Assessment of dimensional stability of novel VPES impression material at different time intervals with standard disinfectants.

BACKGROUND: Vinyl polyether silicone (VPES) is a novel impression biomaterial made of a combination of vinyl polysiloxane (VPS) and polyether (PE). Thus, it is significant to assess its properties and behaviour under varied disinfectant test conditions. This study aimed to assess the dimensional stability of novel VPES impression material after immersion in standard disinfectants for different time intervals. METHODS: Elastomeric impression material used -medium body regular set (Monophase) [Exa'lence GC America]. A total of 84 Specimens were fabricated using stainless steel die and ring (ADA specification 19). These samples were distributed into a control group (n=12) and a test group (n=72). The test group was divided into 3 groups, based on the type of disinfectant used - Group-A- 2% Glutaraldehyde, Group-B- 0. 5% Sodium hypochlorite and Group-C- 2% Chlorhexidine each test group was further divided into 2 subgroups (n=12/subgroup) based on time intervals for which each sample was immersed in the disinfectants - subgroup-1- 10 mins and Subgroup 2- 30 mins. After the impression material was set, it was removed from the ring and then it was washed in water for 15 seconds. Control group measurements were made immediately on a stereomicroscope and other samples were immersed in the three disinfection solutions for 10 mins and 30 mins to check the dimensional stability by measuring the distance between the lines generated by the stainless steel die on the samples using a stereomicroscope at x40 magnification. RESULTS: The distance measured in the control group was 4397.2078 µm and 4396.1571 µm; for the test group Group-A- 2% Glutaraldehyde was 4396.4075 µm and 4394.5992 µm; Group-B- 0. 5% Sodium hypochlorite was 4394.5453 µm and 4389.4711 µm Group-C- 2% Chlorhexidine was 4395.2953 µm and 4387.1703 µm respectively for 10 mins and 30 mins. Percentage dimensional change was in the range of 0.02 - 0.25 for all the groups for 10 mins and 30 mins. CONCLUSIONS: 2 % Glutaraldehyde is the most suitable disinfectant for VPES elastomeric impression material in terms of dimensional stability and shows minimum dimensional changes as compared to that of 2% Chlorhexidine and 0.5% Sodium hypochlorite.

Assessment of changes in enamel colour following fixed orthodontic therapy using an advanced spectrophotometer: An in vivo study.

BACKGROUND: Any manipulation of the surface of natural teeth may result in a variation of their colour. The fixed orthodontic treatment (FOT) is one such procedure which alters the enamel surface during the procedure. OBJECTIVE: To clinically evaluate the colour changes in teeth associated with comprehensive FOT (to compare the changes in test and control groups) and to determine the relationship of age and gender on enamel colour due to FOT by using an advanced spectrophotometer. METHODS: The selection of sixty patients for the study was done randomly and among these thirty patients who underwent the FOT as the case group, the other thirty patients who did not need FOT, were the control group. The recordings of spectrophotometric data were done in a standardized manner for all patients in the labial circular region of every anterior tooth, following debonding and cleaning operations, and before bracket bonding. The Commission Internationale de l'Eclairage's L*, a*, and b* (lightness, red/green, and blue/yellow) tooth-type characteristics were used to measure color, and the associated color differences (DE) between the groups were computed. One-way ANOVA (a < 0.05) and the paired t-test were used to evaluate any changes in these color characteristics. RESULTS: Fixed orthodontic treatment is associated with changes in colour parameters. L* values decreased (P< 0.001), while a* and b* values increased (P< 0.001) at the end of treatment. All measured tooth types showed significant colour change (DE); their mean differences ranged from 1.64 to 2.96 DE units. CONCLUSIONS: Fixed orthodontics can change the natural colour of teeth. The CIE colour parameters L*, a*, and b* of natural teeth showed statistically significant differences after debonding the orthodontic appliances. The L* values decreased making the teeth look darker. The adolescent and male patients had more tooth colour changes than the adult and female groups.

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.

Predoctoral dental implant education techniques-students' perception and attitude.

PURPOSE: Dental implant (DI) therapy is in high demand and can only be rendered efficiently to graduating dentists by effective teaching methodologies. This study aimed to assess the perceptions and attitudes of dental graduates towards predoctoral DI education techniques and rehabilitation by DI. METHODS: A total of 26 well-structured questionnaires were distributed to 120 final-year students. Modified advanced teaching methodologies such as e-learning, small-group teaching-problem-based learning (SGT-PBL), and team-based learning were implemented for teaching DI. Its effects were assessed using a questionnaire set: the first section (DI Rehabilitation) with 12 questions and the second (DI teaching methods) with 14 questions. Statistical analysis was done using the Chi-square test, and a P-value < 0.05 was considered statistically significant. RESULTS: The response rate was 95.83%. Seventy-five percent of the students recommended DI for patients, and 78% of them agreed to it themselves. On comparing teaching methods for DI, on and before level 12, small-group teaching (PBL) was significantly at a higher proportion (P = 0.002), followed by seminars (P < 0.001). Students preferred small-group teaching PBL (60%), followed by e-learning (15%) and demonstration (10%). Ninety-two percent of the students agreed that DI is an important subject in the "bachelor of dental surgery" (BDS) program, but 78% of them felt that time was insufficient to complete the DI syllabus. CONCLUSIONS: The modified teaching methodologies used at level 12 for teaching DI enhanced students' interest and knowledge. The SGT-PBL teaching method was the most preferred. It is recommended that dental implantology topics should be started early in the undergraduate curriculum, and the topics should be widely divided throughout BDS.