Dentists are warning parents that bad bottle-feeding practices can damage and even rot their children's teeth.
The New Zealand Dental Association says dentists report babies and toddlers being brought in with decayed teeth because of bottle-feeding misuse.
In some cases the damage is so severe the teeth have to be removed.
The association's oral health educator, Deepa Krishnan, said some parents were bottle-feeding their babies the wrong way.
Bad practices included parents applying honey or sugar on the bottle teat to encourage the child to drink.
Another was bottle-feeding children to sleep and then letting the child hold the bottle the whole night, sucking on the teat while asleep.
Bottle-feeding for long periods would ultimately affect the growth and development of a baby's teeth, as the teat was pushing the top front teeth forward, Ms Krishnan said.
"We don't recommend bottle-feeding at all. A good practice is to go from breast to cup. But if mum is unable to breastfeed, then the bottle should be used but never given to the child to use the whole night."
The same goes for pacifiers.
"What's worse is if [parents] dip it in honey. Others do that with bottles too. The best thing to do is don't dip it in honey or sugary things. The problem is that the child starts to get used to the sugary taste. So we say, 'Why start a problem like that?"'
Parents in Australia are being urged not to bottle-feed children to sleep after a hospital saw a large increase in the number of children coming in with rotten teeth.
The same is happening here.
Specialist paediatric dentist Dr Yaso Ramadas said the Auckland District Health Board paediatric dental service received up to 30 referrals a week of children who had rotten teeth or dental problems.
They had been referred by the regional school dental service, she said, and their treatment required a general anaesthetic.
On bottle-feeding, Dr Ramadas said parents were still giving their children sugary drinks.
"In preschoolers there appears to be an increased frequency of children being put to bed with sweet drink - often in bottles - which leads directly to decay and the requirement for major dental treatment."
Dr Ramadas said sugars from carbohydrates in milk and juice, even if unsweetened, caused acid to form on the teeth which resulted in damaged or rotting teeth.
"This is preventable and the ADHB recommends that children go to bed with clean teeth and water, should a bottle be required."
* If possible, avoid bottle-feeding altogether and go from breast to cup.
* If bottle-feeding is necessary, use only expressed milk or infant formula.
* Do not put sweet drinks in the bottle.
* Hold the baby while bottle-feeding and avoid propping or putting the baby to bed with the bottle.
* If bottle-feeding, avoid using a bottle after 12 months of age.
* Do not put honey or sugary substances on the teat of the bottle.
Source: NZ Dental Association