Wear of resin-modified glass ionomers: an in vitro study

The purpose of this study was to evaluate the wear resistance and clinical applicability of resin-modified glass ionomer cements as restorative or fissure-sealing materials. The in vitro wear of resin-modified glass ionomers was compared to conventional glass ionomers, a resin-based sealant, and a composite resin. A three-body wear test (enamel block--polymethylmethacrylate powder--experimental dental material) was performed by 20,000 cycles with a load of 4 kgf/cm2. The depth of wear of the experimental materials was measured and calculated using a computerized laser surface scanner. The glass ionomers generally showed more wear than the resin-based sealant and the composite resin, but there was no difference in wear between resin-modified and conventional glass ionomers. Type III ionomers (used for sealant) showed lower wear resistance than type II ionomers (used for restoration).

Early loss of pit and fissure sealant: a clinical and SEM study

The rate of early loss of preventive resin restoration and single application of pit and fissure sealant was determined by a clinical survey. The rate of partial and complete sealant loss on the observed surfaces was 14.4% (43/299) at the 3-month recall, with a further loss of 7.0% (12/171) between the 3- and 6-month recalls. Typically, a complete loss of sealant was observed on maxillary molars and on the buccal surface of mandibular molars, while partial loss caused on the occlusal surface of mandibular molars. Scanning electron microscopic observation of in vivo tooth replicas revealed partial gap formations and small fractures of sealant indicating failure or degradation of adhesion. The presence of unetched areas after routine cleaning and acid etching, especially in and around pits and fissures could be a major cause of early sealant loss.

In vitro marginal leakage of Class II composite resin restorations by thermal cycling

In vitro marginal leakage on class II composite resin restorations by thermal stress was investigated at the cervical, proximal, bucco-lingual, and mesio-distal margins of extracted human premolars. The composite materials used in this study were: (1) Occlusin with Bonding Agent(a), (2) Palfique Light-S with Light Bondb, (3) P-50 with Dentin Primer & Scotchbond 2c, and (4) P-50 with Vitrabond and Scotchbond 2c. Those four groups were representatives of a (l) conventional bonding agent, (2) hydrophilic bonding agent, (3) dentin priming or conditioning agent with a hydrophilic bonding agent, and (4) glass ionomer cement used for a sandwich technique. The number of experimental teeth investigated in each group was ten. The marginal seal among the margins and composite materials was investigated by a dye penetration test using a basic fuchsin solution. The results showed that marginal seals at the cervical margins were found to be improved significantly by the use of dentin bonding materials and methods when compared with a conventional (enamel) bonding agent. However, the proximal margins generally had a less effective marginal seal than the occlusal (bucco-lingual and mesio-distal) margins. In addition, the mesio-distal margins showed a less favorable result than did bucco-lingual ones. These differences among margins might be from the efficacy of a round bevel along the occlusal cavo-surface margin, the different thicknesses of cavity enamel, and the order of light exposure.(ABSTRACT TRUNCATED AT 250 WORDS)