**4.7 Relaxin hormone injection**

Relaxin is a specialized hormone which was detected in the periodontal ligament providing proper remodeling of the soft tissue rather than the alveolar bone surrounding teeth. It provides the needed balance of the collagen content in the pressure and tension sites especially during application of forces as orthodontic treatment. It was found that the local injection of relaxin could provide an accelerated tooth movement by reducing the organization of the related periodontal ligaments and increasing the tooth mobility. A weekly injection of 50 μg of relaxin hormone was also found to accelerate tooth movement via soft tissue remodeling, rather than bone, through increasing the collagen at the tension side over its amount in the compression side. It also decreases the organization of the periodontal ligaments surrounding the tooth causing extra mobility [70–72].

### **4.8 Prostaglandin injection**

Prostaglandin is one of the most important inflammatory mediators that is usually secreted during the inflammatory process. It is also considered as a paracrine hormone which affects mainly bone resorption level around the teeth by affecting the osteoclastic activity. It was found that its local application provides 1.6-fold of accelerated tooth movement than the normal range. Formerly, exogenous single or multiple prostaglandin injections were used [70, 73, 74].

#### **4.9 Simvastatin**

Simvastatin is a chemical agent that is usually used to reduce the serum cholesterol level. It was found that it has a positive, stimulatory effect to the bone by stimulation

of bone growth factors (e.g., BMP-2). On local injection, it was found that simvastatin could efficiently treat the infrabony defects and furcation defects and be used for guided bone regeneration. The injection visits could range from one to three times with 0.5–2 ml per visit. It is considered a successful nonsurgical treatment approach [75] (**Figure9**).
