What are some of the biologic reasons why teeth are too short?
Naturally, our genetics determines the size of our teeth. Some people just have small, short teeth. This may be appropriate for their face and their smile.
Even if the teeth are or were of relatively normal length, they can appear short for a number of reasons. These could be altered active eruption, altered passive eruption, incisal wear (with or without compensatory eruption) and the result of habits which interfered with normal eruption.
Active eruption is the movement of the crown of the newly formed tooth through the bone and into the oral cavity to a point where the crest of bone is approximately 2 mm below the CEJ. In some cases, the crest of bone remains at or close to the CEJ. This leaves the gingival crest closer to the incisal edge.
Passive eruption is the movement of the gingiva in an apical direction from the incisal edge as the tooth emerges into the oral cavity to a point where it is approximately 1 mm incisal to the CEJ. Failure of this process is often due to the patient's occlusion or patient habits or altered active eruption, as mentioned above.
For various reasons, some people wear away the enamel edges of their teeth and eventually even the dentin below. In most cases, as the tooth structure is worn away the teeth continue to erupt so that the teeth remain in contact with the opposing dentition. This is an ongoing process unless steps are taken to prevent it.
Finally, a tongue or finger or foreign object habit in the formative years can prevent the natural process of eruption from occurring.
All of the above can lead to teeth that appear short even though the actual biologic crown (the length of the enamel from incisal edge to CEJ) may be or have been of normal length. Once one has determined the reason for the short teeth, one can then move on to resolve the problem with the correct surgical technique if needed and one can design the case to be successful for the long term. More about this in the next article.