There are some orthodontics treatments that perform risk movements ,and a bone dehiscence may be expected. In that cases mucogingival surgery , such as connective tissue grafts, is necessary prior to tooth movement.

The connective tissue graft in combination with coronal advanced flap is still considered the gold standard , although the use of porcine collagen matrix has obtained promising results for treatment of Miller class I and II recession defects.

Most of the studies report clinical results after a connective tissue graft and there is no evidence about the type of attachment obtained after the graft is performed, a few articles have shown histological results. But, as a rule , a histological study is only performed under exceptional circumstances such as a dental fracture, untreatable decay, tooth extraction for orthodontic reasons, or other reasons.

Most of the techniques results in the formation of a long junctional epithelium and connective tissue attachment with fibers parallel to the root surface. Animals studies have shown a shorter epithelium and a larger new cementum formation after the use of the collagen matrix.

The purpose of this study is to confirm that periodontal regeneration happens after mucogingival surgery The principal outcome is compare the millimeters of new attachment create after a connective tissue graft and after the use of a porcine collagen matrix in teeth that have to been extracted (because of the orthodontic planing treatment) after mucogingival surgery .

The secondary outcomes are:

1. length of new cementum (histometry results)
2. length of the junctional epithelium (histometry results)
3. length of connective tissue attachment (histometry results)
4. complete root coverage (clinical results)
5. width of keratinized tissue

Inclusion Criteria:

• Patient in orthodontic treatment ,who needs mucogingival surgery in both hemi arcade and later the tooth adjacent to the graft should be extracted because of the orthodontic planing treatment .
• The patient must be 18 years or older
• Patient shows sufficient plaque control (FMPS < 20%).
• The patient is able to fully understand the nature of the proposed surgery and is able to provide a signed informed consent

Exclusion Criteria:

• General contraindications for dental and/or surgical treatment are present.
• The patient is taking medications or having treatments which have an effect on mucosal healing in general (e.g. steroids, large doses of anti-inflammatory drugs).
• Untreated periodontal conditions
• Patients not willing to participate

The data collected for the study will be identified by a code and only the researcher will be able to relate them. The personal data will be treated with absolute confidentiality in accordance with the Data Protection Law and will remain in the patient's clinical history. The coded data will be included in a UPV/EHU´s file with reference number 2080310015-INA0110, whose head is Ana María García de la Fuente, and will only be used for the purposes of this project.

Analyst and Histometry: The statistician and the pathologist does not know which treatment corresponds to each variable.