INFLUENCE OF LOW-LEVEL LASER APPLICATION ON ROOT RESORPTION AND PULP ALTERATIONS DURING TOOTH MOVEMENT

http://dx.doi.org/10.5902/223658345042The purpose of this study was to determine the effects of low-level laser (LLL) irradiation on root resorption and dental pulp during experimental tooth movement. Five groups were delineated: a control group without orthodontic force or LLL application, 2 other controls in which orthodontic force was applied for 2 and 7 days respectively, and two experimental groups with orthodontic force and LLL application for 2 and 7 days respectively. To induce experimental tooth movement in rats, orthodontic force of 40 cN was applied to the left first molars. In irradiated groups, Ga-Al-As diode laser (830 nm) was applied on 3 areas around the experimental maxillary molar: mesial, buccal and palatal. Two microscopic analyses were performed with HE staining: a quantitative for root resorption and a qualitative for pulp tissue reactions. Quantitative analysis showed that root resorptions were evident on day 7 of tooth movement. The irradiated group presented twice the amount of root resorption than the orthodontic control group, but this difference was not verified statistically (P=0.073). The qualitative pulp evaluation showed no significant alterations when orthodontic force or LLL were applied. Root resorption was verified when LLL was applied and no undesired effects on pulp tissue were observed. KEY WORDS: laser therapy, low-level; tooth movement; root resorption; dental pul

Evaluation of two protocols for low-level laser application in patients submitted to orthodontic treatment

INTRODUCTION: Different low-level laser (LLL) irradiation protocols have been tested to accelerate orthodontic tooth movement (OTM). Nevertheless, divergent results have been obtained. It was suggested that the stimulatory action of low level laser irradiation occurs during the proliferation and differentiation stages of bone cellular precursors, but not during later stages. OBJECTIVE: The purpose of this study was to determine the effect of two protocols of LLL irradiation on experimental tooth movement: One with daily irradiations and another with irradiations during the early stages. METHODS: Thirty-six rats were divided into control groups (CG1, CG2, CG3) and irradiated groups (IrG1, IrG2, IrG3) according to the presence of: experimental tooth movement, laser irradiation, type of laser irradiation protocol and date of euthanasia (3th or 8th day of experiment). At the end of experimental periods, a quantitative evaluation of the amount of OTM was made and the reactions of the periodontium were analyzed by describing cellular and tissue reactions and by counting blood vessels. RESULTS: The amount of OTM revealed no significant differences between groups in the same experimental period (p < 0.05). Qualitative analysis revealed the strongest resorption activity in irradiated groups after seven days, especially when using the daily irradiation protocol. There was a higher number of blood vessels in irradiated animals than in animals without orthodontic devices and without laser irradiation (p < 0.05). CONCLUSION: Moreover, angiogenesis was verified in some of the irradiated groups. The irradiation protocols tested were not able to accelerate OTM and root resorption was observed while they were applied

Evaluation of palatal arches made from low-nickel stainless steel wire

Aim: To test the hypothesis that there is no difference between stainless steel wires and low-nickel stainless steel ones regarding their mechanical behavior. Force, resilience and elasticity modulus produced by Coffin, “W” arch, and Quad-helix appliances made of 0.032-inch and 0.036-inch wires were evaluated. Methods: Fifteen appliances of each type (Coffin, "W" arch, and Quad-helix) were made according to metal alloy and wire thickness. All arches (12 groups of 15 appliances each) were submitted to mechanical compression test by using an EMIC DL-10000 machine simulating activations of 5, 8, 10, and 12 mm. Analysis of variance with multiple comparisons and Tukey’s test were used (P < 0.05) for analyzing statistically force and resilience data. Results: The results showed that mechanical properties depended on shape of the appliance, diameter of the wire, amount of activation, and metal alloy. Conclusions: Appliances made from lownickel stainless steel alloy had higher release of force, resilience and elasticity modulus compared to those made of stainless steel alloy

Is miniscrew primary stability influenced by bone density?

Primary stability is absence of mobility in the bone bed after mini-implant placement and depends on bone quality among other factors. Bone quality is a subjective term frequently considered as bone density. The aim of this preliminary study was to evaluate bone density in two bovine pelvic regions and verify the primary stability of miniscrews inserted into them. Forty bone blocks were extracted from bovine pelvic bones, 20 from iliac and 20 from pubic bone, all of them containing cortical bone about 1 mm thick. Half of the sections extracted from each bone were designated for histological evaluation of bone density (trabecular bone area - TBA) and the other half for bone mineral density (BMD) evaluation by means of central dual-energy X-ray absorptiometry (DEXA). Then, twenty self-drilling miniscrews (INPÒ, São Paulo, Brazil) 1.4 mm in diameter and 6 mm long were inserted into the bone blocks used for BMD evaluation. Peak implant insertion torque (IT) and pull-out strength (PS) were used for primary stability evaluation. It was found that iliac and pubic bones present different bone densities, iliac bone being less dense considering BMD and TBA values (P > 0.05). However, the miniscrew primary stability was not different when varying the bone type (P < 0.05). IT and PS were not influenced by these differences in bone density when cortical thickness was about 1 mm thick

Evaluation of palatal arches made from low-nickel stainless steel wire

test the hypothesis that there is no difference between stainless steel wires and low-nickel stainless steel ones regarding their mechanical behavior. Force, resilience and elasticity modulus produced by Coffin, W arch, and Quad-helix appliances made of 0.032-inch and 0.036-inch wires were evaluated. Methods: Fifteen appliances of each type (Coffin, W arch, and Quad-helix) were made according to metal alloy and wire thickness. All arches (12 groups of 15 appliances each) were submitted to mechanical compression test by using an EMIC DL-10000 machine simulating activations of 5, 8, 10, and 12 mm. Analysis of variance with multiple comparisons and Tukeys test were used (P < 0.05) for analyzing statistically force and resilience data. Results: The results showed that mechanical properties depended on shape of the appliance, diameter of the wire, amount of activation, and metal alloy. Conclusions: Appliances made from lownickel stainless steel alloy had higher release of force, resilience and elasticity modulus compared to those made of stainless steel alloy

Cytotoxicity of orthodontic separating elastics

Separating elastics may be cytotoxic to the interdental gingival tissues. Both latex and non-latex separating elastics are widely used and both types should be biocompatible

Quantitative assessment of S. mutans and C. albicans in patients with Haas and Hyrax expanders

OBJECTIVE: To assess and compare the number of Streptococcus mutans and Candida albicans colonies in patients with Haas and Hyrax appliances before and after insertion. METHODS: The sample consisted of 84 patients requiring orthodontic treatment. For all patients a midpalatal suture expansion was indicated. Patients were randomly divided into Group HA, who used the Haas appliance (n = 42) and Group HY, who used the Hyrax appliance (n = 42). Initially and thirty days after appliance insertion all patients were submitted to saliva collections. The saliva was diluted followed by seeding in Mitis Salivarius and CHROMagar media, for growth of S. mutans and C. albicans respectively. RESULTS: Results showed statistically significant difference between groups HA and HY for Streptococcus mutans and Candida albicans (p <0.05). Haas appliance promoted greater S. mutans and C. albicans proliferation when compared to Hyrax appliance. CONCLUSION: The Haas appliance favored greater proliferation of S. mutans and C. albicans when compared with the Hyrax appliance. Insertion of the appliances resulted in greater buildup of microorganisms