Preheat oven to 400 degrees F.In a medium mixing bowl, mix together cream cheese, sour cream and mayo. Add artichokes, spinach, Ranch dressing mix, salt and pepper and ¼ cup mozzarella cheese (reserve the rest for topping). Mix until well combined.Slice bread lengthwise. Place cut sides up on a baking sheet.Brush bread with melted butter. Cover with a sheet or aluminum foil.Bake for 7 minutes.Remove the foil sheet.Top with dip filling, spreading evenly. Top with remaining shredded mozzarella cheese.Bake for 12 minutes or until the cheese is melted.Cool to room temperature before serving.