Dental caries persists as one of the most prevalent chronic illnesses and is expensive to treat. 1 In 2015, untreated dental caries in primary teeth alone affected 573 million children worldwide. 2. Complications brought by dental caries in children include not only pain, but also detrimental effects on their growth, general health and wellbeing. 3,4 Other than the substantial healthcare costs associated with managing and treating dental caries, countless school and work hours have been lost due to constraints caused by the consequences of the disease. 3,5 Globally, the estimated productivity losses due to the untreated primary caries were over USD1.7 billion in 2015 around the world. 6

Caries is not evenly distributed in the mouth but displays a characteristic pattern, indicating that some tooth surfaces and tooth sites might be more susceptible to dental caries than others. This understanding of caries pattern was primarily established before the year 2000. 7, 8, 9, 10, 11, 12, 13 Among three-year-old children, caries was predominantly concentrated in the maxillary incisors, while primary molars were less affected as they have only recently erupted into the oral cavity. 11 Among five-year-old children, occlusal caries in primary second molars were found to surpass other primary teeth in terms of prevalence. 12 Furthermore, different tooth surfaces exhibit varying levels of susceptibility to caries. 13

Other factors, such as, race, socioeconomic status, dietary habits and oral hygiene behaviors may also affect caries pattern and disparities related to caries. Children who come from families of a lower socioeconomic status and those who did not receive regular oral care were found to have more dental caries than their peers, regardless of the susceptibilities of the tooth surfaces. 14, 15, 16 Children with exclusive and prolonged bottle-feeding were reported to have significantly more extensive caries in the upper anterior teeth. 17,18

In the 21st century, dentistry has undergone a transformative shift towards patient-centered, technology-driven, outcome-focused, and prevention-oriented oral healthcare delivery. 19 This shift has brought substantial benefits for individuals, healthcare providers, and society as a whole. Moreover, the increased accessibility of care through remote and mobile technology has played a significant role in reshaping the oral healthcare system. This, coupled with a growing awareness of oral health and its importance, has led to the implementation of preventive measures such as water fluoridation, the use of fluoridated dentifrices, and sealant placement. 20, 21, 22 As a result, the overall prevalence of caries has considerably decreased in developed countries over the past few decades. 23 Given these improvements and advancements, it is likely that the caries pattern has also undergone changes in the 21st century.

However, the impact of increased awareness, changes in feeding habits, and preventive measures on the caries pattern is still not fully understood. It is still equivocal whether the pattern of caries has changed in the 21st century. Additionally, understanding the pattern of decay in primary teeth in modern times, under the influence of socioeconomic factors would allow for the implementation of more cost-effective preventive measures and policies for managing the disease.

Therefore, the aim of this systematic review and meta-analysis was to describe and evaluate the caries patterns among the 21st century preschool children globally.