|Year : 2021 | Volume
| Issue : 1 | Page : 26-35
Relationship between dental arch width and vertical facial morphology in multiethnic assamese adults
Mahasweta Dasgupta, Bhabotosh Kumar Roy, Gita Rani Hazarika Bora, Trailokya Bharali
Department of Orthodontics and Dentofacial Orthopedics, Regional Dental College, Guwahati, Assam, India
|Date of Submission||10-Dec-2020|
|Date of Acceptance||11-Feb-2021|
|Date of Web Publication||12-Jul-2021|
Dr. Mahasweta Dasgupta
Regional Dental College, Guwahati - 781 022, Assam
Source of Support: None, Conflict of Interest: None
Aim: The aim of this study was to evaluate the relationship between dental arch width and vertical facial morphology in the Assamese population and also to investigate the differences in dental arch width dimensions between male and female subjects. Materials and Methods: Ninety untreated adults aged from 18 to 45 years, divided into three test groups, Group-I: MP-SN angle: low <27°, Group-II: average 27–37°, and Group-III: high >37°. Measurements of Intercanine width, first and second interpremolar width, first intermolar width, tooth-size arch material discrepancy were performed on maxiillary and mandibular cast. Results: The results indicate a high correlation with Pearson's correlation coefficient values (r) from intercanine width to interpremolar width, medium correlation for intermolar width. The relationship was found to be an inverse, as SN-MP angle increased, the dental arch widths decreased. Arch width varies as low SN-MP > average SN-MP > high SN-MP angle. The dental arch widths of males were found to be wider than females. Conclusion: The relationship of dental arch width and vertical facial pattern is determined by the steepness of the mandibular plane in the Assamese adult population. Since dental arch width is associated with gender, vertical facial morphology, and population groups, it is suggested to use individualized archwires according to each patient's pretreatment arch form and widths.
Keywords: Assamese population, dental arch width, gender variation in arch width, vertical facial morphology
|How to cite this article:|
Dasgupta M, Roy BK, Bora GR, Bharali T. Relationship between dental arch width and vertical facial morphology in multiethnic assamese adults. Indian J Oral Health Res 2021;7:26-35
|How to cite this URL:|
Dasgupta M, Roy BK, Bora GR, Bharali T. Relationship between dental arch width and vertical facial morphology in multiethnic assamese adults. Indian J Oral Health Res [serial online] 2021 [cited 2021 Sep 16];7:26-35. Available from: https://www.ijohr.org/text.asp?2021/7/1/26/321118
| Introduction|| |
The discipline of orthodontics is a multifaceted one. Orthodontics is no longer the practice of just fitting the teeth together, but instead a specialty for prettification of the entire facial skeleton by harmonizing the whole dentition to the rest of the structures in the skull.
As every individual is different so are their needs. Thus, it is of paramount importance that every patient receives a fully customized treatment plan designed to meet the individual needs of every patient.
One of the primary goals of any orthodontic treatment is to create an individualized dental arch that is ideal for the patient. The achievement of a stable, functional, and esthetic arch has long been the prime objective of orthodontic treatment. Nowadays, preformed archwires are routinely used by many orthodontists regardless of the facial type, facial proportions, and gender of the patients. However, using individualized archwires according to each patient's pretreatment arch form and width is suggested during orthodontic treatment.,,
A key aspect in the achievement of these goals is the identification of a suitable arch form to be used in the treatment of each case. It has been well established that the preservation of the original arch form and size of orthodontically treated patients, plays an important role in assuring long-term stability after orthodontic treatment.
Facial morphology is unique to every individual in the world. A well-balanced face has its good proportions in all three dimensions of space, i.e., transverse, sagittal, and vertical. The vertical proportions of the face are important in determining the esthetics and harmony of the face. The facial pattern of an individual can be taken into consideration as an important factor that aids in the treatment selection and protocol because facial types influence the anchorage system, growth prediction of maxillofacial structures, and goal of orthodontic treatment.
Three basic types of facial morphology exist: short, average, and long. Those with long face have excessive vertical facial growth which is usually associated with an anterior open bite, increased sellanasion–mandibular plane (SNMP) angle, increased gonial angle, and increased maxillary/mandibular plane angle. The short face types have reduced vertical growth that is accompanied by a deep overbite, reduced facial heights, and reduced SNMP angle. Between the two types lies the average face.
It is generally accepted among orthodontists that a relationship exists between vertical facial morphology and the cant of the mandibular plane. Schudy, advocated the use of the anterior cranial base (SN) as the reference line to determine the steepness of the mandibular plane (MP). A subject with a high MP–SN angle (steep MP) tends to have a longer face, and one with a low MP–SN angle (flat MP) often has a shorter face.
A long-face individual usually has narrower transverse dimensions (dolichofacial) and a short-face individual has wider transverse dimensions (brachyfacial), according to Ricketts et al., Enlow and Hans, and Wagner and Chung.
A number of investigators noticed the variation of the craniofacial morphology in different ethnic groups. Different racial groups must be treated according to their own individual characteristics.
The population of Assam is a broad racial intermixture of Mongolian, Dravidians, Tibeto-Burmans, Aryo-Dravidians, Mongol-Dravidian, Indo-Burmese, Indo-Iranian, Aryan origin, etc., Assamese is the principal language of the state.
The relationship between vertical facial morphology and arch width has been found for different ethnic and racial growth previously. Most investigators have concluded that there are significant differences between the diverse ethnic and racial groups. All the studies indicate that normal measurement for one group should not be considered normal for every other race or ethnic group.
The objectives of this study were to investigate the correlation between dental arch width and the vertical facial pattern and also to investigate the differences in dental arch dimensions between male and female subjects in the Assamese population.
| Materials and Methods|| |
The radiation exposure caused by each lateral cephalograph is 2–3 μSv which is within the normal exposure limit of general people, i.e., 1 mSv per year (according to guidelines of the International Commission on Radiological Protection).
A combination of cast analysis and cephalometric analysis was undertaken as depicted below.
Collection of samples
The present study was conducted on 90 Assamese subjects randomly selected from the patients seeking orthodontic treatment in Assam.
The following inclusion and exclusion criteria were considered for the selection of the samples.
- The subjects were of Assamese ethnicity, residing in Assam, which was confirmed from family history
- Permanent dentition completely erupted except the third molars
- Subjects without any orthodontic treatment.
- Any anomaly in tooth size, number, and shape
- Congenital defects or deformed teeth.
- Edentulous spaces
- History of trauma
- Significant cuspal wear
- Extensive restorations or prosthetics
- Anterior and posterior crossbites
- Severe crowding (>9 mm) or spacing (>9 mm).
Materials and equipment used for cast analysis
- Irreversible hydrocolloid impression material (alginate)
- Dental stone (Type III)
- Upper and lower impression trays
- Rubber bowl, plaster spatula
- Upper and lower rubber base formers
- Model trimmer
- A digital caliper accurate to 0.01 mm
- Brass wire
- Measurement scale.
Upper and lower impressions of the dental arches were made with alginate impression material and poured immediately to avoid distortion. The impressions were poured in dental stone type III.
Materials for cephalometric analysis
Computed radiography (CR) system – Regius Model 190 and Drypro-793.(Konika) Dental X-ray Unit with Cephalometry.
- CR cassette–Advapex Panoramic System 8“ × 10”
- X-ray illuminator or a viewbox on a tracing table with soft light
- 0.003 mm acetate matt tracing paper
- Geometry box set containing protractor, set squares, scale, 0.3 mm 3 H pencil, eraser, etc.
- The planes used in the study are:
- SN plane
It is a line connecting the sella point to the nasion point that represents the anterior cranial base.
S (Sella) and N (Nasion) were easily discernable in a lateral cephalogram and can be located with relatively higher accuracy.
It can be located in the mid-sagittal plane of the head, and move minimally with any deviation of the head from the true profile position.
- Mandibular plane
The mandibular plane was drawn from menton (Me) to the inferior border of the angular area of the mandible (Schudy, 1965).
- The angles used in the study are
- SN-MP angle: The angle formed by joining the mandibular plane to the anterior cranial base (SN plane)
- ANB angle: The angle formed by joining point A and point B to the nasion.
The head films were traced on A4 size acetate matt paper using a 3Hb pencil.
Three orientation crosses were marked on the cephalogram; two within the cranium and one on the cervical vertebrae with a sharp-pointed tool. These orientation crosses were transferred to the tracing paper. The sample's name, age, and serial number were written on the tracing paper for future reference.
All essential landmarks were identified and traced. The measurement error was determined by re-measuring the cephalometric parameters [Figure 1].
The mean, standard deviation, minimum, and maximum values of each measurement were tabulated and statistical evaluation was done.
Impression was made in alginate for both maxillary and mandibular arches and poured immediately with dental stone type III to avoid distortion. A base mounting aligner was used to orient the bases parallel to the occlusal plane while mounting.
Tooth size - arch length discrepancy was calculated by first determining the arch length available. The arch length required was then subtracted from this value. The arch length required was equal to the sum of the mesiodistal widths of each individual tooth from the second premolar to the second premolar, measured from the contact points [Figure 2].
|Figure 2: Measurements for arch length available by summing the distances from the mesial contact point of the left first molar to the distal contact point of the left lateral incisor, the distal contact point of the left lateral incisor to the mesial contact point of the left central incisor, the mesial contact point of the left central incisor to the distal contact point of the right lateral incisor, and the distal contact point of the right lateral incisor to the mesial contact point of the r|
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- Ninety untreated adults aged from 18 to 45 years
- Subjects will be divided into three test groups based on the findings obtained as follows:
- Group-I: MP– SN angle: Low <27°
- Group-II: Average 27°–37°
- Group-III: High >37°
These values represent 1 standard deviation from the average MP–SN angle reported by Riedel.
For each subject, MP– SN angle was measured. The mandibular plane was drawn from menton (Me) to the inferior border of the angular area of the mandible (Schudy, 1964).
Dental cast measurements were performed using a digital caliper accurate to 0.01 mm. The following maxillary and mandibular dimensions were measured:
- Intercanine width (buccal cusp tip and widest labial aspect)
- First and second interpremolar widths (buccal cusp tip and widest labial aspect)
- First intermolar widths (mesiobuccal cusp, central fossa, widest buccal, and narrowest lingual aspect)
- Tooth size-Arch length discrepancy [Figure 3].
|Figure 3: Arch width measurements of the cusp, fossa, most labial, and most lingual on the dental cast|
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Pearson correlation coefficient is a measure of the linear correlation between two variables X and Y. The correlation coefficient ranges from −1 to 1. A value of 1 implies that a linear equation describes the relationship between X and Y perfectly, with all data points lying on a line for which Y increases as X increases. A value of −1 implies that all data points lie on a line for which Y decreases as X increases. A value of 0 implies that there is no linear correlation between the variables. The closer the value of r gets to zero, the greater the variation the data points are around the line of best fit.
- High correlation: 0.5 to 1.0 or −0.5 to 1.0.
- Medium correlation: 0.3 to 0.5 or −0.3 to 0.5
- Low correlation: 0.1 to 0.3 or −0.1 to −0.3.
| Results|| |
Pearson's correlation coefficients (R) were calculated for each of the 10 maxillary and mandibular arch width parameters. The observed correlations were tested for significance at 5% level of significance. The coefficient of determination, i.e., (R2) for each of the 10 parameters was also calculated. Regression analysis was also done to establish a linear relationship between arch width and SN-MP angle through an estimating equation taking SN-MP as dependent variable (Y) and arch width as independent variable (X).
The results indicated a high correlation with Pearson's correlation coefficient values (r) of above-0.5 for measurements from intercanine width to interpremolar width, whereas the intermolar width values show medium correlation for all angular and linear measurements. In the mandibular arch, most values fall within the range of high correlation, except the intermolar width at most buccal aspect which showed medium correlation.
The scatter diagram shows the best fit for values of intercanine width in the maxillary arch.
The values in the negative range indicate an inverse relationship between SN-MP angle and dental arch width, as SN-MP angle increases ∼ dental arch width decreases.
Regression equations have been obtained for predicting the angular measurement of SN-MP from arch width of the Assamese population at different points with the standard error of estimate.
Y = 145.921 − 3.397X (±5.378)
- Where Y stands for SN-MP angle
- X for intercanine width (at cusp tip) [Table 1].
|Table 1: The correlation of maxillary dental arch width with respect to sella nasion-mandibular plane angle|
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The mean maxillary and mandibular dental arch width for all the 10 parameters was computed along with their standard deviations with respect to the three facial patterns – low SN-MP, average SN-MP, and high SN-MP. The differences in the mean values of the three facial pattern groups were tested for statistical significance through an analysis of variance test at 5% level of significance. The mean values of arch width calculated for low, average, and high SN-MP groups show that low SN-MP has the highest arch width in all 10 parameters, then the average has intermediate values, and high SN-MP groups have the lowest arch width [Figure 4], [Figure 5] and [Table 2].
|Table 2: Comparison of different arch widths in different vertical facial pattern in the maxillary arch|
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|Figure 4: Comparison among groups and relationship with vertical facial pattern maxillary arch|
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|Figure 5: Comparison among groups and relationship with vertical facial pattern mandibular arch|
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These observations are in accordance with the study done on the Caucasian population, Pakistani population, North Indian, and South Indian population all of which show a significant correlation between vertical facial morphology and dental arch width.
The difference in the mean values between males and females was tested for statistical significance using Independent samples t-test at 5% significance. The male and female arch widths vary considerably, with male arch width greater than females. The difference in their mean values is statistically significant for all arch width values, except the second premolar buccal cusp and intermolar width at the mesiobuccal cusp in the maxillary arch [Figure 6].
Mandibular arch showed significant values in all measurements except first and second premolar width most buccal aspect [Figure 7] and [Table 3].
|Table 3: The correlation of maxillary dental arch width with respect to gender|
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The values of intermolar width lingual aspect in maxillary and intercanine width in the mandibular arch are highly significant (P < 0.001) tested by independent t-test at 5% significance.
This observation is in accordance with the observations in Caucasians, where the arch width measurements were larger for males compared to females. Gross et al. observed that boys displayed larger arch width than girls and given that this is due to the fact that boys tend to be physically larger than girls. An increase in arch width during growth was found more in males than females and this can be a reason for males having a broader arch than females. The results in this study were similar to Nasby et al., evaluation. They demonstrated narrower intermolar widths in high-angled children. Wei evaluated posteroanterior cephalograms of Chinese adults and noted gender differences in maxillary and mandibular intercanine widths.
| Discussion|| |
- Skeletal Class I (as determined by ANB angle) subjects were examined because more dental compensation is expected in skeletal Class II or III subjects, which might affect the values of the relationship between vertical facial morphology and dental arch widths
- The present study investigated untreated adult males and females separately. It has previously been demonstrated that males and females exhibit different skeletal facial dimensions, (Chung and Wong; Chung and Mongiovi), as well as differences in maxillary and mandibular arch widths (Christie)
- Unfortunately, many of the earlier studies that examined arch width and mandibular plane angle combined the genders.,,, In addition, the present sample was limited to nongrowing, adult individuals, unlike many of the previous investigations that included only growing children, (Eroz; Chung,,)
- The musculature has been considered as the possible link in this close relationship between the transverse dimension and vertical facial morphology
- Strong masticatory musculature is often associated with a brachyfacial pattern (short face). This muscular hyperfunction causes an increased mechanical loading of the jaws. This, in turn, may cause an introduction of sutural growth and bone apposition which then results in increased transverse growth of the jaws and bone bases for the dental arches
- van Spronsen et al. found that long-faced subjects have significantly smaller masseter and medial pterygoid muscles than normal subjects.
- Satiroğlu et al. ultrasonographically measured masseter muscle thickness. They found that individuals with thick masseter had a vertically shorter facial pattern and individuals with thin masseter have a long face. Their results showed a significant association between vertical facial patterns and masseter muscle thickness. These results are in agreement with previous studies done by Weis et al., Kiliaridis S, Kälebo
- Dental arch width is certainly a multifactorial phenomenon. The data from this study showed an inverse relationship between MP-SN angle and dental arch widths with a strong correlation. It seems the MP-SN angle might be only one of the contributing factors. Hence, the prediction of dental arch width is generalized and can be influenced by other factors.
Ethnic variation in arch width
- Comparing the arch width of Assamese populations with the observations of Forster et al. in the Caucasian population, the interarch widths of the Assamese population were wider than the Caucasian population
- The arch dimension in the South Indian population is less than the Assamese population in both maxillary and mandibular arches
- The arch width in the Assamese population is greater than the Pakistani population
- The intercanine width (30.62 mm) and intermolar width (53.51 mm) at most buccal aspect in the mandibular arch, in the Assamese population, are significantly larger in dimension in comparison to the Caucasian sample of intercanine width (29.01 mm) and intermolar width (49.17 mm) and Japanese samples (29.90 mm, 50.71 mm, respectively)
- The arch dimension in Assamese in mandibular intercanine and intermolar width is larger than Egyptian (28.5 mm, 45.7 mm, respectively) and Israeli population (29.37 mm, 49.71 mm, respectively)
- Arch width of Assamese population is slightly greater than Korean population arch dimension in mandibular intercanine area (30.7mm) and less in intermolar area (51.6mm)
- The variation of arch widths between Assamese and other population and males and females highlights the variation of arch widths according to race, ethnicity, and gender and also using customized archwires according to pretreatment arch form and width for every patient during orthodontic treatment.
| Conclusion|| |
Within the parameters of the study, the following conclusions are made from the statistical analysis:
- The relationship between dental arch width and vertical facial pattern is determined by the steepness of mandibular plane in untreated multiethnic Assamese adult population
- The relationship was found to be an inverse relation in both males and females of untreated multiethnic Assamese adults, as SN-MP angle increased, the dental arch widths tended to decrease
- A generalized prediction was done for the dental arch widths with a given SN-MP, one value known, other could be predicted by the regression equation
- The dental arch widths of males are found to be wider than females among untreated multiethnic Assamese adult adults
- Since dental arch width is associated with gender, vertical facial morphology, and population groups, during orthodontic treatment, it is suggested to use individualized archwires according to each patient's pretreatment arch form and widths.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3]