Bynum put in 23 points to go with 16 rebounds and Sessions provided 22 points and five assists as the Lakers won their fourth straight game without Kobe Bryant.
The Lakers superstar continued to sit out while nursing a left shin injury.
Los Angeles also benefited from Pau Gasol's 20 points and 10 rebounds.
Dirk Nowitzki had 24 points for the Mavericks, who were swept in their season's series with the Lakers.
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