Comparison of Distance between the Most Prominent Part of Labial Surface of Maxillary Central Incisors with the Posterior Limit Of The Incisive Papilla in Various Arch Forms

 

Asma Naz1                                               BDS, FCPS

Shujah Adil Khan2                               BDS

BACKGROUND: After the loss of natural teeth, replacement of teeth by prosthodontic services becomes a vital part in the modern day living. They provide effective mastication and esthetics. To make it more proficient both biologically and functionally, they are accommodated in particular geometric manner referred to as a dental arch form. The objective of this study is to compare the distance between the most prominent part of labial surface of maxillary central incisors with the posterior limit of the incisive papilla in various arch forms.STUDY DESIGN: Cross sectional In-vitro experimental study.

PLACE AND DURATION OF STUDY : Department of Prosthodontics,  Dr. Ishrat ul Ebad Khan Institute of Oral Health Sciences, DUHS, Karachi, Pakistan from March 2012 to August 2012.

METHODOLOGY: 203 College students from third and final years were selected with symmetric faces and all teeth present except third molars. Subjects with malformed teeth, periodontal problems, orthodontic treatment or restorations on the labial tooth surfaces were excluded. After sample selection, impressions were made for upper and lower arches and the resultant casts were standardized for each sample. Arch forms were assessed by their morphological description. Measurements were recorded for incisive papilla (IP) and maxillary central incisor (CI) distance for papillo-incisal distance (PID) with a modified digital vernier caliper with the casts placed on a flat horizontal surface. The fixed jaw blade of the vernier caliper was extended 10 mm from the original for effective measurements.

RESULTS: The mean PID was 11.06 mm ± 1.46. Among the subjects were 90.6% had ovoid, 3.9% had squarish and 5.4% had tapering arch forms. Mean PID for Ovoid arches were found to be 11.04mm, Tapering 10.84mm and Squarish 12.02mm.

CONCLUSION: The suggested mean PID for placing prosthetic central incisors is 11.06mm. There is a higher presentation of ovoid arch forms.

HOW TO CITE: Naz A, Khan SA. Comparison of Distance Between The Most Prominent Part of Labial Surface of Maxillary Central Incisors With The Posterior Limit of The Incisive Papilla In Various Arch Forms. J Pak Dent Assoc 2014; 23(2):76-79.

INTRODUCTION

Prosthesis replacing anterior teeth frequently look artificial because teeth which have been selected are smaller than the natural teeth which they are replacing1, and this is considered a problem in fabricating dentures. With the absence of pre-extraction records3, the selection of appropriate size of maxillary anterior teeth is one of the most confusing and difficult aspect of complete denture construction3 Suitable positioning has always posed great challenges4. The best position for placing artificial teeth is the one occupied by its predecessors5. When pre-extraction records are available the task is simple6.  Several methods have been employed for placement in positions of natural predecessors7.

Multiple landmarks have been used and the most common being the incisive papilla4, labial vestibule5, retromolar pad8, palatal vestigial remnants9, midpalatal suture10 and palatal rugae.

The incisive papilla (IP) is a stable and noticeable anatomical landmark which survives during the progression from dentate to edentulous4. It is an important landmark as it is a stable structure and usually does not shift in adult life11,12. It serves to provide a guide to determine the midline10, the labio palatal position of prosthethic incisors and canines, inciso-cervical position of incisors4, a starter for the occlusal rim fabrication and the central incisor region13 and determination of parallelism of the occlusal plane, when used in conjunction with hamular notch14.

The distance of IP from the central incisors has been measured from the center6, or posterior border of the papilla4,5,8,9,15. This distance also varies in the different arch forms. Studies have been conducted for other populations such as Caucasian4,5,10, Chinese9, Thai8, Korean15 and Taiwanese populations and Pakistani populations as well.

The present study aims at documenting this distance in dental students of two classes in a dental hospital of Karachi, Pakistan with different arch forms. This will reduce the dentist’s chair side effort and patient’s time by allowing the dental laboratory technicians to reproduce the relationship established between the natural teeth and the supporting facial structures5, especially in the absence of pre extraction records.

METHODOLOGY

A cross sectional in-vitro experimental study was carried out over a period of 6 months from March 2012 t o August 2012 at Department of Prosthodontics, Dr Ishrat ul Ebad Khan Institute of Oral Health Sciences, DUHS. Undergraduate students of 3rd and 4th years were selected for sampling, and all of the students ranging in age between 20 and 22 years. The selection criteria were based on healthy dentitions, well aligned arches with all incisors, canines, first and second premolars and molars present. Subjects with malposed teeth, periodontal disease, restored anterior teeth, history of orthodontic treatment, congenital and/or acquired maxillary defects, orthognathic/reconstructive surgical procedures were excluded.

Maxillary impressions were made with Irreversible hydrocolloid (Tropicalgin by Zhermack Spa) following the manufacturer instructions for mixing using the supplied water powder measuring scoop and cylinder. It was hand mixed in a rubber bowl and loaded onto stainless steel perforated stock trays. After introduction of the tray into the patient’s mouth the material was allowed to set for two and a half minutes to ensure an adequate final set. The impression was removed, inspected, washed and disinfected for ten minutes and casts were made using type 4 dental stone and bases were made using a standard base former.

The casts were placed on a horizontal surface and incisive papilla was first identified and then boundaries marked with lead pencil. Distance from posterior surface of IP to maximum convexity of central incisor, the papillo incisal distance (PID) was measured with a modified vernier caliper:  The fixed jaw blade of the vernier caliper extended 10 mm from the original for effective measurements. The arch forms were assessed by their basic morphological description classified as Ovoid, Tapering and Squarish.

The collected data was entered, and analyzed using SPSS program version 16. The study variables included “gender”, “PID” and “Arch Form”. Comparative mean were calculated for the variables defined in the study.

RESULTS

Among 203 subjects about 90% were females as being dominant in the institution and the age group range in between 20 – 22 years. The mean PID was 11.06 mm ± SD 1.46. Among the subjects were 90.6% had ovoid, 3.9% had squarish and 5.4% had tapering arch forms. Mean PID for Ovoid arches were found to be 11.04mm, Tapering 10.84mm and Squarish 12.02mm.

DISCUSSION

Arranging artificial teeth according to the anatomical landmarks helps in positioning the teeth in relation to the general arch form and one another. The pre-maxilla may be referred to as an “esthetic zone” because of its high visibility and influence on facial appearance. Improper positioning of maxillary centrals may result in distorted appearance and may affect speech16.

Many geometric arch forms and mathematical functions have been proposed to describe dental arches over the years17,18. Some authors5,19,20 prefer to classify dental arches into ovoid, tapering and squarish, this classification of arch forms was used in the present study. The majority of the subjects had an ovoid arch form 90% where as 6% had tapering and 4% had squarish arch forms. In a comparison of Japanese and Caucasian mandibular dental arches15 the Japanese group had 46% squarish arches, 42% ovoid and 12% tapering arches. The Caucasian group had 18% squarish arches, 38% ovoid and 44% tapering. The author reported that there were ethnic differences in arch forms. This explanation may also be relevant to the Pakistani samples as reported

Papillo-Incisal Distance

by Zia21. PID is an important biometric guide for positioning of maxillary occlusal rim and central

Statistics

incisors22. Mean PID measured in this study sample was 11.06mm SD±1.46. In Grave’s1 study with the same landmarks the mean PID was 13.1mm on dentate subjects in Caucasians. The mean distance was 12.45mm in another Caucasian sample23. In a Thai sample it was

Frequencies

11.093mm and 12.269mm from incisive papilla to incisal edge of the central incisor and the most convex labial surface respectively8. In a study on Southern Chinese population the posterior limit as well as center of the incisive papilla. to the most labial contour of the central incisor was used9. Mean value for the distances were 12.71mm and 9.17mm respectively. A Jordanian study recorded 12.93mm from incisal tangent to the posterior limit of the incisive papilla using computer scanner and software program24. In a 3D orthographic study on Korean sample the PID from the posterior border of the incisive papilla to a vector drawn in the midpoint of mesio-incisal tips of both maxillary incisors was 11.96mm15. The PID in studies using posterior limit of the incisive papilla as the reference point for measurement is comparable to this study.

The present study was designed to discover various arch forms in the collected sample and to find relation of PID in these arch forms. The ovoid arches were dominant i.e. 82.4%, the other two arch forms combined were only 17.8% which may have affected the final outcome. This could be a limitation of present study and use of equal number of the three arch forms may be explored in future research projects.

CONCLUSIONS

The suggested mean PID for placing prosthetic central incisors is 11.06mm. There is a higher presentation of ovoid arch forms.

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  1. Assistant Professor and Head of department, Department of Prosthodontics, Dr. Ishrat ul Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences, Karachi.
  2. MDS Resident Department of Prosthodontics, Dr. Ishrat ul Ebad Khan Institute of Oral Health Sciences, DUHS, KarachiCorresponding author: “Dr. Shujah Adil Khan” < shujah.adil@gmail.com >