"Remember when a year seemed like a long time?" At the end of another routine and joyless day together, a wife lobs this small grenade at her husband in The Secret Lives Of Dentists, a sharply observed and often brutally funny dissection of the modern marriage. Both parties say nastier things to each other throughout the film, but no one statement better describes the dull inertia that has whisked their union through the decade mark, until they're so inured by careers and children that they function like domestic automatons. Thoughtfully expanded from a Jane Smiley novella by ace writer Craig Lucas (Longtime Companion, Prelude To A Kiss) and director Alan Rudolph, the film catches their marriage at the breaking point, when their routine partnership has finally curdled into a serious crisis. By turns ineffectual and sardonic, Campbell Scott matches the verbal fireworks in last year's Roger Dodger with another performance that deflects his natural charisma, exposing his character's hidden vulnerability and ugliness. Approaching middle age as model suburbanites, Scott and Hope Davis run a husband-and-wife dental practice and manage three young daughters, whose closely succeeding ages suggest that Scott and Davis jumped into parenthood too anxiously. Already burdened with his role as Mr. Mom–the youngest girl attaches to him like an appendage–Scott begins to suspect Davis of having an affair with a local stage director. Reluctant to set the machinations of divorce into motion, Scott doesn't broach the subject with her, holding tight to the dream of a healthy marriage and family life. Meanwhile, he enters into a running dialogue with his conscience, which appears in the form of Denis Leary, a disgruntled patient who plays the proverbial devil on his shoulder. Using teeth as a pliant metaphor for marriage (sturdy yet sensitive, an enterprise that outlasts the body but decays slowly in the mouth), The Secret Lives Of Dentists digs into a common domestic scene with uncommon complexity and insight. With Scott playing the perfect foil to Leary's exasperated sage, the fantasy sequences are hilariously caustic, but as they accumulate more rapidly, the distinction between real and imagined situations becomes disturbingly vague. Once the film enters a bravura sequence in which a deathly flu passes around the entire family, the impending collapse of Scott and Davis' marriage grows as ambiguous as a fever dream. After two notorious duds, Breakfast Of Champions and Trixie, Rudolph returns confidently to form, shedding light on a crumbling institution that American films, from studios to shoestrings, are often too squeamish to touch.