The size of the teeth can be determined by the actual size of the teeth or by the teeth not having fully erupted(too much covered by the gums).
To change the gum height, a gingivectomy can be done. This can be achieved by surgical means for more severe cases or, more typically, by just reshaping the gums. The results tend not to be completely stable so placement of dental veneers on the teeth will allow for long-term stability.
The size of the teeth also depends on whether it is developmental or whether the teeth have worn out. Both can be corrected easily with dental veneers. However, in the case of abnormal wear, the causes do need to be managed.
For your information, there is a recorded webinar on Dental Veneers on this website that you may find useful. https://www.human.com.sg/dental-veneers-dr-kevin-ong
