Influence of proximal box elevation on the marginal quality and fracture behavior of root-filled molars restored with CAD/CAM ceramic or composite onlays

Abstract

OBJECTIVES This study investigated the influence of proximal box elevation (PBE) with composite resin when applied to deep proximal defects in root-filled molars with mesio-occluso-distal (MOD) cavities, which were subsequently restored with computer-aided designed/computer-aided manufacturing (CAD/CAM) ceramic or composite restorations. MATERIALS AND METHOD Root canal treatment was performed on 48 human mandibular molars. Standardized MOD cavities were prepared with the distal box located 2 mm below the cemento-enamel junction (CEJ). The teeth were randomly assigned to one of four experimental groups (n = 12). In groups G1 and G2, the distal proximal box was elevated up to the level of the CEJ with composite resin (PBE). No elevation was performed in the remaining two groups (G3, G4). CAD/CAM restorations were fabricated with feldspathic ceramic (Vita Mark II, CER) in groups G1 (PBE-CER) and G3 (CER) or with resin nano-ceramic blocks (Lava Ultimate, LAV) in groups G2 (PBE-LAV) and G4 (LAV). Replicas were taken before and after thermomechanical loading (TML; 1.2 Mio cycles; 49 N; 3,000 thermocycles between 50°C and 5°C). Following TML, load was applied until failure. Fracture analysis was performed under a stereomicroscope (×16). Marginal quality before and after TML (tooth restoration, composite restoration) was evaluated using scanning electron microscopy (×200). RESULTS After TML, lower percentages of continuous margins were observed in groups G1-G3 compared with pre-TML assessments; however, the differences were not statistically significant. For group G4-LAV, the marginal quality after TML was significantly better than in any other group. The highest mean fracture value was recorded for group G4. No significant difference was found for this value between the groups with PBE compared with the groups without PBE, regardless of the material used. The specimens restored with ceramic onlays exhibited fractures that were mainly restricted to the restoration while, in teeth restored with composite onlays, the percentage of catastrophic failures (fractures beyond bone level) was increased. CONCLUSION PBE had no impact on either the marginal integrity or the fracture behavior of root canal-treated mandibular molars restored with feldspathic ceramic onlays. CAD/CAM-fabricated composite onlays were more favorable than ceramic onlays in terms of both marginal quality and fracture resistance, particularly in specimens without PBE. CLINICAL RELEVANCE Composite onlays with or without PBE may be a viable approach for the restoration of root-filled molars with subgingival MOD cavities. AbstractObjectives This study investigated the influence of proximal box elevation (PBE) with composite resin when applied to deep proximal defects in root--filled molars with MOD cavities, which were subsequently restored with CAD/CAM ceramic or composite restorations.

Marginal sealing of relocated cervical margins of mesio-occluso-distal overlays

“…In contrast, most previous studies reported no significant difference in marginal quality between restorations placed directly on dentin and those with CMR composite (20,25,28,(48)(49)(50). However, two studies showed that, after being subjected to thermal and mechanical stress, luting directly to dentin (conventional technique) resulted in superior marginal adaptation as compared with CMR composite on dentin (21,23). The present findings might have been affected by polymerization shrinkage of the resin composite materials used for making the CMR and luting the overlay (51)(52)(53)(54).…”

“…The present study used a leakage test to evaluate the marginal seal of restorations; however, previous studies evaluated margin quality by using low-magnification scanning electron microscopy (20,21,23,25,37,(48)(49)(50)55).…”

“…The investigated variables were marginal (20,21,23,25,27,28,49,50,55) and internal adaptation (37,48,50), bond strength to the proximal box floor (56), and fracture behavior of restored teeth (23). Marginal adaptation was usually evaluated by SEM examination of impression replicas, to determine the percentage of continuous gap-free margins before and after thermal and mechanical stress.…”

“…Surgical margin relocation can address this (17) but is associated with attachment loss and anatomic complications because of the proximity to root concavities and the furcation area (18). As an alternative to periodontal surgical procedures, the cervical margin can be elevated coronally by applying bonding and resin composite materials (19), in accordance with proximal box elevation technique (20)(21)(22)(23)(24)(25), also referred to as cervical margin relocation (CMR) (26)(27)(28), deep margin elevation (18), or open-sandwich technique (29)(30)(31)(32). CMR can be performed with hybrid or flowable composites, after placing the metal matrix and interproximal wedge.…”

Influence of different composite materials and cavity preparation designs on the fracture resistance of mesio-occluso-distal inlay restoration

“…There is not a specific aging or fatigue protocol in the literature for the laboratory test methods. Generally, the specimens have been subjected thermocycling 34,35) or thermomechanical loading 21,36) or stored in various liquids with various percentages 32) . However, in several studies no aging protocols were applied to specimens, some of those are presented by Liu et al 24) , St-Georges et al 17) ,Soares et al 18,37) , and Görücü 38) .…”