2020, Number 4
Maxillary height according to facial pattern
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ABSTRACT
Introduction: The growth of facial bones is a process that varies according to racial, dental and genetic factors, and this growth may cause alterations in the facial pattern. Objective: determine whether there is a correlation between the increase or decrease in the anterior and posterior maxillary height of the maxillary bone and the facial pattern in individuals from 18 to 45 years of age. Material and methods: observational, descriptive, cross-sectional study with a correlational approach. The population consisted of 500 lateral cephalometric radiographs in digital format. Only 241 radiographs met the selection criteria, which were traced to finally select 160 at random. They were classified into four groups according to facial pattern: low, medium-low, medium-high and high. Then, the height of the maxilla was measured in the anterior and posterior sector. The variables studied were: age, sex, facial pattern, anterior maxillary height and posterior maxillary height. The AutoCAD® V2020 programme was used to measure the variables and parametric tests were used for the statistical analysis with a confidence level of 95% (p < 0.05). Results: of the 160 radiographs analysed, patient age had no correlation with facial pattern (p > 0.05). Sex and anterior maxillary height presented a significant correlation in men, with high facial pattern with a value of p = 0.000, and their degree of correlation was positive and low (rho Spearman = 0.243). Posterior facial height of the maxilla showed no significant difference (p = 0.145). Conclusions: in men, high facial patterns have a greater anterior maxillary height. Sexual dimorphism is evident in male individuals with a high angle of the facial pattern.INTRODUCTION
In orthodontics the growth and direction of the maxillae bones are considered in diagnosis and treatment planning.1 The growth of the maxillae is a process that varies according to racial, dental and genetic factors.2 The maxilla is an essential structure, as changes in its shape affect the normal skull growth and dental structures causing alterations in the facial pattern.3 By means of cephalometrics it is possible to study the bony structures to identify direction, growth and position. Anatomical points are identified and joined by lines to form angles.
According to Cecil Steiner,4 one of the most important determinations that can be made from cephalometric tracing is the degree of deformity or malformation of the mandible, using the sella (S) nasion (N) - gonion (Go) - gnation (Gn) angle. The SN-GoGn angle represents the direction of vertical or horizontal opening of the mandible. This opening indicates a vertical growth pattern which determines the facial pattern, and varies between individuals during treatment. Changes in the height of the maxillary bone can alter this opening, causing the angle to be convergent or divergent.4-6
There are tracings to determine the maxillary height, and the mandibular divergence angle.3 According to Beckmann,7 maxillary anterior alveolar and basal height, is obtained by the distance between the midpoint of the alveolar meatus of the upper central incisor and the point of inter-section between the palatal plane and the long axis of the upper central incisor (MxAABH); and the maxillary posterior alveolar and basal height is measured by the perpendicular distance between the midpoint of the alveolar meatus of the first molar and the palatal plane (MxPABH).7-11
According to Steiner, the mandibular divergence angle is formed by the SN plane, which corresponds to the base of the cranium, and the Go Gn plane, which forms the mandibular plane (MP). The latter angle allows us to obtain a diagnosis of the type of vertical facial pattern of individuals.4-6
The facial pattern may vary due to the diversity of ethnic groups or races, together with the genotypic traits that an individual may present. In the case of the population of Cuenca, Ecuador, the facial phenotypes are mesoprosopic, reported as the predominant, followed by euryprosopic and finally leptoprosopic.12 Since clinicians try to achieve morphological and functional harmony in the stomatognathic system, the aim is to identify how this is associated with the shape of the upper maxilla.
The purpose of this study is to determine whether there is a correlation between increased or decreased maxillary height and different facial patterns.
MATERIAL AND METHODS
The research design is observational, descriptive, cross-sectional, documentary and with a correlational approach. The population consisted of 500 lateral cephalometric radiographs in digital format, taken with NewTom (GiANO HR) panoramic device in the natural position of the head, during the year 2019. The radiographs were from individuals who attended a radiology centre located in the city of Cuenca, Ecuador.
The inclusion criteria were radiographs of individuals aged 18 to 45 years, of both sexes, with clear bony structures and the presence of permanent dental organs, with the exception of third molars. Exclusion criteria were all radiographs of individuals: with previous orthodontic treatment, undergoing orthognathic surgery and with craniofacial anomalies. The population consisted of 500 lateral cephalometric radiographs in digital format, of which only 241 met the selection criteria. The radiographs were then traced and 160 were randomly selected and classified into four groups of 40, according to facial pattern into low, medium-low, medium-high and high. Once classified, the height of the maxilla was measured in the anterior and posterior sector. The variables studied were: age, sex, and two variables comprising a) two linear parameters, and b) an angular measurement, with cephalometric points to evaluate the relationship of the maxilla to the facial pattern.
For the angular parameter, the following was considered: sella-nasion gonion-gnation angle, which measures the convergence or divergence between the cranial base and the mandible. It is determined by tracing the sella-nasion plane and the mandibular plane,4-6 and categorised into four groups: low angle = PM/SN ≤ 27o, medium low angle = PM/SN 28o < 32o, medium high angle = PM/SN 32o ≤ 37o, and high angle = PM/SN >37o (Figure 1A).13
The maxillary height was obtained with the distance in millimetres formed by the plane of the maxillary anterior alveolar and basal height, which is obtained by the distance between the midpoint of the alveolar meatus of the upper central incisor and the point of inter-section between the palatal plane and the long axis of the upper central incisor (MxAABH); and the maxillary posterior alveolar and basal height is measured by the perpendicular distance between the midpoint of the alveolar meatus of the first molar and the palatal plane (MxPABH) (Figure 1B).7-11
In order to obtain the data, 10 digital lateral cephalometric radiographs were observed daily on a laptop computer with the AutoCAD® V2020 programme. The observer was in a separate and dark room, with a quiet environment, to guarantee the precision in the localisation of the points, in an examination schedule from 9-12 hours and from 15-18 hours.
The data was collected using an observation sheet in Excel, where data such as sex, age, facial divergence angle (expressed in degrees) and both anterior and posterior maxilla heights (expressed in millimetres) were recorded.
Further to determine the intra-observer margin of error, the chief investigator repeated the measurement of the angular and linear variables on 20% (n = 32) of the radiographs, which were randomly selected and corresponded to eight radiographs from each facial group.
The data processing was done in the statistical software SPSS® V25.0 for both statistical calculation and graphs; the tables, on the other hand, were done in Microsoft Excel® 2018. Descriptive statistics were used to calculate the mean and standard deviation values of each cephalometric variable under the parameters of each group.
Parametric tests were used following a normal distribution. For differences between age and sex, the Mann-Whitney U test was used; for multiple comparisons of facial pattern with anterior and posterior maxillary height, analysis of variance (ANOVA) and Tuckey's post-hoc test were used. To establish the averages of anterior and posterior maxillary height with the different skeletal patterns, the rho Spearman correlation coefficient was used with a value of 5% (p < 0.05).
RESULTS
After evaluating the 160 digital lateral cephalometric radiographs of individuals between 18 and 45 years of age, it was determined that 51.25% (n = 82) were female and 48.75% (n = 78) were male. The results of the descriptive measures according to age, sex and the different skeletal patterns showed no significant difference p > 0.05 (Table 1).
The results of the means of the anterior maxillary height in relation to the facial pattern showed significant differences with a value of p = 0.000; the posterior maxillary height exhibited a value of p = 0.145. The comparison between groups showed significant differences for the anterior maxillary height in relation to the low to high facial pattern (p = 0.007), medium to low to high (p = 0.009), and medium to high (p = 0.01) and the degree of correlation was low and positive (rho Spearman = 0.243). These results indicate that an individual with a vertical skeletal pattern will present a greater anterior maxillary height and had no relationship with posterior maxillary height; while there was a significant difference between the facial types (p = 0.000) (Table 2).
The mean anterior maxillary height in the different facial patterns was significant only for men (p = 0.001), comparison between the groups indicated differences between the facial types low with high (p = 0.001), medium low with high (p = 0.023), and medium high with high (p = 0.001). While posterior maxillary height was not significant according to sex (Table 3). Figure 2 shows the mean anterior maxillary height in men with high facial pattern.
DISCUSSION
The purpose of orthodontics is to balance the facial profile when establishing a treatment plan, which is why the relationship between balance and the aesthetics of the facial profile has been studied.14 The maxilla, as it presents different sizes and shapes, must be associated with the dental organs and the soft tissues that cover it,15 and it is also necessary to know the relationship that the different vertical changes of the maxilla may have.16
The relationship between the anterior and posterior height of the maxillary bone and the different facial patterns was studied, and the results show that there is no significant difference between age and sex according to facial pattern. This is in agreement with the study by Toledo et al.,17 who found that there is no significant difference between age and sex in an Ecuadorian population. Age is not a factor that can determine a type of facial pattern, these are determined by sex, ethnicity and time. Similarly, Sodawala et al.,13 in their study in an Indian population, found that age was not statistically significant for sex in the four biotype groups and within each of the four groups.
Altemus18 found that the age group 18-25 years is a period of stable growth in the development of the head and face. Roy11 further stated that growth is slower and the permanent dentition does not show variability, as a constant facial pattern is established and is subject to less change.
The relationship of MxAABH and MxPABH with the different facial patterns was found to be significant only for anterior maxillary height and has no significant difference with posterior maxillary height. This indicates that the higher the MxAABH the greater the SN-MP angle, agreeing with Roy,11 who shows that MxAABH and MxPABH were significant for hyperdivergent facial types over other types in an Indian population. Also the results of comparison between groups revealed that they have significant difference (Spearman's rho = 0.243), which means that the higher the vertical facial pattern, the higher the maxillary anterior height. Solow19 explains that this relationship suggests a compensatory mechanism that, as the anterior part of the maxilla enlarges, hyperdivergence occurs. Schudy20 points out that the growth and shape of the maxilla is a factor in achieving morphological and functional harmony as long as there is a tendency for the maxillae to hyperdiverge. In his study he demonstrated that the maxilla is a dentoalveolar parameter for determining different vertical skeletal dysplasias; its height and inclination are of importance with regard to the stability of any planned changes. Similarly, MxPABH also had a higher value in the hyperdivergent group. Isaacson et al21 reported that the amount of maxillary posterior alveolar development decreases as the SN-MP angle decreases. According to Schendel,16 excessive posterior dentoalveolar heights were a common feature of long face syndrome. Opdebeeck15 his studies suggest that when individuals have SN-MP angle with hypodivergence, short face syndrome is present.
There are no similar local studies that compare the study variables, so it is proposed to perform further research on this subject.
Sexual dimorphism between facial types has been found in previous studies,7-11 so it was necessary to segregate the sample in this study according to sex in order to maintain the homogeneity of the sample.
MxAABH and MxPABH showed significant differences for men, such results differ with Roy11 and Ceylan,8 where anterior and posterior maxillary height were not significant for the sex variable, i.e. sexual dimorphism was not evident in maxillary and mandibular morphology. The study by Bucchi22 supports the results of our research, who points out that the height and width of the maxilla and mandible are variables of sexual dimorphism. Maxillary morphology varies by sex in size and shape because men tend to have greater facial heights. Maxillary and mandibular height are greater in men than in women, without increasing proportionally to facial height.
CONCLUSIONS
High facial patterns have a greater anterior maxillary height. The maxillary height was higher in men with high facial pattern and there is no significant difference between facial pattern and posterior jaw height.
REFERENCES
Serantes M, Jiménez M, Calderón M. Morfología craneofacial y su relación con la forma y ancho del arco dentario maxilar en estudiantes entre 13 y 16 años de la ciudad de Cuenca. Revista Latinoamericana Ortodoncia y Odontopediatría. 2014. Disponible en: https://www.ortodoncia.ws/publicaciones/2014/art-11/
AFFILIATIONS
1 Odontólogo. Carrera de Odontología de la Universidad Católica de Cuenca, Unidad Académica de Salud y Bienestar. Ecuador.
2 Docente. Carrera de Odontología de la Universidad Católica de Cuenca, Unidad Académica de Salud y Bienestar. Ecuador.
CORRESPONDENCE
Paúl Efraín Medina Siguenza. E-mail: paul_11toh@hotmail.comReceived: Mayo 2021. Accepted: Septiembre 2021.