No, not the cereal comma. The serial comma, or Oxford comma. It’s the last comma in a list of three or more words. For instance: Should I read To Kill a Mockingbird, Great Expectations, or Jane Eyre tonight? The comma between “Expectations” and “or” is the one under discussion here.
Some folks were taught to use the serial comma. Some folks were taught not to use it. According to Elements of Style (Strunk & White) and the Chicago Manual of Style, we should use it. According to the Associated Press Style Guide, we should not.
In the example above, with the book titles, the sentence would be completely understood by the reader whether or not a serial comma were used. However, in medical and dental copywriting, we often present new words to readers. In an effort to improve communication, I recommend using the serial, or Oxford, comma.
Here’s a good example:
Replacement teeth include dental implants, dentures, partials and crown and bridgework.
Replacement teeth include dental implants, dentures, partials, and crown and bridgework.
Obviously, to someone who does not know that “crown and bridgework” is one type of prosthetic, not two, the serial comma improves communication. This example has two “ands,” though. The same strategy can apply in other situations. For example:
Porcelain veneers, teeth whitening, composite bonding, tooth-colored fillings and ceramic crowns are considered esthetic restorations.
Porcelain veneers, teeth whitening, composite bonding, tooth-colored fillings, and ceramic crowns are considered esthetic restorations.
You can forge your own opinion, but IMHO, using the serial comma in this series sets each restoration apart, compartmentalizing the words for clearer understanding.
So, in short, there is no right or wrong (or right and wrong depends on whom you ask). To punctuate or not to punctuate? That remains the question.