Etched Cavity Research Articles

Replica patterns on composite restorations performed in vitro with different acid-etch procedures and dentin adhesives.

160 experimental Class V restorations using two chemically cured composite resins were inserted in extracted human teeth with conventional and modified acid-etch restorative procedures. The modifications included cavity treatment with non-composite resin, ethanol, or four different dentin adhesives. Following demineralization of the teeth the fillings were examined in the SEM concerning their replica patterns of the etched cavity walls. In vitro conditions favored resin penetration into pretreated enamel and dentin, but resulted in minor variations between different acid-etch procedures compared with those previously seen on resin restorations placed in vivo in teeth with vital pulps.

Dry-etched-cavity pair-groove-substrate GaAs/AlGaAs multiquantum well lasers

A fabrication technique based on reactive ion beam etching is presented for the formation of the facet mirrors on GaAs/AlGaAs lasers called pair-groove-substrate (PGS) multiquantum well lasers. Laser cavities with vertical and smooth walls are achieved with this etching technique by using a high-temperature baked photoresist mask. PGS lasers with 200-μm-long etched cavities show a low pulsed threshold current of 29 mA and a high external differential quantum efficiency of 43%. The threshold current is comparable to those of cleaved lasers. Room-temperature cw operation is easily realized in junction-up mounting.

Marginal adaptation of composite restorations performed in vivo with different acid-etch restorative procedures.

243 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars with the conventional acid-etch restorative procedure and with eight modifications of this technique. The teeth were extracted following an observation period of 4 months. Sections from each cavity were stained and examined for bacteria on the cavity floor. Bacteria in more than 10% of the sections was used as the criterion for marginal leakage along a restoration. Results showed that non-composite resin applied as an intermediary layer in etched cavities or as a surface coating of immediately finished and re-etched restorations, beveling of the margins of preparations, and treatment of the etched cavities with the surface-active comonomer NPG-GMA before filling all significantly decrease the leakage occurrence in the oral environment. The observed differences between the modifications varied considerably but none of them was significant, and no additive effects were found.

The Initial Gap Around Large Composite Restorations in vitro: The Effect of Etching Enamel Walls

Composite resin restorations in cavities are generally associated with the development of a contraction gap during the first minutes after insertion. Enamel-Bond-Concise composite restoration were placed on both approximal sides of extracted pre-molars. The cervical walls of all cavities extended beyond the enamel-cement junction. The enamel walls of one of the cavities in each tooth were acid-etched. The contraction gap was kept air-filled and open at the margin through the use of a special technique. Enamel Bond resin with a fluorescent additive was applied to occlusal and cervical margins of the restorations. The fluorescent resin was "passively" drawn into the gap. In unetched cavities, resin penetrated both cervical and occlusal gaps and some areas of the gap at the axial wall. In cavities with etched enamel, the penetration occurred only at the cervical wall. The distance of penetration from the cervical margin varied from 1 to 6.5 mm, and the width of the contraction gap filled with the fluorescent resin varied from 3.5 to 16 micron. Comparison of the width of the gap at the cervical wall in etched and unetched cavities suggested larger gaps for etched cavities. The method used offers a new technique for the measurement of the contraction gaps around composite resin restorations.

Quantitative evaluation of the morphology of the inner surface of composite restorations.

The aim of the present study was to develop a method for quantitative evaluation of the morphology of inner surfaces of composite resin restorations. Twelve restorations made in vivo using the acid etch technique were examined in a scanning electron microscope at a magnification of x 2000. 2500 predetermined areas (6300 micron2 each) on the inner surfaces of the fillings were scored from 0 to 3 with respect to the impression of their rendering of morphologic details from the etched cavity walls. Based on all the scorings and parts of the scorings, estimates for the enamel and for the dentin relief on each of the fillings were calculated. The statistical comparison of these estimates that approximately 50 areas per filling might be scored to attain an objective and reliable quantitation of the surface morphology.

Marginal leakage and consistency of the composite resin material in etched cavities

The purpose of the study was to evaluate the degree of adaptation of undiluted and diluted composite resin to etched enamel walls with and without an intermediary resin. Cavities (O = 2 mm) were drilled in extracted teeth and the walls were etched with phosphoric acid. Fillings were made of Concise composite resin, without applying an intermediary resin (1), after applying the resin layer (2), after diluting the mix with one (3) or two (4) drops of catalyst resin but without an intermediary resin, and after diluting the mix and applying the resin layer (5). The fillings were ground flush with the tooth surface and the teeth were cycled thermally between two dye solutions baths. The marginal penetration of the dye was evaluated by measuring the discoloured portion of the margin at different depths using a stereomicroscope. The restorations with an intermediary resin (2 and 5) exhibited significantly less leakage than fillings without the intermediary layer (1, 3 and 4). When no resin layer was applied the dilution of the mix seemed to reduce the leakage compared with undiluted material but the differences were not statistically significant. The results indicate the advantage of using an intermediary resin with etching even when the composite is diluted.

Microstructure of inner surfaces on composite restorations related to filling procedure

The inner surfaces of 40 Concise restorations placed in vivo on permanent molars have been studied by scanning electron microscopy. Only grinding traces could be seen on fillings from cavities which had not been etched, while the morphologic structure of the enamel and dentin was reflected on fillings from acid-etched cavities. Application of low-viscous non-composite resin in the cavities before filling with the composite resin did not influence the enamel pattern on the fillings, while the amount of processes of resin corresponding to the dentinal tubules in etched cavities was significantly increased. In the discussion the difference in surface structure of the fillings is correlated to marginal leakage along similar restorations.

Experimental in vitro lesions adjacent to composite restorations in etched cavities

Class V cavities and wedge-shaped cavities simulating erosions were prepared in thirty extracted, permanent human teeth. After being etched for 2 minutes with the pertinent cleanser, the wedge-shaped cavities were restored with Enamelite or Restodent. The Class V cavities were etched with 50 per cent phosphoric acid and restored with HL-72. Artificial lesions around the fillings were produced by immersing the teeth in an acid-gelatin system. Ground sections of the teeth with the fillings in situ were studied by polarized light microscopy and microradiography. All the teeth showed “outer lesions,” whereas the occurrence of a “wall lesion” was a rare exception.