Philtrum morphology and its dental correlates: a cross-sectional study of sex and age variation

The philtrum is a key perioral landmark contributing to facial aesthetics. While sex, age, and ancestry influence philtrum morphology, its relationship with underlying dental structures remains underexplored. This study aimed to classify philtrum morphology, quantify its dimensions in an adult cohort, and examine associations with sex, age, and upper dental measurements. The study cohort consisted of 99 adults of European background (71 females, 28 males). Anthropometric assessment was conducted using digital calipers and standardized frontal photography. Philtrum morphology was classified by two independent observers. Statistical analyses included t-tests, correlations, and multiple regression, with additional predictive modelling using machine learning. Parallel morphology was the most common (55.7%). Philtrum height and width were significantly greater in males than females (p < 0.001). Philtrum width and height showed moderate positive correlations with age. In females, central incisor lengths showed moderate negative correlations with age. Multiple regression identified sex and first premolar width as significant predictors of philtrum width and sex, age, and upper central incisor length as predictors of philtrum height. Machine learning models substantially improved predictive accuracy compared to multiple regression, explaining 72% of the variance in philtrum width and 58% in philtrum height. Inter-observer agreement for morphological classification was high. These findings indicate that philtrum morphology varies with sex and age and is associated with underlying dental structures. The study contributes to understanding soft tissue-hard tissue relationships and provides reference data with relevance to aesthetic, orthodontic, and reconstructive contexts.