This article reviews the literature on the use of hydrogen peroxide in three professionally administered bleaching techniques from historical, technique, and safety viewpoints. Safety over time, absolute safety, and relative safety of nonvital bleaching, in-office vital bleaching, nightguard vital bleaching, and over-the-counter bleaching kits are compared. The advantages and disadvantages of different bleaching options, as well as indications for individual or combined use of the techniques, are discussed. In addition, specific indications for the use of the nightguard vital bleaching technique are presented.

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History, safety, and effectiveness of current bleaching techniques and applications of the nightguard vital bleaching technique.

Physical properties and gap formation of light-cured composites with and without ‘softstart-polymerization’

Objectives
The aim of our study was to measure and compare degree of conversion (DC) as well as micro- (indentation modulus, E; Vickers hardness, HV) and macromechanical properties (flexural strength, σ; flexural modulus, Eflexural) of two recently launched bulk fill resin-based composites (RBCs): Surefil® SDR™ flow (SF) and Venus® bulk fill (VB).

In vitro comparison of mechanical properties and degree of cure of bulk fill composites

Nonvital Tooth Bleaching: A Review of the Literature and Clinical Procedures

Effect of bleaching on restorative materials and restorations—a systematic review

Recently, simple radiometers for measuring the intensity of dental curing lights have been introduced. This study examined the relationship among light intensity measurements by three radiometers, distance of curing tip from composite resin, and resin polymerization (as indicated by microhardness). Light intensity measurements, which decreased with increasing distance from the curing tip, were strongly correlated with composite resin hardness. Reduced light intensity produced softer composite resin, particularly on the bottom of specimens (2-mm depth). The different radiometers provided similar indications of the changes in light intensity at various curing distances.

Effects of curing tip distance on light intensity and composite resin microhardness.

Bleaching with 35 percent hydrogen peroxide causes enamel surface changes, which result in lower bond strengths of composite resin. Although a previous SEM study showed that home bleaching with 10 percent carbamide peroxide does not cause such surface changes, the results of our study indicate that carbamide peroxide bleaching reduces the shear bond strength of composite to etched enamel. Removal of surface enamel, however, restores bond strengths to normal levels.

Bond strength of composite resin to enamel bleached with carbamide peroxide.

Recientemente se han introducido radiomedidores sencillos para calibrar la intensidad de la luz de polimerizacion dental. Este estudio examino la relacion entre las mediciones de intensidad de luz con tres radiomedidores, con la distancia de la punta de polimerizacion a la resina compuesta, y con la polimerizacion de la resina (indicada por su micropureza). Las mediciones de intensidad de luz, que disminuyen conforme aumenta la distancia a la punta de polimerizacion, correlacionaron de forma importante con la microdureza de la resina compuesta. Las intensidades de luz menores produjeron resinas compuestas mas blandas, particularmente en el fondo de los especimenes (2 mm de profundidad). Los diferentes radiomedidores aportaron indicaciones similares de los cambios en la intensidad de la luz a distintas distancias de polimerizacion.

Jose Antonio F. Pires

Papers

Effects of curing tip distance on light intensity and composite resin microhardness.

Bond strength of composite resin to enamel bleached with carbamide peroxide.

Efectos de la distancia de la punta de fotopolimerización sobre la intensidad de la luz y la microdureza de las resinas compuestas