Can Botox to masseter cause facelift failure?

Thank you for your question. I have considerable experience with masseter injection for facial contouring. Many patients, especially those who have injections for muscle hypertrophy/grinding experience significant debulking around the angle of the mandible as the masseters atrophy. In some patients, this can result in laxity of the lower face. Another possibility in you case is that you have also developed laxity as a natural maturing of your mini-facelift result. In other words, the tissues have relaxed naturally to some degrees. Although I do perform mini-facelifts, I view it as a compromise procedure that may not have the longevity of a full facelift.

Botox injected for teeth grinding does also help slim the muscles since it makes them weaker. However, this is not a permanent effect and Botox will need to be repeated. If your underlying tissue is somewhat thinner, the overlying skin may sag. You can support this loss with fillers or skin tightening like radiofrequency treatments.

Face lifts always look best in the first few months after surgery due to swelling and the tissues are maximally tight and lifted. As the swelling resolves and the tissues stretch and loosen you will lose some of the effect which will be different for everyone. Injecting Botox into the masseter muscle will cause the muscle to shrink and that could potentially cause additional laxity of the lower face and neck. In your case it is probably a combination of the natural stretching and loosening which occurs in the first year after a face lift in addition to the volume loss from the Botox to the masseter muscle. Revisiting your surgeon to discuss these issues would be a good next step. Sometimes we forget how much surgery helped and a review of preoperative and postoperative photographs can be illuminating.