This study will take place in Egypt. Undergraduate students from different faculties of the Egyptian Universities will participate. The study began in December 2020.

Matching criteria and allocation ratio: The planned study a single arm cross sectional study, in which the prevalence of students of TMD will be reported. The association between TMD and other variables will be also studied. Therefore, no matching criteria or allocation ratio are required.

Variables It has been shown from literature that many variables are associated with TMD. It was therefore, decided to study the correlation between these variables with TMD among Egyptian population via a regression model once the assumption for regression analysis are satisfied. Binary variables are analyzed through logistic regression, while continuous data through a multivariable regression analysis. If one of the assumptions for regression analysis is violated, a subgroup analysis for each variable will be considered.

These Variables include gender, age, psychological stress, oral habits, parafunctional activities as gum chewing, previous dental treatments , previous trauma to jaws.

Data sources and management Data sources, the answered questionnaires and subsequent spread sheets will only be shared by the team members.

Addressing potential sources of bias Selection bias: an email will be sent to all the students through their university email addresses. Due to the COVID-19 situation only convenient sampling could be used. whenever possible printed questionnaires are handed to the students.

Quantitative variables: Handling of quantitative variables in the analyses None of the data is a continuous variable. All exposure factors are binary or categorical data. Therefore, no plans are set for simplifying continuous data or converting them into binary ones.

Inclusion Criteria:

1. -Undergraduate students in Egyptian universities
2. Age ranges from 18-45 years
3. Males and females

Exclusion criteria

1. school students
2. students not living in egypt

All undergraduate students in Egyptian Universities