If a maxillary 1st molar is affected by periodontal disease it is expected that the furcation which will be involved first is the.. Buccal furcation

If a maxillary 1st molar is affected by periodontal disease it is expected that the furcation which will be involved first is the:

1. Distal furcation

2. Buccal furcation***

3. Mesial furcation

4. All furcations will be involved at the same time.