Effect of ovarian activity on orthodontic tooth movement and gingival crevicular fluid levels of interleukin-1ß and prostaglandin E(2) in cats.

OBJECTIVE: To evaluate whether there is any correlation between ovarian activity and two potent bone-resorbing mediators (prostaglandin E(2) [PGE(2)], interleukin-1ß [IL-1ß]) secreted from the gingival crevicular fluid (GCF) during orthodontic tooth movement. MATERIALS AND METHODS: Eighteen female cats were included in this study. Animals were randomly divided into three groups (estrous, anestrous, and ovariectomized groups), each having six queens. Estrous was induced by administration of 150 IU equine chorionic gonadotropin (eCG) to queens of the estrous group. A closed-coil spring, applied with 80 g of tipping force to the canine, was attached between the maxillary canine and mini-implant. GCF was collected on days 0, 6, and 12 from each cat to examine PGE(2) and IL-1ß during orthodontic tooth movement in cats. The PGE(2) and IL-1ß levels were determined with enzyme-linked immunosorbent assay. RESULTS: There was no significant difference (P > .05) between anestrous and the ovariectomized groups in terms of tooth movement on days 6 and 12 of distalization. In contrast, tooth movement in the estrous group was lower (P < .05) than in the remaining two groups (anestrous and ovariectomized). The mean PGE(2) and IL-1ß levels of the canine teeth of the estrous groups were significantly lower than the remaining two groups on days 6 and 12 (P < .05) of coil spring applications. CONCLUSIONS: These results indicate that ovarian activity can affect orthodontic tooth movement and GCF levels of IL-1ß and PGE(2) in cats.

Effects of silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets.

OBJECTIVE: The aim of this study was to evaluate the effects of tribochemical silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets. MATERIAL AND METHODS: Twenty debonded metal and 20 debonded ceramic brackets were randomly assigned to receive one of the following surface treatments (n=10 for each group): (1) sandblasting (control); (2) tribochemical silica coating combined with silane. Brackets were rebonded to the enamel surface on the labial and lingual sides of premolars with a light-polymerized resin composite. All specimens were stored in distilled water for 1 week and then thermocycled (5,000 cycles) between 5-55ºC. Shear bond strength values were measured using a universal testing machine. Student's t-test was used to compare the data (α=0.05). Failure mode was assessed using a stereomicroscope, and the treated and non-treated bracket surfaces were observed by scanning electron microscopy. RESULTS: Rebonded ceramic brackets treated with silica coating followed by silanization had significantly greater bond strength values (17.7±4.4 MPa) than the sandblasting group (2.4±0.8 MPa, P<0.001). No significant difference was observed between the rebonded metal brackets treated with silica coating with silanization (15±3.9 MPa) and the sandblasted brackets (13.6±3.9 MPa). Treated rebonded ceramic specimens primarily exhibited cohesive failure in resin and adhesive failure at the enamel-adhesive interface. CONCLUSIONS: In comparison to sandblasting, silica coating with aluminum trioxide particles followed by silanization resulted in higher bond strengths of rebonded ceramic brackets.

Maxillary and mandibular mesiodistal tooth sizes among different malocclusions in a sample of the Turkish population.

The purpose of this study was to establish normative data for mesiodistal tooth crown dimensions with respect to malocclusions and gender differences in Turkish sample. The subjects were randomly selected and assigned to three malocclusion groups according to Angle's classification. Each group consisted of 100 individuals between the ages of 13 and 18 years with the following distribution: Class I, 42 males and 58 females; Class II, 52 males and 48 females; and Class III, 51 males and 49 females. An electronic digital calliper was used to measure the mesiodistal tooth width from the right second permanent molar to the left second permanent molar on both upper and lower study casts. For statistical evaluation, one- and two-way analyses of variance and post hoc Tukey's honestly significant difference (HSD) tests were performed. There were statistically significant differences for the maxillary canine (P < 0.001), first premolar (P < 0.05), second molar (P < 0.05), and mandibular canine (P < 0.01) for males, and for all maxillary teeth and the mandibular central (P < 0.05), canine (P < 0.001), and first premolar (P < 0.05) teeth in females among the malocclusion groups. When Angle's classification was evaluated, significant differences were determined, except for the first and second mandibular molars. All mesiodistal widths were also found to be statistically different according to gender dimorphism. A significant relationship was found between mesiodistal tooth size, Angle's classification, and gender. Therefore, tooth dimensions may play a crucial role in treatment planning and in achieving satisfactory interdigitation of the upper and lower dentition following the completion of orthodontic treatment.

Effects of thermocycling on the degree of cure of two lingual retainer composites.

The aim of this study was to evaluate the effects of thermocycling on the degree of cure (DC) and water sorption behavior of two lingual retainer composites. A total of 50 composite specimens, 5 mm diameter and 2 mm height, were prepared using Light Cure Retainer (LCR) (Reliance) and Transbond Lingual Retainer (TLR) (3M Unitek). After 40-second curing with a halogen light and after 24-hour water storage, the composite specimens were subjected to different thermocycling regimes. Absorbance peaks to monitor the DC were recorded using Fourier transform infrared (FTIR) spectroscopy, while water sorption was calculated in microg/mm(3). On DC, significant differences among the different thermocycling regimes were observed only for the TLR specimens (p<0.05). On water sorption behavior, an increase in the number of thermal cycles resulted in increased water sorption for both composites, but the statistical differences in these groups were not significant. On the effect of thermocycling up to 20,000 cycles, present findings showed that LCR was less affected than TLR. Further, LCR exhibited higher DC and lower water sorption values than TLR after thermal cycling.

Bond strength of ceramic brackets bonded to enamel with amorphous calcium phosphate-containing orthodontic composite.

The aim of this in vitro study was to compare the shear bond strength (SBS) and failure modes of a conventional resin-based composite with a recently developed amorphous calcium phosphate (ACP)-containing orthodontic composite system. Forty freshly extracted human maxillary premolar teeth were randomly divided into two equal groups. Conventional composite (group 1; Transbond-XT; 3M Unitek) and ACP-containing orthodontic composite (group 2; Aegis-Ortho; Harry J. Bosworth Co.) were used for bonding ceramic orthodontic brackets. The SBS of these brackets were measured and recorded in megapascals (MPa). Adhesive remnant index (ARI) scores were determined after bracket failure. Data were analysed with a Student's t-test for two independent variables and Pearson's chi-square tests. Statistical analysis showed that the bond strength of group 1 (mean: 36.7 +/- 6.8 MPa) was significantly higher than group 2 (mean: 24.2 +/- 5.4 MPa; P < 0.01). Although a greater percentage of the fractures were cohesive at the composite interface (Score 1 + Score 2 = 70 per cent in group 1 and 90 per cent in group 2), statistically significant differences were observed between the groups (P < 0.05). The ACP system is suitable for bonding ceramic orthodontic brackets due to the lower SBS values compared with conventional composite. The ACP-containing composite is recommended for use in clinical orthodontic practice in order to achieve lower decalcification scores under ceramic orthodontic brackets.

Effects of different chlorhexidine formulations on shear bond strengths of orthodontic brackets.

OBJECTIVE: To test the hypothesis that the application of different chlorhexidine formulations to the etched enamel will not affect shear bond strength (SBS). MATERIALS AND METHODS: Forty-four freshly extracted human premolars were collected and stored in distilled water. The teeth were etched with 37% phosphoric and were rinsed and dried. The teeth then were divided into four equal groups. While Group 1 served as a control, Groups 2 to 4 were treated before bonding with a chlorhexidine formulation that included solution (2%), gel (1%), and mouthwash (0.2%). Orthodontic brackets were bonded with Transbond XT (3M Unitek, Monrovia, Calif). Bond strength results were evaluated with the use of one-way analysis of variance (ANOVA) (P < .05) and post hoc tests. Modes of failures were verified by means of scanning electron microscopy. RESULTS: Although no statistically significant difference was observed between Groups 1 and 4 (P > .05), both were statistically superior to Groups 2 and 3 (P < .05). In this in vitro study, the observed measures for Groups 2 and 3 (14.5-10.6 MPa) were lower than those for Groups 1 and 4 (27.3-24.9 MPa), but these values were much higher than those required for clinical use (6-8 MPa). CONCLUSION: The hypothesis is rejected. The application of chlorhexidine mouth rinse before bonding had no significant effect on the SBS value, and the application of chlorhexidine solution and gel significantly decreased SBS.

Influence of different tooth types on the bond strength of two orthodontic adhesive systems.

The aim of this investigation was to evaluate the effects of different tooth types on the shear bond strength (SBS) of two orthodontic resin adhesive systems in vitro. Two hundred extracted sound human teeth were used in the study. Ten teeth of each tooth type were the mounted in acrylic resin leaving the buccal surface of the crowns parallel to the base of the moulds. In each experimental group, the adhesives (Transbond XT and Light Bond) were applied to the etched enamel surfaces. The orthodontic composite resins were then applied to the surface in cylindrical-shaped plastic matrices. For SBS testing, a force transducer (Ultradent) was applied at a crosshead speed of 1 mm/minute at the interface between the tooth and composite until failure occurred. Data were analysed using two-way analysis of variance (ANOVA), Kruskal-Wallis one-way ANOVA, a Bonferroni adjusted Mann-Whitney U-test, and an independent t-test. Generally, it was found that tooth type had a significant effect on SBS (P < 0.05) with Light Bond showing a higher SBS than Transbond XT (P < 0.05). The highest bond strengths were observed for the upper central incisor and lower molars with Light Bond (P < 0.05) and the lowest mean bond strengths for the upper molars and lower canine with Transbond XT (P <0.05). The results demonstrated that enamel SBS was significantly altered by both tooth type and adhesive system. Thus, the findings of this study confirm that enamel bond strength is not uniform for all teeth. These results may also explain the variability in the enamel-bonding efficacy of adhesives.