Adaptation and Biomechanical Performance of Custom-Fit Mouthguards Produced Using Conventional and Digital Workflows: A Comparative In Vitro Strain Analysis.

BACKGROUND/OBJECTIVES: The use of different models for the fabrication of custom-fit mouthguards (MTGs) can affect their final thickness, adaptation, and shock-absorption properties. This study aimed to evaluate the adaptation, thickness, and shock absorption of ethylene-vinyl acetate (EVA) thermoplastic MTGs produced using conventional plaster or three-dimensional (3D) printed models. MATERIALS AND METHODS: A typical model with simulated soft gum tissue was used as the reference model to produce MTGs with the following two different protocols: plast-MTG using a conventional impression and plaster model (n = 10) and 3DPr-MTG using a digital scanning and 3D printed model (n = 10). A custom-fit MTG was fabricated using EVA sheets (Bioart) plasticized over different models. The MTG thickness (mm), internal adaptation (mm) to the typodontic model, and voids in the area (mm2) between the two EVA layers were measured using cone-beam computed tomography images and Mimics software (Materialize). The shock absorption of the MTG was measured using a strain-gauge test with a pendulum impact at 30° with a steel ball over the typodont model with and without MTGs. Data were analyzed using one-way analysis of variance with repeated measurements, followed by Tukey's post hoc tests. RESULTS: The 3DPr-MTG showed better adaptation than that of the Plast-MTG at the incisal/occlusal and lingual tooth surfaces (p < 0.001). The 3DPr-MTG showed a thickness similar to that of the Plast-MTG, irrespective of the measured location. MTGs produced using both model types significantly reduced the strain values during horizontal impact (3DPr-MTG 86.2% and Plast-MTG 87.0%) compared with the control group without MTG (p < 0.001). CONCLUSION: The MTGs showed the required standards regarding thickness, adaptation, and biomechanical performance, suggesting that the number and volume of voids had no significant impact on their functionality. Three-dimensional printed models are a viable alternative for MTG production, providing better adaptation than the Plast-MTG at the incisal/occlusal and lingual tooth surfaces and similar performance as the MTG produced with the conventional protocol.

Impact of adenotonsillectomy and palatal expansion on the apnea-hypopnea index and minimum oxygen saturation in nonobese pediatric obstructive sleep apnea with balanced maxillomandibular relationship: A cross-over randomized controlled trial.

OBJECTIVE: To determine the impact and best management sequence between adenotonsillectomy (AT) and rapid palatal expansion (RPE) on the apnea-hypopnea index (AHI) and minimum oxygen saturation (MinSaO2) in nonobese pediatric obstructive sleep apnea (OSA) patients presenting balanced maxillomandibular relationship. STUDY DESIGN/METHODS: Thirty-two nonobese children with balanced maxillomandibular relationship and a mean age of 8.8 years, with a graded III/IV tonsillar hypertrophy and maxillary constriction, participated in a cross-over randomized controlled trial. As the first intervention, one group underwent AT while the other underwent RPE. After 6 months, interventions were switched in those groups, but only to participants with an AHI > 1 after the first intervention. OSA medical diagnosis with the support of Polysomnography (PSG) was conducted before (T0), 6 months after the first (T1) and the second (T2) intervention. The influence of sex, adenotonsillar hypertrophy degree, initial AHI and MinSaO2 severity, and intervention sequence were evaluated using linear regression analysis. Intra- and intergroup comparisons for AHI and MinSaO2 were performed using ANOVA and Tukey's test. RESULTS: The initial AHI severity and intervention sequence (AT first) explained 94.9% of AHI improvement. The initial MinSaO2 severity accounted for 83.1% of MinSaO2 improvement changes. Most AHI reductions and MinSaO2 improvements were due to AT. CONCLUSIONS: Initial AHI severity and AT as the first intervention accounted for most of the AHI improvement. The initial MinSaO2 severity alone accounted for the most changes in MinSaO2 increase. In most cases, RPE had a marginal effect on AHI and MinSaO2 when adjusted for confounders.

Mechanical properties of dual-polymerizing resin-core material, dual-polymerizing resin cement, and bulk-fill composite resin used for restoring endodontically treated teeth.

STATEMENT OF PROBLEM: How resin-based material and a light-activation protocol influence the mechanical properties of materials used to cement glass fiber post-and-cores in endodontically treated teeth is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the influence of immediate or 5-minute delayed light activation on the mechanical properties of dual-polymerizing resin cements and dual-polymerizing resin-core materials compared with bulk-fill composite resins. MATERIAL AND METHODS: Nine resin-based materials were tested: 4 dual-polymerizing resin-core materials, (Allcem Core; FGM, LuxaCore Z; DMG, Rebilda DC; VOCO, and (Clearfil DC Core Plus; KURARAY), 3 dual-polymerizing resin cements, (RelyX Universal; 3M ESPE, RelyX U200; 3M ESPE, and Allcem Dual; FGM), and 2 bulk-fill composite resins, (Opus Bulk Fill APS; FGM, and Filtek One Bulk Fill; 3M ESPE). The dual-polymerizing materials were light activated using both protocols. The postgel shrinkage (Shr), flexural strength (FS), elastic modulus (E), Knoop hardness (KH), degree of conversion (DC), and depth of polymerization (DoP) were measured (n=10). The data for Shr, FS, E, and DoP were analyzed using 2-way ANOVA, and for KH and DC using 2-way repeated measurement ANOVA and the Tukey HSD test (α=.05). RESULTS: A 5-minute delay before light-activation significantly reduced Shr for all materials (P<.001). Increasing the depth significantly reduced the KH for all materials (P<.001). Bulk-fill composite resins and dual-polymerizing resin-core had higher KH values than dual-polymerizing resin cements (P<.001). CONCLUSIONS: Delayed 5-minute light-activation reduced postgel shrinkage and had no negative effect on mechanical properties. Dual-polymerizing resin-core materials exhibited higher KH values than dual-polymerizing resin cement and mechanical properties similar to those of bulk-fill composite resin.

Biomechanical behavior of three maxillary expanders in cleft lip and palate: a finite element study.

This study evaluated the stress distribution in the dentoalveolar and palatal bone structures during maxillary expansion in a 17-year-old male patient with bilateral cleft lip and palate (BCLP) using expanders with dental (HYRAX) and skeletal anchorage (MARPE). For the generation of the specific finite element models, cone-beam computed tomography was used, and the DICOM files were exported to Mimics 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: conventional four-banded hyrax screw (9 mm); B) MARPE-DS: 3 miniscrews (1.8 mm diameter - 5.4 mm length) and four-banded dental anchorage; and C) MARPE-NoDS: 3 miniscrews without dental anchorage. Maxillary expansion was simulated by activating the expanders transversely 1 mm on the "X" axis. HYRAX resulted in higher levels of deformation predominantly in the dentoalveolar region. MARPE-DS showed stress in the dentoalveolar region and mainly in the center of the palatal region, at approximately 4,000 µÎµ. MARPE-NoDS exhibited evident stress only in the palatal region. High stress levels in the root anchoring teeth were observed for HYRAX and MARPE-DS. In contrast, MARPE-NoDS cause stress on the tooth structure. The stress distribution from the expanders used in the BLCP showed asymmetric expansive behavior. During the initial activation phase of expansion, the HYRAX and MARPE-DS models produced similarly high strain at the dentoalveolar structures and upper posterior teeth displacement. The MARPE-NoDS model showed restricted strain on the palate.

Effect of four different mono and multi-wave light-curing units on the Knoop hardness of veneer resin composites.

OBJECTIVES: To evaluate the effect of mono and multi-wave light-curing units (LCUs) on the Knoop hardness of resin-based composites (RBC) that use different photoinitiators. METHODS: Central incisor-shaped specimens 12 mm long, 9 mm wide, and 1.5 mm thick were made from 2 RBCs that use different photoinitiators: Tetric N-Ceram (Ivoclar Vivadent) - and Vittra APS (FGM), both A2E shade. They were light-cured with 4 different LCUs: two claimed to be multi-wave - VALO Grand (Ultradent) and Emitter Now Duo (Schuster); and two were monowave - Radii Xpert (SDI) and Elipar DeepCure-L (3 M Oral Care) using 2 different light exposure protocols: one 40 s exposure centered over the specimen; and two 20 s light exposures that delivered light from two positions to better cover the entire tooth. 16 groups with 10 specimens in each group were made. The Knoop hardness (KH, kg/mm2) was measured at the top and bottom of the specimen in the center and at the cervical, incisal, mesial, and distal peripheral regions. The active tip diameters (mm) and spectral radiant powers (mW/nm) of the LCUs were measured with and without the interposition of the RBC, as well as the radiant exposure beam profiles (J/cm²) delivered to the top of the RBCs. The data was analyzed using Three-way ANOVA and Tukey's tests (α = 0.05). RESULTS: The VALO Grand (1029 mW) emitted twice the power of the Radii Xpert (500 mW). The KH values of VI and TN resin composite specimens were significantly affected by the LCU used (p < .001), the measurement location (p < .001), and the surface of the specimen (p < .001). LCUs with wider tip diameters produced greater Knoop hardness values at the peripheries of the 12 mm of long, 9 mm wide specimens. In general, the VALO Grand produced the highest KH values, followed by Elipar DeepCure-L, then by Radii Xpert. The Emitter Now Duo LCU produced the lowest values. Exposing the veneers from two locations reduced the differences between the LCUs and the effect of the measurement location. Only the VALO Grand could fully cover the composite veneer with light when the two locations were used. SIGNIFICANCE: The light tip must cover the entire restoration to photocure the RBC beneath the light tip.

Radiotherapy in the head and neck region influences the chemical and mechanical properties of intraradicular dentin.

OBJECTIVES: To investigate the chemical and mechanical properties of intraradicular dentin submitted to radiotherapy. MATERIALS AND METHODS: Sixteen mandibular incisors were divided into two groups (n = 8): non-irradiated and irradiated. The irradiated teeth were obtained from head and neck radiotherapy patients, with a total dose ranging from 70.2 to 72 Gy divided into 1.8 Gy daily. After sample preparation, intraradicular dentin slices of each root third were evaluated by Raman spectroscopy, energy dispersive spectroscopy and Knoop microhardness test. Data were analyzed by Two-way ANOVA and Tukey's test (α = 0.05). RESULTS: In Raman spectroscopy, carbonate and amide III showed a significant difference for irradiation and third (carbonate p = 0.021 and p < 0.001; amide III p < 0.001 and p = 0.001, respectively). For amide I, there was a significant difference for third (p < 0.001). For carbonate/mineral ratio, there was a significant difference for irradiation (p = 0.0016) and third (p < 0.001), with the irradiated middle third showing the lowest values. For amide I/amide III ratio, there was a significant difference for irradiation (p = 0.005) in the cervical third. In energy dispersive spectroscopy, carbon (p = 0.004; p = 0.020), phosphorus (p < 0.001; p = 0.009) and calcium (p = 0.008; p = 0.007) showed differences for irradiation and third, with the irradiated groups presenting lower values in cervical and middle thirds. For calcium/phosphorus ratio, there was a significant difference for irradiation (p < 0.001) in cervical and middle thirds. Regarding microhardness, there was a significant difference for irradiation (p < 0.001), with all irradiated groups showing lower microhardness values. CONCLUSIONS: The radiotherapy altered the chemical and mechanical properties of intraradicular dentin, mainly in the cervical and middle root thirds.

Biomechanical behavior of three maxillary expanders in cleft lip and palate: a finite element study

Abstract: This study evaluated the stress distribution in the dentoalveolar and palatal bone structures during maxillary expansion in a 17-year-old male patient with bilateral cleft lip and palate (BCLP) using expanders with dental (HYRAX) and skeletal anchorage (MARPE). For the generation of the specific finite element models, cone-beam computed tomography was used, and the DICOM files were exported to Mimics 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: conventional four-banded hyrax screw (9 mm); B) MARPE-DS: 3 miniscrews (1.8 mm diameter - 5.4 mm length) and four-banded dental anchorage; and C) MARPE-NoDS: 3 miniscrews without dental anchorage. Maxillary expansion was simulated by activating the expanders transversely 1 mm on the "X" axis. HYRAX resulted in higher levels of deformation predominantly in the dentoalveolar region. MARPE-DS showed stress in the dentoalveolar region and mainly in the center of the palatal region, at approximately 4,000 με. MARPE-NoDS exhibited evident stress only in the palatal region. High stress levels in the root anchoring teeth were observed for HYRAX and MARPE-DS. In contrast, MARPE-NoDS cause stress on the tooth structure. The stress distribution from the expanders used in the BLCP showed asymmetric expansive behavior. During the initial activation phase of expansion, the HYRAX and MARPE-DS models produced similarly high strain at the dentoalveolar structures and upper posterior teeth displacement. The MARPE-NoDS model showed restricted strain on the palate.

Survival of severely compromised endodontically treated teeth restored with or without a fiber glass post.

OBJECTIVE: The use of a fiber glass post (FGP) type and choice of FGP diameter to restore endodontically treated incisors without ferrule is controversial. This study evaluated survival rate and failure mode of severely compromised central incisors without ferrule rehabilitated using resin-based composite (RBC) with or without FGP with different diameters. METHODOLOGY: A total of 60 decoronated bovine incisors without a ferrule were endodontically treated and prepared for 1.4, 1.6, and 1.8 mm diameter FGPs (Whitepost System DC 0.5, Fit 0.4, and DCE 0.5; FGM). Half of the teeth received FGPs cemented using dual-cure resin cement (Allcem Core; FGM), the other half were filled using only bulk-fill RBC (OPUS Bulk Fill; FGM). The crowns were directly restored with RBC. The roots were embedded in polystyrene resin and the periodontal ligament was simulated with polyether impression material. Fatigue testing was conducted under 5 Hz cyclic loading at 30 degrees to the incisal edge, beginning at 50 N (5,000 cycles) as a warmup. After, the load was increased 100 N every 15,000 cycles until fracture occurred. All specimens were subjected to transillumination, micro-CT analysis, and digital radiography before and after fatigue testing. Fracture mode was classified according to severity and repair potential. Data were analyzed with Kaplan-Meier survival test and post hoc log-rank test (α=0.05) for pairwise comparisons. RESULTS: Using FGP significantly increased the number of cycles to failure, irrespective of FGP diameters (p=0.001). The FGP diameters had no statistically significant effect on cycles to failure or failure mode. CONCLUSION: Using FGP without ferrule improved survival rate of structurally severely compromised central incisors compared with rehabilitation without FGP. The diameter of the FGPs had no effect on the survival rate and failure mode.

Effect of thickness and shade of CAD/CAM composite on the light transmission from different light-curing units.

The thickness and shade of a restoration will affect the transmission of light from the light-curing unit (LCU). This study determined the power (mW), spectral radiant power (mW/nm), and beam profile of different LCUs through various thicknesses and shades of a CAD-CAM resin composite (BRAVA Block, FGM). Five thicknesses: 0.5; 0.75; 1.0; 1.5, and 2.0 mm, in three shades: Bleach; A2 and A3.5 of a CAD-CAM resin (n = 5). Two single-peak LCUs: EL, Elipar DeepCure-S (3M Oral Care); and OP, Optilight Max (Gnatus), and one multiple-peak LCU: VL, VALO Grand (Ultradent), were used. The LCUs were positioned touching the surface of the BRAVA Block. The power and emission spectrum were measured using a fiberoptic spectrometer attached to an integrating sphere, and the beam profiles using a laser beam profiler. The effect of the material thickness on the light attenuation coefficients was determined. VL and EL delivered more homogeneous beam profiles than OP. The type of the BRAVA Block had a significant effect on the transmitted power, and wavelengths of transmitted light (p < 0.001). There was an exponential reduction in the power and emission spectrum as the thickness of the BRAVA Block increased (p < 0.001). The light transmission through the A2 shade was least affected by the thickness (p < 0.001). The attenuation coefficient was higher for the violet light and higher for A3.5 than the A2 or Bleach shades. No violet light from the VL could be detected at the bottom of 2.0 mm of the BRAVA Block.

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.

Leveraging School Health Programs in Africa: Integrated Screening for Rheumatic Heart Disease and Dental Caries.

Background: Rheumatic heart disease (RHD) and dental caries (DC) disproportionately affect children and young adults in sub-Saharan countries, with major impact on schoolchildren's health and education. DC in children with RHD constitutes an important risk for fatal complications. Our study aimed at assessing the feasibility of simultaneous RHD and DC screening in school environment. Methods: March 20-24, 2022, we performed an observational descriptive study of schoolchildren in a public school in Maputo City, Mozambique. RHD screening involved two stages: first, a physical examination (including cardiac auscultation and direct observation of the oral cavity), and second, an abbreviated echocardiography performed by a cardiologist. Rapid testing for group A Streptococcus (GAS) was done to every eighth child in the classroom and for those with signs suggesting recent infection, in accordance with the study protocol developed for screening. A multidisciplinary team collected the data. Data were analyzed using descriptive statistics. Findings: A total of 954 students (median age 9; range 6-15) were screened. One hundred and twenty-five participants were eligible for a rapid antigen test, of which 6 (4.8%) tested positive. On clinical evaluation 52 children (5.3%) presented a heart murmur. Echocardiography on 362 children showed borderline RHD in 35 children and definite RHD in 2 (0.6%); 1 child had a ventricular septal defect. Dental cavities were present in 444 (48.4%), despite 904 out of 917 students reporting brushing of their teeth once to three times daily (98.6%). Conclusion: School-based integrated oral and cardiovascular screenings and use of rapid tests for GAS carriage provide crucial information to create customized preventive strategies for rheumatic fever (RF) and RHD in low- and middle-income countries (LMICs), in addition to detecting children at very high risk of bacterial endocarditis. The sustainability of such interventions and acceptability by health providers needs to be assessed.

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.

Physical and mechanical properties of four 3D-printed resins at two different thick layers: An in vitro comparative study.

OBJECTIVES: This in vitro comparative study aimed to evaluate the physical and mechanical properties of four 3D-printed resins with two different thickness layers. METHODS: Four printed resins (VarseoSmile Crown Plus, VSC; NexDent C&B MFH, MFH; Nanolab 3D, NNL; and Resilab 3D Temp, RSL) were printed with 50 µm and 100 µm layer thickness, resulting in 80 bars measuring 25 × 2×2 mm. The specimens underwent a Raman spectroscopy for degree of conversion, confocal laser scanning microscopy for surface roughness (Sa), three-point bending test for flexural strength and elastic modulus, and a Vickers hardness test (VHN). Data was tested for normality using the Shapiro-Wilk, two-way ANOVA, and Tukey test (α = 0.05) for statistical analysis. RESULTS: The layer thickness affected all performed tests, but the elastic modulus (p < 0.001). Specimens with 100 µm showed, in general, worse results outcomes than those with 50 µm (p < 0.001). However, within the limitations of this comparative in vitro study, it could be concluded that the tested resins and layer thicknesses directly influenced physical and mechanical properties. SIGNIFICANCE: The physical and mechanical properties of three-dimensional printed restorations can be affected by the layer thickness, which can interfere with the choice of the 3D printing resin for a desired clinical outcome.

Effects of different calcium-silicate based materials on fracture resistance of immature permanent teeth with replacement root resorption and osteoclastogenesis.

Objectives: This study evaluated the effects of Biodentine (BD), Bio-C Repair (BCR), and mineral trioxide aggregate (MTA) plug on the fracture resistance of simulated immature teeth with replacement root resorption (RRR) and in vitro-induced osteoclastogenesis. Materials and Methods: Sixty bovine incisors simulating immature teeth and RRR were divided into 5 groups: BD and BCR groups, with samples completely filled with the respective materials; MTA group, which utilized a 3-mm apical MTA plug; RRR group, which received no root canal filling; and normal periodontal ligament (PL) group, which had no RRR and no root canal filling. All the teeth underwent cycling loading, and compression strength testing was performed using a universal testing machine. RAW 264.7 macrophages were treated with 1:16 extracts of BD, BCR, and MTA containing receptor activator of nuclear factor-kappa B ligand (RANKL) for 5 days. RANKL-induced osteoclast differentiation was assessed by staining with tartrate-resistant acid phosphatase. The fracture load and osteoclast number were analyzed using 1-way ANOVA and Tukey's test (α = 0.05). Results: No significant difference in fracture resistance was observed among the groups (p > 0.05). All materials similarly inhibited osteoclastogenesis (p > 0.05), except for BCR, which led to a lower percentage of osteoclasts than did MTA (p < 0.0001). Conclusions: The treatment options for non-vital immature teeth with RRR did not strengthen the teeth and promoted a similar resistance to fractures in all cases. BD, MTA, and BCR showed inhibitory effects on osteoclast differentiation, with BCR yielding improved results compared to the other materials.

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.

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.

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.

Effect of pre-heating methods and devices on the mechanical properties, post-gel shrinkage, and shrinkage stress of bulk-fill materials.

This study evaluated the effect of using two different pre-heating methods on the three resin-based composite (RBCs). Three paste viscosity bulk-fill RBCs (VisCalor Bulk [VC]; VOCO; x-tra fil Caps [XF], VOCO; Filtek One Bulk Fill [FO], 3 M) were pre-heated using either a VisCalor Dispenser (VOCO) to 65 °C, or the Caps Warmer (VOCO) to 37 °C, 54 °C, or 68 °C. The temperature inside the capsules and cavity was monitored before and after insertion into the matrix. Within 30 s of inserting the RBC, they were light-activated using a VALO (Ultradent) curing light for 20 s. The post-gel shrinkage (Shr - %), Flexural Strength (FS - MPa), Elastic Modulus (E - MPa), degree of conversion (DC - %), Knoop Hardness (KH - N/mm2), diametral tensile strength (DTS - MPa), and compressive strength (CS - MPa) of the RBCs were measured (10 specimens per group). The shrinkage stress was calculated using three-dimensional finite element analysis. Data were analyzed using one-way, two-way ANOVA and Tukey's test (α = 0.05). The temperature fell rapidly after the RBC was inserted into the cavity. Pre-heating the RBCs did not affect the mechanical properties. FO had the lowest E, DC, and KH values, VC had intermediate values, and XF achieved the highest values. The DTS and CS values were not affected by the various pre-heating methods, the temperature, or RBC. Pre-heating methods at 37 °C produced higher shrinkage for all RBCs. VC pre-heated to 65 °C produced the lowest stress when measured at 10 min after light activation.

Effect of thickness and shade of CAD/CAM composite on the light transmission from different light-curing units

Abstract The thickness and shade of a restoration will affect the transmission of light from the light-curing unit (LCU). This study determined the power (mW), spectral radiant power (mW/nm), and beam profile of different LCUs through various thicknesses and shades of a CAD-CAM resin composite (BRAVA Block, FGM). Five thicknesses: 0.5; 0.75; 1.0; 1.5, and 2.0 mm, in three shades: Bleach; A2 and A3.5 of a CAD-CAM resin (n = 5). Two single-peak LCUs: EL, Elipar DeepCure-S (3M Oral Care); and OP, Optilight Max (Gnatus), and one multiple-peak LCU: VL, VALO Grand (Ultradent), were used. The LCUs were positioned touching the surface of the BRAVA Block. The power and emission spectrum were measured using a fiberoptic spectrometer attached to an integrating sphere, and the beam profiles using a laser beam profiler. The effect of the material thickness on the light attenuation coefficients was determined. VL and EL delivered more homogeneous beam profiles than OP. The type of the BRAVA Block had a significant effect on the transmitted power, and wavelengths of transmitted light (p < 0.001). There was an exponential reduction in the power and emission spectrum as the thickness of the BRAVA Block increased (p < 0.001). The light transmission through the A2 shade was least affected by the thickness (p < 0.001). The attenuation coefficient was higher for the violet light and higher for A3.5 than the A2 or Bleach shades. No violet light from the VL could be detected at the bottom of 2.0 mm of the BRAVA Block.