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Measurement of the Width, Length, Height and Volume of the Hard Palate Using A 3D Evaluation Method

Corresponding Author: Dr. Silvana Kairalla, MSc in Dentistry, Meth-odist University of São Paulo, Brazil. Email: sil_allegrini@hotmail.com

Received Date: Oct 01, 2019; Accepted Date: Oct 11, 2019; Published Date: Oct 14, 2019Publisher: Scholars Insight Online PublishersCitation: Kairalla . Measurement of the Width, Length, Height and Volume of the Hard Palate Using A 3D Evaluation Method. Ann Dent Oral Biol. 2019; 1:105.Copyright: ©2019 Kairalla S. This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unre-stricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objectives: The objectives of this study were to determine the width, length, height and volume of the hard palate using a computer program and to establish the relationship between the measurements found and the facial types and patterns of the analysed individuals.Methods: The sample consisted of 70 Caucasian individuals (28 men and 42 women) with a minimum age of 15.0 years and a maximum age of 21.3 years (mean of 16.4 ± 1.3 years) with normal natural occlusion. The maxillary arch models were three-dimensionally digitised, and the images were exported to Delcam PowerSHAPE™ 2010 software. Close points were selected in the gingival region and cervically on the lingual surface of the maxillary teeth. The facial patterns and types and the width, length, height and volume of the palate were compared using analysis of covariance (ANCOVA) with age as the covariate and sex as the independent variable. In all statistical tests, a significance level of 5% (p < 0.05) was adopted.Results: The width, length, height and volume of the hard palate were measured using three-dimensional (3D) technology, and the differences were not significant when the facial patterns and facial types of individuals were compared.Conclusions: The 3D method allowed measurement of the width, length, height and volume of the hard palate and showed that for the maxillary arch, these measurements were similar among the mesofacial, dolichofacial and brachyfacial facial types and between individuals with type I and II skeletal patterns in the sample analysed.

Keywords: Dental arches; Anatomy; Hard palate; Lingual orthodontics

that the lingual appliance could cause pain. However, studies showed that the adaptation to the lingual appliance is similar to that of the buccal orthodontic technique [3,4], and patient reports showed that some individuals could adapt more quickly than others. This factor may be related to the size of the dental arches and to the posture of the tongue and its positioning and relationship with the dental arches and, in particular, the hard palate. This adaptation may also be related to the type of lingual bracket, how the lingual appliance is mounted and, lastly, to the shape of the arch wire used.

Appliance mounting using the lingual technique can be performed in a simple or complex manner [5]. The location of the bracket on the lingual surface can be centralised on the lingual surface or positioned more cervically [6]. Bonding of the lingual brackets in a more cervical position is performed to reduce the existing step between the lingual surface (concave) of the canine and first premolar (convex), and in this case, it is necessary to use a lingual straight wire.

Although this strategy allows reduction of the typical insets and offsets of the lingual surfaces of the dental arches, which are concave and convex, unlike the flat vestibular surfaces, an individualised laboratory configuration is necessary. This configuration can sometimes hinder orthodontic mechanics in certain movements and cause gingival inflammation because the resin pads (amount of composite resin) required to compensate for the distance between the lingual surface and the bracket base on these irregular surfaces will be greater in areas where larger compensations are necessary [7-10]. In these cases, the brackets may advance into the space occupied by the tongue, resulting in possible patient discomfort [10].

Figures 1 and 2 show two examples of lingual brackets, one of which was mounted with a resin pad, and the other was mounted without a pad (Figure 2). A bracket base that is close to the lingual surface will

IntroductionWhen examining an orthodontic technique, it is important to

determine the mechanics and consequences of its applicability; thus, it is necessary to relate the anatomical structures of the stomatognathic system to the appliances used in the lingual orthodontic technique.

The first study describing the use of lingual brackets positioned on the inner surfaces of the teeth and a mushroom-shaped arch wire for tooth correction was performed by K. Fujita1 (1979). At the end of the 1970s, this technique was also being developed in the United States [2].

The fact that the brackets were in direct contact with the tongue muscle drew the attention of professionals and patients, raising the fear

Silvana KairallaMSc in Dentistry, Methodist University of São Paulo, Brazil

Research Article

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Figure 1: Adenta® bracket with indirect mounting, with a thickness 5.5 mm (measured by a compass).

Figure 2: Forestadent® bracket with direct mounting, with a thickness of 2.5 mm (measured by a compass).

models using current resources such as a 3D scanner and the computer program Delcam PowerSHAPE™ 2010 (Birmingham, UK) and to verify the existence of a possible relationship between facial types and facial patterns.

Materials and MethodsThis was an observational analytical study of medical records

approved by the Ethics Committee of the School of Health 0000. The study protocol was approved by the Research Ethics Committee under number 0388/2016.

The sample consisted of 70 Caucasian Brazilian individuals (28 men and 42 women) with a minimum age of 15.0 years and a maximum age of 21.3 years (mean of 16.4 ± 1.3 years). The facial patterns and facial types of the sample were classified using lateral teleradiography and extraoral photographs in anterior and profile smiling views and by subjective facial analysis [23]. Of the total, 43 individuals were classified as having facial pattern I, and 27 individuals had facial pattern II. The facial type analysis indicated 35 mesofacial, 28 brachyfacial and 7 dolichofacial individuals.

Regarding the maxillary and mandibular dental models of the sample, the inclusion criteria were individuals with normal natural occlusion, i.e., without odontogenic abnormalities; complete dental eruption, except for the third molars; all permanent teeth in occlusion and the presence of four occlusion keys [24]. The four keys considered were Class I molar relationship, crown angulation, crown inclination (considering the long axis of the teeth) and the curve of Spee (flat or smooth); rotations of up to 3 degrees and diastemas with spacing up to 0.5 mm were accepted. The exclusion criteria were absence of odontogenic abnormalities, incomplete dental eruption and presence of third molars.

The 70 plaster models of the maxillae were digitised using a dw5-140 3D scanner (Dental Wings, Montreal, Quebec, Canada) at the Hospital da Face (São Paulo, São Paulo, Brazil). After obtaining the images of the scanned models, the images were read using Delcam PowerSHAPE™ software (2010, Birmingham, UK)

The x,y and z axes were transferred to the maxillary model using a straight line starting at a point between the maxillary central incisors and ending near the distal surface of the second molars, passing exactly over the y axis, as shown in Figure 3.

Then, the models could be rotated on the computer screen so that the lingual surfaces could be observed in an anterior view and the operator could define and locate exactly where the points should be placed. The points were placed using a tool in the Delcam PowerSHAPE™

have a lower profile, and the appliance will be less invasive into the space occupied by the tongue; therefore, the patient will have better adaptation with regard to speech and comfort [12].

These factors explain the debate regarding the ideal space for the tongue. The tongue is a muscle that, during swallowing and articulatory and chewing movements, is in direct contact with the hard palate and the lingual surface of the teeth [13].

Thus, some researchers have analysed the width, length, height and volume of the hard palate because it has an intimate relationship with the tongue [14], not only during speech and chewing movements but also during swallowing and resting, when the tongue remains supported on the structures of the hard palate and lingual surface of the maxillary teeth for a long period of time.

Thus, Three-Dimensional (3D) digitised models have enabled examination1 of the dimensions of the hard palate [15-17]. However, other research tools are necessary for analysis of tongue volume [18]. In addition, the hard palate, as part of the fixed scaffold of the skull, may be related to the facial pattern and facial type of individuals, which has led some researchers to investigate this correlation [19-22].

Due to the lack of research on this subject, this study aims to determine the width, length, height and volume of the palate in sample

Figure 3: Digitised maxilla model with the coordinates and plane defined on the y-axis.

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2010 software. During the study, all measurements maintained the same proportionality in all models of the sample, demonstrating the accuracy of the method.

The points were established on the gingival surface, approximately 1 mm from the cervical horizontal line of the gingiva on the lingual surface of the maxillary teeth, from the second molar on the left side to the second molar on the right side. The location of the points was required to coincide with the continuation of the long axis of all maxillary anterior and posterior teeth.

After the points were established, they were joined in the anterior and posterior region to delimit the space where the tongue could be positioned comfortably at rest on the structures of the hard palate (Figure 4).

Delcam PowerSHAPE™ 2010 software tools were used to determine the width, length, height and volume of the palate. First, the program selected and marked the area of the hard palate to be analysed with a rectangle (Figure 5).

Next, the program cut the selected area. This jagged area is shown in the lateral and basal views in Figures 6 and 7. Subsequently, these measurements were tabulated in EXCEL (Microsoft™, Redmond, Washington, USA) for statistical analysis.

ResultsData are described using the mean and standard deviation.

A Shapiro-Wilk test was used to determine whether the data

were normally distributed. All measurements met the normality assumption. To compare facial patterns and facial types with the width (Table 1 and 2), length, height and volume of the palate, analysis of covariance (ANCOVA) was used, with age as the covariate and sex as the independent variable. In all statistical tests, a significance level of 5% (p < 0.05) was adopted [25].

DiscussionAlthough the lingual technique is extremely attractive from the

aesthetic point of view because it is considered “invisible”, as it does not show the orthodontic appliance, and the brackets are positioned on the lingual surface of the teeth, it is sometimes disregarded by the proposed users for other reasons. These reasons include fear of tongue pain or of developing changes in speech, especially for patients in certain professions, such as speakers and those with careers in the arts.

Studies show that patients adapt to lingual appliances within 3 weeks [3,4,12], which would not make the technique contraindicated [3]. However, a study indicated that the type of bracket used has a direct relationship with the patient’s adaptation to speech [12], comfort and painful symptoms. Furthermore, a higher bracket profile, either due to its metallic structure (bracket base) or combined with resin to form a pad in individual bracket mountings, results in greater discomfort of the user [11]. This is demonstrated in Figures 1 and 2, which show a clinical example of lingual brackets that were assembled using a resin pad and another example where a thickness of approximately 5.5 mm between the lingual surface and the bracket body was measured with a compass (Figure 1). Figure 2 shows the configuration with another bracket, in this case performed directly on the enamel surface, called

Figure 4: Model with the area delimited after joining the chosen points.

Figure 5: Area selected by the Delcam PowerSHAPE™ 2010 program.

Figure 6: Side view of the area delimited by the Delcam PowerSHAPE™ 2010 program.

Figure 7: Basal view of the area delimited by the Delcam PowerSHAPE™ 2010 program.

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simple mounting or direct bonding [5]; the same measurement made with a compass showed a mean thickness of 2.5 mm (Figure 2).

These clinical observations are important because they are consistent with reports and clinical studies [11,12]. Obviously, this is an empirical measurement that can vary depending on the type of bracket, the configuration method, and the amount of resin and the lingual surface of the tooth. Therefore, accurate studies on this topic are necessary because such clinical evidence calls into question how much this thickness could interfere in the space occupied by the tongue.

Our study used models from a sample of individuals with normal natural occlusion, unlike a previous study that also analysed the dimensions of the palate [19], but in individuals with malocclusion. This factor does not invalidate the results obtained in that study; however, in a sample of individuals with normal natural occlusion, the results obtained can serve as parameters for future studies on this understudied topic.

Another important aspect is studies that report results related to the biomechanics, configurations and lingual arch shapes that improve the lingual technique because comfort is extremely important for patient adherence to the technique [6-10].

The lack of new studies related to this topic led us to investigate the ideal space that the tongue should occupy in its natural position.

Thus, we aimed to identify scientific evidence in the literature that reported the size of the tongue and the ideal space for its positioning. The tongue is a difficult muscle to measure, as no standardised measurement technique was found. Only one study reported using magnetic resonance imaging for this purpose and correlating the results with radiographs [18].

Thus, our search on focused studies that showed the space required for the tongue to be well positioned, and the space was related to the hard palate structure.

Most studies that used 3D technology to study the dimensions of the hard palate were related to treatments of palatal disjunction in young patients [15,16,17,26]. In contrast, based on the mean age of our sample, our patients may be considered adults. The morphology, size and shape of the palate was investigated in a longitudinal study spanning ten years in adult patients using similar landmarks in the palate as those used in the present study [14]. The results were digitised (3D) and suggested that the shape of the hard palate does not seem to change in adult patients.

The 3D technology used in our study corroborates the opinion of other authors who also used this technology and agreed that it is an effective and less invasive tool than cone beam computed tomography and is probably more accurate than measurement of the transversal space of the hard palate in a linear manner, i.e., 2D measurements obtained based on the cusps of teeth [14-17,19,26,27].

We agree with the findings of a previous study21 in that when a diagnosis is made for orthodontic treatment, it is of great importance in clinical practice to define the facial type and correlate it with the stomatognathic functions, musculature and occlusion. Thus, also according to this previous study [21], our sample was divided using the most common facial type nomenclature, i.e., mesofacial, dolichofacial and brachyfacial individuals.

As the musculature surrounding the skeletal scaffold of the face could affect the measurements of the palate, dolichofacial individuals could have some alteration in their measurements in relation to other facial types because the external environment could affect these facial types [18].

The results of this study showed that the palate height and volume were slightly smaller in dolichofacial individuals (Table 2). However, we did not find significant differences that could confirm this relationship, unlike a study that found a difference in the depth of the palate [19], in which the brachyfacial individuals had a shallower palate than dolichofacial individuals. However, it is important to note that in our sample, the number of dolichofacial individuals was very small. The results of another study that compared the dimensions of the hard palate in children with different facial types of also showed no significant difference in hard palate measurements among brachyfacial [27], mesofacial and dolichofacial children.

Some studies have elected to determine the facial type using Ricketts’ cephalometry analysis [19,27], unlike our study and another study [28], which used subjective facial analysis. A different study that evaluated the agreement between subjective facial analysis and cephalometric analysis using anterior and profile photographs and lateral teleradiographic images concluded that subjective facial analysis is an efficient method and that agreement exists between both analyses in the evaluation in the soft tissue [20]. These results supported our choice of method for classification of the sample.

Regarding the skeletal pattern, we also classified individuals in our sample by subjective facial analysis [23]. However, a previous study investigated the performance of the subjective method of facial pattern classification and concluded that this method requires improvements in

PatternsWidth Length Height Volume

mean sd mean sd mean sd mean sdI (n=43) 38,31 2,59 37,44 2,42 17,03 2,42 10,52 1,72II (n=27) 37,94 3,25 37,48 2,44 16,79 2,42 10,41 1,65

P 0,903 ns 0,757 ns 0,925 ns 0,834 nssd-standart deviation; ns-no significant

Table 1: Comparison among facial patterns, adjusted for sex and age, regarding palate width, length, height and volume.

TypesWidth Length Height Volume

mean sd mean sd mean sd mean sdM (n=35) 38,56 2,82 37,72 2,47 17,36 2,11 10,78 1,75B (n=28) 37,81 2,99 37,00 2,05 16,60 2,79 10,32 1,60D (n=7) 37,61 2,50 37,93 3,42 16,17 2,00 9,58 1,44

P 0,577 ns 0,424 ns 0,350 ns 0,215 nssd-standart deviation; ns-no significant

Table 2: Comparison among facial types, adjusted for sex and age, regarding palate width, length, height and volume.

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the morphological criteria used to discriminate the five facial patterns (pattern I, pattern II, pattern III, long face and short face) [29]. This conclusion may have been derived from the opinion of other authors [28], according to which, patterns I and II are the most prevalent facial patterns, while the least prevalent is the short face pattern. This may explain our findings, as only individuals with pattern I and pattern II were found. In turn, this result may have occurred because the sample had normal occlusion; therefore, it is assumed that a balance existed in the skeletal bases with minimal discrepancies. Unfortunately, we have no scientific evidence of this, as it is only an assumption. However, as observed in Table 1, our study found that both pattern I and pattern II individuals showed no significant changes in hard palate measurements.

As this is an original study, we cannot compare its results. However, some considerations can be made, such as the need for further studies on the structure of the hard palate, including the tongue muscle, so that reliability is improved when correlating both structures within a skeletal scaffold. Thus, the results may aid professionals involved in lingual and/or conventional orthodontic treatment. For the latter type of treatment, the aforementioned structures are of inestimable importance because appliances are used, such as expanders, that are directly related to the same structures.

Conclusions1. The 3D method can be used to analyse the width, length, height

and volume of the hard palate.

2. No correlations were found between facial patterns I and II or the dolichofacial, mesofacial and brachyfacial facial types with the width, length, height or volume of the hard palate.

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TitleCorresponding AuthorAbstractKeywordsIntroductionMaterials and Methods DiscussionResultsConclusionsReferencesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Table 1Table 2