| Author | Year | Population | Sample Size | Prevalence | Condition | Reason for exclusion |
| Isiekwe, M. [18] | 2003 | Medical, dental students and armed forces of Nigeria | 110 | 20% | Bimaxillary protrusion | Unclear if sample is representative of population |
| Jones Byran [19] | 1986 | Saudi Arabia | 132 | No figure given | Bimaxillary Proclination | The sample was not representative of the population, the participants were not recruited in an appropriate way. The study subjects and settings were not described in detail |
| Boeck, E., et al. [20] | 2011 | Brazil | 381 | 4.09% | Biprotrusion | Used patient with dentofacial deformities and required orthognathic surgery |
| Baeshen, Hosamn [21] | 2017 | Saudi Arabia | 300 | 8.3% | Bimaxillary Protrusion | Did not sample from population but people seeking treatment. Sample was not representative of the target population and study participants were not recruited in an appropriate way |