Etched Enamel Structure and Topography: Interface with Materials

Abstract

Experiments on bonding of acrylic resins to enamel and dentine began in the early 1950s in England with Dr. Oskar Hagger. He developed a monomer based on glycerophosphoric acid dimethacrylate that was chemically cured with sulphinic acid [1]. This was shown in a Swiss patent (no. 211116, 1951) to bond to tooth structure. His work led to the development of Sevitron, an early commercial adhesive [2,3]. In the U.S., Dr. Michael Buonocore made the second, and more important, advance in adhesive dentistry, by demonstrating that acid etching of enamel led to improved resin-enamel bonds using Sevitron-like resin formulations [4]. His rationale for acid-etching enamel was that little adhesion was obtained on unetched enamel, which he correctly surmised lacked microscopic porosities for resin infiltration. He knew that concentrated (85 wt%) phosphoric acid was used in industry to pre-treat metal surfaces prior to painting or resin coating; thus, it was logical for him to use 85% phosphoric acid for 30 s to etch enamel, followed by water rinsing. The results of his work were very controversial at the time. Many researchers regarded Dr. Buonocore's approach as unconventional and reckless because he advocated the use of dangerous, industrial-strength acids in the oral cavity. Over the next 10 years, many investigators confirmed the utility of acidetching enamel to increase resin-enamel bond strengths. The concentration of the phosphoric acid was subsequently reduced to 50% [5], and more recently to 32-37%. With the recognition that primary tooth enamel surfaces were largely aprismatic, etching times of 120 s were commonly used for bonding procedures for primary teeth [6]. Those etching times have been reduced to 60 s [7] and, more recently, 20-30s [8-10] for aprismatic enamel for bonding of pit and fissure sealants and orthodontic brackets.Phosphoric acid etching worked so well for retention of pit and fissure sealants that it was natural to adopt the same acid on bur-cut enamel cavosurface margins [11]. Both a reduction in the acid concentration as well as etching time [12][13][14] had been proposed. Despite the availability of alternative enamel etchants such as pyruvic, citric, oxalic, nitric or maleic acid, phosphoric acid still remains the etchant of choice, with the contemporary adoption of a reduced etching time to 15 s for both prismatic and aprismatic enamel. The solutions used to etch enamel were also made into gels to permit better control of these acids, since acid etching of dentine was erroneously thought to devitalize pulps [15]. For bonding to cut enamel, it was further observed that even a 5-s etching time [16,17], or a phos-

Surface and interfacial analysis of sandblasted and acid-etched enamel for bonding orthodontic adhesives

“…In both groups, the length of the infiltrated region ranged between 6 and 10 mm; this agrees with the relevant literature. 29 A possible difference between the 2 groups might be associated with the extent of interprismatic and intraprismatic resin penetration, which has been shown to influence interfacial bond strength. 29 The surface demineralization of the sectioned interfaces, aiming to remove the cutting smears, and the use of backscattered electron imaging facilitated the differentiation of the resin infiltrated zone, which demonstrated a lower mean atomic number (darker gray scale) than did the underlying intact enamel (lighter gray scale).…”

“…29 A possible difference between the 2 groups might be associated with the extent of interprismatic and intraprismatic resin penetration, which has been shown to influence interfacial bond strength. 29 The surface demineralization of the sectioned interfaces, aiming to remove the cutting smears, and the use of backscattered electron imaging facilitated the differentiation of the resin infiltrated zone, which demonstrated a lower mean atomic number (darker gray scale) than did the underlying intact enamel (lighter gray scale). This zone had greater length in the SBAEB group compared with the AEB group, although the Arrows indicate interprismatic prismatic penetration of resin tags, beyond the interdiffusion zone.…”

“…29 The strong abrasive capacity of the airborne alumina particles can successively remove the aprismatic enamel domains, thus exposing the underlying prismatic structure. Since the mean size of the abrasive alumina particles is 50 mm (much greater than the diameter of a prism), the roughness of the surface left after sandblasting is much higher than the chemical dissolution effect induced by acid etching.…”

Using self-etch adhesive agents with pit and fissure sealants. In vitro analysis of shear bond strength, adhesive remnant index and enamel etching patterns

“…Considering this fact, sealants are an important preventive measure for fissure caries prevention (Bohannan 1983 ); although their documented efficacy and clinical practice guidelines are available, pit and fissure sealants (PFS) are still underused. Furthermore, its retention relies upon the ability of the resin material to thoroughly fill fissures and morphological defects, to remain completely intact and bonded to enamel surface as long as possible (Tay and Pashley 2005 ; Ahovuo-Saloranta et al 2008 ; Erbas et al 2017 ; Paglia et al 2018 ). Additionally, several factors such as operator's experience, isolation, surface treatment, application of an intermediate bonding layer, among others, could play a role in PFS retention (Erbas et al 2017 ).…”

Relación entre la evolución cronológica del esmalte y su respuesta a la técnica de grabado acido convencional: Estudio in vitro

“…132 De este modo, se ha observado que, cuando el análisis se hace de manera paralela a la orientación de los prismas, los resultados son mayores a los logrados cuando estos se presentan en forma perpendicular, así en el estudio de Giannini en 2004, arroja valores promedios de 42.2 Mpa cuando es paralelo y de 11.5 cuando es perpendicular. 133,134 3.…”