8/16/2019 016 Andrea- Smile Design

http://slidepdf.com/reader/full/016-andrea-smile-design 1/3

5.0 Smile Design

5.1 Introduction

The goal of an esthetic makeover is to develop a peaceful and stable masticatory system,here the teeth, tissues, muscles, skeletal structures and !oints all function in harmony "#eter

Da son$. It is very important that hen planning treatment for esthetics cases, smile designcannot be isolated from a comprehensive approach to patient care. %chieving a successful,healthy and functional result re&uires an understanding of the interrelationship among all thesupporting oral structures, including the muscles, bones, !oints, gingival tissues and occlusion.

5.' Dental midline

The midline refers to the vertical contact interface bet een t o ma(illary centrals. Itshould be perpendicular to the incisal plane and parallel to the midline of the face. )inor

discrepancies bet een facial and dental midlines are acceptable and, in many instances, notnoticeable. *o ever, a canted midline ould be more obvious, and therefore, less acceptable.The ma(imum allo ed discrepancy can be ' mm and sometimes greater than ' mm discrepancyis esthetically acceptable so long as the dental midline is perpendicular to the interpupillary line.+arious anatomical landmarks such as midline of the nose, forehead, chin, philtrum,interpupillary plane can be used as guides to the midline assessment.

The philtrum of the lip is one of the most accurate of these anatomical guide posts. It isal ays in the center of the face e(cept in surgical, accident or cleft cases. The center of the

philtrum is the center of the cupids bo and it should match the papilla bet een the centrals. If

these t o structures match and the midline is incorrect, then the problem is usually incisalinclination. If the papilla and philtrum do not match, then the problem is a true midline deviation.% midline that does not bisect the papilla is more noticeable than the one that does not bisect the

philtrum.

To evaluate the midline, one must al ays consider

1. location and

'. alignment

. patient input

)idline should be

a. parallel to the long a(is of the face- the line angle that forms the contact bet een thecentrals should be parallel to the long a(is of the face

8/16/2019 016 Andrea- Smile Design

http://slidepdf.com/reader/full/016-andrea-smile-design 2/3

b. perpendicular to the incisal plane- the line angle that forms the contact bet een thecentrals should be perpendicular to the incisal plane and

c. over the papilla- the midline should drop straight do n from the papilla.

% face bo transfer or even a reference stick aligned parallel to the interpupillary plane provides useful information in laboratory communication regarding midline inclination and the possible presence of a canted incisal plane.

)a(illary and mandibular midlines do not coincide in /5 of cases. Therefore, it is notadvisable to use the mandibular midline as a reference point for establishing the ma(illarymidline. )ismatch bet een ma(illary and mandibular midline does not affect esthetics sincemandibular teeth are not usually visible hile smiling.

5. Incisal lengths "incisal edge positions$

)a(illary incisal edge position is the most important determinant in smile creation becauseonce set, it serves as a reference point to decide the proper tooth proportion and gingival levels.The parameters used to help establish the ma(illary incisal edge position are-

1. degree of tooth display,

'. phonetics and

. patient input

Degree of tooth display- hen the mouth is rela(ed and slightly open, .5 mm of the incisal thirdof the ma(illary central incisor should be visible in a young individual. %s age increases, thedecline in the muscle tonus results in less tooth display.

#honetics- #honetics is a ma!or determinant of the tooth length. In order to determine proper lip,tongue and incisal support and tooth position, it is necessary that the patient sits either erect orstands during the phonetic e(ercises. The various phonetics used are as follo s-

• ) sound- %fter pronunciation, the lips return to their normal rest position, allo ing

evaluation of the amount of the tooth display in rest position.• 2 sound- The ma(illary incisal edge position should be positioned half ay bet een the

upper and lo er lip during the 324 sound.

8/16/2019 016 Andrea- Smile Design

http://slidepdf.com/reader/full/016-andrea-smile-design 3/3

• and + sounds- ricative sounds are produced by the interaction of the ma(illary incisaledge ith the inner edge of the lo er lips6 vermilion border. Thus, fricative sounds helpto determine the labiolingual position and length of the ma(illary teeth.

• S sound- During pronunciation, the mandibular central incisors are positioned 1 mm behind and 1 mm belo the ma(illary incisal edge.

#atient input- Intraoral cosmetic previe and provisional restorations help to confirm proper placement of the final incisal edge position. The patient desires must be met as best as possible, provided they do not interfere ith the parameters previously discussed.

7orrect incisal edge position is crucial because it is related to the pitch of the anteriorteeth, labial contours, lip support, anterior guidance, lingual contours and tooth display. The pitchof each anterior tooth is determined by the combination of correct lip support and the lingual

labial position of the incisal edge. This location influences anterior guidance and the labial andlingual contours. In short, all these factors play a dominant role in both esthetics and function.

8eferences- http-99 .ncbi.nlm.nih.gov9pmc9articles9#)7 0100'/9