Your concerns are valid.
According to standard infection-control guideline
1)Dental handpieces are classified as critical/semi-critical instruments and must be heat-sterilized (autoclaved) after every patient.
2)Wiping, flushing, or surface disinfectant alone is NOT acceptable for handpieces.
3)A 5-minute gap between patients is not sufficient for proper sterilization. Autoclaving requires adequate time and separate instrument sets.
4)Using the same handpiece on consecutive patients without heat sterilization is unsafe and increases the risk of cross-infection.
5)Touching operatory surfaces (light handles, chair controls) with contaminated gloves without disinfection or barrier protection is against standard protocol.
Next Steps
You are well within your rights to ask about sterilization protocols. If these practices continue, seeking care at a clinic that strictly follows universal precautions would be advisable.