Appraising Lower Incisor to Mandibular Plane Angle in Different Facial and Sympheal Morphology

AUTHORS

Sidra Butt 1 , * , Imtiaz Ahmed 1

1 Department of Orthodontics, Dr Ishrat Ul Ebad Khan Institute of Oral Health Sciences, DUHS, Sindh, Pakistan

How to Cite: Butt S, Ahmed I. Appraising Lower Incisor to Mandibular Plane Angle in Different Facial and Sympheal Morphology, Iran J Ortho. 2015 ; 10(1):e4861. doi: 10.17795/ijo-4861.

ARTICLE INFORMATION

Iranian Journal of Orthodontics: 10 (1); e4861
Published Online: June 13, 2015
Article Type: Research Article
Received: April 11, 2015
Revised: May 16, 2015
Accepted: June 6, 2015
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Abstract

Background: In orthodontic diagnosis and treatment planning assessment of an individual’s facial skeletal pattern in vertical, sagittal and transverse direction is prevalent. Dental compensation is the reverse of skeletal disharmony.

Objectives: This study has correlated the position of mandibular incisors inclination with different facial types and with the mandibular symphyseal morphology.

Materials and Methods: The sample consisted of 100 Pakistani patients of two different age groups i.e. adolescents up to 12 years and audlts up to 22 years on which R–angle, Li–MP, B–MP, Li–MP, symphyseal width (W) and depth (D) were measured.

Results: No correlation was found between Li–MP and R–angle, B–MP, Li–MP, and W except with the D i.e. symphyseal depth.

Conclusions: No significant association observed between lower incisor inclination, different facial types, and symphyseal morphology except with the depth of the symphysis. Slight correlation of differential jaw growth and dental changes with age are coincidental events with no relationship.

Keywords

Lower Incisor Inclination R-Angle Symphyseal Morphology

Copyright © 2015, Iranian Journal of Orthodontics.This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

1. Background

It is observable that the changes with growth and that facial growth continue throughout a person’s life. In orthodontic diagnosis and treatment planning assessment of an individual's facial skeletal pattern in vertical, sagittal and transverse direction is prevalent. Numerous angular and linear measurements of different researchers have been derived to categories the patients with vertical skeletal discrepancies. Many of them are existing with shortcomings. Dental compensation is the reverse of skeletal disharmony. Dento-alveolar compensations are spontaneous changes in incisor position and inclination trying to attain a good occlusion anteriorly and an acceptable anterior guidance in cases of sagittal and to some extent, of vertical skeletal discordant. Changes in the inclination of the lower incisors to compensate for the skeletal discrepancy might cause surface remodeling of mandibular symphysis, affecting its morphology (1). Symphyseal shape and size can be affected by factors such as genetic and ethnicity, inclination of the lower incisors and facial type. Therefore, in this study we have correlated the lower incisor inclination, facial type, and mandibular symphyseal morphology to evaluate any reciprocity between them. The stability of orthodontic treatment results can be bettered if the orthodontist respects the morphology and functional characteristics of each individual.

2. Objectives

This study has correlated the position of mandibular incisors inclination with different facial types and with the mandibular symphyseal morphology.

3. Materials and Methods

The study conducted at orthodontics department of Dow international dental college Ojha campus. 100 pretreatment lateral cephalograms of 25 male adolescents, 25 adult males, 25 female adolescents and of 25 adult women were evaluated by using four angular measurements. i.e. maxillary-mandibular plane angle, gonial angle, lower incisor to mandibular plane angle and R angle along with four linear symphyseal measurements i.e. symphyseal depth and width, perpendicular distances between lower incisor–mandibular plane and point B–mandibular plane as shown in the Table 1 and Figure 1 All tracings were performed by a single researcher. Patients with gross facial dysplasias due to any cause presence of any supplemental, missing, or malformed tooth, anterior and or posterior crossbites and with periodontal disease were in excluded criteria.

Table 1. Angular and Linear Parameters
Variables Description
R-angle Anterior angle between CO-N axis and CO-Me axis
Ll-MPIncisor to mandibular plane angle (IMPA)
H1Perpendicular distance between point B to mandibular plane
H2Perpendicular distance between lower incisor edge to mandibular plane
DSymphyseal depth between point B and posterior tangent to symphysis
WSymphyseal width between anterior and posterior tangent to symphysis
Figure 1. Parameters Delineated
Parameters Delineated

1, R angle; 2, LI–MP (IMPA); a,H2; b, H1; c, D; d, W

4. Results

Data were entered and evaluated on SPSS 16. Mean and standard deviations of the parameters analyzed are given in Table 2. (Descriptive Statistics).

Table 2. Descriptive Statistics
12 Years Male22 Years Male12 Years Female22 Years Female
MeanSDMeanSDMeanSDMeanSD
LI-MP94.849.4595.446.8796.128.5097.367.97
R-angle74.085.1274.123.4572.245.0472.445.29
B–MP (H1)20.082.3723.282.3718.922.2121.242.55
Li–MP (H2)40.043.3445.603.0038.283.0240.483.56
Symphyseal width (W)15.321.4517.361.8214.462.1415.561.60
Symphyseal depth (D)8.801.869.601.478.481.318.961.54

Spearman ranks correlation analysis was performed on data to see the relationship of R, IMPA, H1, H2, W and D with Age group and gender. Correlation matrix shows that, age group has positive significant association with H1 (r = 0.48, P = 0.00), H2 (r = 0.46, P = 0.00), and W (r = 0.39, P = 0.00), but negatively associated with gonial angle (r = - 0.30, P = 0.002). Gender has negative significant correlation with R (r = - 0.21, P = 0.028), H1 (r = - 0.29, P = 0.003), H2 (r= -0.38, P = 0.00) and W (r = -0.31, P = 0.02). It was found that IMPA is statistically significantly but negatively correlated with the vertical pattern of the patient i.e. R-angle, Table 3 (Spearman’s correlation values with Ll-MP).

Table 3. Spearman’s Correlation Values With Ll-MP
AgeGenderR <H1H2WD
Incisor mandibular plane angle0.0420.112-0.1690.1380.0420.1010.231a
Correlation coefficient sign.0.6780.2650.0920.1720.6820.3160.021
N 100100100100100100100

aCorrelation is significant at the 0.01 level (2 tailed).

The correlation analysis revealed highly significant age dependency for all absolute symphyseal measurements, Table 4 (Spearman’s Correlation values with age).

Table 4. Spearman’s Correlation Values With Agea
Age Correlation Coefficient SignH1H2WD
0.4820.4620.3940.190
0.0000.0000.0590.000
N 100100100100

aCorrelation is significant at the 0.01 level (2 tailed).

5. Discussion

In this study, we have used maxillary-mandibular plane angle (MMA) and a new parameter R-angle to assess vertical skeletal disharmony. In general, mandibular incisors play a more important role in compensations than maxillary incisors. For different vertical or anteroposterior relations of the apical bases, nature provides different compensatory inclinations of maxillary and mandibular incisors to ensure occlusion harmony. Lower Incisor Inclination can be determined through cephalometrics calculated as IMPA 90 + 5 degree, R angle below 70.50 indicate Low angle cases, between 70.5 - 75.50 indicate average angle cases and above 75.50 indicate high angle cases (2). This study showed mean values of LI–MP at 12 years, 95.48 degree and at 22 years 96.4 degree, that shows slight increase in incisors inclination with age while mean values of LI–MP in males 95.1 degree and in females 96.7 degree which shows higher inclinations in females. R-angle showed no significant difference of mean values between gender and different age groups, overall mean value calculated was 73 + 2 degree. Mandibular symphysis serves as a reference anatomical landmark for esthetics and beauty of the face in general and of the lower part in particular (3, 4). As the lower face height increases, upper and lower anterior teeth may continue their eruption in an attempt to maintain a positive overbite, bringing their alveolar bony support with them, resulting in an increase in total symphyseal length. (3, 5, 6). In this study for H1, D and W, an age-depended slight increase can be observed for both sexes with an increase can be detected for H2, more pronounced in males. Several other studies (7-9) supports these obtained results.

5.1. Conclusion

No significant association observed between lower incisor inclination, different facial types, and symphyseal morphology except with the depth of the symphysis. Slight correlation of differential jaw growth and dental changes with age are coincidental events with no relationship.

References

  • 1.

    Yu Q, Pan XG, Ji GP, Shen G. The association between lower incisal inclination and morphology of the supporting alveolar Bone — A cone‐beam CT study. Int J Oral Sci. 2009; 1(4) : 217 -23 [DOI]

  • 2.

    Rizwan M, Mascarenhas R. A new parameter for assessing vertical skeletal discrepancies: The R angle. Revista Latinoamericana de Ortodoncia y Odontopediatría. 2013; : 2 -8

  • 3.

    Buschang PH, Julien K, Sachdeva R, Demirjian A. Childhood and pubertal growth changes of the human symphysis. Angle Orthod. 1992; 62(3) : 203 -10

  • 4.

    Hoenig JF. Sliding osteotomy genioplasty for facial aesthetic balance: 10 years of experience. Aesthet Plast Surg. 2007; 31(4) : 384 -91 [DOI]

  • 5.

    Jiang T, Chakravarty MM, Aleong R, Leonard G, Perron M, Pike GB, et al. Automated analysis of craniofacial morphology using magnetic resonance images. PLoS ONE. 2011; 6(5)[DOI]

  • 6.

    Shapiro PA. Mandibular dental arch form and dimension. Am J Orthod. 1974; 66(1) : 58 -70 [DOI]

  • 7.

    Little RM, Riedel RA, Stein A. Mandibular arch length increase during the mixed dentition: Postretention evaluation of stability and relapse. Am J Orthod. 1990; 97(5) : 393 -404 [DOI]

  • 8.

    Noroozi H, Nik TH, Saeeda R. The dental arch form revisited. Angle Orthod. 2001; 71(5) : 386 -9 [DOI][PubMed]

  • 9.

    Schulhof RJ, Allen RW, Walters RD, Dreskin M. The mandibular dental arch: Part I, Lower incisor position. Angle Orthod. 1977; 47(4) : 280 -7 [DOI][PubMed]

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