Cadaveric analysis of periosteal temperature response across skin types in facial tissues using a multi-wavelength diode laser.

Energy-based devices are often applied to the midface using uniform treatment parameters despite interindividual variability in facial anatomy and skin pigmentation. For bulk-heating technologies, clinical relevance depends not only on superficial heating but also on the timing and magnitude of temperature rise at deeper tissue planes, as periosteal thermal exposure in the malar cheek may influence procedural safety and discomfort. This study aimed to quantify time to periosteal temperature rise in the malar cheek and to compare this parameter between Fitzpatrick skin types I-II and III-IV. This cadaveric study was conducted using four human hemifaces representing Fitzpatrick skin types I-IV, grouped into I-II and III-IV. A multi-wavelength diode laser was applied to a malar cheek region using a stacking technique. Periosteal temperature at the zygomatic bone was measured with a thermocouple. Time to periosteal temperature rise was defined as the elapsed time from laser activation to the first sustained periosteal temperature increase of ≥ 0.5 °C above baseline. Mean time to periosteal temperature rise was longer in Fitzpatrick I-II specimens (6.4 ± 0.5 s) than in Fitzpatrick III-IV specimens (4.7 ± 0.4 s). Peak temperatures were higher in Fitzpatrick III-IV (68-71 °C) than in Fitzpatrick I-II (58-62 °C). Fitzpatrick III-IV specimens showed earlier periosteal temperature rise and higher peak periosteal temperatures under identical delivery settings, supporting skin type-dependent differences in deep thermal response during stacking delivery of a multi-wavelength diode laser.