A common piece of advice for anyone planning veneers is that the front teeth should copy the outline of the face, so a square jaw gets square teeth and an oval face gets oval teeth. When researchers have compared real faces with real teeth, most studies have found little or no match between the two. Face outline can still be part of the conversation, but it is a weak guide on its own, and smile design often leans on other measurements.
Where the idea came from
The theory is usually credited to J. Leon Williams, who in the early twentieth century proposed that the outline of the upper central incisor, turned upside down, mirrors the outline of the face. He sorted both into three broad types, square, tapering and ovoid, and the idea became a widely used guide for choosing denture teeth for people who had no natural teeth left to copy, helped by denture tooth manufacturers adopting the classification. A later idea, the dentogenic theory of Frush and Fisher, linked tooth shape with sex and personality, so that rounded teeth were seen as feminine and squarer teeth as masculine.
Both ideas are easy to explain and easy to picture, which is part of why they still appear in smile design advice. The question is whether they hold up when people are measured.
Most studies find a weak match or none
Researchers have tested the theory in different countries with photographs, casts, tracings and software. Most have reached the same conclusion.
| Study | People studied | What it found |
|---|---|---|
| Bell, Journal of the American Dental Association, 1978 | 31 people; three dentists classified faces and teeth | No correlation between face form and central incisor form |
| Sellen and colleagues, Journal of Prosthetic Dentistry, 1998 | 50 dental students; outlines compared by computer | Tooth and face outlines corresponded in 22% of comparisons; nearly half were dissimilar |
| Ibrahimagić and colleagues, Collegium Antropologicum, 2001 | 2,000 people aged 17 to 24 in Zenica, Bosnia and Herzegovina | The inverted tooth outline matched the face in only 30%; the most common pairing was an oval face with a tapered-square tooth |
| Varjão and colleagues, Quintessence International, 2006 | 160 adults aged 18 to 33 from four racial groups | Tooth and face matched in 23.75% of cases |
| Koralakunte and Budihal, Journal of Oral Science, 2012 | 200 Indian dental students | No highly defined correlation; 31.5% correlation using Williams' method, compared with more than 50% by visual assessment |
| Anees and colleagues, Scientific Reports, 2026 | 153 Pakistani adults aged 18 to 30; outlines measured with AutoCAD software | No significant association between face shape and incisor form |
Not every study agrees. Kostić and colleagues (Medicina, 2023) examined 90 Serbian dental students aged 20 to 27 and concluded that a modified version of the theory, which also considers the shape of the dental arch, held in most of their subjects. Taken together, though, the evidence does not support face outline as a reliable rule for choosing tooth shape.
Even experts disagree on what shape a tooth is
Part of the problem is that the categories themselves are hard to apply. In the Varjão study, three prosthodontists classified the same central incisors as square, ovoid, tapering or a combination, and they agreed in only 30.62% of cases at the first session, when given no instructions, and 24.37% at the second, when told to use Williams' method. Ibrahimagić and colleagues recognised 11 facial forms and 10 tooth forms in their population, although 98% of people fell into three main forms of each, and the most common tooth form was a blend, tapered-square.
Many teeth do not fit neatly into one category. A tooth can have straight sides with rounded corners, or a narrow neck that widens towards the edge, and what you see can also depend on the gum line and how much of the tooth shows when you smile.
Teeth do not reliably signal male or female
The masculine and feminine version of the idea has also been tested. Corbella and colleagues (Journal of Investigative and Clinical Dentistry, 2019) showed 100 standardised intraoral photographs of the front teeth, without the face, for five seconds each to five expert dentists, five non-expert dentists and five people without dental training, and asked them to judge each person's sex. The groups were right 56.0%, 65.0% and 58.6% of the time on average, not far above chance, with no real difference between the groups. Rounded central incisors were linked with women in the photographs, but the authors concluded that sex perception is not strongly influenced by the teeth.
In the Anees study, tapering, ovoid and square teeth were all found in both men and women. A preference for a softer or stronger look is a valid design choice, but it is a preference rather than a rule set by the face.
What a smile design is usually built on instead
Planning the shape of front teeth often also considers features that relate directly to the smile:
- Proportions of each tooth. How long a front tooth is compared with its width can affect whether it reads as square or slender, as explained in our article on tooth width to length ratio.
- The lips. How much tooth shows at rest and when smiling, and how the edges of the teeth follow the lower lip, are covered in our guides to the lip line and the smile arc.
- Age and wear. Worn, flat edges and squared corners may make a smile look older, which our article on tooth shape and perceived age looks at in detail.
- Your existing teeth. When only a few teeth are being changed, the new ones generally need to sit comfortably beside the teeth that are staying.
- What you want. Some people ask for a softer, more rounded look and others for straighter, more defined edges. Our guide on how to describe the smile you want can help you put that into words.
Seeing a shape before committing to it
Because face outline is a poor predictor, the most useful step is often to look at a proposed shape on your own smile. A trial smile, or mock-up, places a temporary tooth-coloured material over the teeth so you can see the length and outline in the mirror and in photos, as described in our article on the smile mock-up. A mock-up is a preview, not a promise, and the final result can differ once the restorations are made.
At Lumi, smile planning uses our clinical photography room and 3D intraoral scanner, and Dr James Tran has completed Digital Smile Design training with Dr Christian Coachman. The tooth shape can then be carried out with porcelain veneers or composite bonding, depending on what the teeth need.
Questions we are often asked
I have a square jaw. Should I avoid rounded veneers?
Not because of the jaw alone. Most of the studies above found that face outline and natural tooth shape often do not match, so a rounded or softened outline may suit a square face if it fits your lips, proportions and preference. A mock-up is a simple way to check.
Can my teeth be reshaped without veneers?
Sometimes. Small changes to corners and edges can be made with composite bonding or gentle reshaping of enamel, depending on the tooth. The dentist would check whether there is enough healthy enamel and how the change would affect your bite.
Is there a single ideal tooth shape?
No single shape has been shown to suit everyone. The studies above found a range of tooth shapes in natural smiles, so shape is usually chosen to fit the person rather than a formula.
Planning a change to your front teeth
If you are thinking about veneers or bonding and want to talk through shape, a free cosmetic consult is available for cosmetic treatment. If you live interstate, you can send photos first, as explained in our guide to travelling to Sydney for dental treatment, before visiting us in Melrose Park.
Sources
- Bell RA. The geometric theory of selection of artificial teeth: is it valid? J Am Dent Assoc. 1978;97(4):637-640. PubMed 363761
- Sellen PN, Jagger DC, Harrison A. Computer-generated study of the correlation between tooth, face, arch forms, and palatal contour. J Prosthet Dent. 1998;80(2):163-168. PubMed 9710817
- Ibrahimagić L, Jerolimov V, Celebić A, et al. Relationship between the face and the tooth form. Coll Antropol. 2001;25(2):619-626. PubMed 11811293
- Varjão FM, Nogueira SS, Russi S, Arioli Filho JN. Correlation between maxillary central incisor form and face form in 4 racial groups. Quintessence Int. 2006;37(10):767-771. PubMed 17078274
- Koralakunte PR, Budihal DH. A clinical study to evaluate the correlation between maxillary central incisor tooth form and face form in an Indian population. J Oral Sci. 2012;54(3):273-278. PubMed 23047039
- Kostić M, Đorđević NS, Gligorijević N, et al. Correlation theory of the maxillary central incisor, face and dental arch shape in the Serbian population. Medicina (Kaunas). 2023;59(12):2142. PubMed 38138245
- Anees R, Chaudhary MAG, Fatima SK. Association between maxillary central incisor tooth form and face shape using digital AutoCAD analysis in Pakistani adults. Sci Rep. 2026;16(1):11627. PubMed 41922439
- Corbella S, Alberti A, Muzzarelli M, et al. Anatomical factors associated with gender recognizability: a study on intraoral standardized photographs. J Investig Clin Dent. 2019;10(4):e12476. PubMed 31617964
This article is general information only and is not a substitute for advice about your own situation from a dentist.
