Objectives: There is no agreement on using inferior alveolar nerve (IAN) block or supraperiosteal infiltration anesthesia during dental implant surgery in the posterior mandibular region. The aim of this study was to evaluate the effectiveness of supraperiosteal infiltration anesthesia on posterior mandibular region during dental implant surgery. Materials and Methods: In this study 52 implants were inserted under supraperiosteal infiltration anesthesia in 29 patients. After the surgery, patients were instructed to note their pain and/or painless dyscomfort on the visual analogue scale (VAS). Their pressure pain threshold (PPT) scores were evaluated by mechanical algometer. The distance between the apical end of the implants and IAN was measured by using calipers on postoperatif panoramic radiographs. Results: 50 implants to 27 patients had been able to place without pain under supraperiosteal infiltration. Implants which were placed at the mandibular second premolar and first molar region had been able to place with free of pain with supraperiosteal infiltration. There was no relationship among the distance between the apical ends of the implants and IAN with intraoperative discomfort of the patients. VAS scores during implant placement at the second premolar region were relatively higher than at the first and second molar region. Conclusion: Supraperiosteal infiltration anesthesia is a safe and effective method for posterior mandibular implant surgery. However the length of the implant should be determined carefully to avoid possible damage to IAN during implant placement under supraperiosteal infiltration anesthesia.