Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

William Siemiaszko, DDS

Dentist in Seekonk, MA · enumerated 2007.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1720295009

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Registry record

Entity type Individual (Type 1)

Name William Siemiaszko

Credential DDS

Sex Male

Practice address 20 Commerce Way, Seekonk, MA, 02771

Phone (508) 336-6700

Fax (508) 336-6742

Enumeration date May 17, 2007

Last updated in NPPES Jul 8, 2007

Taxonomy & licenses

122300000X Dentist Dental Providers · License 004430 (CT) Secondary

122300000X Dentist Dental Providers · License 21050 (MA) Primary

122300000X Dentist Dental Providers · License DEN02924 (RI) Secondary

122300000X Dentist Dental Providers · License 052591-1 (NY) Secondary

122300000X Dentist Dental Providers · License 30-022317 (OH) Secondary

122300000X Dentist Dental Providers · License DS036764 (PA) Secondary

DDS · Doctor of Dental Surgery: A licensed dentist; DDS and DMD are equivalent dental degrees. About the DDS credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

Read the full guide → Validate an NPI →

Frequently asked questions

Where does William Siemiaszko practice?

The practice location on file with NPPES is in Seekonk, MA. Providers can have multiple locations; NPPES lists the primary practice address.

What is the NPI number for William Siemiaszko?

The National Provider Identifier (NPI) for William Siemiaszko is 1720295009, a Type 1 (individual) record in the CMS NPPES registry.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-07-08.