Chin Augmentation operation: After 3 years still have pulled muscle in my chin, advice?

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  Prolonged numbness may be due to injury of the sensory nerve(s) to the chin called the mental nerve which is at greater risk of injury when the implant is placed from inside of the mouth due to the added tissue dissection.  The mentalis muscle attachment is also cut with that approach as discussed below.  This may be why you feel like the muscle is "pulled". When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut segments of bone).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  I prefer placement of a  silastic chin implant through a small, curved incision under the chin (submental) instead of through the mouth for the following reasons:
*The submental approach is sterile while the intra-oral approach is not.
*The submental approach requires limited dissection as it is much closer to where the chin implant needs to be placed along the center (front) and lower most sections of the chin on each side (where the wings are placed).  The intra-oral approach by contrast requires dissection all the way down the entire section of the chin in order to reach the same areas for chin implant placement.  This leads to several issues in my humble opinion.  The attachment of the chin muscle to the bone must be cut during the tissue dissection, the sensory nerves (mental) and motor nerves (marginal mandibular nerve) that move the muscles of the lips and mouth) are all in much greater jeopardy of injury because of the added dissection required.
*The added areas of dissection in the intra oral approach, allow upward migration of the implant as well as an increased risk of nerve injury.  Damage to a sensory nerve will create numbness and or an ache type discomfort while injuring the motor nerve will result in an inability to "lower" the corner of the mouth and lower lip.  While some of these symptoms can rarely be experienced in the immediate post op period as the mentalis muscle accommodates the chin implant....these symptoms should be gone within a few weeks post op.
 If you are experiencing any of the above symptoms you may want to discuss these with your Chin Implant Surgeon and perhaps even get a 3-D scan of the face or lower face that will show the position of the implant.  If some nerve injury has occurred, it can take a year or 2 for this to improve to whatever extend that will occur.  If the scan shows one or both wings of the implant are impinging (placing pressure) upon the mental nerve...the implant can be removed and another implant placed below the mental nerve which "may" improve or eliminate the numbness.Hope this helps.