Radiotherapy in the head and neck region influences the chemical and mechanical properties of intraradicular dentin.

OBJECTIVES: To investigate the chemical and mechanical properties of intraradicular dentin submitted to radiotherapy. MATERIALS AND METHODS: Sixteen mandibular incisors were divided into two groups (n = 8): non-irradiated and irradiated. The irradiated teeth were obtained from head and neck radiotherapy patients, with a total dose ranging from 70.2 to 72 Gy divided into 1.8 Gy daily. After sample preparation, intraradicular dentin slices of each root third were evaluated by Raman spectroscopy, energy dispersive spectroscopy and Knoop microhardness test. Data were analyzed by Two-way ANOVA and Tukey's test (α = 0.05). RESULTS: In Raman spectroscopy, carbonate and amide III showed a significant difference for irradiation and third (carbonate p = 0.021 and p < 0.001; amide III p < 0.001 and p = 0.001, respectively). For amide I, there was a significant difference for third (p < 0.001). For carbonate/mineral ratio, there was a significant difference for irradiation (p = 0.0016) and third (p < 0.001), with the irradiated middle third showing the lowest values. For amide I/amide III ratio, there was a significant difference for irradiation (p = 0.005) in the cervical third. In energy dispersive spectroscopy, carbon (p = 0.004; p = 0.020), phosphorus (p < 0.001; p = 0.009) and calcium (p = 0.008; p = 0.007) showed differences for irradiation and third, with the irradiated groups presenting lower values in cervical and middle thirds. For calcium/phosphorus ratio, there was a significant difference for irradiation (p < 0.001) in cervical and middle thirds. Regarding microhardness, there was a significant difference for irradiation (p < 0.001), with all irradiated groups showing lower microhardness values. CONCLUSIONS: The radiotherapy altered the chemical and mechanical properties of intraradicular dentin, mainly in the cervical and middle root thirds.

Effect of an enamel matrix derivative (Emdogain) on the microhardness and chemical composition of human root dentin: an in vitro study.

The advantage of using an Enamel matrix derivative EMD Emdogain as an intracanal medication could be a manner to strength the tooth structure, improving the physical and chemical properties of dentin. We tested, in vitro, the effect of Emdogain on the surface microhardness and chemical composition of root dentin. Ten human teeth were used to produce dentin specimens originated from the canal walls (n = 30) that remained in contact to Emdogain gel for 90 days. Baseline and 90-days after Emdogain treatment measurements were performed using Fourier Transform Infrared Spectroscopy (ATR/FTIR), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Knoop indenters. The use of EMD (Emdogain) for 90 days in contact with human root canal dentin specimens did not alter the microhardness and morphology of dentin. The elemental structure of dentin was altered because there was a reduction in carbonate content.

Chemical analysis of irradiated root dentin and its interaction with resin cements.

OBJECTIVES: To investigate the chemical changes in root dentin submitted to ionizing radiation and how it affects the interaction with resin cements. MATERIALS AND METHODS: Forty human premolars were randomly divided into two groups (n = 20): non-irradiated and irradiated. They were randomly subdivided according to the type of resin cement (n = 10): conventional (RelyX ARC, 3 M ESPE) or self-adhesive (RelyX U200, 3 M ESPE). After cementation of the fiberglass posts, the roots were sectioned to be analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and confocal laser scanning microscopy (CLSM). The data obtained from FTIR and Raman were analyzed using two-way ANOVA followed Tukey's test (α = 0.05). For CLSM, a descriptive analysis was performed. RESULTS: In the FTIR, there was a significant difference between the non-irradiated and irradiated groups for phosphate (p = 0.011), carbonate (p < 0.001), amide III (p = 0.038), and carbonate/mineral ratio (p < 0.001). Regarding the root third, there was a difference for amide I (p = 0.002), mineral/matrix ratio (p = 0.001), and amide I/CH2 (p = 0.026) between the cervical and the others. Raman spectroscopy revealed no difference between groups for 961/1458 cm-1 in the diffusion zone. CLSM showed a different interaction pattern for the two cements with the irradiated dentin from the cervical third. CONCLUSIONS: Ionizing radiation altered the chemical composition of root dentin, especially in the cervical third. The resin cements showed less interaction with the irradiated root dentin. CLINICAL RELEVANCE: As radiotherapy alters the chemical composition of root dentin, the interaction of resin cement with dentin can compromise the success of rehabilitation with fiberglass posts.

Effects of fractionation and ionizing radiation dose on the chemical composition and microhardness of enamel.

OBJECTIVE: To evaluate the chemical and mechanical properties of enamel submitted to different in vitro radiation protocols. DESIGN: Third molars were divided into seven groups (n = 8): non-irradiated (NI); a single dose of 30 Gy (SD30), 50 Gy (SD50), or 70 Gy (SD70) of radiation; or fractional radiation doses of up to 30 Gy (FD30), 50 Gy (FD50), or 70 Gy (FD70). Hemisections were analysed by Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS) and Knoop microhardness (KHN) test. One-way ANOVA followed by Bonferroni's post-hoc test compared the test groups with the NI. Two-way ANOVA was performed for the fractionation and radiation dose, followed by Bonferroni's test (α = 0.05). RESULTS: FTIR revealed differences for the amide I band between the NI and FD50 and NI and FD70 groups (p < 0.001). For the organic matrix/mineral ratio, the FD70 group presented a lower ratio compared to NI (p = 0.009). Excluding the NI group, there were differences between the FD30 and FD50 (p = 0.045) and the FD30 and FD70 groups (p < 0.001). For EDS, there were differences for Ca (p = 0.011) and Ca/P (p < 0.001), with the FD70 group presenting lower values compared to NI (p = 0.015; p < 0.001). For KHN, the FD70 group presented lower values than the NI (p = 0.002). Two-way ANOVA showed difference for the dose (p < 0.001), with the 70 Gy group presenting a lower KHN value within the fractionated groups. CONCLUSION: Fractional doses 70 Gy irradiation caused chemical and mechanical changes to enamel. Radiation applied in single or fractional doses produced different effects to enamel.

Head and neck cancer therapy-related oral manifestation management in the COVID-19 pandemic: a critical review.

With the onset of the new coronavirus disease (COVID-19) pandemic, the dental treatment of patients at risk of infection has become quite challenging. In view of this, patients with head and neck cancer may present with oral complications due to anticancer therapy, making dental assistance necessary. Thus, the objective of the study was to review the literature and critically discuss important concerns about the treatment of patients with head and neck cancer during the COVID-19 pandemic. Because dental professionals are in close contact with the main viral transmission routes, this study presents recommendations for management and protection during clinical dental care. The main characteristics and transmission routes of COVID-19 are also discussed. Dental professionals should control pain and the side effects of antineoplastic treatment and use preventive measures for infection control. During this pandemic, patients with head and neck cancer should not undergo elective procedures, even if they do not have symptoms or a history of COVID-19; therefore, in asymptomatic or painless cases, only preventive actions are recommended. In symptomatic or painful cases, precautions for safe interventional treatments must be implemented by following the hygiene measures recommended by health agencies and using personal protective equipment. During health crises, new protocols emerge for cancer treatment, and professionals must act with greater attention toward biosafety and updated knowledge. It is important to offer adequate individualized treatment based on the recommendations of preventative and interventional treatments so that patients can face this difficult period with optimized quality of life.

Head and neck cancer therapy-related oral manifestation management in the COVID-19 pandemic: a critical review

Abstract With the onset of the new coronavirus disease (COVID-19) pandemic, the dental treatment of patients at risk of infection has become quite challenging. In view of this, patients with head and neck cancer may present with oral complications due to anticancer therapy, making dental assistance necessary. Thus, the objective of the study was to review the literature and critically discuss important concerns about the treatment of patients with head and neck cancer during the COVID-19 pandemic. Because dental professionals are in close contact with the main viral transmission routes, this study presents recommendations for management and protection during clinical dental care. The main characteristics and transmission routes of COVID-19 are also discussed. Dental professionals should control pain and the side effects of antineoplastic treatment and use preventive measures for infection control. During this pandemic, patients with head and neck cancer should not undergo elective procedures, even if they do not have symptoms or a history of COVID-19; therefore, in asymptomatic or painless cases, only preventive actions are recommended. In symptomatic or painful cases, precautions for safe interventional treatments must be implemented by following the hygiene measures recommended by health agencies and using personal protective equipment. During health crises, new protocols emerge for cancer treatment, and professionals must act with greater attention toward biosafety and updated knowledge. It is important to offer adequate individualized treatment based on the recommendations of preventative and interventional treatments so that patients can face this difficult period with optimized quality of life.

Chemical analysis of in vivo-irradiated dentine of head and neck cancer patients by ATR-FTIR and Raman spectroscopy.

OBJECTIVES: To evaluate the effect of in vivo radiotherapy on the chemical properties of human dentine by Fourier-transform infrared spectroscopy (FTIR) and Raman analysis. MATERIALS AND METHODS: Chemical composition was evaluated comparing control and irradiated group (n = 8). Irradiated teeth were obtained from radiotherapy patients subjected to fractionated X-ray radiation of 1.8 Gy daily totaling 72 Gy. The teeth were sectioned according to the type of dentine (crown or root dentine), obtaining 3-mm dentine cervical slices. The analyzed parameters by FTIR and Raman spectroscopies were mineral/matrix ratio (M:M), carbonate/mineral ratio (C:M), amide I/amide III ratio, and amide I/CH2 ratio. Raman also calculated the phosphate and carbonate crystallinity. RESULTS: FTIR revealed that M:M had a decrease in both factors (p = 0.008; p = 0.043, respectively) and root dentine showed a lower C:M in the irradiated group (p = 0.003). Raman revealed a higher phosphate crystallinity and a lower carbonate crystallinity in crown dentine of irradiated group (p = 0.021; p = 0.039). For amide I/amide III, the irradiated showed a lower ratio when compared to the control group (FTIR p = 0.002; Raman p = 0.017). For amide I/CH2, the root dentine showed a higher ratio than the crown dentine in both methods (p < 0.001). CONCLUSIONS: Radiotherapy altered the chemical composition of human dentine. The exchange of phosphate-carbonate ions in the hydroxyapatite and higher concentration of organic components was found after radiotherapy. CLINICAL RELEVANCE: The increased risk of radiation-related caries in patients undergoing head and neck radiotherapy is due not only to salivary, dietary, and microbiological changes but also to changes in tooth chemical composition.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes.

OBJECTIVE: The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. MATERIAL AND METHODS: Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. RESULTS: Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. CONCLUSION: The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes

Abstract Resin cements have led to great advances in dental ceramic restoration techniques because of their ability to bond to both dental structures and restorative materials. Objective The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Material and Methods Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. Results Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. Conclusion The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Associação de cerâmicas na reabilitação estética do sorriso ­ utilização de cerâmica reforçada por dissilicato de lítio e cerâmica feldspática / Ceramics association in smile aesthetic rehabilitation ­ the use of ceramics reinforced by disilicate lithium and feldspar ceramic

A demanda de pacientes que buscam por tratamentos estéticos dos dentes anteriores está em constante crescimento. A busca incessante pelo desenvolvimento de novos materiais e técnicas odontológicas, visando procedimentos mais conservadores do elemento dental e resultado mais previsível, com excelentes propriedades estéticas e funcionais, tem levado as restaurações dos dentes anteriores a um novo patamar. As cerâmicas têm sido muito estudadas e, com isso, melhoras significativas nas suas propriedades mecânicas e estéticas foram obtidas. Associado a isso, o aperfeiçoamento de técnicas adesivas tornou possível a confecção de peças cerâmicas menos espessas, sem a necessidade de grandes desgastes da estrutura dentária. O aprimoramento do diagnóstico e o planejamento reverso possibilitaram resultados bastante previsíveis. Nesse contexto, o relato de caso apresentado neste artigo descreve a sequência clínica de reabilitação estética dos dentes 11, 12, 21 e 22 empregando facetas indiretas de cerâmica reforçadas por dissilicato de lítio associadas à aplicação de cerâmica feldspática, buscando a reprodução das características naturais dos dentes. O conhecimento da técnica operatória, dos materiais restauradores e a qualidade do trabalho protético são fundamentais para se obter um resultado estético e funcional de excelência (AU).

The number of patients seeking for aesthetic treatments of the anterior teeth is constantly growing. The incessant search for the development of new dental materials and techniques, aiming more conservative procedures of the dental element and more predictable results with excellent aesthetic and functional properties, has led the restoration of anterior teeth to a new level. Ceramics have been studied and thus significant improvements in their mechanical and aesthetic properties were obtained. Associated with this, the improvement of adhesive techniques has made possible the production of thinner ceramic parts without the need of large wear of the tooth structure. Improved diagnosis and reverse planning allowed fairly predictable results. In this context, the case report presented in this article describes the clinical sequence of aesthetic restoration of teeth 11, 12, 21 and 22 employing indirect pottery facets reinforced by lithium disilicate associated with application of feldspar ceramic seeking reproduction of the natural characteristics of teeth. The Knowledge of surgical techniques, restorative materials and the quality of prosthetic work are fundamental to get aesthetic and functional results of excellence (AU).