A 57-year-old Arlington man pleaded not guilty in Cambridge District Court Monday to charges that he drove his car into a busy restaurant at dinner time on the weekend, Middlesex prosecutors said. Nick Martirosyan was charged with operating a motor vehicle under the influence of alcohol and negligent operation of a motor vehicle. Police said it was his second OUI offense. They responded to Scutra Restaurant on Summer Street in Arlington at about 6:15 p.m. Saturday night. A 70-year-old woman was taken to a nearby hospital with injuries described as not being ife-threatening.Jacqueline Tempera can be reached at firstname.lastname@example.org. Follow her on twitter @jacktemp.