There are a number of reasons that bonding can chip and not all of them are in the control of a patient. All things being equal anterior bonding commonly chips due to point stress on the edges of anterior teeth. This can occur when patient places their teeth in an edge to edge position. This stress happens when a patient is using their anterior teeth to cut their food with their anterior teeth. When doing so they can place their teeth in an edge to edge position. Biting into something stiff(a pencil, a frozen milky way, a finger nail,a crusty french baguette) or even using your teeth to tear open a plastic bag can cause bonding to chip.
Another frequent cause for anterior bonding failures is bruxuing during the night. Patients sometimes brux by placing their teeth edge and placing repeated grinding pressure on their anterior teeth. Patients with worn anterior teeth, often are suspected anterior bruxers, and this habit can pose a problem for anterior bonding. I carefully check anterior excursions when I repair the edges of anterior teeth, but even so often patient can go into excursions at night that can cause bonding to break. To protect bonded teeth I frequently recommend having a patient wear a night guard or even a retainer that covers the edges of their anterior teeth since it has been my observation that night appliances do tend to protect bonding from the forces generated by bruxing.