Effect of a self-etch primer/adhesive on the shear bond strength of orthodontic brackets

Conventional adhesive systems use 3 different agents (an enamel conditioner, a primer solution, and an adhesive resin) during the bonding of orthodontic brackets to enamel. A unique characteristic of some new bonding systems in operative dentistry is that they combine the conditioning and priming agents into a single product. Combining conditioning and priming saves time and should be more cost-effective to the clinician and, indirectly, to the patient. The purpose of this study was to determine the effects of the use of a self-etch primer on the shear bond strength of orthodontic brackets and on the bracket/adhesive failure mode. Brackets were bonded to extracted human teeth according to 1 of 2 protocols. In the control group, teeth were etched with 37% phosphoric acid. After the sealant was applied, the brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif) and light cured for 20 seconds. In the experimental group, a self-etch acidic primer (ESPE Dental AG, Seefeld, Germany) was placed on the enamel for 15 seconds and gently evaporated with air, as suggested by the manufacturer. The brackets were then bonded with Transbond XT as in the first group. The present in vitro findings indicate that the use of a self-etch primer to bond orthodontic brackets to the enamel surface resulted in a significantly (P = .004) lower, but clinically acceptable, shear bond force (mean, 7.1 +/- 4.4 MPa) as compared with the control group (mean, 10.4 +/- 2.8 MPa). The comparison of the adhesive remnant index scores indicated that there was significantly (P = .006) more residual adhesive remaining on the teeth that were treated with the new self-etch primer than on those teeth that were bonded with the use of the conventional adhesive system.     

Tarsal Joint Fusion Using Memory Compression Staples—A Study of 10 Cases

A prospective clinical study was undertaken to assess the effectiveness of Nickel-Titanium Memory compression staples for fusion of the intertarsal joints. Ten patients underwent procedures for fusion of various hindfoot and midfoot joints with the memory staples. The patients were evaluated regarding period of immobilization in cast and time to radiographic joint fusion. Arthrodesis was achieved in all patients. The average time to fusion was 7.8 weeks, with an average period of immobilization of 6.6 weeks. The early experience with the use of these staples in hindfoot and midfoot joint surgery is encouraging. We did not encounter any technical problems, and there is a suggestion that these implants may reduce the time to fusion.     

Mandibular changes in persons with untreated and treated Class II Division 1 malocclusion

The growth potential of individuals with Class II malocclusions is of interest to the practicing orthodontist because such malocclusions constitute a significant percentage of cases. The purpose of this study was to evaluate on cross-sectional and longitudinal bases the changes in mandibular length and relationship and maxillary-mandibular relationships in untreated Class II subjects from deciduous to permanent dentition and also to evaluate the effects of orthodontic treatment, with and without the extraction of first premolars, on these relationships. Class II samples were compared with matched normal, untreated individuals. The Class II Division 1 (Class II/1) untreated sample comprised 30 subjects, 15 males and 15 females. Each subject had a complete set of data at three stages of dental development—namely, Stage I, after the completion of eruption of the deciduous dentition; Stage II, at the time when the permanent first molars and most of the incisors have erupted (i.e., in mixed dentition); and Stage III, at the completion of eruption of the permanent dentition, excluding third molars. The Class II treated sample comprised 44 subjects (21 males, 23 females) treated with four first-premolar extractions and 47 subjects (20 males, 27 females) treated without extraction. Treatment was accomplished with the use of an edgewise appliance, appropriate extraoral traction, and Class II elastics. The extraction decision was based mainly on the presence of crowding and profile consideration. Records on 35 normal subjects (20 males, 15 females) were available from the Iowa Longitudinal Facial Growth Study. Cephalograms for the normal individuals were matched to the corresponding ages of the Class II cases. With regard to these findings, few consistent differences were noted between the untreated Class II/1 and normal subjects on cross-sectional comparisons. The differences in mandibular length and position were more evident in the early stages of development than at later stages. Longitudinal comparisons of growth profiles indicated that the growth trends were essentially similar between the untreated Class II/1 and normal subjects in the various parameters compared. The comparisons of growth magnitude indicated the presence of greater skeletal facial convexity in the untreated Class II/1 subjects, accompanied by a tendency for a more retruded mandible. Initial comparisons between the Class II/1 treated groups and normal subjects indicated that the Class II/1 malocclusions were associated with a larger overjet, deeper overbite, and greater ANB angle. After a 5-year treatment and observation period, an overall “normalization” in the mandibular and maxillary-mandibular skeletal relationships was noted in the treated Class II/1 subjects in both the extraction and the nonextraction groups compared with normal subjects. The changes were more pronounced in the extraction group.(Am J Orthod Dentofacial Orthop 1998;113:661-73)     

The Spike Osteotomy for Hallux Valgus: A Clinical and Radiological Evaluation

A distal metatarsal osteotomy with soft tissue correction is a frequently performed operation to correct mild to moderate hallux valgus deformity. This is a prospective study of 28 feet in 25 patients who underwent spike osteotomy of the first metatarsal with medial capsulorraphy for symptomatic hallux valgus. The osteotomy is a distal metatarsal osteotomy with a spike fashioned in the plantar and lateral quarter of the proximal fragment and impacted into the trough created in the center of the distal fragment, providing lateral and plantar shift of the distal fragment. The American Orthopaedic Foot and Ankle Society's rating scale was used for functional assessment, and a visual analog scale gauged pain. The average follow-up was 27 months. The rating scale score improved from a mean preoperative value of 39/100 to 84/100. Twenty-six feet had complete pain relief, whereas 2 feet had a lesser degree of persistent metatarsalgia. A review of preoperative and postoperative radiographs showed that the hallux valgus angle improved from a mean 36 degrees preoperatively to 18 degrees postoperatively. Likewise, the mean 1 to 2 intermetatarsal angle improved from 13 degrees to 7.3 degrees. There was no incidence of avascular necrosis. Fourteen patients (16 feet) rated the outcome as excellent, 10 (11 feet) as good, and 1 patient with asymptomatic mild hallux varus deformity rated the result as fair. These results demonstrate that the spike osteotomy is a suitable operation for treatment of mild to moderate hallux valgus.     

Third molars: A dilemma! Or is it?

The purpose of this article is to review some of the pertinent studies related to the management of third molars in an orthodontic context. The clinician should base his or her decision to extract or not extract third molars on the most current scientific information and what is best for each individual patient.     

Effect of time on the shear bond strength of glass ionomer and composite orthodontic adhesives

The purpose of this study was to compare the effects of time on the shear bond strength of a resin-reinforced glass ionomer and a composite adhesive system specifically (1) within half an hour after bonding the bracket to the tooth and (2) at least 24 hours from the time of bonding when the adhesive has achieved most of its bond strength. Ninety-one freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into four groups: Group I, glass ionomer adhesive debonded within 30 minutes from initial bonding; Group II, glass ionomer adhesive debonded after 24 hours immersion in deionized water at 37 degrees C; Group III, composite adhesive debonded within 30 minutes from initial bonding; Group IV, composite adhesive debonded after 24 hours immersion in deionized water at 37 degrees C. The results of the analysis of variance comparing the 4 experimental groups (F = 59. 3) indicated the presence of significant differences between the 4 groups (P =.0001). In general, the shear bond strengths were significantly greater in the 2 groups debonded after 24 hours. This was true for both the resin-modified glass ionomer (x = 8.8 +/- 3.6 MPa) and the composite (x = 10.4 +/- 2.8 MPa) adhesives. On the other hand, the shear bond strengths were significantly lower in the 2 groups debonded within 30 minutes of their initial bonding. The bond strength of the resin-modified glass ionomer adhesive (x = 0.4 +/- 1.0 MPa) was significantly lower than that for the composite (x = 5.2 +/- 2.9 MPa) adhesive. The present findings indicated that the resin reinforced glass ionomer adhesive has a significantly lower initial bond strength but increased more than 20-fold within 24 hours. In comparison, the composite adhesive has a significantly larger initial bond strength that doubled within 24 hours. The clinician needs to take these properties into consideration when ligating the initial arch wires.