Effect of fluoride application during radiotherapy on enamel demineralization

Impact of radiotherapy in chemical composition and mechanical properties of human cervical dentin: an in vitro study

BACKGROUND

Ionizing radiation directly affects hard dental tissues, compromising the dental structure, which results in damage to dentin collagen fibers and impacts the integrity of the dentin-enamel junction (DEJ).

OBJECTIVE

To evaluate the effects of radiotherapy on the chemical composition and mechanical properties of human cervical dentin.

METHODOLOGY

Ten third molars were divided into control/non-irradiated and irradiated groups (n=5). The irradiated teeth were subjected to in vitro radiotherapy with the following protocol: 1.8 Gy daily, five days per week for eight weeks, totaling 72 Gy. The dentin in the cervical region was evaluated for each group. The chemical composition was assessed using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, focusing on the mineral/matrix ratio (M:M), carbonate/mineral ratio (C:M), and amide I/amide III ratio. Amide I/CH2 ratio was used to assess collagen quality, as amide I reflects protein conformation and hydrogen bonding, while CH2 indicates side-chain vibrations with low sensitivity to molecular orientation. Nanohardness and elastic modulus were evaluated by instrumented indentation. Scanning electron microscopy (SEM) was used to assess the enamel's morphology. Statistical analysis of each parameter was performed using a t-test.

RESULTS

The FTIR analysis showed statistically significant differences in the C:M ratio (p=0.004) and amide I/amide III ratio (p=0.007). Raman spectroscopy revealed significant differences in the M:M ratio (p<0.001), as well as in the amide I/amide III (p<0.001) and amide I/CH2 ratios (p<0.001). Additionally, nanohardness (p=0.04) and the elastic modulus (p=0.003) showed statistically significant differences. SEM images revealed sound dentin shows normal tissue organization, whereas irradiated dentin showed no clear limit between peri and intertubular dentin.

CONCLUSIONS

Radiotherapy induced significant changes in dentin composition and mechanical properties, characterized by increased organic content and phosphate levels, reduced carbonate, and decreased nanohardness and elastic modulus. These findings highlight the adverse effects on dentin's structural integrity.

Effect of different protocols in preventing demineralization in irradiated human enamel, in vitro study

BACKGROUND

This in vitro study evaluated the efficacy of professional and home-use fluoride regimens for protecting irradiated enamel, undergoing pH cycling resembling xerostomia.

METHODS

Sixty human premolar teeth were irradiated with a total dose of 70 Gy and subsequently sectioned into 3 × 3 cm enamel slabs. These slabs were randomly distributed into five groups (n = 12 per group): professional-use groups received fluoride varnish either weekly (FV1) or biweekly (FV2); home-use groups applied 5000 ppm (FT5) or 1450 ppm (FT) fluoride toothpaste; and a control group (control) received no treatment. Following radiation, microhardness was measured to establish baseline values. Following 28 days of pH cycling and concurrent fluoride therapy, microhardness was reassessed on day 7, 14, 21, and 28. After the pH cycling period, surface morphology was examined using scanning electron microscopy.

RESULTS

All groups demonstrated declines over the 28-day pH cycling period. FV1 and FV2 maintained higher microhardness relative to control (p < 0.0001). FT5 consistently showed better preservation of enamel microhardness compared to FT (p < 0.0001), with both outperforming control (p < 0.0001), albeit FT to a lesser extent.

CONCLUSION

Fluoride treatments significantly enhanced the enamel's resistance to pH reduction caused by radiation. It is recommended to apply professional fluoride varnish biweekly and use 5000 ppm fluoride toothpaste twice daily for the most effective enhancement of pH resistance in irradiated enamel.

Radiation-Induced Caries: Exploring the Pathway to Manage the Challenge

Radiation-induced caries represent a frequent and serious complication of head and neck radiotherapy, significantly affecting patients' quality of life. Their development results from several factors, including the direct effects of radiotherapy on dental tissues, as well as indirect effects related to xerostomia and changes in saliva. Diagnosis is based on clinical and radiographic assessment, which often reveals a specific pattern of demineralization. The management of these caries requires a comprehensive approach, combining prevention, treatment of lesions, and regular follow-up. It is essential to establish long-term fluoride prophylaxis, and advice on oral hygiene and nutrition, in order to prevent new lesions. The choice of dental restorations must be considered according to the state of salivation and the caries risk, favoring materials adapted to the specificities of radiotherapy.

Oral Management of Patients Undergoing Head and Neck Cancer Treatment

Oral cancer accounts for around 30 percent of all cancers in India. These cancers are usually managed either by surgery, radiotherapy, chemotherapy or a combination of these modalities. Dental oncologists play an integral part in the multidisciplinary team, including surgeons, radiation and medical oncologists, nurses, physician assistants, nutritionists, psychologists and social workers to efficiently manage cancer patients. Oral complications associated with cancer therapy can range from minor mucositis or infections to severely debilitating conditions such as osteonecrosis of jaws, which can disrupt the ongoing cancer therapy and jeopardize the overall quality of life of the patient. This highlights the primary role of a dentist in the efficient identification and management of potential oral foci of infection and subsequent prevention of the onset of these complications. This necessitates accurate, evidence-based knowledge and extensive training of dental oncologists to provide state-of-the-art management strategies. This article aims to review oral management before, during and after therapy in patients undergoing treatment for cancers affecting the head and neck region.

Acid challenge exacerbates activation of matrix metalloproteinases in permanent teeth undergoing radiotherapy

The aim of this study was to investigate the effect of acid challenge on the activation of matrix metalloproteinases (MMPs) in the Dentinoenamel junction of primary and permanent teeth submitted to radiotherapy. For this purpose, a total of 178 dental fragments obtained from molars were used, and randomly divided into 2 groups (primary and permanent teeth) / 4 experimental subgroups (irradiated and non-irradiated, demineralized and non-demineralized). The fragments were exposed to radiation, with a dose fraction of 2 Gy, for 5 consecutive days, until a total dose of 60 Gy was reached, with a total of 30 cycles, for 6 weeks. To determine the activity of MMPs on the dentinoenamel junction (DEJ), in situ zymography assays on 0.6mm dental fragments were performed. To assess whether MMP activity would be impacted by an acidic environment, the fragments were placed in a demineralizing solution (pH of 4.8). The finding was that irradiation activated MMPs in DEJ and these effects were more evident in permanent when compared with primary teeth. When the effect of an acid challenge on MMPs activity was investigated, demineralization was observed not to increase MMPs activity in non-irradiated teeth, but it did increase MMPs activity in irradiated teeth. In conclusion, an acid challenge was found to exacerbate activation of MMPs in DEJ of permanent teeth submitted to irradiation, but not in primary teeth.

Color stability and microhardness alteration of irradiated dental enamel treated with a high fluoride concentration toothpaste

OBJECTIVES

Radiotherapy (RT) is a kind of head and neck cancer (HNC) treatment, which is associated to the habit of smoking and can develop collateral effects in the oral cavity, such as the increase of caries prevalence. This study evaluated the color alteration, the microhardness, and the remineralizing potential of high fluoride concentration toothpastes on irradiated teeth.

MATERIALS AND METHODS

Forty bovine teeth were used (6 × 6 × 2 mm) and after color (EasyShade, VITA) and microhardness initial readings were separated into two groups: exposed to cigarette smoke and non-exposed. All samples were submitted to RT (30 Gy) and to cariogenic challenge. New color and microhardness readings were done. After RT (60 Gy), the samples were submitted to simulated toothbrushing (73,000 cycles = 5 years of brushing) with two different toothpastes: conventional (1450 ppm) and high fluoride concentration (5000 ppm). Final color and microhardness readings were done after brushing. Data were analyzed with 2-way ANOVA with repeated measures and Tukey's test (p < .05).

RESULTS

There was no color difference after RT, nor after brushing (p > .05). However, after brushing, microhardness values increased for the samples treated with high fluoride concentration toothpaste (p < .05).

CONCLUSION

Radiotherapy did not influence the teeth color, and the high fluoride concentration toothpaste presented remineralizing potential; therefore, it could be used on the caries prevention related to HNC radiation.

CLINICAL RELEVANCE

Considering its remineralizing potential, toothpastes with high fluoride concentration could be a proper alternative for caries prevention in patients undergoing radiotherapy.

Evaluation of the changes in physical properties and mineral content of enamel exposed to radiation after treating with remineralization agent

OBJECTIVE

The aim of this study was to investigate the effect of different remineralization agents on the physical properties and elemental content of enamel exposed to radiation.

MATERIAL AND METHOD

The enamel surfaces of impacted third molar teeth were prepared, and six study groups were created (n = 6). Next, 60 Gy radiation was applied to each group. Between applications, each group except for the control group was treated with a different remineralization agent (sodium fluoride, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), casein phosphopeptide amorphous calcium phosphate with fluorite (CPP-ACFP), bioactive glass, or chitosan). The results were evaluated in terms of pre- and post-radiation values and the difference between the two. The paired-samples t test and analysis of variance test were used in the analysis of normally distributed hardness and roughness values, while Wilcoxon's signed ranks test, and the Kruskal Wallis and Mann-Whitney U tests were used in the analysis of elemental content without normal distribution.

RESULTS

A statistically significant decrease was observed in microhardness measurements in all groups. Intragroup evaluation revealed a statistically significant difference between the NaF and bioactive glass groups (p < 0.05). No significant difference was observed between the groups' roughness measurements (p < 0.05). Intergroup evaluation of surface roughness revealed a significant difference in the CPP-ACFP and chitosan groups (p < 0.05). Pre- and post-radiation oxygen, magnesium, and potassium levels and Ca/P ratios also differed significantly (p < 0.05).

CONCLUSION

Radiation caused a statistically significant difference in the microhardness and elemental content of enamel. However, no significant difference was observed in enamel roughness. The applied remineralizing agents have a partial ameliorating effect on the adverse impacts of radiation.

CLINICAL RELEVANCE

Radiation causes changes in the mechanical properties and elemental content of tooth enamel. Remineralizing agent application is a promising option in reducing the adverse effects of irradiation.

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.