Causes of Excess Overjet
In restorative dentistry, ideal is an excellent target but compromise is usually our reality when it comes to problematic occlusal cases. A compromised occlusion is something we see rather frequently as restorative dentists – all presenting in many different varieties. A common variation from ideal is excess overjet, often leaving an anterior open bite. When we think about treating patients with this type of occlusion, it’s helpful to know what can potentially cause excess overjet.
Skeletal relationships: When the mandible is deficient in its growth relative to the maxilla (Angle Class II) there will commonly be excess overjet. Generally the first molar and canine relationships can be used to assess skeletal development; however, it must be remembered that many patients may posture their mandible forward disguising the underlying skeletal condition. If indeed there is a skeletal deficiency a solution could involve orthognathic surgery to advance the mandible forward.
Arch length problems: In this example the excess overjet is caused by any condition which makes the maxillary arch longer than the mandibular arch, or conversely the mandibular arch shorter than the maxillary arch. One example could be missing teeth in the mandibular arch, such as congenitally missing mandibular second premolars; this creates a lower arch that is too short compared to a maxillary arch that has no missing teeth.
Another example may be retained maxillary second primary molars; they have a mesial distal width greater than the permanent premolars that should be present. This creates a long maxillary arch compared to a mandibular arch with a normal compliment of permanent teeth. When problems of arch length cause excess overjet a common solution is to shorten the maxillary arch or lengthen the mandibular arch.
Tooth inclination problems: When it comes to this issue, excess overjet can be caused by two different problems; either the maxillary anteriors are proclined or the mandibular anteriors are retroclined. In either case, the inclination can be corrected with orthodontics to reposition the teeth, eliminating the excess overjet.
For a detailed look at occlusal guidance patterns, history and research, view our free lesson: Understanding Occlusal Guidance.