Radiation-related caries and early restoration failure in head and neck cancer patients. A polarized light microscopy and scanning electron microscopy study

Effect of Ionizing Radiation on the Mechanical Properties of Two Dental Materials Commonly Used in Primary Teeth

Aim

The purpose of this in vitro study was to evaluate the effect of radiotherapy on flexural strength, microhardness, and surface roughness of bulk fill composite (X-tra fil) and glass ionomer (EQUIA Forte HT).

Materials and methods

A total of 40 specimens were prepared for each test and were divided into two groups according to the material used (composite or glass ionomer cement), and each group was divided into two subgroups (n = 10) according to radiation condition, irradiated subgroup, subjected to 50 Gy by multienergy linear accelerator delivered in one shot and control subgroup.

Results

Control samples of flexural strength and microhardness had a significantly higher value than irradiated samples in both materials. Regarding the surface roughness, irradiated samples had a significantly higher value than the control samples in both materials.

Conclusion

Irradiation with a linear accelerator had a negative impact on the flexural strength and microhardness of both materials. Moreover, it increased the surface roughness for both materials. Bulk fill composite is the dental restorative material of choice in head and neck cancer patients undergoing radiotherapy due to its high mechanical properties before and after radiation.

How to cite this article

Nagi BM, El-Korashy DI, Amin A El-S, et al. Effect of Ionizing Radiation on the Mechanical Properties of Two Dental Materials Commonly Used in Primary Teeth. Int J Clin Pediatr Dent 2023;16(5):758-762.

Effect of Cumulative Ionizing Radiation on Flexural Strength, Flexural Modulus, and Elasticity Modulus of Dentin in Unerupted Human Third Molars

Purpose

This in vitro study aimed to investigate the changes in mechanical properties in dentin of third molars after radiation therapy using variable doses and frequencies.

Methods and Materials

Rectangular cross sectioned dentin hemisections (N = 60, n = 15 per group; >7 × 4 × 1.2 mm) were prepared using extracted third molars. After cleansing and storage in artificial saliva, random distribution was performed to 2 irradiation settings, namely AB or CD (A, 30 single doses of irradiation [2 Gy each] for 6 weeks; B, control group of A; C, 3 single doses of irradiation [9 Gy each]; and D, control group of C). Various parameters (fracture strength/maximal force, flexural strength, and elasticity modulus) were assessed using a universal Testing Machine (ZwickRoell). The effect of irradiation on dentin morphology was evaluated by histology, scanning electron microscopy, and immunohistochemistry. Statistical analysis was performed using 2-way analysis of variance and paired and unpaired t tests at a significance level of 5%.

Results

Significance could be found considering the maximal force applied to failure when the irradiated groups were compared with their control groups (A/B, P < .0001; C/D, P = .008). Flexural strength was significantly higher in the irradiated group A compared with control group B (P < .001) and for the irradiated groups A and C (P = .022) compared with each other. Cumulative radiation with low irradiation doses (30 single doses; 2 Gy) and single irradiation with high doses (3 single doses; 9 Gy) make the tooth substance more prone to fracture, lowering the maximal force. The flexural strength decreases when cumulative irradiation is applied, but not after single irradiation. The elasticity modulus showed no alteration after irradiation treatment.

Conclusions

Irradiation therapy affects the prospective adhesion of dentin and the bond strength of future restorations, potentially leading to an increased risk of tooth fracture and retention loss in dental reconstructions.

Effectiveness of glass ionomer cements in the restorative treatment of radiation-related caries - a systematic review

PURPOSE

The aim of this systematic review was to investigate the clinical effectiveness of glass ionomer cements (GICs) compared to other restorative materials in the treatment of radiation-related caries.

METHODS

Two independent researchers searched literature databases (PubMed, Scopus, Web of Science, Cochrane Library, Lilacs/BBO) and the grey literature to identify clinical trials that compared GICs with other restorative materials for the treatment of radiation-related caries. The clinical criteria considered for the performance of the restorations were based on the parameters of marginal adaptation/anatomical form, secondary caries, retention, and cumulative failures of the restorations. The methodological quality and risk of bias were evaluated using the Cochrane Collaboration tool.

RESULTS

From a total of 511, only four articles fulfilled the inclusion criteria. Conventional GIC restorations presented higher marginal adaptation failures than the resin-modified glass ionomer cements (RM-GICs) and composite restorations in all of the follow-up periods. Secondary caries was not observed in conventional GIC restorations throughout the follow-up periods, in three out of four of the included studies. RM-GICs and composite restorations showed significantly lower cumulative failure rates than conventional GICs at 6-, 12-, and 18-month follow-ups.

CONCLUSION

Due to insufficient scientific evidence, it was not possible to conclude that GICs are more effective than other restorative materials for the treatment of radiation-related caries.

Impact of radiotherapy and shielding on the efficacy of the self-etch adhesive technique

Context:

The exposure to gamma radiation affects the enamel and dentin in teeth restored with composite restoration, but a little has been done to protect from the detrimental effect.

Aims:

The aim of this in vitro study was to evaluate the effect of gamma radiation, with or without shielding (0.5 mm thickness of lead), in Class V cavities prepared on teeth exposed before and after restoration using the self-etch adhesive technique.

Methods:

A total of 75 intact teeth were selected. The samples were divided into five groups: Group I (15 teeth) not exposed to gamma radiation. Group II and III exposed to gamma radiation as per the standardized radiation protocol (2 Gy/day for 5 days/week = 10 Gy/week for 6 weeks = 60 Gy). Group III shielded, using a “0.5 mm thickness of lead” molded into a “C” shaped tube. Standardized Class V cavities were prepared on the buccal surface of all teeth and were restored by composite. Groups IV (not shielded) and V (shielded) were then exposed to standardized radiation protocol. All the samples were evaluated for the assessment of microleakage under stereomicroscope.

Statistical Analysis Used:

Statistics were tabulated using the Kruskal–Wallis ANOVA test.

Results:

Samples showed a significant difference in dye penetration scores.

Conclusions:

The samples restored before being exposed to gamma radiations performed better. Shielding with 0.5 mm of lead has shown increased efficacy of self-etch adhesive system irrespective of the stage of exposure.

Dentin remineralization in acidic solution without initial calcium phosphate ions via poly(amido amine) and calcium phosphate nanocomposites after fluid challenges

OBJECTIVES

A previous study showed that the combination of poly(amido amine) (PAMAM) and rechargeable composites with nanoparticles of amorphous calcium phosphate (NACP) induced dentin remineralization in an acidic solution with no initial calcium (Ca) and phosphate (P) ions, mimicking the oral condition of individuals with dry mouths. However, the frequent fluid challenge in the oral cavity may decrease the remineralization capacity. Therefore, the objective of the present study was to investigate the remineralization efficacy on dentin in an acid solution via PAMAM + NACP after fluid challenges for the first time.

METHODS

The NACP nanocomposite was stored in a pH 4 solution for 77 days to exhaust its Ca and P ions and then recharged. Demineralized dentin samples were divided into four groups: (1) control dentin, (2) dentin coated with PAMAM, (3) dentin with recharged NACP composite, and (4) dentin with PAMAM + recharged NACP. PAMAM-coated dentin was shaken in phosphate-buffered saline for 77 days to desorb PAMAM from dentin. Samples were treated in pH 4 lactic acid with no initial Ca and P ions for 42 days.

RESULTS

After 77 days of fluid challenge, PAMAM failed to prevent dentin demineralization in lactic acid. The recharged NACP nanocomposite raised the pH to above 6.5 and re-released more than 6.0 and 4.0 mmol/L Ca and P ions daily, respectively, which inhibited further demineralization. In contrast, the PAMAM + NACP combined method induced great dentin remineralization and restored the dentin microhardness to 0.54 ± 0.04 GPa, which approached that of sound dentin (P = 0.426, P > 0.05).

CONCLUSIONS

The PAMAM + NACP combination achieved dentin remineralization in an acid solution with no initial Ca and P ions, even after severe fluid challenges.

CLINICAL RELEVANCE

The novel PAMAM + NACP has a strong and sustained remineralization capability to inhibit secondary caries, even for individuals with dry mouths.

Effects of ionizing radiation on surface properties of current restorative dental materials

To investigate the impact of radiotherapy on surface properties of restorative dental materials. A conventional resin composite-CRC (Aura Enamel), a bulk-fill resin composite-BFRC (Aura Bulk-fill), a conventional glass ionomer cement-CGIC (Riva self cure), and a resin-modified glass ionomer cement-RMGIC (Riva light cure) were tested. Forty disc-shaped samples from each material (8 mm diameter × 2 mm thickness) (n = 10) were produced according to manufacturer directions and then stored in water distilled for 24 h. Surface wettability (water contact angle), Vickers microhardness, and micromorphology through scanning electron microscopy (SEM) before and after exposition to ionizing radiation (60 Gy) were obtained. The data were statistically evaluated using the two-way ANOVA and Tukey posthoc test (p < 0.05). Baseline and post-radiation values of contact angles were statistically similar for CRC, BFRC, and RMGIC, whilst post-radiation values of contact angles were statistically lower than baseline ones for CGIC. Exposition to ionizing radiation statistically increased the microhardness of CRC, and statistically decreased the microhardness of CGIC. The surface micromorphology of all materials was changed post-radiation. Exposure to ionizing radiation negatively affected the conventional glass ionomer tested, while did not alter or improved surface properties testing of the resin composites and the resin-modified glass ionomer cement tested.

Disorders of Dental Hard Tissues Induced by Radioiodine-131 (I-131) Therapy Used in Differentiated Thyroid Cancer: An In Vitro Study

This study aimed to evaluate, in vitro, the effects of I-131 on enamel and dentin in healthy human incisive permanent maxillary teeth. Our in vitro model analogue with the in vivo conditions of differentiated thyroid carcinoma patients treated with I-131, consisted in a solution of I-131 dissolved in artificial saliva. A total of 48 teeth were divided into eight groups (n = 6): control, irradiation groups at 3, 6, 12, 24, 36, 48, and 192 h, respectively. At the end of radiation exposure, radioiodine activity of specimens was assessed. Fine microstructure, nanostructure, surface roughness, and hidroxyapatite (HAP) crystallite diameter were investigated by atomic force microscopy (AFM) to both enamel and dentin structures. There is a constant increase of radioactivity in dental structures at 3, 6, 12, 24 h, due to progressive retention and I-131 migration, with a maximum at 36 h. Enamel showed notable alterations, which was correlated with the increase of the treatment time. A relevant visible distance between the HAP prisms was observed after 24 h. The surface suffered a loss in its compact structure. I-131 acts in the same way on HAP crystallites in dentin as in those in enamel. It was noticed that their morpho-dimensional changes occurred only after 12 h of treatment. Radioiodine-131 determines degradation of enamel and dentin by starting from the alteration of the crystalline network of HAP prisms, transforming them from compact materials into an agglomeration of rocky submicron structures.

Irradiation therapy and chewing simulation: effect on zirconia and human enamel

PURPOSE

Ionizing radiation therapy (RT) is the main option for head and neck cancer treatment, but it is associated with multiple side effects. This study aimed to evaluate the effect of RT associated with chewing simulation on the surface of human enamel and Yttria-partially stabilized zirconia (Y-TZP).

METHODS

Maxillary premolar cusps and Y-TZP slabs were divided in 7 experimental groups: CO: no RT (control); EZ groups had irradiation applied to both, enamel and zirconia samples (simulating restoration prior to RT); E groups had irradiation applied to enamel only (simulating restoration after RT). RT doses were either 30, 50 or 70 Gray (Gy). Enamel cusps were abraded against zirconia slabs in a chewing simulator (CS - one million cycles/ 80 N/ 60 mm/min, 2 mm horizontal path, artificial saliva, 37˚ C). Zirconia hardness was evaluated before CS; zirconia roughness and enamel volume (wear) were evaluated before and after CS. Hardness and wear data were analyzed by one-way Analysis of Variance and Tukey post hoc test. Roughness was analyzed by Repeated Measures test and Bonferroni test (p=0.05).

RESULTS

There was no significant effect of enamel or zirconia irradiation on enamel cusp wear (p=0.226), regardless of the irradiation dose used - up to 70 Gy. Irradiation also did not affect Y-TZP surface roughness (p=0.127) and hardness (p=0.964).

CONCLUSIONS

RT does not promote significant changes to the surface characteristics of zirconia. Irradiated enamel abraded against zirconia does not show higher wear volume when compared to non-irradiated enamel.

Effect of ionizing radiation and chewing simulation on human enamel and zirconia

PURPOSE

To evaluate the effect of ionizing irradiation on human enamel and zirconia after chewing simulation.

METHODS

Twenty enamel and twenty translucent Yttria-stabilized zirconia (Y-PSZ) specimens were divided in 4 groups: Co (control) - no irradiation on enamel cusps/opposing zirconia slabs; E70 - irradiated (70 Gray) enamel cusps/opposing irradiated enamel slabs; Z70 - irradiated zirconia cusps/opposing irradiated zirconia slabs; EZ70 - irradiated enamel cusps/opposing irradiated zirconia slabs. Cusps were abraded against slabs in a chewing simulator (CS - one million cycles, 80 N, artificial saliva, 37˚C). Wear and roughness of zirconia and enamel were analyzed using a stylus profilometer. The abraded enamel was analyzed by Electron probe micro-analyzer (EPMA) and zirconia was characterized by nanoindentation and X-ray diffraction. One-way analysis of variance (ANOVA) and Tukey test were used for analysis of wear, Repeated Measures and Bonferroni test for roughness, and hardness and modulus values were compared using Wilcoxan Mann Whitney rank sum test (overall 5% significance).

RESULTS

Significantly higher volume loss was presented by cusps in the E70 group (p<0.001). Wear was similar between Co and EZ70 groups. There was no significant effect of irradiation on roughness of enamel or zirconia slabs (p=0.072). Irradiated Y-PSZ slabs had significantly higher hardness and modulus than non-irradiated ones and a 7% increase in m phase content was detected after irradiation.

CONCLUSIONS

The opposing surface characteristics played a more significant role on enamel wear than did ionizing radiation. However, radiation affects Y-PSZ crystalline composition, hardness and modulus of elasticity.

Acoustic diagnosis of elastic properties of human tooth by 320 MHz scanning acoustic microscopy after radiotherapy treatment for head and neck cancer

BACKGROUND

On the elastic profiles of human teeth after radiotherapy for head and neck cancers, generation of dental complications, which may bring several side effects preventing the quality of life, has not well clarified. Thus, we aimed to show the applicability of using 320 MHz Scanning Acoustic Microscopy (SAM) in the evaluation of the tooth damage acoustically at the micrometer level following radiation therapy, and also in the determination of the safe dose limits to impede severe dental damage.

METHODS

This prospective study was performed by SAM employed at 320 MHz by an azimuthal resolution of 4.7 μm resolving enamel and dentin. A total of 45 sound human third molar teeth collected between September 2018 and May 2019 were used for the acoustic impedance measurements pre- and post irradiation. Nine samples for each group (control, 2 Gy, 8 Gy, 20 Gy, 30 Gy and 60 Gy) were evaluated to acquire the acoustic images and perform a qualitative analysis. Scanning Electron Microscopy (SEM) images were obtained to establish a relationship between micromechanical and morphological characteristics of the teeth. Statistical analysis was conducted using the Student t-test succeded by Mann-Whitney U investigation (p < .05), while SEM images were assessed qualitatively.

RESULTS

The analysis included 45 sound teeth collected from men and women 18 to 50 years old. Post irradiation micromechanical variations of human teeth were significant only in the radiation groups of 30 Gy and 60 Gy compared to pre-irradiation group for enamel (7.24 ± 0.18 MRayl and 6.49 ± 028 MRayl; p < 0.05, respectively). Besides, the teeth subjected to radiation doses of 20, 30 and 60 Gy represented significantly lower acoustic impedance values relative to non-irradiated group for dentin (6.52 ± 0.43 MRayl, 5.71 ± 0.66 MRayl and 4.82 ± 0.53 MRayl p < 0.05), respectively.

CONCLUSIONS

These results are evidence for a safe acoustic examination device which may be a useful tool to visualize and follow the safe dose limits to impede severe dental damage through the radiation therapy treatment for head and neck cancers.

The effect of ionizing radiation on properties of fluoride-releasing restorative materials

The purpose of this study was to evaluate the effect of ionizing radiation from high energy X-ray on fluoride release, surface roughness, flexural strength, and surface chemical composition of the materials. The study groups comprised five different restorative materials: Beautifil II, GCP Glass Fill, Amalgomer CR, Zirconomer, and Fuji IX GP. Twenty disk-shaped specimens (8x2 mm) for fluoride release and 20 bar-shaped specimens (25 x 2x 2 mm) for flexural strength were prepared from each material. Each material group was divided into two subgroups: irradiated (IR) and non-irradiated (Non-IR). The specimens from IR groups were irradiated with 1.8 Gy/day for 39 days (total IR = 70.2 Gy). The amount of fluoride released into deionized water was measured using a fluoride ion-selective electrode and ion analyzer after 24 hours and on days 2, 3, 7, 15, 21, 28, 35, and 39 (n = 10). The flexural strength was evaluated using the three-point bending test (n = 10). After the period of measurement of fluoride release, seven specimens (n = 7) from each group were randomly selected to evaluate surface roughness using AFM and one specimen was randomly selected for the SEM and EDS analyses. Data were analyzed with two-way ANOVA and Tukey tests (p = 0.05). The irradiation significantly increased fluoride release and surface roughness for Amalgomer CR and Zirconomer groups (p < 0.05). No significant change in flexural strength of the materials was observed after irradiation (p > 0.05). The ionizing radiation altered the amount of fluoride release and surface roughness of only Amalgomer CR and Zirconomer. The effect could be related to the chemical compositions of materials.

Effect of the double application of universal adhesives on the dentine bond strength after radiotherapy

BACKGROUND

This study aimed to evaluate the effect of double application of universal adhesives on bond strength to dentine after ionizing radiation.

METHODS

One hundred and forty caries-free human third molars were used. Half of the teeth were irradiated (IR) (70.2 Gy). The IR and non-IR teeth were assigned into seven groups (n = 10). Universal adhesives Single Bond Universal (3M Oral Care), Gluma Bond Universal (Heraeus Kulzer) and Prime&Bond Elect (Dentsply) were employed (following manufacturer's instructions and double application). Two-step self-etch adhesive Clearfil SE Bond (Kuraray Noritake) was used as control. After composite build-ups were bonded to mid-coronal occlusal dentine surfaces, the specimens were stored in water (37°C/24 h) and sectioned into microspecimens. The specimens were subjected to μTBS testing (1.0 mm/min). Failure analysis was performed using stereomicroscope and scanning electron microscopy. Data were analysed with two-way ANOVA and Tukey's test (P = 0.05).

RESULTS

The radiotherapy caused reduction in the bond strength of universal adhesives when the adhesives were used with single application after radiotherapy (P < 0.05). The double application resulted in increased bond strength of the universal adhesives to IR dentine (P < 0.05).

CONCLUSIONS

The double application was beneficial in improving the dentine bond strength of universal adhesives affected by radiotherapy after ionizing radiation.

Effect of ionizing radiation on the properties of restorative materials

Aim

The aim of this study is to evaluate the effect of different doses of the ionizing radiation (0 Gy, 10 Gy, 30 Gy, and 60 Gy) on the physical properties of dental materials.

Methodology

Disc-shaped samples from each material (Ketac Molar Easymix, Vitro Molar, Vitremer, Vitro Fil Lc, Filtek Z 250 and Filtek Z 350) were made for water solubility, sorption analysis (n = 20), microhardness (n = 20), and surface roughness analysis (n = 24). Specimens were divided into four groups, according to radiation dose: control group (0 Gy), 10 Gy, 30 Gy, and 60 Gy. For water solubility and sorption analysis, the specimens were irradiated and were stored for 21 days to calculate the water solubility and sorption values. Microhardness analysis was carried out before and after irradiation doses. For surface roughness analysis, the specimens were submitted to brushing test, and after 24 h, initial surface roughness analysis was made in a rugosimeter. Subsequently, the samples were irradiated and final surface roughness analysis was made. The original water solubility and sorption, surface roughness, and microhardness values were subjected to ANOVA two-way statistical analysis and Paired t-test and Tukey post hoc test (α = 0.05), respectively.

Results

Water solubility and sorption values, and surface roughness values presented statistical difference between groups (0, 10, 30 e 60 Gy) for all materials.

Conclusions

High doses of ionizing radiation (30 Gy and 60 Gy) increased the surface roughness, sorption, and solubility for the most materials.

Dental remineralization via poly(amido amine) and restorative materials containing calcium phosphate nanoparticles

Tooth decay is prevalent, and secondary caries causes restoration failures, both of which are related to demineralization. There is an urgent need to develop new therapeutic materials with remineralization functions. This article represents the first review on the cutting edge research of poly(amido amine) (PAMAM) in combination with nanoparticles of amorphous calcium phosphate (NACP). PAMAM was excellent nucleation template, and could absorb calcium (Ca) and phosphate (P) ions via its functional groups to activate remineralization. NACP composite and adhesive showed acid-neutralization and Ca and P ion release capabilities. PAMAM+NACP together showed synergistic effects and produced triple benefits: excellent nucleation templates, superior acid-neutralization, and ions release. Therefore, the PAMAM+NACP strategy possessed much greater remineralization capacity than using PAMAM or NACP alone. PAMAM+NACP achieved dentin remineralization even in an acidic solution without any initial Ca and P ions. Besides, the long-term remineralization capability of PAMAM+NACP was established. After prolonged fluid challenge, the immersed PAMAM with the recharged NACP still induced effective dentin mineral regeneration. Furthermore, the hardness of pre-demineralized dentin was increased back to that of healthy dentin, indicating a complete remineralization. Therefore, the novel PAMAM+NACP approach is promising to provide long-term therapeutic effects including tooth remineralization, hardness increase, and caries-inhibition capabilities.

Direct radiation-induced effects on dental hard tissue

Background

Radiation caries is a complication of radiotherapy characterized by enamel erosion and dentin exposure. The mechanisms of characteristic radiation caries formation are not well-understood. The aim of this study was to evaluate the direct radiation-induced effects on dental hard tissue and investigate their role in the formation of radiation caries.

Methods

Sixty non-carious third molars were divided into three groups (n = 20), which would be exposed to 0 Gy, 30 Gy, and 60 Gy radiation, respectively. After radiation, microhardness and elastic modulus were measured at four depths by means of a Vickers microhardness tester and atomic force microscopy (AFM). The microstructure was observed by scanning electron microscopy (SEM). X-ray diffraction and Raman microspectroscopy were used to determine crystal properties and protein/mineral (2931/960 cm^− 1) ratios.

Results

A statistically significant decrease in microhardness and elastic modulus values 50 μm from the dentino-enamel junction (DEJ) in enamel was revealed in the 30-Gy and 60-Gy groups. With the increasing dose, destruction of interprismatic substance and fissures at the DEJ-adjacent region were found. A greater reduction of crystallinity was revealed in enamel compared with dentin. Raman spectroscopic analysis showed a slight increase of the protein/mineral ratio for enamel following accumulated radiation, while the protein/mineral ratio for dentin was decreased.

Conclusions

Radiation could directly alter the mechanical properties, micro-morphology, crystal properties, and chemical composition of dental hard tissue. The early destruction of DEJ-adjacent enamel, combined with decreased crystallinity of enamel under radiation exposure, may be related to the formation of characteristic radiation caries.

Efeito da radioterapia com raios x de alta energia sobre a resistência de união da dentina humana com resina composta – estudo in vitro

Objetivo: O objetivo deste estudo experimental é avaliar o efeito da radiação com raios X de alta energia na resistência de união entre dentina humana e resina composta. Métodos: Trinta terceiros molares humanos hígidos foram seccionados, produzindo superfícies oclusais planas de dentina, e distribuídos aleatoriamente em dois grupos (n=15): um não irradiado e restaurado com Resina Composta Filtek Z-250, 3M-ESPE® (G1, n=15 – grupo controle), outro irradiado e restaurado com Resina Composta Filtek Z-250, 3M-ESPE® (G2, n=15). O protocolo de radiação utilizado foi de 70 Gy no total. As amostras foram cortadas em palitos (área média de 1 mm2) e submetidas ao teste de microtração. Os dados foram comparados por meio do teste t-student (p <0,05). O padrão de fratura foi examinado em microscopia óptica e submetido ao teste exato de Fischer (p <0,05). Resultados: não houve diferença significativa entre o grupo de dentes não irradiados e irradiados (p=0,738). O grupo controle e o grupo irradiado apresentaram predominância no padrão de fratura de falhas coesivas em resina e/ou mistas e falhas adesivas foram verificadas somente no grupo dos dentes irradiados. Conclusões: A radiação não interfere significativamente na resistência de união da dentina humana restaurada com resina composta e que não houve influência significativa entre os grupos estudados em relação ao padrão de fratura.

Common oral complications of head and neck cancer radiation therapy: mucositis, infections, saliva change, fibrosis, sensory dysfunctions, dental caries, periodontal disease, and osteoradionecrosis

Patients undergoing radiation therapy for the head and neck are susceptible to a significant and often abrupt deterioration in their oral health. The oral morbidities of radiation therapy include but are not limited to an increased susceptibility to dental caries and periodontal disease. They also include profound and often permanent functional and sensory changes involving the oral soft tissue. These changes range from oral mucositis experienced during and soon after treatment, mucosal opportunistic infections, neurosensory disorders, and tissue fibrosis. Many of the oral soft tissue changes following radiation therapy are difficult challenges to the patients and their caregivers and require life-long strategies to alleviate their deleterious effect on basic life functions and on the quality of life. We discuss the presentation, prognosis, and management strategies of the dental structure and oral soft tissue morbidities resulting from the administration of therapeutic radiation in head and neck patient. A case for a collaborative and integrated multidisciplinary approach to the management of these patients is made, with specific recommendation to include knowledgeable and experienced oral health care professionals in the treatment team.

Poly (amido amine) dendrimer and dental adhesive with calcium phosphate nanoparticles remineralized dentin in lactic acid

Patients with dry mouth often have an acidic oral environment lacking saliva to provide calcium (Ca) and phosphate (P) ions. There has been no report on tooth remineralization in acidic pH4 and CaP ion-lacking solutions. The objective of this study was to develop a novel method of combining poly(amido amine) (PAMAM) with adhesive containing nanoparticles of amorphous calcium phosphate (NACP) for dentin remineralization in pH4 and CaP-lacking solution for the first time. Demineralized dentin was tested in four groups: (1) dentin control, (2) dentin with PAMAM, (3) dentin with NACP adhesive, (4) dentin with PAMAM + NACP adhesive. Dentin samples were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and hardness testing. Increasing the NACP filler level in adhesive from 0 to 40 wt% did not negatively affect the dentin bond strength (p > 0.1). NACP adhesive released CaP ions and neutralized the acid. PAMAM alone failed to achieve dentin remineralization in lactic acid. NACP alone induced slight dentin remineralization in lactic acid (p > 0.1). In contrast, the novel PAMAM + NACP group in the pH4 and CaP-lacking solution completely remineralized the predemineralized dentin, increasing its hardness which approached that of healthy dentin (p > 0.1). In conclusion, dentin remineralization via PAMAM + NACP adhesive in pH4 and CaP-lacking acid was achieved for the first time, when conventional remineralization methods such as PAMAM or NACP did not work. The novel PAMAM + NACP method is promising to increase the longevity of the composite-tooth bond, inhibit caries, remineralize lesions and protect tooth structures, even for patients with dry mouth and an acidic oral environment. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2414-2424, 2018.

Effect of ionizing radiation on properties of restorative materials

OBJECTIVE

To evaluate the effect of ionizing radiation from high energy X-ray on properties of restorative materials.

METHODS

Study materials (3M-ESPE) were: Z250-microhybrid resin-based composite (Filtek Z-250); Z350-nanofilled resin-based composite (Filtek Z-350XT); VIT-resin-modified glass ionomer cement (Vitremer); and KME-conventional glass ionomer cement (Ketac Molar Easymix). Sixty bar-shaped and cylinder-shaped specimens were fabricated from each material. Specimens were light activated (980mW/cm², Radii, SDI) for 60s (3×20s for Z250 and Z350) and 120s (3×40s for VIT) and thirty specimens from each shape were irradiated (IR) with 1.8Gy/day for 39days (total IR=70.2Gy). IR and non-irradiated (NI) specimens were evaluated for flexural strength (σ, n=30) followed by fractography (SEM), diametral tensile strength (DTS, n=30), hardness (H, n=10), surface roughness (R_a, n=10) and chemical composition (n=3). The IR effect on each material property was statistically analyzed using Student's t test (α=0.05). Data from σ and DTS were also analyzed using Weibull statistics.

RESULTS

IR significantly increased the mean σ values of VIT and KME and the mean DTS value of VIT (p<0.05). IR increased R_a and H values for VIT and decreased H value for Z-250 (p<0.05). The remaining materials and properties were not significantly affected by IR (p>0.05). There was no significant change on materials composition after IR.

SIGNIFICANCE

The recommended radiotherapy protocol for head and neck cancer altered some material properties, mainly for glass ionomer cements. Such variations on material properties are not related to chemical composition changes.

Poly(amido amine) and calcium phosphate nanocomposite remineralization of dentin in acidic solution without calcium phosphate ions

OBJECTIVE

Patients with dry mouth often have an acidic oral environment lacking saliva that provides calcium (Ca) and phosphate (P) ions. However, there has been no study on dentin remineralization by placing samples in an acidic solution without Ca and P ions. Previous studies used saliva-like solutions with neutral pH and Ca and P ions. Therefore, the objective of this study was to investigate a novel method of combining poly(amido amine) (PAMAM) with a composite of nanoparticles of amorphous calcium phosphate (NACP) on dentin remineralization in an acidic solution without Ca and P ions for the first time.

METHODS

Demineralized dentin specimens were tested into four groups: (1) dentin control, (2) dentin coated with PAMAM, (3) dentin with NACP nanocomposite, (4) dentin with PAMAM plus NACP composite. Specimens were treated with lactic acid at pH 4 without initial Ca and P ions for 21 days. Acid neutralization and Ca and P ion concentrations were measured. Dentin specimens were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and hardness testing vs. remineralization efficacy.

RESULTS

NACP composite had mechanical properties similar to commercial control composites (p>0.1). NACP composite neutralized acid and released Ca and P ions. PAMAM alone failed to induce dentin remineralization. NACP alone achieved mild remineralization and slightly increased dentin hardness at 21days (p>0.1). In contrast, the PAMAM+NACP nanocomposite method in acid solution without initial Ca and P ions greatly remineralized the pre-demineralized dentin, restoring its hardness to approach that of healthy dentin (p>0.1).

SIGNIFICANCE

Dentin remineralization via PAMAM+NACP in pH 4 acid without initial Ca and P ions was demonstrated for the first time, when conventional methods such as PAMAM did not work. The novel PAMAM+NACP nanocomposite method is promising to protect tooth structures, especially for patients with reduced saliva to inhibit caries.

Postradiation Matrix Metalloproteinase-20 Expression and Its Impact on Dental Micromorphology and Radiation-Related Caries

Recent evidence suggests that head-and-neck radiotherapy (HNRT) increases active forms of matrix metalloproteinase-20 (MMP-20) in human tooth crowns, degrading the dentin-enamel junction (DEJ) and leading to enamel delamination, which is a pivotal step in the formation of radiation-related caries (RRC). Additional participation of enzymatic degradation of organic matrix components in caries progression was attributed to MMP-20 in dentin. Therefore, the current study tested the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes to the enamel and dentin. Thirty-six teeth were studied, including 19 post-HNRT specimens and 17 nonirradiated controls. Optical light microscopy was used to investigate the micromorphological components of the DEJ, dentin-pulp complex components, and carious dentin. The samples were divided into 2 subgroups: nondemineralized ground sections (n = 20) and demineralized histological sections (n = 16). In addition, immunohistochemical analysis using the immunoperoxidase technique was conducted to semiquantitatively assess MMP-20 expression in the DEJ, dentin-pulp complex components, and carious dentin. No apparent damage to the DEJ microstructure or other dentin-pulp complex components was observed and no statistically significant differences were detected in MMP-20 expression (p > 0.05) between the irradiated and control groups. This study rejected the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes. Hence, direct effects of radiation may not be regarded as an independent factor to explain aggressive clinical patterns of RRC.

Restorative dentistry and oral rehabilitation: United Kingdom National Multidisciplinary Guidelines

This is the official guideline endorsed by the specialty associations involved in the care of head and neck cancer patients in the UK and provides recommendations on the pre-treatment oral and dental assessment, during and after treatment and oral rehabilitation. Restorative dentists are core members of the multidisciplinary team treating head and neck cancer patients, involved from the treatment planning phase through to long-term rehabilitation.

Structural Analysis of Enamel in Teeth from Head-and-Neck Cancer Patients Who Underwent Radiotherapy

Objective: To analyze macroscopic, microscopic, and ultrastructural aspects of enamel from head-and-neck cancer patients submitted to radiotherapy. Materials and Methods: Twenty sound extracted permanent molars were used and divided into 2 groups. The experimental group consisted of 10 molars from head-and-neck cancer patients submitted to radiotherapy with total doses that ranged from 50 to 70 Gy. Ten molars from patients who did not receive radiotherapy were matched with experimental-group samples by anatomic tooth group and comprised the control group. To perform a macroscopic analysis, standardized photos of different enamel faces were taken with a camera. Teeth were subjected to longitudinal cuts and hand polished to a final thickness of 0.1 mm. Enamel was analyzed under polarized light microscopy, and optical retardation values of birefringence were calculated in cervical, cusp, and occlusal pit areas. Subsequently, the same enamel areas were analyzed by scanning electron microscopy. Data from optical retardation values were statistically analyzed by 2-way ANOVA and Fisher's test (α < 0.05). Results: No macroscopic differences were observed between the irradiated and control groups. Polarized light microscopy analysis revealed that cervical enamel exhibited darker areas characterized by discrete birefringence patterns compared to the control enamel. Optical retardation values were only significantly different in the cervical enamel of the irradiated and control groups (p < 0.0001). Scanning electron microscopy analysis revealed more evident interprismatic spaces in the cervical and outer cusp enamel of irradiated samples. Conclusions: Head-and-neck radiotherapy reduced optical retardation values of birefringence in cervical enamel, and the interprismatic spaces became more evident.

The wolf in sheep's clothing: Microtomographic aspects of clinically incipient radiation-related caries

Background

Radiation-related caries (RRC) can cause rapid progression, with a high potential for dental destruction affecting mainly cervical and incisal areas. Unlike the injuries that occur in the conventional caries, incipient RRC present in unusual surfaces have difficult diagnosis and classification stages of cavitation.

Material and Methods

Evaluate the radiographic patterns of demineralization of RRC by using micro-CT. Ten teeth with incipient RRC and 10 teeth with incipient conventional caries (control group) matched by anatomic teeth group and caries affected surfaces were evaluated by X-ray microtomography (micro-CT) Skyscan 1174V2 (50Kv, 1.3 megapixel, Kontich, Belgium). Teeth were placed in a standard position for micro-CT (coronal, transaxial and sagittal sections) during images acquisition. Lesions were classified according to the depth of invasion and relationship with enamel, dentin and pulp.

Results

RRC samples presented deeper lesions with higher involvement of enamel and dentin. Control group presented focal and superficial lesions with lower involvement of enamel and dentin.

Conclusions

Incipient RRC present aggressive microtomographic patterns of demineralization when compared to conventional caries, as indicated by deep lesions, regardless of its clinically incipient aspects.

Key words:Head and neck cancer, radiotherapy, microtomography, radiation caries.

Radiation-induced caries as the late effect of radiation therapy in the head and neck region

Overall improvement in the nationwide system of medical services has consequently boosted the number of successfully treated patients who suffer from head and neck cancer. It is essential to effectively prevent development of radiation-induced caries as the late effect of radiation therapy. Incidence and severity of radiationinduced changes within the teeth individually vary depending on the patient's age, actual radiation dose, size of radiation exposure field, patient's general condition and additional risk factors. Inadequately managed treatment of caries may lead to loss of teeth, as well as prove instrumental in tangibly diminishing individual quality of life in patients. Furthermore, the need to have the teeth deemed unyielding or unsuitable for the application of conservative methods of treatment duly extracted is fraught for a patient with an extra hazard of developing osteoradionecrosis (ORN), while also increasing all attendant therapeutic expenditures. The present paper aims to offer some practical insights into currently available methods of preventing likely development of radiation-induced caries.

cGVHD-Related Caries and Its Shared Features with Other 'Dry-Mouth'-Related Caries

<p>Several systemic diseases and their medical treatment may predispose the development of aggressive dental caries. Head and neck radiotherapy, chemotherapy, Sjögren's syndrome and long-standing treatment with drugs that induce hyposalivation are some of these conditions. The aim of this article is to describe the clinical features of five patients who developed chronic graft-versus-host-disease (cGVHD) as a complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and, in spite of close dental follow-up, subsequently developed rampant caries. In these cases, the restorations showed early failure and the caries still progressed until generalized teeth destruction. The majority of the teeth therefore had to be extracted due to advanced dental caries and rapid clinical progression. Herein the term "cGVHD-related caries" is proposed to describe this under-recognized complication of cancer treatment that may evolve in allo-HSCT recipients that develop cGVHD. This condition is poorly recognized in the literature and may represent the final result of the clustering of oral complications in cGVHD patients, including mucositis, oral pain, hyposalivation, taste loss and oral infections, leading to rampant caries due to impaired oral hygiene and increased intake of highly cariogenic food. Consequently, the knowledge of this oral complication should improve the medical and dental management of cGVHD oral manifestations and improve the quality of life of patients with this post allo-HSCT complication.</p>

The Effects of Ionizing Radiation on the Oral Cavity

AIM

The aim of this study is to present a literature review on the effects of the ionizing radiation from radiotherapy treatment on dental tissues.

BACKGROUND

Among the effects of increasing global life expectancy and longevity of the teeth in the oral cavity, increasing rates of neoplastic diseases have been observed. One of the important treatment modalities for head and neck neoplastic diseases is radiotherapy, which uses ionizing radiation as the main mechanism of action. Therefore, it is essential for dentists to be aware of the changes in oral and dental tissues caused by ionizing radiation, and to develop treatment and prevention strategies.

RESULTS

In general, there is still controversy about the effects of ionizing radiation on dental structures. However, qualitative and quantitative changes in saliva and oral microbiota, presence of oral mucositis and radiation-related caries are expected, as they represent the well-known side effects of treatment with ionizing radiation. Points that still remain unclear are the effects of radiotherapy on enamel and dentin, and on their mechanisms of bonding to contemporary adhesive materials.

CONCLUSION

Ionizing radiation has shown important interaction with organic tissues, since more deleterious effects have been shown on the oral mucosa, salivary glands and dentin, than on enamel.

CLINICAL SIGNIFICANCE

With the increasing number of patients with cancer seeking dental treatment before and after head and neck radiotherapy, it is important for dentists to be aware of the effects of ionizing radiation on the oral cavity.

Pigmented ameloblastic fibro-odontoma: clinical, histological, and immunohistochemical profile

Ameloblastic fibro-odontoma (AFO) is a slow-growing, expansive, benign odontogenic tumor, composed of ameloblastic epithelium embedded in an ectomesenchymal stroma resembling dental papilla, containing hard dental tissue in variable degrees of maturation, including enamel, dentin, and sometimes cementum. AFO typically affects the posterior mandible, causing bony expansion. We report a case of pigmented AFO in a 5-year-old boy, comprising clinical and histological features illustrated by immunohistochemistry using a large panel of antibodies, polarized light microscopy and scanning electron microscopy.

Effects of gamma radiation on hard dental tissues of albino rats: investigation by light microscopy

The present work aims at studying the effect of gamma radiation on the hard dental tissues. Eighty adult male albino rats with weights of about 250 g were used. The rats were irradiated at 0.2, 0.5, 1.0, 2.0, 4.0 and 6.0 Gy whole-body gamma doses. The effects on hard dental tissue samples were investigated after 48 h in histological and ground sections using light microscopy. Areas of acid phosphatase activity were detected using tartrate-resistant acid phosphatase (TRAP) stains. Observation of histological sections revealed disturbance in predentin thickness and odontoblastic layer as the irradiation dose increased. In cementum, widened cementocytes lacunae were occasionally detected even with low irradiated doses. On the other hand, relatively homogenous enamel was detected with darkened areas in enamel surface at doses over than 0.5 Gy. TRAP-positive cells were detected on the surface of the dentin of irradiated groups as well as cementum surface. Minimal detectable changes were observed in ground sections.

Optical coherence tomography as an auxiliary tool for the screening of radiation-related caries

OBJECTIVE

The aim of this study was to evaluate the morphological alterations of radiation-related caries using optical coherence tomography.

METHODS

Thirty-six extracted teeth from 11 patients who had undergone radiotherapy were sectioned in the sagittal axis in the center of the carious lesion, and 100 μm thick sections were obtained from each specimen. One sample from each tooth was investigated by an optical coherence tomography (OCT) system, and the results were compared with histological images from polarized light microscopy.

RESULTS

In OCT dentin caries images, the demineralized area appeared as a white region, whereas the translucent zone appeared as a dark area, a similar pattern also seen in coronal caries. In noncavitated enamel lesions clinically observed as brown discoloration, the area of high porosity, and also the dark color, absorbs part of the light, resulting in a dark pattern. Finally, the involvement of dentin-enamel junction (DEJ) or cement-enamel junction (CEJ) could be clearly observed, when present and marked alterations along the CEJ could be noted, as junction continuity loss, gap formation, and mineral loss tissue.

CONCLUSIONS

The OCT technique was able to characterize radiation-related caries, from a morphological point of view. Also demonstrated was its potential benefit for use in the clinical monitoring of radiation-related carious process.

Compliance with fluoride custom trays in irradiated head and neck cancer patients

PURPOSE

The purpose of this study is to assess compliance with fluoride gel custom trays in irradiated head and neck cancer patients.

METHODS AND MATERIALS

One hundred fifty-five consecutive patients on remission following radiation therapy of head and neck cancers were assessed retrospectively for dental care practices prior to radiation and prospectively for long-term compliance with custom trays from November 2009 to January 2010. A five-item questionnaire was filled in by patients in the waiting room, and a 15-item questionnaire by the physician in charge during the corresponding follow-up visit.

RESULTS

Ten percent of patients were edentulous at inclusion. Among dentate patients, 17% had total extractions. With a mean follow-up of 24 months, 19% of patients used custom trays for over a year. Primary stage, age, and tobacco consumption were correlated with compliance with custom trays. More than half of dentate patients developed carious lesions, and 8% had stage 1-3 osteoradionecrosis of the whole population of edentulous and dentate patients.

CONCLUSION

Compliance with custom trays was poor in this series. Specific postirradiation dental care follow-up visits and education have demonstrated their utility in the era of 2D irradiation. We currently advocate an 18-month compliance with custom trays in IMRT patients on the basis of the Parsport trial, after which we assess the quality of salivary recovery before recommending prolonged use or interruption. Data with innovative irradiation techniques are however required.