Histological evaluation of orthodontic tooth movement following low level laser irradiation in rabbits.

BACKGROUND: Reduction of orthodontic treatment time is a major concern for orthodontists. Low level laser therapy (LLL) has been widely used in dentistry and it has been claimed that it could stimulate bone formation. OBJECTIVE: The aim of the present study was to evaluate histological effects of LLL on alveolar bone remodeling during experimental tooth movement in rabbits. METHODS: In this experimental study which was performed in the animal lab of Mashhad Dental School in 2016 twenty pre-pubertal female albino rabbits with the mean age of 8±1 weeks were randomly assigned into two groups. All the rabbits were examined by a veterinarian, and underweight or diseased rabbits were excluded from the study. Fifty gram orthodontic force was applied via 0.014 stainless steel spring on central teeth in both groups. In the first group, low level laser KLO3 (wave length: 980 nm, Power: 80mw) was irradiated three minutes from the buccal aspect of central teeth for 21 days. In the second group, rabbits were not exposed to laser irradiation and served as our control group. After this period, the distance between mesial corners of incisors was measured blindly by a caliper calibrated as 0.1mm. All rabbits in both groups were sacrificed by vital perfusion for histological evaluation to determine the number of resorption lacuna and amount of fibrous tissue. Independent sample t-test was used to analyze the data. RESULTS: The number of resorption lacuna, the rate of tooth movement and fibrous tissue were significantly greater in the lased group (p=0.05). CONCLUSION: Low level laser irradiation could accelerate tooth movement in rabbits via increased resorptive activity in alveolar bone.

Static and kinetic frictional forces of silica-insert ceramic brackets with coated archwires in artificial saliva.

BACKGROUND: During sliding mechanics, the frictional force (FF) is an important counterforce to orthodontic tooth movement. The purpose of this in vitro study was to investigate the static and kinetic FFs of S silica-insert ceramic (SIC) brackets with Teflon-coated (TC) and conventional S stainless steel (SS) archwires. MATERIALS AND METHODS: The target group of this study included 80 maxillary canine 0.022 inch slot SIC brackets. Forty SS brackets were used as the control. TC and conventional uncoated SS archwires of different dimensions (0.016, 0.018, 0.016 × 0.022, and 0.018 × 0.025 inch) were examined. All tests were carried out under artificial saliva injected condition. Scanning Electron Micrographs were prepared for two samples of coated and uncoated archwires. Analysis of variance and Tukey post hoc tests were used for statistical purposes (level of significance P < 0.05). RESULTS: SIC brackets showed significantly lower levels of FFs than SS brackets. TC archwires had greater frictional values than conventional uncoated ones. They also exhibited an unusual behavior of increasing kinetic FFs with time. Indentation and delamination of coating were obvious under scanning electron microscopy observations. CONCLUSION: From the standpoint of friction, SIC brackets may serve well, even better than SS brackets, in sliding mechanics. The coating layer of the archwires may delaminate and lost, causing an impediment to tooth movement.

The effect of fractional CO2 laser irradiation on remineralization of enamel white spot lesions.

This study investigated the combined effect of fractional CO(2) laser irradiation and fluoride on treatment of enamel caries. Sixty intact premolars were randomly assigned into four groups and then stored in a demineralizing solution to induce white spot lesions. Tooth color was determined at baseline (T1) and after demineralization (T2). Afterwards, the teeth in group 1 remained untreated (control), while group 2 was exposed to an acidulated phosphate fluoride (APF) gel for 4 min. In groups 3 and 4, a fractional CO(2) laser was applied (10 mJ, 200 Hz, 10 s) either before (group 3) or through (group 4) the APF gel. The teeth were then immersed in artificial saliva for 90 days while subjected to daily fluoride mouthrinse and weekly brushing. Color examinations were repeated after topical fluoride application (T3) and 90 days later (T4). Finally, the teeth were sectioned, and microhardness was measured at the enamel surface and at 30 and 60 µ from the surface. In both lased groups, the color change between T1 and T4 stages (∆E(T1-T4)) was significantly lower than those of the other groups (p < 0.05). Laser irradiation followed by fluoride application (group 3) caused a significant increase in surface microhardness compared to APF alone and control groups (p < 0.05). Microhardness at depths of 30 and 60 µ was also significantly greater in group 3 compared to those of all other groups (p < 0.05). Application of a fractional CO(2) laser before fluoride therapy is suggested for recovering the color and rehardening of demineralized enamel.

Effect of changes in divine proportion on esthetic perception of smile in frontal view.

OBJECTIVES: In orthognathic surgery, the surgeon is capable of creating new dimensions to the patient's face. Because a beautiful smile could be related to the divine proportion, the purpose of the current study was to evaluate the changes in the perception of smile after approximating some components of smile to the divine proportion orthodontically or surgically. MATERIAL AND METHODS: Ten 20- to 25-year-old women with pleasant smiles and no obvious malocclusions participated in this study. Five standard photographs were taken from each participant in a posed smile, and the most natural one was selected and scanned into black and white pictures. Ten anthropometric landmarks were detected on each image and 10 ratios including Labial inferioris (Li)/right chelion (RCh)-right antegonion (RAgo), subnasale (Sn)-Li/left chelion (LCh)-left antegonion (LAgo), RCh-RAgo/labial superioris (Ls)-Li, LCh-LAgo/Ls-Li, Ch-Ch/Ls-Li,stomion (St)-Sn/St-Li, the maxillary central incisor width/maxillary centralincisor height, Ls-right cuspid (RCus)/RCh-RCus, Ls-left cuspid (LCus)/LCh-LCus, and LCus-RCus/Ch-Ch were measured on each picture. The numerators or denominators of the mentioned ratios were then changed in a way that mentioned the divine proportion (1/1.618) was approximated. All the 110 pictures were evaluated by 40 judges in 2 sessions using a visual analog scale. Intraclass correlation coefficient was also calculated (single measure, 0.644; F = 26.27; P < 0.001). The level of significance for this study was P = 0.05. The tests used to analyze the data were general linear model, the Friedman, and Wilcoxon tests. RESULTS: This study showed that LCus-RCus/Ch-Ch, Ls-Lcus/LCh-Lcus, and Ls-RCus/RCh-RCus (with mean scores of 64.2, 57.2, and 56.1, respectively) had the most positive effects on the esthetic perception of smile. However, RCh-RAgo/Ls-Li with a mean score of 29.1 and LCh-LAgo/Ls-Li with a mean score of 24.5 had the mostnegative effects. There were significant differences among the variables with each other except for A0 to J0 and A6 to J6 (F = 450.6; P = 0.001). CONCLUSIONS: Approximating the ratio RCus-LCus/Ch-Ch to the divine proportion may definitely help in achieving a more pleasant smile. On the next level, altering the ratios Ls-LCus/LCh-LCus and Ls-RCus/RCh-RCus could also play a role in making a beautiful smile.

A new method to correct lingual rolling of lower molars (Amini twister).

In this report, we present an uncomplicated approach to overcome lingual rolling of mandibular molars during orthodontic treatment, by using rectangular NiTi arch wire in twist fashion through the molar tube. The sequential steps of the twist manoeuvre on a typodont and a case report are exhibited in this article.

A new approach to correct a Class III malocclusion with miniscrews: a case report.

This report presents the treatment of a patient with skeletal Class III relationship in the permanent dentition caused by maxillary hypoplasia. The treatment plan called for palatal expansion and maxillary advancement. Titanium miniscrews were placed in the mandible to facilitate the maxillary protraction after maxillary expansion. An increase of projection of the upper jaw relative to the cranial base and to the lower jaw and significant improvement of the facial profile were observed.

Shear bond strength and antibacterial effects of orthodontic composite containing TiO2 nanoparticles.

Nanofillers can reduce enamel demineralization without compromising physical properties of the composite. The aim of this study was to evaluate shear bond strength (SBS) and antibacterial effects of an orthodontic composite after adding titanium oxide (TiO2) nanoparticles. Light cure orthodontic composite paste (Transbond XT) was blended with TiO2 nanoparticles. A total of 30 extracted premolars were randomly allocated into two groups of 15. In order to bond brackets, Transbond XT adhesive and nanocomposite were used in each group, respectively. SBS of two groups were determined, and the adhesive remnant index (ARI) scores were assessed. A total of 45 composite discs specimen were prepared. Of the 45 discs, 30 discs were made from nanocomposite and tested for antibacterial properties immediately and 30 days after curing by direct contact test. The antibacterial properties of the remaining 15 discs that were made from the conventional composite were tested immediately after curing as control group. Student's t-test and chi-square tests were used to analyse the data with the significance level of 0.05. No significant difference was found between SBS of conventional and nanocomposites, 24 hours after curing (P = 0.58). Chi-square test showed that ARI scores of two groups were not significantly different after debonding (P = 0.69). Comparison of antibacterial effects between conventional and nanocomposite demonstrated significant difference between two groups, with nanocomposites having a higher antibacterial activity (P = 0.03). Colony count revealed no significant difference in bacterial growth immediately and 30 days after curing in nanocomposite group. Adding TiO2 nanoparticles to orthodontic composite enhances its antibacterial effects without compromising the SBS.

In Vitro Cytotoxicity Assessment of an Orthodontic Composite Containing Titanium-dioxide Nano-particles.

Background and aims. Incorporation of nano-particles to orthodontic bonding systems has been considered to prevent enamel demineralization around appliances. This study investigated cytotoxicity of Transbond XT adhesive containing 1 wt% titanium dioxide (TiO2) nano-particles. Materials and methods. Ten composite disks were prepared from each of the conventional and TiO2-containg composites and aged for 1, 3, 5, 7 and 14 days in Dulbecco's Modified Eagle's Medium (DMEM). The extracts were obtained and exposed to culture media of human gingival fibroblasts (HGF) and mouse L929 fibroblasts. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results. Both adhesives were moderately toxic for HGF cells on the first day of the experiment, but the TiO2-containing adhesive produced significantly lower toxicity than the pure adhesive (P<0.05). No significant differences were found in cell viability percentages between the two groups on the other days (P>0.05). There was a significant reduction in cell toxicity with increasing pre-incubation time (P<0.001). L929 cells showed similar toxicity trends, but lower sensitivity to detect cytotoxicity of dental composites. Conclusion. The orthodontic adhesive containing TiO2 nano-particles indicated comparable or even lower toxicity than its nano-particle-free counterpart, indicating that incorporation of 1 wt% TiO2 nano-particles to the composite structure does not result in additional health hazards compared to that occurring with the pure adhesive.

Enamel resistance to demineralization following Er:YAG laser etching for bonding orthodontic brackets.

BACKGROUND: Several studies have shown that laser-etching of enamel for bonding orthodontic brackets could be an appropriate alternative for acid conditioning, since a potential advantage of laser could or might be caries prevention. This study compared enamel resistance to demineralization following etching with acid phosphoric or Er:YAG laser for bonding orthodontic brackets. MATERIALS AND METHODS: Fifty sound human premolars were divided into two equal groups. In the first group, enamel was etched with 37% phosphoric acid for 15 seconds. In the second group, Er:YAG laser (wavelength, 2 940 nm; 300 mJ/pulse, 10 pulses per second, 10 seconds) was used for tooth conditioning. The teeth were subjected to 4-day PH-cycling process to induce caries-like lesions. The teeth were then sectioned and the surface area of the lesion was calculated in each microphotographs and expressed in pixel. The total surface of each specimen was 196 608 pixels. RESULTS: Mean lesion areas were 7 171 and 7532 pixels for Laser-etched and Acid-etched groups, respectively. The two sample t-test showed that there was no significant difference in lesion area between the two groups (P = 0.914). CONCLUSION: Although Er:YAG laser seems promising for etching enamel before bonding orthodontic brackets, it does not reduce enamel demineralization when exposed to acid challenge.

Early versus delayed rebonding of orthodontic brackets.

OBJECTIVES: There are controversial reports regarding the effect of repeated bonding on shear bond strength (SBS) of orthodontic attachments. The aim of this study was to evaluate the SBS of brackets following early and delayed rebonding, and after employing different methods of composite removal. MATERIALS AND METHODS: Sixty eight premolars were randomly assigned into 4 groups. After initial debonding and recording the SBS, the adhesive remnants in the first group were removed by a round bur, in the second group by a green rubber wheel, and in the third and fourth groups by 12-fluted tungsten carbide burs, all of them connecting to a low speed handpiece. In the fourth group following adhesive removal, the teeth were kept in a simulated oral environment for one month. Then, rebonding was performed and the second SBS was measured. Two representative samples from each group were examined under a scanning electron microscope following adhesive removal. The data were analyzed by ANOVA, Paired sample t-test and Chi-Square test. RESULTS: In the first group, the rebonding strength was decreased significantly (p<0.05), while composite removal with a tungsten carbide bur or a green rubber wheel did not affect SBS significantly (p>0.05). Late rebonding of brackets had no effect on the SBS (p>0.05). CONCLUSIONS: Postponing rebonding to the next visit does not improve the SBS significantly. It is recommended to use a tungsten carbide bur or a green rubber wheel, and not a round bur for removing adhesive remnants following debonding of orthodontic brackets.

The effect of low level laser on condylar growth during mandibular advancement in rabbits.

INTRODUCTION: It has been shown that Low Level Laser (LLL) has a positive effect on bone formation. The aim of this study was to evaluate the effect of low level laser on condylar growth during mandibular advancement in rabbits. MATERIALS AND METHODS: Continuous forward mandibular advancement was performed in fourteen male Albino rabbits with the mean age of 8 weeks and the mean weight of 1.5 ± 0.5 kg, with acrylic inclined planes. The rabbits were randomly assigned into two groups after 4 weeks. LLL (KLO3: wave length 630 nm) was irradiated at 3 points around the TMJ, through the skin in the first group. The exposure was performed for 3 minutes at each point (a total of 9 minutes) once a day for 3 weeks. The control group was not exposed to any irradiation. The rabbits in both groups were sacrificed after two months and the histological evaluation of TMJ was performed to compare fibrous tissue, cartilage, and new bone formation in condylar region in both groups. Disc displacement was also detected in both groups. Student's t-test, Exact Fisher and Chi square tests were used for the statistical analysis. RESULTS: The formation of fibrous tissue was significantly lower, while bone formation was significantly greater in lased group as compared with control group. The thickness of cartilage did not differ significantly between two groups. CONCLUSION: Irradiation of LLL (KLO3) during mandibular advancement in rabbits, increases bone formation in condylar region, while neither increase in the cartilage thickness nor fibrous tissues was observed.

Evaluation of nasomaxillary growth of adolescent boys in northeastern Iran.

Anthropometry, a useful method for evaluating craniofacial soft tissues, makes the quantitative description of the face possible. It also assesses the degree of disharmony and imbalance in the growth and development of the face. The aim of this study was to examine the overall common age-related changes of nasomaxillary complex of adolescent boys in northeast Iran. Three- hundred- twelve 12 to 15 year-old boys voluntarily participated in this study. They were divided into three age groups (12-13, 13-14 and 14-15 year-old groups). Digital photographs of the subjects' faces were taken in Natural Head Position (NHP) frontal and profile views. After determination of the landmarks, nine anthropometric parameters including nasal length, mouth width, alar width, columella width, philtrum height, nasal width, nasolabial angle, nasal root slope angle and nasal index were measured by the Smile Analyzer software considering the magnification ratio of each image. One way ANOVA and Tukey test were used for statistical analyses. Significant differences between the three groups were detected in the mean alar, mouth and philtrum widths, nose length, nasolabial angle and nasal index (P<0.05). We did not find any significant differences in the mean nasal-root-slope angle and the mean philtrum height between the groups (P=0.29 and P=0.13, respectively). Aging of the facial profile is not a gradual process; it occurs in spurts and at different periods of life. During the studied time span, significant growth in nose width and nose length was obvious.

Porcelain conditioning with Nd:YAG and Er:YAG laser for bracket bonding in orthodontics.

In this study, shear bond strength (SBS) of metal orthodontic brackets to porcelain following conditioning by Er:YAG (erbium-doped yttrium aluminum garnet) and Nd:YAG (neodymium-doped yttrium aluminum garnet) laser in comparison to conventional methods was evaluated. One hundred glazed porcelain discs with an upper central shape were prepared and randomly assigned to five equal groups of 20. In the first group, samples were only deglazed and roughened by diamond burs. In the second group, after roughening and deglazing of porcelain samples, the samples were etched by 9.6% hydrofluoric acid for 4 min. Groups, 3, 4, and 5 were prepared by 0.8-W Nd:YAG laser, 2-W Er:YAG laser, 3-W Er:YAG laser for 10 s, respectively. Then, metal, mesh-based brackets were bonded to porcelain samples, and after being stored in distilled water for 24 h, debonding was carried out by a Zwick testing machine. ANOVA and Tukey tests were used to compare SBS in five groups. Mean SBS in groups 1 to 5 were 3.3 ± 1.6, 7.0 ± 2.1, 6.9 ± 2.7, 2.3 ± 1.1, and 3.7 ± 2.3 MPa, respectively. ANOVA test revealed a significant difference between five groups (p < 0.05). Although Tukey's test showed SBS in groups 2 and 3 were significantly higher than the other groups, they did not differ with each other significantly (p > 0.05). The results revealed that SBS of 9.6% hydroflouric acid and Nd:YAG Laser was in an acceptable range for orthodontic treatment. Nd:YAG laser was shown to be an acceptable substitute for hydrofluoric acid while Er:YAG laser with the mentioned power and duration was not a suitable option.

Uncomplicated treatment of ankylosed maxillary permanent canine: a case report.

This report describes the treatment of a young male patient with an ankylosed canine which had a high buccal position and during the fixed orthodontic therapy it was attempted to bring it into occlusion. This was finally accomplished by surgical luxation and extrusion of the tooth.

Cytotoxicity of orthodontic bonding adhesive resins on human oral fibroblasts.

There is little information concerning the cytotoxic effects of no-mix and flowable adhesives used in orthodontics. The aim of the present study was to evaluate the cytotoxic effects of a no-mix (Unite), a light-cured (Tranbond XT), and a flowable (Denfil Flow) adhesives on human oral fibroblasts. Twelve discs of each adhesive were prepared and aged for 1, 3, 5, and 7 days in Dulbecco's Modified Eagle's Medium (DMEM). Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the difference between the groups was tested by analysis of variance and Tukey tests (α = 0.05). After 1 day of storage, the no-mix adhesive showed moderate cytotoxic effects (P < 0.05), while the light-cured and flowable adhesives were essentially non-cytotoxic. Ageing considerably reduced the cytotoxicity of the no-mix adhesive. On days 5 and 7 of the experiment, the cell viability of three adhesives did not differ significantly (P > 0.05), but cell viability was slightly reduced on day 7. Moderate cytotoxic effects of no-mix adhesive on the first day of the experiment suggest that care should be taken to protect dentists and patients when these adhesives are being handled. Despite higher resin components, the flowable adhesive showed excellent biocompatibility.

Progesterone effects on experimental tooth movement in rabbits.

The effect of progesterone on tooth movement was evaluated for nine weeks. Twenty-four rabbits were assigned into three groups of long-term, short-term and no progesterone injection. Orthodontic force was applied to incisors for three weeks. Statistical tests showed no significant difference at the seventh and eighth week; but at the ninth week, tooth movement was significantly lower in the long-term group. Long-term progesterone administration could reduce the rate of tooth movement.

Are more nickel ions released from NiTi wires after sterilisation?

BACKGROUND: Increased concentrations of nickel ions may be released into saliva from recycled NiTi archwires. AIM: To compare the nickel ion concentrations released from recycled NiTi wires after sterilisation by either dry heat or steam autoclave. METHODS: Eighty preformed NiTi wires were assigned to four equal groups. In Groups 1, 2 and 3 the archwires were used intra-orally for 4 weeks. The Group 4 archwires were not used. Group 1 archwires were sterilised by dry heat, the Group 2 archwires were sterilised by steam autoclave, the Group 3 archwires were not sterilised and the Group 4 archwires were as-received. A 2 cm length, cut from each archwire, was immersed in artificial saliva for 4 weeks and the nickel ion concentrations in the artificial saliva measured with an atomic absorption spectrophotometer. RESULTS: There were no significant differences in the nickel ion concentrations released into the artificial saliva by each group of archwires (p = 0.467). CONCLUSION: Sterilisation of used NiTi wires by either dry heat and steam autoclave does not affect the concentrations of nickel ions released into artificial saliva.

Tooth size and arch dimension in uncrowded versus crowded Class I malocclusions.

AIM: The purpose of this investigation was to examine the extent to which arch dimension or tooth size contributes to dental crowding. METHODS AND MATERIALS: Two groups of dental casts were selected. Each group consisted of 30 pairs of dental casts including equal male and female samples. The first group had Class I malocclusions without crowding or spacing. The second group exhibited Class I malocclusions with severe dental crowding (> a 5 mm space deficiency). The following parameters were measured and used to compare the two groups: individual and collective mesiodistal tooth diameters, dental arch length, as well as buccal and lingual dental arch widths in the canine and molar regions. To compare the two groups the Student's t-test with 95% confidence interval was used. RESULTS: Statistically significant differences in both tooth diameters and transverse arch dimensions were found between the two groups. The crowded group was found to have a significantly smaller maxillary arch width and larger tooth size when compared with the uncrowded group. CONCLUSION: The results of this study suggest under equal conditions (a Class I skeletal relationship) tooth size has a greater role in developing dental crowding.