The superficial temporal fat pad and its ramifications for temporalis muscle construction in facial approximation

The construction of the facial muscles (particularly those of mastication) is generally thought to enhance the accuracy of facial approximation methods because they increase attention paid to face anatomy. However, the lack of consideration for non-muscular structures of the face when using these "anatomical" methods ironically forces one of the two large masticatory muscles to be exaggerated beyond reality. To demonstrate and resolve this issue the temporal region of nineteen caucasoid human cadavers (10 females, 9 males; mean age=84 years, s=9 years, range=58-97 years) were investigated. Soft tissue depths were measured at regular intervals across the temporal fossa in 10 cadavers, and the thickness of the muscle and fat components quantified in nine other cadavers. The measurements indicated that the temporalis muscle generally accounts for <50% of the total soft tissue depth, and does not fill the entirety of the fossa (as generally known in the anatomical literature, but not as followed in facial approximation practice). In addition, a soft tissue bulge was consistently observed in the anteroinferior portion of the temporal fossa (as also evident in younger individuals), and during dissection, this bulge was found to closely correspond to the superficial temporal fat pad (STFP). Thus, the facial surface does not follow a simple undulating curve of the temporalis muscle as currently undertaken in facial approximation methods. New metric-based facial approximation guidelines are presented to facilitate accurate construction of the STFP and the temporalis muscle for future facial approximation casework. This study warrants further investigations of the temporalis muscle and the STFP in younger age groups and demonstrates that untested facial approximation guidelines, including those propounded to be anatomical, should be cautiously regarded.