It is widely accepted that teeth as well as the tongue and lips play an important role in speech production, however, the relationship between occlusal anomalies and articulation defects still remains controversial. Scientific investigations in this area are complicated by many factors such as the inability to use animal experiments, variety of classifications and methodologies to identify malocclusions and articulation disorders, different linguistic populations and presence of many compensation mechanisms.
This article presents a review of earlier publications that have attempted to find association between malocclusions and articulatory speech disorders. The occlusal anomalies found to be in stronger association with speech distortions are C III, incisal open bite, space excess in the maxillary anterior region (diastema, spacing) and lateral crossbite. Speech disorder does not seem to correlate with the severity of malocclusion. No certain articulation disorder can be related to C II occlusion, deep bite, lateral open bite or scissors bite.
The speech sounds most often affected by changes in the articulation apparatus are /s/, /r/, /l/, /t/ and /n/. Sigmatism is the only speech disorder that can be directly associated with negative overjet and anterior open bite.
Malocclusions causing changes in the position of the tongue and the hyoid bone (skeletal C III and open bite) lessen the size of the posterior oral cavity and are hence considered to be risk factors for producing articulation disorders. The same applies to occlusal anomalies that change either the size or shape of the anterior oral cavity (spacing in the maxillary anterior region and lateral crossbite, caused mainly by maxillary constriction).