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Smile analysis by almuzian

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  • 1. Smile analysis Smiling involves: 1. The development of prominent nasolabial folds 2. Flaring of the nostrils 3. Inferior movement of the nasal tip 4. Display of the teeth 5. Pronounced lip movement 6. Squinting of the eyes The method of smile measurement described by Ackerman et al (1998) It depends on drawing vertical and horizontal lines on a photograph of an unstrained posed smile. The vertical lines correspond to the commissures of the lips, the distal embrasure of the upper canines and the dental midline. The horizontal lines correspond to the upper border of the upper lip, the lower border of the upper lip, the incisal edge of the right central incisor, the upper border of the lower lip and the lower border of the lower lip. The following measurements can then be obtained: A. maximum upper incisor exposure B. upper lip drape C. lower lip to upper incisor D. interlabial gap at rest and smiling E. commissure (smile) width F. smile index: The smile index was described by Ackerman et al (1998). It is defined as follows:
  • 2. Smile index =Intercommisure width/Interlabial gapon smiling*100. The lower the smile index, the less youthful the smile appears (because there is relatively less tooth display). G. frontal intercanine width the intercanine width as measured from a full-face H. right and left buccal corridor: the buccal corridor is measured from the mesial line angle of the maxillary first premolars to the inner aspect of the commissure I. Buccal corridor ratio: Smiling component factors 1. Lip factors  The lip line  Buccal corridors  The smile arc 2. Dental factors  Teeth color  Teeth proportion and symmetry  The midlines  Tooth angulation  Tooth inclination 3. Gingival factors  Embrasures  Connectors
  • 3.  Contacts  Gingival contour  Gingival levels In details 1. Lip factors A. The lip line • It is the vertical relationship between the upper lip and the maxillary dentition during smiling • Females, on average, show 1 mm of gingival smile line and males show –1 mm. • A number of factors can influence the lip line : 1. The type of smile. posed smile or spontaneous smile 2. Activity of the upper lip. Excessive elevation, also termed hypermobility, 3. Vertical maxillary height. 4. Vertical dental height. 5. Incisor inclination retroclination increases tooth display. 6. Gingival height 7. Age Recently  Botulinum toxin type A (Botox): Many patients with excessive gingival display have excessive muscle contraction.  The use of Botulinum toxin A (BTX-A) to reduce gingival display is described by Polo (2008).
  • 4.  BTX-A blocks neuromuscular transmission by binding to receptor sites on motor or sympathetic nerves,  It therefore produces partial chemical denervation of the muscle . Also it has a filler action to increase the intramatrix space and muscle size.  The muscles injected were the elevators of the upper lip –levator labii superioris, alaeque nasi, and zygomaticus minor. B. Buccal corridors  The buccal corridor is the space between the buccal surface of the premolars and molars and the angle of the mouth during smiling.  Ideally, this should be minimal  Buccal corridor ratio:  The buccal corridor is dependent on a number of factors: 1. Anteroposterior maxillary position. 2. Arch width and arch form 3. The vertical dimension. There is a reported inverse relationship between the vertical dimension and the buccal corridor area. 4. Molar inclination. 5. Inter-commissure distance during smiling. The greater this distance, the greater the buccal corridor width.
  • 5. C. The smile arc  The smile arc was first described by Frush and Fisher in 1958.  It is the relationship between the curvature of the maxillary incisal edges and the curvature of the lower lip in the posed smile.  A number of factors are important in determining an ideal smile arc relationship including 1. The maxillary occlusal plane angle, 2. The curvature of the lower lip 3. Tooth length. 4. Age that cause flattening of the incisal edge and in-consonant smile arc 5. Poor orthodontic treatment, Parekh et al (2006) investigated the attractiveness of smile arc and buccal corridor width and found that excessive buccal corridors and smile arcs were rated less attractive by both orthodontists and lay persons. In addition, flat smile arcs decreased attractiveness regardless of the buccal corridor width. Smile arc can be achieved by differential bracket positioning. 2. Dental factors A. Teeth color B. Teeth proportion and symmetry  The width of the central incisor should be approximately 80% of its length.  Lateral incisor where the space created is 0.618 of the width of the central incisor.
  • 6. C. The midlines  The facial midline is constructed by joining a line between soft tissue nasion and the midpoint of the upper lip. Ideally, the maxillary dental centreline should be coincident and parallel to this.  Midline discrepancies are not readily noticed unless they are 4 mm off. D. Tooth angulation  Where teeth have tilted and are at an abnormal angulation, the level of the incisal edge may not be at the correct relationship to the facial axis of the clinical crown due to incisal edge wear. Kokich (1993).  Mesiodistal angulation of the midline is more noticeable than absolute discrepancy E. Tooth inclination The inclination of the upper canines and premolars should be upright (zero inclination). Canines with either positive or negative buccal root torque look unattractive. When viewed from a sagittal direction, increased tooth inclination may decrease the amount of incisor display; conversely, decreased inclination may increase incisor display due to lengthening of the tooth as the crown is retroclined.
  • 7. 3. Gingival factors Embrasures, connectors and contacts A. Embrasures are the spaces between the incisal edges of adjacent teeth above the contact pint.  Ideally, embrasures should gradually increase in size from the maxillary central incisors to more distally in the arch  Toothwear can result in elimination of embrasures, which contributes to an aged smile. B. Connectors are the areas between adjacent teeth where they appear to meet below the contact point.  Between the central incisors the connector should measure 50% of the height of the central incisor crown, between the central incisor and lateral incisor it should measure 40% of the height of the central incisor and between the lateral incisor and canine it should measure 30% of the height of the central incisor. This has been terms the 50–40–30 rule.  A poor connector relationship can result from incorrect angulation of adjacent teeth and/or a triangular tooth shape. The latter can be corrected by interproximal enamel reduction followed by orthodontic space closure. C. Gingival contour Kokich and Spear (1997) give four criteria to evaluate during orthodontic treatment: • the gingival levels on contralateral teeth (e.g.: right lateral incisor and left lateral incisor) should be the same
  • 8. • the height of the gingival contour on the lateral incisors should be very slightly lower than on the central incisors and canines • the height of the gingival contour of the central incisors and the canines should be the same D. Gingival levels  Ideally, the gingival margins of the maxillary central incisors and canines should be level while those of the lateral incisors should lie 1 mm more incisal  A number of factors can produce gingival marginal discrepancies: 1. Periodontal disease 2. Attrition 3. Ankylosis in a growing patient 4. Severe crowding 5. Delayed maturation of the gingival margin. Treatment of gummy smile