How can you make a loop that stops when a condition is met then continues?

I'm trying to make a loop that creates parts and stops when there's 20 parts, but then continues again when there is less than 20 parts in the game.

while wait(.1) do
    local model = game.Workspace.Model
    local children = model:GetChildren()
    local part = Instance.new("Part")
        part.Parent = workspace.Model
        part.Position = Vector3.new(10,10,10)
    print(#children)
    if #children >= 20 then

    end
end