Alveolar Bone Loss Bone Transplantation Follow-Up Studies Guided Tissue Regeneration, Periodontal Humans Periodontal Attachment Loss Periodontal Pocket Platelet Transfusion Radiography, Dental Tooth Loss Treatment Outcome alveolar bone loss autogenous platelet concentrate bone transplantation controlled study diagnostic imaging follow up guided tissue regeneration human intra-bony defects long-term results periodontal disease periodontal guided tissue regeneration periodontal pocket platelet-rich plasma procedures randomized controlled trial thrombocyte transfusion tooth radiography treatment outcome