The effect of radiotherapy on dental hard tissue—a systematic review

The damage and remineralization strategies of dental hard tissues following radiotherapy

OBJECTIVES

This study pursued two main purposes. The first aim was to expound on the microscopic factors of radiation-related caries (RRC). Further, it aimed to compare the remineralization effect of different remineralizing agents on demineralized teeth after radiotherapy.

METHODS

The enamel and dentin samples of bovine teeth were irradiated with different doses of radiation. After analysis of scanning electron microscope (SEM), X-Ray diffraction (XRD), and energy dispersive spectrometer (EDS), the samples irradiated with 50 Gy radiation were selected and divided into the demineralization group, the double distilled water (DDW) group, the Sodium fluoride (NaF) group, the Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group, the NaF + CPP-ACP group, and the Titanium tetrafluoride (TiF4) group. After demineralization, remineralizing agents treatment, and remineralization, the samples were evaluated using SEM, atomic force microscope (AFM), EDS, and transverse microradiography (TMR).

RESULTS

A radiation dose of 30 Gy was sufficient to cause damage to the dentinal tubules, but 70 Gy radiation had little effect on the microstructure of enamel. Additionally, the NaF + CPP-ACP group and the TiF4 group significantly promoted deposit formation, decreased surface roughness, and reduced mineral loss and lesion depth of demineralized enamel and dentin samples after radiation.

CONCLUSIONS

Radiation causes more significant damage to dentin compared to enamel. NaF + CPP-ACP and TiF4 had a promising ability to promote remineralization of irradiated dental hard tissues.

ADVANCES IN KNOWLEDGE

This in vitro study contributes to determining a safer radiation dose range for teeth and identifying the most effective remineralization approach for RRC.

Longitudinal study of the role of salivary proteins on radiation-related caries onset in head and neck cancer patients using 5000 ppm fluoride dentifrice up to one-year post-intensity modulated radiotherapy

OBJECTIVES

Longitudinal assessment of the role of specific proteins on radiotherapy caries (RC) onset in head and neck cancer patients(HNC) up to one-year post-IMRT using a 5000ppm fluoride paste daily.

MATERIALS AND METHODS

Dental status/salivary protein data were obtained from 40 HNC patients pre-IMRT, six months (T1) and 12 months (T2) post-IMRT (ethical approval/consent). DMFT/salivary parameters were quantified, including flow rate, mucin 5B/7, Immunoglobulin A (IgA), cystatin S and α-amylase.

RESULTS

45% patients had at least one carious lesion at T2, a significant reduction in the number of remaining teeth (65% <21), salivary flow rate (< 50%) and, protein secretion (< 0.05) post-IMRT. T1 IgA concentration/secretion rate was associated with RC (p < 0.05). Finally, IgA and total protein concentration obtained at T1 could provide a predictive pattern (AUC 82.3%) for the patients more predisposed to developing RC at T2.

CONCLUSIONS

This study demonstrated the significant association of RC with salivary proteins in HNC patients treated with IMRT, revealing the potential role of salivary proteins in the early diagnosis of RC.

CLINICAL RELEVANCE

This research contributes to revealing salivary proteins association with RC, and its role in early diagnosis. Therefore, this could be the first step towards personalized medicine approaches to improve this group quality-of-life.

A novel method for determining dose distribution on panoramic reconstruction computed tomography images from radiotherapy computed tomography

Purpose

Patients with head and neck cancer (HNC) who undergo dental procedures during radiotherapy (RT) face an increased risk of developing osteoradionecrosis (ORN). Accordingly, new tools must be developed to extract critical information regarding the dose delivered to the teeth and mandible. This article proposes a novel approach for visualizing 3-dimensional planned dose distributions on panoramic reconstruction computed tomography (pCT) images.

Materials and Methods

Four patients with HNC who underwent volumetric modulated arc therapy were included. One patient experienced ORN and required the extraction of teeth after RT. In the study approach, the dental arch curve (DAC) was defined using an open-source platform. Subsequently, pCT images and dose distributions were generated based on the new coordinate system. All teeth and mandibles were delineated on both the original CT and pCT images. To evaluate the consistency of dose metrics, the Mann-Whitney U test and Student t-test were employed.

Results

A total of 61 teeth and 4 mandibles were evaluated. The correlation coefficient between the 2 methods was 0.999, and no statistically significant difference was observed (P>0.05). This method facilitated a straightforward and intuitive understanding of the delivered dose. In 1 patient, ORN corresponded to the region of the root and the gum receiving a high dosage (approximately 70 Gy).

Conclusion

The proposed method particularly benefits dentists involved in the management of patients with HNC. It enables the visualization of a 3-dimensional dose distribution in the teeth and mandible on pCT, enhancing the understanding of the dose delivered during RT.

Evaluation of the shear bond strength of various adhesives on the surface of enamel irradiated with various doses of radiotherapy

INTRODUCTION

We aimed to compare the shear bond strength (SBS) forces on the enamel surface with 2 adhesives after treatment with various radiation doses.

METHODS

A total of 120 premolars were included in the study. The teeth were randomly divided into 5 main groups (n = 24): negative control (without aging), positive control (with aging), 40 Gy, 60 Gy, and 70 Gy radiation. The 40 Gy, 60 Gy, and 70 Gy groups underwent conventional radiotherapy 5 days a week with a dose of 2 Gy each day. After the radiotherapy, all samples except the negative control group were subjected to thermal cycle aging. In all 5 groups, the specimens were divided into 2 subgroups, and half were bonded using 2 adhesives. After bonding, the universal Shimadzu test device was used to analyze the SBS. After the test, the tooth surfaces were examined under a stereomicroscope to determine the adhesive remnant index.

RESULTS

When adhesives were compared, Biofix adhesive's bond strength value was statistically higher in the 40 Gy group than in the Transbond XT group (P = 0.001). The SBS value was higher in all irradiated groups than in nonirradiated groups (P = 0.001). When the adhesive remnant index score was analyzed, no significant difference was found among the groups.

CONCLUSIONS

The SBS increased in irradiated teeth compared with unirradiated teeth, and the SBS values of both adhesives were within the acceptable limits in all radiation groups.

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.

Radiation-induced xerostomia and cariogenic dietary habits

PURPOSE

Despite the availability of various prevention methods, dental caries continue to be diagnosed in patients receiving head and neck radiotherapy (RT). Since conventional approaches do not evaluate posttreatment alterations in dietary behaviors, we aimed to assess the influence of radiation-induced xerostomia on post-RT cariogenic dietary habits in patients.

METHODS

Fifty-seven patients completed the Xerostomia Questionnaire (XQ) and answered questions regarding daily cariogenic food and beverage (CFB) intake, daily tooth brushing, fluoride application, and subjective total taste acuity (STTA). They also underwent evaluations to determine the Simplified Oral Hygiene Index (OHI-S) score, Saxon test score, number of decayed-missing-filled teeth (DMFT), and proportion of DMFT to the test teeth (DMFT rate). Clinical records were searched for information regarding RT modalities, including the median of the mean dose to the parotid glands, days after the completion of RT, submandibular gland resection, whole-neck irradiation, and the DMFT value and rate before RT. The patients were divided into low and high XQ score groups based on the median XQ score of 47.5 for the two sample tests. Univariable and multivariable regression analyses were used to identify independent factors for frequent CFB intake.

RESULTS

Higher XQ scores were associated with a significantly greater frequency of CFB intake (p = 0.028*). Regression analysis also identified a higher XQ score (p = 0.017*) as an independent risk factor for frequent CFB intake.

CONCLUSION

Radiation-induced xerostomia increased the frequency of CFB intake.

Antibacterial, antibiofilm and anticaries effect of BioXtra® mouthrinse for head and neck cancer (HNC) patients under a microcosm biofilm model

BACKGROUND AND PURPOSE

Considering the lack of studies investigating salivary substitutes to control post-radiation caries for patients with head and neck cancer (HNC), this study aimed to evaluate the antibacterial, antibiofilm, and anticaries effects of BioXtra® on the microcosm biofilm formed on different enamel types (non-irradiated and irradiated) and from distinct saliva sources (control and HNC patients).

MATERIALS AND METHODS

Non-irradiated and irradiated enamel specimens were treated with BioXtra®, phosphate-buffered-saline (PBS; negative control), or 0.12% chlorhexidine (CHX; positive control) for 1 min. Biofilm was produced from human saliva (healthy participants with normal salivary flow for the control group or irradiated HNC patients with hyposalivation for the HNC group), mixed with McBain saliva, under 0.2% sucrose exposure, daily submitted to the treatments (1 min), for 5 days. Bacterial metabolic activity, biofilm viability, CFU counting, and enamel demineralization were determined.

RESULTS

BioXtra® significantly reduced the bacterial metabolic activity for both enamel types and the inoculum sources, being more effective for the irradiated enamel or for the saliva from the control group. Similarly, BioXtra® significantly reduced the biofilm viability, the CFU for total microorganisms, mutans streptococci, and lactobacilli, and was able to significantly reduce the mineral loss and the lesion depth compared to PBS. CHX was an effective treatment to significantly reduce all parameters, performing better than BioXtra® and reinforcing its reliable efficiency as a positive control.

CONCLUSION

Regardless of the enamel type and the inoculum source, BioXtra® presented antibacterial, antibiofilm, and anticaries effects under this experimental model, which should be confirmed in further clinical studies.

Does radiation therapy affect adhesion of tricalcium silicate cements to root dentin?

OBJECTIVE

This study aimed to analyze the effect of irradiation on the push-out bond strength of mineral trioxide aggregate (MTA) and Biodentine to radicular dentin.

METHODOLOGY

A total of 60 extracted mature human teeth with single root canals were categorized into two groups (irradiated and non-irradiated) (n=30). Each group was further divided into two sub-groups based on cements used (Biodentine and MTA). Then, a cumulative radiation dose of 60 Gy was divided into 30 fractions (two Gy for every fraction) and administered for five successive days per week over six weeks. Obturation was then performed using MTA and Biodentine. Afterwards, 1.5 mm thick horizontal sections were procured from the middle one-third of all the specimens and then subjected to push-out bond test. Results were analyzed using one-way analysis of variance with post-hoc Tukey's test.

RESULTS

The bond strength of Biodentine and MTA to irradiated teeth was lower than non-irradiated teeth. Highest push-out bond strength was observed in non-irradiated specimens filled with Biodentine (p=0), followed by irradiated specimens filled with Biodentine (p=0); non-irradiated specimens filled with MTA (p=0); and irradiated specimens filled with MTA (p=0.9).

CONCLUSION

The push-out bond strength of Biodentine and MTA to root canal dentin decreased significantly post irradiation.

Impact of Irradiation on the Adhesive Performance of Resin-Based Dental Biomaterials: A Systematic Review of Laboratory Studies

Head and neck cancers are a significant global health burden, with radiation therapy being a frequently utilized treatment. The aim of this systematic review was to provide a critical appraisal of laboratory studies that assessed the effect of irradiation on the adhesive performance of resin-based biomaterials. The analysis included 23 laboratory studies obtained from five databases, with most studies using human enamel, dentin, or both, and bonding procedures involving the fabrication of direct restorations, standardized specimens, bonding of orthodontic brackets, and luting of endodontic fiber posts. The protocols used for irradiation varied, with most studies exposing specimens made from extracted teeth to irradiation using cabinet irradiators to simulate treatment of head and neck cancer. The findings indicate that irradiation reduces the bond strength of dental adhesives and resin-based composites on flat, ground enamel and dentin specimens, with different adhesives and timing of irradiation having a significant impact on adhesive performance. Irradiation also increased microleakage in most studies. The effect of irradiation on marginal adaptation of direct resin-based composite restorations was inconclusive. This systematic review indicates that irradiation has detrimental effects on the adhesive performance of resin-based biomaterials and highlights the need for further clinical and laboratory studies evaluating the performance of adhesive materials and approaches to improve it.

Influence of Ionizing Radiation on Fluoride-Releasing Dental Restorative Materials

This study aimed to investigate the effects of radiotherapy on the mechanical, chemical, and surface properties of two recently introduced restorative dental materials (a glass hybrid and an alkasite), while two conventional restorative materials served as references. Material specimens of the experimental groups (irradiated) were compared to the specimens of the control groups that underwent the same preparation procedure but without irradiation. The experimental groups of restorative material specimens were irradiated with a total of 70 Gy over 35 days (2 Gy/day × 35 days), while the control groups received no treatment. The following properties were evaluated: surface microhardness (Vickers), surface roughness, color change, flexural strength, flexural modulus, material reliability, and infrared spectra. For the experimental groups, measurements were performed 24 h after specimen preparation, i.e., before radiotherapy and after the completion of the irradiation protocol. For the control groups, measurements were performed after the corresponding periods of no treatment. A statistically significant increase in microhardness (p = 0.001-0.004) and surface roughness (p = 0.013) was observed as a result of material aging/maturation in both the control and experimental groups. However, the only statistically significant difference between the control and experimental groups was observed in the discoloration of the conventional reference material (p < 0.001). In conclusion, no statistically significant negative effects of a therapeutic dose of radiotherapy on any of the tested properties of the alkasite and glass hybrid materials were observed, whereas only a minor negative effect of radiotherapy in terms of discoloration was found for a conventional resin composite that was used as a reference material.

The dose limits of teeth protection for patients with nasopharyngeal carcinoma undergoing radiotherapy based on the early oral health-related quality of life

Radiation-related teeth damage is a common complication in nasopharyngeal carcinoma (NPC) patients undergoing radiotherapy (RT) that seriously affects their oral health-related quality of life (OHRQoL). However, few studies have focused on protecting teeth function. This study aimed to calculate dental dose limits based on OHRQoL. Analysis was performed on 96 NPC patients who received RT (all received routine pre-radiotherapy dental interventions in our department). Based on the General Oral Health Assessment Index (GOHAI), OHRQoL was assigned into poor (<46) and good condition groups (≥46). The binary logistic regression analysis model was used for single-factor and multivariate analyses to identify the independent factors affecting OHRQoL. The cut-off value of dose received by teeth was obtained by drawing a receiver operating characteristic curve. NPC patients experienced a decline in OHRQoL following RT (P < 0.05). Univariate analysis of GOHAI revealed that the average dose of maxillary anterior teeth, the average dose received by the oral cavity, tumor volume (GTVnx), and liking of the sweet food all affected GOHAI (P < 0.05). Multivariate analysis indicated that the average dose of maxillary anterior teeth and liking sweet food were independent factors that influenced the OHRQoL of NPC patients with RT. When the average dose received by maxillary anterior teeth is greater than 28.78 Gy, and there is a tendency in sweet food, the OHRQoL will deteriorate. NPC patients who received RT had a better OHRQoL if the average dose to maxillary anterior teeth was limited to less than 28.78 Gy and the intake of high-sugar foods was reduced.

Impact of radiotherapy on the morphological and compositional structure of intra-radicular dentin

Considering the side effects in the oral cavity and dental structures of radiotherapy (RDT) for head and neck cancer, this study aimed to evaluate the effects of RDT on the root dentin concerning the obliteration of dentinal tubules, the inorganic composition of intra-radicular dentin, and the integrity of collagen fibers. Thirty human canines were selected from a biobank and randomly divided into two groups (n=15). The samples were sectioned buccolingually, and a hemisection was used for structural analysis by scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDS). Low-vacuum SEM images were obtained at 2000-x magnification to observe the obliteration of the dentinal tubules. Moreover, compositional evaluation was performed using EDS. After RDT, the SEM and EDS analyses were repeated using the same methodology. RDT was applied fractionally at 2 Gy per day, 5 days per week, for 7 weeks, resulting in a total dose of 70 Gy. The collagen integrity of the irradiated and non-irradiated samples was analyzed using Masson's trichrome and picrosirius red staining polarization microscopy. Samples subjected to RDT exhibited dentinal tubule obliteration (p < 0.001); low integrity of type I and III collagen fibers (p < 0.05); compositional reduction of calcium (p = 0.012), phosphorus (p = 0.001), and magnesium (p < 0.001); an increased Ca/P ratio (p < 0.001). RDT affects the structure of dentinal tubules, the inorganic composition of intra-radicular dentin, and the collagen fiber integrity in the root dentin, which may interfere with the effectiveness and durability of dental procedures.

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.

Push-out bond strength of fiber posts to irradiated and non-irradiated intraradicular dentin

OBJECTIVES

The aim of this study is to evaluate the influence of ionizing radiotherapy on the resin-dentin interface in endodontically treated teeth restored with fiber posts using a dual-cure resin cement performed with the etch-and-rinse (ER) and self-etch (SE) approaches in terms of push-out bond strength (MPa), and to analyze the post/cement/dentin interface using scanning electron microscopy (SEM).

MATERIALS AND METHODS

Seventy-six single-rooted human teeth were used and randomly assigned into two main groups (n = 38): one non-irradiated group (NoRad) and one group subjected to a cumulative radiation dose of 60 Gy (Rad). All root canals were instrumented and were further subdivided into two subgroups (n = 19) following the adhesive approach: ER (RadER; NoRadER) and SE (RadSE; NoRadSE) used for fiber post luting with the universal adhesive and dual cure resin cement. Each root was sectioned perpendicularly to its long axis and sections from the middle third of the roots were chosen for SEM analysis and push-out bond strength test. Two-way ANOVA with post hoc Tukey tests and a dummy variable linear regression analysis were used for data analysis.

RESULTS

Regardless of the adhesive approach, push-out bond strength in irradiated teeth resulted in significantly lower values than non-irradiated teeth (p = 0.0001). There were no significant differences between the ER and SE approaches in non-irradiated teeth (p = 0.955), whereas the ER approach showed significantly higher bond strengths than the SE approach in irradiated teeth (p = 0.0001).

CONCLUSIONS

Ionizing radiotherapy resulted in dentin structure disruption and negatively affected the push-out bond strength of fiber posts to intraradicular dentin. The reduction in bond strength was also more significant with the SE approach than with the ER approach.

CLINICAL RELEVANCE

The alterations resulting from root dentin irradiation seem to influence adhesive systems bond strength to dentin, as these changes contribute to lower push-out bond strength in irradiated groups before fiber post luting. Thus, clinicians should prepare patients with a reasonable restorative treatment plan prior to radiotherapy and simultaneously initiate a preventive program during radiotherapy.

Effect of experimental and commercial artificial saliva formulations on the activity and viability of microcosm biofilm and on enamel demineralization for irradiated patients with head and neck cancer (HNC)

The effect of different artificial saliva formulations on biofilm activity and viability, and on enamel demineralization for head and neck cancer (HNC) patients was evaluated. Irradiated enamel samples were treated (1 min) with BioXtra® or with experimental formulations containing carboxymethylcellulose plus inorganic constituents alone (AS) or containing 0.1 mg mL^-1 CaneCPI-5 (AS + Cane), 1.0 mg mL^-1 hemoglobin (AS + Hb) or combination of both (AS + Cane + Hb). Phosphate-buffered-saline and chlorhexidine (0.12%) were negative and positive control, respectively. Biofilm was produced from the saliva of five male HNC patients, under 0.2% sucrose exposure for 5 days, and daily treated with the formulations (1 min). No significant effects were observed for the different experimental treatments. BioXtra^® significantly reduced lactobacilli, demonstrating antibacterial potential for this group. Chlorhexidine was an effective treatment to significantly reduce all parameters, being an important antimicrobial and anticaries agent. Future in vitro studies must be performed using a new approach for the design of the experimental formulations.

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.

Effect of Diode Laser and Remineralizing Agents on Microstructure and Surface Microhardness of Therapeutic Gamma-Irradiated Primary Teeth Enamel

BACKGROUND: Radiation caries is a serious complication to head and neck cancer (HNC) radiotherapy, for which the primary teeth are more susceptible to be affected. Preventive protocols are recommended to enhance dental structure resistance against the direct effects of radiotherapy. AIM: The aim of the study is to evaluate the effect of diode laser and two types of remineralizing agents on the microhardness of the primary teeth enamel and examine microstructural alterations. METHODS: Twenty primary molars were sectioned into two halves in a mesiodistal direction, to obtain 40 specimens, which were then randomly allocated into five groups. Group 1 (Control Negative) n = 5 was not subjected to any treatment or radiation. Group 2 (Control positive) n = 5 was gamma irradiated with a dose of 60 Gray. For Groups 3, 4, and 5, specimens were divided into two subgroups: A and B (n = 5/subgroup). Subgroups A were gamma irradiated, then exposed to different surface treatments: 3A:10% nano-hydroxyapatite (nHA) paste, 4A: 5% sodium fluoride varnish (FV), and 5A: diode laser 980 nm. Subgroups B were exposed to surface treatments (3B: 10% nHA, 4 B: 5% FV, and 5B: diode laser 980 nm), then gamma irradiated. Surface micromorphology and microhardness were examined using environmental scanning electron microscope (ESEM), and Vickers microhardness tester, respectively. RESULTS: Group 2 (G) specimens possessed the lowest mean microhardness, while nHA-G (3B), G-Fl (4A), and L-G (5B) had significantly higher values. ESEM analysis showed an alteration in Group G and the obliteration of enamel micropores with remineralizing agents. The melting and fusion of enamel in laser subgroups were also observed. CONCLUSIONS: The findings indicated that using FV, nHA, or diode laser increased microhardness and maintained the integrity of the enamel microstructure. Therefore, applying preventive strategies should be considered in HNC radiotherapy.

An Overview of Clinical Oncology and Impact on Oral Health

As the incidence of cancer continues to increase, so too will the use of various forms of cancer therapeutics and their associated oral and dental complications. Although many of the acute and chronic oral toxicities of cancer therapy are largely unavoidable, appropriate and timely management of these complications has the potential to alleviate morbidity and improve outcomes. Undoubtedly, the substantial short- and long-term impacts of cancer therapy on the health of the oral cavity requires increased awareness, prevention, and treatment by multidisciplinary healthcare teams consisting of medical oncologists, dentists, and other oral healthcare specialists. This mini review provides a brief purview of the current state of clinical oncology and its impact on oral health. The topics introduced here will be further investigated throughout the remainder of the “Oral Complications in Cancer Patients” mini-review series.

Effects of irradiation, restoration and crown fracture type on the maximum load to fracture traumatized incisors: An ex vivo study

BACKGROUND/AIMS

Radiotherapy makes teeth prone to tooth fractures. However, the relationship between radiotherapy and maximum load to fracture teeth that suffered a crown fracture is not fully understood. The aim of this study was to evaluate the influence of fracture type, radiation dose, fracture time, and their interactions on maximum load to fracture irradiated teeth.

MATERIAL AND METHODS

A total of 140 permanent incisors were divided into two fracture type groups (uncomplicated and complicated) each of which included seven radiation dose subgroups (0, 10, 20, 30, 40, 50, and 60). The test groups were exposed to high-energy X-ray at 2 Gy/day, 5 days/week for a total dose of 10-60 Gy. Control groups were not irradiated. The load where the specimen started to break was obtained two different times. The 1st fracture was performed after radiation therapy, and the 2nd fracture was performed after the restoration of these samples.

RESULTS

Fracture type had no effect on the maximum load to fracture. In contrast, the maximum load to fracture teeth decreased with increasing radiation doses. Maximum load to fracture the restored teeth was lower than the 1st fracture results. The general linear model procedure revealed a significant interaction between radiation dose and fracture time. Similarly, there was a significant interaction between the fracture type, radiotherapy dose, and fracture time. Maximum load values of teeth with complicated crown fractures restored with fiber posts and composite were not affected by radiation.

CONCLUSION

Teeth that have been subjected to radiotherapy have an increased risk of fracture during dental trauma. However, restoration of the irradiated teeth with fiber posts and composite resin did not affect the maximum load required to fracture them.

Effect of Preirradiation Fluoride Treatment on the Physical Properties of Dentin

Objective. To determine the effects of preirradiation fluoride treatments on the Knoop hardness of dentin. Materials and Methods. Human posterior teeth mounted into acrylic resin molds were polished with silicon carbide (SiC) abrasives and 3-micron diamond paste. The Knoop hardness of dentin was measured with a Leco hardness instrument. The teeth were divided into groups of ten teeth per group as follows: no treatment (control), treatment with silver diamine fluoride (SDF), MI varnish (MI), and cavity shield (CS). The teeth were exposed to 2 Gy of daily radiation for six weeks using an X-Rad 320ix biological irradiator. Hardness was measured weekly, before, during, and after irradiation. The teeth were stored in artificial saliva at 37oC between radiation treatments. Results. In preirradiation dentin, a Knoop hardness value of 58.8 (14.1) KHN was obtained. Treatment with SDF significantly increased KHN before irradiation. Immediately after radiation treatment, hardness was significantly reduced in all experimental groups. Postirradiation fluoride treatments increased the hardness of dentin to varying degrees. Conclusions. Preirradiation fluoride treatment does not provide protection from decreases in the hardness of dentin. Treatment of teeth with fluoride formulations after radiation progressively restores the hardness of dentin to different degrees.

Direct Induced Effects of Standard and Modified Radiotherapy Protocol on Surface Structure of Hard Dental Tissue

Introduction

Radiotherapy is used to treat neo plasmatic lesions and the common side effects of this process are pain, swelling and sensitivity of mucous membranes in domain of radiation, reduced salivation, caries, and periodontal disease and, in total, low life quality. The purpose of this research was to estimate the outcome of direct irradiation on physical and surface characteristics of hard dental tissues.

Materials and methods

Twenty, caries free third molars were involved in the research. Prior to different submission protocols, tooth halves were randomly assigned to subject and control groups by using a draw method. The first group (n=20) was submitted to conventional irradiation protocol (2 Gy for 35 days), second group (n=20) was submitted to one powerful, exploratory dose of 70 Gy. Each sample served as its own control. Radiation was performed with a linear accelerator radiotherapy unit. The surface microhardness and roughness were measured at the beginning (initially), and upon completion of irradiation procedure. The average change in microhardness and roughness after different treatments was compared by t-test for independent samples. Normality was tested by the Shapiro-Wilk test.

Results

Significant differences were found after the standard radiation protocol and the exploratory dose of 70 Gy, with decreased mean microhardness and increased mean roughness (p<0.001) of both hard dental tissues. Enamel and dentin surface microhardness and roughness did not vary notably with regards to different irradiation protocols.

Conclusion

Head and neck conventional irradiation protocol leads to possible breakdown of enamel and dentin with reduced microhardness and increased surface roughness regardless of used irradiation protocol.

Review of Cracked Tooth Syndrome: Etiology, Diagnosis, Management, and Prevention

Cracked tooth syndrome refers to a series of symptoms caused by cracked teeth. This article reviews the current literature on cracked tooth syndrome from four aspects, etiology, diagnosis, management, and prevention, to provide readers integrated information about this. The article begins with an introduction to the odontiatrogenic factors and then covers the noniatrogenic factors that induce cracked tooth syndrome. While the former discusses inappropriate root canal therapy and improper restorative procedures, the latter covers the topics such as the developmental and functional status of cracked tooth syndrome. This is then followed by the description of common clinical diagnosis methods, the prospects of new technologies, and summaries of current clinical management methods, including immediate management and direct and indirect restoration. In the final section, preventive methods and their importance are proposed, with the aim of educating the common population.

Sequential drug delivery by injectable macroporous hydrogels for combined photodynamic-chemotherapy

With hollow mesoporous silica (hMSN) and injectable macroporous hydrogel (Gel) used as the internal and external drug-loading material respectively, a sequential drug delivery system DOX-CA4P@Gel was constructed, in which combretastatin A4 phosphate (CA4P) and doxorubicin (DOX) were both loaded. The anti-angiogenic drug, CA4P was initially released due to the degradation of Gel, followed by the anti-cell proliferative drug, DOX, released from hMSN in tumor microenvironment. Results showed that CA4P was mainly released at the early stage. At 48 h, CA4P release reached 71.08%, while DOX was only 24.39%. At 144 h, CA4P was 78.20%, while DOX release significantly increased to 61.60%, showing an obvious sequential release behavior. Photodynamic properties of porphyrin endow hydrogel (ϕΔ(Gel) = 0.91) with enhanced tumor therapy effect. In vitro and in vivo experiments showed that dual drugs treated groups have better tumor inhibition than solo drug under near infrared laser irradiation, indicating the effectivity of combined photodynamic-chemotherapy.

Direct Radiotherapy-Induced Effects on Dental Hard Tissue in Combination With Bleaching Procedure

Introduction: The aim of this study was to evaluate the effects of radiation and tooth bleaching on the physical and morphological properties of enamel and dentin on permanent teeth.

Materials and Methods: Eighty fresh, non-carious third molars were used in this study. Before cutting the crown in half, the teeth samples were randomly allocated to treatment and control groups by using a lottery method. The first group (n = 20) underwent standard radiation protocol (2 Gy/fraction/day, 5 days/week) with bleaching treatment afterward using 16% carbamide peroxide gel, the second group (n = 20) underwent standard radiation protocol with afterward bleaching treatment using 38% hydrogen peroxide, the third group (n = 20) underwent a short, one strong, experimental dose of 70 Gy with afterward bleaching treatment using 16% carbamide peroxide gel, and the fourth group (n = 20) underwent one strong, experimental dose of 70 Gy with afterward bleaching treatment using 38% hydrogen peroxide gel. Groups 5–8 (n = 20) served as control as they underwent only bleaching treatment. Vickers microhardness and surface roughness were performed before (initial) and after irradiation and before bleaching or after only bleaching. The effects of irradiation and bleaching on microhardness (or roughness) of enamel and dentin were analyzed in the repeated-measures ANOVA model.

Results: Enamel microhardness after experimental single 70-Gy irradiation or after standard radiation protocol and bleaching with 16 or 38% gel was not statistically significant from microhardness in the control group (p &gt; 0.05). There was a statistically significantly greater reduction in the average microhardness of enamel and dentin during bleaching with 38% gel compared to 16% for both radiation protocols (p &lt; 0.001). After experimental 70-Gy irradiation and bleaching, a 16% statistically significant increase in surface roughness was found for enamel (p = 0.006) and dentin (p = 0.018), while this was not recorded for 38% gel. There was a statistically significantly greater increase in the average roughness of enamel and dentin during bleaching with 38% gel compared to 16% (p &lt; 0.001) for both radiation protocols.

Conclusions: Directly induced radiation leads to potential damage of hard dental tissues, which can be further damaged by additional bleaching. If teeth whitening is necessary after irradiation, it is suggested to use lower concentrations of whitening gels.

Manifestation and Mechanisms of Abnormal Mineralization in Teeth

Tooth biomineralization is a dynamic and complicated process influenced by local and systemic factors. Abnormal mineralization in teeth occurs when factors related to physiologic mineralization are altered during tooth formation and after tooth maturation, resulting in microscopic and macroscopic manifestations. The present Review provides timely information on the mechanisms and structural alterations of different forms of pathological tooth mineralization. A comprehensive study of these alterations benefits diagnosis and biomimetic treatment of abnormal mineralization in patients.

Impact of radiation on tooth loss in patients with head and neck cancer: a retrospective dosimetric-based study

OBJECTIVE

To characterize the dental adverse events after head and neck radiation therapy (HNRT) and to investigate the impact of regional radiation dose upon tooth loss outcomes.

STUDY DESIGN

A retrospective dosimetric-based analysis was conducted to assess dental events affecting post-HNRT extracted teeth and the impact of 3 different radiation doses (<30 Gy, 30-60 Gy, and >60 Gy) upon tooth loss. In addition, post-HNRT extractions outcomes and mean parotid glands dosimetry and salivary changes were analyzed.

RESULTS

Sixty-six patients who underwent HNRT were included in the analysis. Radiation caries was the most frequent (67.8%) post-HNRT dental adverse event, and maxillary molars ipsilateral to the tumor were lost earlier compared with the others (P < .001). The odds ratio for post-HNRT tooth extraction risk was approximately 3-fold higher for teeth exposed to >60 Gy (confidence interval, 1.56-5.35; P < .001), followed by an increased risk of delayed healing and osteoradionecrosis (ORN) in sites receiving doses above 50 Gy.

CONCLUSIONS

Radiation caries was the major cause of dental extractions after HNRT, and the dosimetric analysis suggested that a high dose of radiation may negatively impact the dentition of survivors of head and neck cancer, increasing the risk of tooth loss and ORN.

Dosimetric Parameters Predicting Tooth Loss after Carbon Ion Radiotherapy for Head and Neck Tumors

Background: Tooth loss reduces quality of life; however, little is known about tooth loss caused by carbon ion radiotherapy (CIRT). Here, we aimed to elucidate the incidence of tooth loss post-CIRT for head and neck tumors and to identify risk-predictive dosimetric parameters. Methods: This study enrolled 14 patients (i.e., 171 teeth in total) with head and neck non-squamous cell carcinoma. All patients received CIRT comprised of 57.6 or 64.0 Gy (relative biological effectiveness, RBE) in 16 fractions. Dose–volume analysis of the teeth was performed using receiver operating characteristic (ROC) curve analysis with VX (i.e., the volume irradiated with X Gy (RBE)). Results: The median follow-up period was 69.1 months. The median time of tooth loss was 38.6 months. The 5 year cumulative incidence of tooth loss was 13.3%. The volume of irradiated teeth was significantly greater for the lost teeth than for the remaining teeth throughout the dose range. Using the cut-offs calculated from ROC curve analysis, V30–V60 showed high accuracy (i.e., >94%) for predicting tooth loss, with V50 being the most accurate (cut-off, 58.1%; accuracy, 0.95). Conclusions: This is the first report to examine the incidence of tooth loss post-CIRT and to identify risk-predictive dosimetric parameters.

Awareness of the risk of radiation-related caries in patients with head and neck cancer: A survey of physicians, dentists, and patients

OBJECTIVES

Radiation-related caries (RRC) is one of the most aggressive complications of radiotherapy (RT) in survivors of head and neck cancer (HNC). Lack of RRC awareness may contribute to the occurrence of this oral cavity complication. RRC may be considered a "forgotten oral complication" by patients with HNC, oncologists, and dentists. The present study aimed to assess the level of awareness of RRC among physicians, dentists, and patients.

STUDY DESIGN

Physicians (group 1, G1), dentists (group 2, G2), and patients with HNC undergoing RT (group 3, G3) answered questionnaires concerning their awareness of RRC. Physicians (G1) were divided into group 1A (oncological experience) and group 1B (general physicians/other specialties). Dentists (G2) were divided into group 2A (oncological experience) and group 2B (general dentists/other specialties). Personalized questionnaires were designed for each group.

RESULTS

Recruitment was as follows: physicians (n = 124): 1A (n = 64), 1B (n = 60); dentists: (n = 280), 2A (n = 160), 2B (n = 120). In addition, 58 patients answered the questionnaire. In terms of RRC awareness, 46.77% of physicians, 81.78% of dentists, and 24.13% of patients had some knowledge of the problem.

CONCLUSION

Patient awareness of RRC was poor. The heterogeneity of answers among physicians and dentists suggests an opportunity to improve patient education and prevention of this serious oral complication of RT.

Conformational and constitutional analysis of dental caries following radiotherapy for head and neck cancer

Background

This study aimed to investigate the morphology and chemical composition of dental caries related to ionizing radiation (DCIR), an aggressive and progressive disease that affects dental hard tissues.

Materials and methods

Eight human teeth with DCIR were paired with sixteen control teeth (8 teeth with conventional caries and 8 without caries) and included in this study. An analysis of the morphology of the lesions was performed using the following techniques: periapical radiography, cone beam computed tomography, computed microtomography, and scanning electron microscopy. The chemical composition was assessed using X-ray dispersive spectroscopy.

Results

There was more demineralization in DCIR lesions when compared to conventional dental caries, even though there was no cavitation in the cervical region of the teeth. The superficial roughness and topography of DCIR lesions were similar to those of healthy teeth. On the other hand, lesions of conventional dental caries showed greater surface and topographic irregularity when compared to DCIR and healthy teeth (p = 0.001). Calcium (Ca) and phosphorus (P) levels were lower in DCIR lesions when compared to controls. However, higher levels of carbon (C) have been observed in DCIR lesions. There was a greater loss of the mineral matrix in DCIR followed by conventional caries. The reduction in the mineral matrix (Ca and P) was compatible with the imaging patterns observed in teeth with DCIR and conventional caries.

Conclusion

Despite their rapid evolution, DCIR presents an irregular, apparently intact surface with significant changes in the amount of Ca, P, and C.

Late radiation effects in survivors of head and neck cancer: State of the science

Head and neck squamous cell carcinoma is one of the most common neoplasms. Radiotherapy (RT) plays an essential role in the management of such cases. Despite advances in the technique, hyposalivation, xerostomia, dysphagia, trismus, radiation caries, and osteoradionecrosis remain significant late complications of RT. The aim of this narrative review was to summarize and update the main findings related to late side effects of radiotherapy in survivors of head and neck cancer (HNC). Such effects limit the ability to speak, ingest food and medications, and breathe and also exert a negative impact on social well-being and quality of life. This review highlights research in the field for both researchers and clinicians, assisting in the prevention and management of these adverse conditions. The findings can contribute to improving preventive management and multidisciplinary interventions for HNC patients.

ODONTOLOGICAL EFFECTS OF IONIZING RADIATION (review)

BACKGROUND

Odontological effects of ionizing radiation (IR) as a result of radiotherapy, the consequences of accidents at nuclear power plants and industry, individual occupational exposure, etc. deserve significant attention interns of radiation medicine and radiation safety.

OBJECTIVE

to analyze and summarize clinical and experimental data on the odontological radiation effects.

MATERIALS AND METHODS

OBJECT

the pathological changes in the hard tissues of teeth, pulp, periodontium, mucousmembranes of the mouth and jaws due to exposure to IR.

METHOD

search in the PubMed / MEDLINE, Google Scholarabstract medical and biological databases, scientific libraries of the relevant sources of scientific information.

RESULTS

Radiobiological effects of IR due to its direct and indirect action are manifested throughout the period ofodontogenesis and formation of the facial skeleton. Experimental and clinical data (in children and adults) indicatethe increased risk of dental caries, reduction of pain threshold and vascularization of tooth pulp along with its fibrosis and atrophy, periodontal dysfunction, which predispose to a high probability of tooth loss. Abnormalities in theactivity of osteoblasts and cementoblasts of dental periosteum and osteoblasts of alveolar process in combinationwith circulatory disorders due to endothelial cell death, hyalinization, thrombosis and vascular obliteration increasethe risk of jaw osteoradionecrosis. Children who have undergone a prenatal exposure to IR as a result of theChornobyl NPP accident have a premature change of teeth. Deterioration of periodontal tissues and early development of acute and complicated dental caries are typical for children and adults affected by the Chornobyl disaster.

CONCLUSIONS

Summarized data on the effects of radiation exposure under different conditions on teeth primordia(i.e. immature teeth), their formation and eruption in experimental and clinical settings, as well as on the odontological radiation effects in adults are summarized. Condition of the teeth in the Chornobyl NPP accident survivorsis described. Understanding and taking into account the radiobiological odontological effects is necessary in thelight of planning, preparing, and conducting local radiation therapy and developing the standards of radiation safety and measures to protect professionals and the public in the event of possible radiation accidents at the nuclearpower plants and industry facilities.

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.

Demineralization of tooth enamel following radiation therapy; An in vitro microstructure and microhardness analysis

Objective

The objective of this study is to evaluate the effects of radiotherapy doses on mineral density and percentage mineral volume of human permanent tooth enamel.

Materials and Methods

Synchrotron radiation Xray microcomputed tomography (SRμCT) and microhardness testing were carried out on 8 and 20 tooth samples, respectively. Enamel mineral density was derived from SRμCT technique using ImageJ software. Microhardness samples were subjected to Vickers indentations followed by calculation of microhardness and percentage mineral volume values using respective mathematical measures. Data were analyzed using paired t-test at a significance level of 5%. Qualitative analysis of the enamel microstructure was done with two-dimensional projection images and scanned electron micrographs using μCT and field emission scanning electron microscopy, respectively.

Results

Vickers microhardness and SRμCT techniques showed a decrease in microhardness and an increase in mineral density, respectively, in postirradiated samples. These changes were related to mineral density variation and alteration of hydroxyapatite crystal lattice in enamel surface. Enamel microstructure showed key features such as microporosities and loss of smooth homogeneous surface. These indicate tribological loss and delamination of enamel which might lead to radiation caries.

Conclusions

Tooth surface loss might be a major contributing factor for radiation caries in head-and-neck cancer patients prescribed to radiotherapy. Such direct effects of radiotherapy cause enamel abrasion, delamination, and damage to the dentinoenamel junction. Suitable measures should, therefore, be worked out to protect nontarget oral tissues such as teeth while delivering effective dosages to target regions.

Short-term and long-term unstimulated saliva flow following unilateral vs bilateral radiotherapy for oropharyngeal carcinoma

BACKGROUND

We aimed to compare unstimulated saliva flow using 3-minute modified Schirmer test (MST) following bilateral vs unilateral radiotherapy (RT) in oropharyngeal carcinoma (OPC).

METHODS

We reviewed OPC patients treated with definitive intensity-modulated radiation therapy (IMRT) between 2011 and 2017. MST was measured at baseline, 1-/6-/12-/24-month post-RT. MST values were compared between bilateral-RT vs unilateral-RT groups. Multivariable logistic regression analysis (MVA) identified predictors of hyposalivation (MST < 25 mm).

RESULTS

Total 498 bilateral-RT and 36 unilateral-RT patients were eligible. The MST values at 1-/6-/12-/24-month post-RT were all significantly reduced from baseline for the entire cohort. Baseline unilateral-RT and bilateral-RT MST values (in mm) were similar (P = .2), but much higher for unilateral-RT 1-month (mean: 19.1 vs 13.0, P = .03), 6-month (20.5 vs 9.3, P < .001), 12-month (20.1 vs 11.9, P < .01), and 24-month post-RT (22.2 vs 13.9, P = .04). MVA confirmed that unilateral RT reduced the likelihood of hyposalivation vs bilateral RT (OR 2.36, P = .006).

CONCLUSION

Unilateral RT reduces unstimulated salivary flow in OPC patients.

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.

Results of a randomized controlled phase III trial: efficacy of polyphenol-containing cystus® tea mouthwash solution for the reduction of mucositis in head and neck cancer patients undergoing external beam radiotherapy

PURPOSE

To determine the effect of Cystus® tea (Naturprodukte Dr. Pandalis GmbH & Co. KG) as mouthwash compared to sage tea on oral mucositis in patients undergoing radio(chemo)therapy for head and neck cancer.

METHODS

In this randomized, prospective phase III study, 60 head and neck cancer patients with primary or postoperative radio(chemo)therapy were included between 04/2012 and 06/2014. They received either sage or Cystus® tea for daily mouthwash under therapy. Mucositis was scored twice a week following the Radiation Therapy Oncology Group and the European Organization for Research and Treatment Cancer (RTOG/EORTC) scoring system. Dental parameters were also recorded. Statistical evaluation of the primary endpoint was performed using t‑test and log rank test.

RESULTS

Data from 57 patients could be evaluated. Patient characteristics showed no significant difference between the two groups (n = 27 sage; n = 30 Cystus®). A total of 55 patients received the prescribed dose (60-66 Gy postoperative; 70-76.8 Gy primary). Mucositis grade 3 was observed in 23 patients (n = 11 sage; n = 12 Cystus®) and occurred between day 16 and 50 after start of therapy. There was no significant difference between the two groups in latency (p = 0.75) and frequency (p = 0.85) of the occurrence of mucositis grade 3. The self-assessment of the oral mucosa and the tolerability of the tea also showed no significant differences. Occurrence of dental pathologies appeared to increase over time after radiotherapy.

CONCLUSION

Cystus® and sage tea have a similar effect on the occurrence of radiation-induced mucositis regarding latency and incidence. Cystus® tea mouthwash solution is tolerated well and can be applied in addition to intensive oral care and hygiene along with the application of fluorides.

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.

Salivary Gland Hypofunction and Xerostomia in Head and Neck Radiation Patients

BACKGROUND

The most manifest long-term consequences of radiation therapy in the head and neck cancer patient are salivary gland hypofunction and a sensation of oral dryness (xerostomia).

METHODS

This critical review addresses the consequences of radiation injury to salivary gland tissue, the clinical management of salivary gland hypofunction and xerostomia, and current and potential strategies to prevent or reduce radiation injury to salivary gland tissue or restore the function of radiation-injured salivary gland tissue.

RESULTS

Salivary gland hypofunction and xerostomia have severe implications for oral functioning, maintenance of oral and general health, and quality of life. Significant progress has been made to spare salivary gland function chiefly due to advances in radiation techniques. Other strategies have also been developed, e.g., radioprotectors, identification and preservation/expansion of salivary stem cells by stimulation with cholinergic muscarinic agonists, and application of new lubricating or stimulatory agents, surgical transfer of submandibular glands, and acupuncture.

CONCLUSION

Many advances to manage salivary gland hypofunction and xerostomia induced by radiation therapy still only offer partial protection since they are often of short duration, lack the protective effects of saliva, or potentially have significant adverse effects. Intensity-modulated radiation therapy (IMRT), and its next step, proton therapy, have the greatest potential as a management strategy for permanently preserving salivary gland function in head and neck cancer patients.Presently, gene transfer to supplement fluid formation and stem cell transfer to increase the regenerative potential in radiation-damaged salivary glands are promising approaches for regaining function and/or regeneration of radiation-damaged salivary gland tissue.

In vivo and in vitro radiotherapy increased dentin enzymatic activity

OBJECTIVES

The present study investigated the effects of in vitro and in-vivo radiotherapy on endogenous enzymatic activity in dentin using gelatin zymography and in-situ zymography.

METHODS

Gelatin zymographic assays were performed on protein extracts obtained from dentin powder of sound non-irradiated (NRT), in vitro irradiated (VTRT) and in vivo irradiated (VIRT) human teeth. Their proteolytic activities were quantified using band densitometric evaluation. For in-situ zymography, dentin specimens from NRT, VIRT and VTRT were covered with fluorescein-conjugated gelatin and examined with confocal laser-scanning microscopy. Fluorescence intensity emitted by the hydrolyzed fluorescein-conjugated gelatin was quantified and statistically analyzed. In-situ zymography data were statistically analyzed using Kruskal-Wallis ANOVA and Dunn's multiple comparison procedures (α = 0.05).

RESULTS

No difference between in vitro and in vivo radiotherapy treatment was found. Both VTRT and VIRT groups showed increase in MMP-9 expression when compared to NRT group. Significant increases (p < 0.05) in gelatinolytic activity (26 % for VTRT; 55 % for VIRT) were observed when compared to the NRT group.

CONCLUSION

Radiotherapy increase endogenous enzymatic activity in non-restored dentin.

The effect of radiotherapy delivery time and obturation materials on the fracture resistance of mandibular premolars

OBJECTIVES

This ex vivo study was performed to investigate the effect of radiotherapy (RT) delivery time on fracture resistance of mandibular premolars filled with Biodentine or gutta-percha/sealer (GPS).

MATERIALS AND METHODS

Seventy-two mandibular premolars were used in this study. Randomly selected 24 teeth were kept intact for the control groups (with and without irradiation). Then, the remaining 48 teeth were randomly assigned into 4 groups (n = 12) according to RT delivery time (irradiated before or after root canal treatment) and obturation materials as follows: Group RT + GPS, Group: GPS + RT, Group RT + Biodentine and Group Biodentine + RT. The samples were either initially endodontically treated and then irradiated or initially irradiated and then endodontically treated with one of the abovementioned materials. The samples were irradiated at 2 Gy per fraction, 5 times a week for a total dose of 60 Gy in 30 fractions over 6 weeks. The roots were embedded in self-polymerizing acrylic resin. The fracture resistance was evaluated in a universal testing machine. Data was analyzed by one-way ANOVA and Games-Howell post hoc test at p < 0.05.

RESULTS

Radiation therapy significantly reduced fracture resistance of intact teeth (p < 0.05). The highest fracture resistance was observed in intact/non-irradiated teeth and the lowest fracture resistance in Biodentine + RT group (p < 0.05). The effect of RT delivery time was insignificant when GPS was preferred as the root canal filling material (p > 0.05); it was significant when preferring Biodentine (p < 0.05). When RT was applied to the teeth after Biodentine obturation, the fracture resistance decreased significantly compared to the teeth that were obturated with GPS after or before RT application (p < 0.05).

CONCLUSION

Both RT time and obturation materials (Biodentine or gutta-percha/sealer) affect the fracture resistance of the endodontically treated teeth.

CLINICAL RELEVANCE

Endodontic treatment could be completed with both materials after RT; however, when the endodontic treatment was initially completed and the teeth were subsequently exposed to RT, it was shown that the reinforcement effect of Biodentine decreased.

Pre-radiotherapy dental extractions in patients with head and neck cancer: a Delphi study

OBJECTIVES

To gain a consensus from consultants in restorative dentistry about the types of teeth that should be extracted from head and neck cancer patients (HNC) pre-radiotherapy.

MATERIALS

Literature- and clinician-informed questionnaires were emailed to an 'expert panel' of consultants (n = 24/28; 86%) in the United Kingdom (UK) and Ireland on three consecutive occasions (Delphi rounds). The results of Round 1 were used to revise the questionnaire that was distributed in Round 2, and this procedure was repeated for Round 3. During Rounds 2 and 3, participants were asked to indicate, on a 5-point Likert scale, their level of agreement with a series of statements on the types of teeth that should be extracted pre-radiotherapy. The target level of consensus for each statement was 70%.

RESULTS

In Round 2, there was consensus-agreement for 69 of 102 statements (i.e. ≥ 70% of participants rated 'agree' or 'strongly agree' to the relevant statement). Consensus agreement was also achieved for 20 of 28 statements in Round 3. Therefore, a total of 89 consensus statements are presented that illuminate the decision-making process for the pre-radiotherapy extraction of molar, premolar, and anterior teeth with periodontal pocketing, furcation disease, mobility, caries, tooth-wear, apical disease, or other pathology.

CONCLUSION

The statements represent the consensus professional views of participated consultants in restorative dentistry in the UK and Ireland regarding the types of teeth that should be extracted from HNC patients pre-radiotherapy. The results provide a platform for the development of future guidelines.

CLINICAL SIGNIFICANCE

Pre-radiotherapy dental assessments for head and neck cancer patients are considered mandatory. This study presents different criteria that should be considered for the treatment planning of these patients in relation to pre-radiotherapy extractions, according to the collective consensus opinion of participated consultants in restorative dentistry in the UK and Ireland.

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.

Effects of different anti-caries procedures on microhardness and micromorphology of irradiated permanent enamel

To explore the effects of infiltration resin, casein phosphate polypeptide-amorphous calcium phosphate (CPP-ACP) and fluoride on microhardness and micromorphology of irradiated enamel. Sixty human permanent teeth were mesiodistally sectioned, yielding 120 enamel samples, which randomly divided into 8 groups: G1: blank control; G2: irradiation control; G3: irradiation+fluoride; G4: irradiation+CPP-ACP; G5: irradiation+CPP-ACP+fluoride; G6: irradiation+infiltration resin; G7: irradiation+infiltration resin+fluoride; G8: irradiation+infiltration resin+CPP-ACP. A progressive improvement was observed on the superficial morphology of enamel treated with different anti-caries procedures. The order of microhardness values after irradiation from the highest to the lowest was as follows: G1>G8~G7>G6>G5>G4~G3>G2. CPP-ACP, infiltration resin and fluoride can effectively restore the direct destruction of enamel caused by irradiation and promote the occurrence of remineralization. Infiltration resin and its combined effects with fluoride or CPP-ACP have the most potential anti-caries agent to resist radiation-caries.

Impact of Clustering Oral Symptoms in the Pathogenesis of Radiation Caries: A Systematic Review

Radiation-related caries (RRC) is a disease with a high potential for destruction of the dentition, which impairs quality of life in head-and-neck (HN) cancer (HNC) patients who undergo radiotherapy. In light of the recently described “clustering of oral symptoms theory,” the present systematic review (PROSPERO CRD42019132709) aims to assess HN and gastrointestinal (GI) symptom clusters among HNC patients and discusses how these indirect effects of cancer therapy play a pivotal role in the pathophysiology of RRC. The search was performed at PubMed, Scopus, and Embase and resulted in 11 studies that met the inclusion criteria. Data extraction was performed with respect to the presence of HN/GI symptom clusters among HNC patients. The methodological data of the studies included were assessed using the MAStARI and GRADE instruments. The most prevalent reported HN symptoms were dysphagia, xerostomia, and pain. Taste alterations and fatigue were also commonly reported by the patients. Loss of appetite and weight loss were regularly reported in the studies, as well as nausea and vomiting. The results of the present study suggest that HNC treatment generates clusters of oral symptoms, leading to dietary changes, impaired oral hygiene, enamel fragility, and a highly cariogenic oral environment, which may impact the risk for RRC. A better understanding of oral symptom clustering could be of considerable clinical significance for the oral health and quality of life of HNC patients. Therefore, contemporary protocols of RRC prevention must take this broader treatment scenario of symptom clusters such as oral side effects into account.