Effects of different doses of ionizing radiation on alveolar bone repair in post-extraction tooth socket: an experimental study in rats.

OBJECTIVE: This study aimed to evaluate the dose-response effects of ionizing radiation (IR) on alveolar bone repair and bone strength after tooth extraction. MATERIALS AND METHODS: A total of 32 male Wistar rats were used in the study, 28 animals were included in the final analysis, and n = 7 for each experimental group. Mandibular first molars were extracted. After 7 days, the animals were randomly divided into four groups according to single-dose irradiation: NIr, control group; Ir15, irradiated at 15 Gy; Ir20, irradiated at 20 Gy; and Ir30, irradiated at 30 Gy. The tooth extraction sites were subjected to micro-computed tomography (micro-CT), histological, histomorphometric, and biomechanical analyses 14 days after extraction. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test (α = 0.05). RESULTS: Micro-CT analysis revealed that IR led to lower values of bone volume (BV, in mm3) (0.68 ± 0.08, P < 0.001) and bone volume fraction, ratio of the segmented bone volume to the total volume of the region of interest (BV/TV, in %) (44.1 ± 8.3, P < 0.001) for the Ir30 group compared to the control group. A significantly lower amount of newly formed bone was observed in the Ir30 (P = 0.005) than in the Ir15 group. The histomorphometric results of quantification of bone matrix neoformation and the micro-CT were in agreement, demonstrating greater damage to the Ir30 group. IR30 cells showed a lower percentage of densely packed collagen than control cells. No significant differences were found in the biomechanical parameters. CONCLUSION: IR affects alveolar bone repair. A dose of 30 Gy reduced the bone healing process owing to a smaller amount of newly formed bone and a lower percentage of densely packed collagen. Therefore, a dose of 30 Gy can be used to successfully establish an animal model of an irradiated mandible that mimics the irradiated clinical conditions. CLINICAL RELEVANCE: Radiotherapy can lead to severe side effects and tooth extraction is a major risk factor. A proper understanding of the pathological mechanisms of radiation in alveolar bone repair requires the establishment of a suitable animal model of clinical conditions.

Biomechanical effects of a hard insert and air space in mouthguards on the shock absorption and protection against fractures of direct resin composite veneers from trauma.

BACKGROUND/AIM: Mouthguards (MTG) are used to prevent dental trauma. However, their protective effect on esthetic restorations and whether modified MTGs are beneficial is uncertain. The aim of this study was to evaluate the effect of hard inserts and air spaces in MTGs in protecting direct resin composite veneers during impact. MATERIALS AND METHODS: Twenty resin composite veneers (1.0 mm) were prepared on upper right central incisors on printed maxilla models using polyether. The effect of the MTGs was evaluated in four groups (n = 5): Con-MTG, conventional custom-fit MTGs made with two layers of ethylene vinyl acetate (EVA); Air-MTG, MTGs with the insertion of 2.0 mm air space between the two layers of EVA and tooth surface; PETG-MTG, MTGs with 1.0 mm of polyethylene terephthalate glycol-modified (PETG) inserted between the EVA layers; and No-MTG, comprising resin composite veneers without MTG. The printed models were fixed in a pendulum device, and the impact was performed at 30°. The strain (µS) and shock absorption (%) of the MTG were recorded using strain gauges. Failure modes and cracks were evaluated using macro photography and transillumination and analyzed using the chi-square test. Strain and shock absorption data were analyzed using the one-way analysis of variance followed by Tukey's test (α = 0.05). RESULTS: Mouthguards reduced strain and enhanced shock absorption, regardless of the MTG type (p < .001). Con-MTG, Air-MTG, and PETG-MTG had shock absorption rates of 76.1%, 72.3%, and 33.4%, respectively (p < .001). The single No-MTG model had a root fracture, while all the others had superficial damage. None of the MTG models had cracks or fractures. CONCLUSIONS: Mouthguards protected the resin composite veneers. The Con-MTG and Air-MTG groups had lower strain and greater shock absorption than the PETG-MTG. Resin veneers had no cracks or damage following MTG use. However, 80% of the veneers had surface damage when no MTG was used.

Fluorescence-aided identification technique using a low-cost violet flashlight and rotatory instruments for dental trauma splint removal.

BACKGROUND/AIM: Removing resin composites used for bonding dental trauma splints may result in irreversible damage to the enamel. This in vitro study evaluated the influence of additional violet illumination and different bur types on damage caused to tooth enamel. MATERIALS AND METHODS: Fifteen maxillary models with four bovine incisor teeth were prepared. All models were scanned using a laboratory scanning system (s600 ARTI; Zirkonzahn). Six experimental groups (n = 10) were generated by two study factors: lighting type (three levels), (1) low-cost (5-7 US$) violet LED flashlight (LUATEK, LT 408); (2) VALO Cordless light curing unit (Ultradent) with black lens; or (3) without additional illumination; and rotatory instrument (two levels), (1) diamond bur or (2) multifluted tungsten-carbide bur. New scanning was performed after splint removal, and the generated files were superimposed on the initial scans using Cumulus software. The light emitted by both violet light sources was characterized by using integrating sphere and beam profile. A qualitative and quantitative analysis of enamel damage and two-way ANOVA followed by Tukey's post hoc was used at an α = 0.05. RESULTS: The use of low-cost violet flashlight that emitted the violet peak light at 385 nm and VALO Cordless with black lens at 396 nm resulted in significantly lower damage to the enamel surface than those in the groups without additional violet light (p < .001). An interaction between rotatory instruments and lighting was found. When no additional violet lighting was used, the diamond bur presented higher mean and maximum depth values. CONCLUSIONS: Fluorescence lighting facilitated the removal of remnant resin composite dental trauma splints, leading to less invasive treatment. The diamond bur resulted in higher enamel damage than that affected by the multifluted bur when no violet lighting was used. A low-cost violet flashlight is a useful fluorescence-aided identification technique for removing resin composite dental trauma splints.

Effect of different materials for conventional and 3D-printed models on the mechanical properties of ethylene-vinyl acetate utilized for fabricating custom-fit mouthguards.

BACKGROUND/AIM: The interaction between the ethylene-vinyl acetate (EVA) with distinct materials utilized for obtaining dental models can affect the performance of resulting mouthguards. This study attempted to evaluate the effect of different materials for conventional (dental stone) or 3D-printed (resin) models on EVA's physical and mechanical properties and surface characteristics. MATERIAL AND METHODS: EVA sheets (Bioart) were laminated over four model types: GIV, conventional Type IV dental stone model (Zhermak); ReG, resin-reinforced Type IV dental stone model (Zero Stone); 3DnT, 3D resin printed model (Anycubic) without surface treatment; 3DT, 3D-printed model (Anycubic) with water-soluble gel (KY Jelly Lubricant, Johnson & Johnson) coating during post-curing process. The EVA specimens were cut following the ISO 37-II standard (n = 30). Shore A hardness was measured before and after plasticization on the contact (internal) or opposite (external) surfaces with the model. The breaking force (F, N), elongation (EL, mm), and ultimate tensile strength (UTS, MPa) were measured using a universal testing machine. Macro-photography and scanning electron microscopy were adopted for classifying the EVA surface alteration. Data were analyzed by one-way ANOVA with repeated measures, followed by Tukey's test (α = .05). RESULTS: Plasticization significantly decreased Shore A values for the tested EVA regardless of the model type (p < .001). Higher F, El, and UTS values were verified for the EVA with 3DT and GIV models compared to ReG and 3DnT (p < .001). 3DnT models resulted in severe surface alteration and a greater reduction of the mechanical properties of the EVA. CONCLUSION: The interaction of EVA with 3D resin-printed models without surface treatment or resin-reinforced Type IV dental stone models significantly affected the physical and mechanical properties of this material. The utilization of water-soluble gel coating during the post-curing process of 3D resin printed models improved the mechanical properties of the EVA, similarly when this material was plasticized over conventional Type IV dental stone model.

Effect of surface treatment of ethylene vinyl acetate on the delamination of custom-fitted mouthguards.

BACKGROUND/AIM: Contamination of ethylene vinyl acetate (EVA) during mouthguard fabrication can cause delamination. The study evaluated the effects of different EVA surface treatments on the contact angle, laminate bond strength, and elongation capacity. MATERIALS AND METHODS: Specimens of two bonded EVA plates were prepared (n = 30). The Shore A hardness of standardized EVA plate specimens was measured before and after thermo-plasticization. The EVA plates were randomly allocated to one of five different surface treatment groups: no treatment (control); isopropyl alcohol, 100%; chloroform, 99.8%; self-cure acrylic resin monomer (methacrylate, ethylene glycol dimethacrylate, and chemical initiator-amine type); and ethyl alcohol, 70%. The maximum breaking force and elongation at the site of fracture were recorded using a universal testing machine. The contact angle surface was measured using ImageJ software. Scanning electron microscopy of the EVA surface was performed. The laminate bond strength was obtained by dividing the maximum breaking force by the bonding area between the two EVA plates. The laminate bond strength and maximum elongation data were analyzed by one-way ANOVA, followed by the Tukey's and the Dunnet test. The failure mode data was analyzed using the chi-square test (α = .05). RESULTS: EVA surface treatment significantly influenced the laminate bond strength and maximum elongation (p < .001). The control group had a higher contact angle and significantly lower laminate bond strength and maximum elongation than the other groups (p < .001). The acrylic resin monomer and chloroform-treated specimens had similar laminate bond strength and maximum elongation. The acrylic resin monomer group had a significantly lower contact angle (p < .001). CONCLUSIONS: All treatments had a significantly higher laminate bond strength and maximum elongation than the control group. The acrylic resin monomer and chloroform groups had a significantly higher laminate bond strength and maximum elongation and the acrylic resin monomer group had a lower contact angle than the other groups. The chloroform should be avoided due its hazardous effects.

Photobiomodulation effect of red LED (630 nm) on the free radical levels produced by pulp cells under stress conditions.

The aim of this study was to assess the ability of red light emitting diodes (LED) to modulate oxidative stress in human dental pulp fibroblasts (HDPFs) when different irradiation parameters are employed. Cells from primary teeth were seeded (100,000 cells/well) in 24-well plates in culture medium (DMEM). At 24 h after incubation, the culture medium was replaced with DMEM containing 10 µg/mL lipopolysaccharide (LPS). Thereafter, the cells were irradiated (LED 630 nm, 0.04 W/cm2 and 0.08 W/cm2) at 0 J/cm2 (control group), 4 J/cm2, 15 J/cm2, and 30 J/cm2; and their viability (MTT assay), number (Trypan Blue), synthesis of nitric oxide (NO) (Griess reagent), and reactive oxygen species (ROS) (fluorescence probe, DCFH-DA) were assessed. The Kruskal-Wallis and Mann-Whitney statistical tests using Bonferroni correction were employed (significance level of 5%). Compared to that in control fibroblasts, increased viability was observed in HDPFs exposed to LPS and irradiated with 15 J/cm2 and 30 J/cm2 at 0.04 W/cm2 and 4 J/cm2 and 15 J/cm2 at 0.08 W/cm2 (p < 0.05). Exposure to 4 J/cm2 at 0.04 W/cm2 and 15 J/cm2 and 30 J/cm2 at 0.08 W/cm2 modulated the oxidative stress in cells relative to that observed in non-irradiated LPS-treated pulp cells (p < 0.05). It was concluded that the irradiation strategies of using red LED with radiant exposures of 15 J/cm2 and 30 J/cm2 at 0.04 W/cm2 and 15 J/cm2 at 0.08 W/cm2 were the best parameters to decrease NO and ROS concentration and to stimulate viability of HDPFs exposed to LPS challenge.

Does polishing of bleached enamel affect roughness and tooth color stability after exposure to coffee?

OBJECTIVE: This laboratory randomized study was designed to evaluate the effect of polishing on roughness and color stability of bleached teeth after coffee immersion. MATERIALS AND METHODS: Ninety bovine crowns were randomly allocated to six groups (n = 15), according to bleaching protocols: At-home: standard protocol using 10% hydrogen peroxide (HP) or In-office: standard protocol using 35% HP; and with polishing protocols: (1) no polishing, (2) bleached enamel polished with #0.5 µm or (3) #2-4 µm diamond particles grit pastes. Samples were daily immersed into coffee solution for 45 min followed by mechanical brushing simulation (30 s) for 30 days. The surface roughness (Ra) and color alteration, expressed by ΔEab , ΔE00 , and whitening index (WI) were analyzed at baseline, after bleaching/polishing protocols and after coffee solution staining. The surface from each group was examined using a scanning electron microscope. Data were analyzed by two-way repeated measure analysis of variance followed by the Tukey test (α = 0.05). RESULTS: Staining increases Ra, ΔEab , ΔE00 , and decreases WI values. Polishing after bleaching did not prevent staining, however, tooth polished with #0.5 µ-grit polishing paste showed better performance than #2-4 µ-grit (ΔEab : p = 0.001/ΔE00 : p = 0.003). Scanning electron microscope revealed a more irregular surface after coffee staining for all groups regardless bleaching/polishing protocols. CONCLUSIONS: Using #0.5 µ-grit diamond paste to polish 35%HP in-office bleached enamel reduces the roughness and tooth staining. However, polishing after 10%HP at-home bleached enamel neither affects roughness nor improves tooth color stability after exposure to coffee. CLINICAL SIGNIFICANCE: Polishing after at-home bleaching does not have benefits but after 35% hydrogen peroxide in-office bleaching, the polishing with #0.5 µ-grit polishing paste is indicated to reduce roughness and the tooth staining over time.

Dental trauma splints for the mixed dentition - A finite element analysis of splint material, splint extension, missing teeth, and PDL representation.

BACKGROUND/AIMS: Dental traumatic injuries are common in children during the mixed dentition stage. These injuries usually require splinting for stabilization, which is complicated by the various stages of the permanent tooth development and primary tooth exfoliation. The aim of this study was to evaluate the effect on mobility of splint materials and extensions for an avulsed central incisor, stabilized with and without the adjacent incisor under intrusive and extrusive loading with different periodontal ligament (PDL) conditions. MATERIALS AND METHODS: Seventeen 3D model variations were created from a CBCT scan of a 7-year-old patient without erupted permanent upper lateral incisors. A 1000 N palatal load on the right central incisor simulated the avulsion injury and created an increased alveolus and bone deformation, resulting in an increased PDL thickness of 0.45 mm. Wire-resin composite splints with 0.9 mm cross-section (WCS) or 1.0 mm diameter nylon-resin composite splints (NCS) were created. The models simulated conditions with and without the adjacent upper central incisor. Two PDL conditions were investigated, simulating detached PDL or PDL with polyether impression material-like properties. Mobility was calculated under simulated biting loads in horizontal and vertical (intrusive and extrusive) directions. RESULTS: The NCS allowed greater tooth mobility of the avulsed incisor than the WCS, irrespective of splint extension, PDL condition, or load application. During horizontal loading, polyether-like properties for the PDL allowed around 0.2 mm mobility of the avulsed tooth with the WCS, similar to the intact tooth, whereas a simulated detached PDL allowed 25% more mobility with a WCS than with a NCS. CONCLUSIONS: Based on the FEA analysis, a 1.0 mm NCS may be suitable for splinting avulsion injuries during the mixed dentition stage compared to the considerably more rigid WCS. The NCS models provided flexibility for PDL healing while maintaining stability, even when missing adjacent teeth increased span widths. Extensions beyond directly adjacent teeth did not alter the mobility with the NCS but should still be considered an extra protection in case of bond failure or exfoliation.

Effect of the violet light from polywave light-polymerizing units on two resin cements that use different photoinitiators.

STATEMENT OF PROBLEM: Some light-emitting diode polymerization lights have been promoted as multiple peak or polywave lights that use multiple light-emitting diodes to produce both violet and blue light. However, whether the addition of violet light is required to light-activate resin cements that use bis(4-methoxybenzoyl)diethylgermane (Ivocerin) as the photoinitiator is unclear. PURPOSE: This in vitro study evaluated the effect of violet, blue, or a combination of violet and blue light through ceramic on the degree of conversion of 2 resin cements that use either camphorquinone or Ivocerin as the photoinitiator. MATERIAL AND METHODS: A Bluephase Style polywave light-emitting diode polymerizing unit delivering 6.4 J/cm2 of violet and blue light was used. This comprised 1.4 J/cm2 of violet (385 to 420 nm) and 5.0 J/cm2 of blue light (420 to 515 nm). The light-emitting diode emitters in a second modified Bluephase Style were connected directly to a power supply so that either just violet (1.4 J/cm2) or just blue (5.0 J/cm2) light was emitted. RelyX Veneer and Variolink Esthetic LC resin cements were either directly light-activated or through 0.5 or 1.5 mm of lithium disilicate ceramic (IPS e.max CAD). The degree of conversion was monitored by using Fourier-transform infrared spectroscopy. Data were subject to a 3-way analysis of variance followed by the Tukey honest significant difference multiple comparison tests (α=.05). RESULTS: All factors had a significant effect (P<.001). Increasing the ceramic thickness decreased the degree of conversion only for RelyX Veneer cement (P<.001). The effect of the thickness of ceramic was most noticeable when just violet light was delivered to RelyX Veneer. A significant reduction (P<.001) was found in the degree of conversion of RelyX Veneer when just violet light was delivered. Variolink Esthetic LC had significantly higher degree of conversion values than RelyX Veneer, irrespective of the light type used (P<.001). CONCLUSIONS: A multiple-peak light is not required to photopolymerize a resin cement that uses either camphorquinone or Ivocerin as its photoinitiator. Adding the violet light produced no significant increase in the degree of conversion of the Variolink Esthetic LC cement.

Splint stiffness and extension effects on a simulated avulsed permanent incisor-A patient-specific finite element analysis.

BACKGROUND/AIM: Splinting is an important procedure after avulsion. However, the role of splint stiffness and extension is not fully understood. The aim of this study was to evaluate the effect of splint stiffness and extensions on the mobility and stress on an injured tooth under physiological biting load. MATERIALS AND METHODS: Three-dimensional (3D) finite element models were created from a cone beam computer tomogram of a patient with normal occlusion. An avulsion injury of the right central incisor was created with a 1000 N load application on the palatal of the injured tooth, causing increased socket width. Splints made from four materials were tested: 0.9 mm diameter wire-composite splint (WCS1), 0.4 mm diameter wire-composite splint (WCS2), 1.0 mm diameter nylon-composite splint (NCS), and a 2 mm high by 0.2 mm thick plastic strip composite splint (PSS). Three splint extensions (involving 6, 5, and 3 teeth) were evaluated. Mobility of the avulsed tooth and the maximum principal stress distributions in the adjacent teeth were calculated. RESULTS: The injured incisor tooth mobility was not affected by the splint extensions. The NCS and PSS stabilized the avulsed incisor but allowed, respectively, 10 and 20 times more mobility under horizontal loading than the WCS1, which inhibited most mobility, while the WCS2 allowed double the mobility compared with WCS1. The NCS and PSS allowed more tooth mobility, mainly in the extrusion direction. Splints were 2-3 times more effective in limiting mobility under intrusive loads than extrusive loads. High levels of stress were found at the base of the composite attachments in the adjacent incisors. CONCLUSION: Splinting an avulsed tooth to one or two teeth bilaterally using a nylon splint or a plastic strip is appropriate for tooth stabilization and should be recommended over the 0.4mm wire-composite splint, while the 0.9 mm orthodontic wire is too rigid and not recommended.

Effect of luting materials, presence of tooth preparation, and functional loading on stress distribution on ceramic laminate veneers: A finite element analysis.

STATEMENT OF PROBLEM: How the polymerization shrinkage, loading, and mechanical properties of luting materials affect the shrinkage and functional stresses in ceramic laminate veneers (CLVs) with and without tooth preparation is unclear. PURPOSE: The purpose of this finite element analysis (FEA) study was to evaluate the effect of the polymerization shrinkage, functional loading, and mechanical properties of different luting materials on the stresses in ultrathin 0.3-mm CLVs with and without tooth preparation. MATERIAL AND METHODS: Three resin cements, RelyX Veneer (RV), Allcem Veneer APS (AV), Variolink Esthetic LC (VE), and 1 flowable composite resin, Tetric N-Flow (TF), were tested for post-gel shrinkage (Shr), Knoop hardness (KHN), elastic modulus (E), compressive strength (CS), and diametral tensile strength (DTS). IPS e.max CAD disks of 0.3-mm thickness were made for simulating the effects of light attenuation. Eight 2-dimensional finite element models (Marc-Mentat) of a maxillary central incisor were generated to evaluate the polymerization shrinkage stress of different materials for luting 0.3-mm CLVs with or without tooth preparation and the stress during functional loading by using a modified von Mises criterion (mvm). Collected data from Shr, KHN, and E were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). RESULTS: Light attenuation by the 0.3-mm ceramic disk did not significantly affect the E values, but Shr was significantly lower in VE (26%) and TF (35%). TF had lower volumetric Shr (%) when interposing a ceramic disk (0.31%). Both tested tooth preparation options showed similar stress distributions from polymerization shrinkage or functional loading, with higher stress concentration on the incisal edge and also on the cervical surface. The model featuring tooth preparation and RV resin cement had the highest and VE the lowest stress levels. CONCLUSIONS: The flowable composite resin had similar mechanical properties as the resin cements. The stress distribution from shrinkage and functional loading was similar for both techniques with or without tooth preparation.

Influence of ceramic veneer thickness and antagonist on impact stresses during dental trauma with and without a mouthguard assessed with finite element analysis.

BACKGROUND/AIM: Little is known about the effect of dental trauma and mouthguards (MG) on teeth with ceramic laminate veneers (CLV). The aim was to evaluate the influence of CLV thickness and the presence of a MG with and without antagonist tooth contact on impact stresses during dental trauma. MATERIALS AND METHODS: Twelve 2D-finite element models of a head with maxillary structures and upper incisors, six with and six without antagonist tooth, were created in three CLV conditions: sound incisor (no CLV), 0.3 mm CLV, and 1.0 mm CLV. These were evaluated with and without a 4.0-mm ethylene-vinyl acetate MG, with and without an antagonist tooth. An impact analysis was performed in which the head frontally hits a rigid surface at a speed of 1 m/s (3.6 km/h). The results were analyzed using Critical modified von Mises (MPa). The mean of the 10% highest modified von Mises stresses in each structure was collected. RESULTS: MG presence substantially reduced impact stresses in the CLV and tooth structures. The contact of the antagonist tooth promoted better stress distribution and reduced the stress levels in the traumatized tooth. Critical stress areas were found in the palatal enamel, incisal enamel, labial cervical area, and enamel under the CLV for all models without MG. In the models with MG, the stresses reduced significantly. Critical modified von Mises stress showed that sound or prepared enamel experienced more critical impact stresses than 0.3 or 1.0-mm thick CLV. CONCLUSIONS: The use of 4.0 mm EVA mouthguard reduced the impact stress levels in models with 0.3-mm CLV and 1.0-mm CLV, similar to a sound tooth. The contact of an antagonist tooth and the MG better distributed the stresses and reduced the impact stress in the traumatized tooth.

Fractured alveolar process displacement evaluation-Effect of the rigidity of wire-composite splints.

BACKGROUNDS/AIMS: Traumatic dental injuries with bone fractures require rigid splinting. The degree of rigidity of the wire-composite splints can be challenging. The aim of this study was to evaluate the effect of the rigidity of different wire-composite splints on alveolar process displacement. MATERIAL AND METHODS: A model was created using polystyrene resin to simulate the anterior maxilla, bovine incisors to simulate maxillary incisors, and polyether impression material to simulate the periodontal ligament. An alveolar process fracture was created, while maintaining the labial bone connection with the PDL. Four wire-composite splints (0.3, 0.6, 0.9, and 1.2 mm in diameter) were compared with models without splints and with no fracture (n = 5). The alveolar process displacement was measured (3 times per model/per splint type) at the fractured and adjacent central incisor regions using a deflectometer (Instron) under functional cycling and static loading (100 N). Data (µm) were analyzed using RM ANOVA, followed by Tukey's HSD test (α = 0.05). RESULTS: The displacement at the region of the adjacent incisor was not influenced by the splint during static and cycling load (P > .05). The Tukey test demonstrated that the model without splints had significantly higher alveolar process displacement at the traumatized teeth than that of all other splint models (P < .001). Increasing the wire diameter from 0.3 mm to 0.9 mm significantly reduced the alveolar process displacement (P < .001). No difference was observed between the 0.9 mm (P = .123) and 1.2 mm (P = .219) wire-composite splints irrespective of the measured tooth regions. CONCLUSIONS: The rigidity of the wire-composite splint significantly influenced the mobility of the fractured alveolar process. The use of at least 0.9 mm wire was effective in reducing the fractured alveolar process displacement to a level that was similar to the adjacent teeth.

Chemical analysis of in vivo-irradiated dentine of head and neck cancer patients by ATR-FTIR and Raman spectroscopy.

OBJECTIVES: To evaluate the effect of in vivo radiotherapy on the chemical properties of human dentine by Fourier-transform infrared spectroscopy (FTIR) and Raman analysis. MATERIALS AND METHODS: Chemical composition was evaluated comparing control and irradiated group (n = 8). Irradiated teeth were obtained from radiotherapy patients subjected to fractionated X-ray radiation of 1.8 Gy daily totaling 72 Gy. The teeth were sectioned according to the type of dentine (crown or root dentine), obtaining 3-mm dentine cervical slices. The analyzed parameters by FTIR and Raman spectroscopies were mineral/matrix ratio (M:M), carbonate/mineral ratio (C:M), amide I/amide III ratio, and amide I/CH2 ratio. Raman also calculated the phosphate and carbonate crystallinity. RESULTS: FTIR revealed that M:M had a decrease in both factors (p = 0.008; p = 0.043, respectively) and root dentine showed a lower C:M in the irradiated group (p = 0.003). Raman revealed a higher phosphate crystallinity and a lower carbonate crystallinity in crown dentine of irradiated group (p = 0.021; p = 0.039). For amide I/amide III, the irradiated showed a lower ratio when compared to the control group (FTIR p = 0.002; Raman p = 0.017). For amide I/CH2, the root dentine showed a higher ratio than the crown dentine in both methods (p < 0.001). CONCLUSIONS: Radiotherapy altered the chemical composition of human dentine. The exchange of phosphate-carbonate ions in the hydroxyapatite and higher concentration of organic components was found after radiotherapy. CLINICAL RELEVANCE: The increased risk of radiation-related caries in patients undergoing head and neck radiotherapy is due not only to salivary, dietary, and microbiological changes but also to changes in tooth chemical composition.

Effect of ionizing radiation after-therapy interval on bone: histomorphometric and biomechanical characteristics.

OBJECTIVES: This study aimed to evaluate the effects of radiotherapy on biomechanical, histomorphometric, and microstructural characteristics of bone, in diverse periods, compared with intact bone tissue. MATERIALS AND METHODS: Eighteen adult male New Zealand rabbits were treated with a single radiation dose of 30 Gy. The animals were randomly divided into six groups: NoIr, control group, no radiation, and five irradiated groups sacrificed after 24 h (Ir24h), 7 (Ir7d), 14 (Ir14d), 21 (Ir21d), and 28 (Ir28d) days. After these periods, the animals were sacrificed and their tibias (n = 6) evaluated using three-point bending test to calculate the ultimate force, work to failure, and bone stiffness. Dynamic indentation test was used to quantify Vickers hardness and elasticity modulus of bone tissue. Micro-CT was used to analyze the cortical volume (CtV), cortical thickness (CtTh), and porosity (Ct.Po). Histomorphometric assessment was based on the lacunarity of bone tissue. Data were analyzed using one-way ANOVA and Kruskal-Wallis tests followed by Tukey, Dunnet, and Dunn's post-tests (P < 0.05). RESULTS: The ultimate force, work to failure, stiffness, elastic modulus, and Vickers hardness values of irradiated bone were significantly lower that non-irradiated bone. Irradiated bone showed significantly lower CtTh and CtV values and higher CtPo than non-irradiated bone. No significant difference was found for lacunarity between non-irradiated bone and irradiated bone. CONCLUSIONS: Ionizing radiation decreases normal anisotropy on microarchitecture of cortical bone, and increases bone fragility compared with non-irradiated bone. Further, these changes were seen after longer periods (e.g., 14 and 21 days), and not immediately after radiation therapy. CLINICAL RELEVANCE: The radiotherapy reduces bone mechanical properties and the normal structure of organic and inorganic bone matrix. For studying the protocols to protect the radiotherapy effect using rabbit model, the use of the sacrificing period between 14 and 21 days is recommended.

Biomechanical Effect of Ferrule on Incisors Restored with a Fiberglass Post and Lithium-Disilicate Ceramic Crown after Thermal Cycling and Fatigue Loading.

PURPOSE: To evaluate the biomechanics of endodontically treated incisors restored with a fiberglass post and a CAD/CAM lithium-disilicate ceramic crown with/without a ferrule after thermal and mechanical aging. MATERIALS AND METHODS: Twenty bovine incisors were divided into two groups (n = 10): 1. Fe, with a ferrule of 2 mm, and 2. NFe, without a ferrule. After endodontic treatment, the teeth were restored using a fiberglass post (Exacto 3, Angelus) and composite core (Tetric Ceram, Ivoclar Vivadent). They then received a CAD/CAM lithium-disilicate ceramic crown (IPS e.max CAD) luted using a self-adhesive composite (RelyX Unicem 2, 3M Oral Care). All specimens were subjected to 20,000 thermocycles and 2,400,000 simulated chewing cycles. Ceramic crown and root dentin strains (µS) were measured using strain gauges (n = 10) during 100-N loading before and after the thermal and mechanical aging, and upon fracture loading. The specimens were subsequently loaded to fracture (N). The stress distribution was analyzed using 3D individualized finite-element models created by micro-CT of experimental samples (n = 3). Strain data were analyzed using two-way ANOVA and Tukey's HSD test. Fracture resistance was analyzed using Student's t-test and fracture mode was analyzed using the chi-squared test (α = 0.05). RESULTS: After aging, NFe exhibited significantly higher root dentin deformation (buccal: 1248.0 ± 282.8; lingual: 516.2 ± 195.0; p < 0.001) than Fe (buccal, 554.0 ± 233.8; lingual: 311.8 ± 159.0; p < 0.001). The deformation measured on ceramic crowns was not influenced by ferrule presence or aging process. Significantly higher fracture resistance (N) was observed for the Fe (1099.6 ± 214.8) than the NFe group (675.3 ± 113.8) (p < 0.001). The NFe group revealed a lower fracture resistance:root strain ratio than did the Fe group. The stress levels on root dentin and fiberglass were lower for the Fe group. CONCLUSION: The NFe group showed increased root dentin strain after the aging process. The Fe group revealed higher fracture resistance, lower stress concentration on root dentin and fewer catastrophic fractures.

The effect of dental treatment on oral health-related quality of life in adolescents.

OBJECTIVES: The objective of the study is to assess the effect of dental treatment on the oral health-related quality of life (OHRQoL) of adolescents from a city in South Brazil. MATERIALS AND METHODS: This longitudinal study included 129 adolescents aged 10 to 15 years who received dental caries treatment in a university clinic in Santa Maria, Brazil. The OHRQoL was measured using the Brazilian version of the Child Perceptions Questionnaire for children aged 11 to 14 years (CPQ11-14). The questionnaire was administered through face-to-face interviews before treatment and 1 month after its completion. Paired t tests and effect sizes were used to evaluate changes in CPQ11-14 scores after completion of treatment. RESULTS: In total, 43.4% of the study participants received solely restorations, 15.5% received endodontic treatment, and 44.2% underwent tooth extractions. The mean CPQ11-14 score before treatment was 15.9 ± 10.3, which decreased to 6.3 ± 6.5 after treatment (P < 0.001). The same pattern was observed in the four domains of CPQ11-14 (oral symptoms, functional limitation, emotional well-being, and social well-being). The effect sizes varied from 0.4 to 1.1, with oral symptoms and emotional well-being domains showing the greatest changes. CONCLUSIONS: Dental treatment resulted in a significant improvement in the OHRQoL of the evaluated adolescents. CLINICAL RELEVANCE: Providing dental treatment has beneficial effects on the quality of life of adolescents, especially for oral symptoms and emotional well-being.

Influence of radiotherapy on the dentin properties and bond strength.

OBJECTIVES: The objective of this study was to evaluate the biomechanical properties of dentin and the microtensile bond strength (µTBS) performed before or after radiotherapy (RT). MATERIAL AND METHODS: Dentin chemical composition (infrared spectroscopy-FTIR), SEM images, and mechanical properties (Vickers microhardness-VHN and elastic modulus-E) were evaluated comparing no irradiated and irradiate dentin (n = 5). RT was defined by application of 72 Gy (1.8 Gy daily, 5 days per week, during 8 weeks) with sample immersed in distilled water. µTBS evaluated three groups (n = 10): NI-no irradiated; IB-irradiation before restoration; and IA-irradiation after restoration. Resin-dentin sticks (1.0 mm2) were obtained and submitted to µTBS. Analysis of the bonding interface was made by confocal microscopy. RESULTS: After RT, percentage ratio of FTIR analysis showed increased absorption for all bands. SEM image showed a disorganized dentin structure. Two-way ANOVA showed increased VHN (p = 0.005) and decreased E (p < 0.001). For µTBS, one-way ANOVA and Duncan test showed significant differences among groups (p = 0.018). IB group presented the lowest bond strength values. CONCLUSIONS: RT alters the absorption bands and SEM images showed a disorganization of the dentin structure. Mechanical properties were changed with increased VHN and decreased E. µTBS was affected by the radiotherapy and restoration period (before or after). CLINICAL RELEVANCE: RT causes changes that contribute to increased risk of tooth decay. Restorative treatments can be performed using adhesive procedures, but it is preferable to be performed before of the irradiation protocol, to guarantee better adhesive properties to restoration.

Replanted teeth stored in a newly developed powdered coconut water formula.

BACKGROUND/AIM: A newly developed powdered coconut water formulae (ACP-404) has been proposed to preserve periodontal ligament cell viability. The aim of this study was to investigate the periodontal healing of dog teeth replanted after storage in ACP-404 with 2 different osmolalities. MATERIALS AND METHODS: Sixty teeth of 10 adult beagle dogs were extracted and randomly subjected to the following protocols: immediate replantation after extraction (positive control); dry conditions (negative control); and storage in ACP-404 I (G1), ACP-404 II (G2), in coconut water long shelf life (G3) or in pH-neutralized coconut water long shelf life (G4) for 50 minutes before replantation. The animals were euthanized 28 days post-operatively and processed for histomorphometric analysis using an optical microscope. The groups were subjected to histomorphometric analysis compared with immediate replantation and dry conditions. The data were statistically analysed using the Kruskal-Wallis test with post-analysis using Dunnett's test. RESULTS: The normal periodontal area was significantly higher for the G1 than for the G2 and G3 groups (P < .001). The positive control group presented similar normal periodontal areas compared to the experimental groups, except for the G3 and negative control groups (P < .001). G1 presented the lowest level of external root replacement resorption compared to the other groups (P < .05). All storage solutions had similar periodontal conditions for repaired resorption areas, inflammatory root resorption, ankylosis and replacement resorption (P > .05). CONCLUSIONS: ACP-404 I (G1) was better overall and was able to preserve the normal periodontium and had less external root replacement resorption.