Adolescence is a transitional life phase, with imprecise boundaries between childhood and adulthood. It is defined either by age, by stage of development, or by functionality. Related terms include "tweens," "teens," "youth," "young people," and "young adults." It is characterized by physical, emotional, social and behavioral changes, as well as identity formation and increased independence. It is also strongly influenced by social, cultural, economic, and physical elements.

There is not a single scientific definition of adolescence or set age boundary. The age span can range from 10 years (when pubertal changes occur) to 24 years (adopting a full range of adult responsibilities). We will use data presented by the National Research Council and classification from the Institute of Medicine (IOM), which defines the following age ranges:

• Adolescents: ages 10-19
• Young adults: 20-24

In the US, 1 in 7 people (14%) are adolescents and 1 in 7 (14%) are young adults (US Census).

Within these populations, there is significant diversity and sub-populations that have unique health needs and concerns. Certain groups are particularly vulnerable to poor health, including oral health. These groups include:

• More than one third of all adolescents (35%) are racial or ethnic minorities
• Nearly 40 percent (38%) come from poor or low income households
• 1 in 5 (19%) live in a rural area

This portion of the adolescent population is increasing.

Approximately 2.5 million adolescents are not US citizens (US Census Bureau, 2005). Within your dental practice lifetime, you can expect that nearly 1 in 5 Americans (19%) will come from an immigrant family.

In the US in 2009, over 14 million arrests were made. 2,086,500 of these, or almost 1 in 7 (14%), involved an individual under age 18. 

There are about 92,854 youth residing in juvenile detention and correctional facilities. These youth, detained or incarcerated by the justice system, have a variety of medical and emotional disorders and are, for the most part, medically underserved.

While difficult to determine, it is estimated that there are 1 - 2 million homeless adolescents in the US. Homeless youth are more likely to:

• Experience sexual or physical abuse
• Be in danger of victimization
• Suffer from mental health disorders
• Adopt risky behaviors
• Find barriers in accessing health care and oral care

In 2005, there were over 3 million reports of alleged child abuse and neglect, involving 6 million children and adolescents.

Over half a million children and adolescents are in the foster care system. Children and adolescents in foster care suffer from significantly more health problems than the general population. These include:

• asthma
• anemia
• dental caries
• neurological abnormalities
• dermatological disorders
• malnutrition

LGBTQs comprise up to 40% of the homeless and runaway population. They are also more likely than other homeless youth to engage in a number of practices associated with health and oral health problems including:

• substance abuse
• survival sex
• risky sex practices
• eating disorders

Many LGBTQ adolescents endure rejection, ridicule, harassment, social isolation, and discrimination.