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This study evaluated the effect of experimental solutions containing plant extracts on bacterial species and enamel caries prevention. Microcosm biofilm was produced from human saliva mixed with McBain saliva (0.2% sucrose) on bovine enamel for 5 days (3 days under anaerobiosis and 2 days under aerobiosis) at 37°C. From the 2nd day, the following treatments were applied (1 × 60 s/day): Vochysia tucanorum (10 mg/mL); Myrcia bella (5 mg/mL); Matricaria chamomilla (80 mg/mL); Malva sylvestris, fluoride, and xylitol (Malvatricin Plus®); 0.12% chlorhexidine (CHX, PerioGard®); and PBS (negative control). The medium pH was measured. Quantitative polymerase chain reaction was performed for the detection of Streptococcus mutans and Lactobacillus spp. Enamel demineralization was measured by spectral-domain optical coherence tomography. The data were compared by means of the Kruskal-Wallis/Dunn, two-way ANOVA/Bonferroni, and ANOVA/Tukey tests (p < 0.05). The pH decreased after sucrose exposure; only CHX reestablished pH >5.5 by the last day. CHX also eliminated Lactobacillusspp., but the other treatments did not differ significantly from PBS. Malvatricin Plus® and CHX eliminated S. mutans, but the other treatments did not differ from PBS. Similar results were seen concerning the reduction of lesion depth and reflectivity. The experimental natural-extract solutions were ineffective against cariogenic bacteria and in preventing the development of enamel caries.

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BACKGROUND: Masseter muscle function influences mandibular bone homeostasis. As previously reported, bone resorption markers increased in the mouse mandibular condyle two days after masseter paralysis induced with botulinum toxin type A (BoNTA), followed by local bone loss. OBJECTIVE: This study aimed to evaluate the bone quality of both the mandibular condyle and alveolar process in the mandible of adult mice during the early stage of a BoNTA-induced masseter muscle atrophy, using a combined 3D histomorphometrics and shape analysis approach. METHODS: Adult BALB/c mice were divided into an untreated control group and an experimental group; the latter received one single BoNTA injection in the right masseter (BoNTA-right) and saline in the left masseter (Saline-left). 3D bone microstructural changes in the mandibular condyle and alveolar process were determined with high-resolution microtomography. Additionally, landmark-based geometric morphometrics was implemented to assess external shape changes. RESULTS: After 2 weeks, masseter mass was significantly reduced (P-value <0.001). When compared to Saline-left and untreated condyles, BoNTA-right condyles showed significant bone loss (P-value <0.001) and shape changes. No significant bone loss was observed in the alveolar processes of any of the groups (P-value >0.05). CONCLUSION: Condyle bone quality deteriorates at an early stage of BoNTA-induced masseter muscle atrophy, and before the alveolar process is affected. Since the observed bone microstructural changes resemble those in human temporomandibular joint degenerative disorders, the clinical safety of BoNTA intervention in the masticatory apparatus remains to be clarified.

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Background: Mouse molar is a widely used model for teeth development. However, the effect of masticatory function on enamel and dentine in adult individuals remains poorly understood. As reported, the unilateral masseter hypofunction induced by botulinum toxin type A (BoNTA) resulted in mandibular bone damage and signs of unilateral chewing in adult mice. Objective: We aimed to assess the amount of enamel and dentine in the first molar (M1) during the unilateral masseter hypofunction in mice, using high-resolution X-ray microtomography (µCT) as threedimensional approach. Materials and methods: Mandibles of adult BALB/c mice, located either in a Control-group (without intervention) or a BoNTA-group, were ex-vivo scanned using µCT. Treated individuals received each one BoNTA intervention in the right masseter, and saline solution in the left masseter (intra-individual control). Enamel and dentine from M1 were segmented, and volume, thickness and mesial root length were quantified. Results: Enamel volume from treated side resulted unchanged after 2 weeks of unilateral masseter hypofunction. No differences for enamel volume were found between both sides of control individuals, and between these and samples from hypofunctional side in BoNTA-group. Enamel volume from saline-injected side was reduced when compared with experimental side (p<0,01). No differences in dentine volume, thickness of enamel and dentine, and mesial root length were found for any group. Conclusion: The amount of enamel in hypofunctional molars remains unaffected after unilateral BoNTA intervention in the masseter, but contralateral side showed reduced enamel volume. Therefore, increased functional wearing during unilateral chewing after BoNTA intervention should be considered.

Introducción: El molar de ratón es utilizado como modelo de estudio en el desarrollo dental. El efecto de la función masticatoriasobre el tejido dental en individuos adultos aún se comprende. En ratones adultos, la hipofunción unilateral del masetero inducida por toxina botulínica tipo A (BoNTA) resultó en daño óseo mandibular y signos de masticación unilateral. Objetivo: Evaluamos la cantidad de esmalte y dentina en el primer molar (M1) durante la hipofunción unilateral del músculo masetero en ratones mediante análisis con microtomografía (µCT). Materiales y métodos: Las mandíbulas de ratones BALB/c adultos, del grupo Control (sin intervención) o el grupo BoNTA, fueron escaneadas ex-vivo con µCT. Los individuos tratados se inyectaron con BoNTA en el masetero derecho y con solución salina en el masetero izquierdo (control intra-individuo). El volumen y grosor de esmalte y dentina del M1, y la longitud de la raíz mesial fueron medidos. Resultados: No hubo cambios en el volumen del esmalte del lado tratado con BoNTA y en ambos lados del grupo Control, 2 semanas post-intervención. El esmalte del lado control intra-individuo se redujo comparado con el lado experimental (p< 0,01). No hubo cambios en el volumen de dentina, el grosor de esmalte y dentina o en longitud de la raíz mesial de ambos grupos. Conclusión: La cantidad de esmalte en los molares hipofuncionales no se afecta después de la inyección unilateral de BoNTA en masetero, pero si se reduce en el lado contralateral. Por lo tanto, se debe considerar un desgaste dental asimétrico durante esta intervención.