This chapter discusses case selection, treatment procedure, and the scientific background of the long-term prognosis of molars undergoing tunnel preparation. If a surgical tunnel preparation has been performed and the patient is not able or willing to brush it, the purpose of the treatment will be defied and compliance could be further affected. As soon as the standard of oral hygiene is acceptable, brushing of a furcation entrance can be introduced as a preparatory step to a furcation preparation. A pulp reaction might be expected, as accessory root canals are frequently found in the furcation area of multi-rooted teeth. Molars subjected to furcation tunnelling were reported to be at risk for root caries in the furcation area. A crucial point during the maintenance phase is the time when the patient is discharged from the periodontal practice. The patient should be seen for post-operative follow-up four and eight weeks after surgery.