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.