Seroprevalence of Toxoplasma gondii and associated risk factors in cats from Lima, Peru.

Toxoplasmosis is an important zoonotic disease worldwide caused by the intracellular parasite Toxoplasma gondii. Cats, being hosts, act as a good sentinel for this disease. Thus, the objective of this study was to determine the seroprevalence of T. gondii in cats by examining serum from seven districts of Metropolitan Lima, Peru. We collected and analyzed 303 cat serum samples, and the owners answered a questionnaire about age, gender, lifestyle (indoors only and outdoors access) and feeding (commercial and home food). The samples were tested using indirect hemagglutination (IHA) for detection of antibody IgM and IgG. Among the animals analyzed, we found 52 (17.2%, 95% CI: 13.1% - 21.9%) seropositive cats to T. gondii, of which one corresponded to acute infection (IgM) and 51 to chronic infections (IgG). In addition, the presence of anti-T. gondii antibodies was associated with feeding commercial food and living outdoors access. Our results concluded that T. gondii infections are common in cats with owners in Metropolitan Lima and will be useful to future epidemiological studies.

Prognostic Factors in De Novo Metastatic Renal Cell Carcinoma: A Report From the Latin American Renal Cancer Group.

PURPOSE: To assess the effect of clinical and pathological variables on cancer-specific and overall survival (OS) in de novo metastatic patients from a collaborative of primarily Latin American countries. PATIENTS AND METHODS: Of 4,060 patients with renal cell carcinoma diagnosed between 1990 and 2015, a total of 530 (14.5%) had metastasis at clinical presentation. Relationships between clinical and pathological parameters and treatment-related outcomes were analyzed by Cox regression and the log-rank method. RESULTS: Of 530 patients, 184 (90.6%) had died of renal cell carcinoma. The median OS of the entire cohort was 24 months. American Society of Anesthesiology classification 3-4 (hazard ratio [HR]: 1.64), perirenal fat invasion (HR: 2.02), and ≥ 2 metastatic organ sites (HR: 2.19) were independent prognostic factors for 5-year OS in multivariable analyses. We created a risk group stratification with these variables: no adverse risk factors (favorable group), median OS not reached; one adverse factor (intermediate group), median OS 33 months (HR: 2.04); and two or three adverse factors (poor risk group), median OS 14 months (HR: 3.58). CONCLUSION: Our study defines novel prognostic factors that are relevant to a Latin American cohort. With external validation, these easily discerned clinical variables can be used to offer prognostic information across low- and middle-income countries.

Análisis de costos en la cirugía de catarata por facoemulsificación bilateral simultánea versus facoemulsificación bilateral secuencial / Cost analysis of simultaneous bilateral phacoemulsification cataract surgery versus sequential bilateral phacoemulsification

RESUMEN Objetivo: Evaluar el costo en la cirugía de catarata por facoemulsificación bilateral simultánea vs. facoemulsificación bilateral secuencial, con implante de lente intraocular. Métodos: Se realizó un estudio analítico de evaluación económica en 762 pacientes mayores de 50 años, intervenidos de catarata con la cirugía de facoemulsificación bilateral simultánea (grupo I), y 762 pacientes operados de catarata con la cirugía de facoemulsificación bilateral secuencial (grupo II), en el Instituto Cubano de Oftalmología Ramón Pando Ferrer, del año 2014 al 2019. Se evaluaron los costos en recursos humanos, materiales e indirectos, así como los costos totales de ambos grupos después de la intervención quirúrgica, partiendo de la demostración científica de que ambos procedimientos son igualmente eficaces. Resultados: Predominó la edad de 61 a 80 años y el sexo femenino (75 por ciento) en ambos grupos. Los costos unitarios relacionados con los recursos humanos disminuyeron en 1,69 pesos para el grupo I, mientras que los costos totales y unitarios en relación con los recursos materiales fueron similares en ambos grupos. Los costos unitarios indirectos disminuyeron en 3,63 pesos en el grupo I. Finalmente, el costo unitario total para el grupo de cirugía bilateral simultánea resultó 6,19 pesos menor que el de cirugía bilateral secuencial. Conclusiones: La cirugía de catarata por facoemulsificación bilateral simultánea tiene menores costos que la facoemulsificación bilateral secuencial(AU)

ABSTRACT Objective: Evaluate the cost of simultaneous bilateral phacoemulsification cataract surgery vs. sequential bilateral phacoemulsification with intraocular lens implantation. Methods: An analytic economic evaluation was conducted of 762 patients aged over 50 years undergoing simultaneous bilateral phacoemulsification cataract surgery and 762 patients undergoing sequential bilateral phacoemulsification cataract surgery at Ramón Pando Ferrer Cuban Institute of Ophthalmology in the period 2014-2019. Evaluation was performed of costs incurred on human resources and materials, indirect costs, and total costs for the two groups after surgery, starting from the scientific certainty that both procedures are equally effective. Results: The 61-80 years age group and female sex (75 percent) prevailed in both groups. Human resources unit costs decreased 1.69 CUP in group I, whereas material resources total and unit costs were similar in both groups. Indirect unit costs decreased 3.63 CUP in group I. Total unit cost was 6.19 CUP lower in the simultaneous bilateral surgery group than in the sequential bilateral surgery group. Conclusions: Simultaneous bilateral phacoemulsification cataract surgery is more cost-effective than sequential bilateral phacoemulsification(AU)

Evaluación de la efectividad en la cirugía de catarata por facoemulsificación bilateral simultánea versus facoemulsificación bilateral secuencial / Evaluation of the effectiveness in the simultaneous bilateral phacoemulsification cataract surgery versus sequential bilateral phacoemulsification

RESUMEN: Objetivo: Comparar la efectividad y la seguridad de la cirugía de cataratas en pacientes operados por facoemulsificación bilateral simultánea vs. facoemulsificación bilateral secuencial con implante de lente intraocular. Métodos: Se realizó un estudio longitudinal en 762 pacientes mayores de 50 años, divididos en dos grupos. Se evaluó la variación de la función visual y la calidad de vida mediante la aplicación del cuestionario para analizar la función visual antes de la intervención quirúrgica y luego de 3 meses. Para evaluar la seguridad se midió la incidencia de complicaciones trans y posquirúrgicas asociadas a la intervención. Como medida de efectividad clínica se utilizó la mejor agudeza visual corregida y sin corregir. La efectividad autopercibida por los pacientes se evaluó mediante el cuestionario específico VF-14 de calidad de vida relacionada con la salud. Resultados: Predominó la edad de 61 a 80 años y el sexo femenino (75 por ciento) en ambos grupos. Las comparaciones de las variables refractivas y la calidad de vida según el índice de función visual mostraron diferencias significativas entre el preoperatorio y el posoperatorio, tanto para el grupo I como para el grupo II (p< 0,001), con evidentes resultados favorables posoperatorios en ambos. Conclusión: La cirugía de catarata por facoemulsificación bilateral simultánea es efectiva, por las evidencias de mejoría en la agudeza visual, la funcionabilidad y la calidad de vida de los pacientes, lo que les permite reincorporarse tempranamente a sus actividades sociales y laborales(AU)

ABSTRACT Objective: To compare the effectiveness and safety of cataract surgery in patients operated on by simultaneous bilateral phacoemulsification cataract surgery versus sequential bilateral phacoemulsification with intraocular lens implantation. Methods: A longitudinal study was conducted of 762 patients aged over 50 years, divided into two groups. We evaluated the variation of visual function and quality of life through the application of the questionnaire to analyze visual function before surgery and after 3 months. To evaluate the safety, the incidence of postsurgical complications trans and associated with the intervention was measured. As a measure of clinical effectiveness we used the best corrected and uncorrected visual acuity. The perceived effectiveness by patients was assessed by the specific questionnaire VF-14 of health-related quality of life. Results: The 61-80 years age group and female sex (75 percent) prevailed in both groups. Comparisons of refractive variables and quality of life, according to the VF-14 visual function index, showed significant differences between preoperative and postoperative process, both for group I and group II (p< 0,001), with evident favorable postoperative results in both groups. Conclusion: Cataract surgery for simultaneous bilateral phacoemulsification is effective, due to the evidence of improvement in visual acuity, functionality and quality of life of patients, which Allows them to return early to their social activities and labor(AU)

The extent of root resorption and tooth movement following the application of ascending and descending magnetic forces: a prospective split mouth, microcomputed-tomography study.

OBJECTIVE: Various factors have been examined in the literature in an attempt to reduce the incidence and severity of root resorption. The purpose of the present investigation is to test the null hypothesis that there is no difference in relation to force level using gradually increasing (ascending) and decreasing (descending) orthodontic force generated by magnets on the severity of Orthodontically Induced Inflammatory Iatrogenic Root Resorption (OIIRR) and amount of tooth movement. METHODS: Twenty maxillary first premolars from 10 patients were subjected to ascending (25-225 g, magnets in attraction) and descending (225 to 25 g, magnets in repulsion) buccal forces using a split mouth design over an 8-week period. Polyvinyl siloxane impressions were taken at week 0, 4, and 8 to record the tooth movement. After 8 weeks, the teeth were extracted, scanned, with micro-CT in 16.9 µm resolution, and the root resorption craters were localized circumferentially and quantified at each level of the root. RESULTS: The total volume of OIIRR with ascending force was 1.20 mm3, and with descending force was 1.25 mm3, and there was no statistically significant difference between them. OIIRR on the palatal surface (0.012 mm3) was significantly less than on the buccal surface (0.057 mm3) and than on the mesial surface (0.035 mm3). There is no statistically significant difference in the degree of OIIRR between different level of the root (cervical, middle, and apical) at different surfaces. Moreover, the amount of tooth movement, at 0-, 4-, and 8-week interval, secondary to an ascending and descending force application was not statistically significant. CONCLUSIONS: There is no short-term (8 weeks) statistically significant difference between orthodontic ascending and descending forces, from 25 to 225 g and from 225 to 25 g, respectively, in term of severity and location of OIIRR as well as the amount of tooth movement. The buccal surface of the root showed highest degree of OIIRR compared to other root's surfaces.

The short-term skeleto-dental effects of a new spring for the intrusion of maxillary posterior teeth in open bite patients.

BACKGROUND: The technology surrounding temporary skeletal anchorage devices has improved in leaps and bounds. However, no specific auxiliary exists for the intrusion of molars in conjunction with these devices and currently clinicians are forced to make do with available force delivery materials. A new intrusion auxiliary, the Sydney Intrusion Spring (SIS), was designed to facilitate intrusion without frequent need for reactivation or tissue irritation. METHODS: The subjects consisted of 16 adolescent patients (12 females and 4 males) with an average age of 13.1 years (range 12.2 to 14.3 years). All patients were in the permanent dentition with an anterior open bite of ≥2 mm. Four self-drilling miniscrews were placed into the posterior maxillary buccal alveolar bone. The intrusion appliance consisted of a bonded acrylic appliance and the SIS, activated to produce an initial intrusive force of 500 g. Cone beam computed tomograms were taken after miniscrew placement and at the end of active intrusion. Rendered lateral cephalograms were produced and measurements were taken and compared. RESULTS: All study objectives were achieved in 4.91 months (range 2.5 to 7.75 months). The mean molar intrusion was 2.9±0.8 mm (P<.001), resulting in over bite increase of 3.0±1.5 mm (P<.001). The intrusion led to a 2.6°±1.3° (P<.001) clockwise occlusal plane rotation and a 1.2°±1.3° (P<.01) counter-clockwise rotation of the mandible. Dental measurements showed a significant uprighting and elongation of the incisors. There was no significant extrusion of the lower molars. CONCLUSION: The SIS is an effective appliance for the intrusion of maxillary posterior teeth, in conjunction with miniscrews.

Open bite as a risk factor for orthodontic root resorption.

The purpose of the present study was to clarify the prevalence and degree of root resorption induced by orthodontic treatment in patients with and without open bite. One hundred and eleven patients treated with multibracket appliances were retrospectively selected from the patients and divided into non-open bite (NOB) and open bite (OB) groups. The severity of root resorption and the root shape were classified into five groups on periapical radiographs before and after treatment. Moreover, only in the OB group, all teeth were sub-divided into functional and hypofunctional ones that are occluding and non-occluding. As the results of multiple linear regression analysis of patient characteristics and clinical variables with the number of overall root resorption, the independent variables that were found to contribute significantly to root resorption were bite and abnormal root shape. The prevalences of root resorption evaluated in the number of patients were significantly higher in OB group than in NOB group, and those in the number of teeth were significantly higher in OB group than in NOB group, in particular anterior and premolar teeth. The prevalence of resorbed teeth with abnormal root shapes was also significantly higher in OB group than in NOB group. On the other hand, in OB group, the prevalences of root resorption and teeth with abnormal root shape were significantly greater in hypofunctional teeth than in normal functional teeth. There are more teeth with root resorption and abnormal root shape in open bite cases than in normal bite cases, and more teeth with abnormal root shapes and root resorption in hypofunctional teeth than in functional teeth.

Effect of fluoride on root resorption following heavy and light orthodontic force application for 4 weeks and 12 weeks of retention.

OBJECTIVE: To evaluate the null hypothesis that fluoride intake via drinking water has no effect on orthodontic root resorption in humans after orthodontic force application for 4 weeks and 12 weeks of retention. MATERIALS AND METHODS: Forty-eight patients who required maxillary premolar extractions as part of their orthodontic treatment were selected from two cities in Turkey. These cities had a high and low fluoride concentration in public water of ≥2 pm and ≤0.05 pm, respectively. The patients were randomly separated into four groups of 12 each: group 1HH, high fluoride (≥2 ppm) and heavy force (225 g); group 2LH, low fluoride (≤0.05 ppm) and heavy force; group 3HL, high fluoride and light force (25 g); and group 4LL, low fluoride and light force. Light or heavy buccal tipping force was applied on the upper first premolars for 28 days. At day 28, the left premolars were extracted (positive control side); the right premolars (experimental side) were extracted after 12 weeks of retention. The samples were analyzed with microcomputed tomography. RESULTS: On the positive control side, under heavy force application, the high fluoride groups exhibited less root resorption (P  =  .015). On the experimental side, it was found that fluoride reduced the total volume of root resorption craters; however, this effect was not statistically significant (P  =  .237). Moreover, the results revealed that under heavy force application experimental teeth exhibited more root resorption than positive control groups. CONCLUSION: The null hypothesis could not be rejected. High fluoride intake from public water did not have a beneficial effect on the severity of root resorption after a 4-week orthodontic force application and 12 weeks of passive retention.

Effects of long-term occlusal hypofunction and its recovery on the morphogenesis of molar roots and the periodontium in rats.

OBJECTIVES: To investigate the effects of long-term, artificially created, hypofunctional occlusion and its recovery on the morphology of rat molar roots. MATERIAL AND METHODS: Eighteen 5-week-old Wistar-strain male rats were randomly divided according to their periodontal conditions into normal, hypofunctional, and recovery groups (n = 6 in each). In the experimental hypofunctional and recovery groups, a bite-raising appliance was set to produce hypofunction at the molar region. All groups were analyzed at 16 weeks of age using three-dimensional micro-computed tomography. Root length, width, and area as well as the thickness and the area of the periodontal ligament (PDL) space of the maxillary first molar were calculated. RESULTS: Roots were longer and narrower in the hypofunctional group than in the control group. The mesial root in particular showed a dramatic change. Root area also decreased significantly in the hypofunctional group compared to the other groups. Moreover, the PDL thickness and area decreased significantly in the hypofunctional group compared to the control group, but increased in the recovery group compared to the hypofunctional group. CONCLUSIONS: These findings suggest that root size and PDL structure may be reduced due to disuse atrophy resulting from a defect in occlusal function, but may be recovered following a gain of occlusal stimuli.

Orthodontic tooth movement and root resorption in ovariectomized rats treated by systemic administration of zoledronic acid.

INTRODUCTION: The effect of zoledronic acid, a potent and novel bisphosphonate, on tooth movement and orthodontically induced root resorption in osteoporotic animals systemically treated with zoledronic acid as similarly used in postmenopausal patients has not been elucidated. Therefore, this study was undertaken. METHODS: Fifteen 10-week-old female Wistar rats were divided into 3 groups: ovariectomy, ovariectomy + zoledronic acid, and control. Only the ovariectomy and ovariectomy + zoledronic acid groups underwent ovariectomies. Two weeks after the ovariectomy, zoledronic acid was administered only to the ovariectomy + zoledronic acid group. Four weeks after the ovariectomy, 25-g nickel-titanium closed-coil springs were applied to observe tooth movement and orthodontically induced root resorption. RESULTS: There were significant differences in the amounts of tooth movement and orthodontically induced root resorption between the ovariectomy and the control groups, and also between the ovariectomy and the ovariectomy + zoledronic acid groups. There was no statistically significant difference in tooth movement and orthodontically induced root resorption between the ovariectomy + zoledronic acid and the control groups. Zoledronic acid inhibited significantly more tooth movement and significantly reduced the severity of orthodontically induced root resorption in the ovariectomized rats. The ovariectomy + zoledronic acid group showed almost the same results as did the control group in both tooth movement and orthodontically induced root resorption. CONCLUSIONS: Zoledronic acid inhibits excessive orthodontic tooth movement and also reduces the risk of severe orthodontically induced root resorption in ovariectomized rats.

Physical properties of root cementum: Part 22. Root resorption after the application of light and heavy extrusive orthodontic forces: a microcomputed tomography study.

INTRODUCTION: Extrusive tooth movement has been overlooked in the literature on root resorption. The aims of this study were to quantify the effects of light and heavy controlled extrusive forces on root resorption and to localize the sites of prevalence in premolars. METHODS: Ten patients (7 girls, 3 boys) who required bilateral maxillary first premolar extractions as part of their orthodontic treatment participated in this study. The total sample consisted of 20 maxillary first premolars. Light (25 g) or heavy (225 g) forces were applied to the right or left first premolar for 28 days. After the experimental period, the teeth were extracted without root damage and analyzed with microcomputed tomography. Each specimen was studied in 3 dimensions, and specially designed software was used to measure the volume of each crater. Wilcoxon signed rank tests were used for the statistical analysis. RESULTS: There was a significant difference in the total root resorption caused by light and heavy forces (P = 0.037). The discrepancy between the light and heavy groups was not significant for the cervical, middle, and apical regions separately. Only the distal surfaces were significantly different between the light and heavy forces (P = 0.008). CONCLUSIONS: Greater root resorption was observed after heavy extrusive forces when compared with light forces. The distal surfaces of the tooth root were significantly more affected than other root surfaces and might be influenced by root morphology and initial angulation of the tooth. There was no significant difference in the cervical, middle, and apical thirds in relation to root resorption after light or heavy extrusive forces.

Physical properties of root cementum: part 20. Effect of fluoride on orthodontically induced root resorption with light and heavy orthodontic forces for 4 weeks: a microcomputed tomography study.

INTRODUCTION: The major side effect of orthodontic treatment is orthodontically induced inflammatory root resorption. Fluoride was previously shown to reduce the volume of the root resorption craters in rats. However, the effect of fluoride on orthodontically induced inflammatory root resorption in humans has not yet been investigated. The aim of this study was to investigate the effect of high and low amounts of fluoride intake from birth on orthodontically induced inflammatory root resorption under light (25 g) and heavy (225 g) force applications. METHODS: Forty-eight patients who required maxillary premolar extractions as part of their orthodontic treatment were selected from 2 cities in Turkey with high and low fluoride concentrations in the public water of ≥ 2 and ≤ 0.05 ppm, respectively. The patients were randomly separated into 4 groups of 12 each: group 1, high fluoride intake and heavy force; group 2, low fluoride intake and heavy force; group 3, high fluoride intake and light force; and group 4, low fluoride intake and light force. Light or heavy buccal tipping orthodontic forces were applied on the maxillary first premolars for 28 days. At day 28, the teeth were extracted, and the samples were analyzed with microcomputed tomography. RESULTS: Fluoride reduced the volume of root resorption craters in all groups; however, this effect was significantly different with high force application (P = 0.015). It was also found that light forces caused less root resorption than heavy forces. There was no statistical difference in the amount of root resorption observed on root surfaces (buccal, lingual, mesial, and distal) in all groups. However, the middle third of the roots showed the least root resorption. With high fluoride intake and heavy force application, less root resorption was found in all root surfaces and root thirds. CONCLUSIONS: Fluoride may reduce the volume of root resorption craters. This effect is significant with heavy force applications (P <0.05). The cervical and apical thirds of the root showed significantly greater root resorption after the application of buccal tipping force for 4 weeks.

Tooth movement and root resorption; the effect of ovariectomy on orthodontic force application in rats.

OBJECTIVE: To quantify the amount of tooth movement and orthodontically induced root resorption (OIRR) in ovariectomized rats. MATERIALS AND METHODS: Five 10-week-old female Wistar rats undergoing ovariectomy (OVX) were investigated as the experimental group, and the other five without ovariectomy served as the control group. Four weeks after ovariectomy, 25-g nickel-titanium closed-coil springs were applied mesially to the maxillary left first molars. Micro-computed tomography was taken at day 0, 1, 3, 7, 14, 21, and 28. At day 28, the molars were extracted. The surface area of root resorption craters, depth, and volume were measured using electron and laser scanning microscopes. RESULTS: Tooth movement gradually increased with time throughout 28 days. There was a significant difference in the amount of tooth movement between the control group and the OVX group. For OIRR, the OVX group showed wide and shallow root resorption craters scattered on the mesial root. The deep resorption craters were observed on the distal roots distributed in the cervical, middle, and apical thirds of the roots. Statistically significant differences were found between the control and the OVX groups in the depth and the volume of root resorption craters in the distal roots and the total volume of root resorption craters in all three roots. CONCLUSION: Ovariectomy affected not only tooth movement but also OIRR. Tooth movement in the OVX group was more rapid than the control group. Furthermore, the amount of OIRR in the OVX group was more severe than the control group.

Effects of fluoride intake on orthodontic tooth movement and orthodontically induced root resorption.

INTRODUCTION: Even though the beneficial effects of fluoride on enamel and root caries have been well documented, limited data are available concerning the effect of fluoride on orthodontically induced root resorption and tooth movement. Our objective was to investigate the effect of systemic fluoride administered from birth to 12 weeks on orthodontically induced root resorption and tooth movement in rat molars. METHODS: Fifty male Wistar rats were randomly divided into 5 groups. The negative control group received no sodium fluoride and had no tooth movement. The positive control group received no sodium fluoride but had tooth movement. Three experimental groups received sodium fluoride at 45 ppm from birth to 2, 4, and 12 weeks, respectively. At week 10, a 50-g nickel-titanium coil spring was applied to the maxillary left first molar for 2 weeks. The rats were killed at 12 weeks of age. Movement of the maxillary first molars was measured in relation to the maxillary second molar on digitized cephalometric radiographs. Mesial and distal roots were examined by using scanning electron and 3-dimensional laser microscopes. RESULTS: Fluoride reduced the depth, volume, and roughness of the resorption craters in the experimental groups. However, the area was similar to that in the positive control group. Regarding the duration of fluoride intake, the longer fluoride was administered via drinking water, the smaller the amount of tooth movement observed. CONCLUSIONS: Fluoride in drinking water from birth reduced the severity of orthodontically induced root resorption, but the amount of tooth movement was also decreased.

The effect of fluoride on orthodontic tooth movement in humans. A two- and three-dimensional evaluation.

AIMS: The aim of the present study was to determine whether high and low fluoride concentrations in drinking water affected the early stages of tooth movement when heavy and light orthodontic forces were applied for 4 weeks. A further aim was to compare and evaluate the resulting two-dimensional (2-D) and three-dimensional (3-D) orthodontic tooth movement. METHODS: The sample consisted of 96 maxillary upper first premolars from 48 patients who required premolar extractions as part of their orthodontic treatment. Patients were selected from two different cities in Turkey with low and high fluoride concentrations of 0.05 and 2 ppm, respectively. The patient sample was divided into four groups according to the magnitude of force applied to the first premolars and the concentration of fluoride in the public water supply; Group 1, High fluoride intake (> or = 2 ppm)-Heavy force (225 g); Group 2, Low fluoride intake (< or = 0.05 ppm)-Heavy force; Group 3, High fluoride intake-Light force (25 g); and Group 4, Low fluoride intake-Light force. A light or heavy buccal tipping orthodontic force was applied to the upper first premolars for 4 weeks. The first three palatal rugae were used for the superimposition of patient casts in a 2-D and 3-D evaluation of generated movements. RESULTS: It was found that heavy force application and fluoride intake increased the average rate of tooth movement. It was further shown that age was negatively correlated with tooth movement in the 2-D and 3-D measurements. CONCLUSIONS: The average rate of tooth movement was found to be greater in the heavy force and high fluoride intake group (Group 1HH). Age was negatively correlated with orthodontic tooth movement. Two- and three-dimensional methods were accurate for the assessment of tooth movement after four weeks of buccal tipping force application when the palatal rugae were used for superimposition.

Repair of root resorption 2 to 16 weeks after the application of continuous forces on maxillary first molars in rats: a 2- and 3-dimensional quantitative evaluation.

INTRODUCTION: Root resorption is a side effect of orthodontic treatment that occurs with the removal of hyalinized tissue. Studies have shown that a reparative process in the periodontium begins when the applied orthodontic force is discontinued or reduced below a certain level. However, quantitative 3-dimensional evaluation of root resorption repair has not been done. The aim of this study was to quantitatively assess the 2- and 3-dimensional changes of root resorption craters after 2 weeks of continuous mesially applied orthodontic forces of 50 g on rat molars and 2- to 16-week retention periods. METHODS: We used 60 male Wistar rats (10 weeks old). Nickel-titanium closed-coil springs were used to apply 50-g mesial forces for 2 weeks to move the maxillary left first molars. The rats were randomly allocated to 6 groups. Those in the zero-week retention group were killed after force application. In the remaining 5 groups, the interdental spaces between the maxillary first and second molars were filled with resin to retain the molars. The molars were extracted after periods of retention from 2 and 16 weeks. The maxillary right molars were used as the controls. Mesial and distal roots (distobuccal and distopalatal) were examined by using scanning electron and 3-dimensional scanning laser microscopes. The surface area, depth, volume, and roughness of the root resorption craters were measured. RESULTS: The area, depth, and volume of the craters decreased gradually and showed similar trends over the retention time, approaching a plateau at the 12th week. After 16 weeks of retention, the volumes of the resorption craters of the distobuccal and distopalatal roots reached recovery peaks of 69.5% and 66.7%, respectively. Small pits on the mesial roots showed recovery of 62.5% at the 12th week. The healing patterns in distal roots with severe resorption and mesial roots with shallow resorption had no significant differences. CONCLUSIONS: The resorption and repair processes during the early stages of retention are balanced, and most of the reparative process occurs after 4 weeks of passive retention after the application of orthodontic force. Frequent orthodontic reactivations should be avoided to allow recovery and repair of root surface damage.

Optimal loading conditions for controlled movement of anterior teeth in sliding mechanics.

OBJECTIVE: To determine optimal loading conditions such as height of retraction force on the power arm and its position on the archwire in sliding mechanics. MATERIALS AND METHODS: A 3D finite element method (FEM) was used to simulate en masse anterior teeth retraction in sliding mechanics. The degree of labiolingual tipping of the maxillary central incisor was calculated when the retraction force was applied to different heights of a power arm set mesial or distal to the canine. RESULTS: When the power arm was placed mesial to the canine, at the level of 0 mm (bracket slot level), uncontrolled lingual crown tipping of the incisor was observed and the anterior segment of the archwire was deformed downward. At a power arm height of 5.5 mm, bodily movement was produced and the archwire was less deformed. When the power arm height exceeded 5.5 mm, the anterior segment of the archwire was raised upward and lingual root tipping occurred. When the power arm was placed distal to the canine, lingual crown tipping was observed up to a level of 11.2 mm. CONCLUSIONS: Placement of the power arm of an archwire between the lateral incisor and canine enables orthodontists to maintain better control of the anterior teeth in sliding mechanics. Both the biomechanical principles associated with the tooth's center of resistance and the deformation of the archwire should be taken into consideration for predicting and planning orthodontic tooth movement.

Effect of celecoxib on emotional stress and pain-related behaviors evoked by experimental tooth movement in the rat.

OBJECTIVE: To test the efficacy of an animal model of pain and stress and evaluate the effects of celecoxib administered when orthodontic force is applied. MATERIALS AND METHODS: A 20-g reciprocal force was applied via an orthodontic appliance to the maxillary left first and second molars of 7-week-old male Sprague-Dawley rats. Rat behavior was evaluated at 5, 24, and 48 hours after the appliance was set. Behavior was assessed in a test field by the number of lines crossed in the first 30 seconds and 5 minutes following force application; number of lines crossed to the center; rearing time; and facial grooming time. Experimental group 1 received intraperitoneal administration of 30 mg/kg celecoxib before every behavioral test. Experimental group 2 received 90 mg/kg before the first behavioral test, and physiologic saline was administered before the remaining behavioral tests. Control groups received saline before every behavioral test and were given passive (passive control group) and active (active control group) appliances, respectively. RESULTS: Parameters related to pain increased in the active controls, whereas the parameters in the experimental groups decreased to the level seen in the passive controls. Statistically significant differences in pain-related behavior between control and experimental groups were found at 5 and 24 hours after placing the appliance. Stress-related behavior was significantly less in the experimental groups compared to the active control group during experimental periods. CONCLUSIONS: The administration of celecoxib relieves pain- and stress-related behavior evoked by orthodontic tooth movement in the rat. This model might be a useful tool for the evaluation of pain and stress.

An in vivo 3D micro-CT evaluation of tooth movement after the application of different force magnitudes in rat molar.

OBJECTIVE: To investigate the precise longitudinal change in the periodontal ligament (PDL) space width and three-dimensional tooth movement with continuous-force magnitudes in living rats. MATERIALS AND METHODS: Using nickel-titanium closed-coil springs for 28 days, 10-, 25-, 50-, and 100-g mesial force was applied to the maxillary left first molars. Micro-CT was taken in the same rat at 0, 1, 2, 3, 10, 14, and 28 days. The width of the PDL was measured in the pressure and tension sides from 0 to 3 days. Angular and linear measurements were used to evaluate molar position at day 0, 10, 14, and 28. The finite element model (FEM) was constructed to evaluate the initial stress distribution, molar displacement, and center of rotation of the molar. RESULTS: The initial evaluation of PDL width showed no statistical differences among different force magnitudes. Tooth movement was registered 1 hour after force application and gradually increased with time. From day 10, greater tooth movement was observed when 10 g of force was applied. The FEM showed that the center of rotation in the molar is located in the center of five roots at the apical third of the molar roots. CONCLUSION: The rat's molar movement mainly consists of mesial tipping, extrusion of distal roots, intrusion of mesial root, palatal inclination, and mesial rotation. Although the initial tooth movement after the application of different force magnitudes until day 3 was not remarkably different, 10 g of force produced more tooth movement compared with heavier forces at day 28.

Effects of steroidal and nonsteroidal drugs on tooth movement and root resorption in the rat molar.

OBJECTIVE: To test the hypothesis that the administration of aspirin, acetaminophen, meloxicam, celecoxib, and prednisolone have no effect on root resorption and tooth movement. MATERIALS AND METHODS: A mesial force of 50 g was applied to the left maxillary first molars of sixty 10-week-old male Wistar rats using nickel titanium closed coil springs attached to the cervical area of the incisors. The rats were randomly divided into 12 groups of 5 each. High and low doses of aspirin, acetaminophen, meloxicam, celecoxib, and prednisolone were administered via drinking water for 2 weeks. The experimental control group had tooth movement but received no drug. The negative control group received neither tooth movement nor drugs. The amount of tooth movement was measured on digitized lateral cephalometric radiographs. Rats were sacrificed after 2 weeks. Mesial and distal roots (distobuccal and distopalatal) were examined using scanning electron and three-dimensional (3D) scanning laser microscopes. The surface area, depth, volume, and roughness of the root resorption craters were measured. RESULTS: When compared with experimental control rats, only prednisolone- and high-dose celecoxib-treated groups showed significantly less root resorption and less tooth movement. Although low dose celecoxib-treated group significantly decreased the tooth movement, root resorption was similar to the control group. Furthermore, resorption craters showed a smoother surface in the prednisolone-treated rats. CONCLUSIONS: The hypothesis was rejected. Administration of prednisolone and high-dose celecoxib reduces root resorption and interferes with tooth movement in rats. Both drugs may interfere in the arachidonic acid cascade depending on dose thresholds.