The resorption of alveolar ridge after tooth extraction develop difficulty in restoring the extraction area with implant or bridge. Therefore, try to preserve the alveolar ridge width and height at extraction socket and gaining its bone volume in maximal is worth for clinical investigation. There are several method to deal with alveolar ridge preservation (ARP), the most popular way for its approach, the trend is toward to minimally invasive treatment. Alveolar ridge preservation which is done with open-healed wound without primary closure is the key for minimally invasive approach.

This three-armed randomized clinical trial would like to determine the effect of applying ribose cross-linked collagen membrane without primary flap closure in molar extraction sockets for alveolar ridge preservation. The procedure is for implant site development.

Three groups were designed as test group1 was grafted with freeze dried bone allograft (FDBA) and covered by ribose cross-linked collagen membrane (OSSIX® PLUS). In test group2 sockets filled with collagen plug(Teruplug®) and sockets healed naturally as control group. Cone-beam computed tomography(CBCT) scans are obtained immediately and 4 months after ARP as the primary outcome and secondary outcome. A biopsy from implant site and histomorphometric analysis will be done as well. The change of marginal bone level and the width/height of keratinized mucosa are measured.

Inclusion Criteria:

• Age>20
• according to periapical film, the bone defect over bucco-lingual and mesio-distal direction less than 50%
• patient agreed to undergo implant therapy after tooth extraction

Exclusion Criteria:

• systemic diseases which will affect wound healing (ex. Diebetes)
• heavy smoker (10 cigarette/day)
• patient who underwent oral-maxillary surgery or who diagnosed with oral cancer
• patient who is pregnant or who is breast-feeding
• patient who is allergic to Lidocaine
• patient who cannot cooperate the study design