The more economical choice of the Powerex line of dental compressors, the Powerex Model OTS and OTD reciprocating air compressors use a piston and cylinder assembly similiar to an Volkswagon Bug or Harley Davidson engine. While a reciprocating air compressor costs less to purchase, it does have higher maintenance demands and costs than a Powerex Scroll compressor.
If your maintenance practices aren't exactly "routine", consider the Scroll package. Other than an air filter change once a year, the compressor won't need maintenance for approximately 10,000 hours of run time. The OTS and OTD compressors require lubrication of internal assemblies every 2,000 hours and valve adjustments every 7,000 hours. This is the case with all oilfree reciprocating air compressors, regardless of manufacturer.