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ORIGINAL RESEARCH ARTICLE ESTIMATION OF VERTICAL DISTANCE OF INCISIVE PAPILLA WITH MAXILLARY CENTRAL INCISOR AND THEIR CORRELATION IN VARIOUS ARCH FORM

Background : The relation of incisive papilla to the incisal edges of the maxillary central incisors in a vertical dimension could serve as a guide for inciso-cervical placement of anterior teeth in denture base according to the arch form of the edentulous patient. The aim of this study was to determine the vertical distance between incisive papilla and maxillary central incisor in different arch form. Methods: A cross-sectional study was conducted among 100 dentulous subjects. The vertical distance between the incisal edges of maxillary central incisor and center of incisive papilla was measured by a digital caliper on casts obtained from dentate subjects meeting inclusion criteria after which statistical analysis of data using SPSS v26 version. Results: The mean vertical distance between maxillary central incisor and incisive papilla were 5.97±1.03mm in ovoid, 6.09±0.98mm in square and 6.23±0.89mm in taper arch form. Conclusions: The result obtained in this study can be used as a clinical guideline for the fabrication of maxillary occlusal rim and may aid in determining the position of occlusal plane along with the reference of other anatomical landmarks.


INTRODUCTION
The primary goal of prosthodontic rehabilitation of missing teeth is to restore patient's oral health, function, comfort, and confidence that are biologically compatible and desirable. 1 Besides function, esthetics is another prime concern of patient seeking prosthodontic treatment. The selection and arrangement of maxillary anterior teeth for edentulous patient in a natural and esthetically pleasing form is a challenging task particularly in absence of pre-extraction records. Determination of correct anterior incisal tooth position is important in fabricating complete denture. The proper positioning of artificial teeth lays the foundation for correct natural speech, esthetics and normal function. 2,3 The incisive papilla, which is a small pear shaped eminence, serves as one of the significant anatomical landmarks that serves as a guide to arrange the maxillary anterior teeth during complete denture fabrication. 4 If the incisal edges of the maxillary central incisors could be related to the incisive papilla in a vertical dimension in various arch form, this would serve as a guide for inciso-cervical placement of anterior teeth in denture base according to the arch form of the edentulous patient. Thus, the aim of this study was to determine the vertical distance between incisive papilla and maxillary central incisor in different arch form.

This was a cross-sectional study carried out on Department of Prosthodontics & Maxillofacial Prosthetics of Chitwan Medical
College from Feb 2020 to Nov 2020. The ethical approval letter was obtained from Chitwan Medical College-Institutional Review Committee (CMC-IRC/076/077-116). Hundred dentulous subjects with full complement of natural teeth along with symmetrical and acceptable alignment of maxillary dentition were included in the study. Subjects with worn/restoration of anterior teeth, tooth with agenesis, crowding, rotation, periodontal diseases were excluded from the study. The consent of the patient for taking the impression was taken and who agreed for voluntary participation were only included. The casts were obtained from impression of maxillary arch and were divided into square, ovoid and taper arch form by using Diagnostic Orthoform Template as advocated by 3M Unitek. The midpoint of the incisive papilla was marked on each stone cast.  Figure 2). The flat edge plane of the depth caliper contacted the mesial incisal edges of the maxillary central incisors and the midpoint of the flat edge plane of the depth caliper matched with the midpoint of the maxillary central incisors. Thus, the vertical distance of incisal edge of maxillary central incisor from incisive papilla was measured. The measurements were done by the same investigator at three separate times using the same instrument. The average values of the measurements were calculated using mean, standard deviation and chi square tests. Statistical Package for the Social Sciences version 26 was used for the analysis.

RESULTS
The mean vertical distance between incisive papilla & central incisor was found to be 5.97±1.03 in ovoid, 6.09±0.98 in square and 6.23±0.89 in tapering arch form showing the greatest mean vertical distance between incisive papilla & central incisor in tapering arch form. However, the distance was not statistically significant (p value 0.15). The study showed the mean anteroposterior length of incisive papilla to be 6.19±1.03 in ovoid, 5.77±1.28 in square and 6.29±1.08 in tapering arch form with no significant variation in different arch form (Table 1-3).  Comparison of arch forms according to the gender of the patient was found to be statistically significant (p value 0.028). Square arch form was common in male whereas ovoid arch form in female, the tapering arch form being the least common in both the gender (Table 3).

DISCUSSION
Restoration of natural appearance of an individual is one of the primary objectives of prosthodontic rehabilitation in patients requiring complete dentures. Though prostheses cannot exactly substitute the natural teeth, however if fabricated in correct manner based upon some measurable parameters, they are not only functionally stable but also biologically and aesthetically viable. 5,6 The positioning of anterior teeth is one of the key factors for esthetics of complete denture. This can be guided to a certain extent by available pre-extraction records such as pre-extraction radiographs, anthropometric records, casts, and photographs that have been used in the past. Additionally extra-oral landmarks such as the philtrum, ala of the nose, pupils, canthus of the eye etc. have been related to the size and shape of teeth and arch form to obtain values which would guide in the selection and arrangement of teeth in the complete denture. 7,8 Incisive papilla, being a stable landmark, can be used as a biometric guide to determine the midline, anteroposterior position of the anterior teeth, as a starting point for occlusal rim fabrication and for the determination of parallelism of occlusal plane when used in conjunction with hamular notch. 9,10 According to Harper, a stable incisive papilla was obtained by caliper measurements on pre-extraction and post resorption models over 7 years thereby stating the incisive papilla as a dependable basis for reproducing the horizontal and vertical position of the maxillary central incisors. 2 Although the shape of the papilla shows a wide range of variation, the middle or center of the papilla is commonly used as a point of reference in many studies. 11 Although, the horizontal relationship between incisive papilla and the maxillary central incisors had been investigated by several studies 12,13 there are very few specific information in the literature relative to vertical distance between the incisive papilla and the maxillary central incisors.
Fu et al used a three-dimensional precise measuring device, 14 Mersel et al used caliper to measure the horizontal distance and the vertical pin of the parallelometer along with caliper to measure the vertical distance. 15 Guldag et al., used digital Vernier's caliper on the surveyor to measure the vertical distance. 4 In the present study surveyor and digital Vernier's caliper was used to measure the horizontal and vertical distance of midpoint of incisive papilla and the mesial incisal edges of maxillary central incisors.
Chalsuthipan and Boonsiri investigated the relationship between the incisive papilla, maxillary central incisors and canines in Thai population. They found the vertical distance from the most distal point of the incisive papilla to incisal edge of the central incisors ranging from 6.94 to 7.23 mm with the mean of 7.08 mm. 16 Guldag et al found the mean vertical distance between maxillary central incisors and incisive papilla to be 6.70±0.81 mm. The vertical distance range was 5.51 mm to 8.89 mm. 4 The present study supports the finding of Guldag

CONCLUSION
Within the limitations of the study, the vertical distance between central incisor and incisive papilla determined in various arch form can be used as a guideline for the fabrication of occlusal rim and to locate the vertical placement of central incisor. Arch form parameter being statistically significant according to gender can also be considered. As the study is carried out in small group of population, further studies including different races and different age groups can be conducted for the more reliable findings.