Maximum mouth opening. Associated factors and dental significance

To estimate active maximum mouth opening (AMMO) in a Jordanian subpopulation and to study associated factors and relationship to patient's dental conditions.

This cross-sectional study was conducted on 496 patients aged 15-80 years at the University of Jordan Hospital, Amman, Jordan between October 2008 and March 2009. The AMMO was measured as maximum distance between incisal edges of upper and lower central incisors. Descriptive statistics and uni- and multivariate analyses were used to determine factors affecting AMMO.

Mean AMMO +/- standard deviation was 42.9 +/- 5.7 mm. The AMMO varied significantly between men (45.3 +/- 5.7 mm) and women (41.5 +/- 5.3 mm), decreased with age, and correlated positively with body height and weight, but no relation was found with body mass index and temporomandibular joint complaints. The relationship of AMMO to patient's dental conditions revealed a negative correlation with number of missing teeth, but not with number of decayed or restored teeth. Subjects who had present third molars had wider AMMO compared to subjects with extracted, impacted, or congenitally missing third molars. Multivariate regression analysis revealed gender, age, and weight to be the only independent predictors of AMMO.

In this population, AMMO is influenced by gender, age, and weight of patients and was generally narrower than that reported in European populations. Wide AMMO was associated with less risk of tooth loss and preservation of third molars.