Comparison of dimensional accuracy of elastomeric impression materials using 3D laser scanner.

Background: The dimensional accuracy of elastomeric impression materials has been evaluated by different methods but their reliability is still questionable. The aim of this study was to evaluate the dimensional accuracy of elastomeric impression material using 3D laser scanner. Method: In the present study, a metal die with its custom tray were designed. Using this die and tray, 10 impressions each were made from addition silicone (Aquasil LV; Dentsply), condensation silicone (Speedex coltene, Whaledent) and polyether (3M; ESPE). All the impressions were poured with Type IV die stone and total of 30 die replicas were obtained. These were scanned with a Picza 3D laser scanner (LPX 600, Roland,California) and the difference between the stone model was calculated by determining its volumetric changes using CAD-CAM pero version 2.0. One way analysis of variance (ANOVA) was used to compare the groups, whereas significance of mean difference between the groups was done by Tukey HSD. Results: All the three groups showed mean decrease indicating a dimensional shrinkage from the master die. Mean percentage dimensional change in condensation silicone was maximum (-319.02 ±15.50) followed by polyether (-122.59 ± 0.64) and least in addition silicone (-23.83 ± 0.43). All the results were statistically significant (p<0.001). Conclusion: Picza 3D laser scanner can precisely measure the volumetric changes in all the three elastomeric impression materials.

A comparative study of masticatory performance in complete denture patients before and after application of soft liner.

BACKGROUND: To compare the masticatory performance in complete denture patients before and after application of soft liner and to assess the effect of aging of soft liner on masticatory performance at different intervals of time. METHODS: A total of 30 complete denture wearers between age of 64 and 80 years, were selected from both the sex (20 men, 10 women). This study evaluated the effect of before and after application of chair-side soft liner on masticatory performance of complete denture wearers by using raw carrots and roasted peanut as the test food. This study further evaluated the cushioning effect of chair-side soft liner material at the interval period of 1week, 4 weeks, 8 weeks, 12 weeks and 16 weeks. RESULTS: There were significant differences in masticatory performance without soft liner as compared to with soft liner at different intervals of time. The performance was found to be significantly higher for raw carrot as compared to roasted peanut (p < 0.001). For both the materials peak performance was recorded at 4th week. CONCLUSION: The use of soft liner helps in increasing the masticatory performance among complete denture wearers.

Obstructive Sleep Apnea and Neurocognitive Dysfunction in Edentulous Patients.

PURPOSE: To record the incidence of cognitive dysfunction in edentulous patients suffering from obstructive sleep apnea (OSA) and establish a plausible hypothesis to explain the correlation of cognitive dysfunction and OSA. MATERIALS AND METHODS: In this study, 315 edentulous patients (aged 60 to 65 years) visiting the outpatient department at Saraswati Dental College, Lucknow were recruited from January 2013 to October 2015. Prosthodontic Diagnostic Index (PDI) classification was used to assess the intraoral condition to relate it with the span of edentulousness. The BERLIN questionnaire and Epworth Sleepiness Scales were used to diagnose sleep-disordered breathing, following which the patients were put through all-night polysomnography. The apnea-hypopnea index (AHI) scores were derived. Mild and moderate OSA patients were classified into mild, moderate, and severe cognitive dysfunction based on SGRQ-C and SCD. Data were tabulated according to a new classification (Cognitive Dysfunction of Dental Sleep Medicine Patients [CDDSMP] Classification) designed specifically for this study. Data were analyzed using SPSS v15.0. Scores were tabulated as mean ± SD and median [IQR] values. Change from baseline was analyzed using Wilcoxon signed rank test. RESULTS: Mean scores at different time intervals were 3.03 ± 1.76 (3 months), 2.98 ± 1.80 (6 months), and 2.81 ± 1.84 (9 months). The median [IQR] values of scores at all time intervals except 9 months were 3 [1 to 5]. At 9 months, median [IQR] was 2 [1 to 5]. A significant change in scores was observed in the 3-month interval (p ≤ 0.001). CONCLUSIONS: The severity of OSA and neurocognitive dysfunction could be directly related to the PDI classification and the span of edentulousness of the patient and modified mandibular advancement device treatment significantly improved the patients' condition, which was reflective from 3 months post-intervention itself.

An innovative approach to the prosthodontic management of Class III mandibular defect.

Class III mandibular resection due to surgical treatment of jaw tumor produces a discontinuity in the mandible which is severely incapacitating to the patient. It leads to a deviation and rotation of the mandible which depends on the amount of tissues resected the manner of surgical site closure, loss of proprioceptive sense of occlusion, the presence, and condition of teeth, and the time of initiation of prosthodontic therapy. These put together makes the task of prosthodontic rehabilitation quite arduous. Guide flange prosthesis is a comparatively simple and cost-effective method of restoring the esthetics and function to an acceptable level. This clinical report describes an innovative and simplified approach to impression making (sectional two-step impression) to minimize trauma to the underlying and circumoral fragile tissues postsurgery, and to the fabrication of buccal guide flange (wrought wire supported and reinforced guide flange) for prosthetic rehabilitation of a patient with Class III mandibular resection.

Effect of Different Ferrule Length on Fracture Resistance of Endodontically Treated Teeth: An In vitro Study.

INTRODUCTION: A ferrule has been described as a key element of tooth preparation when using a post and a core. It is a vertical band of tooth structure at the gingival aspect of crown preparation. It lessens the stress transmission to the root which is due to forces from posts or bending during seating of the post. The incorporation of a ferrule can help to withstand the forces of occlusion, preserve the hermetic seal of the luting cement, and minimize the concentration of stresses at the junction of post and core. AIM: To evaluate and compare the effect of ferrule length on fracture resistance of endodontically treated mandibular premolar teeth, restored with prefabricated glass fiber post luted with resin cement, composite core and a full coverage metal crown. MATERIALS AND METHODS: Forty freshly extracted mandibular premolars were treated endodontically. They were randomly divided into four groups according to their ferrule height: 3 mm, 2 mm, 1 mm and 0 mm (no ferrule). All specimens were restored with prefabricated glass fibre posts (Reforpost, Angelus) and composite resin (Filtek™ Z250XT). Standardized preparation was done on each specimen to receive a cast metal crown. The specimens were thermocycled and compressive static load at a crosshead speed of 1 mm/min was applied at an angle of 30° on lingual incline of buccal cusp of the crown until failure occurred. The load (N) at failure and mode of failure were recorded. Statistical analysis was performed with Kruskal Wallis test. RESULT: Fracture resistance values among the groups was found to be statistically significant (p<0.001). The 3 mm ferrule group had significantly higher failure load (971.99±133.07) compared to 2 mm (848.84±109.60), 1 mm (714.64±133.89) and 0 mm ferrule groups (529.36±119.95). More favourable failure modes were observed in almost all groups. CONCLUSION: The results of this study showed that fracture resistance of endodontically treated teeth increases as ferrule length increases.

Treatment Outcome with Delayed Maxillary Obturator Prosthesis: Case Series of Four Patients.

A series of four patients is presented to indicate the possibility of success with delayed prosthodontic rehabilitation of acquired maxillary defects. Four patients with a history of hemi-maxillectomy in the past 3 to 5 years were rehabilitated with definitive obturator prostheses. All had partial maxillectomy on the right side. Because of delayed referral to the prosthodontic facility, immediate surgical and interim obturation was not planned. Definitive obturator prostheses were fabricated following the necessary steps and delivered to the patients. Prosthesis function was subsequently reassessed in these patients every fortnight for the first 3 months then once every quarter for the next 3 years, followed by once a year. Individual patient responses were evaluated at regular intervals. Components of prosthesis function assessed were esthetics, speech, mastication, and salivary control, all of which were restored to satisfactory levels by the definitive obturators. Thus, optimal restoration of esthetics and function is achievable despite a time lag in prosthodontic therapy after surgery.

Effect of PFM Firing Cycles on the Mechanical Properties, Phase Composition, and Microstructure of Nickel-Chromium Alloy.

PURPOSE: The purpose of this study was to compare the mechanical properties of beryllium-free nickel-chromium (Ni-Cr) dental casting alloy before and after each porcelain firing cycle (once fired, twice fired, and thrice fired) and to relate these properties to the microstructural changes and changes in X-ray diffraction patterns of Ni-Cr alloy that occur after each porcelain firing cycle. MATERIAL AND METHODS: Forty tensile bar specimens and 20 disc-shaped specimens of Ni-Cr alloy were prepared. These specimens were divided into four groups. The first group was not heat treated and tested in the as-cast condition, thus serving as control group. The second, third, and fourth groups were fired once, twice, and thrice, respectively. Tensile bar specimens were loaded to failure in tension using a universal testing machine. Values of ultimate tensile strength, 0.1% yield strength, and percentage elongations were determined. Microstructural study and hardness testing were done using an optical microscope and digital Vickers hardness tester, respectively, on disc-shaped specimens. Disc-shaped specimens were again used to obtain the X-ray diffraction patterns by using diffractometer Bruker D8 focus. Statistical comparisons of the mechanical properties and hardness of the alloy were made with ANOVA. Intergroup comparisons of the data in the as-cast and fired specimens were analyzed by applying Tukey's HSD multiple comparison tests. RESULTS: Before porcelain firing, the alloy exhibited higher ultimate tensile strength (548 MPa), 0.1% yield strength (327 MPa), hardness (192 HV), and lower elongation values (18%). After each firing cycle, there was a significant (p < 0.001) decrease in ultimate strength (464 MPa for three times fired specimens), 0.1% yield strength (284 MPa for three times fired group), and hardness (164 HV for three times fired group) and significant (p < 0.001) increase in elongation value (28% for three times fired group) of Ni-Cr alloy. The microstructure of the control group specimen exhibited heterogeneous microstructure, and after each firing, microstructure of the alloy was gradually homogenized by formation of grain boundaries at the interdendritic interfaces. X-ray diffraction pattern shows that the alloy exhibited four strong diffraction peaks within the range of 2θ = 40° to 100°. After a third firing, intensity of these planes increased. CONCLUSIONS: Results of this study confirmed that nickel-based alloys become weaker after each firing process. After firing treatment, the microstructure of alloys showed decreased dendritic structure (i.e., homogenization, which was responsible for decrease in strength and an increase in ductility of the alloy); however, this decreased strength and hardness of Ni-Cr alloy after heat treatment was still superior to those of the most noble metal alloys used in dentistry. X-ray diffraction study showed that firing process led to relieving of stresses, which ultimately resulted in stability in the crystal structure of alloy.

Treatment outcome with guiding flange prosthesis in hemimandibulectomy patients: Case series of three patients.

There are various indications that may necessitate partial or complete resection of the mandible, from trauma to congenital deformities. However, the most prevalent indication that requires surgical resection of the mandible along with the involved adjacent oral structures is the presence of a locally aggressive neoplastic growth. The resultant continuity defect leads to an alteration in the range and direction of mandibular movement, impedes clear articulation of syllables and cosmetic disfigurement. The role of a prosthodontist is paramount in bringing about the restoration of the esthetic and functional dysfunction. This article discusses a series of hemimandibulectomy cases wherein mandibular deviation was successfully corrected using guide-flange prosthesis.

Full mouth rehabilitation of hypomaturation type amelogenesis imperfecta: A clinical report.

PROBLEM CONSIDERED: This clinical report describes the prosthodontic treatment of an 18-year-old female diagnosed with amelogenesis imperfecta. MATERIALS AND METHOD: The specific objectives of the treatment were to restore esthetics and masticatory function. Metal-ceramic fixed partial dentures were fabricated at the existing vertical dimension of occlusion utilizing the PMS occlusal scheme. RESULTS: Clinical examination of the patient 12 months after treatment revealed no evidence of disease or degeneration of the restored teeth. CONCLUSION: The patient's esthetic and functional expectations were satisfied.