Dosimetric parameters and radiotherapy simulation methods used in preclinical studies of radiation damage to the dentition: a systematic review.

OBJECTIVE: This systematic review investigated the dosimetric parameters used in preclinical studies. STUDY DESIGN: Searches were performed in 3 databases (PubMed, Scopus, and Embase) and gray literature to identify studies for review. In vitro and ex vivo studies that examined the effect of radiation on human permanent teeth were included. The modified Consolidated Standards Of Reporting Trials checklist of items for reporting preclinical in vitro studies was used to assess the risk of bias. RESULTS: In total, 32 studies met the inclusion criteria. The average radiation dose of in vitro studies was 53 (±22) Gy and in ex vivo studies was 69 (±1) Gy. Twenty-two studies used 5 different fractionation schemes. Twenty-two of the included studies did not report the radiotherapy modality of those reporting. Twenty studies used linear accelerators, and 7 used Cobalt-60 with the source-surface-distance of radiation ranging from 1.5 to 100 cm. Distilled water was the storage solution for the dental structure used most commonly. Biases were observed, including small sample sizes, lack of randomization, and blinding processes. CONCLUSION: The dosimetric parameters used in the preclinical studies, including radiation dose, radiotherapy modality, fractionation regime, and the storage solutions used did not support the hypothesis of direct effects of radiation on the dental structure.

Acid dissolution of ultrathin glass-ceramic and its correlation with flexural strength.

STATEMENT OF PROBLEM: When glass-ceramics are treated with hydrofluoric acid (HF), not only the area of application is affected but also other surfaces. Information regarding the correlation of the dissolution caused by HF and the flexural strength of the ceramic is lacking. PURPOSE: The purpose of this in vitro study was to investigate the effect of HF etching protocols on the flexural strength of 2 glass-ceramics, the correlation of their flexural strength with the internal and lateral dissolution, and the differences in Weibull characteristics concerning the etching protocols. MATERIAL AND METHODS: Specimens (4×12×0.3mm) of leucite-reinforced glass-ceramic-LEU (IPS Empress) and of lithium disilicate-reinforced glass-ceramic-LD (IPS e.max) were prepared. The specimens were divided into 5 groups (n=12) according to etching protocol: control-untreated; hydrofluoric acid (HF) 5% for 20 seconds (HF5%20s); HF5%60s; HF10%20s; and HF10%60s. Flexural strength was evaluated through 3-point bend testing. The fractured specimens were submitted to a morphological and metrical analysis of each pattern (LEU I-IV, LD I-III) on the lateral surface (LS) and of the dissolution areas (µm2) on the internal surface (IS) using a scanning electron microscopy (SEM) and a software program (FIJI). Flexural strength (MPa) values were analyzed by 1-way ANOVA, Bonferroni test, and Weibull and the correlation between flexural strength and dissolution by Pearson correlation coefficient (α=.05). RESULTS: ANOVA revealed that the HF etching protocol was significant (P<.001) for LEU ceramic. When HF10%60s was applied, LEU showed Weibull characteristic strength (σθ) values lower than those of the other protocols. LD showed no difference in σθ and reliability (m) among the groups. The internal dissolution areas concerning LEU had a significant high negative correlation with the flexural strength (r=-0.6; P<.001). LEU-IV on the LS was the only pattern to show a significant decrease in flexural strength (r=-0.3, P<.05). CONCLUSIONS: Special care should be taken when applying hydrofluoric acid on glass-ceramic restorations. Protocols with higher hydrofluoric acid concentrations and longer application times were more related to greater internal areas of dissolution which reduced the flexural strength of leucite ceramics.

Over 300 Radiation Caries Papers: Reflections From the Rearview Mirror.

Radiation caries (RC) is an aggressive oral toxicity in head and neck cancer survivors, which develops 6 to 12 months after head and neck radiotherapy. It initially affects the tooth cervical/incisal surfaces, and if not promptly diagnosed/managed, progresses to dental crown amputation and risk of osteoradionecrosis. It results from a multidimensional cluster of treatment-induced oral symptoms, including hyposalivation, dietary changes, and oral hygiene impairment. Although recognized as a frequent complication of radiotherapy and extensively assessed by a myriad of retrospective, in vitro, and in situ studies, RC patients are still orphans of clinically validated methods for risk prediction, prevention, and treatment of early lesions. This review provides a historical overview of science-based concepts regarding RC pathogenesis and treatment, emphasizing the growing demand for interventional clinical studies (randomized trials).

Impact of head and neck radiotherapy on the longevity of dental adhesive restorations: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Established restorative protocols for patients after head and neck radiotherapy are lacking, increasing the failure rates of dental adhesive restorations. PURPOSE: The purpose of this systematic review and meta-analysis was to analyze the evidence regarding the impact of head and neck radiotherapy on the longevity of dental adhesive restorations. MATERIAL AND METHODS: A search was performed using PubMed, Scopus, and Embase in May 2018 (updated in November 2020). Data extraction was performed regarding the percentage of restoration failure among dental adhesive materials, including glass ionomer cements, resin-modified glass ionomer cements, and composite resins. Risk of bias was assessed by the meta-analysis of statistics assessment and review instrument (MAStARI). Confidence in cumulative evidence was evaluated by the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) protocol. RESULTS: Four studies met the inclusion criteria. All included studies were classified as having a moderate risk of bias and reported results regarding class V restorations. Overall, composite resins presented lower failure rates at 2 years (30%) when compared with resin-modified glass ionomer (41%) and glass ionomer cements (57%). Meta-analysis showed that the risk of failure with glass ionomer cements was greater than with resin-modified glass ionomer cements (RR: 1.71, P<.001). Composite resins presented lower risk of failure when compared with glass ionomer (RR: 2.29, P<.001) and resin-modified glass ionomer cements (RR: 1.30, P=.03). Three studies reported results regarding fluoride compliance, which had a negative effect on the survival rates of glass ionomer and resin-modified glass ionomer cements and a positive effect on composite resin restorations. CONCLUSIONS: The results suggest that composite resin restorations associated with fluoride gel compliance seems to be the best alternative for restoring class V lesions in patients after head and neck radiotherapy. However, the results showed moderate certainty of evidence, which justifies the need for more randomized clinical trials regarding this subject.

Dissolution Depth and Surface Morphological Alterations in Ultrathin Glass Ceramic Etched with Different Hydrofluoric Acid-etching Protocols.

PURPOSE: To evaluate the effect of different HF-etching protocols on the dissolution depth and micromorphology of the etched and adjacent surfaces of ultrathin glass-ceramic specimens. MATERIALS AND METHODS: One hundred twenty specimens (6 x 6 x 0.3 mm) of leucite-reinforced glass-ceramic (LEU, IPS Empress, Ivoclar Vivadent) and lithium-disilicate-reinforced glass-ceramic (LD, IPS e.max, Ivoclar Vivadent) were prepared. Specimens were divided into 5 groups (n = 12) according to etching protocol: G1: control, untreated; G2: 5% hydrofluoric acid (HF) etching for 20 s (HF5%20s); G3: HF5%60s; G4: HF10%20s; and G5: HF10%60s. To analyze the dissolution depth, specimens were sectioned into two similarly sized halves using a chisel to create an internal surface (IS). Specimens were analyzed with scanning electron microscopy (SEM) on the following surfaces: HF application surface (AS), lateral surface (LS), internal surface (IS), and the surface opposite to the AS (OS). Dissolution patterns were identified. Data were submitted to one-way ANOVA and Bonferroni's test (α = 0.05). Dissolution depth data were submitted to Kruskal-Wallis and Mann-Whitney U-tests (α = 0.05). The prevalence of different dissolution patterns was analyzed using SEM. RESULTS: HF gel applied on the AS also affected the adjacent surfaces of all specimens. Different dissolution patterns were observed, which were dependent of HF-etching protocol and proportion of the glass phase in the ceramic. These patterns were categorized into four types for LEU (I-IV) and three for LD (I-III) according to the micropore size. The greater the micropore size, the more pronounced the etching pattern (p < 0.001). Higher HF times and concentrations showed prevalence of more severe etching patterns. HF10%60s produced greater dissolution depth in both materials when compared with other HF-etching groups (p < 0.05). CONCLUSION: Hydrofluoric acid etching not only affects the surface upon which it is applied, but internal, lateral and even opposite edges of glass ceramic. Different dissolution patterns and depths can be formed which are dependent of hydrofluoric acid concentration, application time, and proportion of the glass phase in the ceramic.

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.

Radiation-related caries: current diagnostic, prognostic, and management paradigms.

OBJECTIVE AND STUDY DESIGN: This narrative review summarizes the current state of art of radiation-related caries (RC), an aggressive disease that affects approximately 30% of post-head and neck radiotherapy (HNRT) patients. RESULTS: RC mainly affects the tooth cervical areas and incisal/cuspal tips and develops 6 to 12 months after HNRT. Early RC signs include black/brownish tooth discoloration and enamel cracks, which progress to enamel delamination, exposing underlying dentin to a highly cariogenic oral environment and rapid tooth destruction/dental crown amputation. As RC advances and renders the tooth nonrestorable, it may lead to osteoradionecrosis spontaneously or upon extraction if the tooth is in a highly irradiated field of the oral cavity. This requires aggressive treatment, which would have a negative impact on a cancer survivor's quality of life and contribute to the incremental cost of cancer care. Chlorhexidine mouth rinses and topical fluoride applications are effective agents used in RC prevention; however, there are no well-established treatment protocols. Once RC progresses, dental restorations should be performed with adhesive materials in association with systematic fluoride application as illustrated in the clinical case presented in this review. Post-HNRT patients should be closely followed up for optimal RC prevention, early diagnosis, and prompt treatment. CONCLUSIONS: Future clinical studies are necessary to establish a contemporary, clinically validated protocol for RC management.

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.

Massive extrusion of calcium hydroxide paste containing barium sulphate during endodontic treatment.

A 31-year-old woman was referred for the evaluation of persistent lower lip numbness following endodontic treatment of tooth #36. Imaging examinations showed a large amount of radiopaque/hyperdense material spread in an angiographic distribution in the left mandibular body region. Laboratory analyses of tooth #36 and adjacent periapical tissue, surgically extracted in an external Service due to acute pain following endodontic treatment, identified chronic inflammatory reaction and birefringent crystalloid foreign bodies rich in barium and sulphur, leading to the diagnosis of alveolar nerve injury due to accidental extrusion of intracanal dressing material composed of calcium hydroxide [Ca(OH)2 ] paste incorporated with barium sulphate. Clinicians should be aware that Ca(OH)2 when in contact with periapical tissues may lead to persistent toxicities, such as necrosis, pain and paraesthesia. Therefore, injectable Ca(OH)2 systems should be used with caution because they can cause paste extrusion and damage to the lower alveolar nerve.

Effect of cleaning protocol on silica deposition and silica-mediated bonding to Y-TZP.

OBJECTIVES: To evaluate the effect of cleaning methods on the deposition of silica on yttria-stabilized zirconium dioxide (Y-TZP) surface and on the silane-silica mediated bond strength between Y-TZP and resin cement. METHODS: Y-TZP slabs were air-abraded with 30µm silica-coated alumina particles and distributed in three groups: no cleaning, cleaning with a stream of oil-free air/water spray for 5s and cleaning with an ultrasonic bath in water for 10min. The distribution of Si on the Y-TZP surfaces was recorded using energy dispersive spectroscopy (EDS). After the treatment was applied, Y-TZP slabs (n=20) received a primer application and resin cement cylinders were built on the surface. After storage (24h) in water storage or 3 months plus thermocycling; n=10), microshear bond strength test (µSBS) was performed. X- ray Photoelectron Spectroscopy (XPS) characterized the chemical bonds between the silica layer and the silane-containing primer. Data were analyzed using ANOVA and Tukey test, as well as Weibull analysis (α=0.05). RESULTS: Cleaning method had a significant effect on the amount of Si deposited on zirconia surface (p<0.001) and, consequently, on bond strength (p<0.001). Storage/aging also had a significant effect on bond strength (p<0.001). Low values of Weibull moduli for bond strength were observed for all groups after aging. XPS showed silane-silica chemical interaction for all groups. SIGNIFICANCE: The silica deposited by tribochemical coating to Y-TZP was removed by the cleaning methods evaluated, compromising bond strength. Stability of the bonding is also a concern when no cleaning method is applied.

Effect of silane and MDP-based primers on physico-chemical properties of zirconia and its bond strength to resin cement.

OBJECTIVE: To evaluate the effect of surface treatments on yttria-tetragonal zirconia polycrystal (Y-TZP) characteristics and on resin-mediated zirconia bond. METHODS: Y-TZP slabs were grit blasted with 45µm alumina or with 30µm silica-coated alumina particles. The chemical treatments were: no-chemical treatment (NC), silane-containing primer (SP), MDP (10-Methacryloyloxydecyl dihydrogen phosphate) and silane-containing primer (MPS), MDP-containing primer (MP) and MDP and silane-containing adhesive (MPA). Contact angle as a function of surface roughness (θm) and surface roughness parameter (Sdr) were measured using Fringe Projection Phase Shifting (FPPS). Surface free energy (γsTOT) was calculated with a goniometer. Chemical interaction between primers/adhesive and zirconia was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Resin cement microshear bond strength (µSBS) was analyzed at either 24-h or 8-months water storage (37°C). θm values, Sdr values, γsTOT and µSBS values were analyzed using Analysis of variance (ANOVA) and post hoc Tukey test (α=0.05). RESULTS: Chemical treatment had an effect (p<0.001) on all surface parameters analyzed: θm, γsTOT and Sdr. MP-treated group showed higher incidence of P-O-Zr bonds than the other groups, indicating more chemical linkages. Grit blasting (p<0.001) and the interaction chemical treatment*storage (p<0.001) did not affect µSBS; all silane-containing primers showed significant drop in µSBS after aging. SIGNIFICANCE: MDP and/or silane-based solutions affect the physicochemical properties of blasted-zirconia. An MDP-based primer is fundamental to achieve a stable resin-zirconia bonding, but the chemical reactivity of MDP is impaired when this molecule is present in a multicomponent system.

Bond Strength of CAD/CAM Restorative Materials Treated with Different Surface Etching Protocols.

PURPOSE: To evaluate the effect of different surface treatments on the surface morphology of CAD/CAM ceramics and on their bond strength to cement. MATERIALS AND METHODS: Sixty cubic sections were cut from each of three materials (lithium disilicate glass-ceramic [DL], leucite-based glass-ceramic [LC], resin-matrix ceramic composite [RMCC]) and were treated as follows (n = 10): 1. no treatment (C); 2. 5% hydrofluoric acid applied for 20 s plus silane (HF5% 20 s); 3. 5% hydrofluoric acid applied for 60 s plus silane (HF5% 60 s); 4. 10% hydrofluoric acid applied for 20 s plus silane (HF10% 20 s); 5. 10% hydrofluoric acid applied for 60 s plus silane (HF10% 60 s); 6. Self-etching ceramic primer (MBEP). Ceramic cubes were bonded to pre-polymerized composite resin cubes with a composite cement. Each set was cut into stick-shaped specimens (1 ± 0.3 mm2). After 24-h water storage, microtensile bond strength (µTBS) was measured. Data were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Failure pattern and surface morphology were assessed using scanning electron microscopy (SEM). RESULTS: Both factors significantly influenced µTBS, while no interaction between factors was found. RMCC presented statistically higher µTBS values than LC and DL, while the surface treatments HF5% 20 s, HF5% 60 s, HF10% 20 s, HF10% 60 s and MBEP, did not show statistical differences between them, although they resulted in statistically significantly higher bond strengths than did C groups. A high number of pre-test failures were detected in the control groups for all materials. MBEP produced less extensive surface alterations than did all HF treatments. CONCLUSION: All of the hydrofluoric acid treatments tested showed similar cement-ceramic bonding efficacy. The self-etching ceramic primer produced less surface alterations and comparable bonding efficacy compared to separate hydrofluoric acid/silane primer application.

In Vivo Measurement of Root Canal Wall Temperature at Different Stages Prior to Fiber Post Cementation.

OBJECTIVE: This study measured the in vivo temperature of prepared root canal walls during various stages of treatment prior to endodontic postcementation. MATERIALS AND METHODS: One tooth each from five patients requiring endodontic treatment received conventional gutta-percha obturation. The coronal 4 mm of gutta-percha was removed by drilling and the canal wall temperature was measured. A sterile, saline rinse was applied, and another temperature value was recorded. Paper points were placed, and the wall temperature was recorded. A standardized period of 1.5 minute passed, simulating time needed to mix and place the resin cement and post (no resin was placed), after which the final wall temperature was obtained. The tooth was temporized and scheduled for prosthetic reconstruction. A one-way repeated measure analysis of variance (with Tukey's post hoc test) was performed among mean temperature values for each treatment stage (preset α 0.05). RESULTS: Significant temperature differences were found among the treatment stages. Canal space drilling yielded the highest temperature (35.5 ± 0.8°C), while the lowest was obtained after saline rinsing (34.0 ± 0.9°C). The temperature of prepared root canal wall prior to postplacement (34.9 ± 1.2°C) and following paper point drying (34.8 ± 1.1°C) presented intermediate results, with no statistical difference between them. CONCLUSIONS: This study suggested that root canal wall temperature varied during various stages of preparation prior to endodontic post.

Comparison of in vivo and in vitro models to evaluate pulp temperature rise during exposure to a Polywave® LED light curing unit.

OBJECTIVES: To measure and compare in vivo and in vitro pulp temperature (PT) increase (ΔTEMP) over baseline, physiologic temperature using the same intact upper premolars exposed to the same Polywave® LED curing light. METHODOLOGY: After local Ethics Committee approval (#255,945), local anesthesia, rubber dam isolation, small occlusal preparations/minute pulp exposure (n=15) were performed in teeth requiring extraction for orthodontic reasons. A sterile probe of a temperature measurement system (Temperature Data Acquisition, Physitemp) was placed within the pulp chamber and the buccal surface was sequentially exposed to a LED LCU (Bluephase 20i, Ivoclar Vivadent) using the following exposure modes: 10-s low or high, 5-s Turbo, and 60-s high. Afterwards, the teeth were extracted and K-type thermocouples were placed within the pulp chamber through the original access. The teeth were attached to an assembly simulating the in vivo environment, being similarly exposed while real-time temperature (°C) was recorded. ΔTEMP values and time for temperature to reach maximum (ΔTIME) were subjected to two-way ANOVA and Bonferroni's post-hoc tests (pre-set alpha 0.05). RESULTS: Higher ΔTEMP was observed in vitro than in vivo. No significant difference in ΔTIME was observed between test conditions. A significant, positive relationship was observed between radiant exposure and ΔTEMP for both conditions (in vivo: r2=0.917; p<0.001; in vitro: r2=0.919; p<0.001). CONCLUSION: Although the in vitro model overestimated in vivo PT increase, in vitro PT rise was close to in vivo values for clinically relevant exposure modes.

Physicochemical and morphological characterization of a glass ceramic treated with different ceramic primers and post-silanization protocols.

OBJECTIVE: Evaluate the effect of different ceramic primers and post-silanization protocols on physicochemical and morphological characteristics of a lithium disilicate glass ceramic. METHODS: Lithium disilicate ceramic (IPS e-max CAD) plaques (6 × 10 × 2 mm) were divided into 3 groups according to the ceramic primer used: (1) Silane (RelyX Ceramic Primer-RL); (2) Silane + MDP (Clearfil Ceramic Primer Plus-CP); (3) Self-etching ceramic primer (Monobond Etch and Prime-MB). Specimens from each group were distributed into 5 sub-groups according to post-silanization protocols: (a) Treated as recommended by the manufacturer (MR), (b) MR + Additional drying with air at room temperature for 30 s (RTA), (c) MR + additional drying with hot air for 30 s (HT), (d) MR + Surface rinsing with water at room temperature for 10 s and drying with air at room temperature for 30 s (WT), and (e) Specimens were not silanized (NS). Surface free energy (SFE) was determined using static contact angles measurements with water and diiodomethane. SFE data were submitted to Friedman followed by Wilcoxon post-hoc test (α = 0.05). Morphology was analyzed using scanning electron microscopy. Elemental composition and chemical interactions were determined with X-ray photoelectron spectroscopy analysis. RESULTS: RL presented the highest SFE (62.4 mN/m) followed by CP (59.7 mN/m). Post-silanization protocols resulted in similar SFE, but WT and HT induced the highest water contact angles when using CP and RL. CP modified ceramics' surface morphology compared to the etched and RL treated groups. The presence of water was identified on CP treated specimen. All analyzed primers formed siloxane bonds with ceramic surface. SIGNIFICANCE: Ceramic primers resulted in different surface free energy and morphology, but siloxane bonds were identified for all tested solutions. HT and WT protocols should be used with RL and CP primers. MB was not influenced by the different silanization protocols.

Dentin-pulp complex reactions in conventional and radiation-related caries: A comparative study.

BACKGROUND: Radiation-related caries (RRC) is one of the most significant oral toxicities of head and neck radiotherapy (HNRT); however, the potential of radiation to directly cause harmful dentin and pulpal effects and impair response to caries progression is controversial. MATERIAL AND METHODS: Therefore, the aim of this study was to characterize the reactions of the dentin-pulp complex in teeth affected by RRC. Patients and methods: Twenty-two carious teeth extracted from 22 head and neck cancer (HNC) patients were divided into control (conventional caries; n=11) and irradiated (RRC; n=11) groups and paired matched by dental homology, clinical patterns of caries progression following the Post-Radiation Dental Index (PRDI) and microscopic depth of carious invasion. Histopathological characteristics based on morphological hierarchy, cell populations of dental pulp, blood vessels, neural elements, extracellular matrix components, inflammation, patterns of carious invasion and reactionary dentin presence were evaluated by optical light microscopy and histomorphometry. RESULTS: Mean PRDI scores were 3.2 for the control group and 3.8 for the irradiated group. Dentin demineralization patterns were also similar between the groups and the mean depths of demineralization were 1,158.58µm and 1,056.89µm for the control and irradiated groups, respectively. CONCLUSIONS: Pulp histopathological changes and dentin reaction patterns were similar between groups and varied according to the PRDI scores and carious lesions depth. Dentin and pulp reactions are highly preserved in RRC teeth. Key words:Cancer, radiotherapy, radiation-related caries, teeth, pulp.

Bonding effectiveness of tooth-colored materials to resin cement provided by self-etching silane primer after short- and long-term storage.

STATEMENT OF PROBLEM: Glass-ceramic materials are typically treated with hydrofluoric acid (HF) and silane to improve their bond to composite resin; however, HF may be harmful to human tissues and the integrity of the material, and its application is a technique-sensitive procedure. A novel self-etching ceramic primer has been introduced with the claim that it can solve those problems. However, independent scientific evidence regarding its performance is scarce. PURPOSE: The purpose of this in vitro study was to evaluate the effect of self-etching silane primer on glass-ceramic surface roughness and on long-term bonding between glass-ceramic and composite resin cement. MATERIAL AND METHODS: Plates of 3 materials (n=10), lithium disilicate glass-ceramic (LDC) (IPS e.max CAD), leucite-based glass-ceramic (LEU) (IPS Empress CAD), and resin-modified ceramic (PIC) (VITA ENAMIC), were treated in the following ways: no treatment (C), HF (5%) applied during the recommended time for each material (HF), and self-etching ceramic primer (Monobond Etch & Prime [MBEP]). Surface roughness (Sa) was analyzed with a laser 3D profiler. Ceramic sticks were subjected to (n=20) no treatment (C); treatment with hydrofluoric acid plus silane (HF+S); and treatment with self-etching ceramic primer (MBEP) bonded to prepolymerized composite resin sticks with composite resin cement (Variolink II) and stored for 24 hours and 1 year (n=10). The assemblies were submitted to microtensile bond strength testing (µTBS). Data were analyzed using ANOVA and the Tukey pairwise, post hoc test (α=.05). Failure pattern and surface and interface morphology were assessed using scanning electron microscopy. RESULTS: Only individual factors resulted in statistically significant differences for both variables (material: P<.001; surface treatment: P=.020), interaction (P=.570). HF group (0.49 ±0.11 µm) showed statistically higher roughness values (P≤.05) than control groups (0.44 ±0.97 µm), while MBEP (0.48 ±0.11 µm) was comparable with both. HF produced greater surface alterations than MBEP and C. PIC (0.60 ±0.051 µm) exhibited significantly higher roughness values (P≤.05) than LDC (0.37 ±0.07 µm) and LEU (0.45 ±0.04). Regarding µTBS, the general mean of PIC (24.6 ±10.1 MPa) was higher (P≤.05) than LEUs (14.7 ±6.7 MPa) and LDCs (13.1 ±4.8 MPa), while treatment groups HF+S (17.9 ±10.0 MPa) and MBEP (20.5 ±9.7 MPa) produced higher µTBS values than control groups (14.2 ±5.5 MPa). Adhesive failure was associated with low µTBS values and aged specimens, while cohesive failure within the composite resin-cement layer and mixed failures were associated with higher µTBS values. Interface debonding was detected in C groups for LDC and LEU. PIC exhibited better interface stability. CONCLUSIONS: MBEP produced smoother surfaces than HF. HF+S and MBEP significantly improved ceramic and composite resin cement bonding.

Comparison of in vivo and in vitro models to evaluate pulp temperature rise during exposure to a Polywave® LED light curing unit

Abstract Objectives: To measure and compare in vivo and in vitro pulp temperature (PT) increase (ΔTEMP) over baseline, physiologic temperature using the same intact upper premolars exposed to the same Polywave® LED curing light. Methodology: After local Ethics Committee approval (#255,945), local anesthesia, rubber dam isolation, small occlusal preparations/minute pulp exposure (n=15) were performed in teeth requiring extraction for orthodontic reasons. A sterile probe of a temperature measurement system (Temperature Data Acquisition, Physitemp) was placed within the pulp chamber and the buccal surface was sequentially exposed to a LED LCU (Bluephase 20i, Ivoclar Vivadent) using the following exposure modes: 10-s low or high, 5-s Turbo, and 60-s high. Afterwards, the teeth were extracted and K-type thermocouples were placed within the pulp chamber through the original access. The teeth were attached to an assembly simulating the in vivo environment, being similarly exposed while real-time temperature (°C) was recorded. ΔTEMP values and time for temperature to reach maximum (ΔTIME) were subjected to two-way ANOVA and Bonferroni's post-hoc tests (pre-set alpha 0.05). Results: Higher ΔTEMP was observed in vitro than in vivo. No significant difference in ΔTIME was observed between test conditions. A significant, positive relationship was observed between radiant exposure and ΔTEMP for both conditions (in vivo: r2=0.917; p<0.001; in vitro: r2=0.919; p<0.001). Conclusion: Although the in vitro model overestimated in vivo PT increase, in vitro PT rise was close to in vivo values for clinically relevant exposure modes.

Depth of cure of bulk fill resin composites: A systematic review.

OBJECTIVE: To evaluate scientific evidence regarding depth of cure of bulk-fill resin composites (BFRCs) and related factors. MATERIAL AND METHODS: PubMed/Medline, Embase, Scopus, and ISI Web of Science databases were accessed from October 2016 to May 2017. Investigations published in English language, assessing depth of cure of BFRCs by microhardness test and/or degree of conversion (DC) were included. Studies using exclusively ISO 4049, employing specimens deepness less than 4 mm, as well as those not reporting exposure time and/or irradiance from light curing units (LCUs) were excluded. RESULTS: In total, 742 studies were found from which 33 were included. From 21 studies evaluating BFRCs microhardness, 10 showed acceptable bottom/top ratios (≥0.8) for all tested materials. However, material-dependent results and non-satisfactory bottom/top microhardness ratios (<0.8) were reported in 9 and 2 investigations, respectively. From 19 studies that assessed DC, 11 showed acceptable results (≥50%) for all tested BFRCs, while 8 studies reported material-dependent outcomes. Overall, irradiance from LCUs ranged from 650 to 1330 mW/cm2 and exposure time from 5 to 60 seconds. Favorable depth of cure results were observed with the use of LCUs emitting irradiance ≥1000 mW/cm2 and exposure times ≥20 seconds. CONCLUSIONS: High depth of cure rates by BFRCs, depends on some factors as material, irradiance and exposure time. Polywave LCUs were useful but not essential on polymerizing alternative photoinitiator-containing BFRC. CLINICAL SIGNIFICANCE: LED curing devices (polywave or monowave) displaying an irradiance ≥1000 mW/cm2 and 20 seconds of exposure time are imperative to accomplish successful polymerization of most BFRCs.

Cracked tooth syndrome in irradiated patients with head and neck cancer.

OBJECTIVES: The aim of this study was to assess the presence of enamel craze lines (ECLs), part of the spectrum of the so-called cracked tooth syndrome, on the surface of teeth irradiated in vivo. STUDY DESIGN: Forty teeth extracted from patients with head and neck cancer were paired, matched, and equally divided into 4 groups: noncarious irradiated (G1); noncarious control (G2); radiation-related caries (RRC) (G3), and carious control (G4). Samples were examined for ECL detection with a fiberoptic transillumination device and photographed, and ECL mean size, number, and patterns of topographic distribution in tooth crown were determined. Groups were compared accordingly: G1 versus G2; G3 versus G4. RESULTS: We analyzed 538 ECLs, of which 30.1% were found in noncarious irradiated teeth, 19.3% in noncarious controls, 27.6% in RRC, and 23% in carious controls. Non-carious irradiated teeth presented higher quantities of ECL than non-carious control (P < 0.05). Higher incidences of ECLs were identified in specific enamel topographies of anterior G1 and G3 samples (P <.05). There was no correlation between ECL size/numbers and radiation isodose delivery to teeth. CONCLUSIONS: Increased incidence of ECLs may indicate weakened enamel structure in irradiated teeth, and this may play a role in the onset and progression of RRC.