Stress Distribution on Prepared Tooth With Shoulder and Radial Shoulder Margin to Receive Crowns of Three Different Materials: A Finite Element Analysis.

Aim and background This study aims to determine the stress distribution on the prepared tooth at the margins with shoulder and radial shoulder finish lines when an occlusal load of 300N was applied to ceramic, zirconia, and polyether ether ketone (PEEK) crowns. Materials and methods Six models of mandibular first molar teeth were fabricated. The tooth models were subdivided into two groups with shoulder and radial shoulder margins, respectively (n = 18). The teeth were restored with three different prosthetic crown materials (ceramic, zirconia, and PEEK). To simulate the typical forces experienced by a prosthetic crown material in a lower posterior tooth during chewing and biting, an occlusal load of 300N was applied to each of the samples, and the maximum principal stress (Pmax) and von Mises stress were calculated, respectively. These samples were then compared and evaluated to determine the material best suited as a prosthetic crown material of choice for a lower posterior tooth. Results Among the materials used, the maximum principal stress value was the least in PEEK crowns. The von Mises stress value was highest for the zirconia crown with shoulder margin and was least for the PEEK crown with a similar margin. Conclusion PEEK as a crown material was found to be a better choice for lower posterior teeth as there was the least maximum principal stress at the margin, irrespective of either shoulder or radial shoulder finish line used.

Evaluation of Tensile Bonding Strength of Permanent Soft Relining Material to Denture Base Acrylic Resin after Erbium:Yttrium- Aluminum-Garnet Laser Treatment - An in vitro Study.

PURPOSE: The purpose of the study was to assess the effectiveness of erbium:yttrium-aluminum-garnet (Er:YAG) laser surface pretreatment at various pulse durations of exposure on increasing the tensile bonding strength of permanent soft relining material and acrylic resin. MATERIALS AND METHODS: Polymethyl methacrylate resin samples were fabricated and grouped as comparison group (no laser surface pretreatment) and three test groups (received Er:YAG laser surface pretreatment at various pulse durations of 10 s, 20 s, and 30 s) for bonding with the permanent soft relining material, Molloplast B. Following the surface pretreatment, the samples were tested for tensile stress using a universal testing machine. Loads at the point of failure were noted and the tensile bond strength values were obtained. Parametric tests of one-way-ANOVA and Tukey's post hoc tests were done. RESULTS: The highest tensile bonding strength was recorded in Group C, and the control group recorded the lowest bonding strength. CONCLUSION: Er:YAG laser surface pretreatment at 10 Hz, 3 W, and 300 mJ for 30 s improved the bonding strength of the permanent soft relining material to heat-processed acrylic resin material.

Cytotoxic effect of indigenously fabricated dental magnets for application in prosthodontics.

CONTEXT: Dental magnets are used for retaining removable prostheses such as a removable partial denture, complete denture, and maxillofacial prosthesis. They provide good retention for the prostheses. However, the elements released from the magnets may be cytotoxic for the tissues. Therefore, it is necessary to evaluate their cytotoxic effect on cell lines. AIM: The aim of the study is to check the cytotoxic effect of indigenously fabricated dental magnets on animal cell lines. MATERIALS AND METHODS: Neodymium-iron-boron (Nd-Fe-B) magnet was tested for cytotoxicity. The magnet was encased in a teflon cylinder. Magnets were placed in the well tissue-cultured plates together with a suspension containing NIH 3T3 mouse fibroblasts (5 × 105 cells/ml). After 3 days of incubation at 37°C, cell viability was determined by mean transit time (MTT) assay. Cells were subsequently dissolved in 100 µl dimethyl sulfoxide with gentle shaking for 2 h at room temperature followed by measurement of absorbance at 570 nm. Eight replicate wells were used at each point in each of four separate measurements. Measured absorbance values were directly used for calculating percent of viable cells remaining after the respective treatment. Data were analyzed statistically with significance level set at P < 0.05. RESULTS: The control group had highest absorbance reading for the MTT assay followed by test group. The lowest values were found with bare Nd-Fe-B magnets. One-way ANOVA test was performed for the data obtained. There was a statistical significant difference seen in the positive control (bare magnets, 44.96) and the test (teflon cased magnets, 96.90) group. CONCLUSION: More number of viable cells was visible in test group cells indicating that the indigenously fabricated dental magnet did not show any cytotoxicity.

A Comparison of the Change in Mandibular Condyle/Fossa Relationship with the Use of Anatomic Teeth and Semi-anatomic Teeth in Complete Denture Prosthesis.

The association between dental occlusion and mandibular condyle/fossa relation has long been debated and still remains one of the most controversial issues in Prosthodontics. The aim of the study was to evaluate the effect of two different tooth forms on the condyle/fossa relation recorded during jaw relation process. Twenty edentulous patients were selected with good neuromuscular control. For each patient two pairs of dentures were fabricated with anatomic teeth and semi-anatomic teeth. Condylar position was recorded using a digital volume tomography (DVT) following the process of jaw relation (following extra oral tracing). Subsequent laboratory remounting, the denture insertion was done and DVTs were taken again for both the dentures separately. Two methods were used to evaluate the condyle/fossa relation viz. (1) Zhang's method (2) Brewka's method. The obtained values were then subjected to statistical analysis. The statistical significance was set as at 0.05 %. The mandibular concentricity were analysed during the process of jaw relation and after the insertion of dentures with the two different tooth forms. Statistical analysis indicated that no statistically significant difference of the influence of different posterior tooth forms on the condyle/fossa relation recorded during jaw relation (p < 0.05). Thus within limitations of this study it was concluded that the condyle/fossa relation established during jaw relation does not change with the change in posterior tooth form used.

Magnet retained cheek plumper to enhance denture esthetics: case reports.

Handicap due to the loss of teeth in patients can be severe due to the impairment of masticatory function and facial disfigurement leading to negative psychological impact on the individual. To combat this, apart from the regular measures of positioning the teeth to obtain lip support, excellent denture esthetics can be achieved by providing additional support to the slumped tissues. This clinical report highlights a technique to provide support for sunken cheeks using detachable acrylic cheek plumpers, retained using iron-neodymium close-field magnets. The use of these magnets is a modification from the conventional technique of supporting the slumped tissues.

A finite element analysis for a comparative evaluation of stress with two commonly used esthetic posts.

OBJECTIVES: The objective of this study was to evaluate stress distribution in the dentin and alveolar bone created by load application on simulated endodontically treated teeth with two different esthetic posts. MATERIALS AND METHODS: A finite element model was made and elastic moduli and poissons ratio of all the materials fed to the software. For both the models, a 100N force was applied on the lingual surface of the tooth at an angle of 45°. Stress concentration and distribution were evaluated and noted down for both the posts. RESULTS: Finite element method revealed that Glass fibre post had homogenous distribution of stress whereas in zirconia post the stress was concentrated in the post. CONCLUSION: The present findings suggest that glass fibre post should be used in well-conserved radicular tooth structure and Zirconia post is indicated in weakened and grossly destructed tooth structure.

Use of a stud attachment to retain a silicone orbital prosthesis: a clinical report.

Orbital defects with total loss of eyelids and eyeball cannot be satisfactorily repaired by reconstructive surgery. Prosthetic replacement is the treatment of choice owing to its acceptable lifelike appearance. The use of semiprecision attachments in maxillofacial prostheses is limited to osseointegrated prostheses. Therefore, this article describes a conventional glasses frame technique, to retain the silicone orbital prosthesis using a Dalla Bona stud attachment.

Evaluation of understanding levels of Indian dental students' knowledge and perceptions regarding older adults.

Increasing numbers of older people and decreasing rates of edentulism highlight the importance of dental education that focuses on oral health and ageing. Our evaluation study was carried out to assess the Indian dental graduate's geriatric knowledge, as well as their awareness, of the bio-psychosocial factors that are potential barriers to geriatric oral health care. A total of 98 students were evaluated during their rotational clinical posting in the fifth year of the dental education programme. The results suggest that general attitudes need to be changed by the inclusion of geriatric dentistry in the dental curriculum. Exposure of students to didactic and clinical setting appears to be a critical element towards positive knowledge and attitude of the elderly.

Perceptions and preferences on denture marking in an Indian sample.

AIM: Denture marking is useful in institutional settings and post-mortem identification. Numerous markers have been developed, and their advantages and limitations assessed previously; however, patient perception to denture marking is paramount. We evaluated this in an Indian sample and also gauged their preference for different markers. MATERIALS AND METHODS: One-hundred and one edentulous patients seeking prosthodontic treatment in our institution were shown four denture markers (stainless steel matrix band, paper strip with name inscribed on it, patient photograph and optically readable laminated bar code) and asked whether they wanted similar markers in their dentures; patients were also asked to rank the markers based on preference and indicate their satisfaction with it. RESULTS: Approximately two-thirds of patients (65/101) were uninterested in getting their dentures marked; among the 36 who agreed, 10 preferred the stainless steel band followed by photographs (9), paper strip (6) and bar code (2); nine gave multiple responses and were excluded from analyses. Sixteen patients expressed dissatisfaction with the photographic marker and bar code, while this number reduced for the stainless steel band (13) and paper strip (10). CONCLUSIONS: The results are in contrast to European studies wherein the majority of patients agreed to denture marking, indicating patient background (e.g. education level) may affect perception to denture marking; amongst those who agreed to marking, most preferred, or were satisfied with, the stainless steel and paper strip markers over photographic marker and a complex method such as bar-coding, implying that simple methods harbouring basic patient information may suffice in the Indian context.

Use of an implant o-ring attachment for the tooth supported mandibular overdenture: a clinical report.

Retention of a mandibular denture can be achieved by an implant-retained or natural tooth-retained bar and stud attachment in the anterior segment of the mandible. The same design principles holds true for both implant-retained and tooth-retained methods of anchoring the bar and stud attachment. A simple and cost effective treatment for more complex implant overdenture is the concept of conventional tooth-retained overdentures. When few firm teeth still remain in a compromised dentition, preservation of these teeth for overdentures can improve retention and stability. The authors present a clinical report of a patient treated with a mandibular tooth-borne overdenture with bar and O-ring attachment. A splinted bar supported the prosthesis and an O-ring retained the denture.

Ocular prosthesis for a geriatric patient with customised iris: a report of two cases.

OBJECTIVE: An ocular prosthesis is given when trauma or disease may lead to enucleation or evisceration of the eye and the combined efforts of the ophthalmologists and the maxillofacial prosthetist can provide a cosmetically acceptable ocular prosthesis. METHODS: An ocular prosthesis is either pre-fabricated or custom-made. One of the important factors for achieving a cosmetic result is accurate colour matching of the iris with the contralateral iris. RESULTS: A knowledge of the anatomy of the eye facilitates hand painting of iris and sclera to produce a satisfactory result. CONCLUSION: The custom-made ocular prosthesis allows infinite variations during the fabrication.

Comparison of linear dimensional change, surface hardness and surface roughness of refractory model prepared from two different duplicating media.

The aim of this study was to evaluate and compare the linear dimensional change, surface hardness and surface roughness of the refractory casts poured against different duplicating media. Polyvinyl siloxane and Agar-agar were used for duplicating the stainless steel die. Sixty refractory models were prepared which were divided into two groups: I and II with 30 samples each respectively. Each group was subdivided into 3 subgroups with 10 samples each which were treated differently. All the specimens were measured for the linear dimensional change and surface hardness and the obtained data was statistically analyzed. Surface roughness was evaluated qualitatively taking SEM photomicrographs. Statistical analysis of linear dimensional change using one-way ANOVA showed statistically significant difference between subgroups of group I and non-significant difference between subgroups of group II. One-way ANOVA for Brinell hardness number showed statistically significant difference between the subgroups of group I & II. Student's 't' test results for linear dimensional change among different subgroups of group I & II showed significant difference between IA-IIA, IB-IIB, IC-IIC. Similarly 't'-test results for Brinell hardness number showed significant difference between subgroups IA-IIA, IB-IIB, and IC-IIC. Surface characteristics of the refractory casts poured against polyvinyl siloxane duplicating media were found to be better than the Agar media.

Effect of porcelain-firing cycles and surface finishing on the marginal discrepancy of titanium copings.

PURPOSE: The aim of the study was to evaluate the effect of simulated porcelain firing cycles and surface finishing on the marginal fit of commercially pure titanium (Cp Ti) copings. MATERIALS AND METHODS: A machined stainless steel die system with standard 0.5-mm copings was fabricated. Wax patterns were prepared by pouring the molten wax on a two-part stainless steel die. Thirty specimens were cast in Cp Ti. These were divided into three groups with ten specimens in each group. Group 1 was treated with conventional cold working and later oxidized. Group 2 specimens were oxidized initially and then cold worked. Group 3 was heat treated in its original investment and later treated as in group 1. All specimens were later subjected to sequential simulated porcelain firing cycles, that is, oxidation, bonder, opaque, body, and glaze firing. Following the completion of each firing cycle, marginal discrepancy was measured in µm using a traveling microscope. The obtained data were subjected to one-way analysis of variance (ANOVA) and Student's t-test. The statistical level of significance was set at 1%. RESULTS: The results showed that the mean and SD values (in µm) were 55 ± 2.6, 43 ± 3.0, and 68 ± 4.0 after oxidation for groups 1, 2, and 3, respectively. Mean and SD values (in µm) after glaze firing were 76 ± 3.9, 64 ± 4.1, and 89 ± 4.3 for groups 1, 2, and 3, respectively. The mean marginal opening was largest for group 3 specimens. One-way ANOVA showed the difference within the three groups was highly significant after oxidation (F-value 149.37 at p-value 0.0000) and glaze firing (F-value 82.43 at p-value 0.0000). CONCLUSIONS: (1) The Student's t-test values demonstrated that increased marginal openings of the specimens resulted after the sequential simulated porcelain firing cycles. (2) Marginal discrepancy values improved when the specimens were thermocycled prior to cold working.

Evaluation of shear bond strength of porcelain bonded to laser welded titanium surface and determination of mode of bond failure.

The aim of this study was to evaluate the shear bond strength of porcelain to laser welded titanium surface and to determine the mode of bond failure through scanning electron microscopy (SEM) and energy dispersive spectrophotometry (EDS). Forty five cast rectangular titanium specimens with the dimension of 10 mm x 8 mm x 1 mm were tested. Thirty specimens had a perforation of 2 mm diameter in the centre. These were randomly divided into Group A and B. The perforations in the Group B specimens were repaired by laser welding using Cp Grade II titanium wire. The remaining 15 specimens were taken as control group. All the test specimens were layered with low fusing porcelain and tested for shear bond strength. The debonded specimens were subjected to SEM and EDS. Data were analysed with 1-way analysis of variance and Student's t-test for comparison among the different groups. One-way analysis of variance (ANOVA) showed no statistically significant difference in shear bond strength values at a 5% level of confidence. The mean shear bond strength values for control group, Group A and B was 8.4 +/- 0.5 Mpa, 8.1 +/- 0.4 Mpa and 8.3 +/- 0.3 Mpa respectively. SEM/EDS analysis of the specimens showed mixed and cohesive type of bond failure. Within the limitations of the study laser welding did not have any effect on the shear bond strength of porcelain bonded to titanium.

Effect of anchorage on the accuracy of fit in removable partial denture framework.

PURPOSE: This study evaluated the effect of anchorage on the accuracy of fit in removable partial denture framework. MATERIALS AND METHODS: Twenty-four partially edentulous maxillary refractory casts were duplicated from a machine-milled metal cast. Twelve of these were included in the test group, which had the provision for anchorage in the refractory cast, and the remaining 12 were taken as control group, which did not have provision for anchorage. Identical wax patterns for the maxillary strap major connector were invested and cast in cobalt chromium alloy. The accuracy of fit of the cast partial major connector frameworks were measured at two selected points using a profile projector. The resultant data were analyzed using student's t-test and unpaired t-test. RESULTS: Student's t-test showed statistically significant improvement in the fit of the major connectors of the test group at point A (p= 0.0003) and P (p= 0.0074). Unpaired t-test was performed for the control and test group. The results of the unpaired t-test for the control group exhibited a greater gap discrepancy (0.44 +/- 0.20 mm) than for the test group at point A (0.16 +/- 0.10 mm). Similarly, the gap was more at Point P for the specimens in the control group (0.65 +/- 0.10 mm) than the test group (0.42 +/- 0.24 mm). CONCLUSION: Within the limitations of the study it is concluded that the accuracy of fit of the palatal major connector was significantly better in the test group than the control group, with 0.1% level of significance at point P. The accuracy was significantly improved in both groups at point A by 1% level of confidence.

Full mouth rehabilitation of severely attrited dentition. A case report.

Tooth wear and its management should be accurately diagnosed and planned. In some patients, long-term monitoring is essential before embarking on any irreversible, interventive treatment. Patients with excessive wear often require extensive restorative treatment. This article describes the case of one such patient who had severe tooth wear, resulting in reduced vertical dimension.

Usefulness of patient photograph as a marker for identifying denture-wearers in India.

AIM: Denture marking has been recommended for identifying the edentulous, both in day-to-day recognition when dentures are misplaced as well as in forensic scenarios. The purpose of this study was to test the use of patient photographs as a denture marker and to compare it with conventional marking systems as well as discussing its suitability in the Indian context. MATERIAL AND METHODS: A photograph of the patient was taken and compared with a metal matrix band and optically readable laminated bar code in terms of preparation, ease of incorporation into the denture, readability following denture fabrication and changes on exposure to high temperatures (200-1300 °C). RESULTS: The photograph and metal matrix band were easy to prepare and incorporate, but the bar code was less so; no differences, however, were appreciable with regard to readability of the three markers. Fire resistance of the photographic marker (280 °C) and bar code (200 °C) was considerably lower to that of the metal marker (1050 °C). CONCLUSIONS: The major advantage of the photographic marker is that identity is easily ascertained by lay persons with the unassisted eye (bar codes require a hand-held reading device); photographic markers are also relevant in the Indian context where one-third of the population is illiterate and diverse scripts are used across the country, making interpretation of written data challenging at times. This allows for photographic markers' routine use in residential and hospital set-ups. Although the photographic marker has low fire resistance, it may be useful in forensic contexts since dentures retained in the mouth are well-protected by the oro-facial tissues and may survive incineration.

A study on reproducing silicone shade guide for maxillofacial prostheses matching Indian skin color.

AIM: The value and success of a well-fitting and anatomically correct prosthesis are compromised if the color does not match the adjoining tissues. The use of powder colors to help develop a simplified silicone shade guide to aid in the fabrication of silicone facial prostheses for Indian patients has been described here. MATERIALS AND METHODS: Ten powder pigments were used to fabricate the silicone samples for three different subjects having light, medium and dark complexions who were separated into three groups depending on the value of their shades. Four-step wedge silicone samples with thickness variations of 1, 2, 4 and 6mm were fabricated. Visual assessment of the samples was done by four evaluators to check the agreement of color match. Data was statistically analyzed using kappa coefficients. RESULTS: The kappa values were found to be 0.09-0.44 for a light skin tone, -0.11 to 0.77 for medium skin and 0.44 to 0.85 for dark skin tones. This study showed that the samples of dark skin tone matched the skin tone well and showed a statistically good agreement. To further test the validity of these shade guides, facial silicone veneers were fabricated for three patients having light, medium and dark complexion. The color matching showed satisfactory results. CONCLUSION: The silicone veneers matched the skin color of all three patients. Hence, this shade guide will help clinicians to obtain a good intrinsic shade and minimize extrinsic coloration.