Correlation of vertical dimension with lip position , nasolabial angle and incisal display at rest and at smile in young adults

Research Article


INTRODUCTION
The pleasant dental esthetics has been rated as an important factor for psychosocial well being. Ideal occlusion should certainly remain the primary functional goal of orthodontics but the esthetic outcome is critical for patient satisfaction. Record taking in orthodontics is considered immensely important as it aids in determining the finest possible treatment plan for each case. 1 This study is designed to compare facial and dental dimensions and various photographic parameters among patients with long, average, short faces in central Indian population. With the rise in demands of radiation safety there is a need to minimize radiation exposure and hence this technique of photographic diagnostic analysis is useful. 2 An alternative method to cephalometric analysis needs to be worked upon which is reliable, easily assessable and convenient for multiple usage by the orthodontist & digital photographic analysis could be one of the answer. The application of photogrammetry in orthodontics was first proposed by Stoner, who compared pre-and post-treatment profiles with ideal profiles. Different authors have included soft tissue parameters in photogrammetry, and various facial soft tissue analyses based on standardized photogrammetri. Other photographic methods have also been used to quantify facial aesthetics. Facial soft tissue analysis has been conducted using newer threedimensional (3D) methods, such as laser surface and, more recently, scanning digital 3D photogrammetry. Photogrammetry has been introduced as an alternative to direct measurements to obtain distances between facial landmarks using both two-dimensional and three-dimensional methods. Obtaining measurements from photographs is less intrusive to the patient, more cost-effective, provides a permanent record of the face that can be accessed at a later time, and offers consistency in longitudinal studies in which different observers with different direct measuring techniques might participate. 3 Facial harmony and balance are determined by the facial skeleton and its soft tissue drape. The evaluation of the soft tissue profile is vital in smile designing. Soft tissue changes have been shown to accompany growth, orthodontic treatment as well as plastic surgery. It is for these reasons that the soft tissue profile must be carefully examined before a decision regarding smile enhancement, orthodontic treatment and/or orthognathic surgery can be made. 4 In depth clinical and photographic analysis among various vertical facial patterns depicting correlations with lip position, nasolabial angle and incisal display in all types of malocclusion in central Indian population is still lacking. The purpose of the present study is to determine whether there should be some relation in certain esthetic parameters, so that an additional all diagnostic parameter could be available to the orthodontist in treatment approach.

OBJECTIVES
To evaluate the gender specific effect of Vertical Dimension (VD), high VD, average VD and low VD on the position of lip, amount of incisal display and nasolabial angle at smile and at rest.
To emphasize on this technique of photographic diagnostic analysis to give due attention to this essential diagnostic aid.

MATERIAL & METHOD
The sample will consist of central Indian population of young patients age ranging from 18 -25 years, equally including both male and female in genders having any VD (high/average/low) irrespective of any malocclusion (Angles class I/class II/class III). The sample included in this study is selected from the patients referred to Bhabha college of dental science (BCDS), Bhopal for orthodontic consultation and treatment purpose Nikon D3400 digital camera with lens AF-P DX Nikon 18-55mm, 70-300mm f/4.5-6.3G ED VR lens will be used for taking photographs. The camera mounted on a tripod stand with the lens and positioned parallel to the true perpendicular of the face in natural head position. A distance of 3 feet was maintained between the camera and the subject. The subject was made to face a mirror placed 120 cm away to aid in obtaining Natural Head Posture (NHP). A metal scale attached to a drip stand was secured just side of the subject. Four photographs (frontal rest, frontal smile, profile rest and profile smile) from each of 150 subjects were taken at natural head position.The images are transferred to imageJ software. Image J is a Java-based image processing program developed at the National Institutes of Health and the Laboratory for Optical and Computational Instrumentation (LOCI, University of Wisconsin). 1,3 Its first version, ImageJ 1.x, is developed in the public domain, while ImageJ2 and the related projects SciJava, ImgLib2, and SCIFIO are licensed with a permissive BSD-2 license. The project developer, Wayne Rasband, retired from the Research Services Branch of the National Institute of Health in 2010.
While in clinical examination measurement patients will b asked to sit on a chair in relaxed posture, making their FH plane parallel to the floor and maintaining the occlusal contact, clinically, measurements will b done using vernier calliper. After clinical examination, 4 extra oral photographs will be taken of the same patient. The frame that best represents the patient's natural unstrained social smile that is the most reproducible smile in all the frames will be selected8. Frontal at rest, frontal at smile, profile at rest and profile at smile of each patient will be taken, keeping the patient camera distance of 3 feet and by placing a metal scale on one side of the patient's head. The image received will be analyzed by using ImageJ software.          The Correlation between variables in frontal view was done with the help of pearson correlation. The correlation coefficient value between incisal display and vertical dimension using clinical examination was 0.561. The same result was interpreted using photographic examination at rest (0.555). Therefore incisal display shows moderate positive correlation with vertical dimension which was statistically significant. The photographic examination at smile shows weak correlation between incisal display and vertical dimension with correlation coefficient 0.149.
The correlation coefficient value between incisal display and upper lip length was 0.436. The same result was interpreted using photographic examination at rest (0.419) and smile (0.341). Therefore incisal display shows moderate positive correlation with upper lip length which was statistically significant.
The correlation coefficient value between upper lip length and vertical dimension was 0.561. The same result was interpreted using photographic examination at rest (0.535) and smile (0.400). Therefore upper lip length shows moderate positive correlation with vertical dimension which was statistically significant.
Statistically significant positive moderate correlation between incisal display & vertical dimension, incisal display & upper lip and lower lip length was seen among the participants with high VD, average VD and low VD by using clinical examination, photographic examination at rest and smile. (Table 3) Badusha S J, Joneja P, Agarwal A, Choudhary D S: Correlation of vertical dimension with lip position, nasolabial angle and incisal display at rest and at smile in young adults  The Correlation between variables in profile view was done with the help of pearson correlation. The correlation coefficient value between Nasolabial Angle and vertical dimension using clinical examination was 0.026. The same result was interpreted using photographic examination at rest (0.029) and smile (0.027). Therefore Nasolabial Angle shows weak positive correlation with vertical dimension which was statistically non -significant. Therefore here we accept null hypothesis that there was no correlation between Nasolabial angle and vertical dimension.

DISCUSSION
In order to effectively and accurately diagnose compounding dentoskeletal problems in the vertical dimension, the orthodontist must have an understanding of the morphologic characteristics commonly attributed to the different vertical dimension patient, as well as the types and degree of variation that can be expected within the short, average and long face patient. [5][6] Many structural elements enter into the configuration of the face like cartilage, connective tissue, and musculature as well as bony tissue. Any developmental changes in the soft tissue overlying the skeletal parts, in itself, may influence facial appearance. [7][8][9][10][11] It is pertinent that the orthodontist follows a thorough and proper diagnostic protocol to obtain consistent and predictable results. This study shows that standardized photographic technique has numerous advantages as the subject does not move, there are no skin pressure-related errors, also it is easier to take measurements, the time needed with the patient is also lesser, also it is easier for the clinician to explain the photographs to the patient rather than a cephalogram. Additionally, measurements can be made repeatedly as well as the data can be stored permanently, making longitudinal follow up studies possible. There are some disadvantages of the photographic technique as well distortion of the image due to the presence of some distance between the subject and the lens as it causes objects farther to the camera appear smaller than those closer to it . But this factor is only critical when we are making an attempt to equate structures located in the various planes of space. Furthermore, angular variables were used more often, which partially incapacitates the difficulty of magnification. cephalograms provide us with accurate measurements, their major disadvantage is the exposure of patients to radiation. With our results we can conclude that photographs can be used as an alternative to cephalograms. The advantages of photographs are that they are safe and free from radiation, easy, less time consuming, do they do not require any special equipment. [12][13][14][15] Vertical facial form is an important element of orthodontic assessment. Large variations are found in the vertical dimension and these affect the clinician's approach to successful diagnosis, treatment planning, and mechanics (Nanda, 1988 , 1986). In these studies it was found that photographic records provide valid, reproducible, and representative ratings of dental and facial aesthetics. 16 Their findings suggested that photographic analysis could be used as an alternative when cephalograms cannot be obtained due to lack of availability of equipment, concerns with radiation exposure and in analysis of large number of samples in epidemiological studies. [17][18][19] CONCLUSION The results of the study highlights the importance of correlation of the vertical facial pattern that is vertical dimension, incisal display, upper lip length, lower lip length, clinical FMA and nasolabial angle. Photogrammetry was found to be a quick easy, cost effective and reliable diagnostic tool which can reduce radiation exposure and reduce the number of cephalograms during treatment. Evaluation of facial measurements in large samples can be carried out accurately using the non invasive method can be used for assessment for diagnosis and treatment planning. The vertical proportions of facial soft tissue following the underlying vertical skeletal pattern high vertical dimension is associated short upper lip more incisal display more clinical FMA and obtuse nasolabial angle. The low vertical dimension is associated with acute nasolabial angle and low clinical FMA. The study opens the scope of further research in the subject to substantiate the result of the research. ImageJ imaging software developed in public domain is adequately reliable in photographic evaluation in orthodontics and can replace manual photographic analysis in orthodontics.