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.
The Comma Splice. A comma splice, also called a run-on, occurs when a writer has connected two main clauses with a comma alone. A main clause makes a complete thought, so you should not find a wimpy comma struggling to join two such powerful clauses. Main Clause + , + Main Clause.