My little one for his first tooth last week and is around the same age as your lo. He now has a second one. Both teeth at the front on the bottom. Id assume they take around 3 or 4 weeks to start showinng properly once through. Last week i had to really look hard to see them but now every time he laughs you see them staight away and thats only been a week. But there still not too raised up out the gum yet, guessing another couple of weeks and they will be. Think they grow quite quick once theyve broke through the gum. My first little boy got his first two teeth at 5 months too, another 2 at 6 months and 3 at 7 months but think all babies are different.