Finite element analysis of the effect of framework materials at the bone-implant interface in the all-on-four implant system.

BACKGROUND: The "All-on-four" concept for treatment of edentulous arches incorporates four implants that are placed in between mental foramina in the mandible. The prosthetic framework is an important parameter in stress/strain concentration at the implants, prosthesis, and the underlying bone. Materials such as titanium, zirconia, and carbon fibers have been used for fabrication of framework in the past. The aim of this study was to analyze the effect of framework materials in the "All-on-four" implant system. MATERIALS AND METHODS: Finite element three-dimensional (3D) model of edentulous mandible was simulated using a computerized tomographic scan data of an edentulous patient. Threaded implants were replicated along with the abutments using 3D modeling software and the framework was designed and simulated using material properties of titanium, zirconia, and polyetheretherketone (PEEK). Axial and nonaxial load of 200 N was applied at the abutment region of right distal implants. The computer-generated numerical values were tabulated and analysed by ANSYS software. RESULTS: Principal strain, von Mises stress and micromotion were assessed in the peri-implant bone region to evaluate its stress condition. Zirconia framework showed the least stress/strain values at axial and oblique loading. Maximum strain values were seen at the PEEK framework material. Zirconia framework in all models showed the least micromotion/displacement. CONCLUSION: The stress distribution pattern at implant-bone interface was influenced by the framework material used. The framework material, loading site, and direction of forces influenced the stresses and displacement at the bone-implant interface.

Assessment of Flexural Strength and Cytotoxicity of Heat Cure Denture Base Resin Modified with Titanium Dioxide Nanoparticles: An In Vitro Study.

AIMS: To assess the effect of titanium dioxide nanoparticles (NPs) on flexural strength and cytotoxicity of heat-cured polymethyl methacrylate (PMMA) resins. METHODOLOGY: Sixty-four rectangular and 12 circular specimens were fabricated from metal dies to test flexural strength and cytotoxicity, respectively. The rectangular specimens were grouped into four (16 specimens each)-control group (Group 1), Group 2 with 3% TiO2, Group 3 with 5% TiO2, and Group 4 with 7% TiO2. They were tested for flexural strength using universal testing machine. The circular specimens were grouped into two (six specimens each)-control group and the test group which included the group which showed a highest flexural strength. They were tested for cytotoxicity using MTT assay. The analysis of variance (ANOVA) test was used to analyze the mean flexural strength of each group and Tukey's post hoc test, for pairwise group comparison (p <0.05). An independent sample t-test was used to analyze the cytotoxicity between the groups (p <0.05). RESULT: The study showed that there was a significant decrease in the flexural strength from the control group (mean: 298.95), which reduced as the concentration of TiO2 increased. However, the toxicity reduced considerably from 24 hours to 7 days in both groups while the test group showed better cell viability (%) than the control group. CONCLUSION: The flexural strength of heat cure acrylic resin (modified and unmodified) was much higher than the recommended flexural strength for these resins. On adding TiO2 NPs, flexural strength decreased when compared to the control group. However, with 3% TiO2 NPs, there was no significant decrease in flexural strength as compared to conventional resins. TiO2 NP-modified heat cure acrylic resin showed less toxicity on day 1 and even lesser toxicity after 7 days indicating that it is biocompatible. CLINICAL SIGNIFICANCE: TiO2 NPs incorporated at 3% concentration in denture base resin had less cytotoxicity and adequate flexural strength, to be used as a promising alternative to conventional denture base resin.

Interproximal Papilla Volumization Using Vestibular Incision Subperiosteal Tunneling Access Technique in Esthetic Rehabilitation.

An accurate diagnostic and interdisciplinary approach is essential for obtaining suitable, conservative, and predictable results in areas with high esthetic demand. Patients reporting with an improper prosthesis that has a black triangle pose a challenge for soft-tissue esthetic rehabilitation. Re-restoration of such cases with conventional fixed prosthesis would be undesirable due to imbalance in pink and white esthetics. This case report describes an interdisciplinary approach to maintain the existing midline diastema and correction of black triangle in the interproximal area between abutment and pontic in the esthetic zone. Minimally invasive vestibular incision subperiosteal tunneling access technique with connective tissue graft was planned for reconstructing the interdental papilla, followed by prosthetic rehabilitation of edentulous site with fixed partial denture using loop connector design to maintain the midline diastema. Postoperative result showed a comprehensive, pink and white rehabilitation to meet the patient's esthetic demand.

A comparison between visual, digital photography and polarizing filter photography for shade selection.

AIM: There is an increased awareness for aesthetically pleasing restorations among patients in current practice. Due to variability in the natural tooth colour, shade selection becomes an intricate procedure. The aim of this study is to determine which of the three named methods is more accurate for shade selection in aesthetic dentistry. MATERIALS AND METHODS: Two VITAPAN classical shade guides were used for this study. Nine shades were selected from the first shade guide (A1, A2, A3.5, B1, B2, B3, C1, C2, C3) and the number was concealed. Ten selected participants were asked to identify each concealed shade with the second shade guide. Canon 5D camera with ISO 200, shutter speed 1/100 sec, F22 was used for capturing images of the second shade guide. Photoshop CS3 Software was used for developing the digital shade guide. The participants were asked to match the shades from the first shade guide with the prepared digital shade guide. The third photographic shade guide was prepared using a polarised filter on the Canon 5D camera with the same settings. The participants were asked to match shades with the prepared photographic shade guide. RESULTS: Total observations made during the study were 270. Cross table statistical analysis (Chi-square test) done using SPSS 20.0 showed statistically significant difference between conventional and digital photography (P = 0.049). Analysis between digital photography and polarizing filter photography did not reveal a significant association (P = 0.181). CONCLUSION: Digital photographic method was most accurate among the three shade selection methods. It can be used to obtain aesthetic results.

A Study to Determine the Accuracy of Various Clinical Techniques of Ridge Mapping before Implant Fixture Placement.

AIM: The most important parameter to assess prior to implant fixture placement is the available bone width. Radiographic techniques have been found to be inadequate in providing this valuable information, unlike clinical techniques. The purpose of the present study was to determine the accuracy of various clinical techniques of ridge mapping before implant fixture placement. MATERIALS AND METHODS: Ten patients with at least two missing teeth adjacent to each other were selected for the study. Direct and indirect techniques of ridge mapping were carried out to assess the available bone width. RESULTS: The data obtained were statistically analyzed using ANOVA and Tukey's Post Hoc analysis. The results indicate that there is no significant difference between direct and indirect technique of ridge mapping. CONCLUSION: Either direct or indirect technique of ridge mapping can be used to assess the width of available bone before implant fixture placement. CLINICAL SIGNIFICANCE: Clinical techniques of ridge mapping are handy and can be carried out chairside with ease and less cost and no radiation exposure. Indirect techniques of ridge mapping provide adequate and reliable data regarding bone width just like direct technique. In the absence of a bone mapping caliper, this technique can be used as a diagnostic procedure before implant placement. And during the indirect technique, any material can be utilized with equal efficacy for the fabrication of the guides.

Characterization of Herbal Antifungal Agent, Origanum vulgare against Oral Candida spp. Isolated from Patients with Candida-Associated Denture Stomatitis: An In vitro Study.

BACKGROUND: Candida Associated Denture Stomatitis is the prevalent fungal pathosis in denture wearers, especially in immunocompromized patients. Existing antifungal agents are ineffective since the Candida species become resistant and also, they become toxic. Origanum vulgare is a herbal plant with high anti-fungal activity against Candida of blood and urine origin. However, it has never been explored against Candida from oral cavity. MATERIALS & METHODOLOGY: Dry leaves of the plant were purchased and authenticated. Oil extraction was done using Hydro-distillation method. Clinical isolates of Candida from denture wearers was speciated using CHROMagar. Well Diffusion test was used to confirm the antifungal activity. Hydro-distillation & Maceration methods of extraction were compared. MIC/MFC was determined using CSLI guidelines. Infra-Red Spectroscopy was used to identify the active functional group. RESULTS: O.vulgare showed 30±3mm of zone of inhibition as against 19mm for fluconazole. The suitable extraction method was Hydro-distillation. MIC & MFC were found to be 0.024% and 0.097% respectively which was much lesser than for fluconazole (0.25%). The active functional group had chemically similar structure as Carvacrol, usually found in antifungal herbs. CONCLUSION: within the limitations of the study, it was concluded that (a)O.vulgare is anticandidal for clinical isolates of oral Candida, (b) Hydro-distillation is an effective method as compared to Maceration (c) MIC & MFC are much lower than that of fluconazole (d) the major functional group was structurally similar to Carvacrol.

A Comprehensive Review on the Errors That occur during Ideal Teeth Arrangement for Complete Denture Prosthesis.

AIM: The aim of this article is to present a comprehensive review and a classification system on the various errors that occur during the ideal arrangement of artificial teeth for complete denture prosthesis. MATERIALS AND METHODS: Assessment of various classification systems presented for errors in artificial tooth arrangement and identifying the lacunae in each system. RESULTS: A comprehensive review and a classification system on the various errors that occur during the ideal arrangement of artificial teeth for complete denture prosthesis have been presented. CONCLUSION: This classification system is aimed toward dental students and dental practitioners to aid in the arrangement of artificial teeth for complete denture prosthesis. CLINICAL SIGNIFICANCE: The proposed classification system helps the operator to identify the various errors which may occur during the arrangement of artificial teeth for complete denture prosthesis. It also aids in providing a detailed insight into the role played by artificial teeth in restoring the form and function of completely edentulous patients.

Preliminary impression techniques for microstomia patients.

The Prosthetic rehabilitation of microstomia patients presents difficulties at all the stages. The difficulty starts with the preliminary impression making. This is due to the tongue rigidity and the decreased oral opening. A maximum oral opening which is smaller than the size of the tray can make prosthetic treatment challenging. Due to the restricted mouth opening, insertion and removal of the impression trays is extremely cumbersome and various modifications of the trays have been used in the past. Among these are the flexible trays and the sectional trays used with different modes of reassembling the segments extra orally after the impression is made. This article reviews the literature published from 1971 to 2015 concerning preliminary impression techniques used in making impressions for patients with microstomia based on various tray designs. An electronic search was performed across three databases (PubMed, Science Direct and Google Scolar) for relevant citations. The keywords/combinations used for the search were microstomia, limited/constricted/restricted mouth opening/oral access, trismus, sectional trays, impressions and prosthetic/prosthodontic rehabilitation. The search was limited to papers written in English which resulted in a total of 45 related articles of which 17 articles were included for discussion of this review.

Preliminary impressions in microstomia patients: an innovative technique.

Microstomia has been defined as an abnormally small oral orifice associated with various etiopathologic factors. Management of these patients poses extreme difficulties in every procedure during prosthesis fabrication. Restricted mouth opening of the patient makes the insertion and the removal of the tray extremely difficult. So sectioning of the existing stock tray is necessary, so that the trays can be inserted and removed in sections. The main problem encountered during this procedure is the reorientation of the tray back in position. This article presents an innovative technique for the easy handling of the sectioned stock impression trays.

Role of colors in prosthodontics: application of color science in restorative dentistry.

Shade selection procedure depends on various factors including translucency, contour and surface texture. Tooth shade selection using a conventional means involves a high degree of subjectivity. Traditional shade guides are available that use several methods for quantifying shade. Technology-based systems provide with an advantage of natural looking restorations. They include RGB devices, colorimeters, spectrophotometers. The impact of the color science can be seen on various restorative materials ranging from ceramics to maxillofacial prosthetic materials.

Inner canthal distance and golden proportion as predictors of maxillary central incisor width in south Indian population.

OBJECTIVES: Even though the constant relation of golden proportion and inner canthal distance (ICD) with the width of the maxillary central incisor (CIW) has been found in European population, it may not be applied to Indian population as we differ from Europeans racially and genetically. Hence, this study was carried out with the objectives of determining if these parameters are applicable to our population also. MATERIALS AND METHODS: Three hundred south Indian subjects between 18 and 26 years of age, free from facial and dental deformities were examined. Inner canthus of each eye was used as soft tissue landmark. The maxillary central incisors were measured at the contact point area with the help of digital vernier caliper. The CIW was also calculated using golden proportion ratio to obtain the calculated central incisor width. A comparison was made with measured width. Statistical analyses were done to identify any significant difference using "Z" tests. Pearson's Correlation Coefficient test was used to evaluate the measured and the calculated width of the central incisor. RESULTS: ICD and the width of two maxillary incisors were in golden proportion in south Indian population. Also, ICD when multiplied by a decreasing function value of the golden proportion and divided by 2 is a reliable predictor of determining CIW. CONCLUSION: As in the European population, the ICD and the golden proportion are reliable predictors for determining the width of the maxillary central incisors in the south Indian population also.

In vivo evaluation of crestal bone heights following implant placement with 'flapless' and 'with-flap' techniques in sites of immediately loaded implants.

PURPOSE: To evaluate and compare the changes in crestal bone height around implants placed with flapless surgery and with-flap surgery. MATERIALS AND METHODS: Ten implants were placed in six patients--five using flapless and five using with-flap techniques. Single-piece root-form implants and a one-stage approach with immediate nonfunctional loading protocol were used. The change in heights of crestal bone was measured on standardized digital periapical radiographs taken at 0, 1, and 3 months. RESULTS: On mesial side, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was significantly lower than with-flap method [0.01-0.06 mm for flapless and 0.13-0.40 mm for with-flap ( P = 0.01)]. On the distal side, the mean change from months 0-1, months 1-3, and months 0-3 for flapless method was significantly lower than with-flap method [0.02-0.05 mm for flapless and 0.09-0.30 mm for with-flap ( P = 0.01)]. CONCLUSIONS: During the three-month period, reduction of crestal bone height around the implants placed with flapless surgery (0.06 mm) was not statistically significant, while the reduction of crestal bone height around the implants placed using with-flap surgery (0.4 mm) was statistically significant. Comparitively, flapless approach showed lesser crestal bone height reduction, which was statistically significant.