A study on the wear of enamel caused by monolithic zirconia and the subsequent phase transformation compared to two other ceramic systems.

PURPOSE: The purpose of this in vitro research project was to evaluate and compare the wear behavior of human tooth enamel opposing monolithic zirconia and other different ceramic restorative materials and also to observe the tetragonal to monoclinic phase transformation in zirconia-based ceramics that may occur while simulating wear occurring at room temperature in a wet environment. MATERIALS AND METHODS: A total of sixty samples were prepared for this study. Fifteen discs of glazed zirconia, 15 discs of polished zirconia without glaze, 15 discs of metal ceramic, and 15 discs of lithium disilicate were fabricated. Sixty extracted premolars were collected and randomly divided into four groups of 15 each. The discs and extracted human premolars were placed onto holders on a two-body wear machine under a constant load of 5 kg to simulate the oral wear cycle. A diffractometer was used to analyze phase transformation. One-way analysis of variance and Tukey's post hoc tests was used. RESULTS: The mean loss of height of tooth samples and its standard deviation for Group I (monolithic zirconia with glaze), Group II (mechanically polished monolithic zirconia without glaze), Group III (porcelain fused to metal), and Group IV (glazed monolithic lithium disilicate) was obtained as 0.2716 ± 0.1409, 0.1240 ± 0.0625, 0.1567 ± 0.0996, and 0.2377 ± 0.1350, respectively. The highest mean loss in height was observed in Group I and the least was observed in Group II. CONCLUSION: Mechanically polished zirconia showed the least amount of enamel wear followed by porcelain fused to metal and glazed monolithic lithium disilicate, whereas glazed monolithic zirconia showed the highest enamel wear.

An evaluation of wear of human enamel opposed by ceramics of different surface finishes.

STATEMENT OF PROBLEM: Surface of porcelain restoration is a matter of clinical concern because of its abrasive action on the opposing enamel. PURPOSE: This study comparatively evaluated wear of enamel when opposed by three different surface finishes of ceramic. MATERIALS AND METHODS: A total of 60 metal-ceramic discs (10 mm × 2 mm) with different surface finishes were fabricated. They were divided into four groups of autoglazed ceramic surface, over glazed ceramic surface, ceramic surface polished with Shofu polishing kit and ceramic surface polished with DFS polishing wheels and paste. Each group comprised of 15 discs. Sixty human teeth samples were prepared from freshly extracted, unrestored, caries free, nonattrited maxillary first premolars. Each tooth sample was weighed before wear testing using AT200 Mettler Toledo electronic analytical balance of 0.0001 g accuracy. Occlusal surfaces of these teeth were then abraded against the substrates in a wear machine for a total of 10,000 cycles. Each tooth sample was weighed after 5000 cycles and after the total of 10,000 cycles, respectively, using the same balance. Differences in weight of tooth samples before and after wear testing were evaluated statistically using one-way analysis of variance and Bonferroni's correction for multiple group comparisons. RESULTS: The values obtained for percentage weight loss after 10,000 cycles for over glazed ceramic surface were marginally higher than values obtained for autoglazed surface. It was observed that values obtained for percentage weight loss by polished ceramic after 10,000 cycles were statistically less as compared to the values obtained with autoglazed and over glazed ceramic surface (P < 0.001). There was no statistically significant difference between the values obtained by polished ceramic surfaces of two different groups. CONCLUSION: Enamel wear produced by polished porcelain is substantially less than autoglazed and over glazed porcelain. No significant difference was found in enamel wear when opposed by ceramic surfaces polished by two different methods. This study indicates the potential damage porcelain can inflict upon enamel and suggests that porcelain should be polished instead of over glazed.

Diabetes and Edentulism: A Survey on Oral Health-Related Quality of Life in Indian Sub-Population.

Aims: The current study was conducted to assess the oral health-related quality of life in completely edentulous and diabetes mellitus (DM) patients. The null hypothesis of the survey is that there is no effect of both edentulism and diabetes on the oral health-related quality of life of patients. Settings and Design: A descriptive cross-sectional study. Methods and Materials: Test Groups: The study population was divided into three groups: • Group 1: Non-diabetic patients, wearing a complete denture. • Group 2: Diabetic patients, wearing a complete denture. • Group 3: Diabetic, completely dentulous patients. Sample Size: In total, 332 (200 males and 132 females) patients. Methodology of the Survey: Telephonic and interview methods of surveying were employed to evaluate patients. Statistical Analysis Used: The mean values, standard deviation (SD) and P value were calculated using a one-way analysis of variance (ANOVA). The level of significance was set at 5% (*P value < 0.05, ***P value < 0.001, NS: statistically non-significant). The higher the score, the higher the impact and vice-versa. Inter-group comparisons were done with post-hoc Bonferroni's test for multiple group comparisons. Results: Data collected from the survey were statistically significant, results were noted between the completely edentulous patients wearing dentures and diabetic dentulous patients. Though DM is a potent risk factor for periodontitis, leading to edentulism, statistical analysis of this study suggested that the oral health-related quality of life was affected significantly only due to edentulism and not due to DM. This is indicative of the fact that the quality of the prostheses itself determines the overall oral health-related quality of life, irrespective of whether the patient is a diabetic or not. Therefore, it can be said that the present trends of prosthodontic management of patients with DM are successfully restoring the patients physiological, psychological as well as social needs. Conclusions: Complete edentulism is the terminal outcome of a multifactorial process involving biological factors and patient-related factors. Diabetes and edentulism are both potential comorbid factors governing the oral health-related quality of life. The correlation between the two is complex and needs a thorough evaluation to improve the overall health of patients in the current clinical practice.

A comparative evaluation of colour stability of different resin cements and its influence on the final shade of All-Ceramic Restorations: An in-vitro Study.

Introduction: Colour changes of the luting material can become clinically visible affecting the aesthetic appearance of thin ceramic veneers. Therefore, unfortunately, the long-term success of veneers is tied to the colour stability of the luting agent used to cement them. Aim: To compare the colour stability of different resin cements and its influence on the final shade of overlying ceramic using two different thicknesses of ceramic. Material and Methodology: Sixty disc-shaped specimens of high translucency (HT) A2 shade of two thicknesses (0.5 mm & 1 mm) were prepared from lithium disilicate glass-ceramic. The discs of each thickness were further divided into three groups randomly depending upon the resin cements used. Group A - light cure resin cement - Variolink N LC by Ivoclar Vivadent in clear shade, Group B - base paste of dual-cure resin cement - Variolink N by Ivoclar Vivadent in transparent shade and Group C dual-cure resin cement - Clearfil esthetic cement EX by Kuraray in clear shade were used to compare their colour stability. A spectrophotometer was used for the colour measurements of the specimens before and after accelerated ageing. The colour stability was determined by colour differences (ΔE) using the coordinates L*, a* and b* in the pre and post accelerated ageing. Results: On comparing the three resin cements, Group A showed the lowest ΔE, whereas the highest ΔE was observed in Group B. This finding was constant for discs of both thicknesses. Conclusion: Even though statistically significant results were observed between the groups, they were not visibly differentiable.

Assessment of different surface treatments and shear bond characteristics of poly-ether-ether-ketone: An in vitro SEM analysis.

Aim: The aim of this study is to assess the surface roughness and shear bond characteristics of pol-ether-ether-ketone after different surface treatments. Setting and Design: An in vitro, prospective. Materials and Methods: One hundred and twenty disc-shaped samples of 10 mm diameter and 2 mm thickness were milled and subjected to following surface treatments: 110 µm alumina particles, 98% concentrated sulfuric acid, and 10-20 µm synthetic diamond particles. Surface characteristics of treated sample were studied under SEM with ×500 and ×1000 magnification. Shear bond strength (SBS) with composite resin discs embedded in acrylic blocks after luting with self-etch resin cement and resin-modified glass ionomer cement (RMGIC) was evaluated using the universal testing machine (Instron®, Massachusetts U. S. A). Statistical Analysis Used: The data collected were evaluated using the Analysis of variance and Tukey's honest significant difference post hoc test. Results: Highest SBS and SR were noted with self-etch resin cement in the given order: 98% sulfuric acid (2.106 ± 0.186 µm), followed by alumina particles (1.706 ± 0.160 µm) and synthetic diamond particles (1.101 ± 0.167 µm). Conclusion: The SBS of self-etch resin cement was higher compared to RMGIC for all three surface treatments done on test samples. Hundred percent samples treated by all three surface treatment methods showed mixed type of failure.

Comparative evaluation of marginal and internal fit of endocrowns using lithium disilicate and polyetheretherketone computer-aided design - computer-aided manufacturing (CAD-CAM) materials: An in vitro study.

PURPOSE: To evaluate the marginal and internal fit of endocrowns with different computer-aided design/computer-aided manufacturing (CAD-CAM) materials by measuring them with a stereomicroscope (µm). MATERIALS AND METHODS: A mandibular first molar typodont tooth was prepared to receive an endocrown. The preparation was scanned using an extra-oral scanner. Endocrowns (n = 20) were fabricated using lithium disilicate (IPS e. max CAD LT block; CEREC Ivoclar Vivadent, Liechtenstein) and polyetheretherketone (PEEK) (breCAM. BioHPP®; Bredent, UK) using CAD-CAM technique. Marginal gap was evaluated using a stereomicroscope at the midpoint of all four surfaces (mid buccal, mid lingual, mid mesial, mid distal). This was followed by sectioning of the endocrowns in a sagittal plane along with the prepared tooth to evaluate the internal fit at four different points (A, B, C, D) using a stereomicroscope. Statistical analysis was performed using one-way analysis of variance test. RESULTS: Mean values of marginal gap of lithium disilicate and PEEK endocrowns are 56.6 ± 6.1 µm and 81.3 ± 10.1 µm, respectively. Mean value internal gaps of lithium disilicate and PEEK endocrowns are 158.2 ± 11.1 µm and 199.1 ± 13 µm, respectively. Results in the present study have shown that the marginal and internal fits of lithium disilicate endocrowns are superior to that of PEEK endocrowns. CONCLUSIONS: Based on the outcomes of this in vitro study, the marginal and internal fit of lithium disilicate endocrowns is better than PEEK endocrowns. The marginal gap clinically acceptable is <120 µm. The marginal gap values recorded in this study are within the acceptable range for both materials.

Assessment of the existing dental education environment at a dental teaching institution.

INTRODUCTION: An important aspect of creating a competent medical practitioner is the teaching-learning environment that shapes the mentality and instigates an urge among the students to learn. To facilitate a motivating learning setup, the faculty members need to inadvertently establish a successful and safe learning environment which is extensively feasible, given that the faculty gets to control their own style of teaching. A lot of research focuses on student's perception of the learning environment, seldom studies have reported the teacher's perspective. This present study focuses on the teacher's side of the story regarding the current scenario of the workplace that is one of the essential factors to alter the approach toward andragogy. MATERIALS AND METHODS: A cross-sectional questionnaire study was carried out using the Assessment of Medical Education Environment by Teachers (AMEET) questionnaire. The AMEET questionnaire was administered to 50 staff members at MA Rangoonwala College of Dental Sciences and Research Centre, Pune. All the participants were assured of confidentiality of their personal details and they all signed a written informed consent before participating in the study. RESULTS: Majority of the participants had a positive attitude which was seen more in the seniors compared to the juniors. The teacher's perception of teaching is that there needs to be a greater emphasis on what the student learns rather than what the teacher does. Junior staff members felt that students do not prepare and come for classes nor are the expected outcomes clear to them. Assignments are also a task for the students that are never on time. CONCLUSION: It was observed that more senior faculties were positive toward the existing education environment. In addition, even though opportunities are available for the staff as well as students for upgrading and imbibing newer information, they were not being benefitted by the same due to underutilization.

A comparison of fracture resistance of endodontically treated teeth restored with bonded partial restorations and full-coverage porcelain-fused-to-metal crowns.

The aim of this study was to evaluate the use of bonded partial restorations compared with full-coverage porcelain-fused-to-metal (PFM) crowns as a viable treatment option for endodontically treated posterior teeth. Forty-five recently extracted maxillary first premolars were collected, endodontically treated, and mounted in acrylic blocks. The specimens were randomly divided into three groups and prepared to receive their respective restorations. The teeth in group 1 received full-coverage porcelain-fused-to-metal crowns. The teeth in group 2 received bonded partial restorations made from pressed ceramics (lithium disilicate) involving a functional cusp (palatal). Finally, group 3 received bonded partial restorations made from pressed ceramics involving the buccal cusp and keeping a functional cusp (palatal) intact. All group 1 restorations were cemented using glass ionomer cement. Restorations in groups 2 and 3 were bonded using a dual-cured resin cement. All specimens were subjected to an aging process and tested for shear bond strength using a universal loading machine. The mean force applied in Newtons to cause failure for group I was 674.90 ± 94.16 N, for group 2, 463.46 ± 61.11 N, and for group 3, 849.33 ± 68.92 N. P values obtained using one-way analysis of variance showed a highly significant difference between groups 2 and 3 (P = .001), groups 1 and 2 (P = .001), and groups 1 and 3 (P = .001). The fracture modes observed in all groups involved restorations and tooth fracture. This in vitro study suggests that endodontically treated posterior teeth with intact functional cusps can be restored with bonded partial porcelain restorations. However, if the loss of tooth structure involves the functional cusp, full-coverage PFM crowns are the treatment of choice.

Comparative evaluation of dimensional accuracy of different polyvinyl siloxane putty-wash impression techniques-in vitro study.

BACKGROUND: Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. The purpose of this in vitro study was to compare the dimensional accuracy of the casts obtained from one step double mix, two step double mix polyvinyl siloxane putty- wash impression techniques using three different spacer thicknesses (0.5mm, 1mm and 1.5mm), in order to determine the impression technique that displays the maximum linear dimensional accuracy. MATERIALS & METHODS: A Mild steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Express, 3M ESPE) and customarily made perforated metal trays. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 0.5-mm, 1mm and 1.5mm-thick metal-prefabricated spacer caps. The accuracy of the 4 different impression techniques was assessed by measuring 7 dimensions (intra- and inter abutment) (20-µm accuracy) on stone casts poured from the impressions of the mild steel model. The data were analyzed by one sample't' test. RESULTS: The stone dies obtained with all the techniques had significantly larger or smaller dimensions as compared to those of the mild steel model (P<0.05). The order for highest to lowest deviation from the mild steel model was: single step putty/light body, 2-step putty/light body with 0.5mm spacer thickness, 2-step putty/light body1.5mm spacer thickness, and 2-step putty/light body with 1mm spacer thickness. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their standard deviations from the master model (P<0.05), were noted. CONCLUSIONS: The 2-step putty/light-body impression technique with 1mm spacer thickness was most dimensionally accurate impression methods in terms of resultant casts. How to cite this article: Dugal R, Railkar B, Musani S. Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. J Int Oral Health 2013;5(5):85-94.

An in vitro Comparative Evaluation of Micro Tensile Bond Strength of Two metal bonding Resin Cements bonded to Cobalt Chromium alloy.

BACKGROUND: The purpose of this study was to evaluate and compare the micro tensile bond strength of two metal bonding resin cements to sandblasted cobalt chromium alloy. MATERIALS & METHODS: Eight, Cobalt chromium alloy blocks of dimensions 10x5x5 mm were cast, finished and polished. One of the faces of each alloy block measuring 5x5mm was sandblasted with 50 µm grit alumina particles. The alloy blocks were then cleaned in an ultrasonic cleaner for 1 min and then air dried with an air stream. The Sandblasted surfaces of the two alloy blocks were bonded together with 2 different metal bonding resin systems (Panavia F Kuraray and DTK Kleber - Bredent). The samples were divided into 2 groups (n=4). Group 1- Two Co-Cr blocks were luted with Panavia cement. Group 2- Two Co-Cr blocks were luted with DTK Kleber-Bredent cement. The bonded samples were cut with a diamond saw to prepare Microtensile bars of approximately 1mm x 1mm x 6mm. Thirty bars from each group were randomly separated into 2 subgroups (n=15) and left for 3hrs (baseline) as per manufacturer's instructions while the other group was aged for 24hrs in 370C water, prior to loading to failure under tension at a cross head speed of 1mm/min. Failure modes were determined by means of stereomicroscopy (sm). Statistical analysis was performed through one way - ANOVA. RESULTS: Significant variation in micro-tensile bond strength was observed between the two metal bonding resin systems. CONCLUSION: DTK showed higher mean bond strength values than Panavia F cement both at baseline and after aging. How to cite this article: Musani S, Musani I, Dugal R, Habbu N, Madanshetty P, Virani D. An in vitro Comparative Evaluation of Micro Tensile Bond Strength of Two metal bonding Resin Cements bonded to Cobalt Chromium alloy. J Int Oral Health 2013;5(5):73-8.