Dental Esthetic Research

Smile arc with gingival display

Dental Esthetic Research


Smiles are important both socially and professionally! This page goes into the research behind an attractive smile and what we use when designing dental veneers.

Image of What people notice first when they meet someone

Top 5 reasons that smiling is so important!

The simple act of smiling can do so much for you. Check out these 5 reasons to show off those pearly whites! Go ahead, give it a try!

  1. You will live longer!  Smiling has real chemical effects on your body – even if you are faking it!
  • Studies have found smiling will lower your heart rate, steady your breathing, and relax your body; which results in a stronger immune system.
  • It will make you happier by releasing serotonin (fake smile or not)
  • Lowers blood pressure by releasing endorphins = “natural high”
  1. Appear more attractive and trustworthy to those around you.  Another bonus is that psychological research has shown that attractive people are perceived as more successful, intelligent, and friendly.
  2. Appear younger!  Smiling is a natural face-lift!
  3. Be more memorable.  Studies have shown you are 3x more likely to be remembered if you are smiling than if you display a negative or neutral face.
  4. Be more successful!  The previous three effects lead to promotions and more yes’s from others.

Famous smile quotes

A quote from my all-time favorite book, “A smile costs nothing, but creates much.  It enriches those who receive, without impoverishing those who give.  It happens in a flash and the memory of it sometimes lasts forever.”  Dale Carnegie

General rules for esthetic dentistry.

Take photos of smiles for posting slightly superior – those and straight on favored over inferior view This may be due to fact as go higher the smile can appear to change from reverse to straight to parallel.  When patients look at themselves in mirror they get top view (good thing).  When hold mirror, should hold straight or below to give straight or top view.

At rest 2 plus/minus 2 D Bauer
2-4mm central show at rest Hornbrook

RULE of 42.2 4mm central show at rest and within 2mm lower lip  2mm most gingiva show at smile

Systemic review of laypersons perspective of a frontal smile

How the layperson sees our work is what really matters so these are stats to know. Several thresholds exist according to Parrini AJO 2016.

  • Diastema 0-2mm
  • Midline discrepancy up to 3mm
  • Buccal corridors from 5-16mm
  • Gingival exposure from 1.5-4mm
  • Occlusal cant up to 4 degrees
  • Overbite 2-5mm

Research on the esthetics of smiles and dentistry.

For men the gingva level of the central can be up to .5-1mm below the canine with a 1-2mm step up to the lateral for incisal lengths. Menezes and later Simões AJO 2019

Spacing always looks better farther back ie if midline space try to move it to distal laterals Noureddine 2014 J Pros Dent

Burcak 2013

Smile arc with zero gingival display
Smile arc 5 with 0 mm of gingival display = fav ortho and DDS
Smile arc with -2mm gingival display
Smile arc 3 with −2 mm of gingival display = fav or layperson
  • Flat smile arcs preferred when lacking gingiva show
  • Vaulted smile arc preferred when excessive giniva show

Springer 2011 Laypersons

  1. With the lower-face view: ideal smile arc, ideal buccal corridor, maximum gingival display, upper to lower midline, and occlusal cant important.
  2. The principle of tracking the curve of the lower lip was confirmed, even though lip curvature varies.
  3. For the full-face view, the raters preferred less maximum gingival display, less buccal corridor, more upper to lower midline discrepancy, and less cant of the occlusal plane.

McLeod 2011 Regional discrepancies exist Canada more discriminating to deviations from norm than US

Research from 2000-2010

Bukhary 2007 British study

  • Slighter wider than golden proportion 62% for laterals preferred 67% then 72%
  • Lateral 1-1.5mm shorter than central preferred

Rosenstiel 2002 Web based laypersons

  1. Strongest preferences concerned diastema and midline shift
  2. Weakest concerned whiteness and proportion.
  3. The largest minority view was the straight embrasures.
  4. Females had stronger preferences in all conditions.
  5. Respondents younger than 40 years of age had stronger preferences for whiteness and against diastema
  6. Whites strongly rejected the diastema.

Parekh 2006 Orthodontists and laypersons

  1. Minimal buccal corridors are favored by layperson
  2. Significantly lower attractiveness ratings were found for flat smile arcs and excessive buccal corridors.
  3. Flattening of the smile arc overwhelms the deleterious effects of excessive buccal corridors on attractiveness ratings. (So arc more important than buccal corridor?)

Sharma 2010 Little ethnic difference in the perception of smile esthetics, except for buccal corridor and smile arc

Dental Research pre 2000


Kokich 1999  Laypersons v dentists v ortho

  1. Max central must be 2mm shorter for layperson to notice
  2. Laterals have to go 4mm skinnier before layperson notices (lots wiggle room)
  3. Midline can shift at least 4mm before layperson notices (lots wiggle room)
  4. Gingival embrasure can go only 2mm before layperson starts to notice
  5. At least 2mm of gingival discrepancy on laterals is unnoticed
  6. Takes 3mm of cant to notice BUT only the front 6 had cant
  7. 2mm covering up to 4mm fine for smile height

Husley 1970  Orthodontists I believe

  1. Orthodontically treated subjects had significantly poorer smile scores than the subjects with “normal occlusion.”!!!!
  2. Arcs of curvature of the incisal edges of the upper incisors and the upper border of the lower lip important.
  3. The smile symmetry ratio was important
  4. The buccal corridor ratio appeared to be of no significance to an attractive smile.
  5. Most attractive smiles having average lip height
  6. Upper lip curvature was most desirable when the corners of the smile were above the midline of the upper lip. However, those smiles in which the corners of the smile were below the midline of the upper lip were attractive if they possessed the most desirable relationships of each of the other components.

Tjan 1984

  1. Smile – High 11% average 69% low 20% women tend to be higher
  2. Parallel 85% straight 14% reverse 2%
  3. Incisal edge above lower lip 35% (more men) touches 47% (more women) covered 16%
  4. 6 teeth displayed 7% 8(49%) 10(41%) 12 (4%)
  5. Patents use upper lip to find midline (that and diastema most important)

Dong 1999 Korean study

  1. Laypeople preferred PM2-PM2 smiles.

Gracco 2006 Italy

  1. Full, broad smile with minimal “buccal corridors” seems to please dentists as well as laypersons and age and gender were not relevant.
  2. BUT a significant percentage also preferred the largest buccal corridor offered, so again personal preference

Moore 2005 Iowa – minimal buccal corridors is a preferred esthetic feature

Ioi 2012 Japan and Korea prefer minimal buccal corridor but again all over the map

15% buccal corridor was seen as most esthetic according to Nimbalker JPD 2018. My only issue is the people choose the middle option which may not be a coincidence.

Buccal corridor research pre 2000

Frush and Fisher 1958 Denture article with esthetic terms

  1. “There are two worlds; the world we can measure with line and rule, and the world that we feel with our hearts and imagination.“-Leigh Hunt.
  2. The buccal corridor creates an added illusion of reality. If buccal corridor completely filled, ie the “molar to molar smile” = characteristic of a denture.