facial pattern during facial growth and development, normal occlusion can be attained and maintained primarily through dental compensation. 
In some variations of the skeletal morphology and saggittal jaw discrepancies, the compensatory inclination of the maxillary and mandibular incisors is very obvious and result in normal incisal relationship. ,
Quantitative evaluation of both the vertical and saggittal dentoalveolar adaptation in different over jet pattern may provide not only additional information for prediction of growth changes but also useful for planning treatment of subjects with different inter-arch relationships. So, the purpose of this study was to investigate the dentoalveolar compensation in subjects with normal class I molar occlusion (Angle classification) and the relationship of the overjet distance with this compensation and to determine the cephalometric parameters that quantitatively describe dental compensations.
| Materials and Methods|| |
A sample consists of lateral cephalometric records of 59 school children; 34 boys and 25 girls aged 7.5 to 10.5 years with a mean age of 8.69.years. They all had normal class I type of occlusion; no one had any orthodontic treatment in the past, no extensive caries or fillings, no missed teeth and no severe attrition.
Overjet was measured as the distance between the incisal tip of maxillary central incisor and the labial surface of the mandibular central incisor on a line parallel to the occlusal plane. According to a previous study on Egyptian children with mixed dentition by one of the authors  the normal overjet distance ranged from 0.05 to 6.35 mm with no significant sex differences. The sample was therefore pooled and the overjet was classified according to its size into four quartiles:
- The first quartile ranged from 0.0-1.8 mm (Group I).
- The second quartile ranged from 1.9-2.9 mm (Group II).
- The third quartile ranged from 3.0-3.8 mm (Group III).
- The last quartile ranged from 3.9-6.4 mm (Group IV).Analysis of lateral cephalograms was based on seven linear and eight angular measurements by using a "Dental Tracer Program".
The various linear measurements on the lateral cephalogram were measured using dental tracer program as follows: [Figure 1] and [Figure 2]
- Maxillary anterior alveolar and basal height (MxAABH) is the distance between the midpoint of the alveolar meatus of the maxillary central incisor and the intersection point of the long axis of this tooth with the palatal line.
- Maxillary anterior depth (MxAD) is the distance between points A and A'. A is the most palatal point on the outer surface of the labial plate of the alveolar process of the maxillae. From point A, a line was drawn parallel to the palatal line intersecting the dorsal contour of the maxillary alveolar bone (A').
- Maxillary posterior alveolar and basal height (MxPABH) are the perpendicular distance from the midpoint of the alveolar meatus of the maxillary first molar and the palatal line.
- Mandibular anterior alveolar and basal height (MdAABH) is the perpendicular distance between the midpoint of the alveolar meatus of the mandibular central incisor and the mandibular line.
- Mandibular posterior alveolar and basal height (MdPABH) is the perpendicular distance between the midpoint of the alveolar meatus of the mandibular first molar and the mandibular line.
- The horizontal distance between the labial surface of the maxillary central incisor and N-A line (UI-NA).
- The horizontal distance between the labial surface of the mandibular central incisor and N-B line (LI-NB). B is the most dorsal point on the outer surface of the labial plate of the alveolar process of the mandible.
The various angular measurements on the lateral cephalogram were measured using dental tracer program as follows [Figure 3]:
- The angle between the long axes of the maxillary and mandibular central incisors (angle 1).
- The angle between the long axis of the maxillary central incisor and S-N line (angle 2).
- The angle between the long axis of the mandibular central and the S-N line (angle 3).
- The angle between the long axis of maxillary central incisor and the N-A line (angle 4).
- The angle between the long axis of the mandibular central incisor and the N-B line (angle 5).
- The angle between the long axis of mandibular central incisor and the mandibular line (angle 6).
- The angle between the S-N and A-B lines (angle 7).
- The angle between the S-N and the occlusal lines (angle 8).
To determine the method errors, lateral cephalometric head films from randomly selected cephalograms were retraced and remeasured by the same operator with a two weeks interval.
Dahlberg's formula was used to calculate the method error: Method error= √∑d 2 /2n where d is the difference between two measurements of a pair and n is the number of subjects. The method error didn't exceed 0.43mm. (Range 0.34-0.43mm) or 0.51 degrees (range 0.30-0.51degrees).
Differences between the overjet groups and between sexes were assessed by means of analysis of variance.
The least significant difference test was applied. Also, correlation coefficients between overjet and other studied variables were calculated. In addition means and standard deviations were computed for all measurements in each overjet group separately. All calculations and computations were done by the statistical package for social sciences (SPSS for Windows, version 10). SPSS, Inc., Chicago, Illinois, USA.
| Results|| |
Means and Standard deviation values of the chronological ages and overjet measurements for each group and F-values are presented in [Table 1]. There was no significant age or gender differences among the overjet groups however, statistically significant size differences among the overjet groups (P < 0.05) were found.
Descriptive statistics including means and standard deviations for all studied variables "linear and angular" are determined separately for each overjet group are presented in [Table 2].
To determine the significant differences between the overjet groups for studied parameters, the least significant differences (LSD) test was applied. Almost in all linear measurements, no significant differences were detected between the overjet groups and only, the results denoting significant differences are given in [Table 3]. It is obvious that the most significant difference between the overjet groups is concentrated at angle 7 which is between SN and AB, and at angle 5 between the second and fourth overjet groups and also at angle 6 between the second and third groups and between the second and fourth groups (P < 0.05).
[Table 4] illustrates the correlations coefficients between the overjet and the other studied variables as a whole and in each sex, separately. It is observed that the highest correlation was found between the overjet and SN-AB followed by the angle between the long axis of lower incisor and mandibular plane also, between the long axis of lower incisor and the NB line.
A significant coefficient of correlation was found between the overjet and angle 1, angle 6 and angle 8 in girls while in boys the significant relation was observed with angle 7.
Finally, the results of variance analysis are shown in [Table 5]. It could be seen that angle 6 and angle 7 are the only angular measurements showing statistical significant differences among the overjet groups. Also, it is clear that no significant sex differences could be demonstrated in this table. In addition the only observed significant interaction between gender and overjet groups was found in angle 4.
| Discussion|| |
Although, facial bones don't ordinary grow as isolated, unrelated, independent unit, and the growing face changes in proportion as well as in size, there is certain common profile characters and proportionate relationship sustained and the basis of morphological form or pattern variation is thereby created. Even in person with good esthetics and good functional balance. ,
Overjet or horizontal overlap is undergoing significant changes during primary and transitional dentition and it is a reflection of the anteroposterior relationship of maxillary and mandibular bases. 
It is important to note that, in addition to the presence of morphological compensatory dento-alveolar changes produced by soft tissue and occlusal forces, the lower incisor inclination is strongly regulated by the sagittal jaw relationship and it plays an important role for achievement and maintenance of normal incisors relationships under different jaw relationships. ,,,,
Present study confirms the previous findings and indicates a sufficient incisal adaptation to growth changes in the sagittal jaw relationship to attain normal class I occlusal relationship particularly during transitional dentition, and manifested itself by the absence of significant differences between the studied parameters in spite of presence of high significant overjet size differences [Table 1] and [Table 2].
For evaluation of vertical and sagittal dento-alveolar adaptation in relation to different normal overjet pattern, the least significant difference test was applied in this study [Table 3] and the results indicating that there is a statistical significant concentration in the angular parameters between the overjet groups and the most pronounced compensatory changes were clustered to the lower arch where the mandibular incisors were more effective in providing dento-alveolar compensation in normal class I relationships than maxillary ones, these findings supporting those by Enlow et al.,  who pointed out in counterpart analysis that the cant of the occlusal plane compensates skeletal jaws discrepancies to attain a class one occlusal relationship. However, these findings are confirmed by Bibby,  Janson et al.,  and Ceylan et al,  who reported that in cases of large skeletal relationship variations and discrepancies between jaws, compensatory inclination of the incisors were more clearly reflected by proclination of the lower incisors in class I and II subjects where in class III they were upright or retroclined. On the other hand, Ishikawa et al.,  reported that the upper incisors incline more labially (proclination) and the lower incisors more lingually (retroclination) in negative overjet cases.
Compensatory angulations of the occlusal plane was statistically substantiated with SN-AB in this study which is in agreement with Ishikawa et al.,  who suggested that the most appropriate parameter for describing the quantitative dental compensation would achieved by measuring SN-AB angle as a skeletal measure where each degree of change in this angle monitored by large variation in the relationship between both maxillary and mandibular denture bases.
Considering correlation analysis, the results of the present study [Table 4] and [Table 5] agree with Ceylan et al.,  where there was statistically significant relationship between the overjet size and the axial inclination of upper incisor with NA and lower incisor with NB. Although these correlation coefficients are relatively low which might be due to limitation of the studied sample to class I angle classification with subsequent normal overjet variations they were considered as dental measures for dental compensation.
Further investigations are necessary to provide additional information for establishing the limits in sagittal jaw relationships where normal class I occlusion is obtained in natural growth via spontaneous dento-alveolar compensation.
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Nadia Lashin Soliman
Department of Oral Medicine and Dental Surgery Research, National Research Centre, 33, El-Tahrir St., Dokki, Cairo
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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