The aims of this clinical study are:

To evaluate the clinical performance between indirect composite and ceramic laminate veneers:

Main interests are:

• colour stability of the restoration (digital measurement in follow up)
• failure mode of the restoration
• wear of the restoration and antagonist

Hypothesis:

• The colour stability of indirect composite restorations will not be different from the ceramic restorations.
• The indirect composite restorations will not be more prone to failure than the ceramic restorations.
• Antagonist wear and restorative material wear will be similar for both ceramic and composite.

Material and Methods The laminates will be fabricated according to a specified protocol. In order to avoid possible noticeable differences in case of distinct levels of possible discoloration, a modified split mouth design is employed where the central incisors and the symmetric other teeth receive the same type of restoration. Randomization is based on the paired teeth and it is performed using the flip of a coin for the choice of material. Evaluation will be performed at baseline and at follow-up visits annually up to 2 years.

Patient recruitment: Patients will be recruited from the university clinic.

Intake: If the patient is included in the study following the inclusion and exclusion criteria, the patient will be evaluated using the evaluation form. All the data will be collected and impressions will be made. Using the impressions, a wax up will be made on stone models indicating the restorations to be fabricated. With a transparent mould, the situation will be duplicated in the mouth with spot etching and composite. By using this protocol minimal loss of tooth material is guaranteed.

Tooth Preparation: After prophylaxis, the teeth will be prepared in a controlled manner using special depth cutting laminate preparation burs (Intensive, Switzerland). The margins will extend to half the way to the inter-proximal contact area. The shape of the cervical margins will be maintained in chamfer form. The incisal edge will be prepared 1.5 mm to create an overlap to the palatinal region for the translucency area in the laminate veneers.

Conditioning the tooth surface: Rubberdam will be placed. The preparation surfaces will be etched with 35% phosphoric acid, rinsed thoroughly and dried followed by the application of primer and the bonding agent.

Conditioning the existing restorations: The existing composite restaurations will be conditioned using tribochemical silicacoating (CoJet, 30µm SiOx, 3M ESPE) in a Dentoprep (Ronvig, Denmark) intraoral sandblaster. Following this the restauration will be conditioned by silanisation.

Conditioning the composite veneers: The inner surfaces of the indirect composite laminates will rinsed with alcohol and thereafter conditioned using tribochemical silicacoating (CoJet, 30µm SiOx, 3M ESPE) using an (Ronvig, Denmark) intra-oral sandblaster. The sandblasting will be approx 13 sec until the inner surface of the restoration change colour visually. Following this the inner surface will be conditioned by silanisation.

Conditioning the ceramic veneers: The inner surfaces of the ceramic laminates will be conditioned with hydrofluoric acid 5% and rinsed in neutralizing agent, ultrasonically cleaned and then silanized.

After insertion, the excess composite will be removed using handinstruments and finishing burs under continuous water-cooling. Finally the margins will be polished using diamond polishing-paste with a rotating rubber cup. The interproximal surfaces will be finished with Sof-Lex polishing disks and strips.

Cementing the restorations: The cementation medium will be a dual-cure aesthetic adhesive cement Variolink veneer. All adhesive restorations will be cemented using ultrasonic insertion techniques. Cementation of the indirect restorations will be performed according to a protocol presented in appendix 2: "Clinical procedures".

Inclusion Criteria:

1. The veneers will be placed on central incisors, lateral incisors, canines in the maxilla. Indications will involve replacing worn, discoloured composite restorations and existing veneers, or correcting discoloured, malformed and/or misaligned teeth.
2. An indication for closure of the open space (diastema)
3. No obvious untreated caries, dental health problems (regularly checked by a dentist).
4. No untreated periodontal disease (allowed are DPSI 1, 2, 3-)
5. Good or moderate oral hygiene (plaque score of less than 30% in anterior region before treatment).
6. Endodontic treatment with good outcome (root canal densely filled with gutta-percha 0.5-1.5 mm from apex) with only a restoration on palatinal side.
7. The patient agrees with the research protocol (signing of an agreement form, appendix 4)
8. 18 Year and older.

Exclusion Criteria:

1. Patients with only one tooth to restore, or two central incisors.
2. Considerable horizontal and/or vertical mobility of abutment teeth: tooth mobility index score 2 or 3.
3. Considerable periodontal disease without treatment (DPSI 3+ and 4)
4. Endodontic treatment with extensive loss of tooth tissue (more than 2/3 of crown is restored with restoration material).
5. Restoration of whole crown, more than 2/3 of coronal part of the teeth is restored.
6. Patients that still want to bleach their teeth or bleached teeth less than 3 weeks before the treatment.