Fruits are promoted as a good source of nutrients but the high sugar content could have negative effect. 

A recent study by Fridell evaluated 30 participants in Norway that supplemented their diets with either extra fruits or extra nuts at +7 kcal per kilogram body weight for 2 months.

Here are the findings:

The number of participants with deep gum pockets ≥ 4mm was reduced in the FRUIT group compared to the NUT group. Despite the high sugar content, fruit intake had a favourable effect on gum health likely due to the protective micronutrients they contain. Fruits are a nutrient source that is rich in vitamins, antioxidants, and fibre, and this appears to counteract gum inflammation. 

Fridell S, Ström E, Agebratt C, Leanderson P, Guldbrand H, Nystrom FH. A randomised study in young subjects of the effects of eating extra fruit or nuts on periodontal inflammation. BDJ Open. 2018 Jan 5;4:17022. doi: 10.1038/bdjopen.2017.22. PMID: 29607092; PMCID: PMC5842821.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5842821/