Dimensional stability of 3D-printed edentulous and fully dentate hollowed maxillary models over periods of time.

BACKGROUND: Dental casts made utilising digital workflow are becoming more common because to their speed and cost savings. However, studies on their dimensional accuracy over time with diverse designs are missing. OBJECTIVE: The aim of this in vitro study was to assess the dimensional stability of 3D-printed edentulous and fully dentate hollowed maxillary models with 50-micrometer resolution over 1 day, 14 days, and 28 days using surface matching software. METHODS: Scanned edentulous and fully dentate maxillary typodont models were used as references. The models were scanned by a desktop lab scanner of 15-micrometer accuracy (D900, 3Shape). Then, the files were used in designing software (Meshmixer, Autodesk) to create hollowed maxillary casts. Fifteen edentulous and 15 fully dentate (total of 30) models were printed using a DLP lab printer (Cara print 4.0, Kulzer). The 3D-printed models were scanned using the same desktop lab scanner of 15-micrometer accuracy at intervals of baseline days, 1 day, 14 days, and 28 days to assess the effect of aging (n = 120). The dimensional changes were quantified and compared using the root mean square (RMS) method, expressed in micrometres (µm). The study employed repeated measures analysis of variance (ANOVA) to assess and compare the root mean square (RMS) values across the variables. The data was analysed using SPSS (26, Chicago, Illinois, USA). RESULTS: The RMS of the edentulous models rapidly increased from a mean value of 0.257 at the beginning of the study to 0.384 after twenty-eight days. However, the mean RMS values for the dentate models did not change much over the four intervals. It varied only from 0.355 to 0.347. The mean values for edentulous patients increased from 0.014 to 0.029 during the period from baseline to twenty-eight days. However, the mean average values decreased for the dentate models from 0.033 to 0.014 during this period. By utilizing ANOVA, mean RMS values increased insignificantly till one day but significantly to fourteen and twenty-eight days. Dentate model mean values differed insignificantly across four intervals. Repeated measures ANOVA for combined and separated data showed no significant differences across edentulous, dentate, and total models over times. CONCLUSION: The study revealed changes in the dimensions of 3D-printed edentulous models over a span of 3 and 4 weeks. Caution should be applied when using 3D-printed dental master models for constructing definitive prostheses on edentulous models over a period of 3 to 4 weeks.

Technical assessment of shear bond strength at ceramo-alloy interface after various surface treatment combinations and application of metal bonding agent.

BACKGROUND: Bonding between metal and ceramic is one of the most important aspects of a successful prosthesis. Various methods have been recommended for preparing the metal surface to enhance the bond between metal and ceramic including the use of a metal bonding agent. OBJECTIVE: This study aims to evaluate and compare the shear bond strength of the metal-ceramic (M-C) interface after combinations of various surface treatments including the application of a metal bonding agent. METHOD: 40 Ni-Cr alloy specimens were made and divided into 4 groups of 10 each based on the combination of surface treatments. Sandblasting, surface grinding, and Oxidation heat treatment (OHT) were performed on specimens from Group 1 (Control). In addition, Group 2 specimens received ultrasonic cleaning, Group 3 steam cleaning, and Group 4 metal bonding agent application. Following surface treatments on all specimens, porcelain build-up was performed, and shear bond strength was tested in a Digital Universal testing machine. The statistical tests used were independent t-test and ANOVA. RESULTS: Results revealed that Group 4 specimens had the highest mean value of shear bond strength of 39.087 MPa while Group 3 specimens showed the least mean shear bond strength of 18.154 MPa with highly statistically significant results (p< 0.001). CONCLUSION: The surface treatments and application of bonding agent to metal prior to porcelain application resulted in increased shear bond strength of the metal-ceramic interface.

Retentive Forces and Deformation of Fitting Surface in RPD Clasp Made of Polyether-Ether-Ketone (PEEK).

BACKGROUND: Polyetheretherketone (PEEK) has provided the option to fabricate RPDs with aesthetics unlike metal RPDs, but little attention has been paid to its suitability, especially towards the retentive forces and deformation of the clasp. This study aimed to examine the retentive forces and the fitting surface (inner surface) deformation of clasps made from PEEK and compare it with cobalt-chromium (Co-Cr) clasp. METHODS: Forty-two circumferential clasps (14 Co-Cr and 28 PEEK) were fabricated and divided into two groups with clasp undercuts (0.25 mm and 0.5 mm) with thicknesses of 1 mm and 1.5 mm. Each was examined for retentive forces after cycle test on its abutment for 360 cycles. Initial and final retentive forces were recorded. The fitting surface deformation was determined using 3-Matic research analysis software. RESULTS: The results revealed that highest mean initial retentive force was of Co-Cr clasps with 0.50 mm undercut 22.26 N (±10.15 N), and the lowest was the 1 mm PEEK clasps with 0.25 mm undercut 3.35 N (±0.72 N) and highest mean final retentive force was the Co-Cr clasps with 0.50 mm undercut 21.40 N (±9.66 N), and the lowest was the 1 mm PEEK clasps with 0.25 mm undercut 2.71 N (±0.47 N). PEEK clasps had a lower retentive force than Co-Cr clasps with 0.50 undercut. PEEK clasps (1.5 mm) at 0.25 mm undercut had the least deformation (35.3 µm). PEEK showed significantly less deformation (p ≤ 0.014) than Co-Cr. CONCLUSION: The deformation of PEEK clasps fitting surface was lower than Co-Cr clasps and retentive forces were close to the Co-Cr clasps, suggesting the use of PEEK as an aesthetic clasp option for RPD framework.

Assessment of PCL between dental implant prosthesis and natural teeth using a digital force analyzer.

BACKGROUND: The prime concern of an implant-supported prosthesis (ISP) is to maintain an optimal proximal contact tightness, which further maintains arch integrity, improves masticatory effectiveness, and minimizes peri-implantitis. OBJECTIVE: To investigate the loss of proximal contact tightness between single tooth implant-supported prosthesis and the adjacent natural teeth. METHODS: Forty patients treated by a single mandibular first molar ISP, aged between 18-50 years were selected. All were randomly allocated in Group I and Group II. Group I, 20 subjects who have received ISP without an insertion of Essix retainer, and Group II patients received an insertion with Essix retainer. The groups were subdivided into Subgroup A, B, and Subgroup C, D, in which A and C are control groups. To measure the tightness at proximal contact points, a digital force analyzer was used. Proximal contact tightness (PCT) was measured immediately after the placement of the prosthesis, 3 months, 6 months, and 1-year follow-up respectively, and the PCT values at end of 1 year were statistically evaluated. Statistical analysis was done, mean and standard deviation was calculated by independent sample t-test wit p< 0.05 as a statistically significant value. RESULTS: In Group I, towards the end of 1 year, 2.09 N (65.5%) and 1.50 N (53.1%) loss of PCT were found on mesial and distal contact areas respectively. In Group II, loss of PCT at mesial contact area was 0.87 N (28.9%) and at distal contact area was 1.77 N (53.3%), which is significantly less compared with the non-usage of Essix retainer (p< 0.05). CONCLUSION: The usage of Essix retainer, PCT increases especially on the mesial contact area. The frequency of contact loss was decreased. Thus, to minimize the loss of proximal contact the usage of Essix retainer is recommended.

Dental Management Considerations for Patients with Cardiovascular Disease-A Narrative Review.

Dental therapists encounter patients with various systemic diseases of which cardiovascular disease (CVD) patients form a significant segment. Relation between oral health and cardiac diseases has been well established. Common cardiac disorders encountered in a dental practice include arterial hypertension, heart failure, ischemic heart disease, cardiac arrhythmias, infective endocarditis, stroke, and cardiac pacemaker. Patients with CVDs pose a significant challenge to dental therapy. These patients need special considerations and an adequate understanding of the underlying cardiovascular condition to provide safe and effective dental treatment. Based on the cardiac condition, an appropriate modification in dental care is crucial. A multidisciplinary approach including the patient's cardiologist can potentially reduce complications and improve dental treatment results. This review aims at unfolding the risks associated with the dental management of a cardiac patient and outlines the measures to be undertaken for optimum dental treatment.

Novel CAD-CAM zirconia coping design to enhance the aesthetics and strength for anterior PLZ crowns.

BACKGROUND: The aesthetics and strength of anterior porcelain layered zirconia (PLZ) crowns are mainly affected by the zirconia (Zr) coping design. There is a need for a modified design to enhance aesthetics with strength. OBJECTIVES: The purpose of this study was to compare the fracture resistance of anterior PLZ crowns having modified CAD-CAM Zr coping designs (in terms of thickness and marginal collar designs) with standard Zr copings. METHODS: Fifty PLZ crowns were fabricated and divided into two groups: Gr 1: Standard Zr Coping (SZC) (control gr) with 0.5 mm thickness (Facial-F, Mesial-M, Distal-D, incisal-I, and Palatal-P) without a collar; Gr 2: Collar Zr Coping (CZC) (test gr) with 2.5 mm collar height on M, D, P and 0.2 mm F and variable facial wall thickness. Subgroups: Gr 2a: (CZC-0.5 mm) facial wall thickness 0.5 mm; Gr 2b: (CZC-0.4 mm) facial wall thickness 0.4 mm; Gr 2c: (CZC-0.3 mm) facial wall thickness 0.3 mm; Gr 2d: (CZC-0.2 mm) facial wall thickness 0.2 mm. The fracture load was determined and analysed using One-way ANOVA and Dunnet test. RESULTS: The minimum fracture load was 927.36 ± 127.80 N observed for Gr 2c (CZC at 0.3 mm) while the maximum fracture load was 1373.61 ± 146.54 N observed for Gr 2a (CZC at 0.5 mm). A highly significant difference in mean fracture load among various Zr coping groups (p< 0.001) was determined. CONCLUSIONS: Novel Zr coping design for anterior PLZ crowns can provide better aesthetics with strength. Reducing the thickness of Zr coping in the aesthetic zone to 0.2 mm and providing a modified collar design (2.5 mm collar height on M, D, P, and 0.2 mm F) would provide strength without jeopardizing aesthetics.

Can Herbal Extracts Serve as Antibacterial Root Canal Irrigating Solutions? Antimicrobial Efficacy of Tylophora indica, Curcumin longa, Phyllanthus amarus, and Sodium Hypochlorite on Enterococcus faecalis Biofilms Formed on Tooth Substrate: In Vitro Study.

AIM: The purpose of this study was to evaluate the antimicrobial efficacy of Tylophora indica, Curcumin longa, and Phyllanthus amarus on Enterococcus faecalis biofilms formed on the tooth substrate. Sodium hypochlorite was used as a positive control. DMSO (dimethyl sulfoxide), the vehicle for the herbal extracts, was used as the negative control. MATERIALS AND METHODS: Extracted human teeth were biomechanically prepared, vertically sectioned, placed in the tissue culture wells exposing the root canal surface to E. faecalis to form a biofilm. At the end of the third week, all groups were treated for 15 min with the test solutions and the control. The results were analyzed both quantitatively and qualitatively. RESULTS: Statistical analysis was performed by using one-way analysis of variance and compared by the Mann-Whitney test using the Statistical Package for the Social Sciences (SPSS) software, version 20.0. The qualitative assay with the 3-week biofilm on the canal portion showed complete inhibition of bacterial growth for NaOCl, whereas samples treated with herbal solutions showed significant reduction of bacterial growth compared to control group, which showed 139.9 × 109 CFU/mL among the experimental herbal solutions groups. P. amarus has shown maximum bacterial count followed by C. longa and T. indica. CONCLUSION: NaOCl 5% showed maximum antibacterial activity against 3-week biofilm on tooth substrate. T. indica, P. amarus, and C. longa showed statistically significant antibacterial activity against 3-week biofilm. The use of herbal alternatives might prove to be advantageous considering the several undesirable characteristics of NaOCl.