Interim Crowns Research Articles

Comparison of Marginal Accuracy of Interim Restoration Fabricated from Self-cure Composite and Autopolymerizing Acrylic Resin: An In Vitro Study.

ABSTRACTBackground and Objectives:One of the important steps toward achieving a successful fixed partial denture treatment is the fabrication of interim restorations with good marginal adaptation. Poor marginal adaptation of the interim restorations will allow ingress of fluids and microorganisms between the restorations and may lead to caries and pulpitis. The objective of this study was to evaluate and compare the marginal accuracy of interim restorations made from two polymethyl methacrylate (PMMA) and two bis-acryl materials.Materials and Methods:An in vitro method was used to replicate a clinical procedure in which the interim crown was made using a direct technique. A maxillary first molar typodont tooth was prepared to receive a full cast crown restoration having 1 mm chamfer and a taper of 5°, and then the prepared artificial tooth was cast into a cobalt chromium metal die. Wax patterns were prepared on the metal die using type 2 inlay wax for full metal crowns. The impression of the die along with the wax pattern was made with a putty-type polyvinyl siloxane, and this impression was used as a mold for making interim restorations. Two PMMA and two bis-acryl provisional crown materials were distributed as follows: Group A: Unifast Trad (GC Dental), Group B: DPI self-cure tooth molding material, Group C: Structur 2 QM (VOCO), and Group D: Cool Temp Natural (Coltene/Whaledent). A total of 60 interim restorations from all the four materials were fabricated (15 interim restorations from each material). The marginal discrepancy of the interim restoration was determined by measuring the space between the margin of the interim restoration and the finish line of the metal die at four vertical reference lines previously marked at the midpoint of the metal die finish line at the buccal, palatal, mesial, and distal surfaces of the die. The marginal gaps were visualized at ×45 magnification using a stereomicroscope and interpreted using ProgRes image capture software.Results:The mean marginal discrepancy calculated in PMMA materials was 269 µm for DPI and 205 µm for Unifast Trad, and the mean marginal gap for the bis-acryl material was 171 µm for Cool Temp and 140 µm for Structur 2 QM.Interpretation and Conclusion:Comparison of marginal accuracy showed that bis-acryl provisional crown material showed better marginal accuracy than PMMA provisional crown material. Among the materials tested, Structur 2 QM showed the best marginal accuracy, and the least marginal accuracy was shown by DPI.

Assessment of the Adaptation of Interim Crowns using Different Measurement Techniques.

To compare the internal fit and marginal discrepancy of acrylic resin interim crowns fabricated by different manufacturing methods, and to test the consistency of measuring marginal discrepancy and internal fit between different measuring techniques. A dentoform mandibular left first molar was prepared for an all-ceramic crown. Thirty-six interim crowns were fabricated and divided into three groups (n = 12): group BAC (Bis-acrylic composite, fabricated manually), group CAM (CAD/CAM polymethylmethacrylate resin, milled), and group 3DP (3D printed methacrylic oligomers, printed). The internal fit of the interim crowns was evaluated by the silicone replica technique and by X-ray microcomputed tomography (µCT) technique. The marginal discrepancy of the interim crowns was evaluated by the vinyl polysiloxane (VPS) (Aquasil Ultra XLV) impression technique and by optical coherence tomography (OCT) technique. Data were statistically analyzed using ANOVA and Turkey tests at α = 0.05. Pearson correlation test was used to evaluate the correlation between the different measurement techniques and marginal discrepancy/internal fit. The manually fabricated interim crowns (group BAC) had significantly greater discrepancy of internal fit than did the digitally fabricated crowns (group CAM and group 3DP) measured by both silicone replica technique and µCT 2-dimensional (2D) image measurement. There were no statistically significant differences in the cement space volume values obtained by the µCT image technique between group BAC and group 3DP (p = 0.285). The coefficientof determination between the two volumetric measurement techniques was low (R2 = 0.30). For marginal discrepancy, the manually fabricated interim crowns had a wider absolute marginal discrepancy than both digitally fabricated groups (p < 0.05). In both the VPS impression and OCT assessment, there was no statistically significant difference between group CAM and group 3DP (p = 0.798 and 0.994, respectively). The coefficientof determination between the VPS impression and OCT techniques for marginal discrepancy measurement was low (R2 = 0.23). Digitally fabricated interim crowns (group CAM and group 3DP) had better internal fit and smaller marginal discrepancy than manually fabricated interim crowns (group BAC). For comparison of the different evaluation techniques, the silicone replica technique and µCT measurements had low correlation for internal fit assessment, as did the PVS impression and OCT techniques for marginal discrepancy test.

Digital impression of teeth prepared with a subgingival vertical finish line: A new clinical approach to manage the interim crown

Intraoral scanner can simplify the prosthodontic workflow with reduction of time, cost and several steps. However, clinic conditions can affect the quality of the digital impressions, especially if the tooth is prepared with subgingival vertical finish line. This report describes a technique to manage the interim crown and to obtain accurate digital impression of an abutment tooth with subgingival vertical finish line without the use of retraction techniques.

Assessment of the internal fit and marginal integrity of interim crowns made by different manufacturing methods

Statement of problemThe adaptation of interim crowns made by subtractive and additive manufacturing has not been well investigated. PurposeThe purpose of this in vitro study was to evaluate the internal fit and marginal discrepancy of interim crowns made by different manufacturing methods. Material and methodsA dentoform mandibular left first molar was prepared for a ceramic crown and scanned for the fabrication of 48 stereolithical resin dies and interim crowns. Group CAM included 16 ZCAD interim crowns made by computer-aided design and computer-aided manufacturing (CAD-CAM) technology; group 3DP, 16 NextDent MFH interim crowns made by digital light processing technology; and group APP, 16 Jet interim crowns manually made by using autopolymerizing acrylic resin and used as controls. The silicone replica technique was used to determine the internal discrepancy volume before definitive cementation. All crowns were cemented with Temp-Bond NE under a 50-N load and bench set for 10 minutes before microcomputed tomographic (μCT) scan assessment. The volume of cement space was measured by using the μCT scan 3-dimensional (3D) images, and gap distance at assigned locations was recorded by using the μCT scan 2-dimensional (2D) images. The marginal discrepancy was measured by the polyvinyl siloxane (PVS) impression technique and using a stereomicroscope. Data were analyzed by ANOVA and the Tukey honestly significant difference tests (α=.05). The association between different measuring techniques was analyzed by the Pearson correlation test. ResultsThe gap distance between interim crowns and dies from all 3 groups measured by using the μCT scan 2D images ranged from 0.13 mm to 0.55 mm, with the highest value found at the central occlusal location in group APP. The total average gap distance values recorded for group APP were significantly higher than those for group CAM and group 3DP (P<.05). No significant differences were found in internal discrepancy and cement space volume between group CAM and group 3DP (P>.05). The Pearson correlation test showed a moderate correlation (r=0.69) between the silicone replica technique and the μCT scan technique in determining cement space volume. When the PVS impression technique was used to measure the marginal discrepancy, the mean values obtained from group APP were statistically significantly higher than those from group CAM and group 3DP (P<.05). No statistically significant difference in marginal discrepancy was found between group CAM and group 3DP (P=.70). ConclusionsDigitally fabricated interim crowns had better internal fit and smaller marginal discrepancy than manually constructed interim crowns. The silicone replica technique and μCT scan technique measurements had a moderate correlation in assessing the adaptation of cemented interim crowns.

Fabrication technique for a custom implant emergence profile on 3D printed casts

A procedure is described for fabricating a removable resilient soft-tissue replica that accurately replicates the contoured emergence profile of an interim implant-supported restoration on a cast fabricated by 3D printing. The technique uses digital scanning and 3D printing technologies to produce a 3D printed replica of the implant-supported interim crown, which is then used to fabricate the custom soft-tissue replica. This straightforward technique allows the accurate replication of the emergence profile without retaining the interim crown or fabricating a new one. No additional clinical appointments are needed.

A digital intraoral implant scan technique using a combined healing abutment and scan body system

Multiple clinical appointments are generally needed after implant placement for the delivery of definitive implant-supported crowns. Digital and conventional workflows are accompanied by the frequent connection and disconnection of prosthetic components such as healing abutments, interim crowns, impression posts, and definitive abutments before the placement of definitive crowns. Repetitive removal of these components may result in trauma on the component–peri-implant soft tissue interface. This report describes a technique for the fabrication of an implant-supported crown by using a combined healing and scan body abutment in a digital workflow. This technique reduces the number of appointments and allows the formation of a soft tissue emergence profile similar to that of the definitive crown, which can help minimize patient discomfort during placement of an implant crown.

The influence of abutment macro-design on clinical and radiographic peri-implant tissue changes for guided, placed, and restored implants: A 1-year randomized controlled trial.

The aim was to evaluate the peri-implant tissue levels over a 1-year period for implants connected to either convex or concave final abutments at the time of implant placement. In this randomized, double masked, controlled clinical study, twenty-eight patients with one missing maxillary premolar were allocated to receive one single implant with abutment of either convex (CX Group) or concave (CV Group) emergence shape. A block randomization sequence was used to allocate treatments. Opaque sealed randomization envelopes were used for allocation concealment. All implants received final abutments and interim crowns at implant placement and permanent crowns following 3months. Clinical and radiographic data were collected at the time of implant placement (IP), final prosthesis delivery (PR), and 12months following implant placement (FU-1). One patient from the CX Group (n=13) dropped out from the study and for one patient from CV Group (n=13), the implant failed to integrate. The mean change in peri-implant buccal mucosa position (MP) from IP to FU-1 was -0.76±0.72mm for CX Group and -0.69±0.89mm for CV Group (p=0.8). The amount of bone remodeling above the implant platform from IP to FU-1 was -0.66±0.46mm for the CX Group and -0.24±0.25mm for the CV Group (p=0.007). Buccal bone thickness was significantly correlated with the amount of buccal MP change from IP to FU-1 (r=0.4, p=0.038). The study failed to support the hypothesis that abutment macro-design has an effect on peri-implant mucosa margin position changes over time.

Effect of polymerization temperature on the properties of autopolymerizing resin

Statement of problemThe polymerization conditions of an autopolymerizing resin affect its physical properties, and at chairside, 3 different methods are commonly used: cooling in cold water, warming in warm water, and heating in hot water. However, the effects of polymerization temperature on the physicomechanical properties of autopolymerizing resin are unclear. PurposeThe purpose of this in vitro study was to determine the effect of polymerization temperature on the physicomechanical properties of autopolymerizing resin, including shrinkage, water absorption, surface roughness, amount of residual monomer, and flexural strength. Material and methodsThe experiment was designed to simulate a direct technique commonly used for the fabrication of interim crowns. Autopolymerizing resin specimens were made according to the powder-to-liquid ratio recommended by the manufacturer and soaked in water at 13°C, 37°C, or 60°C for 2 minutes to mold the resin until polymerization was completed 4 minutes after mixing. Shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength were measured immediately after polymerization and after 1, 3, and 7 days in distilled water at 37°C. Differences among these properties among the 3 different temperatures groups were statistically analyzed by using 1-way ANOVA and the Tukey honest significant difference test (α=.05). ResultsShrinkage tests showed that the 13°C group had significantly lower shrinkage (P=.004 for 37°C and P<.001 for 60°C) than the other groups immediately after specimen preparation. The 13°C group had significantly higher surface roughness after 0 (P<.001 for 37°C and P<.001 for 60°C), 1 (P=.025 for 37°C and P=.012 for 60°C), 3 (P<.001 for 37°C and P<.001 for 60°C), and 7 days (P<.001 for 37°C and P<.001 for 60°C) than those in the other groups and significantly higher water absorption rates (P=.033 for 37°C and P<.001 for 60°C) than the other groups during the 7 days after fabrication. However, the 13°C group showed significantly higher weight percentage of residual monomers than the 60°C group at 0 (P<.001) and 1 day (P<.001). Finally, 3-point bend tests showed that the 13°C group had significantly lower flexural strength at 0 (P<.001), 1 (P<.001), 3 (P<.001), and 7 days (P<.001) than the other groups. ConclusionsThe temperature environment during dental chairside polymerization of the autopolymerizing resin affected the physicomechanical properties of shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength.

Functional and esthetic restorative treatment with preheated resins in a patient with ectodermic dysplasia: A clinical report

Ectodermal dysplasia is a heterogeneous genetic condition affecting 1.6 to 22 per 100000 people. Oral manifestations associated with this condition include hyperdontia, hypodontia, microdontia, and conical teeth. Traditional treatment consists of a combination of orthodontic and rehabilitation therapies. The initial treatment stage uses removable prostheses and interim crowns for long periods, thus increasing risks for developing secondary caries. This clinical report describes the use of direct composite resin bonding with preheated compactable resins applied to vacuum-formed trays filled with clear silicone. This restorative treatment provides predictable, inexpensive, minimally invasive, functional, and esthetic recovery before orthodontic treatment.

Color stability and marginal integrity of interim crowns: An in vitro study.

Objective:Many commercial dental materials are used to fabricate interim restorations. This study aimed to compare the color stability and the marginal integrity of four different interim crown materials.Materials and Methods:An ivorine right maxillary central incisor was prepared for a full coverage all-ceramic restoration. A total of 36 specimens in the form of crowns were fabricated on the master die using four different materials (n = 9); Polymethyl methacrylate (PMMA) resin (TrimPLUS), PMMA computer-aided design, and computer-aided manufacturing (CAD-CAM) blocks (Ceramill TEMP), cold cure bis-acryl resin (Success CD), and bis-acryl resin dual-cure composite (TempSpan). Color change ΔE for each sample was calculated by measuring its color as Commission Internationale de l’Eclairage L* a* b* with a spectrophotometer before and after immersing in a concentrated tea solution for 7 days. Marginal gap was measured at four reference points using stereomicroscope at ×40. One-way ANOVA and the Tukey multiple comparisons test were used to determine any statistically significant difference between the four groups, (α = 0.05).Results:Success CD showed significantly the greatest color change (7.7) among all the tested materials, while no significant difference was found between the other three materials. TempSpan showed significantly the highest marginal gap formation (430.15 μm), while no significant difference was found between the three other materials.Conclusions:Bis-acryl resin composite materials demonstrated clinically noticeable change in color while PMMA materials demonstrated superior color stability. Dual cure interim materials exhibited significantly higher marginal discrepancy in comparison to PMMA and cold cure bis-acrylic resin materials. CAD-CAM PMMA material exhibited the best color stability and marginal integrity.

Fit of interim crowns fabricated using photopolymer-jetting 3D printing

Statement of problemThe fit of interim crowns fabricated using 3-dimensional (3D) printing is unknown. PurposeThe purpose of this in vitro study was to evaluate the fit of interim crowns fabricated using photopolymer-jetting 3D printing and to compare it with that of milling and compression molding methods. Material and methodsTwelve study models were fabricated by making an impression of a metal master model of the mandibular first molar. On each study model, interim crowns (N=36) were fabricated using compression molding (molding group, n=12), milling (milling group, n=12), and 3D polymer-jetting methods. The crowns were prepared as follows: molding group, overimpression technique; milling group, a 5-axis dental milling machine; and polymer-jetting group using a 3D printer. The fit of interim crowns was evaluated in the proximal, marginal, internal axial, and internal occlusal regions by using the image-superimposition and silicone-replica techniques. The Mann-Whitney U test and Kruskal-Wallis tests were used to compare the results among groups (α=.05). ResultsCompared with the molding group, the milling and polymer-jetting groups showed more accurate results in the proximal and marginal regions (P<.001). In the axial regions, even though the mean discrepancy was smallest in the molding group, the data showed large deviations. In the occlusal region, the polymer-jetting group was the most accurate, and compared with the other groups, the milling group showed larger internal discrepancies (P<.001). ConclusionsPolymer-jet 3D printing significantly enhanced the fit of interim crowns, particularly in the occlusal region.

A pilot clinical study of immediate provisionalization with a chairside computer aided design and computer aided manufacture monolithic crown for single tooth immediate implant placement

Objective: To evaluate the primary clinical outcomes of immediate provisionalization with a monolithic crown utilizing a novel chairside computer aided design and computer aided manufacture (CAD/CAM) workflow for single tooth immediate implant placement. Methods: This pilot study was a prospective within-subjects design. Thirteen consecutive patients were included and diagnosed with untreatable single incisor or premolar with fine general and local anatomical conditions. The trial was conducted at Department of Implantology, Peking University School and Hospital of Stomatology, Beijing, between January 2016 and June 2016. The teeth were extracted atraumatically and implants were immediately placed in the fresh sockets. Two screw-retained interim crowns were fabricated for the same site utilizing different workflows, a monolithic lithium disilicate (LS2) crown produced by CEREC (Sirona, Germany) chairside CAD/CAM system (CER group) and a manually fabricated resin crown utilizing conventional workflow (CONV group) respectively. The patients were blinded to the group allocation of the two interim crowns. After the clinical try-in for both crowns in a randomized sequence, the patients' level of satisfaction was assessed with a virtual analogue scale (VAS) questionnaire. The restorations chosen by patients themselves were seated in the implants by one experienced prosthodontist. The accuracy, aesthetic effect and clinical time consumption of both groups were compared. Statistical analyses were performed with the Wilcoxon signed rank test. Results: All patients were treated with atraumatic tooth extraction, immediate implant placement using flapless surgery and immediate provisionalization in a single visit. The interim crowns of both groups could be fitted with or without slight adjustments. For each patient, the interim crown of CER group was chosen to be seated with a relatively higher VAS result. The white esthetic score (WES) results demonstrated no statistically significant difference between CER group (7.5±1.1) and CONV group (7.9±0.9) (P>0.05). The mean total work time was significantly different resulting in (131.9±5.0) min for CER group and (205.2±6.3) min(P<0.05). The major difference lied in the laboratory work time, resulting in (113.5±6.3) min for CER group which was significantly shorter than (185.6±6.6) min for CONV group. As for impression taking time, the CER group (7.5±0.8) min was significantly shorter than CONV group (11.7± 1.1) min (P<0.05). However, analysis for clinical adjustment time showed a significantly longer time for CER group [(11.0±2.1) min vs (8.0±2.8) min, P<0.05]. After 3-6 months of observation, the overall survival rate was 100%. Screw loosening occurred in 4 patients and was tightened again. No other major complication soccurred. Conclusions: The full digital workflow utilizing CEREC chairside CAD/CAM system to fabricate interim crowns after immediate implant placement in one single visit was feasible. It was more time-efficient and could effectively shorten the laboratory work time compared to the conventional workflow. Patients demonstrated high satisfaction and there was no statistical difference in WES results compared to the conventional workflow. Favorable clinical outcomes were gained in this short-term follow-up study.

Evaluation of internal fit of interim crown fabricated with CAD/CAM milling and 3D printing system.

PURPOSEThis study is to evaluate the internal fit of the crown manufactured by CAD/CAM milling method and 3D printing method.MATERIALS AND METHODSThe master model was fabricated with stainless steel by using CNC machine and the work model was created from the vinyl-polysiloxane impression. After scanning the working model, the design software is used to design the crown. The saved STL file is used on the CAD/CAM milling method and two types of 3D printing method to produce 10 interim crowns per group. Internal discrepancy measurement uses the silicon replica method and the measured data are analyzed with One-way ANOVA to verify the statistic significance.RESULTSThe discrepancy means (standard deviation) of the 3 groups are 171.6 (97.4) µm for the crown manufactured by the milling system and 149.1 (65.9) and 91.1 (36.4) µm, respectively, for the crowns manufactured with the two types of 3D printing system. There was a statistically significant difference and the 3D printing system group showed more outstanding value than the milling system group.CONCLUSIONThe marginal and internal fit of the interim restoration has more outstanding 3D printing method than the CAD/CAM milling method. Therefore, the 3D printing method is considered as applicable for not only the interim restoration production, but also in the dental prosthesis production with a higher level of completion.

Ulteriori applicazioni degli scanner intraorali: duplicazione di corone e ponti provvisori funzionalizzati

ObjectivesInterim restorations are an essential part of the prosthodontic therapy, but they can give some problems, such as fractures. A fractured provisional can be repaired, but the initial mechanical strength is lost. Our aim is to introduce a sapioneering technique meant to obtain a copy of a functionalized interim prosthesis. Materials and methodsAn interim crown was relined and polished. Just before cementation, it was removed from the mouth and scanned with an intraoral scanner (3D Progress, MHT Srl, Verona, Italy). A 3D model of both the outer and inner surface was generated and sent to a milling centre. ResultsA new crown, as a copy of the interim prosthesis, was manufactured by using a material available on the market. The manufactured prosthesis was clinically acceptable and needed only minor occlusal adjustments. ConclusionsProstheses produced with this workflow are cheaper, less time-consuming and more durable as compared with a chairside conventional method. Interim or durable prostheses can be milled without the need for Computer Aided Design (CAD) and the relevant costs.

A Novel Technique for Immediate Loading Single Root Form Implants With an Interim CAD/CAM Milled Screw-Retained Crown.

A technique is described where an interim abutment and crown are fabricated in the laboratory by utilizing computer-aided design/computer-aided manufacturing (CAD/CAM) technology and placed the day of dental implant surgery. The design and contours of the interim crown are designed by the computer software to be identical to the contours of the tentatively designed definitive prosthesis. The interim crown satisfies esthetics immediately after dental implant surgery while allowing the tissue to heal and obtain contours similar to the contours of the definitive prosthesis. The interim crown can be either cement retained or screw retained. The presented technique describes fabrication of a screw-retentive interim crown. After osseointegration is confirmed, a definitive impression is made with a CAD/CAM impression coping. The definitive prosthesis is then fabricated.

In vitro evaluation of the marginal integrity of CAD/CAM interim crowns

Statement of problemThe accuracy of interim crowns made with computer-aided design and computer-aided manufacturing (CAD/CAM) systems has not been well investigated. PurposeThe purpose of this in vitro study was to evaluate the marginal integrity of interim crowns made by CAD/CAM compared with that of conventional polymethylmethacrylate (PMMA) crowns. Material and methodsA dentoform mandibular left second premolar was prepared for a ceramic crown and scanned for the fabrication of 60 stereolithical resin dies, half of which were scanned to fabricate 15 Telio CAD-CEREC and 15 Paradigm MZ100-E4D-E4D crowns. Fifteen Caulk and 15 Jet interim crowns were made on the remaining resin dies. All crowns were cemented with Tempgrip under a 17.8-N load, thermocycled for 1000 cycles, placed in 0.5% acid fuschin for 24 hours, and embedded in epoxy resin before sectioning from the mid-buccal to mid-lingual surface. The marginal discrepancy was measured using a traveling microscope, and dye penetration was measured as a percentage of the overall length under the crown. ResultsThe mean vertical marginal discrepancy of the conventionally made interim crowns was greater than for the CAD/CAM crowns (P=.006), while no difference was found for the horizontal component (P=.276). The mean vertical marginal discrepancy at the facial surface of the Caulk crowns was significantly greater than that of the other 3 types of interim crowns (P<.001). At the facial margin, the mean horizontal component of the Telio crowns was significantly larger than that of the other 3 types, with no difference at the lingual margins (P=.150). The mean percentage dye penetration for the Paradigm MZ100-E4D crowns was significantly greater and for Jet crowns significantly smaller than for the other 3 crowns (P<.001). However, the mean percentage dye penetration was significantly correlated with the vertical and horizontal marginal discrepancies of the Jet interim crowns at the facial surface and with the horizontal marginal discrepancies of the Caulk interim crowns at the lingual surface (P<.01 in each instance). ConclusionsA significantly smaller vertical marginal discrepancy was found with the interim crowns fabricated by CAD/CAM as compared with PMMA crowns; however, this difference was not observed for the horizontal component. The percentage dye penetration was correlated with vertical and horizontal discrepancies at the facial surface for the Jet interim crowns and with horizontal discrepancies at the lingual surface for the Caulk interim crowns.

Microleakage of Glass Ionomer-based Provisional Cement in CAD/CAM-Fabricated Interim Crowns: An in vitro Study.

The aim of this study was to compare in vitro the marginal microleakage of glass ionomer-based provisional cement with resin-based provisional cement and zinc oxide non-eugenol (ZONE) provisional cement in computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated interim restorations. Fifteen intact human premolars were prepared in a standardized manner for complete coverage of crown restorations. Interim crowns for the prepared teeth were then fabricated using CAD/CAM, and the specimens were randomized into three groups of provisional cementing agents (n = 5 each): Glass ionomer-based provisional cement (GC Fuji TEMP LT™), bisphenol-A-glycidyldimethacrylate (Bis-GMA)/ triethylene glycol dimethacrylate (TEGDMA) resin-based cement (UltraTemp® REZ), and ZONE cement (TempBond NE). After 24 hours of storage in distilled water at 37°C, the specimens were thermocycled and then stored again for 24 hours in distilled water at room temperature. Next, the specimens were placed in freshly prepared 2% aqueous methylene blue dye for 24 hours and then embedded in autopolymerizing acrylic resin blocks and sectioned in buccolingual and mesiodistal directions to assess dye penetration using a stereomicroscope. The results were statistically analyzed using a nonparametric Kruskal-Wallis test. Dunn's post hoc test with a Bonferroni correction test was used to compute multiple pairwise comparisons that identified differences among groups; the level of significance was set at p < 0.05. All groups exhibited marginal microleakage; the Bis-GMA/TEGDMA resin-based provisional cement demonstrated the lowest microleakage scores, which were statistically different from those of the glass ionomer-based provisional cement and the ZONE cement. The provisional cementing agents exhibited different sealing abilities. The Bis-GMA/TEGDMA resin-based provisional cement exhibited the most effective favorable sealing properties against dye penetration compared with the glass ionomer-based provisional cement and conventional ZONE cement. Newly introduced glass ionomer-based provisional cement proved to be inferior to resin-based provisional cement as far as marginal microleakage is concerned.

Preimpression troughing with the diode laser: A preliminary study

Statement of problemThe mechanical-chemical technique and the use of a laser are methods for displacing the gingiva to make an accurate impression of the preparation for a complete crown. The tissue needs to be displaced and the hemorrhage controlled to capture the prepared finishing line in the impression. The degree of undesirable gingival recession after these displacement techniques is unknown. PurposeThe purpose of this pilot clinical study was to clinically monitor and compare the regeneration of the gingival tissue by using 2 methods of gingival displacement in the same participant: the mechanical-chemical technique with double cords impregnated with aluminum chloride and the 810 nm diode laser (Odyssey; Ivoclar Vivadent AG). Material and methodsA total of 6 participants needing 2 crowns on natural teeth were included in this study. At the first visit, the teeth were prepared with a 0.5-mm subgingival finishing line and interim crowns were fabricated. One of the teeth was randomly assigned to the double cord technique with 2 (# 000 and # 1) impregnated 5% aluminum chloride cords and the other to the 810 nm diode laser. An adjacent tooth served as a control. A device was made that would function as a fixed reference point for the measurements at different time intervals. A notch was created on the device to position the digital ruler between the occlusal notch and the free gingival margin to measure the distances. The measurements were recorded for each patient before displacement of the gingiva and at the time of cementation of the definitive crowns. The patients were followed at 1 week, 3 weeks, and 8 weeks after cementation of the definitive crowns. ResultsThe amount of recession with the cord impregnated with aluminum chloride was 0.26 mm 8 weeks after cementation of the definitive crowns with a range between 0.00 mm and 0.72 mm. The diode laser showed an average recession of 0.27 mm with a range between 0.01 mm and 0.68 mm. ConclusionsThis study found an average loss of gingival height of 0.26 mm for the double cord technique and 0.27 mm for the laser. The amount of recession was considered not clinically significant.

Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials

Statement of problemThe effects of surface sealant agents on the surface roughness and color stability of interim crown materials are unknown. PurposeThe purpose of this in vitro study was to evaluate the effects of different polishing methods on the surface roughness and color stability of 4 interim crown materials. Material and methodsA total of 160 specimens were fabricated from 2 poly(methyl methacrylate) (PMMA; Tab 2000, Dentalon Plus) and 2 bis-acryl (Tempofit, Protemp 4) interim crown materials and divided into 4 groups (n=10) according to applied surface treatment procedures: conventional polishing (control) and 3 surface sealant (Palaseal, Optiglaze, Biscover) coupling methods. Surface roughness (Ra) values were measured with a profilometer. Color parameters were measured with a spectrophotometer before and after staining in coffee. Color differences (CIEDE 2000 [ΔE00]) were calculated. Data were statistically analyzed with 2-way ANOVA and the Tukey honest significant differences test (α=.05). ResultsThe Ra values of Tempofit with Biscover were significantly lower than their control group, Tab 2000 and Dentalon Plus control groups (P<.05). The highest ΔE00 was calculated for Tempofit control (P<.05). The Dentalon Plus control group had significantly higher ΔE00 values than the other groups, except for the Tempofit and Tab 2000 control groups.The Tab 2000 control ΔE00 was significantly higher than the other groups, except for Dentalon Plus with Palaseal and Dentalon Plus with Optiglaze. ConclusionsAll specimens had a surface roughness higher than the plaque accumulation threshold (0.20 μm). Smoother surfaces were observed for Tempofit with Biscover when compared with theTempofit control. The color change observed with the Dentalon Plus, Tab 2000, and Tempofit control groups was clinically unacceptable. Nonperceivable color changes were seen with Protemp 4 with Optiglaze, Tempofit with Optiglaze, and Tempofit with Biscover. Perceivable but clinically acceptable color changes were observed when sealants were used for all other test groups and Protemp 4 control.

Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually

Statement of problemInterim restorations represent an essential treatment step; however, the optimal resin material for long-term interim restorations requires investigation. PurposeThe purpose of this in vitro study was to compare the color stability, water sorption, wear resistance, surface hardness, fracture resistance, and microleakage of computer-aided design/computer-aided manufacturing-(CAD/CAM) fabricated interim restorations with those of manually fabricated interim restorations. Material and methodsEpoxy replicas were made from a prepared maxillary first premolar. On the replicas, interim crowns were fabricated and divided into the following groups: CAD/CAM poly(methyl methacrylate) (PMMA) blocks (CC), autopolymerizing temporary resin (AP), automix temporary resin (AM), and thermoplastic resin (TP). After cementation, all specimens were subjected to thermocycling and dynamic fatigue. The CIE Laboratory color coordinates were then recorded before and after immersion in coffee, tea, carbonated cola, and red wine. Water sorption was evaluated by using an immersion technique. Wear resistance was measured in a surface abrasion device. Vickers microhardness was measured on polished specimens. Fracture resistance was evaluated by axial loading with a universal testing machine. Marginal dye penetration was evaluated by sectioning the interim restorations after immersion in methylene blue (α=.05). ResultsColorimetric analysis revealed a large degree of color alteration (ΔE) in the manually fabricated interim restorations: AP = ΔE of 6.7 ±2); AM = ΔE of 7.1 ±1.5), and TP = ΔE of =5.4 ±3.1. The CC group demonstrated color stability (ΔE=2.1 ±0.2). CAD/CAM interim restorations demonstrated significantly lower water sorption, higher wear resistance, higher surface hardness, and significantly higher fracture resistance (1289±56N) compared with manually fabricated interim restorations (AP=996 ±45, AM=899 ±37, and TP=1179 ±41). The stereomicroscopic examination of sectioned specimens demonstrated the absence of dye penetration in all tested specimens. ConclusionsCAD/CAM interim crowns presented stable physical and mechanical properties and may be used for long-term interim restorations.