An In Vivo Study to Compare Location of Neutral Zone Recorded with Two Materials.

AIM: To establish a relationship between the crest of the alveolar ridge and neutral zone and to compare its location recorded by two different material. METHODS AND MATERIALS: Thirty subjects were selected, and the location of the neutral zone was compared with the mandibular alveolar ridge crest. For each subject neutral zone was recorded by two different recording materials-Low fusing impression compound and tissue conditioner. After neutral zone recording, the relation between mandibular ridge crest and neutral zone location examined radiographically. The data so collected were checked for normality, descriptive statistics and the Mann-Whitney U test was used. RESULTS: Position of neutral zone was found towards lingual in the posterior, labial side in anterior and almost near to the alveolar ridge crest in premolar region. The thermoplastic flow of the material effects the position of neutral zone but no significant difference was noted in the positions of neutral zone recorded by the two materials in relation to the alveolar ridge crest. CONCLUSION: Location of the neutral zone is not affected by the material used in recording it. CLINICAL SIGNIFICANCE: The location of the neutral zone varies from subject to subject and mainly depends upon their musculature and can be recorded accurately by using correct technique irrespective of the materials used.

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.

Influence of time, temperature and humidity on the accuracy of alginate impressions.

BACKGROUND: The goal of the current in vitro study was to assess the dimensional accuracy of dental impressions when stored at different times, temperature and humidity. METHODS: Impressions were poured to an aluminium triangular die and three teeth placed at the three corners of the die. A total of 130 impressions were made, in which 10 were poured immediately following manufacturers' instructions and the remaining 120 specimens were divided into two groups on the basis of relative humidity during storage. Group-1: 100%, Group-2: 50% relative humidity. Impression was poured with type IV gypsum. The below points were chosen to determine the length between in each of the specimens using the traveling microscope with 10x magnifications after 24 hours of model recovery for calculating the effect of changes in storage conditions- relative humidity, temperature and delay in pouring the impressions, on dimensional accuracy. RESULTS: Analysis of the results revealed that the casts achieved by pouring alginate impressions without delay were most accurate than the delay pouring. With the increase in temperature and time, the distance between the points increased and the casts obtained were bigger. CONCLUSION: Irreversible hydrocolloids should be poured immediately for optimum dimensional stability.

An In Vitro Evaluation of Fracture Resistance Strength of Different Post Systems in Endodontically Treated Teeth.

AIM: This study aimed to evaluate the fracture resistance strength of different post systems in endodontically treated teeth. MATERIALS AND METHODS: Freshly extracted 60 single-rooted first premolars were selected for this study. Conventional step-back technique was used to prepare a canal for all the teeth. Obturation was carried out and post space was created using a Peeso reamer. All teeth were randomly divided into three groups of 20 samples in each group: Group I, teeth inserted with prefabricated carbon posts; Group II, teeth inserted with prefabricated zirconia posts; and Group III, teeth inserted with prefabricated everStick posts. Core buildup was performed using light-cured composite resin. Compressive load required to fracture the tooth was measured using a universal testing machine. RESULTS: The compressive strength of zirconia posts was highest with a mean of 796.10 ± 20.78 followed by carbon posts (628.22 ± 18.11) and lower compressive strength was exhibited by everStick posts (534.13 ± 19.98). An analysis of variance revealed a statistically highly significant difference (P < 0.005) among the different posts used, and a statistically significant difference between carbon posts vs. zirconia posts, carbon posts vs. everStick posts, and zirconia posts vs. everStick posts (P < 0.05). CONCLUSION: Zirconia posts show the maximum fracture resistance than the carbon posts and everStick posts.