Comparison of Contamination of Low-Frictional Elastomeric Rings with That of Conventional Elastomeric Rings by Streptococcus mutans - An In-vivo Study.

INTRODUCTION: The presence of brackets and ligatures has been shown to be related to an increase in gingival inflammation and increased risk of decalcification. The various measures were taken to reduce the plaque accumulation and also lot of efforts were made by manufacturers that reduced the binding friction between the ligature rings and arch wire that facilitated easy sliding of the tooth through the wire. The low frictional ligatures rings manufactured by different manufacturers presumed to attract fewer bacteria due to greater reduction in surface roughness. Our study aimed to evaluate whether the low frictional elastomeric rings accumulate fewer bacteria than conventional ligature rings. MATERIALS AND METHODS: Thirty patients (15 males and 15 females) who underwent fixed appliance therapy were selected. The study was done using split-mouth design. In each volunteer, synergy low frictional elastomeric rings were tied to brackets bonded to the maxillary premolar on the right side and mandibular premolar on the left side. Conventional elastomeric rings that served as control group were tied to the contralateral teeth, with the same design. Samples were collected after four weeks (28 days) and cultured for bacteria Streptococcus mutans. RESULTS: There was no statistical difference between Streptococcus mutans count in low frictional elastomeric rings with that of conventional rings. CONCLUSION: We concluded that adherence of Streptococcus mutans is similar in both synergy low frictional elastomeric rings and conventional clear elastomeric rings and thus the manufacturer's claim of minimal bacterial adherence was discarded.

Evaluation of hyoid bone position and its correlation with pharyngeal airway space in different types of skeletal malocclusion.

INTRODUCTION: The hyoid bone and its relation with the pharyngeal space in health and disease has been an intriguing subject for years. AIM: This study attempts to evaluate the hyoid bone position and to ascertain any correlations with pharyngeal airway space in skeletal class I, II, and III malocclusions. MATERIALS AND METHODS: McNamara's airway analysis was carried out to assess the upper and lower airway widths and Hyoid triangle analysis by Bibby and Preston was carried out to determine the position of the hyoid bone. CONCLUSION: A positive correlation was found between the lower airway and horizontal distance from the hyoid bone to the retrognathion in class I skeletal pattern with average growth pattern.

Determination of optimum adhesive thickness using varying degrees of force application with light-cured adhesive and its effect on the shear bond strength of orthodontic brackets: an in vitro study.

AIM: The thickness of the adhesive layer under a bracket may be an important factor that affects the final tooth position and bond strength. With increasing use of preadjusted brackets, it is important to ensure that a consistently even layer of composite is placed under each bracket to take full advantage of bracket design and to avoid the need for compensatory bends to be placed in the archwire. Therefore, the present study is aimed at determining the optimum adhesive thickness by varying the force of application and observing the effect on the shear bond strength of orthodontic brackets. METHODS: Sixty premolars extracted for orthodontic purposes were divided into three groups of 20 samples each. Adhesive thickness was measured by varying the force of application while bonding brackets with light-cured adhesive and tested on a universal testing machine to evaluate the shear bond strength. RESULTS: The study showed that adhesive thickness is inversely proportional to applied force. In addition, the shear bond strength has a tendency to increase with a decrease in adhesive thickness up to a certain extent and then decrease. CONCLUSION: Adhesive thickness between bracket base and tooth surface decreases with an increase in the amount of force application from 1 to 3 oz. Mean shear bond strength increases when adhesive thickness decreases from 0.99 to 0.83 mm, and then it has a tendency to decrease when adhesive thickness decreases to 0.72 mm. Optimum adhesive thickness should be considered to be 0.83 mm, which is the thickness required to achieve sufficient bond strength to prevent chances of bond failure.

Three-dimensional finite element analysis of strength, stability, and stress distribution in orthodontic anchorage: a conical, self-drilling miniscrew implant system.

INTRODUCTION: The aims of this study were to analyze the stress distribution and displacement patterns that develop in an orthodontic miniscrew implant and its surrounding osseous structures for 2 implant materials under horizontal and torsional loading, with no ossseointegration. METHODS: A numeric approach was adopted. The finite element method was used to determine the stress and displacement of the various components at a given time after miniscrew implant application, when, due to viscoelastic relaxation effects, the only remaining stress field was from the application of the orthodontic load. RESULTS: Stress distribution was not significantly different between the 2 types of implant material. Increased stress values were located at the necks of the implants and the surrounding cortical bone. Bending of the titanium miniscrew was observed in the neck region under horizontal traction. CONCLUSIONS: The differences between the values of stress and displacement we obtained for the 2 types of miniscrew were too small to be clinically significant. Optimization of the miniscrew implant composed of the titanium alloy might be achieved by increasing the bulk (quantity) of the material in the neck region. The miniscrew implant can be immediately loaded and used for group movement of teeth.

Efficiency, behavior, and clinical properties of superelastic NiTi versus multistranded stainless steel wires: a prospective clinical trial.

OBJECTIVE: To investigate efficiency, behavior, and properties of superelastic NiTi vs multistranded stainless steel wires in Begg and preadjusted edgewise appliance (PEA) under moderate to severe crowding conditions. MATERIAL AND METHODS: Ninety-six participants (48 male, 48 female), aged 12-18 years old (mean age  =  15.2 ± 1.95), with moderate (≤ 6 mm; mean  =  5.3 ± 0.48) to severe (> 6 mm; mean  =  7.9 ± 0.66) initial crowding were distributed into four groups: superelastic NiTi PEA (n  =  24), superelastic NiTi Begg (n  =  24), multistranded (coaxial) stainless steel PEA (n  =  25), and multistranded (coaxial) stainless steel Begg (n = 23). In this study, 0.16-inch superelastic (austenitic active) NiTi and 0.175-inch multistranded (six stranded, coaxial) stainless steel wires were used in a 0.022-inch slot (Roth prescription) PEA and Begg appliance with a follow-up of six weeks. RESULTS: Analysis of variance revealed no significant difference in reduction of crowding between superelastic NiTi PEA and multistranded (coaxial) stainless steel PEA groups, but reduction in crowding was significantly greater in the superelastic NiTi Begg group compared with the multistranded (coaxial) stainless steel Begg group with F (3, 44)  =  8.896, P < .001, and effect size (ω) 0.57 in moderate crowding and F (3, 44)  =  122.341, P < .001, and effect size (ω) 0.93 in severe crowding. Linear regression demonstrated significant (P < .05) positive correlation between amount of initial crowding and reduction in crowding in all groups except the multistranded (coaxial) stainless steel Begg group, wherein a negative correlation did exist. CONCLUSION: Superelastic NiTi performed significantly better than multistranded (coaxial) stainless steel wire in the Begg appliance. However, in PEA, there was no significant difference.

Cephalometric comparison of vertical changes between Begg and preadjusted edgewise appliances.

The purpose of this retrospective study was to quantify and compare the vertical dimensional changes in bialveolar dental protrusion patients undergoing extraction of all four first premolars between the preadjusted edgewise appliance (PEA) and the Begg appliance. The cephalometric records of 55 patients (14 males and 41 females) with Class I bimaxillary protrusion were selected and divided into two groups based on the appliance used, i.e Begg or PEA mechanotherapy. To minimize the effects of growth, the subjects were at least in stage VI of skeletal maturation. The mean age was 18.25 ± 3.2 years for the Begg group and 18.03 ± 3.5 years for the PEA group. Skeletal and dental changes were analysed in both groups on lateral cephalograms taken pre- (T1) and post- (T2) treatment. A Student's t-test was used to analyse the treatment changes. Within group results showed a significant increase in face height and extrusion and mesial movement of the upper and lower molars for both groups. However, no significant differences were observed when the groups were compared. A significant correlation was found between the change in lower molar to mandibular plane angle and lower anterior face height for both groups. No significant difference was found when the Begg mechanotherapy was compared to the PEA technique on vertical dimensional changes. It can be speculated that mesial movement of the molars tended to keep pace with their extrusion and negated any bite opening effect with both mechanotherapies.

Evaluation of antimicrobial and physical properties of orthodontic composite resin modified by addition of antimicrobial agents--an in-vitro study.

INTRODUCTION: This study was designed to investigate the antimicrobial and physical properties of orthodontic composite resin modified by the addition of antimicrobial agents. METHODS: Unite bonding adhesive (3M Unitek, Monrovia, Calif), a chemically cured composite resin, modified by the addition of benzalkonium chloride (BAC), chlorhexidine, and triclosan in concentrations of 0.1 wt%, 0.2 wt%, and 0.3 wt%, respectively, was formed into tablets for testing. The tablets of each group and a control group were subjected to the agar plate diffusion test to measure the zone of bacterial inhibition. In addition, they were incubated for 24 hours in tryptic soy broth inoculated with Streptococcus mutans and examined for bacterial growth. A total of 80 extracted premolars were collected and divided into 2 sets of 40 teeth each. Stainless steel Begg brackets were bonded by using control and experimental composites. A universal testing machine was used to determine shear bond strength. The first set of teeth was tested after 24 hours and the second set after 25 days of storage in distilled water. Time-dependent release of antimicrobial agents from the modified composites was monitored spectrophotometrically. RESULTS AND CONCLUSIONS: The findings indicated that (1) addition of BAC to the orthodontic composite resin enhanced its antimicrobial properties, (2) there was no significant difference in the bond strengths of the control and the experimental resin tested after 24 hours and 25 days, and (3) maximum release of BAC from the modified resin was higher than that of chlorhexidine or triclosan, and was much higher than the minimum inhibitory concentration level.