Escherichia coli Cellular Activity and Frontal Trizonal Evaluation of Microspace Between Implants and Abutments Under Calibrated Cyclic Stress.

AIM: To evaluate microspace and microleakage between implant and abutments subjected to pre- and post-calibrated cyclic stress. MATERIALS AND METHODS: Twelve screw-retained implant prostheses with BioHPP polyetheretherketone (PEEK) abutment (Noris Dental Implant System Ltd., Nesher, Israel) (Group I) and 12 screw-retained implant prostheses with computer-assisted design/computer-assisted manufacturing (CAD/CAM) milled zirconia abutment (DentGallop, Houston, TX, USA) (Group II) were connected to their respective implant, and the prosthetic screw was torqued to 30N/cm (Noris). The microspace was evaluated using scanning electron microscopy (SEM; TeScan, Brno, Czech Republic). Twenty-four samples were then induced to cyclic stress (Lokesh Industries, Pune, India) simulating 180 days duration of oral stress. The microspaces (Group IA and Group IIB) were measured post-cyclic stress. Group I and II were again renamed into Group Ia and Group IIb for microbial study. Both implant assemblies were immersed in fresh soybean casein digest broth (SCDB) (Himedia, Mumbai, India) and subsequently inoculated with 1.0µL E. coli suspension (Himedia) at the open end and incubated at 37ºC for seven days. After the incubation period, cellular activity was determined by the spread plate method, and total colony-forming units (CFU) were calculated. The results were evaluated using independent T and Mann-Whitney tests. RESULT: Average and microspace at the implant-abutment junction of Group I samples in the front right was 12.98µm, center 13.76µm, front left 13.22µm, and in Group II samples, the front right was 18.52µm, center 17.84µm, front left 18.58µm.After being subjected to cyclic loading, the mean levels of the vertical microgap for Group IA samples were: in the front right region 10.37µm, in the center 9.34µm, in the front left 10.51µm and in Group IIB samples front right was 14.59µm, center 13.39µm, front left 13.8µm. Independent t-tests showed insignificant differences between the two groups. The median value of microbial leakage of Group Ia samples after cyclic loading was 30 x 103 CFU/ml, and Group IIb samples were 42 x 103 CFU/ml and were significant. CONCLUSION: There was minimal variation in the mean microspace between the BioHPP PEEK abutment and CAD/CAM milled zirconia abutment, and it was insignificant before and after cyclic stress. BioHPP PEEK abutment-titanium implant interfaces showed significantly decreased microbial leakage than CAD/CAM milled zirconia abutment-titanium implant interfaces after cyclic stress.

Comparative evaluation of wear resistance of CAD-CAM zirconia and cast cobalt chromium alloy for indirect restorations against human enamel - An In Vitro study.

PURPOSE OF THE STUDY: To comparatively evaluate the wear resistance of two different posterior indirect restorative materials against human enamel. MATERIALS AND METHODS: Two different posterior indirect restorative materials of ten in each Group-I (Monolithic zirconia) (n = 10) and Group-II (Cast cobalt chromium) (n = 10) were formed into disc and used as a substrate for the wear test. Freshly extracted mandibular first premolars were used as a pin (antagonist) (n = 20). Pin-on-disc wear testing machine was used to simulate the masticatory parameters and evaluation of the wear parameters was done after 1,20,000 cycles, with load of 40N for specific duration. Data related to wear testing procedure were tabulated and evaluated. Results were statistically analyzed using Mann-Whitney test and Wilcoxon signed rank test. RESULTS: Mean surface roughness value (Ra value) obtained for Group-I disc test samples showed no statistical significance (P value < 0.05). Mean wear rate value of test disc samples was statistically significant between Group-I and Group-II (P value < 0.05). Mean surface roughness value was statistically significant between Groups-I and II before and after wear test (P value < 0.05). CONCLUSION: From the results obtained, it was found that the Group-I (Monolithic zirconia) exhibited higher wear resistance than Group-II (cast cobalt chromium) and causes less wear to the opposing enamel antagonist.

Compatibility of Nonoriginal Abutments With Implants: Evaluation of Microgap at the Implant-Abutment Interface, With Original and Nonoriginal Abutments.

PURPOSE: The purpose of this study was to evaluate the fit of nonoriginal abutments to implants at the implant abutment junction. MATERIALS AND METHODS: Twenty titanium implants from a single manufacturer were randomly divided into 2 groups of ten each. Ten titanium premachined original abutments (group I) and ten titanium premachined nonoriginal abutments (from different manufacturer-group II) were connected to the implants with the recommended manufacturer torque level and then embedded into autopolymerizing clear acrylic resin blocks. After overnight curing, these blocks were vertically sectioned using water jet sectioning machine and evaluated under scanning electron microscope following the sequential cleaning procedures. The microgap at the implant-abutment interface for all the samples was measured using pixel counting software and subjected to statistical analysis using nonparametric Mann-Whitney U test. RESULTS: The mean microgap at the implant-abutment interface at the external, middle, and internal points was 1.597, 1.399, and 1.831 µm, respectively, for group I and 2.395, 2.488, and 3.339 µm, respectively, for group II samples. Nonparametric Mann-Whitney U test showed statistically significant difference between 2 groups at the midpoint for the nonoriginal abutments compared with the original ones. CONCLUSION: Within the limitations of the study, the mean microgap at the implant-abutment interface at the platform level at the external, middle, and internal points for both original abutments and nonoriginal abutments was found to be within clinically acceptable limits.

Comparative Evaluation of the Masking Ability of Lithium Disilicate Ceramic with Different Core Thickness on the Shade Match of Indirect Restorations over Metallic Substrate: An In vitro Study.

PURPOSE: The purpose of this in vitro study was to comparatively evaluate the masking ability of lithium disilicate ceramic with different core thickness on the shade match of indirect restorations over metallic substrate. MATERIALS AND METHODS: A total of 30 heat pressed lithium disilicate ceramic discs of low translucency were fabricated with diameter 10mm and thickness of 1 mm, 1.3 mm and 1.6mm with each thickness consisting of 10 samples to be used in the study. Thirty Ni-Cr metal discs of diameter 10mm were used to simulate metallic substrates .The colour difference of the lithium disilicate ceramic disc before and after cementation were measured using CIE LAB system. RESULTS: The mean colour difference (ΔE) of Group I,Group II, Group III before cementation with the Ni-Cr metal discs was 17.32,13.01 and 11.73 respectively. The mean colour difference (ΔE) of Group I,Group II, Group III after cementation with the Ni-Cr metal discs was 16.32,12.10, 11.05 respectively. CONCLUSION: The mean colour difference of the three groups were found to be more than the clinically acceptable perceptibility threshold (ΔE < 3.3) indicative of reduced masking ability of all the three groups of ceramic discs over metallic substrate used in this study.

Comparative Evaluation of the Antimicrobial Efficacy of Three Immersion Chemical Disinfectants on Clinically Derived Poly(Vinyl Siloxane) Impressions.

PURPOSE: To comparatively evaluate the antimicrobial efficacy of freshly prepared electrolyzed oxidizing water (EOW) with that of 2.4% glutaraldehyde (GA) and 1% sodium hypochlorite (SH) on clinically derived poly vinyl siloxane (PVS) impressions. MATERIALS AND METHODS: Four clinically derived PVS impressions each were obtained from 10 subjects. One impression from each subject was randomly kept as control (group I), without disinfection. The remaining three impressions were randomly disinfected by immersion in either 2.4% GA (group II), 1% SH (group III), or freshly prepared EOW (group IV). The samples were subjected to microbial culture individually on brain heart infusion (BHI) agar medium. The organisms isolated were confirmed by visual examination and gram staining. Mean colony forming units (CFU) were counted, log10 reduction obtained and compared. Data were statistically analyzed using one-way ANOVA, followed by multiple comparisons using Tukey-HSD post hoc tests (p < 0.05). RESULTS: Streptococci, Staphylococci, Pseudomonas, Candida, Proteus, Klebsiella, and E. coli were isolated from all impressions including the controls, except those disinfected by EOW. All three disinfectants showed significant reduction in CFU and log10 reduction values as compared to the controls. EOW showed significantly higher reduction in log10 values compared to GA and SH, whereas GA and SH showed similar reductions. EOW, GA, and SH showed kill rates of 100%, 99.60%, and 99.82%, respectively. CONCLUSION: EOW showed significant antimicrobial efficacy as evidenced by reduction in log10 values when used as an immersion disinfectant for PVS impressions when compared with the results obtained using GA and SH. These results need further investigation. CLINICAL IMPLICATIONS: EOW shows high antimicrobial efficacy when used as an immersion disinfectant as compared to GA and SH for clinically derived PVS impressions.

Lip repositioning surgery for correction of excessive gingival display.

Esthetic demands have considerably increased over the years in routine clinical practice. A pleasant smile can give supreme confidence to an individuals personality. However, a perfect smile is dictated by a perfect balance of the white (teeth) and pink (gingival) display. This balance can be managed different treatment modalities, which is based on proper diagnosis. This case report demonstrates a successful management of gummy smile with a lip-repositioning procedure in a patient with an incompetent upper lip. This was accomplished by removing a partial thickness strip of mucosa from the maxillary buccal vestibule and suturing the lip mucosa to the mucogingival line. This resulted in a narrower vestibule and restricted muscle pull, thereby resulting incompetent lips and reduced gingival display during smiling.

Influence of Surface Modifications of Acrylic Resin Teeth on Shear Bond Strength with Denture Base Resin-An Invitro Study.

BACKGROUND: Debonding of artificial teeth from the denture base is an important issue for edentulous patients rehabilitated with conventional or implant supported complete dentures. AIM: The purpose of this study was to evaluate shear bond strength between denture base resin and acrylic resin denture teeth subjected to three different surface modifications on the ridge lap area as compared to unmodified denture teeth. MATERIALS AND METHODS: Forty acrylic resin central incisor denture teeth were selected and randomly divided into four test groups. The teeth in each group were subjected to one of the three different surface modifications, namely, chemical treatment, sandblasting and placement of retentive grooves on the ridge lap area respectively, prior to packing of the denture base resin. The group with unmodified teeth served as control. Forty acrylic resin test blocks thus obtained were tested for shear bond strength between acrylic resin teeth and denture base resin in Universal Testing Machine. Data obtained was statistically analysed using one-way ANOVA and Student- Newman- Keul's test (p< 0.05). RESULTS: Analysis of shear bond strength revealed that retentive grooves on the ridge lap area showed highest bond strength values followed by sandblasting and both were statistically significant compared to the control and chemically treated groups. Unmodified surface of the resin teeth showed the least bond strength. CONCLUSION: Within the limitations of this invitro study the placement of retentive grooves or sandblasting of the ridge lap area showed highly significant improvement in shear bond strength compared to the unmodified surface. Chemical treatment did not result in any significant improvement in the shear bond strength compared to the unmodified surface.