Radiotherapy does not impair dentin adhesive properties in head and neck cancer patients

Effect of radiotherapy, immediate dentin sealing and irrigation simulating single- or two-visits endodontic treatment on the bond strength to pulp chamber dentin: an in vitro study

This study aimed to evaluate the influence of radiotherapy and different endodontic treatment protocols on the bond strength to pulp chamber dentin. Eighty mandibular molars were randomly divided into two groups (n = 40): non-irradiated and irradiated (60 Gy). The pulp chambers were sectioned, and each group was subdivided (n = 8), according to the endodontic treatment protocol: no treatment (Control); Single-visit; Two-visits; Immediate dentin sealing (IDS) + single-visit; and IDS + two-visits. Each endodontic treatment visit was simulated through irrigation with 2.5% NaOCl, 17% EDTA and distilled water. IDS was performed by actively applying two coats of a universal adhesive to the lateral walls of the pulp chamber. After, the pulp chambers were restored with resin composite and four sticks were obtained for microtensile test. In addition, the dentin of the pulp chamber roof was assessed for surface roughness, chemical composition, and topography after each treatment protocol. Two-way ANOVA, Tukey's post hoc, Mann-Whitney, Kruskal-Wallis and Dunn's post hoc were performed (α = 5%). The treatment protocol affected bond strength (p < 0.05), while the irradiation did not (p > 0.05). The control group presented the highest values (p < 0.05). The single-visit group demonstrated better performance compared to the other groups (p < 0.05), which did not differ from each other (p > 0.05) The use of IDS changed the surface roughness (p < 0.05), chemical composition (p < 0.05) and topography of the dentin. In conclusion, the treatment protocol influenced dentin adhesion, while irradiation did not.

Preventive and restorative alternatives to caries by irradiation: a scoping review

PURPOSE

This study is to conduct a comprehensive scoping review to map scientific evidence and clarify concepts regarding the commonly recommended preventive and restorative dental treatments for patients diagnosed with head and neck cancer (HNC) and subjected to radiotherapy.

MATERIAL AND METHODS

This systematic scoping review was performed under the PRISMA-ScR guidelines. The study's experimental design was registered in the Open Science Framework. In vitro studies that evaluated preventive and restorative dental treatment over 50 Gy radiation doses were included. The search was conducted in November 2023 in five electronic databases (PubMed, Scopus, Web of Science, Cochrane Library, and Embase) without language or date restriction. A search strategy was applied based on keywords, MeSh terms, or synonyms. A descriptive analysis was conducted.

RESULTS

A total of 49 studies, out of 3679 original articles identified, were included and reviewed. Of the included studies, three evaluated saliva stimulants and 35 evaluated fluoride-based preventive materials: gel (n = 18) toothpaste (n = 11) mouth rinse (n = 8) and varnish (n = 5) while 14 evaluated restorative materials: resin composite (n = 12) glass ionomer cement (n = 6) and amalgam (n = 1) Of those studies, 36 were clinical trials and 13 were in vitro studies.

CONCLUSION

Fluoride gel was the most frequently recommended preventive material for preventing radiation caries with supportive clinical evidence. Resin composite and glass ionomer were the most frequently used restorative materials, respectively. However, there is not yet clinical evidence to support the use of resin composite in irradiated teeth.

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.

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.

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.

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.

Impact of radiotherapy on the bond strength of different adhesive systems to human dentin

Aim: The aim of this study is to evaluate the effect of radiotherapy on the bond strength of resin-based composite restorations to dentin, performed either 24 h or 1 year before or after radiation. Methods: Ninety-six posterior teeth were randomly distributed into the following groups: IB (n = 16), irradiated teeth were restored 1 year after x-ray application; NB (n = 16), not irradiated teeth were stored for 1 year and then restored. IA (n = 32), teeth were restored and irradiated at 24 h or 1 year after the restoration. NA (n = 32), teeth were restored, not irradiated, and tested as IA. Eight samples from each group were randomly assigned to either the three-step or two-step etch-and rinse adhesive system procedure. The irradiated specimens were subjected to 60 Gy of x-ray radiation fractionally. The restored teeth were vertically sectioned, and 1-mm2 resin–dentin sticks were obtained and submitted to the microtensile bond strength test. The bond strength data were analyzed by two-way analysis of variance (ANOVA) followed by Tukey’s test (p < 0.05). Failure modes were examined by optical microscopy and scanning electron microscopy. Results: The IB group showed lower bond strength values compared to the NB group. The bond strength values between the adhesive systems were not statistically different. Conclusion: The application of radiation dose decreased the bond strength of the adhesive restorations to dentin when the bonding procedure was conducted 1 year after in vitro radiotherapy.

Efficiency of desensitizing materials in xerostomic patients with head and neck cancer: a comparative clinical study

OBJECTIVES

To assess the clinical effectiveness of four desensitizing materials in patients who are xerostomic due to radiotherapy for head and neck cancer (HNC) in comparison to a healthy group with normal salivation.

METHODS AND MATERIALS

The study was conducted as a split-mouth randomized clinical trial. Forty HNC patients (group A) and 46 healthy patients (group B) suffering from dentin hypersensitivity (DH) were included. Salivary flow was determined through a scialometric test. Hypersensitivity was assessed with air stimulus and tactile stimulus. The materials used as desensitizing agents were Vertise Flow, Universal Dentin Sealant, Clearfil Protect Bond, and Flor-Opal Varnish. The response was recorded before application of the materials, immediately after, and at 1 week, 4 weeks, and 12 weeks.

RESULTS

Salivary flow rates in groups A/B were 0.15/0.53 mL/min (unstimulated) and 0.54/1.27 mL/min (stimulated), respectively. In group A, 100 hypersensitive teeth were included. Application of the desensitizing agents significantly decreased the hypersensitivity immediately and throughout the 4-week follow-up (p < 0.001). However, after the 12-week timepoint, a loss of efficacy was detected in all agents (p = 0.131). In group B, 116 hypersensitive teeth were included. The materials performed a more stable action, although a loss of effectiveness was detected at 12-week control (p = 0.297).

CONCLUSION

The efficiency of the desensitizing agents after the first application was similar in both groups. In the radiated group, this effect lasted for shorter periods than in healthy controls.

CLINICAL RELEVANCE

HNC patients with hyposalivation may be a new risk group for DH.

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.

Tensile Bond Strengths of Two Adhesives on Irradiated and Nonirradiated Human Dentin

The aim of this study was to assess the effect of radiotherapy on bond efficiency of two different adhesive systems using tensile bond strength test. Twenty extracted teeth after radiotherapy and twenty nonirradiated extracted teeth were used. The irradiation was applied in vivo to a minimal dose of 50 Gy. The specimens of each group were randomly assigned to two subgroups to test two different adhesive systems. A three-step/etch-and-rinse adhesive system (Optibond FL) and a two-steps/self-etch adhesive system (Optibond XTR) were used. Composite buildups were performed with a nanohybrid composite (Herculite XTR). All specimens were submitted to thermocycling ageing (10000 cycles). The specimens were sectioned in 1 mm(2) sticks. Microtensile bond strength tests were measured. Nonparametric statistical analyses were performed due to nonnormality of data. Optibond XTR on irradiated and nonirradiated teeth did not show any significant differences. However, Optibond FL bond strength was more effective on nonirradiated teeth than on irradiated teeth. Within the limitations of an in vitro study, it can be concluded that radiotherapy had a significant detrimental effect on bond strength to human dentin. However, it seems that adhesive choice could be adapted to the substrata. According to the present study, the two-steps/self-etch (Optibond XTR) adhesive system tested could be more effective on irradiated dentin compared to three-steps/etch-and-rinse adhesive system (Optibond FL).

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.

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.