Cementation of prosthetic restorations: from conventional cementation to dental bonding concept

Current Protocols for Resin-Bonded Dental Ceramics

Resin-bonded ceramic restorations are common treatment options. Clinical longevity of resin-bonded ceramic restorations depends on the quality and durability of the resin-ceramic bond. The type and composition of the specific ceramic determines the selection of the most effective bonding protocol. Such protocol typically includes a surface pretreatment step followed by application of a priming agent. Understanding of fundamental ceramic properties and chemical compositions enables the clinician to make proper material selection decisions for clinically successful and long-lasting restorations. Based on research accrued over the past decades, this article reviews and discusses current resin-bonding protocols to most commonly used dental ceramics.

Luting indirect restorations with resin cements versus composite resins: Effects of preheating and ultrasound energy on film thickness

OBJECTIVE

This study aims to evaluate and compare the film thickness obtained with a resin cement and two composite resins, preheated and/or ultrasonically vibrated, as luting agents.

MATERIALS AND METHODS

One hundred and twenty-six (126) pairs of resin discs were randomly assigned to six experimental groups (n = 21) according to luting agent (Variolink Esthetic LC, IPS Empress Direct or Estelite Omega) and cementation technique (preheating at 68°C and/or ultrasonic vibration). Specimens were luted by applying a controlled force. Following sectioning and film thickness measurement through field emission gun scanning electron microscopy, statistical analysis was carried out considering a 5% significance level.

RESULTS

Statistically significant lower film thickness was observed in Variolink Esthetic LC group when compared to all composite resin groups (p < 0.001), except IPS Empress Direct preheated and ultrasonically vibrated group (p = 0.073). IPS Empress Direct with ultrasonic vibration yielded statistically lower film thickness values than Estelite Omega groups, regardless of luting technique (p < 0.05). Ultrasonically vibrated Estelite Omega groups showed statistically lower film thickness values than solely preheated groups (p < 0.05).

CONCLUSIONS

Both Variolink Esthetic LC and IPS Empress Direct preheated and ultrasonically vibrated provided the lowest film thickness. The addition of ultrasonic vibration during cementation proved to be effective in reducing film thickness of both tested composite resins.

CLINICAL SIGNIFICANCE

The cementation technique will have variable results depending on the luting material. Adhesive cementation protocols with composite resins should mainly consider ultrasonic vibration, but also preheating, as strategies for reducing film thickness. The tested resin cement, alongside with IPS Empress Direct composite resin preheated and ultrasonically vibrated, provided the lowest film thickness among the tested materials and techniques.

Effect of silver diamine fluoride, potassium nitrate, and glutaraldehyde in reducing the post vital tooth preparation hypersensitivity: A randomized controlled trial

Aim

Hypersensitivity is the most common clinical problem which is encountered by most of dental patients undergoing a vital tooth preparation for a fixed crown prosthesis. The aim of this study is to evaluate the effect of silver diamine fluoride, potassium nitrate, and glutaraldehyde in reducing dentinal hypersensitivity following vital tooth preparation.

Settings and Design

This study is a randomized control trial performed on 119 teeth of 68 patients who are in need of fixed prosthesis treatment.

Materials and Methods

After a thorough clinical examination, patients were allocated into any of the randomly assigned four groups (Control, silver diamine fluoride, potassium nitrate, and glutaraldehyde) and the level of hypersensitivity was measured by blasting air on the surface of tooth at five different intervals (before preparation, after preparation, after application of desensitizers, before cementation and after a follow up period of about 30 days) and is graded using Schiff 's cumulative hypersensitivity index.

Statistical Analysis Used

Kruskal wallis test is used to compare the rate of sensitivity between the 4 groups. Friedman and Wilcoxon test is used to compare the rate of sensitivity at 5 different intervals.

Results

All the desensitizers used in this study reduced the level of hypersensitivity. Among which, silver diamine fluoride was found to be more effective after application, before cementation, and after a follow up period of about 30 days followed by GLUMA and potassium nitrate.

Conclusion

The results of this study suggest that silver diamine fluoride was found to be more effective after application, before cementation of the definitive prosthesis and after a follow up period of 30 days.

Investigating the mechanophysical and biological characteristics of therapeutic dental cement incorporating copper doped bioglass nanoparticles

OBJECTIVE

This study was investigated the mechanophysical properties of zinc phosphate cement (ZPC) with or without the copper doped bioglass nanoparticles (Cu-BGn) and their biological effect on dental pulp human cells and bacteria.

MATERIALS AND METHODS

Cu-BGn were synthesized and characterized firstly and then, the experimental (Cu-ZPC) and control (ZPC) samples were fabricated with similar sizes and/or dimensions (diameter: 4 mm and height: 6 mm) based on the International Organization of Standards (ISO). Specifically, various concentrations of Cu-BGn were tested, and Cu-BGn concentration was optimized at 2.5 wt% based on the film thickness and overall setting time. Next, we evaluated the mechanophysical properties such as compressive strength, elastic modulus, hardness, and surface roughness. Furthermore, the biological behaviors including cell viability and odontoblastic differentiation by using dental pulp human cells as well as antibacterial properties were investigated on the Cu-ZPC. All data were analyzed statistically using SPSS® Statistics 20 (IBM®, USA). p < 0.05 (*) was considered significant, and 'NS' represents nonsignificant.

RESULTS

Cu-BGn was obtained via a sol-gel method and added onto the ZPC for fabricating a Cu-ZPC composite and for comparison, the Cu-free-ZPC was used as a control. The film thickness (≤ 25 µm) and overall setting time (2.5-8 min) were investigated and the mechanophysical properties showed no significance ('NS') between Cu-ZPC and bare ZPC. However, cell viability and odontoblastic differentiation, alkaline phosphate (ALP) activity and alizarin red S (ARS) staining were highly stimulated in the extracts from the Cu-ZPC group compared to the ZPC group. Additionally, the antibacterial test showed that the Cu-ZPC extracts were more effective than the ZPC extracts (p < 0.05).

SIGNIFICANCE

Cu-ZPC showed adequate mechanophysical properties (compressive strength, hardness, and surface roughness) and enhanced odontoblastic differentiation as well as antibacterial properties compared to the ZPC-only group. Based on the findings, the fabricated Cu-ZPC might have the potential for use in the field of dental medicine and clinical applications.

Cement selection criteria for full coverage restorations: A comprehensive review of literature

BACKGROUND

Proper cement selection in fixed prosthesis plays a determinative role in providing long-term serviceability, retention, caries prevention, and patient satisfaction. This study, reviews different luting agent characteristics and their application based on different clinical situations and different types of full coverage restorations.

MATERIAL AND METHODS

An electronic search was conducted through PubMed, Medline, and Google scholar using following keywords or combinations: restoration, full coverage, PFM, porcelain fused to metal, all ceramic, zirconia, ceramic, casting, fixed partial denture, cement*, dental cement, cement selection, and retention. The most related articles were selected for review.

RESULTS

Choosing a proper luting agent is highly dependent on scientific knowledge regarding the characteristics of restorative materials and luting agents. Conventional cements could be indicated in various situations; however, some restorative materials or clinical situations call for resin-cements to provide predictable retention, support, and durability.

CONCLUSIONS

Conscious selection of retentive cement for each type of restoration/material is necessary to provide predictable successful treatment and reduce the potential complications. Key words:Adhesive cement, dental bridgework, dental cements, dental crowns, dental porcelain, prostheses and implants.

Effect of aging on color stability and bond strength of dual-cured resin cement with amine or amine-free self-initiators

This study aimed to evaluate the effect of aging on the color stability and bond strengths of dual-cured resin cements containing amine or amine-free self-initiators. Three dual-cured and one light-cured resin cements were used. The covered (by lithium disilicate ceramic disks) and uncovered groups (n=10) were included. Color measurements were tested after 24 h, 10,000 and 20,000 thermal cycles (TCs). Micro-shear bond strengths (µSBS) were tested after 24 h, 10,000 and 20,000 TCs, and failure modes were analyzed (n=14). Two-way ANOVA and Tukey's test were implemented for color difference (ΔE*_ab) and µSBS (α=0.05). The mean ΔE*_ab difference was significant among groups (p<0.001). The lowest ΔE*_ab values were obtained for dual-cured resin cement with amine-free self-initiators dual-cured cement after aging in all dual-cured resin cements, and the µSBS of the dual-cured resin cements on ceramic was significantly higher than that of the light-cured ones after aging (p<0.001).

The impact of liquefaction disaster on farming systems at agriculture land based on technical and psychosocial perspectives

This research aims to determine the attitudes of the farmers whose lands are affected by liquefaction in Jono Oge, Central Sulawesi Province, The Republic of Indonesia. The methods used here were integrated survey and experimental design. The survey approach was intended to figure out the attitudes of the farmers viewpoints: (1) to return to their activities on the agricultural lands affected by liquefaction; (2) to consume their own agricultural products; and (3) of their willingness to be relocated. The experimental design approach was used to figure out the effectiveness of organic material input combined with the SP-36 fertilizer. The obtained results were analyzed using the Likert Scale, diversity test, correlational test, and regression test. The results showed that the farmers persevered farming on the lands affected by liquefaction (Index = 88.82%) yet refused to consume their own agricultural products with the reason that corpses remained buried beneath their lands (Index = 27.82%); and they also refused to be relocated (Index = 28.80%). The continued production suitability of the affected land was also investigated. Terrain profile identification results in Jono Oge showed the disaster impact was dominantly landslide as it still showed a clear characteristic horizon between the topsoil and the sub soil. This contrasts to terrain at Petobo, Central Sulawesi Province, where the high mix of the topsoil with the sub soil of agricultural land affected by liquefaction, prevented demarcation of the horizon. The land treatment of organic material and SP-36 fertilizer showed that the combined dose (M) of 40-kg ha-1 with P 300-kg ha-1 had the highest effect by changing the field pH from 5.7 to 6.41, increased the availability of P and increased the corncob indicator plant weight. Based on these indications, the lands affected by the liquefaction in Jono Oge can still be used as agricultural lands through restoration, from both social and technical aspects.

Influence of Bioactive, Resin and Glass Ionomer luting cements on the fracture loads of dentin bonded ceramic crowns

Objective:

To investigate the failure loads of dentin bonded all-ceramic crowns when luted with Bioactive, resin and glass ionomer cements (GIC) in an in-vitro setting.

Methods:

This study was conducted at King Saud University, Saudi Arabia, from Nov.2018 to March 2019. In this study, 60 premolar teeth were prepared for dentin-bonded ceramic crowns. Lithium disilicate ceramic crowns fabricated using CAD-CAM technique were cemented to teeth using Bioactive (ACITVA), Resin (Nexus 3 Gen) and GIC (Ketac Cem- Maxicap). Half of the bonded specimens in each group were thermocycled (50000 cycles), however the remaining half were not aged (n=10). Fracture loads of bonded crowns were assessed by exposing them to static axial occlusal loads (1mm/min) using a round ended metal probe in a Universal testing machine. Means and standard deviations among the study groups were compared with ANOVA and Tukey-Kramer multiple comparisons test.

Results:

Highest failure loads were observed in resin group without ageing (thermocycling) (689.13±89.41 N), however, the lowest loads were observed in GIC specimens with ageing (243.16±49.03 N). Among non-aged samples, failure loads for Bioactive (480.30±47.26 N) group were less than Resin (689.13±89.41 N) samples but higher than GIC (307.51±45.29 N) specimens respectively. Among the aged specimens, Bioactive (404.42±60.43 N) showed significantly higher failure loads than GIC (243.16±49.03 N), however lower failure loads than Resin (582.33±95.95 N) samples.

Conclusions:

Dentin boned crowns with resin cementation showed higher failure loads than Bioactive and GIC luted crowns. Crowns luted with Bioactive cement showed acceptable failure loads for use as restoration on anterior teeth.

Influence of N-(2-hydroxyethyl)acrylamide addition in light- and dual-cured resin cements

OBJECTIVE

To develop experimental light-cured (L) and dual-cured (D) resin cements containing N-(2-hydroxyethyl)acrylamide and evaluate the physicochemical and optical properties.

METHODS

Experimental resin cements were formulated using bisphenol A-glycidyl dimethacrylate (70%) and 2-hydroxyethyl methacrylate (30%), in the control groups, and, bisphenol A-glycidyl dimethacrylate (70%) and N-(2-hydroxyethyl)acrylamide (30%). Polymerization kinetics were evaluated by differential scanning calorimetry (n = 3), softening in solvent (ΔKHN) evaluated by the difference of Knoop microhardness before (KHN₁) and after (KHN₂) ethanol solution immersion (n = 5), radiopacity in mmAl (n = 5), film thickness (n = 3) and color stability were evaluated. Mechanical properties as ultimate tensile strength (UTS) and micro-shear bond strength (μSBS) were analyzed immediately and after 6 months. Results were analyzed using ANOVA, Tukey's test and Student's t-test (α = 0.050).

RESULTS

The L_HEAA1 group had no statistical difference from the control group regarding polymerization kinetics, KHN₁, ΔKHN and color stability (p > 0.050). In dual-cured cements, the acrylamide groups presented a lower degree of conversion and higher ΔKHN than the D_HEMA0.6 group, which obtained a higher rate of polymerization (p < 0.050). There was no statistical difference in radiopacity and film thickness (p > 0.050). Dual-cured cements with N-(2-hydroxyethyl)acrylamide showed higher color change than methacrylates. Immediate mechanical properties were lower for acrylamide groups (p < 0.050), with higher hydrolytic stability.

CONCLUSIONS

The addition of N-(2-hydroxyethyl)acrylamide negatively affected the properties of the dual-cured resin cements. LHEAA1 did not differ in physicochemical and optical properties from the control, with higher hydrolytic stability.

CLINICAL SIGNIFICANCE

The results of the study indicate that acrylamides increased mechanical properties over time independently of the curing system mode, with more hydrolytic stability. The clinical performance of experimental resin cements should be evaluated.

Rely XTM U200 versus Rely XTM ARC: uma comparação da resistência à microtração

Resumo Introdução Os cimentos resinosos são extensivamente utilizados na fixação de restaurações indiretas de cerâmica e cerômero, sendo classificados em duas categorias: os cimentos resinosos convencionais, que não apresentam uma adesão inerente à estrutura dental e requerem o uso de um sistema adesivo e os cimentos resinosos autoadesivos, que não requerem um tratamento adesivo prévio do substrato dentário. Objetivo Avaliar a resistência de união de dois cimentos resinosos, convencional e autoadesivo, quando utilizados na cimentação de restaurações cerâmicas e ceroméricas, trazendo elementos para propiciar melhor compreensão da interação adesiva em procedimentos de cimentação com as referidas categorias de cimentos resinosos. Material e método Dentes humanos (n=20), cedidos pelo banco de dentes da Universidade Federal de Alfenas (UNIFAL), foram preparados para que cilindros de cerâmica ou de cerômero fossem cimentados utilizando-se dois tipos de cimentos resinosos (autoadesivo e convencional). Após a cimentação, 20 palitos foram obtidos e submetidos ao teste de tração, avaliando-se a força necessária para a fratura. Os valores obtidos foram submetidos à análise estatística empregando-se a análise de variância (ANOVA) e o teste de Tukey. Resultado As forças mínimas e máximas necessárias ao rompimento do cimento convencional foram superiores às mesmas requeridas para o rompimento da união promovida pelo cimento autoadesivo, bem como as medianas e as médias aritméticas, independentemente do material restaurador empregado. O teste de Tukey demonstrou que as diferenças entre os cimentos empregados são estatisticamente significantes, independentemente do material restaurador. Conclusão Os resultados deste trabalho sugerem que o material utilizado para a confecção dos corpos de prova (cerâmica ou cerômero) não influenciou na resistência à tração, sendo que o cimento convencional apresentou valores superiores de resistência.

Shear bond strength of luting cements to fixed superstructure metal surfaces under various seating forces

PURPOSE

In this study, the shear bond strengths (SBS) of luting cements to fixed superstructure metal surfaces under various seating forces were investigated.

MATERIALS AND METHODS

Seven different cements [Polycarboxylate (PCC), Glass-Ionomer (GIC), Zinc phospahate (ZPC), Self-adhesive resin (RXU), Resin (C&B), and Temporary cements ((RXT) and (TCS))] were bonded to a total number of 224 square blocks (5×5×3 mm) made of one pure metal [Titanium (CP Ti) and two metal alloys [Gold-Platinum (Au-Pt) and Cobalt-Chrome (Co-Cr)] under 10 N and 50 N seating forces. SBS values were determined and data were analyzed with 3-way ANOVA. Pairwise comparisons and interactions among groups were analyzed with Tukey's simultaneous confidence intervals.

RESULTS

Overall mean scores indicated that Co-Cr showed the highest SBS values (1.96±0.4) (P<.00), while Au-Pt showed the lowest among all metals tested (1.57±0.4) (P<.00). Except for PCC/CP Ti, RXU/CP Ti, and GIC/Au-Pt factor level combinations (P<.00), the cements tested under 10 N seating force showed no significantly higher SBS values when compared to the values of those tested under 50 N seating force (P>.05). The PCC cement showed the highest mean SBS score (3.59±0.07) among all cements tested (P<.00), while the resin-based temporary luting cement RXT showed the lowest (0.39±0.07) (P<.00).

CONCLUSION

Polycarboxylate cement provides reliable bonding performance to metal surfaces. Resin-based temporary luting cements can be used when retrievability is needed. GIC is not suitable for permanent cementation of fixed dental prostheses consisting of CP Ti or Au-Pt substructures.

Effect of previous photoactivation of the adhesive system on the color stability and mechanical properties of resin components in ceramic laminate veneer luting

STATEMENT OF PROBLEM

The color stability and mechanical properties of luting agents influence the esthetics and longevity of ceramic restorations. However, studies evaluating the color changes and mechanical properties of luting agents under ceramic laminates activated by using different methods are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of different modes of photoactivation on the nanohardness and elastic modulus of resin cements and dental adhesives and on the color stability of ceramic laminate veneers.

MATERIAL AND METHODS

Forty-four lithium disilicate blocks (7×8×0.6 mm) were cemented onto bovine enamel and divided into 4 groups according to the polymerization light (Radii-Cal or Valo) used and the mode of activation of the dental adhesive (no previous photoactivation or previous photoactivation). Single Bond Universal dental adhesive and RelyX Veneer resin cement were used in all experimental groups. Color stability was measured using a UV-2450 ultraviolet-visible spectrophotometer before and after ultraviolet-B artificial accelerated aging (n=8). The nanohardness and the elastic modulus of the adhesive and resin cement were measured using a nanohardness tester (n=3). The color stability and mechanical properties were measured and analyzed using ANOVA and the Tukey least significant difference test (α=.05).

RESULTS

No difference in color stability or mechanical properties of the resin cement among the polymerization lights was detected (P>.05). Specimens that underwent previous photoactivation of the adhesive using the Valo polywave unit exhibited higher elastic modulus values than those that did not undergo previous photoactivation (P<.001).

CONCLUSIONS

The Valo polywave polymerization light improved mechanical properties and color stability more than the Radii-Cal unit. Previous activation of the dental adhesive in the dental enamel with the Valo polywave polymerization light yielded more satisfactory results.

Microtensile bond strength of resin cement primer containing nanoparticles of silver (NAg) and amorphous calcium phosphate (NACP) to human dentin

PURPOSE

The purpose of the current study was to evaluate the effect of incorporating nanoparticles of silver (NAg) and amorphous calcium phosphate (NACP) into a self-etching primer of a resin cement on the microtensile bond strength of dentin, regarding the proven antibacterial feature of NAg and remineralizing effect of NACP.

MATERIALS AND METHODS

Flat, mid-coronal dentin from 20 intact extracted human third molars were prepared for cementation using Panavia F2.0 cement. The teeth were randomly divided into the four test groups (n=5) according to the experimental cement primer composition: cement primer without change (control group), primer with 1% (wt) of NACP, primer with 1% (wt) of physical mixture of NACP+Nag, and primer with 1% (wt) of chemical mixture of NACP+Nag. The resin cement was used according to the manufacturer's instructions. After storage in distilled water at 37℃ for 24 h, the bonded samples were sectioned longitudinally to produce 1.0 × 1.0 mm beams for micro-tensile bond strength testing in a universal testing machine. Failure modes at the dentin-resin interface were observed using a stereomicroscope. The data were analyzed by one-way ANOVA and Tukey's post-hoc tests and the level of significance was set at 0.05.

RESULTS

The lowest mean microtensile bond strength was obtained for the NACP group. Tukey's test showed that the bond strength of the control group was significantly higher than those of the other experimental groups, except for group 4 (chemical mixture of NACP and NAg; P=.67).

CONCLUSION

Novel chemical incorporation of NAg-NACP into the self-etching primer of resin cement does not compromise the dentin bond strength.

Evaluation of color changes of dental luting materials in food colorant solutions

BACKGROUND

The purpose of this study was to compare the color stability and water absorption of 3 commercially available resin cements in vitro by storing them in 0.15% erythrosine, dark brown and sunset yellow for 30 days.

METHODS

2 self-adhesive resin cements and 1 dual/light curing, resin-based dental luting material were evaluated (total 120 samples). The CIE L, a, b of 10 mm diameter-2.0 mm height disk shaped samples was measured using a spectrophotometer for color stability on a white background, 10 mm diameter-1.0 mm height disk shaped samples were measured for water absorption before and after storage in food colorant solutions.

RESULTS

The self-adhesive resin cement-sunset yellow group caused the most severe discoloration (27.89 ± 3.64) that is clinically unacceptable. The lowest discoloration was seen in the self-adhesive resin cement control group (3.35 ± 1.13). The highest water absorption was observed in the self-adhesive resin cement-dark brown group (2.41 ± 0.60) and the lowest water absorption in the dental luting material-control group (0.65 ± 0.17).

CONCLUSIONS

Storage food colorant solutions affected the color stability and water absorption of different resin cement materials.

Resistência de união de diferentes cimentos resinosos a cerâmica à base de dissilicato de lítio

Resumo Introdução O sucesso de restaurações indiretas depende de uma adequada união entre o cimento e o substrato dental. Portanto, a seleção e o conhecimento das características dos agentes cimentantes são importantes para a retenção da restauração indireta. Objetivo Avaliar a resistência de união de dois cimentos resinosos diferentes à cerâmica de dissilicato de lítio. Metodologia Dois grupos experimentais foram confeccionados: cimento resinoso convencional (Grupo CRC) e cimento resinoso autoadesivo (Grupo CRA). Para isso, dez discos de cerâmica de dissilicato de lítio (10 mm) foram pré-fabricados e, sobre cada disco, foram confeccionados quatro postes de cimento (0,7×1,0 mm), obtendo-se um total de 20 amostras de cada tipo de cimento. Os discos tiveram o mesmo tratamento de superfície para os dois grupos, que é padrão para as cerâmicas ricas em sílica, de acordo com o protocolo estabelecido pelo fabricante. As amostras foram submetidas ao teste de microcisalhamento para avaliar a resistência de união entre o cimento e a cerâmica. Posteriormente, o modo de falha foi analisado em microscópio ótico. Resultado Os dados obtidos foram submetidos a teste estatístico. Foi observado que o grupo CRC apresentou maiores valores de resistência de união (15,29 MPa) em relação ao grupo CRA (12,41 MPa). Na análise do modo de falha, nenhuma amostra obteve fratura do tipo adesiva. Em ambos os grupos, CRC (75%) e CRA (65%), obtiveram-se mais falhas do tipo mista, seguidas pela falha coesiva. Conclusão Ambos os cimentos apresentaram adesão à cerâmica. O cimento resinoso convencional apresentou maior adesão a cerâmica à base de dissilicato de lítio que o cimento resinoso autoadesivo.

Selected physical properties of new resin-modified glass ionomer luting cements

STATEMENT OF PROBLEM

Two resin-modified glass ionomer (RMGI)-based luting agents have been recently marketed without independent reports of their physical properties.

PURPOSE

The purpose of this in vitro study was to evaluate selected physical properties of 2 newly marketed RMGI luting agents and compare the findings with traditional materials.

MATERIAL AND METHODS

Specimens (N=12) of Nexus RMGI, UltraCem, GC Fuji Cem 2, and RelyX Luting Plus were fabricated using standardized molds for flexural strength and fracture toughness according to manufacturer recommendations and stored in physiologic phosphate-buffered saline solution at 37°C until testing. Specimens were tested at 1 and 24 hours, 1 week, and 1 month. Mean values for flexural strength, flexural modulus, flexural toughness, and fracture toughness were determined. Additionally, film thickness (N=12) for each material was determined following Amerian National Standards Association/American Dental Association (ANSI/ADA) specifications. Mean results were analyzed with Kruskal-Wallis and Mann-Whitney U tests (α=.05).

RESULTS

All luting agents exhibited a similar film thickness that met ANSI/ADA requirements for aqueous-based luting agents. Nexus RMGI surprisingly demonstrated significantly greater flexural strength and fracture toughness at 1 hour, which decreased significantly at 24 hours, making it similar to the other materials evaluated. All materials had similar flexural strength values at 7 days.

CONCLUSIONS

Physical property performance was material dependent. Nexus RMGI demonstrated greater early physical properties that were significantly less at 24 hours. UltraCem, GC Fuji Cem 2, and RelyX Luting Plus demonstrated the increasing physical property development that is normally associated with polyalkenoate-based systems.

Influence of root dentin treatment on the push-out bond strength of fiber posts

The aim of the present study was to assess whether different dentin conditioning protocols with different acids [phosphoric acid, ethylene diamine tetra acetic acid (EDTA), and polyacrylic acid (PAA)] influence the bond strength of fiber posts along the radicular depth when luted with self-adhesive resin cement. Twenty single-rooted teeth were randomly divided into four experimental groups (n = 5) according to dentin treatment: Group 1: no treatment; Group 2: etching with 35 % phosphoric acid for 10 s; Group 3: 17 % EDTA application for 60 s; and Group 4: conditioning with 25 % PAA for 30 s. RelyX Fiber Posts were luted with the self-adhesive resin cement RelyX Unicem 2 Automix (3M ESPE). Roots were transversally sectioned into nine 1-mm thick specimens, three corresponding to each root third and a push-out test was performed. Data were analyzed by two-way ANOVA and Tukey test (p < 0.05). Failure mode was determined and specimens with representative failures for each group were observed under scanning electron microscopy. According to the results, dentin treatment influenced the bond strength (p < 0.001), whereas the root third did not (p > 0.05). Fiber posts luted after treating dentin with phosphoric acid, and PAA exhibited the highest push-out bond strength values, while the lowest were obtained after EDTA application. Intermediate results were obtained when dentin was not conditioned. In conclusion, the bond strength of the self-adhesive resin cement RelyX Unicem 2 improves when root dentin is treated with 35 % phosphoric acid or 25 % PAA, before fiber posts luting irrespective of the root depth.

Influence of volume and activation mode on polymerization shrinkage forces of resin cements

The concern with the polymerization shrinkage of restorative resin composites also applies to resin cements. The aim of this study was to evaluate the influence of volume and polymerization mode on forces generated during polymerization shrinkage (FGPS) of resin cements. Two light-cured resin cements--Variolink II (VL; Ivoclar Vivadent) and Nexus 3 (NX; Kerr)--and two self-cured resin cements - Multilink (ML; Ivoclar Vivadent) and Cement Post (CP; Angelus) - were inserted between two rectangular steel bases (6x2 mm) with distance set at 0.1, 0.3 and 0.5 mm, establishing a variation of volume. These steel bases were attached to a universal test machine with 50 kg load cell and forces (N) were registered for 10 min. Values of maximum forces generated by each material were subjected to two-way ANOVA and Tukey's test for individual comparisons (α=0.05). VL, NX and CP developed increasing FGPS as the volume of material increased, while ML presented the opposite behavior. It may be concluded that higher volume increases FGPS even with a concomitant decrease of C-factor, unless the resin cements present lower force generation rates as a function of time in combination with a low C-factor, resulting in stress relief and consequently lower values of FGPS.

Combined treatment with laser sintering and zirconium: a case report of dentinogenesis imperfecta

Osteogenesis imperfecta (OI) is a heterogeneous disorder of connective tissue that manifests mainly as skeletal deformity and bone fragility. Dentinogenesis imperfecta (DI) is sometimes an accompanying symptom of OI. The treatment protocol of these patients varies according to the clinical appearance. The case report here describes complete mouth rehabilitation of an 18-year-old male patient with OI and DI using direct metal laser sintering (DMLS) technique of metal-ceramic restorations and zirconium all-ceramic crowns. DMLS is an additive metal fabrication technology that is simpler, more precise, and healthier than conventional manufacturing and can be remarkably cost effective. Moreover, the technique affords highly accurate production of fixed partial dentures with ideal marginal fit and excellent mechanical properties. The patient was treated using a multidisciplinary strategy that focused on controlling caries, protecting teeth from further wear, obtaining an appropriate vertical dimension, and providing soft tissue support to return the facial profile to a normal appearance using new technology in the field of prosthetics.