FILE PHOTO: U.S. Supreme Court Associate Justice Brett M. Kavanaugh is seen during a group portrait session for the new full court at the Supreme Court in Washington, U.S., November 30, 2018. REUTERS/Jim Young

WASHINGTON (Reuters) - The U.S. Supreme Court’s newest member, Brett Kavanaugh, issued his first written opinion on Tuesday as the justices in a unanimous ruling bolstered companies’ ability to use arbitration to resolve disputes with customers or other businesses.

The court decided 9-0 to throw out a lower-court ruling that had kept a case involving dental equipment companies from being resolved through arbitration because the court had determined the demand for arbitration was groundless.

Newly appointed justices are generally assigned non-controversial, unanimous cases as their first opinions.

Kavanaugh joined the court in October after a raucous confirmation process during which he had to fend off accusations of sexual assault by California university professor Christine Blasey Ford. He was the second conservative justice named to the court by Republican President Donald Trump, after Justice Neil Gorsuch.

Kavanaugh’s appointment solidified a 5-4 conservative majority on the court. He replaced retired Justice Anthony Kennedy, a conservative who sometimes sided with the court’s liberals on social issues like abortion.

The arbitration case involved price-fixing claims lodged by Plano, Texas-based dental equipment distributor Archer and White Sales Inc against other manufacturers and distributors.

It centered on whether courts can prevent arbitrators from deciding if an issue can be arbitrated at all. Companies prefer to arbitrate claims because it is cheaper and faster than litigation in court, which is harder to fight and carries a greater risk of hefty damages awards by juries.

When a contract allows arbitrators to decide whether a dispute can be resolved through arbitration, “a court may not override the contract,” Kavanaugh said on Tuesday, explaining the decision.

Although Tuesday’s ruling was Kavanaugh’s first opinion for the court, his first known vote as a member of the court was in December when he joined other justices to reject appeals by Louisiana and Kansas seeking to end their public funding to women’s healthcare and abortion provider Planned Parenthood through the Medicaid program.