According to a study in the Journal of Dental Research more than 2.4 billion people worldwide have untreated tooth decay.
Experts are alarmed at the extent of the global issue which affects both adults and children. In the UK alone, a third of the population have untreated decay. In Lithuania it is over two thirds.
Tooth decay is a process which occurs over time as bacteria, which use sugars and starches in foods to create acids, cause infection. The cumulative effect of these acids can lead to cavities in teeth if not counteracted by minerals in saliva, e.g. calcium and phosphate, or fluoride from various sources, which can help the enamel repair itself.
Demineralization and remineralizaion occur all day long. Decay is preventable. But too many sugary foods and drink and frequent snacking allow the bad guys to dominate and then only dental treatment can help.
In some populations the news is better. In the USA, there has been the first drop since 2007 regarding untreated tooth decay amongst children. Although still 10%, it is the lowest percentage for 25 years. This also includes a reduction in the percentage of cavities which is directly affected by sugary drinks and snacks. This could be a result of pediatricians being trained to encourage parents to bring their child to the dentist before their first birthday. However, improvement in behaviours which can cause decay is very important. Technology has been useful here, e.g. iPads are being used by health workers with a program called MySmileBuddy which helps parents create behaviour plans to help prevent the decay process.
There are lots more apps now to encourage good brushing habits. Check in App Store or Google Play, depending on device.
Here'a a fun, free App called BrushDJ - it plays 2 minutes of a song from your device to for you to brush to plus advice and reminders for all age groups.
Read more in this BBC article Billions have untreated tooth decay, and here in this New York Times article Untreated dental decay is falling among children.