Resin composites, the first choice of material for the restoration of posterior teeth, still have several drawbacks including their polymerization shrinkage and potential failure of the resin-dentin interface leading to secondary caries. Time-saving and simplified restorative procedures are an ongoing demand for posterior applications.The bulk-fill resin based composites (BF-RBCs), has been developed with an attempt to speed up the restoration process by enabling up to 4- or 5-mm thick increments to be cured in one step. The photo-polymerized single-step BF-RBC materials seem to have some limitations in terms of adequate polymerization.

Therefore, recently, the use of dual-polymeritzed RBCs that are also suitable for bulk-fill application with additional bioactive properties such as acid-neutralizing ion release has been offered as an alternative to photo-polymerized ones. Cention N (Ivoclar Vivadent, Schaan, Liechtenstein) restorative material is one approach that has been introduced as a new material category for this purpose. The hand mixed form is named as Cention N whereas auto-mixed capsule form is Cention. Both of them are resin based composite materials categorised as 'alkasite'. They are self-curing composites with optional photo-polymerzation for full volume (bulk) placement. Their composition is same with only exception of the concentration of the initiators and the powder liquid proportion. Cention is delivered together with Cention Primer to ensures the retention of the filling independent of the preparation.

The objective of this prospective clinical trial is to evaluate the clinical performance of Cention and Cention Primer in restoration of Class I and II cavities.

The aim of the study is to place at least 90 posterior restorations with Cention (in at least 45 patients). The patients will be informed about the study and ask to sign the Informed Consent. After having the initial radiographs and images, the preperation will be performed by standard procedures. As the cavity preparation is finished the measurement of the cavity dimensions will be performed by using a periodontal probe. After having the cavity images the cavity will be restored by Cention according to the manufacturer's instructions. Following the occlusal adjustment final image of the restoration will be taken.

After 2 weeks the patient will be recalled in order to asses the baseline FDI criteria by two observers. This recall appointment will be done annually up to 3 years.

Inclusion Criteria:

1. Vital tooth checked with sensibility test towards cold
2. Proximal and/or occlusal caries lesion to be treated invasively or restoration that needs replacement (i.e. amalgam, composite, glass-ionomer)
3. Class I & II restorations in premolar and molars (at least 75% Class II).
4. Maximum 2 fillings with Cention in each patient
5. No obvious untreated caries in the rest of the dentition, dental health problems (regularly checked by a dentist)
6. Good or moderate oral hygiene (plaque score of less than 30% in anterior region before treatment) Moderate or high caries activity: DMFS equivalent or higher than mean DMFS of the population of the same age group in the same region or city.
7. No untreated periodontal disease (only DPSI 1, 2)
8. Subjects had to be over the age of 18, be classified according to the American Society of Anesthesiologists (ASA) as ASA I or ASA II, present with moderate to good oral hygiene, and be free of periodontal disease (probing depth and attachment levels within normal limits, no furcation involvement, and no mobility)
9. Appropriate isolation after cavity preparations
10. Subjects had to agree to keep the scheduled recall appointments for data collection and maintenance and plan to stay in the area for at least 3 years.

Exclusion Criteria:

1. Considerable horizontal and/or vertical mobility of teeth: tooth mobility index score 2 or 3
2. Considerable periodontal disease without treatment (DPSI 3-, 3+ and 4)
3. Endodontic treatment
4. Pulp exposure or near pulp exposure
5. Patients who want to bleach their teeth or bleached teeth less than 3 weeks ago
6. Extremely hypersensitive tooth (s. below) / Pulpitis 7 VAS (visual analog scale) >3 on temperature and/or biting
7. Excluding the teeth, without opposing natural dentition (either intact or restored with intracoronal or extracoronal fixed restorations), and with a minimum of 20 teeth
8. Subjects who presented with severe wear facets and/or reported parafunctional activities such as clenching or nocturnal bruxism
9. Subjects undergoing orthodontic treatment
10. Subjects who are pregnant or breast feeding during the duration of the study
11. Subjects who are known to be allergic to the ingredients of resin materials