2020, Number 4
Cephalometric analysis of the posterior bony space for third molar eruption
Full text
Language: English/Spanish [Versión en español]
References: 14
Page: 245-253
PDF size: 230.98 Kb.
ABSTRACT
Introduction: cephalometric analysis is a measurement method, which can be used to calculate the posterior bony space and third molar eruption. Objective: estimate the magnitude of modifications in the posterior bony space for the eruption of third molars (wisdom teeth), according to the stages of growth and development. Material and methods: an observational, descriptive, cross-sectional study was conducted in Santiago de Cuba, from November 2019 to February 2020. Three random samples were selected (n1 = 100 infants, n2 = 100 adolescents and n3 = 21 young people). The variables studied were age, third molar location and posterior bone space. Information was extracted from orthopantomography and summarised as mean and standard deviation (SD). Results: the averages of the posterior bony space for the eruption of third molars according to location, stage of growth and development, presented statistically significant differences for each of the dental hemiarchs (p < 0.001). An increase in posterior bony space was detected in relation to age (in all three groups), according to the different locations of third molars. Conclusions: the magnitude of changes in the posterior bony space for the eruption of third molars, according to the stages of growth and development, are considerable; with emphasis between infancy and adolescence. This phenomenon is probably due to the fact that these are the periods when significant changes occur in the growth of the maxilla and mandible.INTRODUCTION
Orthodontics is the science that studies facial and oral morphology in its different stages of growth and development, as well as the knowledge, prevention and correction of deviations from this morphology and normal function.1 This is how its complexity as a science is expressed, because it studies both morphology and function, taking into account the growth and post-growth of the individual. An essential aspect is that prior knowledge is necessary to be able to diagnose and achieve a correct treatment plan.2
The diagnostic assessment considers essential details such as the characteristics considered normal, according to the stage of growth and development in order to be able to identify alterations. The treatment to be followed will depend on the growth potential.
Growth is defined by Otaño3 as the increase in size (height and weight), resulting from of cell division, the increase in cell size and intercellular substance, the product of biological activity, manifestation of the functions of hypertrophy and hyperplasia of the body's tissues; it is also a quantitative change that can be measured in centimetres/year or grams/day.
Growth evolves in three main stages: childhood (from birth to 11 years in girls and to 12 or 13 years in boys), adolescence (from 11 to 18 years in girls and from 12 to 20 years in boys) and early adulthood (from 18 or 20 to 25 years, although it lasts approximately until 22 years of age).1-3
From an orthodontic point of view, cephalometry is one of the methods for assessing the growth of the various bony components of the skull and face,1 the term derives from the Greek kephale –head– and metron –measure–. Cephalometry is considered as the set of procedures followed for the measurement of the head, description and quantification of the structures involved in malocclusion (bones, teeth and soft tissues). In a true sense, it includes craniometry (from the Greek knanion –skull– and metron –measurement–) and the measurement of the face. Disciplines such as anthropometry, osteometry and somatometry are also involved.4
The stages of growth and development, together with cephalometry, are two aspects that are an indissoluble pair for decision making in the presence of third molars, which are the last teeth to erupt and form part of the current dental formula. Early detection and extraction of third molars is advisable to guarantee stability in treatment, as well as to avoid undesired movements due to the mesial thrust force during the tooth eruption and damage to neighboring teeth and tissues when there is insufficient space. It is therefore necessary to assess the posterior bony space available for their formation, development and eruption process.
In this regard, several authors5-10 have proposed cephalometric measurement methods related to the posterior bony space variable, which differ in the age range of the methodology. Only a few authors4,11,12 are inclined to identify changes by stage of growth and development.
There is a need to know whether such cephalometric methods and values described fit the ages (8-19 years) commonly treated in orthodontic practices in Cuba, which requires thorough investigation.
The existence of discrepancy between bone and tooth depends on the growth of the maxilla and mandible. Discrepancy is defined as the disproportion between the amount of bone and the sum of the mesiodistal diameters of the teeth.3 In order to estimate the magnitude of changes in the posterior bony space for the eruption of third molars, it was decided to investigate this issue according to the stages of growth and development.
MATERIAL AND METHODS
An observational, descriptive and cross-sectional study was conducted in Santiago de Cuba, from November 2019 to February 2020.
Three population groups were used: infants aged 8 to 10 years, adolescents aged 15 to 18 years and young people aged 21 years. The groups were defined by the following characteristics to ensure the quality of the measurements:
- 1. All teeth present according to their age, diagnosed with a Moyers class I.
- 2. Normal weight and without previous orthodontic treatment.
- 3. All four third molars with complete root formation, without deforming oral habits and/or neuromuscular dysfunctions (of the stomatognathic system).
- 4. Without dental anomalies of number (hypodontia or hyperdontia), volume (macrodontia or microdontia) and shape (conoid teeth).
Three random samples were selected from the Orthodontic Clinic of "José Martí Pérez" Polyclinic (n1 = 100 infants), from "Antonio Alomá Serrano" Senior High School (n2 = 100 adolescents) and from the health area of "Mártires del Moncada" Provincial Teaching Stomatology Clinic (n3 = 21 young people).
The variables studied were age, third molars and posterior bony space. For age, stages of growth were taken into account according to the classification of classical orthodontic authors,1,3 described in age groups: 8-10 years, 15-18 years and 21 years. For the location of the third molars, the classification described by the World Dental Federation (WDF) was used:13 1.8 upper right; 2.8 upper left; 3.8 lower left and 4.8 lower right. In the case of the posterior bony space, it was defined as the distance from the distal face of the second permanent molar to the Frankfort Y intersection with the pterygoid vertical for upper molars and the Xi or mandibular centroid for lower molars (Figure 1); the value was expressed in millimetres.4
Information on sample 1 (n1) was obtained through orthodontic medical records, where the initial orthopantomography was selected. While the other two samples were collected in community activities, where eligible individuals were selected by clinical examination and orthopantomography was taken. Measurements were performed manually with a millimetre ruler and a set square.
The ethical principles for medical research on human subjects, as promulgated in the World Medical Association declaration of Helsinki14 were followed, so that the radiological protection measures for the safe use of radiation and to ensure the protection of individuals and the environment established by the competent bodies4 were followed. Approval was also sought from the necessary institutions, as well as informed consent from the selected patients and their relatives.
Data Automation Strategy was followed using the statistical package IBM SPSS Statistics V21.0. The mean and standard deviation (SD) were used as summary statistics for the analysis of quantitative variables, with 95% confidence interval estimate. To identify differences between the means of the posterior spaces in the three samples, a one-way analysis of variance (ANOVA) was applied, with a significance level of α = 0.05. To estimate the predictive magnitude of the possible change in posterior bony space, a visual analysis of the possible linear relationship between this variable and age was initially performed by observing the scatter plot between the two variables. Then, a simple linear regression analysis was performed where:
Dependent variable: posterior space (in millimetres).
Independent variable: age (ranged from 8-21 years of age).
A linear regression line has an equation of the form, y = a + bx, where: y is the dependent variable, a is the intercept of the line, b is the slope of the line and x is the explanatory variable (independent variable).
In all cases, the probability of obtaining statistical differences beyond chance was specified (p-value < 0.001).
RESULTS
Table 1 summarises the averages of the posterior bony space for third molar eruption according to location and stage of growth and development. Statistically significant differences were observed in each stage of growth and development, according to the different locations of the third molars (p < 0.001). An increase in this dimension was detected with age, where the lowest value of 1.8 was 10.9 ± 6.8 mm in childhood, 19.9 ± 4.6 mm in adolescence and 25.7 ± 3.1 mm in early adulthood. For 4.8, which is the largest figure, 29.8 ± 5.2 mm was estimated in childhood, 42.3 ± 5.4 mm in adolescence and 44.7 ± 1.8 mm in early adulthood.
Table 2 shows that there is a direct and strong correlation between posterior bony space and age, with significant association, i.e. with increasing age so will the posterior bony space by 0.679, 0.666, 0.784 and 0.743 mm for 1.8, 2.8, 3.8 and 4.8, respectively.
Furthermore, a good adjustment was observed, since 45.8, 44.1, 61.4 and 54.9% of the changes in the posterior bony space dimensions for the respective 1.8, 2.8, 3.8 and 4.8 are explained by the increasing age of the examined individuals.
DISCUSSION
Orthodontists value and attach greater importance to diagnosis, because a thorough knowledge of the problem facilitates timely and appropriate treatment, even though clinical examination is considered more transcendent because it would avoid treating patients by cephalometric standards alone. There are several factors that must be taken into account to determine the most appropriate treatment plan, such as age, sex, race, developmental prognosis, facial biotype and severity of dentofacial anomalies. There are no exact formulas that can be invariably applied to the facial complex to indicate a specific treatment; therefore, in order to establish a complete individual diagnosis, the cephalometric findings must be related to the data from the other diagnostic aids used.
With regard to third molars, the posterior bony space obtained cephalometrically is an indispensable element for the prognostic assessment of their possible retention or, partial or complete eruption. Therefore, together with the analysis of other epidemiological variables, such as age, it is a very useful tool for prediction in orthodontics. In this context, the current research showed that as age increases, the posterior bony space for third molar eruption increases considerably. The result is associated with the fact that the ages of the study correspond to the active growth of the individual, where the maxilla and mandible undergo longitudinal changes.
The maxilla shows longitudinal and vertical growth at the same time, as described by Mayoral1 and Otaño.3 Regardless of the genetic influence upon the establishment of the basic facial pattern and the characteristics on which the external and internal environment operate, growth is achieved by downward and forward displacement through different mechanisms. Notable among these are: Sicher's sutural parallelism (growth of the frontomaxillary, temporozygomatic, zygomaticomaxillary and pterygopalatine sutures), the cartilaginous growth of the nasal septum or Scott's theory, and the functional matrices of Melvin Moss (apposition and resorption occurring during the displacement and remodelling of the orbits, nasal cavity and palate, and the influence of the perioral muscles).
The mandible growth is divided according to its two anatomical parts, 1) the body and 2) the ramus (composed by two rami). 1) In the body, grows by concomitant resorption along the anterior border of the rami when the mandible grows forward. 2) In the rami, the mandible grows by a) bone apposition, along the entire posterior border, and b) minor resorption along the anterior border.1-3
The space for the third molars, in the case of the upper molars, is provided by the apposition on the periosteal surface of the tuberosities. On the other hand, if they are the lower molars, the space is generated by resorption at the anterior border of the ramus (which increases the body longitudinally) and by apposition at the posterior border (which increases longitudinally the rami).4
Where this process is most notable is in childhood (where the greatest amount of growth of the individual occurs) and adolescence (where there is a major change in the growth of the maxilla and mandible, caused by "pubertal growth spurts").11 In contrast, it persists at a minimum in early adulthood where overall growth is relative, and that of the maxilla and mandible is reduced; and the individual reaches definitive height and proportions.1-3,12 This explains the successive increases in the spaces from 8 to 21 years of age in the current casuistry. In the same sense, our results show that the magnitude of changes in this space was much greater between the groups of individuals aged 8 to 10 (childhood, specifically the Middle childhood) and 15 to 18 years of age (adolescence, specifically between puberty and post-puberty according to sex); with increments of 9, 8, 11.5 and 12.5 mm for the respective upper right (1.8) and upper left (2.8), lower left (3.8) and lower right (4.8) bone spaces.
Quirós and Palma5 cite several international authors who have described the values of the posterior bony space, such as Henry and Morant (1936), Björk (1956), Ricketts (1972) and Turley (1974), who use profile teleradiography for the measurements, the disadvantage of which is the superimposition of both right and left sides. González4 cites Cuban authors such as Céspedes (2000), Fernández (2015), Pérez Cabrera (2012, 2017), who use Turley's method with orthopantomography. However, neither these values nor those described by previous authors can be contrasted with those of the current study. Only the work of González4,11,12 offers similar figures, a fact attributable to the use of the same measurement method and auxiliary aids for diagnosis, carried out in the same populations in Santiago de Cuba and in the same age groups.
The truth is that on many occasions a goal is set in a treatment plan in relation to third molars based on clinical experience and arch length discrepancy, when a cephalometric analysis could be carried out to predict whether the molar will erupt with or without difficulty. Furthermore, other studies4-6 indicate that third molars have considerable mesiodistal diameters that will prevent normal eruption in an insufficient space.
CONCLUSIONS
The magnitude of changes in the posterior bony space for third molar eruption according to the stages of growth and development are significant. It is most noticeable between infancy and adolescence, probably because these are the stages where major changes in maxillary and mandibular growth occur.
Evidence-based medicine plays an increasingly important role, leaving empiricism behind, and it is for this reason that the present work seeks to establish a precedent in the use and application of cephalometric analysis that is adjusted to the Cuban population.
REFERENCES
Fernández Pérez E, De Armas Gallegos LI, Batista González NM, Llanes Rodríguez M, Ferreiro Marín A. Análisis del espacio disponible para la erupción de los terceros molares mandibulares en radiografías panorámicas. Congreso Internacional Estomatología 2015; 2-6 Nov 2015; La Habana, Cuba. La Habana: Universidad de Ciencias Médicas de La Habana; 2015. Disponible en: http://www.estomatologia2015.sld.cu/index.php/estomatologia/nov2015/paper/view/210/103
Sánchez Salinas YM. Predicción del espacio para el tercer molar mediante la cefalometría de Ricketts. Huánuco. 2016 [Tesis]. Huánuco, Perú: Universidad de Huánuco; 2016. Disponible en: http://repositorio.udh.edu.pe/bitstream/handle/123456789/580/S%C3%81NCHEZ%20SALINAS%2C%20YANINA%20MARIAN%C3%89.pdf?sequence=1&isAllowed=y
González Espangler L, Duany López B, Romero García LI, Soto Cantero LA, Suárez Lorenzo J. Variación evolutiva del espacio óseo posterior para el brote de los terceros molares. Congreso Internacional Estomatología 2020; Nov 2020; La Habana, Cuba. La Habana: Universidad de Ciencias Médicas de La Habana; 2020. Disponible en: http://www.estomatologia2020.sld.cu/index.php/estomatologia/2020/paper/view/9/114
Asociación Médica Mundial. Declaración de Helsinki de la AMM- Principios éticos para la investigación en seres humanos. New York: AMM; 2017 [citado 20 Ene 2018]. Disponible en: https://www.wma.net/es/policies-post/declaracion-de-helsinki-de-la-amm-principios-eticos-para-las-investigaciones-medicas-en-seres-humanos/
AFFILIATIONS
1 Estomatóloga. Especialista de primer grado de Estomatología General Integral y Ortodoncia. Profesor asistente. Clínica Dental Contramaestre. Santiago de Cuba, Cuba. ORCID: https://orcid.org/0000-0001-9442-0046.
2 Estomatóloga. Doctora en Ciencias Estomatológicas. Especialista de primer y segundo grado en Ortodoncia. Profesor e investigador auxiliar. Facultad de Estomatología de la Universidad de Ciencias Médicas de Santiago de Cuba. Santiago de Cuba, Cuba. ORCID: https://orcid.org/0000-0002-2918-462X.
3 Médico. Especialista de primer y segundo grado en Bioestadística. Máster en Epidemiología y Salud Pública. Profesor Instructor e Investigador Auxiliar. Hospital Provincial "Saturnino Lora Torres", Universidad de Ciencias Médicas. Santiago de Cuba, Cuba. ORCID: https://orcid.org/0000-0002-3248-3110.
CORRESPONDENCE
Liuba González Espangler. E-mail: liuba.gonzalez@infomed.sld.cuReceived: Julio 2021. Accepted: Mayo 2022.