[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Dentistry](https://durgical.com/en/dentistry/) › [Caries, pulp and tooth wear](https://durgical.com/en/dentistry/areas/caries-pulp/) › How caries forms: biofilm, sugar and demineralisation # How caries forms: biofilm, sugar and demineralisation - Oral pathology Caries is not just a hole: it is a slow, reversible loss of mineral caused by acid from bacteria feeding on sugar. Early lesions can heal. Updated Nov 12, 2026 ## Key points - Caries = bacteria + sugar + susceptible tooth + time. - Frequency of sugar matters more than amount. - White spots can remineralise; cavities cannot. ## What it is Dental caries is a disease of the biofilm driven by diet. Bacteria in plaque (mainly mutans streptococci and lactobacilli) ferment sugars into acid. When the pH at the tooth surface falls below about 5.5 the enamel loses calcium and phosphate (demineralisation); when the acid is cleared by saliva, mineral returns (remineralisation), helped by fluoride. Caries develops when demineralisation wins over time. The first sign is a chalky white spot that can still remineralise; once the surface collapses into a cavity, the lesion progresses into dentine and towards the pulp. Caries is the most common disease in the world (WHO). ## How to recognise it - Four ingredients: a susceptible tooth, cariogenic bacteria, fermentable sugar and time. - How often sugar is eaten matters more than the total amount: each intake drops the pH for twenty to thirty minutes. - Pits and fissures of molars, the areas between teeth and the gum line are the common sites. - White spot lesions are reversible with fluoride and hygiene; cavitated lesions need restoration. - Root caries affects older adults with recession and dry mouth. ## Differential and risks - Untreated caries leads to pulpitis, pulp necrosis, abscess and spreading facial infection. - High caries risk: frequent sugary snacks and drinks, low fluoride exposure, dry mouth, previous caries, poor hygiene, orthodontic appliances, and low socioeconomic status. - Sudden widespread caries in an adult suggests reduced saliva (drugs, radiotherapy, Sjögren disease) or diet change (sweet drinks, eating disorders). ## Next step / Initial management - Advise brushing twice daily with fluoride toothpaste, limiting sugar to mealtimes and avoiding sweet drinks between meals. - White spot lesions: fluoride varnish and hygiene; review with the dentist. - Cavities, pain, or any caries in a child or pregnant woman: refer to the dentist for treatment. - Rampant caries: look for dry mouth, diet and eating disorders, and refer. ## Test yourself Think of the answer, then tap the question to see it. ## Below which approximate pH does enamel begin to demineralise? About 5.5. ## Why is frequent snacking on sugar worse than the same sugar eaten at one meal? Each intake keeps the plaque pH low for twenty to thirty minutes, so frequent intakes leave little time for remineralisation. ## What is the earliest visible sign of caries and can it heal? A chalky white spot on enamel; it can remineralise with fluoride and good hygiene. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/dentistry/how-caries-forms-biofilm-sugar-and-demineralisation/) ## Connections ## Related 5 - [Classifying caries: by site, depth and activity](https://durgical.com/en/dentistry/classifying-caries-by-site-depth-and-activity/) - [Early childhood caries](https://durgical.com/en/dentistry/early-childhood-caries/) - [Preventing caries: fluoride, sealants and diet](https://durgical.com/en/dentistry/preventing-caries-fluoride-sealants-and-diet/) - [Saliva and the oral microbiome](https://durgical.com/en/dentistry/saliva-and-the-oral-microbiome/) - [Pulpitis: reversible or irreversible](https://durgical.com/en/dentistry/pulpitis-reversible-or-irreversible/) ## Related conditions 1 - [Dental caries](https://durgical.com/en/conditions/dental-caries/) ## In Pharmacology 2 - [Fluoride](https://durgical.com/en/pharmacology/fluoride/) - [Chlorhexidine](https://durgical.com/en/pharmacology/chlorhexidine/) [← All of dentistry](https://durgical.com/en/dentistry/) Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once. Sources: [Dental Caries](https://www.ncbi.nlm.nih.gov/books/NBK551699/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Tooth Decay](https://www.nidcr.nih.gov/health-info/tooth-decay) (National Institute of Dental and Craniofacial Research (NIDCR, NIH), 2024); [Oral health](https://www.who.int/news-room/fact-sheets/detail/oral-health) (World Health Organization, 2026); [Dental cavities](https://medlineplus.gov/ency/article/001055.htm) (MedlinePlus, US National Library of Medicine, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/dentistry/how-caries-forms-biofilm-sugar-and-demineralisation/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/dentistry/how-caries-forms-biofilm-sugar-and-demineralisation/