A digital platform to support communication and organization in the general practice: Evaluation of healthcare usage and costs using claims data of a health insurer

INTRODUCTION

The pressure on general practitioners (GPs) is rising due to the increasing demand for care and a decreasing availability of GPs. eHealth is seen as one of the solutions to enhance accessibility and reduce workload. A platform supporting the organization and communication in general practice has been developed offering services, such as econsultations. This study aims to evaluate healthcare usage and costs of patients using this platform by comparing these outcomes (1) before and after implementation and (2) an intervention with a matched control group.

MATERIAL AND METHODS

This study is a retrospective observational cohort study. To evaluate the longitudinal impact of the implementation on healthcare usage, mixed model Poisson analyses were used with time as a factor term for the within-subject analysis and exposure to the platform as a factor term and an interaction term (i.e., exposure X 6-months) in the between-subject analysis. Cost analyses were done with mixed model analyses of variance over time.

RESULTS

The total number of GP consultations significantly increased after compared to before implementation (i.e., Rate = 1.52; p < 0.001). The number of GP consultations was higher in the intervention compared to the control group (respectively, Rate = 1.23; p = 0.035). Healthcare costs increased for GP consultations after compared to before implementation (€13,57; p < 0.001). The costs for GP consults were significantly higher in the intervention compared to the control group (€7,06; p 0.018).

CONCLUSION

This study showed a rise in GP consultations and costs when implementing a digital platform. This increase was presumably and partly caused by circumstances in one of the two included practices. Moreover, creating new options for contacting and communicating with the GP can enhance care accessibility and thereby driving an increase in consultations. This digital platform is a promising working method in general practice to facilitate patients and provide GPs with more flexibility.

Prewarming effect on adaptation, porosities, and strength of a composite resin

Warming composite resin before insertion to reduce viscosity is advocated for improving adaptation and reducing voids. This study evaluated how prewarming altered porosities, adaptation, and strength. Twenty composite restorations were placed in 2 increments in typodont teeth with a large Class II preparation. The composite was either at room temperature (control) or prewarmed to 68 °C (n = 10/group). Each increment was light-cured for 20s. After 24h, the restored teeth were sectioned and imaged under a stereomicroscope. Examiners ranked the quality of adaptation to walls and between increments, and the presence of voids on a 0-3 scale. Results were statistically analyzed using Mann-Whitney U Test. Diametral tensile strength of monolithic or incrementally-filled composite cylinders (6 mm diameter × 4 mm height; n = 10/group) made with room temperature or prewarmed composite were tested at 0.5 mm/min. Strength results were analyzed using ANOVA statistics followed by pairwise comparisons. Restorations made with prewarmed composite had significantly fewer large voids and better adaptation to cavity walls and between layers (P < 0.05). Strength of prewarmed composite was higher than room temperature composite, and was significantly higher in monolithic specimens (P < 0.05). It was concluded that prewarming conventional composite can improve its handling, making it handle more like a flowable composite without jeopardizing physical properties. The prewarmed composite was found to have better adaptation and fewer voids, and attained higher strength than composite that was not prewarmed.

Fast Curing with High-power Curing Lights Affects Depth of Cure and Post-gel Shrinkage and Increases Temperature in Bulk-fill Composites

OBJECTIVES

High-power LED curing lights and bulk-fill resin composites are intended to reduce chair time. This study investigated depth of cure, post-gel shrinkage (responsible for shrinkage stress), and heat generation in bulk-fill composites when cured according to minimum curing times recommended by manufacturers of curing lights and composites.

METHODS

A regular LED curing light (Demi Ultra, 1350 mW/cm2, Kerr Dental) and two LED curing lights with high-power modes (VALO Grand, 3117 mW/cm2 Xtra Power, Ultradent; and Bluephase PowerCure, 2435 mW/cm2 Turbo and 3344 mW/cm2 3sCure, Ivoclar Vivadent) were tested on three bulk-fill composites (Filtek One Bulk Fill, 3M Oral Care Solutions; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; Tetric Powerfill, Ivoclar Vivadent). Using minimum times recommended by manufacturers (3, 5, 6, 10, or 20 seconds), depth of cure was determined by Vickers hardness of specimens cured in a slot (n=10). Post-gel polymerization shrinkage was measured using a strain gauge (n=10) and temperature with a thermocouple (n=5). Results were analyzed using two- and one-way analysis of variance (ANOVA) followed by pairwise comparisons or Student-Newman-Keuls post hoc tests (α=0.05).

RESULTS

Curing lights and curing protocols significantly affected depth of cure, post-gel shrinkage, and temperature rise (p<0.001). Cure decreased with depth whereby best overall curing performance was achieved by the 20 second exposure at lowest irradiance (Demi Ultra). Fast curing (3-5 seconds) at high irradiance resulted in lesser depth-of-cure performance, except for the BluePhase-Tetric PowerFill combination. Post-gel shrinkage was higher in all composites when cured at high irradiance (p<0.001), while heat generated also tended to be higher.

CONCLUSIONS

Although the high-power LED curing lights advertise time savings, not all manufacturer recommended minimum curing times cured bulk-fill materials to the same extent. Moreover, these time savings came at a cost of higher post-gel shrinkage and generated more heat in the bulk-fill composites than the lower irradiance curing protocol.

The effect of filling technique on the cuspal strain, polymerization shrinkage stress, enamel crack formation and depth of cure of restored molars

OBJECTIVE

Evaluate the effect of different restorative filling techniques on the residual shrinkage stress (ShrS), cuspal strain (CS), depth of cure (DC), and enamel crack formation (Ec) in molars with MOD restorations.

METHODS

Post-gel shrinkage, elastic modulus, compressive and diametral tensile strength of the Filtek One Bulk Fill composite were calculated. Sixty molars with MOD preparations were restored using four filling techniques: Bulk; Horizontal; Oblique; Natural enamel and dentin substitution (NEDS) technique. CS was measured using a strain gauge (n = 10). The DC (n = 5) was measured using Knoop hardness. Shrinkage stress/strain was analyzed using 3D finite element analysis. The Ec analysis was carried out by transillumination. Two-way ANOVA with repeated measures and Tukey's HSD test (α = 0.05) was performed for the CS data. Two-Way ANOVA and Tukey's HSD test was performed for the DC data (α = 0.05).

RESULTS

CS was higher at the lingual cusp for the horizontal and NEDS technique. No statistical difference was found between the buccal and lingual CS values for the Bulk (p = 0.367) or Oblique techniques (p = 0.192). CS values were lower for the Bulk. More enamel cracks were found for the Bulk. DC was lower at 4 mm regardless the filling technique. The Horizontal showed the highest ShrS values. The Bulk generated the lower ShrS values.

SIGNIFICANCE

A Bulk technique caused the lowest shrinkage stress/strain. An Oblique technique yielded the best balance between stress, strain and crack formation. NEDS technique is a good alternative to decrease the number of increments while maintaining the stress levels nearby the Oblique technique.

Looking bad: Female patients drawing their representation of chemotherapy-induced alopecia

This study explored the experienced impact of alopecia using patient's drawings. Forty patients made drawings of their feelings about appearance of their head and hair before and during chemotherapy. Patients also reported illness perceptions (B-IPQ). Twenty-four patients (60%) reported ⩾50% alopecia at enrollment. Most patients (70%) drew a negative change of feelings over time and physical changes. Many experiences related to alopecia emerged from the written texts underneath the drawings and the B-IPQ. Drawings depicted deteriorated feelings of appearance, affecting many activities throughout the day. Healthcare providers are advised to use patient-tailored questioning about alopecia.

"Dear hair loss"-illness perceptions of female patients with chemotherapy-induced alopecia

OBJECTIVE

Chemotherapy-induced alopecia (CIA) is one of the most common and distressing side effects of chemotherapy treatment. This study aims to assess the illness perceptions of female patients dealing with CIA, and their associations with demographic and clinical characteristics, coping strategies, and quality of life. The secondary aim was to compare the illness perceptions of patients with CIA with other samples, to help elucidate the specific perceptions of patients with CIA.

METHOD

Forty female patients at risk of severe hair loss due to chemotherapy treatment were included at the oncological daycare unit of a teaching hospital in the Netherlands. Patients were asked to complete the Brief-Illness Perception Questionnaire (B-IPQ) and the Hair Quality of Life (Hair-QoL) questionnaire.

RESULTS

Illness perceptions indicated that although patients understood their hair loss, they lacked being able to make sense of managing it, negatively impacting patients' lives. Psychological quality of life was significantly correlated with the B-IPQ domains: consequences, degree of concern, and emotional response. Social quality of life was significantly correlated with psychological quality of life. Patients with CIA felt significantly less able to manage their hair loss, compared to patients with breast cancer and psoriatic arthritis.

CONCLUSION

As patients' beliefs of being able to manage their hair loss are important for adopting and maintaining adequate coping behaviors, additional effort of health care providers in fostering patients' sense of control is indicated, focusing on patients' strengths during and after chemotherapy treatment. In the context of developing interventions for patients with CIA, consequences, concern, and emotional response are the major dimensions that should be taken in account to help patients deal with hair loss.

Giving A Face to Chemotherapy-Induced Alopecia: A Feasibility Study on Drawings by Patients

Objective:

Individuals with cancer experience the impact of chemotherapy on hair loss in different ways. The aim of this pilot study was to explore patients' experiences of alopecia through patients' drawings.

Methods:

Fifteen female patients diagnosed with cancer and treated with chemotherapy were recruited at the oncological day-care unit of a teaching hospital in the Netherlands. Participants completed a semi-structured interview about alopecia. They drew their head and hair before and during chemotherapy and completed the Brief Illness Perception Questionnaire (B-IPQ).

Results:

The drawings revealed predominantly physical effects, rather than emotions. Emotions were evident in the text that patients wrote under the drawings and in the B-IPQ open question about the perceived consequences of alopecia. The overall impact of alopecia that emerged from the drawings and the B-IPQ corresponded to the information retrieved from the interviews, namely disappointment, insecurity, sadness, and confrontation.

Conclusions:

Drawings expose cognitive and emotional responses to alopecia that may be relatively unexplored when using traditional assessment methods such as questionnaires or interviews. In future research, the drawing instructions need to be more specifically focused on feelings in order to better capture emotional reactions to hair loss.

The effect of occlusal loading on cervical gap deformation: A 3D finite element analysis

OBJECTIVES

Secondary caries can be accelerated by hydrodynamic flow in a gap between the tooth and restorative material. This study investigated whether occlusal loading can lead to increased hydrodynamic flow by deforming a gap between tooth and restorative material.

METHODS

3D finite element analysis was employed to model a molar containing a restoration with an interfacial gap. The model was loaded using direct cusp-to-restoration contact and using a rubber tube model simulating a food bolus. The object exerting pressure was moved across the molar from buccal to lingual side. The applied forces were 50, 100, 200 and 400N. The elastic modulus of the restoration material was varied between 5, 10, 15.9 and 25GPa to resemble different kinds of composite. The primary outcome parameter was the volume of the gap under occlusal pressure.

RESULTS

Occlusal loading resulted in deformation of the gap area. Maximum deformation was seen when loading was applied in the middle of the restoration. Higher forces and lower restoration stiffness led to more deformation of the gap. Maximum deformation with a force of 100N and composite modulus of 15.9GPa was -0.0083mm³ (1.12%).

SIGNIFICANCE

Deformation of the gap between tooth and restorative material could lead to increased hydrodynamic flow and faster secondary caries lesion formation. The measured deformation is small. Further research needs to show whether gap compression through occlusal loading affects secondary caries formation to a clinically relevant degree.

Delayed Photoactivation of Dual-cure Composites: Effect on Cuspal Flexure, Depth-of-cure, and Mechanical Properties

Objectives:

This study tested whether delayed photoactivation could reduce shrinkage stresses in dual-cure composites and how it affected the depth-of-cure and mechanical properties.

Methods and Materials:

Two dual-cure composites (ACTIVA and Bulk EZ) were subjected to two polymerization protocols: photoactivation at 45 seconds (immediate) or 165 seconds (2 minutes delayed) after extrusion. Typodont premolars with standardized preparations were restored with the composites, and cuspal flexure caused by polymerization shrinkage was determined with three-dimensional scanning of the external tooth surfaces before restoration (baseline) and at 10 minutes and one hour after photoactivation. Bond integrity (intact interface) was verified with dye penetration. Depth-of-cure was determined by measuring Vickers hardness through the depth at 1-mm increments. Elastic modulus and maximum stress were determined by four-point bending tests (n=10). Results were analyzed with two- or three-way analysis of variance and pairwise comparisons (Bonferroni; α=0.05).

Results:

Delayed photoactivation significantly reduced cuspal flexure for both composites at 10 minutes and one hour (p≤0.003). Interface was &gt;99% intact in every group. Depth-of-cure, elastic modulus, and flexural strength were not significantly different between the immediate and delayed photoactivation (p&gt;0.05). The hardness of ACTIVA reduced significantly with depth (p&lt;0.001), whereas the hardness of Bulk EZ was constant throughout the depth (p=0.942).

Conclusions:

Delayed photoactivation of dual-cure restorative composites can reduce shrinkage stresses without negatively affecting the degree-of-cure or mechanical properties (elastic modulus and flexural strength).

Cuspal Flexure and Stress in Restored Teeth Caused by Amalgam Expansion

Objective:

Cracks in amalgam-filled teeth may be related to amalgam expansion. This study measured cuspal flexure and used finite element analysis to assess associated stress levels in amalgam-filled teeth.

Methods and Materials:

External surfaces of 18 extracted molars were scanned in three dimensions. Nine molars were restored with mesio-occluso-distal amalgam fillings; the other teeth were left intact as controls. All teeth were stored in saline and scanned after two, four, and eight weeks. Cuspal flexure and restoration expansion were determined by calculating the difference between scanned surfaces. Stresses in a flexed tooth were calculated using finite element analysis.

Results:

Cusps of amalgam-filled teeth flexed outward approximately 3 μm, and restoration surfaces expanded 4 to 8 μm during storage. Cuspal flexure was significantly higher in the amalgam group (multivariate tests, p&lt;0.05), but storage time had no significant effect (repeated measures, p&gt;0.05). Expansion caused stress concentrations at the cavity line angles. These stress concentrations increased stresses due to mastication 44% to 178%.

Conclusions:

Amalgam expansion pushed cavity walls outward, which created stress concentrations at the cavity line angles. Expansion stresses can raise stresses in amalgam-filled teeth and contribute to incidentally observed cracks.

Safe pseudoelastic limit range under torsional loading with Reciproc Blue

AIM

To determine the distortional angle and torsional load at the pseudoelastic limit of Reciproc Blue instruments and to verify the safety of using pre-set dedicated motors designed for use with the original Reciproc instruments.

METHODOLOGY

Two torsional conditions of Reciproc R25 and Reciproc Blue R25 were tested using a custom device. The first condition fixed the file tips at 3 mm and repetitively rotated them, with gradually increasing angles, from 10° to 270°, and the resulting torque was recorded (n = 15). The second test involved a single continuous rotation until fracture (n = 15). The pseudoelastic limits of the instruments were determined from their torque-rotation curves. For statistical analysis, two-way analysis of variance and t-tests were used, at a 95% significance level. Tested specimens were examined using field-emission scanning electron microscopy (FE-SEM).

RESULTS

The angle at the pseudoelastic limit was significantly greater for Reciproc Blue than Reciproc, regardless of test mode (P < 0.05). When torsional loading was repeated, using gradually increasing rotational angles, the torsional resistance was significantly lower than for a single rotation (P < 0.05). However, under all test conditions, the pseudoelastic limit was below the pre-set 170° of the dedicated reciprocating motor. FE-SEM evaluation of the lateral aspects of the instruments revealed numerous longitudinal microcracks running along their long axis. For Reciproc Blue groups, the file shaft machining grooves were distorted after repetitive and continuous torsional tests.

CONCLUSIONS

The 170° pre-set angle of the dedicated endodontic motors for the Reciproc system was safe for Reciproc Blue in single or time-restricted use.

Efeito da Fotoativação de Materiais de Proteção Pulpar e Resina Composta na Deformação Dentinária e Mudanças de Temperatura na Câmara Pulpar

Analisar o efeito da fotoativação de materiais de proteção pulpar e da resina composta na deformação, temperatura pulpar e na integridade da interface de teto da câmara pulpar/materiais de proteção em molares com cavidades MOD com 1,0mm dentina   na parede pulpar. Quatro materiais de proteção: adesivo auto-condicionante CLE, Clearfil SE Bond (Kuraray) 2 hidróxidos de cálcio fotoativados: BIO, Biocal (Biodinâmica); ULT, Ultrablend plus (Ultradent) e cimento de ionômero de vidro modificado por resina composta VIT, Vitrebond (3M-ESPE). As cavidades foram restauradas com resina composta (Filtek Z350 XT, 3M-Espe) (n10). Termopares e extensômetros foram utilizados para detectar mudanças de temperatura, deformação durante a fotoativação.  A deformação dentinária (µS) durante a fotoativação de CLE foi maior que os outros materiais de proteção pulpar (P <0.001).     Na fotoativação da resina, a deformação aumentou para ULT, VIT e CLE e diminuiu significativamente para BIO. A temperatura na câmara pulpar aumentou cerca de 3,5ºC após a fotoativação dos materiais protetores e 2,1ºC na resina composta. O micro-CT mostrou perfeita integridade da interface após a restauração para CLE, VIT e ULT, no entanto, foram encontrados gaps entre BIO e o teto da câmara pulpar em todas as amostras. A fotoativação dos materiais protetores resultou em deformação da dentina pulpar e aumento da temperatura. A contração da restauração em resina causou descolamento do Biocal.Palavras-chave: Fotoativação. Temperatura Pulpar. Deformação Dentinária.

Simulação de Fadiga Térmica em Elementos Finitos: Análise em Laminados Oclusais Finos em Cerâmica e Resina Nanocerâmica

O objetivo deste trabalho foi avaliar pelo método de elementos finitos a distribuição de temperatura, tensões térmicas em laminados oclusais finos confeccionados em cerâmica (IPS e.max CAD) e resina nanocerâmica (Lava Ultimate) na espessura de 0.3 e 0.6 mm. A contração pós-gel do cimento (RelyX Ultimate) foi obrida com extensometria bidirecional. Modelos de elementos finitos 2D foram construídos no software MENTAT baseados em microtomografia de primeiro molar inferior humano por importação de pontos gerados no ImageJ. A simulação da contração da camada de cimento e variação da temperatura (55, 37 e 5 °C) na superfície do modelo, simulando a fadiga térmica laboratorial, foram realizadas pelo MARC. Tensões térmicas foram avaliadas pelo critério de von Mises modificado. A contração volumétrica pós-gel do cimento foi de 1,13%. A ciclagem em baixa temperatura gerou maior tensão que em alta temperatura. Laminados mais espessos acumulam maior tensão. A cerâmica propagou maior calor que a resina nanocerâmica, sendo a camada de cimento a região que com maior acúmulo de tensão. Conclui-se que a temperatura, a contração de polimerização do cimento, a espessura e material dos laminados, afetam a distribuição de tensões térmicas.Palavras-chave: Temperatura Fadiga. Análise por Elementos Finitos.

Labelling of Bleomycin with Cobalt-57, Indium-111, Technetium-99m, Mercury-197, Lead-203, and Copper-67

The radiochemical purity of the cobalt-57 complex of bleomycin could be enhanced by adjusting the pH of the final product to a value between 5 and 6. This radiopharmaceutical appeared to have better tumor visualizing properties compared to the not neutralized preparation.

The clinical use of the cobalt-57 bleomycin complex is however limited by the long physical half-life of the label, causing a risk of radioactive contamination. It appeared to be possible to label bleomycin with radioactive cations (111In3+, 99mTc4+, 197Hg2+ and 67Cu2+) having suitable gamma ray energies and short half-lifes.

These bleomycin complexes showed a high radiochemical purity judged by their behaviour on thin layer chromatography, paper chromatography, and electrophoresis, but their application as tumor visualizing radiopharmaceutical turned out to be disappointing compared with cobalt-57 bleomycin.

Effect of Light Activation of Pulp-Capping Materials and Resin Composite on Dentin Deformation and the Pulp Temperature Change

OBJECTIVES

To analyze the effect of pulp-capping materials and resin composite light activation on strain and temperature development in the pulp and on the interfacial integrity at the pulpal floor/pulp-capping materials in large molar class II cavities.

METHODS

Forty extracted molars received large mesio-occlusal-distal (MOD) cavity bur preparation with 1.0 mm of dentin remaining at the pulp floor. Four pulp-capping materials (self-etching adhesive system, Clearfil SE Bond [CLE], Kuraray), two light-curing calcium hydroxide cements (BioCal [BIO], Biodinâmica, and Ultra-Blend Plus [ULT], Ultradent), and a resin-modified glass ionomer cement- (Vitrebond [VIT], 3M ESPE) were applied on the pulpal floor. The cavities were incrementally restored with resin composite (Filtek Z350 XT, 3M ESPE). Thermocouple (n=10) and strain gauge (n=10) were placed inside the pulp chamber in contact with the top of the pulpal floor to detect temperature changes and dentin strain during light curing of the pulp-capping materials and during resin composite restoration. Exotherm was calculated by subtracting postcure from polymerization temperature (n=10). Interface integrity at the pulpal floor was investigated using micro-CT (SkyScan 1272, Bruker). The degree of cure of capping materials was calculated using the Fourier transform infrared and attenuated total reflectance cell. Data were analyzed using one-way analysis of variance followed by the Tukey test (α=0.05).

RESULTS

Pulpal dentin strains (μs) during light curing of CLE were higher than for other pulp-capping materials ( p<0.001). During resin composite light activation, the pulpal dentin strain increased for ULT, VIT, and CLE and decreased for BIO. The pulpal dentin strain was significantly higher during pulp-capping light activation. The temperature inside the pulp chamber increased approximately 3.5°C after light curing the pulp-capping materials and approximately 2.1°C after final restoration. Pulp-capping material type had no influence temperature increase. The micro-CT showed perfect interfacial integrity after restoration for CLE and ULT; however, gaps were found between BIO and pulpal floor in all specimens. BIO had a significantly lower degree of conversion than ULT, VIT, and CLE.

CONCLUSIONS

Light curing of pulp-capping materials caused deformation of pulpal dentin and increased pulpal temperature in large MOD cavities. Shrinkage of the resin composite restoration caused debonding of BIO from the pulpal floor.

Effective Expansion: Balance between Shrinkage and Hygroscopic Expansion

The purpose of this study was to investigate the relationship between hygroscopic expansion and polymerization shrinkage for compensation of polymerization shrinkage stresses in a restored tooth. One resin-modified glass-ionomer (RMGI) (Ketac Nano, 3M ESPE), 2 compomers (Dyract, Dentsply; Compoglass, Ivoclar), and a universal resin-based composite (Esthet•X HD, Dentsply) were tested. Volumetric change after polymerization ("total shrinkage") and during 4 wk of water storage at 37°C was measured using an optical method (n= 10). Post-gel shrinkage was measured during polymerization using a strain gauge method (n= 10). Extracted human molars with large mesio-occluso-distal slot preparations were restored with the tested restorative materials. Tooth surfaces at baseline (preparation), after restoration, and during 4 wk of 37°C water storage were scanned with an optical scanner to determine cuspal flexure (n= 8). Occlusal interface integrity was measured using dye penetration. Data were analyzed using analysis of variance and post hoc tests (significance level 0.05). All tested materials shrunk after polymerization. RMGI had the highest total shrinkage (4.65%) but lowest post-gel shrinkage (0.35%). Shrinkage values dropped significantly during storage in water but had not completely compensated polymerization shrinkage after 4 wk. All restored teeth initially exhibited inward (negative) cuspal flexure due to polymerization shrinkage. Cuspal flexure with the RMGI restoration was significantly less (-6.4 µm) than with the other materials (-12.1 to -14.1 µm). After 1 d, cuspal flexure reversed to +5.0 µm cuspal expansion with the RMGI and increased to +9.3 µm at 4 wk. After 4 wk, hygroscopic expansion compensated cuspal flexure in a compomer (Compoglass) and reduced flexure with Dyract and resin-based composite. Marginal integrity (93.7% intact restoration wall) was best for the Compoglass restorations and lowest (73.1%) for the RMGI restorations. Hygroscopic expansion was more effective in compensating shrinkage stress than would be assumed based on total shrinkage, because only post-gel shrinkage needed compensation. Effective expansion is therefore hygroscopic expansion minus post-gel shrinkage.

Delayed Photo-activation Effects on Mechanical Properties of Dual Cured Resin Cements and Finite Element Analysis of Shrinkage Stresses in Teeth Restored With Ceramic Inlays

OBJECTIVE

The aim of this study was to investigate the effect of delayed photo-activation on elastic modulus, Knoop hardness, and post-gel shrinkage of dual cure resin cements and how this affects residual shrinkage stresses in posterior teeth restored with ceramic inlays.

METHODS AND MATERIALS

Four self-adhesive (RelyX Unicem, 3M ESPE; GCem, GC; MonoCem, Shofu; and seT, SDI) and two conventional (RelyX ARC, 3M ESPE; and AllCem, FGM) dual cure resin cements for cementing posterior ceramic inlays were tested. Strain gauge and indentation tests were used to measure the post-gel shrinkage (Shr), elastic modulus (E), and Knoop hardness (KHN) when photo-activated immediately and 3 and 5 minutes after placement (n=10). Shr, E, and KHN results were analyzed using two-way analysis of variance followed by Tukey honestly significant difference post hoc tests (α=0.05). The experimentally determined properties were applied in a finite element analysis of a leucite ceramic inlay (Empress CAD, Ivoclar Vivadent) cemented in a premolar. Modified von Mises stresses were evaluated at the occlusal margins and cavity floor.

RESULTS

Shr, E, and KHN varied significantly among the resin cements (p<0.001). Highest overall Shr values were found for RelyX Unicem; GCem had the lowest. Increasing the photo-activation delay decreased Shr significantly. Delayed photo-activation had no effect on E (p=0.556) or KHN (p=0.927). RelyX Unicem had the highest E values; seT and MonoCem had the lowest E values. AllCem and RelyX Unicem had the highest KHN and MonoCem had the lowest KHN. Cements with high Shr and E values caused higher shrinkage stresses. Stresses decreased with delayed photo-activation for all cements.

CONCLUSIONS

KHN and E values varied among the different resin cements. Residual shrinkage stress levels decreased with increasing photo-activation delay with all resin cements.

Effect of Restorative Protocol on Cuspal Strain and Residual Stress in Endodontically Treated Molars

Objectives

To evaluate the effect of the restorative protocol on cuspal strain, fracture resistance, residual stress, and mechanical properties of restorative materials in endodontically treated molars.

Methods

Forty-five molars received mesio-occlusal-distal (MOD) Class II preparations and endodontic treatment followed by direct restorations using three restorative protocols: composite resin (CR) only (Filtek Supreme, 3M-ESPE), resin modified glass ionomer cement in combination with CR (Vitremer, 3M-ESPE in pulp chamber and Filtek Supreme in MOD cavity), conventional glass ionomer cement in combination with composite resin (CGI-CR) (Ketac Fil, 3M-ESPE in pulp chamber and Filtek Supreme in MOD cavity). Cuspal strain was measured using strain gauges, and fracture resistance was tested with an occlusal load. Elastic modulus (EM) and Vickers hardness (VH) of the restorative materials were determined at different depths using dynamic microhardness indentation. Curing shrinkage was measured using the strain gauge technique. The restorative protocols were also simulated in finite element analysis (FEA). The shrinkage strain, cuspal strain, EM, VH, and fracture resistance data were statistically analyzed using split-plot analysis of variance and Tukey test (p=0.05). Residual shrinkage stresses were expressed in modified von Mises equivalent stresses.

Results

Shrinkage strain values (in volume %) were Ketac Fil (0.08±0.01) &lt; Vitremer (0.18±0.01) &lt; Filtek Supreme (0.54±0.03). Cuspal strain was higher and fracture resistance was lower when using CR only compared with the techniques that used glass ionomer. The EM and VH of the materials in the pulp chamber were significantly lower for glass ionomer. The FEA showed that using CR only resulted in higher residual stresses in enamel and root dentin close to the pulp chamber than the combinations with glass ionomers (RMGI-CR and CGI-CR).

Conclusions

The choice of restorative protocol significantly affected the biomechanical behavior of endodontically treated molars. Using glass ionomer to fill the pulp chamber is recommended when endodontically treated molars receive direct composite restorations because it reduces cuspal strain and increases fracture resistance.

Mechanical properties, shrinkage stress, cuspal strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique

OBJECTIVES

To compare bulk-fill with incremental filling techniques for restoring large mesio-occlusal-distal (MOD) restorations.

METHODS

Seventy-five molars with MOD preparations were divided into five groups: Z350XT, incrementally filled with Filtek Z350XT and four bulk-fills-FBF/Z350XT, Filtek Bulk Fill/Filtek Z350XT; VBF/CHA, Venus Bulk Fill/Charisma Diamond; SDR/EST-X, SDR/Esthet-X HD; TEC, TetricEvoCeram Bulk Fill. Cuspal strains were measured using strain-gauges (n=10): CSt-Re, during restorative procedure; CSt-100N, during 100N occlusal loading; CSt-Fr, at fracture load. Before fracture load, teeth were load-cycled. Fracture resistance, fracture mode, and enamel cracks were recorded. The other five teeth were used for Elastic modulus (E) and Vickers hardness (VH). Post-gel shrinkage (Shr), diametral tensile strength (DTS) and compressive strength (CS) were determined (n=10). Shrinkage stresses were analyzed using finite element analysis.

RESULTS

SDR had similar CS values as TEC, lower than all other composites. CHA had similar DTS values as Z350XT, higher than all other composites. Z350XT had the highest mean Shr and SDR the lowest Shr. New enamel cracks and propagation was observed after the restoration, regardless of filling technique. Z350XT had lower fracture resistance than bulk-fill composite techniques. No significant differences in failure modes were found. E and VH were constant through the depth for all techniques. Bulk-filling techniques had lower stresses compared to Z350XT.

CONCLUSIONS

Flowable bulk-fill composites had lower mechanical properties than paste bulk-fill and conventional composites. All bulk-fill composites had lower post-gel shrinkage than conventional composite. Bulk-fill filling techniques resulted in lower cusp strain, shrinkage stress and higher fracture resistance.

CLINICAL SIGNIFICANCE

Using bulk-fill composites cause lower CSt wich indicates lower stress in restored tooth. Furthermore, bulk-fill composites have a higher fracture resistance. Therefore, clinicians may choose the bulk-fill composite to decrease undesirable effects of restoration while simplifying filling procedure.

Frequency, severity and causes of unexpected allergic reactions to food: a systematic literature review

Food allergic patients have to deal with an avoidance diet. Confusing labelling terms or precautionary labels can result in misinterpretation and risk-taking behaviour. Even those patients that strictly adhere to their diet experience (sometimes severe) unexpected allergic reactions to food. The frequency, severity and causes of such reactions are unknown. The objective of this review was to describe the frequency, severity and causes of unexpected allergic reactions to food in food allergic patients aged > 12 years, in order to develop improved strategies to deal with their allergy. A systematic review was carried out by two researchers, in six electronic databases (CINAHL, Cochrane, EMBASE, Medline, Psychinfo and Scopus). The search was performed with keywords relating to the frequency, severity and causes of unexpected allergic reactions to food. This resulted in 24 studies which met the inclusion criteria; 18 observational and six qualitative studies. This review shows that knowledge about the frequency of unexpected reactions is limited. Peanut, nuts, egg, fruit/vegetables and milk are the main causal foods. Severe reactions and even fatalities occur. Most reactions take place at home, but a significant number also take place when eating at friends' houses or in restaurants. Labelling issues, but also attitude and risky behaviour of patients can attribute to unexpected reactions. We conclude that prospective studies are needed to get more insight in the frequency, severity, quantity of unintended allergen ingested and causes of unexpected allergic reactions to food, to be able to optimize strategies to support patients in dealing with their food allergy. Although the exact frequency is not known, unexpected reactions to food occur in a significant number of patients and can be severe. For clinical practice, this means that patient education and dietary instructions are necessary.

Cuspal Flexure and Extent of Cure of a Bulk-fill Flowable Base Composite

Objectives

To investigate a bulk-fill flowable base composite (Surefil SDR Flow) in terms of cuspal flexure and cure when used in incremental or bulk techniques.

Methods

Mesio-occluso-distal cavities (4 mm deep, 4 mm wide) were prepared in 24 extracted molars. The slot-shaped cavities were etched, bonded, and restored in 1) two 2-mm increments Esthet-X HD (control), 2) two 2-mm increments Surefil SDR Flow, or 3) 4-mm bulk Surefil SDR Flow (N=8). The teeth were digitized after preparation (baseline) and restoration and were precisely aligned to calculate cuspal flexure. Restored teeth were placed in fuchsin dye for 16 hours to determine occlusal bond integrity from dye penetration. Extent of cure was assessed by hardness at 0.5-mm increments through the restoration depth. Results were analyzed with analysis of variance and Student-Newman-Keuls post hoc tests (α=0.05).

Results

Surefil SDR Flow, either incrementally or bulk filled, demonstrated significantly less cuspal flexure than Esthet-X HD. Dye penetration was less than 3% of cavity wall height and was not statistically different among groups. The hardness of Surefil SDR Flow did not change throughout the depth for both incrementally and bulk filled restorations; the hardness of Esthet-X HD was statistically significantly lower at the bottom of each increment than at the top.

Conclusions

Filling in bulk or increments made no significant difference in marginal bond quality or cuspal flexure for the bulk-fill composite. However, the bulk-fill composite caused less cuspal flexure than the incrementally placed conventional composite. The bulk-fill composite cured all the way through (4 mm), whereas the conventional composite had lower cure at the bottom of each increment.

Effect of Photoactivation Timing on the Mechanical Properties of Resin Cements and Bond Strength of Fiberglass Post to Root Dentin

OBJECTIVES

This study tested the hypothesis that photoactivation timing and resin cement affect mechanical properties and bond strength of fiberglass posts to root dentin at different depths.

METHODS

Fiberglass posts (Exacto, Angelus) were luted with RelyX Unicem (3M ESPE), Panavia F 2.0 (Kuraray), or RelyX ARC (3M ESPE) using three photoactivation timings: light curing immediately, after three minutes, or after five minutes. Push-out bonding strength, PBS (n=10) was measured on each root region (coronal, middle, apical). The elastic modulus (E) and Vickers hardness (VHN) of the cement layer along the root canal were determined using dynamic indentation (n=5). A strain-gauge test was used to measure post-gel shrinkage of each cement (n=10). Residual shrinkage stress was assessed with finite element analysis. Data were analyzed with two-way analysis of variance in a split-plot arrangement and a Tukey test (α=0.05). Multiple linear regression analysis was used to determine the influence of study factors.

RESULTS

The five-minute delay photoactivation timing significantly increased the PBS for all resin cements evaluated. The PBS decreased significantly from coronal to apical root canal regions. The mean values for E and VHN increased significantly with the delayed photoactivation for RelyX Unicem and decreased from coronal to apical root regions for all resin cements with the immediate-curing timing.

CONCLUSIONS

The PBS of fiber posts to root dentin, E, and VHN values were affected by the root canal region, photoactivation timing, and resin cement type. Shrinkage stress values decreased gradually with delayed photoactivation for all the cements.

Failure Strengths of Composite Additions and Repairs

Purpose

When adding composite to a cured composite restoration, the intent is to achieve the same failure strength as the original restorative material. This study evaluated the failure strengths of added or repaired composite using various chemical and/or mechanical surface treatments.

Methods

Failure strengths were determined using a four-point bending test. Beam-shaped specimens were fabricated by adding new composite to cured composite (Filtek Supreme Ultra). The cured composites were either fresh or aged seven days (N=10-14). The composite surfaces were left unground or were ground before treatment with various combinations of roughening, acid etching, silane, and dental adhesives (conventional Adper SingleBond Plus or new multimode Scotchbond Universal) and/or tribochemistry (CoJet system). Monolithic composite specimens were the control. Failure strengths were statistically analyzed using one-way analysis of variance and the Fisher protected least significant difference (α=0.05).

Results

Failure strengths (mean ± standard deviation) when composite was added to unground freshly cured composites (111±25 MPa) and aged composites using a new multimode adhesive with (102±22 MPa) or without (98±22 MPa) tribochemical treatment were not significantly lower than the monolithic specimens (122±23 MPa). Grinding the surfaces of freshly cured composite significantly reduced failure strength, either with (81±30 MPa) or without (86±31 MPa) use of conventional adhesive. Failure strengths of aged composites were also significantly lower (51±21 MPa with SingleBond Plus), even after tribochemical treatment (71±29 MPa with SingleBond Plus; 73±35 MPa with Silane-Visiobond).

Conclusions

Using a new multimode adhesive when adding composite to freshly cured or aged composite substrates recovered the failure strength to that of the original monolithic composite.

Investigation of treatment options to minimize the effects of acid erosion on enamel

This in vitro study investigated 4 products (containing calcium, phosphate, and/or fluoride) and their ability to reharden enamel softened by hydrochloric acid as compared to hardening with saliva alone. Extracted human molars were embedded and polished, and baseline Vickers hardness (VH) of enamel was measured. Statistical analysis was performed with ANOVA followed by Student-Newman-Keuls post hoc tests (P = 0.05). For all groups, VH decreased significantly after immersion in hydrochloric acid. Fluoride in combination with casein phosphopeptide amorphous calcium phosphate was the most effective treatment for enamel hardness recovery.

Microleakage of resin-modified glass ionomer restorations with selective enamel etching

AIM

Bonding of resin-modified glass ionomers to enamel is an important quality, especially when saliva contamination is inevitable. This study evaluated if microleakage of a resin-modified glass ionomer improves with selective enamel etching, with or without saliva contamination.

METHODS

Class V cavities with the occlusal margin in enamel and the gingival margin on the root were prepared in extracted human permanent teeth and filled with a resin-modified glass ionomer using an acidic primer according to the manufacturer's recommendation or with an additional selective enamel etching step. Preparations were contaminated with saliva before primer application or before restoration placement (n=10). Restored teeth were thermocycled between 5°C and 55°C for 1000 cycles, stained with basic fuchsin, and sectioned. Microleakage distance was measured and analyzed with analysis of variance followed by Duncan post hoc test at a significance level of 0.05.

RESULTS

Enamel microleakage was highest when saliva contamination occurred before the placement of resin-modified glass ionomer. Microleakage distances were significantly reduced in the selective etching groups regardless of saliva contamination. However, selective etching of enamel increased microleakage in cementum. The increase in cementum leakage was significantly higher when saliva contamination occurred before restoration placement.

CONCLUSION

Selective etching reduces enamel microleakage of a resin-modified glass ionomer even with saliva contamination, but it may increase microleakage at the cementum. The severity of microleakage is affected by the timing of saliva contamination.

Microleakage of Resin-Modified Glass Ionomer Restorations With Selective Enamel Etching

SUMMARY Aim : Bonding of resin-modified glass ionomers to enamel is an important quality, especially when saliva contamination is inevitable. This study evaluated if microleakage of a resin-modified glass ionomer improves with selective enamel etching, with or without saliva contamination. Methods : Class V cavities with the occlusal margin in enamel and the gingival margin on the root were prepared in extracted human permanent teeth and filled with a resin-modified glass ionomer using an acidic primer according to the manufacturer's recommendation or with an additional selective enamel etching step. Preparations were contaminated with saliva before primer application or before restoration placement (n=10). Restored teeth were thermocycled between 5°C and 55°C for 1000 cycles, stained with basic fuchsin, and sectioned. Microleakage distance was measured and analyzed with analysis of variance followed by Duncan post hoc test at a significance level of 0.05. Results : Enamel microleakage was highest when saliva contamination occurred before the placement of resin-modified glass ionomer. Microleakage distances were significantly reduced in the selective etching groups regardless of saliva contamination. However, selective etching of enamel increased microleakage in cementum. The increase in cementum leakage was significantly higher when saliva contamination occurred before restoration placement. Conclusion : Selective etching reduces enamel microleakage of a resin-modified glass ionomer even with saliva contamination, but it may increase microleakage at the cementum. The severity of microleakage is affected by the timing of saliva contamination.

Incremental filling technique and composite material--part I: cuspal deformation, bond strength, and physical properties

OBJECTIVES

To evaluate the effect of composite resins (one conventional and two low-shrink composites) and filling techniques on cuspal strains (CS), microtensile bond strength (μTBS), composite ultimate tensile strength (UTS), and mechanical properties of the composites at various depths in molars with large Class II restorations.

MATERIALS AND METHODS

One hundred seventeen human molars received standardized Class II mesio-oclusal-distal cavity preparations and restorations with three composites (Filtek LS [3M-ESPE]; Aelite LS [BISCO]; and Filtek Supreme [3M-ESPE]) using three filling techniques (bulk, eight increments, and 16 increments). CS was measured using strain gauges, after which the same restored teeth were used to assess μTBS and UTS. The elastic modulus (E) and Vickers hardness (VH) at different depths were determined from microhardness indentations. The CS, μTBS, UTS, E, and VH data were statistically analyzed using split-plot analysis of variance and Tukey test (p=0.05).

RESULTS

The CS was higher when using 16 increments. The 'low-shrink' composites caused lower CS. The μTBS and UTS were similar for eight- and 16-increment techniques and higher when compared to the bulk filling in all composites. E and VH were constant through the depth when applied in eight or 16 increments.

CONCLUSIONS

Type of composite and filling technique affected the CS, μTBS, UTS, and mechanical properties of large Class II restorations. The eight-increments filling technique resulted in generally less CS with the same μTBS and UTS than was obtained with 16 increments, without affecting E and VH through the depth of the composites.

Incremental filling technique and composite material--part II: shrinkage and shrinkage stresses

OBJECTIVES

Finite element analysis (FEA) was used to study polymerization shrinkage stress in molars restored with composites and to correlate those stresses with experimentally measured tooth deformation.

METHODS

Three composites (Filtek LS, Aelite LS Posterior, Filtek Supreme) and three filling techniques (bulk, 2.0-mm increments, and 1.0-mm increments) for restoring a molar were simulated in a two-dimensional FEA. Polymerization shrinkage was modeled using post-gel shrinkage, which was measured using the strain gauge technique (n=10). Cuspal tooth deformation, measured at the buccal and lingual surfaces with strain gauges in a laboratory study, was used to validate the analysis. Residual shrinkage stresses were expressed in modified von Mises equivalent stresses. Linear Pearson correlations were determined between the laboratory and FEA results.

RESULTS

Post-gel shrinkage values (in volume %) were: Filtek LS (0.11 ± 0.03) < Aelite LS Posterior (0.51 ± 0.02) < Filtek Supreme (0.62 ± 0.09). The 1.0-mm increment filling caused substantially higher stresses and strains in the cervical enamel region. Significant correlations were found between: elastic modulus and FEA strain, elastic modulus and FEA stress, post-gel shrinkage and FEA strain, post-gel shrinkage and FEA stress, FEA strain and cuspal deformation by strain gauge, and FEA stress and cuspal deformation by strain gauge (p<0.05).

CONCLUSIONS

Increasing the number of increments and high post-gel shrinkage and/or elastic modulus values caused higher stresses in the remaining tooth structure and tooth/restoration interface. Cuspal deformation measured with the strain gauge method validated the finite element analyses.

Three-point bending testing of fibre posts: critical analysis by finite element analysis

AIM

To evaluate the effect of taper, specimen supports and the isotropic and orthotropic properties of the posts on flexure and stress response during three-point bending using finite element analysis.

METHODOLOGY

A three-dimensional finite element model of a fibre post was created. The occlusal portion was cylindrical whilst the apical portion was tapered. Five different support positions were evaluated during a simulated three-point bending test: M1 - support distance of 10 mm centralized and no tilt; M2 - 10 mm centralized with tilt; M3 - 10 mm not centralized and no tilt; M4 - 10 mm not centralized with tilt; M5 - 6 mm not centralized with no tilt. A sixth post model (M6) was a centralized post without tapered section. The applied properties were elastic and orthotropic.

RESULTS

Tilting the tapered posts to level them in the test setup had little effect on the outcome. Flexure increased when 50% of the bent portion involved taper (M1, M2). If only 20% of the bent post involved taper (M3, M4), the flexure values were close to M6 (no taper). The orthotropic properties also caused increased flexure compared to an isotropic post. Maximum stresses were only a little higher when 50% of the bend structure involved taper, whilst the orthotropic properties had little effect.

CONCLUSIONS

Regardless of levelling, the flexural stress determination with tapered fibre posts in the three-point bending test was valid as long as the tapered portion was limited in length.

Understanding Contradictory Data in Contraction Stress Tests

The literature shows contradictory results regarding the role of composite shrinkage and elastic modulus as determinants of polymerization stress. The present study aimed at a better understanding of the test mechanics that could explain such divergences among studies. The hypothesis was that the effects of composite shrinkage and elastic modulus on stress depend upon the compliance of the testing system. A commonly used test apparatus was simulated by finite element analysis, with different compliance levels defined by the bonding substrate (steel, glass, composite, or acrylic). Composites with moduli between 1 and 12 GPa and shrinkage values between 0.5% and 6% were modeled. Shrinkage was simulated by thermal analogy. The hypothesis was confirmed. When shrinkage and modulus increased simultaneously, stress increased regardless of the substrate. However, if shrinkage and modulus were inversely related, their magnitudes and interaction with rod material determined the stress response.

Characteristics of non-carious cervical lesions--an ex vivo study using micro computed tomography

The aetiology of non-carious cervical lesions (NCCLs) is not well understood and still controversial. The aim of this ex-vivo study was to examine the morphological characteristics of NCCLs for clinical evidence of enamel loss above the cemento-enamel junction (CEJ) as suggested by the abfraction theory. Fifty extracted human teeth with various types of NCCLs were collected and scanned by micro computed tomography. The reconstructed three-dimensional models were evaluated from multiple aspects, including longitudinal cross-section series. The location of internal line angle and proximal exits of the lesions were evaluated in relation to the level of CEJ. The coronal margins of the lesions were inspected for evidence of enamel loss above the CEJ using the bucco-lingual longitudinal sectional images. Coronal margins of the lesions were located along and/or under the CEJ for all of the 50 samples. In most of the lesions, regardless of lesion type, the proximal exits and internal line angles were located below the CEJ. This study did not detect clinical evidence of enamel loss above the occlusal margin of NCCLs as would have been expected according to the general abfraction mechanism.

Can Fiber Posts Increase Root Stresses and Reduce Fracture?

The clinical success of fiber posts has been attributed to their lower elastic modulus. The tested hypothesis was that fiber posts could lead to lower risk of post debonding and lower risk of root fracture, despite an increase in root stresses. Stress analyses were carried out with a 3D finite element model of a premolar restored with a metallic or a fiber post. Bonded and non-bonded post/cement interface conditions were simulated. We calculated risk-of-fracture indices by determining the highest principal stress values divided by the tensile strength. Shear stresses along the post/cement interface were analyzed for the bonded models. Compared with the premolar restored with a metallic post, the fiber post generated lower stresses along the interface and higher stresses in the root. However, with the fiber post, fracture was less likely to occur in the root, since its core and post fracture indices were higher.

Changes in compaction stress distributions in roots resulting from canal preparation

AIM

To examine if canal enlargement with instruments of controlled taper leads to more uniform stress distributions within a root, thereby reducing fracture susceptibility.

METHODOLOGY

Finite element models of a mandibular incisor were constructed with round and oval canal profiles, based on measurements from extracted teeth. The shapes of rotary nickel-titanium instruments (ProTaper F1, F2, and F3 and ProFile size 30, 0.04 taper and size 30, 0.06 taper; Dentsply Maillefer) were superimposed on the canals. Equivalent stresses and circumferential stresses in the root were calculated for a compaction load.

RESULTS

The highest stresses were found at the canal wall. Round canals showed lower uniform distributions, whilst oval canals showed uneven distributions with high concentrations at the buccal and lingual canal extensions and greater stresses in the coronal and middle thirds than in the apical third. Preparation of round canals introduced only small circumferential stress increases in the apical half; preparation of oval canals produced substantial reductions where the canal was enlarged to a smooth round shape. Even where fins were not completely eliminated, the maximum stresses were still reduced by up to 15%. External distal and mesial surfaces of roots with oval canals showed moderate stress concentrations that were minimally affected by preparations, whilst stress concentrations emerged on roots with round canals when preparation sizes increased.

CONCLUSIONS

The potential for reducing fracture susceptibility exists as a result of round canal profiles achieved and smooth canal taper. Even when fins were not contacted by the instrument, stresses within the root were lower and more evenly distributed than before preparation.