Zoledronate treatment exerts sex-independent effects on bone and dental physicochemical properties in mice jaw necrosis.

INTRODUCTION: Bisphosphonate (BF) therapy is strongly related to the occurrence of medication-related osteonecrosis of the jaw (ONJ). However, no previous study has evaluated if there are sex-related differences on the ONJ establishment together with bone biomechanical alterations, and if they could have a synergy with the ZA treatment. MATERIALS AND METHODS: This study aimed to analyze the physicochemical properties of mineralized tissues in a zoledronate (ZA)-related osteonecrosis mouse model, by a 2 × 2-factorial design, considering sex (female/male) and treatment (ZA/Saline) factors (n = 8/group). After three ZA (1.0 mg/kg) or saline administrations (days 0, 7, 14), the lower left second molar was extracted (day 42). Further ZA administration (day 49) and euthanasia (day 70) were conducted. After confirmation of ZA-induced jaw necrosis (histologic and microtomographic analysis), spectroscopic and mechanical parameters were assessed. RESULTS: ZA-treated groups presented lower bone density due to impaired healing of tooth extraction socket. Sex-related alterations were also observed, with lower bone density in females. Regarding biomechanical parameters, sex and treatment exerted independent influences. ZA, although decreasing flexural modulus and yield stress, increases stiffness mainly due to a higher bone volume. Females show less resistance to higher loads compared to males (considering dimension-independent parameters). Additionally, ZA increases crystallinity in bone and dental structure (p < 0.05). In summary, although strongly related to osteonecrosis occurrence, ZA modifies bone and dental mineral matrix, improving bone mechanical properties. CONCLUSION: Despite sex-dependent differences in bone biomechanics and density, osteonecrosis was established with no sex influence. No synergistic association between sex and treatment factors was observed in this study.

Root canal curvature influences uncontrolled removal of dentin and cleaning efficacy after ultrasonic activation.

This study evaluated the correlation between root canal curvature and the effects of ultrasonic irrigation in the following parameters: volume of uncontrolled dentin removal (UDRVol), maximum depth of dentin defects, removal of accumulated hard tissue debris (AHTD), and canal transportation in prepared curved root canals. Twenty-four human permanent mandibular molars were divided into two groups according to root canal curvature: moderate curvature (MC: mean 25°); and severe curvature (SC: mean 48°). The specimens were scanned using an X-ray microcomputed scanner (Skyscan 1172) before and after cleaning and shaping and after the final irrigation protocol with ultrasonic irrigation. There was a moderate correlation between the degree of root canal curvature and the volume of remaining AHTD (p<0.05) and between the degree of root canal curvature and maximum depth of defects due to uncontrolled removal of dentin (p<0.05). The teeth in the SC group had a greater maximum depth of defects on the dentin wall in the apical third than the teeth in the MC group (p <0.05). Both groups had a significant reduction of AHTD in all canal thirds, but the amount of remaining AHTD in the middle and apical thirds and the whole canal was significantly greater in the SC than in the MC group (p <0.05). Canal transportation was not influenced by the canal curvature in all thirds (p >0.05). This study concluded that root canal curvature affects significantly the uncontrolled removal of dentin and remaining AHTD volume after the final irrigation protocol with ultrasonic irrigation.

Fluorotic Enamel Susceptibility to Dental Erosion and Fluoride Treatment.

The purpose of this in vitro study was to test the hypothesis that fluoride treatment can prevent dental erosion on fluorotic enamel of different severities. It followed a 3×2 factorial design, considering a) fluorosis severity: sound (TF0, Thylstrup-Fejerskov Index), mild (TF1-2), moderate (TF3-4); and b) fluoride treatment: 0 (negative control) and 1150ppmF. Human molars with the three fluorosis severities (n=16, each) were selected and randomly assigned to the two fluoride treatments (n=8). Enamel blocks (4×4mm) were prepared from each tooth and subjected to a dental erosion cycling model, for 10 days. The daily cycling protocol consisted of erosive challenges (1% citric acid, pH 2.4), interspersed by periods of immersion in artificial saliva, and three 2-minute treatments with either 0 or 1150ppm F. The enamel volume loss (mm3) was calculated by subtracting values obtained by microtomography before and after cycling. Two-Way ANOVA showed no significant interaction between fluorosis severity and fluoride treatment (p=0.691), and no significant effect for either fluorosis severity (TF0 mean±standard-deviation: 13.5(10-2±0.42(10-2, TF1-2: 1.50(10-2±0.52(10-2, TF3-4: 1.24(10-2±0.52(10-2, p=0.416) or treatment (0ppmF: 1.49(10-2±0.53(10-2; 1150ppmF: 1.21(10-2±0.42(10-2; p=0.093), when evaluated independently. Considering the limitations of this in vitro study, the presence and severity of fluorosis in enamel do not appear to affect its susceptibility to dental erosion. Fluoride treatment was not effective in preventing the development of dental erosion in both sound and fluorotic enamel substrates under our experimental conditions.

Comparison of Self-Etching Adhesives and Etch-and-Rinse Adhesives on the Failure Rate of Posterior Composite Resin Restorations: A Systematic Review and Meta-Analysis.

The aim of this study was to perform a systematic review with meta-analysis on the comparison of self-etching adhesives and etch-and-rinse adhesives with respect to the failure rate of posterior composite resin restorations. The study protocol was registered in PROSPERO (CRD42017078015), following PRISMA recommendations and PICO search strategy. Literature search was performed in the following databases: MEDLINE, ISI Web of Science, LILACS, SCOPUS, and Cochrane Library through July 2021. Six studies from five randomized clinical trials were included in the qualitative synthesis. The funnel plot detected important bias (all studies out of the funnel area). The meta-analysis showed a positive summary Cohen H effect size of 0.406 (95% CI: 0.100; 0.713, p = 0.009), favoring etch-and-rinse adhesives. The total number of failures (including restorations that required replacement and those that did not require replacement) were attributed to either marginal adaptation (five studies) or marginal staining (one study). A very low certainty of the evidence was obtained through GRADE analysis. In conclusion, current available evidence indicates that etch-and rinse adhesives performed better (with a low effect size) than self-etching adhesives in terms of failure rates in posterior composite restorations.

Shaping efficiency of XP-endo shaper and Mtwo instruments in long oval root canals: A micro-CT study.

This study evaluated the shaping ability of XP-endo Shaper and Mtwo systems in long-oval-shaped canals of extracted human mandibular molars using micro-computed tomography (micro-CT). Images recorded before and after preparation were evaluated for morphometric measures regarding increase in canal volume, dentin removed, surface area, untouched walls and structure model index (SMI). Data were statistically analysed using the Mann-Whitney test with 5% of significance. On both groups, the root canal preparation significantly increased all analysed parameters (P > 0.05). There was no statistical difference between XP-endo Shaper and Mtwo systems in the increase of the canal volume (30.50%-27.82%), in volume of dentin removed (2.77%-2.40%), in the increase of the canal surface area (11.30%-8.86%), in canal untouched surfaces (9.57%-8.51%) and in the SMI (2.59%-2.68%), respectively. XP-endo Shaper and Mtwo systems showed similar shaping efficiency and were not able to completely prepare the walls of long-oval-shaped canals of extracted human mandibular molars.

Assessment of Mechanical Root Canal Preparation with Centric Reciprocating or Eccentric Rotary Kinematics: A Micro-computed Tomographic Study.

INTRODUCTION: The aim of this study was to compare, using micro-computed tomographic imaging, the preparation of mesial canals of mandibular molars with the Reciproc (VDW GmbH, Munich, Germany) and XP-endo Shaper (FKG, La Chaux-de-Fonds, Switzerland) systems, evaluating changes in dentin and canal volume, the percentage of untouched walls, the volume of accumulated hard tissue debris, and root canal deviation in the apical third. METHODS: Twenty-four mandibular molars with 2 mesial root canals and a single foramen were anatomically paired and divided into 2 experimental groups (n = 12) according to the system used. The specimens were scanned before and after preparation with the SkyScan 1176 microtomographic scanner (Bruker-microCT, Kontich, Belgium) at a resolution of 17.42 µm. The resulting data were statistically compared at a significance level of 5% using the Student t test and the Mann-Whitney test. RESULTS: A significant difference was observed in the untouched surface area for the total canal and the cervical and middle thirds, with the lowest untouched surface area in the XP-endo Shaper group (P < .05). The volume of accumulated hard tissue debris was significantly higher in the Reciproc group in the total canal as well as in the middle and apical thirds. There was no significant difference between the groups regarding the volume of dentin removed or the increase in canal volume and surface area (P > .05). CONCLUSIONS: The XP-endo Shaper touched more walls and left less accumulated hard tissue debris in the root canal system than the Reciproc group. Although the XP-endo Shaper showed superior results, neither system was able to fully prepare the root canal.

Root canal curvature influences uncontrolled removal of dentin and cleaning efficacy after ultrasonic activation

Abstract This study evaluated the correlation between root canal curvature and the effects of ultrasonic irrigation in the following parameters: volume of uncontrolled dentin removal (UDRVol), maximum depth of dentin defects, removal of accumulated hard tissue debris (AHTD), and canal transportation in prepared curved root canals. Twenty-four human permanent mandibular molars were divided into two groups according to root canal curvature: moderate curvature (MC: mean 25°); and severe curvature (SC: mean 48°). The specimens were scanned using an X-ray microcomputed scanner (Skyscan 1172) before and after cleaning and shaping and after the final irrigation protocol with ultrasonic irrigation. There was a moderate correlation between the degree of root canal curvature and the volume of remaining AHTD (p<0.05) and between the degree of root canal curvature and maximum depth of defects due to uncontrolled removal of dentin (p<0.05). The teeth in the SC group had a greater maximum depth of defects on the dentin wall in the apical third than the teeth in the MC group (p <0.05). Both groups had a significant reduction of AHTD in all canal thirds, but the amount of remaining AHTD in the middle and apical thirds and the whole canal was significantly greater in the SC than in the MC group (p <0.05). Canal transportation was not influenced by the canal curvature in all thirds (p >0.05). This study concluded that root canal curvature affects significantly the uncontrolled removal of dentin and remaining AHTD volume after the final irrigation protocol with ultrasonic irrigation.

Resumo Este estudo avaliou a correlação entre a curvatura do canal radicular e os efeitos da irrigação ultrassônica nos seguintes parâmetros: volume de remoção não controlada de dentina (UDRVol), profundidade máxima do desgaste de dentina, remoção de debris de tecido duro acumulado (AHTD) e transporte em canais radiculares curvos. Vinte e quatro molares inferiores humanos permanentes foram divididos em dois grupos de acordo com a curvatura do canal radicular: curvatura moderada (MC: média de 25°); e curvatura acentuada (SC: média de 48°). Os espécimes foram digitalizados usando um scanner microcomputador de raios X (Skyscan 1172) antes e depois da limpeza e modelagem e após a irrigação ultrassônica. Houve uma correlação moderada entre o grau de curvatura do canal radicular e o volume de AHTD remanescente (p<0,05) e entre o grau de curvatura do canal radicular e a profundidade máxima de defeitos devido à remoção descontrolada de dentina (p<0,05). Os dentes do grupo SC apresentaram maior profundidade máxima de defeitos na parede dentinária no terço apical do que os dentes do grupo MC (p<0,05). Ambos os grupos tiveram uma redução significativa de AHTD em todos os terços do canal, mas a quantidade de AHTD remanescente nos terços médio e apical e em todo o canal foi significativamente maior no grupo SC do que no grupo MC (p <0,05). O transporte do canal não foi influenciado pela curvatura do canal em todos os terços (p > 0,05). Este estudo concluiu que a curvatura do canal radicular afeta significativamente a remoção descontrolada de dentina e o volume remanescente de AHTD após a irrigação ultrassônica.

Fluorotic Enamel Susceptibility to Dental Erosion and Fluoride Treatment

Abstract The purpose of this in vitro study was to test the hypothesis that fluoride treatment can prevent dental erosion on fluorotic enamel of different severities. It followed a 3×2 factorial design, considering a) fluorosis severity: sound (TF0, Thylstrup-Fejerskov Index), mild (TF1-2), moderate (TF3-4); and b) fluoride treatment: 0 (negative control) and 1150ppmF. Human molars with the three fluorosis severities (n=16, each) were selected and randomly assigned to the two fluoride treatments (n=8). Enamel blocks (4×4mm) were prepared from each tooth and subjected to a dental erosion cycling model, for 10 days. The daily cycling protocol consisted of erosive challenges (1% citric acid, pH 2.4), interspersed by periods of immersion in artificial saliva, and three 2-minute treatments with either 0 or 1150ppm F. The enamel volume loss (mm3) was calculated by subtracting values obtained by microtomography before and after cycling. Two-Way ANOVA showed no significant interaction between fluorosis severity and fluoride treatment (p=0.691), and no significant effect for either fluorosis severity (TF0 mean±standard-deviation: 13.5(10-2±0.42(10-2, TF1-2: 1.50(10-2±0.52(10-2, TF3-4: 1.24(10-2±0.52(10-2, p=0.416) or treatment (0ppmF: 1.49(10-2±0.53(10-2; 1150ppmF: 1.21(10-2±0.42(10-2; p=0.093), when evaluated independently. Considering the limitations of this in vitro study, the presence and severity of fluorosis in enamel do not appear to affect its susceptibility to dental erosion. Fluoride treatment was not effective in preventing the development of dental erosion in both sound and fluorotic enamel substrates under our experimental conditions.

Resumo Este estudo in vitro foi testou a hipótese de que o tratamento com flúor pode prevenir a erosão dentária no esmalte fluorótico de diferentes severidades. O objetivo deste estudo foi: investigar o efeito protetor dos fluoretos contra a erosão e abrasão simuladas no esmalte fluorótico. Seguiu um desenho fatorial 3×2, considerando a) severidade da fluorose em 3 níveis: hígido (TF0, Índice Thylstrup-Fejerskov), suave (TF1-2), moderada (TF3-4); b) tratamento com flúor: 0 (controle negativo) e 1150ppmF. Molares humanos com as três severidades de fluorose (n=16, cada) foram selecionados e distribuídos aleatoriamente para os dois tratamentos com flúor (n=8). Blocos de esmalte (4×4mm) foram preparados a partir de cada dente e submetidos a um modelo de ciclo de erosão dentária, por 10 dias. O protocolo de ciclagem diária consistiu em seis desafios erosivos de 5 minutos (1% de ácido cítrico, pH 2,4), intercalados por seis períodos de imersão em saliva artificial e três tratamentos de 2 minutos com 0 ou 1150ppmF. O volume do esmalte perdido foi calculado subtraindo o perfil superficial 3D obtido por microtomografia antes e depois da ciclagem. A ANOVA de dois fatores não mostrou interação significativa entre a severidade da fluorose e o tratamento com flúor (p = 0,691) e nenhum efeito significativo para a severidade da fluorose (TF0 média+/desvio padrão: 13,5(10-2±0,42(10-2, TF1-2: 1,50(10-2±0,52(10-2, TF3-4: 1,24(10-2±0,52(10-2, p=0,416) ou tratamento (0: 1,49(10-2±0,53(10-2; 1150ppmF: 1,21(10-2±0,42(10-2, p=0,093), quando avaliados independentemente. Considerando as limitações deste estudo in vitro, a presença e severidade da fluorose no esmalte não parece afetar sua suscetibilidade à erosão dentária. O tratamento com flúor não foi eficaz na prevenção do desenvolvimento da erosão dentária em esmalte hígido e fluorótico, sob as condições experimentais utilizadas.

In vitro effects of nano-hydroxyapatite paste on initial enamel carious lesions.

PURPOSE: The purpose of this study was to analyze the protective effect of remineralizing agents on enamel caries lesions using surface Knoop microhardness testing (KHN) and atomic force microscopy (AFM). METHODS: Forty-eight human enamel blocks were assigned to four groups (N=12): (1) control (without agent); (2) fluoride varnish (Duraphat); (3) nano-HAP paste (Desensibilize Nano P); and (4) casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (MI Paste Plus). Incipient caries-like lesions were artificially developed. Cariogenic challenge (pH-cycling) was performed for seven days. The pastes were applied before each immersion in demineralization solution, and the varnish was applied only once. KHN values were obtained at baseline, after incipient enamel lesion, and after challenge. The percentage of surface hardness recovery (%SMHR) was performed, and the surface morphology was evaluated by atomic force microscopy (AFM). ANOVA, Tukey's, and student paired t tests were applied at P<.05. RESULTS: After the cariogenic challenge, the nano-HAP group showed significantly higher KHN and %SMHR values than varnish. The CPP-ACP group showed no increase in KHN. The nano-HAP group showed, via AFM, a protective layer formation with globular deposits on the surface. CONCLUSION: SMHR and AFM morphology revealed that nano-hydroxyapatite paste showed a protective effect against in vitro enamel caries development.

In Vitro Effects of Nano-hydroxyapatite Paste on Initial Enamel Carious Lesions.

PURPOSE: The purpose of this study was to analyze the protective effect of remineralizing agents on enamel caries lesions using surface Knoop microhardness testing (KHN) and atomic force microscopy (AFM). METHODS: Forty-eight human enamel blocks were assigned to four groups (N=12): (1) control (without agent); (2) fluoride varnish (Duraphat); (3) nano-HAP paste (Desensibilize Nano P); and (4) casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (MI Paste Plus). Incipient caries-like lesions were artificially developed. Cariogenic challenge (pH-cycling) was performed for seven days. The pastes were applied before each immersion in demineralization solution, and the varnish was applied only once. KHN values were obtained at baseline, after incipient enamel lesion, and after challenge. The percentage of surface hardness recovery (%SMHR) was performed, and the surface morphology was evaluated by atomic force microscopy (AFM). ANOVA, Tukey's, and student paired t tests were applied at P<.05. RESULTS: After the cariogenic challenge, the nano-HAP group showed significantly higher KHN and %SMHR values than varnish. The CPP-ACP group showed no increase in KHN. The nano-HAP group showed, via AFM, a protective layer formation with globular deposits on the surface. CONCLUSION: SMHR and AFM morphology revealed that nano-hydroxyapatite paste showed a protective effect against in vitro enamel caries development.

In vitro Effect of Erosive Challenge on Surface Microhardness of Orthodontic Composites

Objective: To evaluate in vitro the effect of erosive challenge and continuous immersion in cola drink on surface microhardness of orthodontic composites. Material and Methods: Forty samples of three composites (Transbond XT, Quick Cure and Ortho Cem) were prepared (4 x 2 mm) and distributed into 4 groups (n=10): erosive challenge, artificial saliva immersion (control 1), continuous cola immersion and artificial saliva immersion (control 2). Erosive challenge was performed 4 times per day (5 min) in cola drink for 2 h in artificial saliva for 7 days. Samples of continuous cola immersion group were soaked in cola drink for 5 weeks and the beverage was renewed every two days. Control samples were immersed in artificial saliva for 7 days (control 1) and 5 weeks (control 2). Vickers microhardness (VHN) measurements were performed before and after erosive challenge and continuous immersion. Data were evaluated by paired Student's T-test, ANOVA one-way and Tukey tests (α = 0.05). Results: After 7 days of erosive challenge, there was no statistical difference between VHN values before and after erosive challenge and artificial saliva immersion. However, after 5 weeks of cola drink and artificial saliva immersion, significant reduction in VHN values was observed for all composites when compared to baseline values, and specimens immersed in cola drink showed lower VHN compared to those immersed in saliva, regardless of composite composition. Conclusion: After 7 days of erosive challenge, there was no alteration in superficial VHN of orthodontic composites. However, after 5 weeks of immersion in cola drink, significant reduction of VHN values was observed for all composites.