Campbell Scott follows last year’s National Board of Review-honored turn in “Roger Dodger” with another deft performance in “The Secret Lives of Dentists.”

“Dentists” (HHH out of four) is the story of David and Dana Hurst (Scott is joined by Hope Davis, best known as Jack Nicholson’s daughter in “About Schmidt”), two dentists who share an office as well as a home with three young daughters.

One night, before Dana is about to perform in a community theater production, David wanders backstage to wish her luck. He spots her in an amorous embrace with a man whose face he does not see. In the weeks that follow, David suspects that Dana is having an affair and takes note every time she is gone for hours without explanation or has an uncharacteristic mood swing.

“Dentists” is a compelling meditation on the difficulties of marriage and raising children. Its many scenes of a chaotic home life ring true because Alan Rudolph directs them with a natural fluidity. The sequence in which all five family members catch the flu over the course of a week feels so real, it’s as if we’re spying on an actual family.

The child actresses are a dream, and they hold their own with their accomplished co-stars. Davis is really coming into her own as an actress, not only with this film, but also with her appearance in “American Splendor.”

Ironically, what keeps the film from being great is also one of its assets.

The great comedian Denis Leary plays Slater, one of David’s patients and an obnoxious jerk. Slater humiliates David at Dana’s opera by showing the audience that his filling fell out.

Later, Slater becomes the personification of David’s self-doubt and suspicion. At this point, Slater exists only in David’s mind, and he walks around the house giving David advice such as, “Kill her. I would.”

Leary gets the most laughs with his acidic delivery, but his character isn’t really necessary. Scott’s performance is so good that we can already sense what he is thinking and feeling.

Also, with the introduction of Slater, the movie no longer knows what it wants to be. It’s a clever cinematic device, but one that feels like it belongs in a different film – it clashes with the realistic slice-of-life tone that prevails throughout the rest of the movie. And if Slater isn’t real, how can he interact with his environment, like the scene in which he catches a squirrel, fries it and drops it onto David’s dinner plate?

The jokes get hearty laughs because of skillful comedic timing, but they come at an expense to the story and tone.

Despite its flaws, “Dentists” is still a remarkable achievement. And it’s a wonderfully well-acted and well-written antidote to those end-of-summer underachievers.

Reach Hawkins Teague at [email protected].