How do you find a retired Dentist's old company name with only an address?

Without knowing which area the retired dentist worked it isn't possible to suggest specific contacts.

It sounds as though you don't know the dentist's name, but there will be a dentists' association in your area; their records are sure to be electronically stored, so they should be able to retrieve the old company name from just an address.

Of course, if another dentist, or other business, is operating at the old address you could ask them or, failing that, get from them the name of the firm leasing out the premises: their old records should have the data.

Local government authority records will also show the information you need.

Have ready as much detail as you know before you contact anyone to ask for information. The amount of assistance you'll get depends on the individual, and how busy they are at the time. If you can quickly give as much data as possible they might be inclined to be more helpful.

Of course, if you live nearby, you could also try asking neighbours of the address in question whether they remember the previous business and its name.