Background: Significant numbers of haematology patients are seen on a clinic dedicated to the management of patients with medically complex backgrounds within the Dental Institute of King’s College Hospital. Many are referred for dental assessment and treatment prior to haematopoietic stem cell transplant (HSCT), our clinic aims to provide this service in a timely manner in order to avoid dental concerns delaying transplant. The objective of pre-HSCT dental assessment is the identification and elimination of possible source of dental infection which could otherwise cause significant morbidity or mortality during the transplant process. For most of the patients found to require dental treatment this will involve the extraction of teeth which are non-vital, infected or considered to pose a future risk of infection. Our team includes dental consultants, specialty trainees and hospital grade dentists who work closely with haematology colleagues within our hospital and others. We report two cases in which concerns about oral health identified at dental assessment resulted in planned HSCT being significantly delayed or abandoned. The impact on the patients’ haematological management will be discussed with the aim of highlighting the importance of effective pre-transplant dental assessment and the effects of poor dental health on HSCT. Aims: - To identify patients whose medical outcome was directly adversely affected by their dental health. - To discuss the cases in which findings at dental assessment resulted in significant delay to HSCT. Methods: From the dedicated database of patients managed within our medically complex dental clinic over the last five years, those referred for pre-HSCT dental assessment whose oral health contraindicated proceeding with HSCT around the time this was planned were identified and data pertaining to them extracted. Results: Since 2017 our clinic received more than 600 referrals for pre-HSCT dental assessment from haematology colleagues. The vast majority of patients were deemed dentally fit for transplant either at presentation or after the successful completion of dental treatment. Two patients who could not proceed to transplant due to oral contraindications were, however, identified. Patient 1 had been diagnosed with Hodgkin’s lymphoma 2 years earlier, previous treatment included zolendronic acid. Unfortunately, no dental assessment was undertaken before this bisphosphonate therapy was commenced. He presented with a large, spontaneous osteonecrosis of the left maxilla and a neglected dentition; all remaining teeth required extraction. The patient’s haematologist believed that the presence and extent of the necrotic bone contraindicated HSCT so alternative, less effective treatment, was pursued instead. Patient 2 had received chemotherapy to treat his follicular lymphoma. During pre-HSCT dental assessment a squamous cell carcinoma of the right tongue was noted and later confirmed on biopsy; he subsequently underwent hemi-glossectomy and right neck dissection with free flap reconstruction. HSCT had to be postponed but was successfully completed 3 months after his surgery. Summary/Conclusion: The cases presented highlight the value of pre-HSCT dental assessment and how oral health can impact significantly on wider aspects of healthcare. Although a rare occurrence dental assessment may identify patients who should not proceed to transplant as planned and in doing so may help to prevent adverse outcome of this intervention.