Fracture Resistance of Pressed and Milled Lithium Disilicate Anterior Complete Coverage Restorations Following Endodontic Access Preparation.

PURPOSE: This in vitro study evaluated the fracture resistance and clinical prognosis of anterior lithium disilicate crowns (e.max Press and e.max CAD), following endodontic access and repair. The research design simulates intraoral loading conditions to produce clinically applicable results. MATERIALS AND METHODS: Monolithic anterior crowns, based on #8 anatomy, were fabricated from e.max Press ingots and e.max CAD blocks and adhesively bonded on identical dies milled out of a dentin analog material (NEMA G10). Specimens were divided into 4 groups: intact pressed, repaired pressed, intact milled, and repaired milled (n = 15/group). Repaired pressed and repaired milled were prepared with a standardized endodontic access and repaired using a porcelain repair system and composite resin. All crowns were cyclically loaded under simulated oral conditions and then loaded to failure in water, using a universal testing machine. Data were interpreted using ANOVA/Tukey post-hoc test (α = 0.05). RESULTS: Mean loads to failure ranged from 758.9 to 931.4 N for the 4 groups, indicating that both fabrication techniques, pressed and milled, yielded restorations that could reasonably withstand maximum masticatory forces. The pressed groups (923.7 N) exhibited significantly higher fracture resistance than the milled groups (797.5 N), p = 0.0002. When milled and pressed groups were categorized into intact and repaired subgroups, no difference was found in fracture resistance between the subgroups. Differences were noted in the modes of fracture, where the milled groups (intact and repaired) exhibited higher frequency of catastrophic fractures than the pressed groups. CONCLUSIONS: Endodontic access preparation does not appear to affect fracture resistance of an anterior lithium disilicate restoration, suggesting that replacement may not be necessary. Fabrication technique had a significant effect on fracture resistance and fracture mode of lithium disilicate restorations. The pressed fabrication technique resulted in significantly greater crown strength and fracture resistance than the milled technique.

An accessory technique for the intraoral removal of a fractured implant abutment screw.

As the use of dental implants becomes more prevalent, mechanical complications become more common. When an implant abutment screw fractures, it can be difficult to retrieve the retained fragment. The purpose of this article is to describe a technique to remove the abutment screw fragments without damaging the implant body or its screw threads.

Repair Success of Two Innovative Hybrid Materials as a Function of Different Surface Treatments.

PURPOSE: To evaluate surface treatments for chipping in order to avoid bonding problems between hybrid materials and composite resin and to determine the optimal surface treatment method during intraoral repair of restorations to achieve clinical success. MATERIALS AND METHODS: A total of 96 samples were prepared from computer-aided design/computer-assisted manufactured (CAD/CAM) blocks: 48 polymer-infiltrated ceramic (PIC) and 48 resin nano-ceramic (RNC). Prior to application of the surface treatments, the two test groups were each divided into four subgroups: control group; hydrofluoric acid group; hydrofluoric acid with silane group; and air-abraded with silica-coated aluminum oxide (Al2O3) sand with silane group. Each subgroup contained 12 samples. A shear bond strength (SBS) test was performed after artificial aging (5,000 cycles, 5°C to 55°C). RESULTS: For both types of ceramic used, all subgroups showed significantly higher SBS values than the control groups (P < .05). The highest SBS values for both types of ceramic were observed in the air-abraded with silica-coated Al2O3 particles group. CONCLUSION: Each of the surface treatment methods increased the SBS, with the most effective method being air abrasion with silica-coated Al2O3.

Management of a Damaged Implant for Retention of an Overdenture Prosthesis and Fixed Single Crown: Clinical Reports.

This article demonstrates a method to salvage an implant that has been damaged or is no longer usable because of a fractured screw that cannot be removed. In the first situation the patient had a Locator abutment that fractured during torqueing of the abutment. Despite the attempt to remove the fractured screw, it was not retrievable, and the internal threads of the implant were damaged in the attempt to remove the screw. Rather than removing the implant or covering it and sleeping the implant, a custom cast post was used to restore the implant to function. A second example describes a patient with a fixed implant crown. The implant was damaged during attempts to remove the fractured screw. A custom post was fabricated and cemented, and a new crown was fabricated.

Effect of surface treatments on repair with composite resin of a partially monoclinic phase transformed yttrium-stabilized tetragonal zirconia.

STATEMENT OF PROBLEM: Studies of composite resin repairs of yttrium-tetragonal zirconia polycrystal (Y-TZP) are usually performed in its tetragonal phase, but it may be partially transformed into a monoclinic phase in a clinical fracture. PURPOSE: The purpose of this in vitro study was to evaluate the effect of airborne-particle abrasion (APA) and a bonding agent on the shear bond strength (SBS) between a composite resin and hydrothermally aged Y-TZP. MATERIAL AND METHODS: Specimens (7.0×7.0×1.7 mm, N=112) of Y-TZP Lava were obtained, and 50% were aged in an autoclave at 134°C at 300 kPa for 8 hours. The surfaces were treated with APA 50-µm Al2O3 particles (ALU) or Rocatec Soft (30 µm) (ROC) followed by Clearfil SE Bond Primer (10-methacryloyloxydecyl dihydrogen phosphate [10-MDP]) plus Clearfil porcelain bond activator (3-methacryloxypropyl-trimethoxy silane [3-MPS]) (CLE) or RelyX Ceramic Primer plus a layer of RelyX U100 adhesive-resin cement (REL). Composite resin cylinders were built on the Y-TZP treated surfaces. After thermocycling (6000 cycles, 5°C and 55°C, 30-second dwell time), an SBS test was carried out (n=14). Data were analyzed by 3-way ANOVA and the Tukey honest significant differences test (α=.05). The failure mode was analyzed. RESULTS: The 3-way ANOVA was not significant for aging (P>.05), but the APA (P<.001), bonding agent (P<.001), and their interaction (P<.001) were significant. APA with ALU or ROC did not influence the SBS of the groups bonded with CLE, but the REL APA with ROC provided higher SBS. The failure mode was adhesive for all specimens. CONCLUSIONS: Adhesion was not different on monoclinic partially transformed Y-TZP. The APA with ROC followed by REL was the most effective treatment for repairing Y-TZP.

Marginal discrepancy of noble metal-ceramic fixed dental prosthesis frameworks fabricated by conventional and digital technologies.

STATEMENT OF PROBLEM: Studies evaluating the marginal adaptation of available computer-aided design and computer-aided manufacturing (CAD-CAM) noble alloys for metal-ceramic prostheses are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the vertical marginal adaptation of cast, milled, and direct metal laser sintered (DMLS) noble metal-ceramic 3-unit fixed partial denture (FDP) frameworks before and after fit adjustments. MATERIAL AND METHODS: Two typodont teeth were prepared for metal-ceramic FDP abutments. An acrylic resin pattern of the prepared teeth was fabricated and cast in nickel-chromium (Ni-Cr) alloy. Each specimen group (cast, milled, DMLS) was composed of 12 casts made from 12 impressions (n=12). A single design for the FDP substructure was created on a laboratory scanner and used for designing the specimens in the 3 groups. Each specimen was fitted to its corresponding cast by using up to 5 adjustment cycles, and marginal discrepancies were measured on the master Ni-Cr model before and after laboratory fit adjustments. RESULTS: The milled and DMLS groups had smaller marginal discrepancy measurements than those of the cast group (P<.001). Significant differences were found in the number of adjustments among the groups, with the milled group requiring the minimum number of adjustments, followed by the DMLS and cast groups (F=30.643, P<.001). CONCLUSIONS: Metal-ceramic noble alloy frameworks fabricated by using a CAD-CAM workflow had significantly smaller marginal discrepancies compared with those with a traditional cast workflow, with the milled group demonstrating the best marginal fit among the 3 test groups. Manual refining significantly enhanced the marginal fit of all groups. All 3 groups demonstrated marginal discrepancies within the range of clinical acceptability.

Clinical assessment of fractured implant abutment screws: The Bernese silicone replica technique.

Fractured implant abutment screws can be retrieved with repair or rescue devices. However, whether the screw was completely retrieved or the inner implant body was damaged may be uncertain. A silicone replica technique was recently implemented in Bern and may be the most predictable method available at the moment for clinically assessing the internal implant body. This technique is straightforward and precise and may help dentists determine the internal implant condition when managing a fractured screw.

Effect of several repair techniques on the bond strength between composite resin and degraded Y-TZP ceramic / Efeito de várias técnicas de reparo na resistência de união entre resina composta e zircônia degradada

Objective: To evaluate the bond strength of different repair treatments for composite resin to aged Y-TZP ceramics. Material and Methods: Zirconia blocks were cut into smaller specimens, sintered according to manufacturer's recommendations (final dimensions of 4×4×3 mm), and randomly allocated into nine groups (n=15) according to the surface treatment and presence/ absence of aging of the substrate (subjected to lowtemperature degradation - LTD), as follows: without LTD (Control: without treatment; TBS: tribochemical silica coating + silane + adhesive); with LTD (Control-LTD: without treatment; TBS-LTD: TBS with hydrothermal degradation; MoS-LTD: Monobond S + adhesive; MoPLTD: Monobond Plus + adhesive; MZP-LTD: Metal/ Zirconia Primer + adhesive; USB-LTD: Single Bond Universal; AP-LTD: Alloy primer + adhesive). LTD was simulated in an autoclave (134 °C, 2 bar, 5 h). The ceramic blocks were embedded in PVC cylinders with a self-curing acrylic resin; each surface treatment protocol was performed; a composite resin cylinder ( : 3.25 mm and height: 3 mm) was then build-up using split metallic matrices. All the specimens were aged (thermocycling + storage in water for 90 days) and subjected to the shear bond strength test using a universal testing machine (1 mm/min). The failure mode was classified into four types: adhesive, composite resin cohesive fracture, ceramic cohesive fracture, and mixed. The bond strength values were subjected to Mann­Whitney test. Results: Only air-abraded samples (TBS and TBS­LTD) survived thermocycling. More than 80% of the samples of the other groups presented pre-test failures. TBS groups presented higher values of bond strength (3.94) compared to TBSLTD (0.96). The predominant type of failure for the surviving samples were adhesive. Conclusion: Air particle abrasion is mandatory to improve the bond strength of the Y-TZP substrate; an aged substrate presents an even more unfavorable scenario for adhesion. (AU)

Objetivo: Avaliar a resistência de união ao cisalhamento gerada por diferentes técnicas de reparo em resina composta aderida em zircônia envelhecida (sujeita a degradação a baixa temperatura - LTD). Material e Métodos: blocos de zircônia foram seccionados em espécimes, sinterizados de acordo com o fabricante (dimensões finais de 4x4x3 mm), e aleatorizados em nove grupos (n=15) de acordo com o tratamento de superfície e presença/ausência de envelhecimento do substrato (LTD), conforme: sem LTD (Control: sem tratamento; TBS: tribosilicatização + silano + adesivo); com LTD (Control-LTD: Monobond S + adesivo; MoP-LTD: Monobond plus + adesivo; MZPLTD: Meta/Zirconia primer + adesivo). LTD foi simulada em autoclave (134 °C, 2 bar, 5 h). Os blocos de cerâmica foram embutidos em cilindros de PVC com resina acrílica autopolimerizável; cada tratamento de superfície foi realizado; um cilindro de resina composta ( : 3,25 mm 3 mm de altura) foi confeccionado usando matrizes metálicas bipartidas. Todos os espécimes foram envelhecidos (termociclagem + armazenagem em água por 90 dias) e sujeitos ao teste de cisalhamento usando um equipamento de teste universal (1 mm/ min). O modo de falha foi classificado em quatro grupos: adesivo, fratura coesiva em resina composta, fratura coesiva da cerâmica, e mista. Os valores de adesão foram sujeitos ao teste de Mann-Whitney. Resultados: somente as amostras jateadas (TBS e TBSLTD) sobreviveram a termociclagem. Mais que 80% dos espécimes dos outros grupos apresentaram falhas préteste. Os grupos TBS apresentaram os maiores valores de resistência ao cisalhamento (3,94) comparado com TBS-LTD (0,96). Os tipos predominantes de falha para os espécimes sobreviventes foi adesiva. Conclusão: o jateamento é recomendável para aumentar a resistência adesiva à zircônia; um substrato envelhecido apresenta um cenário mais desfavorável de adesão. (AU)

In Vitro Comparison of the Bond Strength between Ceramic Repair Systems and Ceramic Materials and Evaluation of the Wettability.

PURPOSE: When fracture of an all-ceramic restoration occurs, it can be necessary to repair without removing the restoration. Although there are many studies about the repair of metal-ceramic restorations, there are few about all-ceramic restorations. The aim of this study was to evaluate the shear bond strength between ceramic repair systems and esthetic core materials and to evaluate the wettability of all-ceramic core materials. MATERIALS AND METHODS: Disk-like specimens (N = 90) made of three dental ceramic infrastructure materials (zirconia ceramic, alumina ceramic, glass ceramic) were polished with silicon carbide paper, prepared for bonding (abrasion with 30 µm diamond rotary cutting instrument). Thirty specimens of each infrastructure were obtained. Each infrastructure group was divided into three subgroups; they were bonded using 3 repair systems: Bisco Intraoral Repair Kit, Cimara & Cimara Zircon Repair System, and Clearfil Repair System. After 1200 thermocycles, shear bond strength was measured in a universal testing machine at a 0.5 mm/min crosshead speed. In addition, the contact angle values of the infrastructures after surface treatments were examined for wettability. Data were analyzed by using ANOVA and Tukey post hoc tests. RESULTS: Although there were no significant differences among the repair systems (p > 0.05) in the glass ceramic and zirconia groups, a significant difference was found among the repair systems in alumina infrastructure (p < 0.001). There were no statistically significant differences among the infrastructures (p > 0.05); however, a statistically significant difference was found among the repair systems (p < 0.05). No difference was found among the infrastructures and repair systems in terms of contact angle values. CONCLUSIONS: Cimara & Cimara Zircon Repair System had higher bond strength values than the other repair systems. Although no difference was found among the infrastructures and repair systems, contact wettability angle was decreased by surface treatments compared with polished surfaces.

Mantenimiento, manejo y cuidado de las prótesis dentales en pacientes atendidos en una consulta de estomatología general integra / Preservation, handling and care of the dental prosthesis in patients assisted in a comprehensive general stomatology service

Se realizó un estudio descriptivo y transversal de los 110 pacientes portadores de prótesis dentales, atendidos en la consulta de Estomatología General Integral de la Clínica Estomatológica Provincial Docente "Mártires del Moncada" de Santiago de Cuba, en el período de septiembre a diciembre del 2015, con el propósito de identificar el mantenimiento, los cuidados y manejos en los aparatos protésicos. Se obtuvo un predominio de los pacientes que portaban prótesis total superior (50,0 %), de los que las habían usado por más de 5 años (52,7 %) y de las prótesis en mal estado (58,2 %); la higiene bucal deficiente resultó más frecuente en el sexo masculino (67,7 %) al aplicar el índice de Love.

A descriptive and cross-sectional study of the 110 patients with dental prosthesis assisted in the General comprehensive stomatology service of "Mártires del Moncada" Teaching Provincial Stomatological Clinic in Santiago de Cuba, was carried out from September to December, 2015, aimed at identifying the preservation, caring and handling in the prosthetic appliances. There was a prevalence of the patients that carried upper total prosthesis (50.0%), of those that had used them for more than 5 years (52.7%) and of the prosthesis in poor conditions (58.2%); poor oral hygiene was more frequent in the male sex (67.7%) when implementing the Love index.

Survival of cast-metal, resin-bonded fixed partial dental prostheses after nearly 20-year follow-up: A retrospective study.

STATEMENT OF PROBLEM: Cast-metal resin-bonded fixed partial dental prostheses (RBFPDPs) are a conservative approach to replacing missing teeth. Despite their recognized advantages, the use of cast-metal RBFPDPs as a definitive option remains somewhat controversial because of the lack of long-term studies on their success. PURPOSE: The purpose of this retrospective study was to evaluate the long-term survival rate of cast-metal RBFPDPs and investigate the influence of covariates such as sex, type of prosthesis, location, number of pontics, abutments, and type of luting cement on the survival of bonded prostheses. MATERIAL AND METHODS: This study evaluated 209 cast-metal RBFPDPs cemented in 181 patients (mean 41.06 ±11.90 years of age) treated in the principal author's private practice between July 1993 and May 2012. Data sheets were completed at the patients' recall examination at regular intervals or if seen for complications. Kaplan-Meier analysis was used to evaluate the survival rate of the prostheses before debonding. The Cox model and Wald test were used to analyze the prognostic factors (α=.05). RESULTS: A total of 198 prostheses were studied. Eleven cast-metal RBFPDPs were lost to follow-up. This study evaluated the effect of different variables on the survival rate of both conventional RBFPDPs (wing-wing) and combination resin-bonded FPDPs (wing-crown) types. Survival rate was divided into "with repair" and "without repair" groups. The mean survival time was 102.24 months for the group with no repair and 119.76 months for the group with repair. The survival rate after 5, 10, and 15 years was 86%, 42%, and 15% with repair, whereas 69%, 32%, and 14% of the prostheses survived without repair. CONCLUSIONS: In appropriate clinical conditions and selected patients, cast-metal RBFPDPs were a viable treatment option with an acceptable survival rate.

Ceramic Repair Without Hydrofluoric Acid.

PURPOSE: To evaluate the bond strength between composite resin and feldspathic ceramic following repair protocols with and without hydrofluoric acid and aging by thermocycling. MATERIALS AND METHODS: Forty-eight glass feldspathic ceramic blocks (8 x 8 x 6 mm) were divided into three groups on the basis of their surface repair treatment: 1. 10% hydrofluoric acid + Signum Ceramic Primer I + Signum Ceramic Primer II (control group); 2. abrasive rubber tips + Signum Ceramic Primer I + Signum Ceramic Primer II (test group); 3. Signum Ceramic Primer I + Signum Ceramic Primer II (negative control group). The treated surface of each block was built up with composite and then sectioned to produce nontrimmed bars (adhesive area = 1 mm²). Half of the bars from each group were aged by 6000 cycles of 30-s immersions in water baths at 5°C and 55°C, with a transfer time of 2 s. The other bars were immediately subjected to microtensile bond strength testing. The mean bond strength for each block was then recorded and submitted to two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The aging protocol influenced the bond strength values of all groups (p = 0.000). The non-aged groups submitted to surface treatment protocols 1 (13.1 ± 2.5 MPa) and 2 (11.5 ± 5.1 MPa) presented the highest bond strength values. CONCLUSIONS: The interface bond strength of all groups was susceptible to aging. Surface treatment protocol 2, with abrasive rubber tips and no hydrofluoric acid, appeared to be the most promising option, as the resulting bond strength values were similar to those of the control group.

A minimally invasive approach for a compromised treatment plan.

A primary goal in dentistry is the execution of appropriate treatment plans that are minimally invasive and maintainable. However, it is sometimes necessary to repair existing dental restorations or revise treatment plans to accommodate changes in a patient's condition. In the present case, a patient who was satisfied with a removable partial overdenture lost a critical abutment tooth. A creative, minimally invasive approach enabled the patient to keep his existing partial prosthesis and avoid the need for a full reconstruction or complete denture.

Prospective assessment of CAD/CAM zirconia abutment and lithium disilicate crown restorations: 2.4 year results.

STATEMENT OF PROBLEM: Single-tooth implant restorations are commonly used to replace anterior maxillary teeth. The esthetic, functional, and biologic outcomes are, in part, a function of the abutment and crown. PURPOSE: The purpose of this clinical study was to describe the implant, abutment, and crown survival and complication rates for CAD/CAM zirconia abutment and lithium disilicate crown restorations for single-tooth implants. MATERIAL AND METHODS: As part of a broader prospective investigation that enrolled and treated 141 participants comparing tissue responses at the conical interface (CI; AstraTech OsseoSpeed), flat-to-flat interface (FI; NobelSpeedy), and platform-switch interface (PS; NanoTite Certain Prevail) of single-tooth implants, computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia abutments (ATLANTIS Abutment) and cemented lithium disilicate (e.max) crowns were used in the restoration of all implants. After 2.4 years in function (3 years after implant placement), the implant, abutment, and crown of 110 participants were evaluated. Technical and biologic complications were recorded. Demographic results were tabulated as percentages with mean values and standard deviations. Abutment survival was calculated with the Kaplan-Meier method. RESULTS: After 2.4 years, no abutments or crowns had been lost. Abutment complications (screw loosening, screw fracture, fracture) were absent for all 3 implant groups. Crown complications were limited to 2 crowns debonding and 1 with excess cement (2.5%). Five biological complications (4.0%) were recorded. The overall complication rate was 6.5%. CONCLUSIONS: CAD/CAM zirconia abutments restored with cemented lithium disilicate crowns demonstrated high survival on 3 different implant-abutment interface designs. No abutment or abutment screw fracture occurred. The technical complications observed after 2.4 years were minor and reversible. The use of CAD/CAM zirconia abutments with cemented lithium disilicate crowns is associated with high technical and biologic success at 2.4 years.

Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

PURPOSE: Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. MATERIALS AND METHODS: In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. RESULTS: Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. CONCLUSIONS: Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

Fracture resistance of lithium disilicate restorations after endodontic access preparation: An in vitro study.

STATEMENT OF PROBLEM: Endodontic access preparation through a lithium disilicate restoration is a frequently encountered clinical situation. The common practice of repairing the accessed crown with composite resin may result in a weakened restoration. PURPOSE: The purpose of this in vitro study was to determine the effect of endodontic access preparation on the fracture resistance and microstructural integrity of monolithic pressed and monolithic milled lithium disilicate complete coverage restorations. MATERIAL AND METHODS: Twenty monolithic pressed (IPS e.max Press) and 20 monolithic milled (IPS e.max CAD) lithium disilicate restorations were fabricated. Ten of the pressed and 10 of the milled crowns were accessed for a simulated endodontic treatment and subsequently repaired by using a porcelain repair system and composite resin. All specimens were submitted to cyclic loading and then loaded to failure. Force data were recorded and analyzed with 2-way ANOVA followed by a post hoc test (Sidak correction) to indicate significant differences among the groups (α=.05). A Weibull analysis was also performed for each group. Eight (4 pressed and 4 milled) additional restorations were fabricated to complete a scanning electron microscope (SEM) analysis and evaluate the surface damage created by the endodontic access preparation. RESULTS: A statistically significant difference (P=.019) was found between the pressed intact and pressed repaired restorations and between the pressed intact and milled repaired restorations (P=.002). Specimens that were examined with an SEM showed edge chipping involving primarily the glaze layer around the access openings. CONCLUSIONS: Endodontic access preparation of lithium disilicate restorations resulted in a significantly reduced load to failure in the pressed specimens, but not in the milled specimens.