A tooth abscess differs from a gum abscess by the source of the original infection. The tooth abscess (or periapical abscess) originates from the pulp of the tooth and exits out the tooth's apex at the bottom of the root. A gum abscess (or periodontal abscess) starts in a gum pocket outside of the tooth next to the root.
Click here to see a 239-word sentence that is a perfectly fine sentence (structurally). When two independent clauses are connected by only a comma, they constitute a run-on sentence that is called a comma-splice. The example just above (about the sunscreen) is a comma-splice.
What is a Comma Splice? A comma splice occurs when you use a comma to join two complete sentences without placing an appropriate joining word between them. The comma just isn't strong enough to do the job of making one grammatical sentence out of two. Learn to recognize what comma splices look like, and be sure to avoid them in your essays. Here is a simple example of a comma splice: I completed my essay, I have not submitted it.