Some parents in Wales are not brushing their baby's teeth because they do not realise they need to, an expert in dental health has said.
It meant some five-year-olds in Wales were having up to nine teeth removed in one go, Cardiff University's senior lecturer in dental public health said.
Maria Morgan said: "I think people don't realise that you should start that early."
She wants the dental profession to work with midwives to get the message out.
The latest figures show the proportion of five-year-olds with tooth decay in Wales is continuing to fall - from 47.6% in 2007-08 to 34.2% last year.
But chief dental officer, Dr Colette Bridgeman, said the Welsh Government's Designed to Smile programme - which encourages child dental health - would be "re-focusing" on those aged zero to five.
And Mrs Morgan said parents of babies might need more of a nudge.
'It can get left'
"No book can prepare you for life when you have a baby," she said.
"When that lands on your plate with all the different things you have to do and fit in… brushing teeth might not be the highest priority in the day. Sometimes it can get left.
"The messages might not be getting to everybody," she added.
About 14% of three-year-olds have a decayed, missing or filled tooth, Maria Morgan said.
She added: "We are having some children at five, six or seven who are having five, six, seven, eight, nine teeth removed in one go.
"There are some children in Wales who are having teeth extracted under general anaesthetic, that's approximately 8,000 children a year, and while some children will need to have dental treatment delivered that way because of special circumstances, [like] special needs children, it shouldn't be that great a number."
Mrs Morgan said children should have their teeth brushed twice a day "as soon as teeth show in their mouth".
She said it was essential that parents "actively supervised" their children's teeth brushing until the age of seven.
In 2013, Cardiff University asked the parents of 1,400 three-year-old if they brushed their child's teeth twice a day, with 75% saying they did.
Leah Ennis, 29, of Cornelly, Bridgend county borough, is a mum to a three-year-old and a three-month-old.
When her eldest was six months old her health visitor gave her a pack that included a baby toothbrush and toothpaste but she said she received no instructions on how to use them. So far, no-one has mentioned dental hygiene for her youngest, she said.
"Growing up I was shown good dental hygiene that I can pass onto my children but not everyone is," she said.
Miss Ennis said there was a lack of information and she was "not surprised" to hear some parents were not brushing their baby's teeth.
"Pregnant women could be given this information through pregnancy [but] I didn't see anything up on the wall in hospital waiting rooms - that would be a good place to start. I had no information from midwives," she said.
"If parents aren't told they're not going to go and look for the information."