An Invitro Analysis of Elemental Release and Cytotoxicity of Recast Nickel–Chromium Dental Casting Alloys

Recasting of the casting alloys affects the composition and elemental release which may have cytotoxic effect different from the pure alloy in the surrounding tissues. An Invitro study was conducted to investigate the elemental release and their cytotoxic effects from commercially available Ni–Cr dental casting alloys, commonly used for fabricating fixed partial dentures. Three Ni–Cr alloys [Wiron 99(A), Ceramet (B), and Hi Nickel CB (C)] were tested. Alloy specimens (disks 3 × 5 mm) were casted and grouped as follows: Group I (A₁/B₁/C₁): 100% pure alloy; Group II (A₂/B₂/C₂): 50% new with 50% recast; and Group III (A₃/B₃/C₃): 100% recast. Disks of each alloy type from each group were transferred to Dulbecco’s modified eagle medium and left for 3 days at 37°C in an atmosphere of 5% CO₂. Ni, Cr, Co, Cu and Mo elemental release from metal alloys into culture medium was investigated using Inductively Coupled Plasma Mass Spectrometry. Cytotoxicity was tested using mouse fibroblast cells and MTT Assay. Controls consisted of 6 wells containing cells with no alloy specimens. Data were analyzed by two-way analysis of variance followed by t-test. The total amount of elements released in parts per billion for various casting groups were Group I, A₁-6.572, B₁-6.732, C₁-8.407; Group II, A₂-22.046, B₂-26.450, C₂-29.189; Group III, A₃-84.554, B₃-88.359, C₃-92.264. More amounts of elements were released in Hi Nickel CB than Ceramet and Wiron 99 in all the three test groups. Percentage of viable cells from MTT analysis were Group I, A₁-62.342, B₁-61.322 C₁-60.593, Group II, A₂-58.699, B₂-56.494, C₂-52.688, Group III, A₃-53.101, B₃-52.195, C₃-47.586. The viable cells present in the culture media were more in Wiron 99 than Ceramet and Hi Nickel CB. Elemental release increased with amount of recast alloy. Amongst the three alloys tested Hi Nickel CB had significantly higher elements released compared to Ceramet and Wiron 99 in 100% pure alloys, 50% recast and 100% recast alloys. Wiron 99 showed least element release in 100% pure alloy, 50% recast and 100% recast specimens. 100% pure alloys of all three alloys are less cytotoxic, but their cytotoxicity is more on 50% and 100% re-casted alloys. Out of all three variations of casting Wiron 99 was least cytotoxic, followed by Ceramet and Hi Nickel CB. Recasting of alloys significantly increased the elements released and their cytotoxicity.     

The Effect of Surface Treatments on the Bond Strength of a Nonprecious Alloy–Ceramic Interface: An Invitro Study

The purpose of this study was to compare the effect of seven different alloy surface treatments on the bond strength of the porcelain-metal interface. Three layers of opaque porcelain and a measured thickness of dentin porcelain were applied to nickel–chromium alloy, A tensile bond strength test was used. The alloy surface treatment that exhibited the highest bond strength was sandblast + surface grinding + sandblast + de-gas, whereas the alloy surface treatment that exhibited the lowest bond strength was sandblast + surface grinding + sandblast + steam cleaning + de-gas. There was a significant difference between the two methods (P < 0.05). It was concluded that de-gassing the alloy prior to porcelain application increased the bond strength and excess surface grinding of the alloy reduced bond strength; steam cleaning the alloy surface prior to de-gassing and porcelain application also significantly reduced the bond strength.     

Evaluation and Comparison of the Effect of Different Surface Preparations on Bond Strength of Glass Ionomer Cement with Nickel–Chrome Metal–Ceramic Alloy: A Laboratory Study

Retention of fixed partial dentures is mostly dependent upon the bond between metal and cement as well as cement and tooth structure. However, most of the time clinical failure of bond has been observed at metal and cement interface. The treatment of metal surface, prior to luting, plays a crucial role in bonding cement with the metal. This study is conducted to evaluate and compare the effect of different surface preparations on the bond strength of resin-modified glass ionomer cement with nickel-chromium metal ceramic alloy. Fifty caries-free extracted molar teeth were made flat until the dentin of the occlusal surface was exposed. After fabrication of the wax patterns and subsequent castings, the castings were subjected to porcelain firing cycles. The nickel-chromium metal ceramic alloy discs were also divided into five groups and subjected to various surface treatments: (1) Unsandblasted (U), (2) sandblasted (S), (3) sandblasted and treated with 10% aqueous solution of KMnO4 (SK), (4) unsandblasted and roughened with diamond abrasive points (UD) and (5) unsandblasted and roughened with diamond abrasive points and treated with 10% aqueous solution of KMnO(4) (UDK). After surface treatments, the castings were cemented using Fuji PLUS encapsulated resin-modified glass ionomer cement. The obtained values of all the groups were subjected to statistical analysis for Tensile and Shear bond strength. Different surface treatments of the metal affects the bond strength values of resin-modified glass ionomer cement when used as luting agent.     

Comparative Evaluation of Marginal and Internal Gap of Co–Cr Copings Fabricated from Conventional Wax Pattern, 3D Printed Resin Pattern and DMLS Tech: An In Vitro Study

Accuracy of the fit of the restoration has always remained as one of the primary factors in determining success of the restoration. A well fitting restoration needs to be accurate both along its margins and internal surface. This study was conducted to comparatively evaluate the marginal gap and internal gap of cobalt–chromium (Co–Cr) copings fabricated by conventional casting procedures and with direct metal laser sintering (DMLS) technique. Among the total of 30 test samples 10 cast copings were made from inlay casting wax and 10 from 3D printed resin pattern. 10 copings were obtained from DMLS technique. All the 30 test samples were then cemented sequentially on stainless steel model using pressure indicating paste and evaluated for vertical marginal gap in 8 predetermined reference areas. All copings were then removed and partially sectioned and cemented sequentially on same master model for evaluation of internal gap at 4 predetermined reference areas. Both marginal gap and internal gap were measured in microns using video measuring system (VMS2010F). The results obtained for both marginal and internal gap were statistically analyzed and the values fall within the clinically acceptable range. The DMLS technique had an edge over the other two techniques used, as it exhibited minimal gap in the marginal region which is an area of chief concern.     

Shaping Ability of the Conventional Nickel-Titanium and Reciprocating Nickel-Titanium File Systems: A Comparative Study Using Micro–Computed Tomography

Introduction

This study used micro–computed tomographic imaging to compare the shaping ability of Mtwo (VDW, Munich, Germany), a conventional nickel-titanium file system, and Reciproc (VDW), a reciprocating file system morphologically similar to Mtwo.

Methods

Root canal shaping was performed on the mesiobuccal and distobuccal canals of extracted maxillary molars. In the RR group (n = 15), Reciproc was used in a reciprocating motion (150° counterclockwise/30° clockwise, 300 rpm); in the MR group, Mtwo was used in a reciprocating motion (150° clockwise/30° counterclockwise, 300 rpm); and in the MC group, Mtwo was used in a continuous rotating motion (300 rpm). Micro–computed tomographic images taken before and after canal shaping were used to analyze canal volume change and the degree of transportation at the cervical, middle, and apical levels. The time required for canal shaping was recorded. Afterward, each file was analyzed using scanning electron microscopy.

Results

No statistically significant differences were found among the 3 groups in the time for canal shaping or canal volume change (P > .05). Transportation values of the RR and MR groups were not significantly different at any level. However, the transportation value of the MC group was significantly higher than both the RR and MR groups at the cervical and apical levels (P < .05). In the scanning electron microscopic analysis, file deformation was observed for 1 file in group RR (1/15), 3 files in group MR (3/15), and 5 files in group MC (5/15).

Conclusions

In terms of shaping ability, Mtwo used in a reciprocating motion was not significantly different from the Reciproc system.     

Effects of Conventional Welding and Laser Welding on the Tensile Strength, Ultimate Tensile Strength and Surface Characteristics of Two Cobalt–Chromium Alloys: A Comparative Study

The purpose of this study was to evaluate the efficacy of laser welding and conventional welding on the tensile strength and ultimate tensile strength of the cobalt–chromium alloy. Samples were prepared with two commercially available cobalt–chromium alloys (Wironium plus and Diadur alloy). The samples were sectioned and the broken fragments were joined using Conventional and Laser welding techniques. The welded joints were subjected to tensile and ultimate tensile strength testing; and scanning electron microscope to evaluate the surface characteristics at the welded site. Both on laser welding as well as on conventional welding technique, Diadur alloy samples showed lesser values when tested for tensile and ultimate tensile strength when compared to Wironium alloy samples. Under the scanning electron microscope, the laser welded joints show uniform welding and continuous molt pool all over the surface with less porosity than the conventionally welded joints. Laser welding is an advantageous method of connecting or repairing cast metal prosthetic frameworks.     

TRUShape Versus XP-endo Shaper: A Micro–computed Tomographic Assessment and Comparative Study of the Shaping Ability—An In Vitro Study

IntroductionThe aim of this study was to evaluate and compare the shaping ability of XP-endo Shaper (XP; FKG Dentaire, La Chaux-de-Fonds, Switzerland) and TRUShape (TS; Dentsply/Tulsa Dental Specialties, Tulsa, OK) during the preparation of moderated curved root canals using micro–computed tomographic imaging.MethodsTwenty human maxillary premolars with 2 roots were randomly separated into 2 groups of 10 teeth, which were scanned before and after root canal preparation using the SkyScan 1275 X-ray microtomograph (Bruker micro-CT, Kontich, Belgium) at a nominal resolution of <4 μm. Premolars and irrigant were maintained at 37° before and during preparation; group 1 was treated using XP and group 2 with TS. After preparation, researchers measured the amount of dentin removed, untreated superficies of canal walls, root canal volume, degree of canal transportation, and centering ability. Values of central tendency and dispersion were calculated using Statgraphics Centurion XV software (StatPoint Technologies, Inc, Warrenton, VA); means and median were compared using the Mann-Whitney-Wilcoxon test. The level of significance was set at 5% (P < .05).ResultsNo significant statistical differences were observed between the 2 groups in shaping ability, untreated superficies of canal walls, degree of canal transportation, and centering ability (P > .05).ConclusionsInstrumentation of moderately curved root canals using the XP single file and the TS file system were equally effective. XP and TS maintained the original anatomy of the root canals and showed a similar percentage of untreated canal walls, centered ability, and minimal apical transportation.     

Micro–computed Tomographic Assessment and Comparative Study of the Shaping Ability of 6 Nickel-Titanium Files: An In Vitro Study

IntroductionThis research studies and compares the shaping ability of WaveOne Gold (WG; Dentsply Tulsa Dental Specialties, Tulsa, OK), the Reciproc Blue (RB; VDW, Munich, Germany), TRUShape (TS, Dentsply Tulsa Dental Specialties), XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland), iRace (IR, FKG), and TruNatomy (TN; Dentsply Sirona, Ballaigues, Switzerland) in the preparation of moderately curved canals and using micro–computed tomographic technology.MethodsSixty lower molars with 2 mesial canals were randomly distributed into 6 groups of 10 molars and 20 canals per group (n = 20). Specimens were scanned before and after preparation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WG, group 2 with RB, group 3 with TS, group 4 with XP, group 5 with IR, and group 6 with TN. After instrumentation, researchers quantified the changes produced in the canal geometry in terms of surface, volume, structure thickness, surface convexity index, structure model index, percentage of surface touched, and centroids. Wilcoxon and analysis of variance tests were performed to compare the values before and after preparation and the differences between groups. The significance level was established at 5%.ResultsThere were no significant differences between WG and RB (P > .05) and between TN and XP (P > .05). TN had significant differences with WG, RB, TS, and IR (P < .05). All the files produced similar apical transportation (P > .05).ConclusionsWG and RB and TN and XP had similar shaping effectivity. TS and WG touched the highest percentages of canal surfaces (81% and 73%, respectively) but produced the biggest changes in the canal anatomy. TN and XP better kept the canal anatomy, but TN touched the lowest percentage of canal surface (50%). All the files used were able to clean and to shape moderately curved canals with minimal apical transportation.     

Comparison of the Effect of Different Ceramic Alloys and Porcelain Systems upon the Color of Metal–Ceramic Restorations: An In Vitro Study

The exact replication of natural tooth color in a metal ceramic restoration is a challenging fact as its affected by enumerable factors. Research revealing the influence of base metal alloys with different porcelain systems on the color of the restorations have shown minimal interest. The aim of the study was to evaluate the optical influence of different alloys (mainly base metal) and ceramic systems affecting the final color of metal–ceramic restorations. Four commercial ceramic alloys, two Ni–Cr, one Co–Cr and a high-noble alloy were combined with two porcelains in metal–ceramic specimens with a standardized thickness of layers. Ten disc-shaped specimens were prepared for each alloy/porcelain combination. High-noble was used as control group. Only opaque and dentin layers were applied. The specimens were analysed with Spectrophotometer, and data were obtained in the CIELAB color system. The recorded data were analysed with a one-way ANOVA and multiple range test by tukey—HSD procedure to identify the significant groups at 5 % level. The final color of the metal–ceramic specimens were significantly affected by both type of the alloy and the porcelain systems used (P < 0.0001). The Co-Cr alloy-porcelain combination produced least color difference when compared with the high-noble control group. There was significant difference (P < 0.0001) between both the brands of Ni–Cr alloy–porcelain systems. For all the alloy-porcelain combinations VMK 95 porcelain showed minimum color difference compared to the d-SIGN porcelain group. Conclusion: The final color of metal ceramic specimens was influenced both from the type of base metal alloy substructure and from the type of overlying porcelain.     

A Comparative Evaluation of the Effect of the Addition of Pachymic Acid on the Cytotoxicity of 4 Different Root Canal Sealers—An In Vitro Study

Introduction

Root canal sealers exhibit varying degrees of cytotoxicity to periapical tissues. This in turn results in inflammation, delayed wound healing, and even bone resorption. This study aimed to explore the effect of the addition of an antioxidant like pachymic acid on the cytotoxicity of 4 root canal sealers, namely, Tubliseal (Kerr, Romulus, MI), a zinc oxide eugenol–based sealer; AH Plus (Dentsply De Trey GmbH, Konstanz, Germany), an epoxy resin–based sealer; Sealapex (Kerr), a calcium hydroxide–based sealer; and EndoREZ (Ultradent Products, South Jordan, UT), a methacrylate resin–based sealer.

Elimination of Intracanal Tissue and Debris through a Novel Laser-activated System Assessed Using High-resolution Micro–computed Tomography: A Pilot Study

Introduction

Laser-activated irrigation to remove organic debris from canal isthmuses was investigated using x-ray microfocus computed tomographic imaging.

Methods

A total of 14 extracted human mandibular molars were used. The mesial canals were prepared using a standardized instrumentation protocol. Two groups (n = 7) underwent final irrigation using either standard needle irrigation (SNI) or photon-induced photoacoustic streaming (PIPS). After enlarging canals to 30/.06, canal volumes were reconstructed from micro–computed tomographic scans before and after irrigation to assess removal of organic tissue and inorganic debris by quantitative analysis of the superimposed volumes. Comparisons of the volumes were made using 2-way analysis of variance and Tukey method, with statistical differences considered significant at the alpha = 0.05 level.

Results

Debris removal and an increase in root canal system volume for the laser-activated PIPS group was more significant (P < .001) than for the SNI group (P = .04). Irrigation using PIPS increased the canal volume and eliminated debris from the canal system 2.6 times greater than SNI.

Conclusions

Eliminating debris from complex canal spaces found in mandibular molars was achieved at a significantly greater level using laser-activated PIPS irrigation compared with SNI.     

Geometric Analysis of the Distolingual Root and Canal in Mandibular First Molars: A Micro–computed Tomographic Study

IntroductionThe purpose of this study was to comprehensively assess by micro–computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.MethodsOne hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.ResultsAll DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.ConclusionsThe novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.     

Comparison of Fracture Toughness of All-Ceramic and Metal–Ceramic Cement Retained Implant Crowns: An In Vitro Study

To evaluate the fracture toughness of cement-retained implant-supported metal–ceramic molar crown with that of all-ceramic crowns, fabricated using IPS Empress 2 and yttria-stabilized zirconia copings. An dental implant and abutment was embedded in a clear polymethyl methacrylate model. A wax pattern reproducing the anatomy and dimension of a mandibular molar was made using inlay wax. Copings were made from the manufacturers guidelines for zirconia, metal ceramic and empress crown, in total of 21 copings, which were built for the crowns with metal layering ceramics specified by the manufacturers. The polymethylmethacrylate block-implant abutment complex was mounted on universal testing machine, and a static continuos vertical compressive load with a crosshead speed of 0.5 mm/min was applied. The breaking load and the peak load (in kilo Newtons) were recorded. The fractures for group I (zirconia–ceramic) and group II (metal–ceramic) occurred on the mesio-buccal aspect of the crowns involving the veneered ceramic layer while the catastrophic/bulk fracture was not observed. The mean value of breaking load for zirconia–ceramic, metal–ceramic and IPS-empress 2 was 3.4335, 3.071 and 1.0673 kN respectively. The mean value of peak load for zirconia–ceramic, metal–ceramic and IPS-empress 2 was 4.7365, 3.2757 and 1.566 kN respectively. It can be concluded that the zirconia–ceramic crown with the fracture toughness of 4.7365 ± 2.2676 kN has sufficient strength to allow clinical testing of these crowns as an alternative for metal–ceramic crowns (3.2757 ± 0.4681 kN).     

Evaluation of the marginal and internal discrepancies of CAD-CAM endocrowns with different cavity depths: An in vitro study

Statement of problem

The marginal and internal discrepancies of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns are unknown.

Comparative Evaluation of Dentinal Microcrack Formation before and after Root Canal Preparation Using Rotary,Reciprocating, and Adaptive Instruments at Different Working Lengths—A Micro–computed Tomographic Study

IntroductionThis study aimed to compare root dentinal microcrack formation after root canal shaping using rotary, reciprocating, and adaptive instruments at different working lengths using micro–computed tomographic imaging.MethodsOne hundred eighty extracted mature mandibular molar mesial roots with 2 separate canals were selected. The mesial roots were resected at the cementoenamel junction and randomly divided into 4 groups (n = 45) based on the nickel-titanium file system used: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold (Dentsply Maillefer), Twisted File Adaptive (SybronEndo, Orange, CA), and Reciproc Blue (VDW, Munich, Germany). Each of the 4 groups were then subdivided into 3 groups (n = 15) depending on the working length used for root canal preparation (ie, instrumentation 1 mm short, flush, and 1 mm beyond the major apical foramen). The roots were imaged with micro–computed tomographic scanning before and after root canal preparation. The cross-sectional images generated were screened to detect the presence of new microcracks.ResultsThe ProTaper Universal system significantly increased the number of postinstrumentation microcracks at all working lengths (P ≤ .05). No significant increase (P > .05) in postinstrumentation microcracks was observed in the ProTaper Gold, Twisted File Adaptive, or Reciproc Blue groups.ConclusionsRotary instrumentation induced a higher number of dentinal microcracks compared with reciprocating and adaptive instruments. Instrumentation at different working lengths did not significantly influence the formation of dentinal microcracks.     

Children with a cleft lip and palate: An exploratory study of the role of the parent–child interaction

IntroductionHaving a child with an orofacial cleft may be associated with a specific pattern of parenting. In order to investigate the parenting style, the present study assessed parent–child interactions during a problem-solving task performed under pressure.Material and methodsParent–child interactions were video recorded for 15 families with a child with a cleft lip and palate (CLP), which were then compared to 20 healthy families and 20 families with a child suffering from migraines. The children had to solve a puzzle within a specified time with either their mother or father.ResultsIn families with a child with CLP, mothers tried to support their children more often and children demonstrated more autonomous behaviour towards both parents than children in healthy and migraine-affected families. Moreover, the children with CLP relied less on their fathers for help and interrupted their fathers less frequently.ConclusionsAutonomous behaviour among children with CLP which is supported by their parents may represent psychosocial compensatory mechanisms in the family environment.