The failure rate of adhesively retained composite core build-ups in comparison with metal-added glass ionomer core build-ups

Influence of geometric dimensions on early failures of adhesively retained composite resin core build-ups

OBJECTIVE

To determine the influence of the geometric dimensions of core build-ups on early core build-up failure, that is, loss before definitive prosthesis cementation.

MATERIALS AND METHODS

Adhesive core build-ups of exclusively vital teeth in 114 participants were evaluated (n materials: 40 Rebilda DC, 38 Multicore Flow, 36 Clearfil DC Core; n teeth: 8 incisors, 54 premolars, 52 molars). Impressions of the abutment teeth were made (1) after removal of insufficient restorations/caries and (2) after core build-up and preparation for a fixed prosthesis. Digitized model surfaces of both situations were aligned (Geomagic Design X) and core build-up volume (V_CBU ), remaining hard tissue volume (V_Abut ), and size of the adhesive surface (A_adh ) were assessed. The derived measure d_CBU  = V_CBU /A_adh can be interpreted as mean arithmetic core build-up thickness. Associations between participant or core build-up design characteristics and the occurrence of early failures were statistically evaluated (SPSS v27, α = 0.05).

RESULTS

A total of six (5.3%) core build-up failures were registered. Higher participant age, greater core build-up volume V_CBU and greater arithmetic uniform thickness d_CBU were associated with a greater incidence of failure in bivariate and univariate, however, not in multivariate statistics.

CONCLUSIONS

Core build-up volume and thickness were associated with early success or failure.

CLINICAL SIGNIFICANCE

In the case of voluminous/thick core build-ups in relation to the adhesive surface, additional measures, such as the preparation of retentive elements to increase the bonding area, might be considered to reduce the risk of early core build-up failure.

Early failures when using three different adhesively retained core build-up materials-a randomized controlled trial

Objectives

To compare the failure rates for three different adhesively retained core build-up composites up to the incorporation of a permanent fixed dental prosthesis (FDP), and to identify potential failure risk factors.

Material and methods

A randomized controlled trial of 300 participants in need of a core build-up to restore a vital abutment tooth before prosthetic treatment was conducted. Participants were assigned by stratified block randomization to one of three study groups: Rebilda DC (RDC), Clearfil DC Core (CDC), or Multicore Flow (MF). Test teeth were prepared by use of the respective manufacturer’s adhesive system. The total-etch technique was used for RDC and MF, and the self-etch technique for CDC. Participants were treated by dentists (n = 150) or dental students (n = 150). Failure rates of core build-ups before incorporation of FDPs were investigated using univariate and multiple logistic regression.

Results

The overall failure rate was 8% (n = 23). Rate differences between the three investigated groups did not reach statistical significance (p > 0.05). The mean time between placement of core build-ups and placement of fixed dental prostheses was 12.2 (SD: 14.2) weeks. Conversely, larger cavities (> 3 surfaces) and treatment by dental students were independently associated with an increased failure risk (p < 0.05).

Conclusions

The main risk factors for early failure seem to be the size of the core build-up and clinical experience of the operator, whereas failure rates of core build-up materials combined with a self-etch approach seem to be similar to the rates of materials combined with the total-etch technique.

Clinical significance

This research article should give clinicians an impression of the short-term performance of different adhesively retained core build-ups using different adhesive techniques/materials. Moreover, predominant influencing factors for the success or failure should be pictured.

Effect of different surface treatments of human occlusal sclerotic dentin on micro-tensile bond strength to resin composite core material

The objectives of this study were to evaluate the micro-tensile bond strength (μTBS) of composite bonded to human occlusal sclerotic dentin following different surface treatments to determine the sclerotic dentin morphology. Human molars without (normal dentin; group 1) or with occlusal wear (sclerotic dentin; groups 2-5) were divided and subjected to different surface treatments, including the normal protocol for the Contax self-etch bonding system (group 1 and 2); doubled etch-prime time (group 3); pre-conditioning with 37% phosphoric acid before normal protocol (group 4); or pre-conditioning with 37% phosphoric acid before doubling the self-etching time (group 5). All teeth were restored with composite (Luxacore Z dual), sectioned into stick specimens and stored for 24 h in water before specimens were subjected to the μTBS test (n = 50 per group). The μTBS of normal dentin was not statistically significantly different from that of the sclerotic dentin groups, except for the doubled etch-prime time group which showed lower μTBS. Sclerotic dentin pre-treated with phosphoric acid resulted in less sclerotic casts and wider dentinal tubules, while doubled etch-prime time did not alter the morphology, as shown by scanning electron microscopy. In conclusion, the use of 37% phosphoric acid before applying self-etch bonding resulted in more tubule openings and a significantly higher μTBS when compared with the doubled etch-prime time group.

Influence of a Retentive Shoulder Design to Prevent Early Failure of Three Core Build-Ups

This study evaluated the influence of a retentive shoulder design to prevent early failure of three resin composite build-ups on molars. Ninety-six intact extracted human maxillary third molars were assigned to two groups (n=48) based on occlusal, buccal cusps only and all cusps reduction. The groups were divided into two subgroups: pin retained and non-pin retained build-ups resulting in four groups (n=24), according the cusps reduction: pin retained/partial, pin retained/complete, non-pin retained/partial, non-pin retained/complete. Occlusal reduction was 3 mm with a semi-lunar retentive shoulder of 3 mm and an axial wall height of 1.5 mm. Groups were restored using a microhybrid, flowable or titanium reinforced resin composite. Modified self-curing acrylic resin provisional crowns were fabricated, cemented with non-eugenol temporary cement and thermal cycled. An instron machine applied tension to the provisional crowns parallel to the long axis of the tooth until dislodgement. A three-way analysis of variance was conducted on the influence of the variables on the retention of the core build-up. Ninety-three build-ups were retained under tensile load, while three core build-ups without pins were dislodged. Three-way analysis of variance showed no statistically significant difference between core build-ups using a retentive shoulder and pin retained core build-ups when tested under tensile load. With the advent of adhesive systems, increased surface area and retentive shoulder design can provide a retentive core foundation to prevent early failures of core build-ups during indirect restoration fabrication which will contribute to the longevity of final restorations.

Performance of Post-retained Single Crowns: A Systematic Review of Related Risk Factors

INTRODUCTION

Numerous factors may influence the survival/success of post-retained restorations of endodontically treated teeth (ETT). The aim of this review was to assess the influence of the number of remaining coronal walls, the use or disuse of posts, and their type on the clinical performance of these restorations.

METHODS

Randomized controlled trials and controlled clinical trials for ETT restored with a combination of post/crown or no post/crown were searched for in MEDLINE, Embase, and the Cochrane Library. Two authors independently reviewed all identified titles and abstracts for eligibility. Tables were generated to summarize the included studies, and reports of randomized trials were assessed for bias using the Cochrane risk of bias tool.

RESULTS

Nine articles were identified as meeting the inclusion criteria. Teeth without ferrule presented the highest values of variation of success/survival (0%-97%), whereas teeth with remaining coronal walls (1, 2, 3, or 4 walls with ferrule) presented lower variation. The use of posts with a high elastic modulus success/survival ranged between 71.8% and 100%, whereas posts with a low elastic modulus ranged between 28.5% and 100%. The survival of crowns without posts varied between 0% and 100%. The poor performance of posts with a low elastic modulus and without posts was associated with the absence of ferrule and the preservation of only 1 coronal wall.

CONCLUSIONS

The restoration of ETT should focus on the maintenance of the coronal structure. Until more studies with longer follow-up periods are available, posts with a high elastic modulus appear to present with better performance when restoring ETT with no ferrule.

In Vitro Assessment of Retention and Resistance Failure Loads of Teeth Restored with a Complete Coverage Restoration and Different Core Materials

PURPOSE

To investigate in vitro the retention and the resistance form, as well as the failure modes of maxillary premolars restored with cast metal crowns and different core materials.

MATERIALS AND METHODS

Sixty human extracted maxillary premolars were selected according to their size and were embedded in PMMA resin blocks. After removing a part of their clinical crowns, the teeth were randomly divided into 3 groups of 20 teeth and were either left unrestored, or they were restored with amalgam or composite resin. All teeth were prepared for a cast metal complete coverage restoration. The restorations were cemented on the prepared teeth with a resin-modified glass ionomer luting agent (GC Fuji Plus). All specimens were subjected to static loading at 1 mm/min by a universal testing machine, until failure. Half the specimens of each group were subjected to tensile loading along the long axis of the teeth. The other half were subjected to compressive loading at a 30° angle. Failure loads and failure modes for each tooth were recorded. The statistical analysis included descriptive statistics, one-way ANOVA, and Tukey's HSD test.

RESULTS

One-way ANOVA revealed statistically significant differences among the 3 tested groups (p < 0.05) for both tests. The group of teeth with no core material presented the highest failure loads for both the tensile and the compressive loading tests, with mean loads of 381.02 Ν and 741.21 Ν, respectively. Mean tensile and compressive failure loads for the amalgam group were 277.34 Ν and 584.75 Ν, while the composite resin group presented the lowest tensile and compressive failure values, which were 250.77 Ν and 465.78 Ν, respectively. The compression loading test resulted in the same failure mode for all specimens, which included unfavorable fracture of the teeth in combination with detachment of the cast metal complete coverage restorations. The tensile loading test resulted in different failure modes between the groups that used a core material and the group with no core material.

CONCLUSIONS

Teeth that lost more than half of their coronal structure presented better retention and resistance form if no core material was used, provided that a minimum of 2-mm axial wall height was present at the missing part. Teeth that have lost more than half of their coronal structure and were restored with amalgam core presented better retention and resistance form than those restored with composite resin. Catastrophic fractures, extending to the root, were associated with compression forces but not with tensile forces.

An assessment of fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in endodontically treated teeth: anin vitrostudy

Endodontically treated teeth with excessive loss of tooth structure would require to be restored with post and core to enhance the strength and durability of the tooth and to achieve retention for the restoration. The non-metallic posts have a superior aesthetic quality. Various core build-up materials can be used to build-up cores on the posts placed in endodontically treated teeth. These materials would show variation in their bonding with the non-metallic posts thus affecting the strength and resistance to fracture of the remaining tooth structure.

Aims. The aim of the study was to assess the fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in extracted endodontically treated teeth.

Material and Methods. Forty-five freshly extracted maxillary central incisors of approximately of the same size and shape were selected for the study. They were divided randomly into 3 groups of 15 each, depending on the types of non-metallic posts used. Each group was further divided into 3 groups (A, B and C) of 5 samples each depending on three core build-up material used. Student’s unpaired ‘t’ test was also used to analyse and compare each group with the other groups individually, and decide whether their comparisons were statistically significant.

Results. Luxacore showed the highest fracture resistance among the three core build-up materials with all the three posts systems. Ti-core had intermediate values of fracture resistance and Lumiglass had the least values of fracture resistance.

Fracture strength and nanoleakage of weakened roots reconstructed using relined glass fiber-reinforced dowels combined with a novel prefabricated core system

PURPOSE

The aim of this study was to evaluate fracture strength and nanoleakage of endodontically treated weakened teeth after being restored with relined glass fiber-reinforced dowels and two types of cores.

MATERIALS AND METHODS

Sixty sound human decoronated and endodontically treated teeth were embedded in epoxy resin blocks, then divided into three groups (n = 20) according to the method of root reconstruction. Group 1 (control): nonweakened roots were restored with glass fiber-reinforced dowels (UNIC); group 2: weakened roots restored with glass fiber-reinforced dowels relined with composite resin; group 3: weakened roots restored with glass fiber-reinforced dowels and a thick layer of luting cement. Dowels were cemented using Corposit, a dual-cured adhesive resin cement, then each group was assigned into two subgroups (n = 10) according to the type of core used; subgroup a: custom-made core using the same luting cement, subgroup b: prefabricated glass fiber-reinforced core (UNIC). Half the specimens of each subgroup were individually mounted at 45° angles and statically compressed until fracture at a 0.5 mm/min crosshead speed with a 5 kN load cell. The type of failure was assessed using a magnification lens. The other half of the specimens were removed from the block, placed in silver nitrate solution for 24 hours followed by photo developer for 8 hours, then examined using environmental scanning electron microscope/energy dispersive analytical X-ray for nanoleakage evaluation. Data were statistically analyzed.

RESULTS

The nonweakened group recorded the highest fracture strength values. The composite relined group showed significantly higher fracture strength values than the cement group. The prefabricated core yielded higher fracture strength values than the custom-made core. All groups showed a degree of nanoleakage, with higher scores recorded for the composite group.

CONCLUSIONS

The fracture resistance of wide root canals can be improved by using glass fiber-reinforced dowels relined with composite resin as an alternative to increasing the thickness of luting cement; however, the percentage nanoleakage would increase. On the other hand, the recently introduced prefabricated glass fiber-reinforced core can be considered a promising technique, but further investigations are necessary.

Comparative evaluation of compressive strength and flexural strength of conventional core materials with nanohybrid composite resin core material an in vitro study

Several dental materials have been used for core build-up procedures. Most of these materials were not specifically developed for this purpose, but as a consequence of their properties, have found application in core build-up procedures. Improvements in composites and the development of nanocomposites have led to their use as a core build up material due to their superior mechanical properties, optical properties and ease of handling. However it is not clear if they have better mechanical properties than the conventional core build up materials like amalgam, GIC and dual cure composite core build up material. The strength of the core material is very important and this study was undertaken to compare the mechanical properties of materials used for direct core foundations. The differences between the compressive strength and flexural strength of Filtek Z350 nanocomposite with conventional core build up materials like Amalgam, Vitremer GIC and Fluorocore were tested. Cylindrical plexi glass split molds of dimension 6 ± 1 mm [height] x4 ± 1 mm [diameter] were used to fabricate 15 samples of each core material for testing the compressive strength and rectangular plexi glass split molds of dimension 25 ± 1 mm [length] x 2 ± 1 mm[height] x2 ± 1 mm [width] used for fabricating samples for flexural strength. The samples were stored a water bath at 250 °C for 24 h before testing. The samples were tested using a Universal Instron testing machine. The results of the study showed that Fluorocore had the highest compressive strength and flexural strength followed by Filtek Z350 [nanocomposite] Amalgam had the least flexural strength and Vitremer GIC had the least compressive strength. Thus flurocore and nanocomposite are stronger than other core build up materials and hence should be preferred over other conventional core build up materials in extensively damaged teeth.

Effect of sodium hypochlorite contamination on microhardness of dental core build-up materials

This study aimed to determine the influence of sodium hypochlorite (NaOCl) contamination on the microhardness of build-up composites. Fifty-two samples, from each of three build-up materials (LuxaCore Dual, MultiCore flow and Rebilda DC) were prepared. Half of the samples from each material were stored in physiologic saline (baseline control) while the other halves were stored in NaOCl. After 1 h, the samples were rinsed with tap water, cut axially and measured for Knoop hardness at different depth levels. The results were analysed by ANOVA and unpaired t-tests (p<0.05). Significant differences in microhardness were observed for LuxaCore Dual up to 0.2 mm, Rebilda DC up to 0.3 mm, and for MultiCore flow up to 0.4 mm under the surface level. Contact with sodium hypochlorite on build-up materials causes reduction of the microhardness. The softening is not only limited on the surface, but can also be found in deeper layers of build-up materials.

Physical properties of self-, dual-, and light-cured direct core materials

The objective of this study is to evaluate flexural strength, flexural modulus, compressive strength, curing temperature, curing depth, volumetric shrinkage, water sorption, and hygroscopic expansion of two self-, three dual-, and three light-curing resin-based core materials. Flexural strength and water sorption were measured according to ISO 4049, flexural modulus, compressive strength, curing temperature, and curing depth according to well-proven, literature-known methods, and the volumetric behavior was determined by the Archimedes' principle. ANOVA was calculated to find differences between the materials' properties, and correlation of water sorption and hygroscopic expansion was analysed according to Pearson (p < 0.05). Clearfil Photo Core demonstrated the highest flexural strength (125 ± 12 MPa) and curing depth (15.2 ± 0.1 mm) and had the highest flexural modulus (≈12.6 ± 1.2 GPa) concertedly with Multicore HB. The best compressive strength was measured for Voco Rebilda SC and Clearfil DC Core Auto (≈260 ± 10 MPa). Encore SuperCure Contrast had the lowest water sorption (11.8 ± 3.3 µg mm(-3)) and hygroscopic expansion (0.0 ± 0.2 vol.%). Clearfil Photo Core and Encore SuperCure Contrast demonstrated the lowest shrinkage (≈2.1 ± 0.1 vol.%). Water sorption and hygroscopic expansion had a very strong positive correlation. The investigated core materials significantly differed in the tested properties. The performance of the materials depended on their formulation, as well as on the respective curing process.

Glass ionomer cements and their role in the restoration of non-carious cervical lesions

Glass ionomer based materials are clinically popular in several areas of restorative dentistry, but restoration of cervical lesions has proven particularly successful. Various etiologies, conformations, locations and structural characteristics make non-carious cervical lesions more challenging to adhesive restorative procedures and marginal seal in the long run. Due to their characteristics, glass ionomer cements (GICs) have precise indication for these cases. Moreover, the use of a GIC base underneath composite resin, the so-called "sandwich" or mixed technique, allows associating the good characteristics of composite resins and GICs, and has been considered quite useful in the restoration of non-carious cervical defects. The aim of this paper is to critically review the literature and discuss peculiar features of GICs regarding their role in the restoration of non-carious cervical lesions.

Bond strength performance of different resin composites used as core materials around fiber posts

OBJECTIVES

To evaluate the microtensile bond strengths of different resin composites used as core materials around fiber posts.

METHODS

Forty DT Light-Posts (RTD) were randomly divided into eight groups, according to the resin composite used. They included two core materials specifically developed for core build-up--Group 1: Core-Flo (Bisco Inc.) and Group 2: UniFil Core (GC Corp.); three hybrid composites--Group 3: Tetric Ceram (Ivoclar-Vivadent), Group 4: Gradia Direct (GC Corp.), Group 5: Bisfil 2B (Bisco, Inc.); and three flowable composites--Group 6: AEliteflo (Bisco, Inc.), Group 7: Filtek Flow (3M ESPE) and Group 8: UniFil Flow (GC Corp). A cylindrical plastic matrix was placed around the silanized post and filled with the respective resin composite. Each bonded post provided five to eight sticks for microtensile testing. Each stick was loaded to failure under tension at a cross-head speed of 0.5mm/min. One-way ANOVA and Tukey's test were used for statistical analysis. Scanning electron microscopy (SEM) was used to evaluate the interface of the fractured sticks.

RESULTS

Resin composites exhibited a significant influence on microtensile bond strength (p<0.05). Core-Flo showed the highest bond strength (11.00+/-0.69 MPa) although it was not statistically significantly different from all groups, except from the flowable composites. Under SEM, all the composites adapted well to the fiber post, with a variable extent of voids observed along the fractured composite interfaces.

SIGNIFICANCE

Although good adaptation to the post surface was achieved, bond strength to fiber post remains relatively weak. Core build-up and hybrid composites are better alternatives to flowable composites as core build-up materials.