Corrosion-induced changes in surface properties and roughness of orthodontic wires.

INTRODUCTION: This study aimed to investigate the surface free energy and surface roughness (SR) of metallic alloys under the influence of acid solutions. METHODS: The experiment involved the use of 270 rectangular wire samples measuring 0.019 × 0.025-in. These samples were sourced from 3 different commercial brands: Dentsply GAC, American Orthodontics, and Orthoclassic. This in vitro study categorized the samples into 3 groups based on the solutions employed: deionized water, citric acid, and phosphoric acid. Each group consisted of 90 samples, with 30 samples representing each type of alloy-stainless steel, nickel-titanium, and titanium molybdenum alloy (TMA). The wire segments were immersed in their respective solutions for 72 hours at a controlled temperature of 37°C, with continuous orbital agitation at 130 rpm. After the immersion period, the study analyzed both surface free energy and SR. The mean values obtained were subjected to an analysis of variance at a significance level of 5%. RESULTS: All alloys displayed hydrophobic behavior, as indicated by interaction free energy values <0. In acidic environments (phosphoric acid and citric acid), significant differences were observed among different brands and alloys, affecting surface energy and interaction free energy. Variations in SR among metallic alloys included steel with the lowest SR variations, followed by nickel-titanium and TMA. Notably, the TMA alloy stood out with significantly higher surface energy compared with that of the other alloys (P <0.001). CONCLUSIONS: In this study, all examined alloys demonstrated a hydrophobic nature, suggesting a limited attraction to water. Notably, TMA exhibited the least hydrophobic behavior among the alloys studied. However, when exposed to citric acid, TMA displayed the most substantial alterations in its surface properties. These results underscored the significance of accounting for the distinctive properties of each alloy and their responses to diverse challenges, such as exposure to acidic solutions, during the selection of orthodontic wires for orthodontics treatment.

Validation of a new experimental model of extrusive luxation on maxillary molars of rats: a histological study.

BACKGROUND/AIM: The aim of this study was to test and validate a new model of extrusive luxation trauma on maxillary first molars of rats. MATERIAL AND METHODS: Forty adult male rats (Rattus norvegicus albinus, Wistar; weight = 230-250 g), 45 days old, were divided into eight groups (n = 5): control groups, in which animals were not subjected to any procedure and waited 1 day (GC1D) or 3 days (GC3D) for euthanasia, and experimental groups, in which animals were subjected to forces of 1100cN, 1300cN, or 1500cN and waited 1 or 3 days for euthanasia (GT1100/1D, GT1100/3D, GT1300/1D, GT1300/3D, GT1500/1D, GT1500/3D). In animals of the experimental groups, trauma was produced by an extrusive force in maxillary first right molars. Four-micrometer serial cuts stained with hematoxylin and eosin (HE) were made. Descriptive microscopic analysis of first upper right molar and semi-quantitative analysis (scores 1 to 4) of intensity of acute and chronic inflammation and vascular changes in the periodontal ligament and active and inactive external root resorption were conducted. The distribution of scores in the groups was compared using the Freeman-Halton extension of Fisher's exact test. The significance level was 5%. RESULTS: It was observed that vascular disorders (bleeding) on the periodontal ligament became more evident with increasing extrusive force. CONCLUSIONS: This new method was capable of generating histological changes, proving its secure application in this research area. The 1500cN force produced more damage on the periodontal ligament. CLINICAL RELEVANCE: The validation of a new experimental method can produce more reliable evidence in further research.

Cone-beam tomography assessment of the condylar position in asymptomatic and symptomatic young individuals.

STATEMENT OF PROBLEM: Studies of the condyle-mandibular fossa relationship are common, although the role of this relationship in the development of a temporomandibular disorder remains controversial. PURPOSE: The purpose of this study was to quantitatively evaluate the condyle-mandibular fossa relationship in young individuals with intact dentitions and compare it to that between individuals with and without symptoms of temporomandibular disorder. MATERIAL AND METHODS: Volunteers were classified as asymptomatic (n=20) or symptomatic (n=20) according to research diagnostic criteria for temporomandibular disorders. Each participant underwent 2 cone beam-computed tomography scans of the middle and lower third of the face: 1 scan of the maximum intercuspation position and 1 of the centric relationship position. The distance between the condyle and mandibular fossa was measured on frontal and lateral images of the temporomandibular joint. The condylar position was compared across groups (asymptomatic, symptomatic) by using the Mann-Whitney U test (α=.05). Within each group, the condylar position was compared across maximum intercuspation and centric relationship positions by using the Mann-Whitney U test (α=.05). RESULTS: No statistically significant differences were found in condylar positions between centric relationships and maximum intercuspation in either asymptomatic or symptomatic young adults, and no significant differences were found between asymptomatic and symptomatic young adults. CONCLUSIONS: The condyle-mandibular fossa relationships of these young adults were similar in the centric relationships and maximum intercuspation positions when evaluated by computed tomography. The presence or absence of temporomandibular disorder was not correlated with the condyle position in the temporomandibular joint.

Effect of alendronate sodium on tooth movement in ovariectomized rats.

OBJECTIVES: The aim of the present study was to evaluate the effect of two different dosages of alendronate on induced orthodontic movement in an experimental model involving rats with osteoporosis following ovariectomy. DESIGN: Female Wistar rats (Rattus norvegicus) eight weeks of age were divided into four groups (n=12/group): ovariectomized (OVX group); ovariectomized and treated with alendronate sodium at 1mg/kg (Group OVX+ALN1); ovariectomized and treated with alendronate sodium at 2mg/kg (Group OVX+ALN2); and sham operated (control). Three months after ovariectomy, the maxillary right first molar was submitted to movement for five and seven days. After the death of the animals, the maxilla were removed and processed for microscopic evaluation. The maxillary left first molar (without movement) was used for comparison purposes in all groups. The samples were processed for the quantification of alveolar bone and tooth movement. RESULTS: Intragroup comparisons showed significant movement after five and seven days (p<0.05) for all groups. Comparison among groups revealed greater tooth movement in the OVX group (p<0.05), on day 7. CONCLUSIONS: Both alendronate sodium doses similarly decreased tooth movement in ovariectomized rats (p>0.05). Movement in ovariectomized+alendronate groups were also smaller than non-ovariectomized rats, however without statistical difference.

Microscopic evaluation of induced tooth movement after subluxation trauma: an experimental study in rats.

OBJECTIVE: The objective of this study was to assess the histological alterations that occurred in the periodontal area of rat molars submitted to induced tooth movement (ITM) right after an intentional trauma (subluxation). METHODS: Forty adult male Wistar rats (Rattus norvegicus albinus) were selected. The animals were divided into eight groups (n=5), according to the combination of variables: Group 1--control (neither trauma nor ITM); Group 2--ITM; Groups 3, 4, 5 and 6--dentoalveolar trauma groups corresponding, respectively, to 1, 3, 8 and 10 days after trauma; Groups 7 and 8 - the animals' molars were subjected to a 900 cN impact and, one and three days after the trauma event, tooth movement was induced. The rats' maxillary first molars were mesially moved during seven days with a closed coil (50 cN). After the experimental period of each group, the animals were sacrificed by anesthetic overdose and the right maxillas were removed and processed for histological analysis under light microscopy. RESULTS: In the animals of group 3, 4, 5 and 6, the histological alterations were not very significant. Consequently, the effect of induced tooth movement right after a subluxation event (groups 7 and 8) was very similar to those described for Group 2. CONCLUSIONS: There was no difference in the quality of periodontal repair when ITM was applied to teeth that had suffered a subluxation trauma.

Induction of ankylosis in the incisor for orthodontic tooth movement in rats.

BACKGROUND/AIM: The present research evaluated the induction of ankylosis and the eruption rate in rat incisors, with the aim of achieving stable anchorage for orthodontic tooth movement (OTM) of the molars. MATERIAL AND METHODS: Fifteen male Wistar rats were used. In the Experimental group, the right superior incisor of each animal was extracted, denuded of the PDL and the dental papilla, and reimplanted. The Control group was the left superior incisors. The eruption rate was measured at 7, 10, 12, 14, and 16 days after replantation. NiTi closed springs with a 50cN release force were installed for additional 9 days, and the eruption rate was determined. Then, the rats were sacrificed, and ankylosis was examined by microscopic analysis. Differences with P < 0.01 were defined as statistically significant. RESULTS: The eruption rates were 0 and 0.39 mm day(-1) in the Experimental group and Control group, respectively. All incisors of the Experimental group showed ankylosis according to histological analysis. CONCLUSIONS: The methodology used to induce ankylosis in this study was effective for anchoring the incisors during the OTM of rat molars, eliminating the undesirable effects consequent to continuous eruption.

Storage media for avulsed teeth: a literature review.

Dental avulsion is the most severe type of traumatic tooth injuries because it causes damage to several structures and results in the complete displacement of the tooth from its socket in the alveolar bone. The ideal situation is to replant an exarticulated tooth immediately after avulsion because the extraoral time is a determinant factor for treatment success and for a good prognosis. However, it is not always possible. The success of replantation depends on a number of factors that may contribute to accelerate or minimize the occurrence of root resorption or ankylosis, among which is the type and characteristics of the medium used for temporary storage during the time elapsed between avulsion and replantation. Maintaining the tooth in an adequate wet medium that can preserve, as longer as possible, the vitality of the periodontal ligament cells that remain on root surface is the key to success of replantation. Recent research has led to the development of storage media that produce conditions that closely resemble the original socket environment, with adequate osmolality (cell pressure), pH, nutritional metabolites and glucose, and thus create the best possible conditions for storage. Although these storage media can now be purchased in the form of retail products, the most common scenario is that such a product will not be readily available at the moment of the accident This paper reviews the literature on the different storage media that have been investigated for avulsed teeth based on full-length papers retrieved from PubMed/Medline, Lilacs, BBO and SciELO electronic databases using the key words 'storage medium', 'transportation medium', 'avulsion', 'tooth avulsion', 'replantation', 'tooth replantation', 'milk' and 'propolis'. After application of inclusion and exclusion criteria, 39 papers were selected and critically reviewed with respect to the characteristics, efficacy and ease of access of the storage medium. The review of the literature showed that a wide array of types of wet storage media have been evaluated in laboratory studies and clinical reports, including cell and tissue culture solutions like Hank's Balanced Salt Solution (HBSS); medical/hospital products developed specifically for organ storage purposes, such as Viaspan® and Euro-Collins®; culture media, like Minimum Essential Medium (MEM); saline; natural products like water, saliva, bovine milk and its variations, propolis, green tea, Morus rubra (red mulberry), egg white and coconut water; rehydrating solutions, like Gatorade® and Ricetral, and even contact lens solutions. Based on the literature, it could be stated that, so far, apart from Based on the literature, it could be stated that, so far, apart from solutions designed specifically for storage and culture purposes, regular pasteurized whole milk is the most frequently recommended and with the best prognosis among other solutions that are likely to be available at the scene of an accident, such as water, saline or saliva. Its advantages include its high availability, ready accessibility, physiologically compatible pH and osmolality (fluid pressure) with the root-surface adhered PDL cells, presence of nutrients and growth factors. However, there is not yet a single solution that fulfills all requirements to be considered as the ideal medium for temporary storage of avulsed teeth, and research on this field should carry on.

Interceptive approach to treatment of impacted maxillary canines.

Impaction of maxillary canines can be prevented by early intervention in the mixed dentition phase after the correct diagnosis of malocclusion, reducing the complexity of the treatment. This article reports the case of a 10-year-old patient who possessed impacted maxillary canines and, after early extraction of primary canines, had reestablished favorable permanent successors' eruption axis. This 5-year radiographic follow-up study with panoramic radiography shows that this can be used in practice and that an effective control strategy ensures the accuracy in the inclination of the impacted canines. Treatment success is related to early diagnosis and strategic interceptive treatment choice.

Microscopic evaluation of induced tooth movement in traumatized teeth: an experimental study in rats.

The clinical management of orthodontic patients with dental trauma before or during the treatment is mainly founded on clinical experience, expert opinions, and individual case reports. It is proposed in the literature that teeth sustaining mild trauma with minor damage to the periodontium (e.g. subluxation) should be followed for a period of time before being subjected to orthodontic forces. A minimum period of 3 months has been proposed. In this study, we used an animal model to investigate whether shorter observation periods could be established in case of mild trauma. The periradicular region of rat molars was examined microscopically to determine the biological events of tooth movement started 15 and 30 days after intentional subluxation using an experimental method to induce dentoalveolar trauma. Thirty adult male Wistar rats were assigned to 6 groups (n = 5): Group 1 (control - no trauma/orthodontic movement); Group 2: the animals received an orthodontic device and were sacrificed after 7 days; Groups 3 and 4: dentoalveolar trauma (subluxation) was experimentally induced by the application of an axial force of 900 cN on the occlusal surface of the maxillary right first molar, and the animals were sacrificed after 22 and 37 days, respectively; and Groups 5 and 6: 15 and 30 days, respectively, after force application, an orthodontic device was installed and the rats were sacrificed 7 days later. In G5 and G6, the periodontal ligament and pulp tissue were rich in cellular elements and blood vessels, the alveolar bone was preserved, and the root surface presented only very small areas of surface resorption (cementum), maintaining the characteristics of normality. In conclusion, the microscopic alterations in the gingival and periodontal tissues in response to an experimentally induced mild dentoalveolar trauma simulating subluxation were not sufficient to contraindicate starting the orthodontic movement 15 and 30 days after trauma.

Perceptions of laypersons and orthodontists regarding the buccal corridor in long- and short-face individuals.

OBJECTIVE: To determine the perception of orthodontists and laypersons regarding the size of the dark spaces in the buccal corridors and how that affects smile esthetics in individuals with long and short faces. MATERIALS AND METHODS: Images of eight smiling individuals were modified to create five sizes of dark spaces in the buccal corridors (2%, 10%, 15%, 22%, and 28%) and were submitted to a group of laypersons and a group of orthodontists. RESULTS: Laypersons were more critical in their evaluation than orthodontists. Laypersons could not distinguish the gradation of dark spaces in the buccal corridor unless it was very plain. Orthodontists perceived this gradation beginning at 15%. Female evaluators were more critical than male evaluators in both groups. CONCLUSIONS: The presence or absence of dark spaces in the buccal corridors has little influence over smile esthetics. While this aspect must be considered in the orthodontic diagnosis, there is no justification for expanding the buccal corridor to eliminate dark spaces unless they are very evident.

Multidisciplinary treatment of a fractured root: a case report.

AIM: To describe the orthodontic, periodontal and prosthetic management of a case with a 3 mm root fracture below the crest of the alveolar bone. METHODS: The root was extruded and periodontal surgery carried out to improve aesthetics and dental function. CONCLUSION: A multidisciplinary approach to the management of dental root fractures is necessary for successful treatment.

Mesiodistal angulations of the mandibular canines, premolars and molars with or without the presence of third molars.

SUMMARY: The purpose of the present research was to compare the normal average values of mesiodistal axial angulation, with the mesiodistal axial angulation of canines, premolars and mandibular molars in individuals with and without the presence of the mandibular third molars. Panoramic radiographs of 19 male and 21 female Caucasians, with a mean age of 22.35 years, who had not undergone orthodontic treatment were studied. The subjects were divided into two groups: group I, 20 radiographs of subjects without, and group II, 20 radiographs of subjects with mandibular third molars. The mean values of the groups were compared using a Student's t-test. The results show that, in both groups, the mandibular premolars and molars had enhanced angulation in the mesial direction, when compared with a control group of 42 Caucasians ranging in age from 12 to 17 years with a 'normal' occlusion (P < 0.05), while the mesiodistal axial angulation of the mandibular canines was similar to the control group (P < 0.05). The two groups, when compared, exhibited similar angular values for the canines, premolars and mandibular molars (P < 0.05), indicating no influence of the third molars.

Histological evaluation of experimentally induced subluxation in rat molars and its implications on the management of orthodontic treatment.

The purpose of this study was to evaluate the histological alterations occurred in the periradicular region of rat molars after intentional subluxation using an experimental method to induce dentoalveolar trauma. Eighteen adult male Wistar rats (Rattus norvegicus albinus) were selected for the study. The dentoalveolar trauma was experimentally induced by the application of an occlusogingival force on the occlusal surface of the maxillary right first molar using a tensiometer secured on a fully articulated support with adjustable steel shafts. The animals were assigned to six groups (n = 3), according to the intensity of the force applied to induce trauma: Group I (GI, control) - no force application; Groups II-VI (GII-GVI) - the animals were subjected to 600, 700, 800, 900 and 1000 cN force, respectively. After experimental induction of trauma, the animals were sacrificed by anesthetic overdose and the right maxillas were removed and processed for histological analysis under light microscopy. In the animals of GII, GIII and GIV, the histological alterations were similar to those described for GI. GVI (1000 cN) presented the most severe alterations, with the occurrence of buccal bone plate fracture, alveolar fracture and root fracture, which are not present in mild traumatic injuries like subluxation. The 900 cN force (GV) was capable to produce clinical and histological alterations in the gingival and periodontal tissues compatible with those observed in subluxation.

Uprighting impacted mandibular second molars with orthodontic elastic separating rings.

A 16-year-old girl presented with complaints of recurrent spontaneous pain in the mandibular second molar region. Treatment favored use of a simple uprighting technique involving orthodontic elastic separating rings.

Analysis in vitro of direct bonding system with cyanoacrylate ester and orthodontic wires.

The aim of this study was to evaluate the tensile strength of orthodontic wires bonded onto the enamel with cyanoacrylate ester. To obtain the specimens, 120 human premolars (extracted for orthodontic or periodontal reasons) were included in acrylic blocks of rapid polymerization with three teeth each. Four groups were formed with ten specimens each. In the specimens, a dental splint model was made with cyanoacrylate ester and round stainless steel wire. In groups I, II and III, cyanoacrylate ester was used with round steel wires, with variation in diameter: 0.014 inches; 0.016 inches and 0.018 inches, respectively. In group IV, round steel wire 0.018 inches was used with photo polymerizing resin composite with previous acid etching. The adhesive force of the materials was measured in two points under the action of the tensiometer (ETM-USA). The number of loose wires was counted along with those that remained fixed according to the different levels of force applied because of the direction of the tensile force (vertical or horizontal) and the diameter of the wire used. The data obtained were first submitted to a descriptive analysis and then submitted to a statistical analysis (Friedman's Test and Dunn's Test of Multiple Comparison - Epi-info 3.2). Within the limitations of the experimental conditions presented, the cyanoacrylate ester or 'Super Bonder' maintained bonded to enamel and steel wires (0.016 and 0.018 inches) during the tensile strength tests under different levels of applied forces.