Effects of surface preparation on shear bond strength
Elnafar AA, Alam MK, Hasan R. The impact of surface preparation on shear bond strength of metallic orthodontic brackets bonded with a resin-modified glass ionomer cement. J Orthod 2014;41:201-7
Research has shown that conventional etching combined with composite resin provides an adequate bond throughout treatment; however, the technique comes with the potential costs of decalcification and white spot formation. This article was designed to assess bond strengths of different surface preparations with resin-modified glass ionomer cement, a fluoride-releasing material shown to strengthen enamel and prevent enamel decalcification. One hundred four premolars were divided into 4 groups, and each group was subjected to a different surface preparation: group 1, 37% phosphoric acid; group 2, sandblasting; group 3, sodium hypochlorite and 37% phosphoric acid; and group 4, sodium hypochlorite and sandblasting. The adhesive remnant index and enamel surface roughness were also investigated by an image analyzer system and profilometry, respectively. Scanning electron microscopy also evaluated the morphology of the enamel surfaces of the teeth after debonding. Shear bond strength and the adhesive remnant index were significantly highest in group 3 (17 MPa, 20.66%), followed by group 1 (13.86 MPa, 11.16%), group 4 (9.63 MPa, 3.73%), and group 2 (9.08 MPa, 2.06%). No significant difference between groups was found for surface roughness. Sandblasting, when assessed by shear bond strength parameters, showed significantly lower bond strength than did phosphoric acid etching. Also, phosphoric acid combined with sodium hypochlorite had a better surface preparation quality than did phosphoric acid alone because sodium hypochlorite improves the marginal seal at the bracket base-enamel junction. Scanning electron microscopy showed that both techniques used to remove residual adhesive from enamel, tungsten carbide bur and sandblasting, showed enamel scarring; however, the tungsten carbide bur appeared to be efficient and less time-consuming.
Reviewed by Brett Bullard
Mini-implant considerations
Baumgaertel S. Hard and soft tissue considerations at mini-implant insertion sites. J Orthod 2014;41 (Suppl 1):S3-7
When selecting a site for orthodontic mini-implants, the orthodontist must consider both hard and soft tissues. Hard tissue “macro-anatomical” factors deal with true anatomic structures such as dental roots, neurovasculature, and sinuses. Implants placed close to dental roots are less likely to succeed. Sites adjacent to maxillary molars are favorable, since these teeth have single palatal roots. To ensure adequate root clearance, the implant should be placed after the teeth have been leveled and aligned, or even diverged from each other. Neurovascular bundles in the oral complex should be avoided as well. Although a plain film would be adequate in identifying mandibular structures, 3-dimensional radiographs are required for maxillary structures. Oro-antral perforations can lead to infection and should also be avoided, since these risks outweigh the benefits of bicortical anchorage. Acceptable sites that pose little risk of sinus perforation include the anterior palate and the maxillary alveolar processes. Hard tissue “micro-anatomical” factors deal with local bone anatomy and thus implant stability. Whereas primary stability is improved with thicker cortical bone, secondary stability is influenced mostly by insertion torque. Insufficient torque indicates poor bone-to-implant contact, whereas excessive torque may lead to resorptive remodeling. With regard to the soft tissue, attached gingiva is more favorable, since it lacks mobility. Although mucosal mobility increases with distance from the mucogingival junction, the “limited-mobility mucosa” directly apical to the mucogingival junction is also an acceptable site. With a more apical position, cortical bone is thicker, and interradicular distances are greater. In selecting a site for microimplant placement, hard and soft tissue factors must be thoroughly evaluated to obtain maximal short-term and long-term stability.
Reviewed by M. Noam Green
Mini-implant considerations
Baumgaertel S. Hard and soft tissue considerations at mini-implant insertion sites. J Orthod 2014;41 (Suppl 1):S3-7
When selecting a site for orthodontic mini-implants, the orthodontist must consider both hard and soft tissues. Hard tissue “macro-anatomical” factors deal with true anatomic structures such as dental roots, neurovasculature, and sinuses. Implants placed close to dental roots are less likely to succeed. Sites adjacent to maxillary molars are favorable, since these teeth have single palatal roots. To ensure adequate root clearance, the implant should be placed after the teeth have been leveled and aligned, or even diverged from each other. Neurovascular bundles in the oral complex should be avoided as well. Although a plain film would be adequate in identifying mandibular structures, 3-dimensional radiographs are required for maxillary structures. Oro-antral perforations can lead to infection and should also be avoided, since these risks outweigh the benefits of bicortical anchorage. Acceptable sites that pose little risk of sinus perforation include the anterior palate and the maxillary alveolar processes. Hard tissue “micro-anatomical” factors deal with local bone anatomy and thus implant stability. Whereas primary stability is improved with thicker cortical bone, secondary stability is influenced mostly by insertion torque. Insufficient torque indicates poor bone-to-implant contact, whereas excessive torque may lead to resorptive remodeling. With regard to the soft tissue, attached gingiva is more favorable, since it lacks mobility. Although mucosal mobility increases with distance from the mucogingival junction, the “limited-mobility mucosa” directly apical to the mucogingival junction is also an acceptable site. With a more apical position, cortical bone is thicker, and interradicular distances are greater. In selecting a site for microimplant placement, hard and soft tissue factors must be thoroughly evaluated to obtain maximal short-term and long-term stability.
Reviewed by M. Noam Green
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