A comparison of the shear bond strengths of two glass ionomer cements.

The objective of this study was to determine the in vitro shear bond strength (in megapascals) and location of bond failure with two light-cured glass ionomer resin systems. One system was a hybrid glass ionomer cement with resin (GC Orthodontics, Aslip, Ill), and the other system a glass-filled resin system (Reliance Orthodontic Products, Inc, Itasca, Ill). These systems, Fuji Ortho LC (GC Orthodontics) and Ultra Band Lok (Reliance), respectively, were compared to a light-cured composite resin. Maxillary premolar brackets (n = 200) were bonded to the facial surface of human premolar teeth. The two glass ionomer resin systems were each evaluated by two protocols, one according to the manufacturers' direction plus a variation of their respective technique. The five distinct groups (n = 40) were stored in 37 degreesC distilled water for 30 days and subjected to thermocycling before shear bond strength testing. The findings indicated that large variations existed between the bond strengths of the materials tested. The laboratory shear bond strength of the glass-filled resin glass ionomer cement (Reliance), whether tested in a dry or moist field, was similar to the composite control with all of the previous materials being significantly (P <.01) higher than both the hybrid glass ionomer cement groups (Fuji Ortho LC). However, the hybrid glass ionomer cement with enamel conditioner demonstrated a clinically acceptable mean megapascal value. The Adhesive Remnant Index values ranged from 0.53 to 1.62. The hybrid glass ionomer cement without enamel conditioning recorded the lowest mean adhesive remnant index score and the lowest mean megapascal score. Although both products are glass ionomer resin systems, their individual chemistries vary; this affects their clinical performance. Clinically, it may be suggested that glass ionomers used in a dry field may be beneficial for orthodontic bonding, and that glass ionomer resin systems used in a moist environment need an enamel conditioner.

Direct bonding to Adlloy-treated amalgam.

The purpose of this study was to test the bond-enhancing effect by modifying amalgam surfaces with Adlloy (a gallium-tin liquid alloy) and bonding brackets by using two different resin systems. Bond strength and location of bond failure was assessed by using (1) Concise (3M Dental Products) and (2) C&B Metabond (Parkell) systems with and without the use of Adlloy alloy. Class V buccal amalgam restorations (n = 132) were subjected to one of two surface treatments: (1) sandblasting or (2) sandblasting plus Adlloy treatment. Mandibular premolar brackets were bonded with Concise composite resin or C&B Metabond (adhesive) to amalgam surfaces. All specimens were stored in 37 degrees C water for 10 weeks and subjected to thermocycling before bond strength testing. The laboratory shear bond strength of Concise material to amalgam was not improved after Adlloy modification. However, Adlloy-treated amalgam significantly increased the laboratory shear bond strength of orthodontic brackets bonded with C&B Metabond material. The majority (58%) of the bond failures of C&B Metabond bonded to non-Adlloy treated-amalgam occurred at the amalgam-adhesive interface, whereas the majority (58%) of the bond failure of C&B Metabond bonded to Adlloy-treated amalgam failed within the adhesive. Fracture within the amalgam during debonding was observed with C&B Metabond bonded to sandblasted amalgam (21%) and Adlloy-treated amalgam (15%). Regardless of Adlloy treatment, C&B Metabond would appear to provide adequate orthodontic bonding to amalgam; however, there may exist a potential risk of amalgam restoration fracture upon debonding.

Infection control in the orthodontic office in Canada.

Because of the difficulty of identifying infected persons, current recommendations for infection control are to treat all patients as if they are infected with blood-borne pathogens such as human immunodeficiency virus (HIV) and the hepatitis viruses. Dentists' compliance with these recommendations has been investigated previously, however, there are few data related to orthodontists. The objective of this study was to measure the proportion of orthodontists who report the use of recommended infection control procedures and to compare the infection control practices of orthodontists and general dentists. A mailed survey with three follow-up attempts was administered to all orthodontists and general dentists in Ontario (N = 5441) in 1994. There were significant differences in the routine use of gloves (orthodontists 85%, general dentists 92%); masks (orthodontists 38%, general dentists 75%); protective eyewear (orthodontists 60%, general dentists 84%); changing gloves after each patient (orthodontists 84%, general dentists 96%); and heat sterilization of handpieces (orthodontists 57%, general dentists 84%). Hepatitis B virus (HBV) vaccination of all clinical staff was reported by 46% of orthodontists, compared with 61% of general dentists (p < 0.001). Reports of HBV vaccination of orthodontists (94%) and general dentists (92%) were not significantly different. The use of additional precautions for patients with HIV was reported by 80% of orthodontists and 78% of general dentists. More education is required to promote the use of universal precautions by both general practitioners and orthodontists. Increased use of barrier methods, HBV vaccination of clinical staff, and heat sterilization of handpieces is required to reduce the potential for cross infection in the orthodontic practice. This is particularly important with the increasing number of microorganisms that are resistant to antibiotics.

Orthodontic retention.

This article briefly describes several factors that should be considered during orthodontic retention. These factors may influence occlusal stability following the completion of the active phase of orthodontic therapy. Orthodontic retention is an important part of orthodontic treatment. It should always be considered and included in the initial stages of treatment planning, rather than added on at the end of treatment as an after-thought.

Male postpubertal facial growth in Class II malocclusions.

Maxillary and mandibular postpubertal growth changes were assessed from lateral cephalograms taken when subjects were 16 and 20 years of age. The sample consisted of 39 male subjects with no previous orthodontic treatment who exhibited Class II skeletal characteristics. Significant increases in mean maxillary and mandibular measurements were observed over the age period studied. Mean mandibular growth (Co-Gn) was approximately three times that of maxillary growth (Co-A). Total mandibular growth observed between 16 to 20 years of age was approximately 4.3 mm. The mandible appeared to rotate anteriorly superiorly, reflected by a mean reduction in mandibular plane angle of 1.47 degrees and a greater increase in posterior versus anterior face height. There were not statistically significant changes in incisor angulation. Mean growth changes in this Class II sample were comparable to those previously reported for male subjects with Class I malocclusions over the same age period, suggesting a similarity in postpubertal development between these two groups.

Evaluation of an anamnestic questionnaire as an instrument for investigating potential relationships between orthodontic therapy and temporomandibular disorders.

A group of 100 patients who received orthodontic treatment, between the ages of 16 to 31 years, were asked to complete the TMJ Scale (an anamnestic temporomandibular disorder [TMD] questionnaire) and undertake a simple clinical TMD examination, the Helkimo clinical dysfunction index. The purpose of this study was to compare the TMJ Scale and the Helkimo clinical dysfunction index to validate the use of the TMJ Scale as a potential method with which to examine whether there is any relationship between TMD and orthodontic therapy. Comparisons between TMJ Scale scores from the orthodontically treated group were made with previously reported TMJ Scale data. In addition, comparisons were made between various treatment and malocclusion groups identified within the orthodontically treated sample. On the basis of the TMJ Scale global scale scores for the orthodontically treated group and two normative nontemporomandibular disorder groups described by Levitt, Lundeen, and McKinney, no differences were observed. Similarly, TMJ Scale comparisons between various treatment and malocclusion subgroups showed no statistically significant differences. The results of this study support the use of the TMJ Scale as a valid instrument with which to determine whether there is any relationship between orthodontic therapy and TMD.

Facial growth in females 14 to 20 years of age.

The objective of this study was to determine the magnitude and the direction of postpubertal mandibular and maxillary facial growth in females. The sample consisted of 37 untreated subjects who had Class I skeletal and dental characteristics and whose lateral cephalograms were taken at 14, 16, and 20 years of age. Mandibular growth was determined to be significant for the age periods of 14 to 16 years and 16 to 20 years. Overall mandibular growth as measured from Co-Gn was approximately twice that of the overall maxillary growth as measured from Co-A. Correlation analysis revealed a statistically significant relationship between the estimates of incremental mandibular growth from either articulare or condylion. The mandibular growth rate was found to be twice as large for age period 14 to 16 years as for age period 16 to 20 years. The increase in posterior vertical face height was slightly more than the increase in anterior vertical face height. The mandibular plane angle decreased 1.1 degrees during the age period of 14 to 20 years, suggesting a tendency for a closing rotation of the mandible. Mandibular incisors appeared to tip labially with advancing age. Although variable, the potential for significant maxillary and mandibular facial growth in females during late adolescent has been demonstrated.

Orthodontic therapy in the patient treated with cyclosporine.

Cyclosporine is an immunosuppressive drug that is gaining widespread use in the treatment of a variety of disorders. Gingival hyperplasia, a common side effect of cyclosporine therapy, has significant implications for orthodontic treatment, especially as the drug becomes more widely used to treat diseases prevalent in adolescents. A 5-year study of a group of patients with type 1 diabetes who were receiving cyclosporine treatment revealed a series of findings that are of importance to the orthodontist, including the potential for orthodontic appliances to increase the severity of the induced gingival enlargement and the potential of the gingival hyperplasia to complicate orthodontic therapy. Guidelines to minimize the degree of cyclosporine-induced gingival enlargement in the orthodontic patient are suggested.

Facial growth in males 16 to 20 years of age.

Postpubertal craniofacial skeletal and dental changes were examined from lateral cephalograms taken when subjects were 16, 18, and 20 years of age. The sample consisted of males with no previous orthodontic treatment who had Class I skeletal and dental characteristics. Mandibular growth was found to be statistically significant for the age periods of 16 to 18 years and 18 to 20 years. Growth from 16 to 18 years was greater than that from 18 to 20 years. Maxillary and mandibular growth were highly correlated at each age period. However, overall mandibular growth was approximately twice that of overall maxillary growth. Mandibular growth was found to involve an upward and forward rotation, a result of posterior vertical growth exceeding anterior vertical growth. Lower incisors were found to tip lingually with increasing age. Incremental changes in mandibular cephalometric measurements were found to be equivalent when measured from either articulare or condylion, indicating the interchangeability of the landmarks for growth estimates.

Mandibular response to orthodontic treatment with the Bionator appliance.

A group of 20 subjects who underwent successful Bionator treatment was compared with 20 subjects who were treated less successfully with the same appliance. Both groups had similar advancements in their bite registrations, as well as similar treatment times and growth-prediction parameters. Success was judged not on the final occlusion (all patients were treated to a Class I molar relationship) but on the posttreatment position of skeletal pogonion. The successful group experienced 3.5 mm or more of advancement in skeletal pogonion, whereas the less successful group had less than 3 mm of advancement of this point. The two groups were comparable in all features except, as may be expected, total mandibular growth, which was greater in the group with the larger anterior pogonion advancement. The results of this study suggest that persons who have small mandibles (as determined by comparison with published growth standards) may benefit more from functional appliance therapy than patients with normal-sized mandibles. The subjects with delayed growth may experience more mandibular development than those with average growth during treatment under the favorable growth environment created by functional appliance therapy.

Facial changes in children treated with the Activator appliance: a lateral cephalometric study.

Using lateral cephalometry, facial profile changes in 32 children treated with the Activator appliance were assessed and compared to profile changes in 12 untreated children of same age and with similar malocclusions. The results of this study indicated that the maxillary region of the facial profile underwent similar changes in both groups. In contrast, the mandibular changes were different, with the treated group showing more mandibular advancement than the untreated group during the period examined.

Orthodontic treatment of impacted first permanent maxillary molars.

The etiology and treatment of impacted first maxillary molars has been reported. Appliance selection criteria, as well as treatment planning considerations have also been discussed. Although impacted first maxillary molars can be treated with either fixed or removable orthodontic appliances, the selection of the appliance should be based on the overall severity of the malocclusion.

Linear changes of the maxillary and mandibular lips.

This investigation was designed to assess the growth effect on the linear dimensions of human lips from childhood to adulthood. By means of serial computerized cephalometry, the changes in lip length and thickness were studied in 32 untreated male and female subjects from 8 to 18 years of age. It was observed that the maxillary and mandibular lips, under the influence of growth, increase in both dimensions with the advancement of age. During the period studied, the length and thickness of the lips of the male subjects exhibited greater increases both proportionally and numerically than the corresponding dimensions of female lips.

The effects of Fränkel II treatment on arch width and arch perimeter.

Changes in dental arch width and total arch perimeter in 24 Class II, Division 1 patients treated with the Fränkel II appliance were compared with changes in an untreated control group. Measurements were made on pretreatment and posttreatment plaster casts at three points on each of four maxillary and four mandibular teeth. Increases in width were computed at the occlusal point and compared for the two samples. A significant increase in occlusal arch width for all measures was suggestive of both a minor tipping movement of the maxillary teeth and a bodily movement of the mandibular teeth. Width development in the maxilla was greater than in the mandible. Occlusal arch width increased more in the molar and premolar regions in the maxilla and in the premolar region in the mandible. Wide arches were found to have as much increase as narrow arches. The total arch perimeter decreased significantly less in the treatment sample than in the control sample. The documented gains in arch width and arch perimeter would not be sufficient to relieve severe crowding, but could be useful in avoiding removal of teeth in borderline extraction cases.

The depth of the mandibular antegonial notch as an indicator of mandibular growth potential.

The craniofacial characteristics and growth potential of 25 orthodontically treated patients with deep mandibular antegonial notch were compared with a similar group of 25 shallow notch subjects by the use of longitudinal lateral cephalometric radiographs. Deep notch cases had more retrusive mandibles with a shorter corpus, smaller ramus height, and a greater gonial angle than did shallow notch cases. The lower facial height in the subjects with a deep mandibular notch was found to be longer, and both the mandibular plane angle and facial axis were more vertically directed. During the average 4-year period examined, the deep notch sample experienced less mandibular growth as evidenced by a smaller increase in total mandibular length, corpus length, and less displacement of the chin in a horizontal direction than did the shallow notch sample. The results of this study suggest that the clinical presence of a deep mandibular antegonial notch is indicative of a diminished mandibular growth potential and a vertically directed mandibular growth pattern.

Cephalometric changes associated with treatment using the activator, the Fränkel appliance, and the fixed appliance.

Treatment with the activator, the Fränkel appliance, and the edgewise appliance was compared in three separate groups; each group consisted of twenty-five nonextraction cases of Class II, Division 1 malocclusion. Hard- and soft-tissue profile changes caused by growth and treatment were assessed by means of pretreatment and posttreatment lateral cephalograms. Anterior movement of A point was 1.6 mm more in the activator group than in the fixed-appliance group. The most anterior point on the maxillary incisor moved 1.5 mm more distally in the fixed-appliance sample than in the functional groups. Among the three groups, the activator sample showed the most anterior movement of the mandible (2.3 mm); the fixed group showed the least (0.6 mm). The fixed-appliance group showed more posterior rotation of the mandible than the activator group. However, relative to cranial base, the movement of the mandibular symphysis was not statistically different in the three groups. There were little differences among the treatment groups with regard to changes in the soft-tissue profile. In clinical terms, there was a remarkable similarity in the changes that occurred in the three treatment groups.

Growth of lips in two dimensions: a serial cephalometric study.

The effect of growth on the cross-sectional area of the lips was studied radiographically on 168 lateral cephalometric films of 28 persons, taken every 2 years from the age of 8 to the age of 18 years. All subjects studied had received no orthodontic treatment, and the total lip outline as it is seen on the lateral cephalogram was traced and calculated by computerized cephalometry. This method of calculating the total lip area, instead of relating lip growth to a single lip point, was selected in order to avoid any effect that positional changes of the lips may have and subsequently superimpose on lip changes resulting from growth. Increase in total lip area, in both numerical and proportional terms, was observed from age 8 to age 18 years. The largest incremental growth increase for both lips took place between the ages of 12 and 14 years, while no significant changes were observed after the age of 16. Tested growth changes for sex differences revealed statistically significant sexual dimorphism, with larger maxillary lip area in males at ages 10, 12, 14, 16, and 18 and larger mandibular lip area at 18 years of age, while the females showed significantly larger mandibular lip area at age 12.