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.

Selective carious tissue removal and glass ionomer liner reduction of pulp stress in bulk fill resin composite restorations.

To evaluate the effect of selective or nonselective carious tissue removal and the use of a resin-modified glass ionomer (RMGIC) liner under bulk fill resin composite restoration on the stress at the pulp chamber, the elastic moduli of hard, firm, soft and intact dentin were calculated using nanoindentation. Post-gel shrinkage of the bulk fill resin composite and RMGIC were determined using the strain-gauge method. Six finite element models were created by using digital radiography with the combination of two study factors: a) carious tissue removal: selective removal or nonselective removal of carious tissue, and b) use of RMGIC liner: with or without 1.0 mm of RMGIC liner. The modified von Mises stresses (mvm) (MPa) were extracted on the nodes of the internal wall of the pulp ceiling chamber at 100 N occlusal loading. Data were analyzed descriptively and recorded quantitively. Both study factors influenced the stress distribution. The mvm stress during the restorative procedure was higher for nonselective carious tissue removal without RMGIC (25.9 MPa) and lower for selective carious tissue removal associated with RMGIC (13.5 MPa). The dentin elastic modulus increased from soft carious (3.6 ± 0.3 MPa) to firm carious (5.2 ± 1.0 MPa) to hard carious (10.9 ± 1.2 MPa) to intact dentin (22.7 ± 3.0 MPa). Molars with carious lesions showed high mvm stress at the pulp ceiling (89.6 MPa) and at fragilized coronal structure remaining. Selective carious tissue removal followed by restoration using a Vitrebond liner and Tetric N-Ceram Bulk fill reduced the stress at the pulp chamber ceiling.

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.

Selective carious tissue removal and glass ionomer liner reduction of pulp stress in bulk fill resin composite restorations

Abstract: To evaluate the effect of selective or nonselective carious tissue removal and the use of a resin-modified glass ionomer (RMGIC) liner under bulk fill resin composite restoration on the stress at the pulp chamber, the elastic moduli of hard, firm, soft and intact dentin were calculated using nanoindentation. Post-gel shrinkage of the bulk fill resin composite and RMGIC were determined using the strain-gauge method. Six finite element models were created by using digital radiography with the combination of two study factors: a) carious tissue removal: selective removal or nonselective removal of carious tissue, and b) use of RMGIC liner: with or without 1.0 mm of RMGIC liner. The modified von Mises stresses (mvm) (MPa) were extracted on the nodes of the internal wall of the pulp ceiling chamber at 100 N occlusal loading. Data were analyzed descriptively and recorded quantitively. Both study factors influenced the stress distribution. The mvm stress during the restorative procedure was higher for nonselective carious tissue removal without RMGIC (25.9 MPa) and lower for selective carious tissue removal associated with RMGIC (13.5 MPa). The dentin elastic modulus increased from soft carious (3.6 ± 0.3 MPa) to firm carious (5.2 ± 1.0 MPa) to hard carious (10.9 ± 1.2 MPa) to intact dentin (22.7 ± 3.0 MPa). Molars with carious lesions showed high mvm stress at the pulp ceiling (89.6 MPa) and at fragilized coronal structure remaining. Selective carious tissue removal followed by restoration using a Vitrebond liner and Tetric N-Ceram Bulk fill reduced the stress at the pulp chamber ceiling.

Effect of exposure time and moving the curing light on the degree of conversion and Knoop microhardness of light-cured resin cements.

OBJECTIVE: To evaluate the effect of exposure time and moving the light-curing unit (LCU) on the degree of conversion (DC) and Knoop microhardness (KH) of two resin cements that were light-cured through ceramic. METHODS: Two resin cements: AllCem Veneer APS (FGM) and Variolink Esthetic LC (Ivoclar Vivadent) were placed into a 0.3 mm thick matrix in 6 locations representing the canine to canine. The resins were covered with 0.5 mm thick lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent). A motorized device moved the LCUs over the ceramic when the LCU was on. Two single-peak LCUs: Elipar DeepCure-L (3M Oral Care) and Emitter C (Schuster), and one multi-peak: Bluephase G2 (Ivoclar Vivadent) were used with 3 different exposure protocols: a localized exposure centered over each tooth for 10 or 40 s; moving the tip across the 6 teeth for a total exposure time of 10 or 40 s; and moving the tip across the 6 teeth resins for a total exposure time of 60 or 240 s. After 24 h, the DC and KH were measured on the top surfaces and the data was analyzed using three-way ANOVA and Tukey's tests (α = 0.05). RESULTS: Interposition of 0.5 mm of ceramic reduced the irradiance received by the resin by approximately 50%. The 40 s localized exposure over each tooth always produced significantly higher DC and KH values. Moving the LCUs with a total exposure time of 10 s resulted in the lowest DC and KH. There was no beneficial effect on the DC or KH when the multi-peak (violet-blue) LCU (Elipar DeepCure-L or Bluephase G2), but the lower light output from a small tip LCU reduced the DC and KH values (Emitter C). SIGNIFICANCE: Moving the LCUs when photo-curing light-cured resin cements is not recommended. This study showed that a single-peak LCU could activate a resin cement that uses Ivocerin™ as well as the multi-peak LCU.

Irradiance and Radiant Exposures Delivered by LED Light-Curing Units Used by a Left and Right-Handed Operator.

The combination of the restoration location, the hand preference of the operator using the light-curing unit (LCU), and the design of the LCU all can have an impact on the amount of the light delivered to the restoration. To evaluate the effect of left-handed or right-handed users, the position of the operator (dentist or assistant), and the LCU design on the irradiance, radiant exposure and emission spectrum delivered to the same posterior tooth. Two light emitting diode (LED) LCUs were tested: an angulated monowave LCU Radii-Cal (SDI, Victoria, Australia) and a straight aligned multi-peak LCU Valo Cordless (Ultradent, South Jordan, UT, USA). The irradiance values (mW/cm2), radiant exposure (J/cm2) and emission spectrum were measured using a sensor in maxillary left second molar tooth. The irradiance and radiant exposure were analyzed using three-way ANOVA followed by Tukey test (a=0.05). The emission spectra (nm) were analyzed descriptively. The interaction between LCU design, operator position, and hand preference significantly influenced the irradiance and radiant exposure (P<0.001). In all cases, Valo delivered significantly higher irradiance than Radii-Cal. The handedness and the operator position affected the irradiance and radiant exposure delivered from Valo. Operator position and access affect the irradiance and radiant exposure delivered to the maxillary left second molar. The irradiance and radiant exposure can be greater when a right-hand operator is positioned on the right side of the chair and a left-hand operator is positioned on the left side of the chair. This may result in better resin composite polymerization.

Irradiance and radiant exposures delivered by led light-curing units used by a left and right-handed operator

Abstract The combination of the restoration location, the hand preference of the operator using the light-curing unit (LCU), and the design of the LCU all can have an impact on the amount of the light delivered to the restoration. To evaluate the effect of left-handed or right-handed users, the position of the operator (dentist or assistant), and the LCU design on the irradiance, radiant exposure and emission spectrum delivered to the same posterior tooth. Two light emitting diode (LED) LCUs were tested: an angulated monowave LCU Radii-Cal (SDI, Victoria, Australia) and a straight aligned multi-peak LCU Valo Cordless (Ultradent, South Jordan, UT, USA). The irradiance values (mW/cm2), radiant exposure (J/cm2) and emission spectrum were measured using a sensor in maxillary left second molar tooth. The irradiance and radiant exposure were analyzed using three-way ANOVA followed by Tukey test (a=0.05). The emission spectra (nm) were analyzed descriptively. The interaction between LCU design, operator position, and hand preference significantly influenced the irradiance and radiant exposure (P<0.001). In all cases, Valo delivered significantly higher irradiance than Radii-Cal. The handedness and the operator position affected the irradiance and radiant exposure delivered from Valo. Operator position and access affect the irradiance and radiant exposure delivered to the maxillary left second molar. The irradiance and radiant exposure can be greater when a right-hand operator is positioned on the right side of the chair and a left-hand operator is positioned on the left side of the chair. This may result in better resin composite polymerization.

Resumo A combinação da localização da restauração, a preferência de mão do operador ao utilizar aparelhos fotopolimerizadores (AFP) com luz emitida por diodo (LED) e o formato do AFP podem afetar a quantidade de luz fornecida à restauração. O objetivo foi avaliar o efeito de operadores canhotos e destros, a posição do operador (dentista ou auxiliar), e o formato do AFP na irradiância, energia radiante e espectro de luz entregue ao mesmo dente posterior. Dois AFP foram testados: um com formato angulado, onda única Radii-Cal (SDI, Victoria, Australia) e um formato reto multi-pico Valo Cordless (Ultradent, South Jordan, UT, USA). Os valores de irradiância (mW/cm²), energia radiante (J/cm²) e espectro de luz foram medidos utilizando um sensor no segundo molar superior esquerdo. A irradiância e energia radiante foram analisados utilizando ANOVA 3 fatores seguido por teste de Tukey (a=0.05). O espectro de luz (nm) foi analisado de forma descritiva. A interação entre o formato do AFP, posição do operador e preferência de mão foram significativamente influentes na irradiância e energia radiante (P<0.001). Em todos os casos, Valo teve irradiância significativamente maior que Radii-Cal. A mão dominante e a posição do operador afetaram a irradiância e energia radiante com o Valo. Posição do operador e acesso afetou a irradiância e exposição radiante entregue ao segundo molar superior esquerdo. A irradiância e exposição radiante teve melhores resultados quando AFP foi utilizado com a mão direita pelo operador posicionado na cadeira do lado direito e mão esquerda do operador posicionado do lado esquerdo da cadeira. Estes resultados podem levar a uma melhor polimerização da resina composta.

Estética do sorriso: Planejamento digital, cirurgia periodontal e procedimento restaurador / Smile's esthetics: digital smile design, periodontal surgery and restorative procedure

A busca pela estética tem acentuado a procura dos pacientes pela transformação do sorriso. Com o auxílio da fotografia e da tecnologia computacional, é possível a realização do DSD (digital smile design ­ planejamento digital do sorriso), que nos dá maior previsibilidade do tratamento. A confirmação deste planejamento digital se dá na prova do mock-up, a partir do qual o paciente tem a real sensação do seu sorriso planejado. Este artigo apresentou um caso clínico no qual se destaca a adesão do paciente ao tratamento e a realização de cirurgia periodontal para aumento de coroa clínica, seguida de restaurações diretas com resinas compostas, posterior ao enceramento diagnóstico. Com o planejamento integrando a terapia cirúrgica periodontal e o protocolo restaurador adesivo direto guiado por planejamento digital (DSD), foi possível estabelecer um excelente resultado com uma elevada satisfação do paciente.

The seek for esthetics has increased patient´s demand for the smile makeover. With the help of computational technology, it is possible to perform the DSD (digital smile design) with greater treatment predictability treatment. Confirmation of this digital planning occurs in the mock-up test, from which the patient has a physical sensation of his/her planned smile. This article presents a clinical case which highlights the patient cooperation and periodontal surgery for crown lengthening, followed by direct composite resin restorations after the diagnostic wax-up procedure. With an integrated treatment planning guided by the DSD protocol, it was possible to establish an excellent outcome with high patient satisfaction.