Retained deciduous teeth is not a common thing beyond the age of 12yrs which is normal for permanent dentition after that age.
In your case you could go for Xray in the region of retained deciduous teeth and look for root condition, also mobility of teeth and if the deciduous teeth are not mobile with no signs of root resorption-which happens when there are permanent teeth below erupting to replace deciduous teeth, as in your case the patient says permanent teeth are missing below the retained deciduous anterior teeth in the lower arch middle tooth region.
Next Steps
Suggestable treatment plan -to go for crown preparation and suitable crown over the deciduous teeth which are retained to improve asthetics-as is the patient complaint for
Health Tips
Deciduous teeth with crowns