Effect of time and photoactivated face on bond strength of brackets and on degree of monomer conversion.

OBJECTIVE: To evaluate the effect of four different photoactivation protocols (according to "photoactivated faces" - mesial/distal, cervical/incisal or center - and "photoactivation time" - 6-3 s) of a high-power photo activator (Valo Cordless®-Ultradent) on the shear bond strength (SBS) between metal brackets and dental enamel and on the degree of conversion (DC) of an orthodontic resin. MATERIALS AND METHODS: 40 bovine incisor crowns were randomly assigned to 4 groups (n = 10). The brackets were bonded with Transbond XT® resin using 4 protocols according to the "photoactivation protocol" factor (which was subdivided into photoactivated faces and photoactivation time): V3C = 3 s + center; V6C = 6 s + center; V3M3D = 3 s on mesial + 3 s on distal; V3C3I = 3 s on cervical + 3 s on incisal. All the samples were stored for 4 months (water,37ºC) and then subjected to a SBS test (100KgF,1 mm/min). 40 resin discs were made to evaluate the monomer degree of conversion. Data from the SBS and DC were assessed by One-way ANOVA and Tukey's test (5%). Bond failures were analyzed according to the Adhesive Remnant Index (ARI) and evaluated by the Kruskal-Wallis test (5%). RESULTS: There was a statistically significant difference (p = 0.008) in the One-way ANOVA result for SBS values between all groups, but the protocols showed statistically similar results (p ≥ 0.05-Tukey's tests) concerning the photoactivated faces (V6C, V3M3D and V3C3I) and photoactivation time (V3C and V6C) factors individually. There was no statistically significant difference (p ≥ 0.05) in the One-way ANOVA result for DC values. CONCLUSION: The SBS and DC values will vary depending on the protocol applied. CLINICAL RELEVANCE: It is possible to maintain the bracket fixation quality with the use of a high-power LED photo activator associated with a shorter photoactivation time. However, it is assumed that not all types of protocols that might be applied will provide quality bonding, such as V3C, V3M3D and V3C3I, which may - depending on the SBS and DC values - affect the final treatment time, due to brackets debonding, or increase of possibility of damage to dental enamel during bracket removal. Clinical studies are suggested to confirm the hypotheses of this research.

Caffeine induces alveolar bone loss in rats submitted to orthodontic movement via activation of receptor activator of nuclear factor Ò¡B, receptor activator of nuclear factor Ò¡B ligand, and osteoprotegerin pathway.

INTRODUCTION: Caffeine is a widely consumed substance with several effects on bone metabolism. This study aimed to investigate the effect of caffeine on the bone tissue of rats submitted to orthodontic movement. METHODS: Twenty-five male Wistar rats underwent orthodontic movement (21 days) of the first permanent maxillary molars on the left side. The experimental group (caffeine; n = 13) and control group (n = 12) received caffeine and water, respectively, by gavage. Microcomputed tomography was performed to analyze orthodontic movement. Histologic analysis of the inflammatory infiltrate and osteoclast count by tartrate-resistant acid phosphatase were conducted. Maxilla tissue was evaluated for receptor activator of nuclear factor Ò¡B (RANK), RANK ligand (RANKL), and osteoprotegerin by immunohistochemistry. RESULTS: Caffeine exhibited a lower bone volume/tissue volume ratio (78.09% ± 5.83%) than the control (86.84% ± 4.89%; P <0.05). Inflammatory infiltrate was increased in the caffeine group compared with the control group (P <0.05). A higher number of tartrate-resistant acid phosphatase-positive cells was observed in the caffeine (9.67 ± 1.73) than in the control group (2.66 ± 0.76; P <0.01). Immunoexpression of RANK and RANKL in the caffeine group was greater than the control (P <0.05). CONCLUSIONS: The use of caffeine thermogenic induces alveolar bone loss in rats submitted to orthodontic movement via activation of RANK, RANKL, and osteoprotegerin signaling pathways.

Caffeine Effect on Bone Metabolism in Rats: a Systematic Review

Abstract Caffeine is a highly-consumed substance around the world and can be found in various food sources and certain medications. The present systematic review aimed to evaluate the effect of caffeine on bone metabolism in rats. A systematic review was conducted in the PubMed, Medline, Scopus, Cocharane, Embase, and Clinical Trials.gov databases, and the Guidelines for Preferential Reporting for Systematic Reviews and Meta-Analyzes (PRISMA) were followed. In vivo experimental studies that presented caffeine as the study object were included, and studies which did not evaluate the bone metabolism and/or evaluated the caffeine in association with other substances were excluded. The quality evaluation of the selected studies was carried out following the guidelines of the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE) and the Animal Research Reporting In Vivo Experiment (ARRIVE). Nine of the 472 initially identified articles met the inclusion criteria and were selected for qualitative evaluation. There was a variation between the included studies regarding the administered caffeine doses in each experimental group, as well as their frequency and duration of ingestion. Most studies show that caffeine can interfere with bone metabolism, be it in a negative way by accelerating bone loss and delaying bone repair, or in a beneficial way by activating osteogenesis and bone neoformation. There is a need for further studies to better understand the real effect of caffeine on bone metabolism.

Efeito da cafeína na movimentação ortodôntica e no comportamento de ratos: estudo experimental in vivo / Effect of caffeine on orthodontic movement and behavior in rats: in vivo experimental study

OBJETIVO: Verificar o efeito da cafeína na movimentação ortodôntica (MO) e no comportamento de ratos. MÉTODOS: Neste estudo experimental in vivo randomizado, foram utilizados 12 ratos machos saudáveis da linhagem Wistar (Rattus norvegicus albinus), 7-12 semanas, 200-300g. Esses animais foram submetidos à MO (mola fechada de NiTi (50cN) entre 1o molar e incisivos superiores/lado esquerdo) e administração diária de cafeína (3g/L) e água por gavagem durante 21 dias consecutivos. A amostra foi distribuída em dois grupos: a) controle (n = 7): submetidos à MO e água; b) experimental (n = 5): submetidos à MO e cafeína. A quantidade de MO foi verificada através de um compasso de ponta seca e régua milimetrada nos tempos inicial e final. O teste de campo aberto foi empregado na avaliação comportamental em quatro tempos: baseline (T0), após colocação das molas (T1), após 2a gavagem (T2), após 21 dias (T3). Em seguida, foram realizados testes estatísticos de Mann-Whitney (quantidade de MO) e o teste de Friedman/pós teste de Wilcoxon (comportamento) em um nível de significância de 5%. RESULTADOS: A cafeína não interferiu na MO (p > 0,05). Quanto ao teste de campo aberto, valores estatisticamente significativos (p >0,05) foram identificados em diversos parâmetros. CONCLUSÃO: A cafeína não influenciou na quantidade de movimentação ortodôntica macroscópica, apesar de exibir efeito ansiogênico no comportamento de ratos (AU).

OBJECTIVE: To verify the effect of caffeine on orthodontic movement (MO) and behavior of rats. METHODS: In this randomized in vivo experimental study, 12 healthy male Wistar rats (Rattus norvegicus albinus), 7-12 weeks, 200-300g were used. These animals were submitted to OM (closed NiTi spring (50cN) between 1st molar and upper incisors / left side) and daily administration of caffeine (3g / L) and water by gavage for 21 consecutive days. The sample was divided into two groups: a) control (n = 7): submitted to OM and water; b) experimental (n = 5): submitted to OM and caffeine. The amount of OM was verified by a dry point compass and millimeter ruler at the beginning and end times. The open field test was used in the four-stage behavioral assessment: baseline (T0), after spring placement (T1), after 2nd gavage (T2), after 21 days (T3). Then, Mann-Whitney statistical tests (amount of OM) and Friedman test / Wilcoxon test (behavior) were performed at a significance level of 5%. RESULTS: Caffeine did not interfere with OM (p> 0.05). Regarding the open field test, statistically significant values (p> 0.05) were identified in several parameters. CONCLUSION: Caffeine did not influence the amount of macroscopic orthodontic movement, despite exhibiting anxiogenic effect on rat behavior (AU).