Scientists have developed a test that can determine if a child has autism by looking at their baby teeth. 

The research takes a closer look at how children metabolize metals, which is critical to neurodevelopment in early life.

As a child grows, a new layer of tooth is formed every day based on the chemicals circulating in that child's body, similar to growth rings on a tree. So, these scientists looked at a study of baby teeth in Sweden involving 200 twins. Those researchers used a laser to test whether zinc-copper cycles were different in those with autism and they were. The study was then done again in the U.S. and U.K. 
    
From that data, the scientists developed an algorithm that is 90 percent accurate in distinguishing between teeth of children with autism and without. The authors published their findings in the journal Science Advances. 

Currently, a biochemical test does not exist for autism. Doctors diagnose the disorder using clinical assessments and observations. But since children lose their teeth too late for this test to be helpful, experts say this is just one step toward an end goal. 

"They're hoping that future work would look at developing some type of prenatal or blood assay to be able to essentially look at, ok, we can expect possibly autism from this test," Dr. LaQuia Vinson, Riley Hospital for Children pediatric dentist, said. 

If parents can find out earlier their child may have autism, doctors can begin intervention and know sooner about any medical conditions commonly associated with autism. 

Teeth actually begin to form as early as four weeks in utero, so dentists and doctors say they can be a very good indicator of a child's health history. 

There are some developmental and behavioral warning signs for autism parents can look out for, according to HelpGuide.org. 

Your baby or toddler doesn't:

• Make eye contact, such as looking at you when being fed or smiling when being smiled at
• Respond to his or her name, or to the sound of a familiar voice
• Follow objects visually or follow your gesture when you point things out
• Point or wave goodbye, or use other gestures to communicate
• Make noises to get your attention
• Initiate or respond to cuddling or reach out to be picked up
• Imitate your movements and facial expressions
• Play with other people or share interest and enjoyment
• Notice or care if you hurt yourself or experience discomfort