Evaluation of posterior indirect resin composite restorations with proximal box elevation technique.

Restoration of large posterior defects extending below the cemento-enamel junction (CEJ) with coverage of one or more cusps represent a very common clinical situation. When restoring deep cervical margins biological and technical operative problems may occur. In order to make clinical procedures less fault-prone 'Proximal Box Elevation' (PBE) is an option that refers to application of composite resin in the deepest parts of the proximal areas in order to reposition the cervical margin supragingivally prior to cavity preparation for an indirect restoration.

This project aims to evaluate the clinical performance and periodontal status of posterior indirect composite restorations with PBE. According to study design at least 60 patients will be recruited to project and 80 restorations will be evaluated. The project will be carried out at the School of Dentistry, Istanbul Medipol University,Turkey.

The rehabilitation of decayed or fractured posterior teeth using an indirect technique was introduced for large cavities with coverage of one or more cusps. Problems of biological nature and technical operative may be encountered when restoring large cavities extending below the cement-enamel junction(CEJ).

Biological problems refers to the possible violation of the 'biological width', a recommended distance of 3 mm or more between the restorative margins and the alveolar crest. The technical operative problems include difficulties in tooth preparation, impression making, adhesive cementation of the restoration, finishing and polishing in subgingival areas. In order to eliminate these difficulties Proximal Box Elevation' (PBE) was introduced that proposes application of composite resin in the deepest parts of the proximal areas in order to reposition the cervical margin supragingivally. Whether the PBE technique is the most optimal treatment option for the restoration of cavities extending below CEJ and how the proposed advantages and possible disadvantages could affect the clinical performance of the indirect restorations are the topics extensively discussed among clinicians.

According to results of in vitro studies, PBE was found to be effective in indirect resin composite bonding to deep proximal boxes in terms of marginal quality and adaptation (1).

In a retrospective clinical study, 79 indirect composite restorations were clinically examined following modified United States Public Health Service criteria. Survival rate was 91.1% and success rate was 84.8% after 5 years (2). Similarly, in another clinical study success rate of 71 indirect composite restorations was reported as 100% after 36 months (3). Nevertheless, not much scientific evidence on the influence of PBE technique on the longevity of the restorations and the periodontal health could be found in the currently available literature. Randomized controlled clinical trials with classification of baseline clinical situation and standardization of cavity preparations are necessary to evaluate the clinical performance of this technique.

This study will be carried out as a prospective study, with assessment of the restorations after three years. 80 indirect composite restorations in at least 60 patients will be included. Potential patients attending to Istanbul Medipol University Dental Clinics in Istanbul will be invited to the study. The patients meeting the inclusion criteria will be recruited. After giving their consent to take part in the study, baseline clinical situation will be classified based on technical operative and biological parameters (4).

The treatment procedure is:

Restorative process in all cases, will start with coronal relocation of the margins using flowable composite with maximum thickness 1 to 1.5 mm and followed by resin composite build-up. Defined principles of morphology driven preparation technique will be followed for standardization of cavity preparations. Impression making, fabrication of indirect restoration with SR Nexco and adhesive cementation will be completed according to manufacturer's instructions.

The control procedure is:

The restorations will be evaluated according to marginal adaptation, cavo surface marginal discoloration, approximal contact, fractures and caries associated with restorations. The periodontal status will be assessed with defined periodontal parameters. The controls will be conducted after two weeks, six months, 1year, 2 and 3 years.

Inclusion Criteria:

1. Vital or endodontically treated posterior teeth with extensive substance loss
2. Caries removal or restoration replacement (i.e. amalgam, composite, glass-ionomer)
3. Large posterior defects with at least one or more cuspal coverage in molars
4. Proximal defects extending below CEJ and at least one or more cavity margin/margins located beneath the gingival tissues
5. Maximum 2 indirect restorations with SR Nexco material in each patient
6. No obvious untreated caries in the rest of the dentition, dental health problems (regularly checked by a dentist)
7. Good or moderate oral hygiene (plaque score of less than 30% in anterior region before treatment)
8. No untreated periodontal disease (only DPSI 1, 2)
9. Subjects had to be over 18 years of age, 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)
10. Appropriate isolation after cavity preparations
11. 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)
2. Poor endodontic prognosis
3. Pulp exposure
4. Patients who still want to bleach their teeth or bleached teeth less than 3 weeks ago
5. Extremely hypersensitive tooth
6. Excluding the teeth, without opposing natural dentition (either intact or restored with intracoronal or extracoronal fixed restorations), and with a minimum of 20 teeth
7. Substance loss due to developmental anomalies (hypoplasia, amelogenesis imperfecta etc.)
8. Subjects who presented severe wear facets and/or reported parafunctional activities such as clenching or nocturnal bruxism
9. Subjects who are pregnant or breast feeding during the duration of the study
10. Subjects who are known to be allergic to the ingredients of resin materials