"Economic times became tougher for people, and processed food became so much more readily available," Mrs Dewson said.
"These days, children's teeth are constantly under an acid attack."
Mrs Dewson said one initiative that had a positive effect on children's oral health was Fruit In Schools, which was introduced to high-needs schools in 2006. The scheme is now optional for decile one and two primary and intermediate schools.
Mrs Dewson said some schools in Wanganui were no longer taking part and there had been a marked difference in the state of the oral health in children at those schools.
"When kids were eating a piece of fruit every day their teeth were cleaner, they had less plaque, and they were generally healthier. Every day they were having a fruit break, which meant that was one break a day they weren't picking up a muesli bar or a chocolate biscuit."
Mrs Dewson said some people thought fruit wasn't good for teeth because it contained sugar, that wasn't necessarily the case as "the sugar found in fruit is a much better, more natural kind of sugar, and eating fruit produces saliva, which is beneficial for dental health".
Some fruit was better than others. An apple was better than a banana, for example, because bananas can be sticky, she said.
However, fruit wasn't the only answer, children also need to clean their teeth everyday with a fluoride toothpaste.
"Unfortunately, in low socio-economic communities there is often a culture of not cleaning your teeth," Mrs Dewson said.
She noted it was easier for poor families to buy groceries that were bad for their children's teeth, such as fizzy drinks, chippies and biscuits because they were cheaper than fruit and vegetables and often on sale.
"However, there's a lot of work to do with privileged families, as their diet can be just as full of processed foods," she said.
Mrs Dewson said she was particularly concerned by the teeth of 5-year-olds.
In 2011, over the 5-year-old population as a whole, 53 per cent were decay-free, compared to around 60 per cent nationally. By the time children finished intermediate school, Wanganui was almost on a par with the national figure.
"It's much easier for us to see the children once they are at school. We are able to use the tools available to us, such as fluoride varnish and fissure sealants, to help protect their teeth," Mrs Dewson said.
There was a strong push for dental staff to see children at a very young age - five months was ideal - in order to try and educate their parents on the best foods to feed their children once they start taking solids.
"The younger we can get to mum and baby, the better. We're also collaborating with midwives and practice nurses so we're all speaking the same language about dental care."
Despite the high amount of decay, Wanganui's statistics are slowly improving.
"I am hopeful that things will continue to improve. We have 99 per cent of primary and intermediate school children enrolled with us now, and that's a good start," Mrs Dewson said.
