Pressure-safe electric toothbrush

1 . An electric toothbrush head, comprising:

a bristle field having a plurality of bristles, wherein the bristles comprise a stimulus-responsive material configured to provide a reversible decrease in stiffness in response to a first condition indicative of excessive brushing pressure; and

a mechanical force-protection mechanism configured to induce a reversible physical displacement of the bristle field in response to a second condition indicative of excessive brushing force, wherein said displacement comprises at least one of a rotational slip, a linear retraction, or an angular tilt.

2 . The electric toothbrush head of claim 1 , wherein the first condition is an increase in temperature of the bristles to an oral temperature.

3 . The electric toothbrush head of claim 1 , wherein the first condition is an application of mechanical force to the bristles exceeding a first pressure threshold.

4 . The electric toothbrush head of claim 1 , wherein the stimulus-responsive material is a shape-memory polymer.

5 . The electric toothbrush head of claim 1 , wherein the stimulus-responsive material is a piezoelectric composite.

6 . The electric toothbrush head of claim 1 , wherein the stimulus-responsive material is a magneto-rheological elastomer, and wherein the head further comprises a magnetic field generator configured to alter a magnetic field applied to the bristles to cause the reversible decrease in stiffness.

7 . The electric toothbrush head of claim 1 , wherein the reversible decrease in stiffness is a reduction in effective tip stiffness of at least 40 percent when measured between 22° C. and 37° C.

8 . The electric toothbrush head of claim 1 , wherein the mechanical force-protection mechanism is configured to activate when the second condition corresponds to an applied tip force exceeding 150 grams.

9 . The electric toothbrush head of claim 1 , wherein the physical displacement is the rotational slip, and the mechanical force-protection mechanism comprises a clutch mechanism;

wherein the clutch mechanism is a magnetic torque micro-clutch calibrated to slip at an equivalent tip force between 160 grams and 200 grams.

10 . The electric toothbrush head of claim 1 , wherein the physical displacement is the linear retraction, and the mechanical force-protection mechanism comprises a spring-mounted subassembly;

wherein the linear retraction is over a distance between 1.0 mm and 2.0 mm;

wherein the spring-mounted subassembly further comprises a viscoelastic dashpot cartridge configured to provide rate-dependent damping.

11 . The electric toothbrush head of claim 1 , wherein the physical displacement is the angular tilt;

wherein the mechanical force-protection mechanism is located in a neck portion of the toothbrush head;

wherein the angular tilt is between 10 degrees and 15 degrees relative to a longitudinal axis of the neck portion.

12 . The electric toothbrush head of claim 11 , wherein the mechanical force-protection mechanism comprises an eccentric cam and a compliant joint;

wherein the eccentric cam mechanism comprises at least one detent configured to provide tactile feedback upon engagement.

13 . The electric toothbrush head of claim 1 , further comprising a feedback generator configured to provide a user-perceptible signal upon the inducement of the physical displacement;

wherein the user-perceptible signal is at least one of a visual signal from an LED, a tactile signal comprising a click or patterned vibration, or an audible signal.

14 . The electric toothbrush head of claim 1 , wherein the plurality of bristles further comprise hydrogel cap tips configured to swell under compressive load.

15 . The electric toothbrush head of claim 1 , wherein the plurality of bristles are mounted on telescopic spiral root anchors configured to reversibly extend under compressive load.

16 . The electric toothbrush head of claim 1 , further comprising a transparent window configured to permit viewing of at least a portion of the mechanical force-protection mechanism.