The invention relates to a diagnostic apparatus comprising a mounting (20) and a measurement circuit (15) attached to the mounting, the mounting comprising a gutter (12) having a shape which substantially complements that of a dental arch, the measurement circuit comprising at least one force sensor (24) arranged at the bottom of said gutter, a clock (28), a memory (30), a control module (32) capable of recording in said memory the force measurements taken by said at least one force sensor and the corresponding times read by said clock, and a battery (36) for supplying the measurement circuit with electrical energy, the mounting comprising at least two layers encapsulating said measurement circuit, the apparatus being characterised in that the measurement circuit comprises a sheet substrate (26), said substrate comprising first and second portions connected by at least one bridge (42) having a width (l) of less than 2 mm.