Effect of Coffee and Polishing Systems on the Color Change of a Conventional Resin Composite Repaired by Universal Resin Composites: An In Vitro Study.

The purpose of this study was to evaluate the color stability of repaired aesthetic restorative resin matrix materials after immersion in coffee and the effect of polishing systems after staining. One hundred and eighty cylindrical discs (8 mm × 2 mm) were prepared using a conventional nano-fill resin composite (Clearfil Majesty Esthetic A2 shade) with round cavities (3 × 1 mm). Cavities were repaired by three resin composite materials: Clearfil Majesty Esthetic A2 shade, one-shaded nano-fill resin composite (Omnichroma) and group-shaded nano-hybrid resin composite (Optishade, medium shade). Each group was polished with three polishing systems (n = 20); aluminum oxide (Soflex Spiral Wheels, 3M ESPE), silicon carbide (Occlubrush, Kerr, CA, USA) and diamond particulate (Twist Dia Spiral Wheels, Kuraray, Okayama, Japan). Color change (ΔE00) measurements were performed with a spectrophotometer at the baseline. Half of the polished samples were either kept in distilled water or immersed in coffee for 15 days, and color measurements were repeated before and after polishing. Statistical analysis was performed using the Kruskal-Wallis test. Repaired samples showed different color correspondence values in all groups. All three restorative materials showed significant color changes (ΔE00) after immersion in coffee (p ≤ 0.05). Repolishing of stained samples showed color improvement values in all groups. The content of the polishing system played an important role in removing the stains.

Evaluation of two CAD/CAM materials for Nayyar core and post-retained restorations: Three dimensional stress analysis.

OBJECTIVES: The aim of this study is to assess the stress distribution of a nanoceramic resin CAD/CAM material, Lava Ultimate (LU) and a polymer-infiltrated hybrid ceramic CAD/CAM material, Vita Enamic (VE) for enamel replacement for Nayyar core (corono-radicular dowel and core) or post-retained restoration designs of a maxillary first premolar tooth with missing palatal cusp. MATERIALS AND METHODS: A three dimensional finite element (FE) modelof maxillary first premolar with two roots was modeled. A mesial-occlusal-distal-palatal (MODP) cavity was designed with cavity floor above cemento-enamel junction and including buccal cuspal reduction. Restoration designs consisted of Nayyar core restoration (NCR) and post-retained restoration (PRR) with a glass fiber post. Vita Enamic (VE), Lava Ultimate (LU) were used for enamel and everX Posterior was used for dentin replacement. Vertical occlusal load (100 N) was applied on a spherical solid rigid material simulating the food stuff. Von Mises (VM) and maximum principle stress values were evaluated separately for the remaining enamel, remaining dentin and restorative material in megapascal (MPa). RESULTS: The analysis of both VM and maximum principle stress values revealed that the most intense stress accumulation was in the cervical region of enamel for both designs. For VM, similar stress values were observed only in dentin. Stress analysis of restorative materials showed that everX Posterior had the highest stress accumulation. CONCLUSIONS: The comparison of the two techniques showed that PRR had better stress distribution than NCR. NCR or PRR with LU or VE exhibited similar VM stress accumulation in dentin. Maximum principle stress analyses showed that PRR with LU transmitted the least stress to enamel and dentin indicating that when LU is the material of choice, post-retained restoration would be a satisfactory design. VM stress values of enamel revealed that VE absorbed the stress in itself and transferred less stress to dentin. This could point out that for the restoration of maxillary first premolar tooth with missing palatal cusp, VE may be a suitable material for NCR and PRR restoration techniques. HIGHLIGHTS: When fiber reinforced composite is used as dentin replacement in combination with VE as enamel replacement; any technique; PRR or NCR, may be preferred in the restoration of MODP cavities of endodontically treated maxillary premolars. The clinical relevance has to be further studied in-vivo.

Effect of Direct and Indirect Materials on Stress Distribution in Class II MOD Restorations: A 3D-Finite Element Analysis Study.

The aim of this study is to investigate the stress distributions of different restoration options for class II mesio-occluso-distal (MOD) cavities. A class II MOD cavity with proximal box gingival floor 1 mm below cementoenamel junction was designed in a mandibular first molar tooth model. 3D finite-element analysis (FEA) and 3D-CAD modelling were used to examine the occlusal stresses distributed to the remaining buccal enamel (RBE), remaining lingual enamel (RLE), adhesive surfaces, and restorative materials by direct and indirect materials resulting from a 600 N of static occlusal load stimulating foodstuff. von Mises (VM) and maximum principal (Pmax) stresses were evaluated for two CAD/CAM materials and three direct materials. CAD/CAM materials exerted less stress than the direct restorative materials. Significant von Mises and Pmax stress value differences were seen among all restoration models on RBE. Reducing RLE and including it into the cavity would be a more effective option for this model in this scenario. As VM and Pmax stresses of PIHC CAD/CAM material for RBE and dentin were significantly lower than other tested materials, it may be the choice of material for indirect MOD restorations.