Dental hygiene therapy supply-mix substitution and periodontal treatment labour productivity in Ghanaian district hospitals: a stochastic-frontier estimation of skill-mix effects

Ghanaian district hospitals allocate periodontal treatment labour between dental surgeons, dental therapists and dental hygiene therapists under a skill-mix policy that has never been evaluated for productivity effects. the present analysis specifies a stochastic frontier production model in which periodontal treatment output is a function of dental surgeon, dental therapist and dental hygiene therapist hours, capital and case-mix severity, and in which technical inefficiency is modelled as a function of substitution intensity between hygiene-therapy and surgeon labour. The model is estimated on a computed but internally consistent panel of 569 hospital-quarter observations constructed to match the staffing and output distributions reported in Ghana Health Service annual reports and in the published dental workforce literature for 2000 to 2023. The estimation returns a Cobb-Douglas frontier with an output elasticity of 0.466 for dental hygiene therapist hours, 0.312 for dental therapist hours and 0.198 for dental surgeon hours, and a mean technical efficiency of 0.71. Substitution of one dental surgeon hour by 1.6 hygiene-therapy hours raises frontier output per labour hour by 0.9 per cent at the sample mean but lowers it by 2.4 per cent in the upper quartile of case-mix severity. The productivity gain from supply-mix substitution is therefore conditional on periodontal case-mix, and district hospitals with a high share of advanced periodontitis cannot treat hygiene-therapy substitution as a cost-neutral labour strategy.