Comparison of a nano resin modified glass ionomer and a submicron hybrid composite materials water sorption, water solubility, flexural strength, elasticity modulus and 18 month clinical evaluation

Glass ionomer cements are known for their fluoride release and recharge, adesion with the dental hard tissues while resin-based composite ae known for their need of minimal cavity preparation and esthetic properties. Due to these advantages both materials are being used commonly in pediatric dentistry for the dental treatment of the child patient. In-vitro and in-vivo researches are needed to find the ideal restorative material for the child patient. The aim of this study was to evaluate the flexural strength, elasticity modulus, water sorption, water solubility and the 18 month clinical performance of a new resin modified glass ionomer containing nano particles (nano-ionomer) and a submicron hyrid composite resin material.For the flexural strength and elasticity modulus tests 10 specimens 25 mm long and 2 mm in diameter from each material and for the water sorption and solubility test 10 specimens 15 mm in diameter and 1 mm thickness from each material was prepared according to the ISO specification 4049:2000. A three point bending test was applyed using the INSTRON 3345 machine to the specimens prepared for the flexural strength and elasticity modulus tests. Specimens prepared for the water sorption and solubility test were dessicated and then immersed in distilled water for 7 days and dessicated for a second time and each specimens weight and volume was calculated.Ninety six patients aged between 7-15 who had two comparable class I dental carries in their left and right lower first permanent molars were included to the study. According to the split mouth study design each patient received only one restoration from each material randomly. The restorations were evaluated on the 1st week, 6th, 12th and 18th month recalls according to the modified USPHS (Ryge) criterias. All patients PI, DI, OHI and GI scores were recorded and all patients received an oral hygiene education prior to treatment and at each recall. Each patients upper and lower first molars periapical radiographs were taken at the first session and the 18th month recall. Each restorations digital photographs were recorded at each recall.The statistical analysis of the in-vitro and in-vivo test results were performed with NCSS 2007 software programme. PI, GI, OHI, CI results were compared with Friedman test and the changes were analyzed with Dunn?s test. The difference in the performance of both restorative materials were evaluated by the Chi-square test. Measurement of agreement between the examiners were compared with Cohen?s Kappa statistic. The level of significance was set at p<0,05.The flexural strength and elasticity modulus results of Ketac N 100 material was statistically lower compared to Spectrum TPH3 (p<0.0001) while the water sorption and solubility of Ketac N 100 was statistically higher compared to Spectrum TPH3 (p<0.0001). The water sorption and solubility and the flexural strength and elasticity modulus results were positively correlated (p<0.0001). Patients 1st day PI, DI, OHI and GI results were higher compared to the 1st week, 6th, 12th and 18th month controls. The difference was only significant for the PI, DI and OHI results (p<0.001). Ketac N 100 materials marginal discoloration, restoration fracture, marginal adaptation results were significanly higher at the 12th and 18th month recalls (p<0.01) while anatomic form-occlusal wear parameter was significanly higher only at the 18th month recall compared to Spectrum TPH3 material (p<0.01). In the 18th month clinical evaluation period only one Ketac N 100 restoration failed because of restoration fracture. While none of the Spectrum TPH3 restoration showed any failure. None of the restoration showed vitaliy loss nor secondary carries. According to the ADA acceptance criteria for restorative materials in the end of the 18th month clinical evaluation Ketac N 100 restorations showed %98.5 and Spectrum TPH3 showed %100 clinical sucess.As a conclusion, the water sorption, solubility and elasticity of the nano-ionomer was higher and the flexural strength was lower then submicron hybird composite material. Spectrum TPH3 material showed a better clinical performance comparing to Ketac N 100 in respect for it?s marginal discoloration, marginal adaptation, restoration fracture and anatomic form-occlusal wear. The clinical performance of both restorative materials were considered satisfactory and clinically accetable for Class I restorations in permanent teeth. But there is a need to evaluate restorations over a longer timescale to determine the long-term clinical performance of both materials.