Straight teeth - What should they look like?
Do you feel that your understanding of the term “straight teeth” is incomplete? You’re not alone because most people focus on what is visible when you smile and that is usually the front six teeth!
Straight teeth should be assessed on the basis of 32 adult, healthy, working teeth arranged correctly in the upper and lower jaws. The relationship between all teeth, adjacent and opposing, within each jaw should be harmonious and aesthetic. Everybody cannot conform to the ideal or perfect ‘dental arrangement’ because of differences in tooth shape, size, bone structure and racial characteristics. However, aesthetic professionals agree that there is no ‘normal’ because of this variability! When analysed from different viewpoints there are some key features that need to be demonstrated for your orthodontist to be satisfied that your teeth are straight. Here we lay them out for you in plain language.
What should it look like when viewed from the front?
 | In the diagram, the midline (the dashed blue line) between the two middle upper and lower front teeth should coincide. Preferably this dental midline should coincide with the centre-line of the face. There is an aesthetic zone (in the green box) which falls between the canines and the smile zone includes all the teeth that appear within the lips when you smile. All the teeth that appear in both zones should be in a balanced relationship with each other. Contrary to popular belief, the biting edges of the teeth need not be straight, it is perfectly natural for your teeth to form a contoured pattern, such as illustrated by the red line. The presence of this contoured pattern enables us to distinguish between somebody who is wearing machined dentures or ill-designed veneers and somebody with a natural look. The ideal relationship between the upper front teeth should be stepwise with the central (1) and lateral incisor (2) and canine(3) at different levels. |
What they should look like from the top or bottom?
 | The two curved lines drawn over the teeth should be balanced and symmetrical arches in an ideal scenario. However, this is not achievable in everybody due to differences in tooth sizes, shapes and bone structure. |
What should it look like from the side?
 | When teeth are viewed from the side there should be an obvious cog-like arrangement, in the same way gears fit together. This aspect of straightness is an indication that your teeth can function properly when you bite together. |
What is overbite?
 | When your teeth are together the upper teeth should overlap the lowers - this defined as overbite. In a perfect smile, the upper teeth should cover no more than 30% of the lowers (the difference between the red and green line). If your teeth meet on their edges, they will wear down rapidly (reduced overbite and attrition). Deep bite occurs when your teeth overlap too much causing injury to the gums and teeth. |
What is overjet?
 | Overjet, is the extent to which the front top teeth protrude past the lower front teeth. This is represented by the arrows on the diagram. Preferably, overjet should be between 2 to 4 mm, however this can differ depending on the extent to which your jaws grow. Observe the diagram to see that the upper and lower front teeth stick forwards slightly, this is important because they provide a surface on which the upper and lower lips rest (lip support). Both overjet and overbite are important for the scissor action which we use when eating. In conclusion, the orthodontic term “straight teeth” encompasses all these features discussed. |
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