This study reports the clinical outcomes obtained in a longitudinal cohort of 23 patients treated by guided tissue regeneration for strategically important teeth compromised by the presence of deep intrabony defects. After completion of initial periodontal therapy and placement of a provisional fixed partial denture, a nonresorbable e-PTFE membrane was applied to isolate the defect. Changes in probing attachment level, probing pocket depths, and radiographic bone support were evaluated 12 months after removal of the membrane. Clinically and statistically significant improvements in outcome measurements were observed: a probing attachment level gain of 5.3 ± 1.7 mm, a reduction in probing pocket depths of 6.1 ± 2 mm, and an increase in the percentage of radiographic bone support of 31% ± 18%. The results obtained were highly reproducible with 91.3% of the cases resulting in probing attachment level gains of 4 mm or more. The evidence provided in this investigation indicates that guided tissue regeneration can predictably increase the functional support, and possible improve the prognosis of strategically important abutments. Guided tissue regeneration therapy should, therefore, be one of the options discussed in treatment planning for complex periodontal-prosthetic cases.