Objective: To explore what motivates dentists to work in prisons using Vroom's theoretical model of motivation as an explanatory framework. Method: In-depth interviews were conducted with ten of the 15 dentists working in Scottish prisons. The focus was to explore their motivations to work in Scottish prisons. The data were analysed using a thematic framework based on the three motivational dimensions of expectancy, instrumentality and valence. Results: The dentists had the skills to help improve their prisoner-patients' oral health but their efforts were often hindered by institutional rationing and the requirement to fit in with prison routines and procedures (expectancy). Despite these institutional difficulties the dentists experienced work rewards associated with the improvement in the prisoners' oral health (instrumentality). Finally, the dentists experienced a feeling of personal worth and a sense of commitment to providing care to Scottish prisoners (valence). Conclusions: The dentists' motivation to work in Scottish prisons may be explained by Vroom's Expectancy Theory. The dentists' motivation is characterised by their beliefs that their work will improve clinical outcomes which will be rewarded by the satisfaction experienced when they overcome environmental obstacles and provide oral health care for their prisoner-patients.