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At least 739 records · Page 41Linked to original sources
PubMedDate not supplied

Evaluation of a newly developed visual shade-matching apparatus.

PURPOSE: This study evaluated a newly developed visual shade-matching apparatus, Shademat Visual+, as well as the influence of tab arrangement, clinician gender, and years in practice on shade-matching quality. MATERIALS AND METHODS: A group of 129 color-normal evaluators-dental students and general dentists-matched the shade of four ceramometal crowns using the Vitapan Classical shade guide. Crowns were positioned onto the upper member of an artificial head and fastened to the headrest of the dental chair or Shademat Visual+. Shade tabs were arranged according to the manufacturer's suggestion or according to deltaE* in relation to the "lightest" tab and divided into groups (alternative arrangement). The evaluators matched the shade of four ceramometal crowns both in daylight and using the Shademat Visual+ artificial light source. The color coordinates were determined using digital image analysis. Based on deltaE* values, each shade-matching result was ranked from 1 (the worst match) to 16 (the best match) points. RESULTS: The evaluators achieved a better result in Shademat Visual+ trials than in daylight trials (13.2 points vs 12.4 points; P < .001). For the same ceramometal crown, 12.7 points were recorded in daylight trials with the manufacturer-suggested arrangement, and 13.7 were recorded with the alternative arrangement (P< .001). Corresponding values for Shademat Visual+ trials were 13.6 points and 14.6 points, respectively (P< .001). Female-male and student-dentist evaluator differences were not significant. CONCLUSION: The Shademat Visual+ apparatus enabled better shade-matching results than daylight. The alternative tab arrangement enabled better results than the manufacturer-suggested one. Gender and years in practice did not influence shade-matching quality.

Age Factors↗
PubMed2002

Relationship between the number of occlusal contacts and masticatory muscle activity in healthy young adults.

The electromyographic (EMG) potentials of left and right masseter and temporalis anterior muscles were recorded in 23 healthy young adults during: 1. a 3-second maximum voluntary clench (MVC) on cotton rolls positioned on the posterior teeth (standardized recording); and 2. a 3-second MVC in intercuspal position. EMG potentials recorded in intercuspal position were standardized as a percentage of the mean potentials of the standardized recording, and the EMG muscle activity was calculated. The number of occlusal contacts in intercuspal position was assessed by using eight microm thick shim stocks. Two groups of subjects with either 1. Less than ten occlusal contacts (11 subjects with "few contacts"); or 2. At least ten occlusal contacts (12 subjects with "many contacts") were selected. The MVC muscle activity in the "few contacts" group was significantly lower than that recorded in the "many contacts" group (p<0.005). In conclusion, the number of occlusal contacts and masticatory muscular function are significantly related, at least in young adults with a sound stomatognathic apparatus.

Adult↗
PubMed1994

Working time of synthetic elastomeric impression material.

This study will introduce a new method for measuring the working time of elastomeric impression materials, taking into account the perceived shortcomings of existing systems for evaluating these times. The working times of various commercially available polysulfide, addition reaction silicones and polyethers were determined at room temperature (20 degrees C), following storage in a refrigerator (6 degrees C), and at mouth temperature (35 degrees C). At room temperature, the polysulfides demonstrated the longest working times and the silicones the shortest. Both the polysulfides and the silicones had longer working times following storage at 6 degrees C for 24 hours. However, the polyethers were found to be unusable at this temperature. All the impression materials had shorter working times when placed into the testing apparatus, which had been heated to mouth temperature.

Dental Impression Materials↗
PubMed1995

Purification of nonamelogenin proteins from bovine secretory enamel.

The developing enamel matrix is composed of two groups of proteins that can be generally classified as amelogenins and nonamelogenins. The hydrophobic amelogenins represent the majority of the developing enamel matrix proteins, whereas nonamelogenins include the more hydrophilic enamelins, proteinases, and other minor protein components, which represent a small proportion of the matrix. This report describes the purification and partial amino acid sequences of two previously unknown proteins isolated from developing bovine enamel. These proteins were prepared by extracting bovine secretory stage enamel with low ionic strength buffer, followed by ammonium sulfate fractionation. The proteins were purified by ion-exchange, affinity, and reversed-phase chromatography. We propose to designate the proteins BEgp (a glycoprotein) and BEpa. A partial sequence was also obtained from a third protein (BEpb) which was nearly identical to BEpa. Antibodies were prepared to a synthetic peptide based on the N-terminal sequence of BEpa and subsequent immunoblots of various bovine tissues showed a major component of approximately 25 kDa specifically in enamel and ameloblasts. Little or no cross-reactivity of the antibody was found to bovine proteins extracted from heart, lung, kidney, liver, dental pulp, or bone. Similar analyses of both rat secretory stage and maturation stage enamel showed two bands of 28 kDa and 29 kDa. Immunohistochemical localization in rat incisors, showed specific staining of the enamel, secretory granules, and Golgi apparatus in ameloblasts. No sequence homology with known proteins could be demonstrated for BEgp or BEpa, suggesting that these components of developing enamel are novel tooth-specific proteins.

Amino Acid Sequence↗
PubMed1994

Clinical application of dental prosthesis with magnetic attachment to a patient with cerebral palsy.

Removable dental prosthesis with magnetic attachment was applied to a fifty-two-year old female with cerebral palsy. New magnetic attachments made of rare earth metal, a pair of Sm-Co magnets housed in a magnetic stainless steel keeper, were used as a safe and simple retention apparatus instead of the conventional cast metal or wire clasps for partial denture. The patient even with her severe physical disability could manipulate this denture without much difficulty.

Cerebral Palsy↗
PubMed2006

Cyclic fatigue in water of veneer-framework composites for all-ceramic dental bridges.

OBJECTIVES: Ceramic materials applied in dentistry may exhibit significant subcritical crack growth due to the severe cyclic loading in the aqueous environment encountered in the mouth during mastication. The authors report on the subcritical crack growth behavior of three dental restoration systems (Empress 2/IPS Eris, TZP/Cercon S and Inceram-Zirconia/Vita VM7) under cyclic loading in water, in order to establish guidelines for the use and design of long-lifetime all-ceramic posterior bridges. METHODS: Inert strength and lifetime tests under cyclic loading in an aqueous environment were performed in a mechanical bending apparatus and evaluated with Weibull statistics. RESULTS: Subcritical crack growth occurred predominantly in the outer veneer layer of the veneer-framework composites. The apatite-based veneer (IPS Eris) was more susceptible to subcritical crack propagation compared to the feldspathic glass veneers (Cercon S and Vita VM7). SIGNIFICANCE: Dental restoration systems containing apatite-based veneers and weak frameworks (Empress 2/IPS Eris) are not recommended for the fabrication of all-ceramic bridges in the molar region. Conversely, veneer-framework systems consisting of feldspathic glass veneers and tough zirconia-based frameworks (TZP/Cercon S and Inceram-Zirconia/Vita VM7) may exhibit lifetimes longer than 20 years if the bridge connector is properly designed.

Aluminum Oxide↗
PubMed1985

Dental occlusal wear and degenerative disease of the temporomandibular joint: a correlational study utilizing skeletal material from a contemporary population.

Forty crania and mandibles with intact dentition exceeding twenty-six teeth and bilaterally intact condyle-fossa apparatus were evaluated for attrition and degenerative joint disease. The skeletal specimens all represent a twentieth-century contemporary American population from the Atkinson Skull Collection at the University of the Pacific School of Dentistry. While 23.1% of this sample exhibited some degree of erosive osseous degenerative wear involving the condyle or articular fossa and 76.3% exhibited occlusal tooth wear, no significant correlation between the degree of attrition and the severity of degenerative joint disease could be documented.

Adult↗
PubMed1991

Measurement methods used for the determination of dimensional accuracy and stability of denture base materials.

The literature relating to methods of measurement of dimensional accuracy and stability of denture base materials is reviewed. The papers are presented chronologically together with information on the measurement technique used and the reported level of accuracy. Most authors utilized optical measuring apparatus, with the use of calipers being the second most popular method.

Dental Materials↗
PubMedDate not supplied

Immediate implant-supported oral rehabilitation using a photocurable plastic skull model and laser welding. A technical note on the screw-retained type: Part 1.

PURPOSE: This article describes a new procedure for immediate implant-supported oral rehabilitation using a photocurable resin skull model and a laser-welding apparatus. MATERIALS AND METHODS: Preoperatively, the framework was fabricated on a photocurable resin skull model produced from a CT scan and individually designed guide template. The implants were immediately placed using the guide template; laser welding connected the components of framework. RESULTS: Despite the custom-made prosthesis, the total treatment from implant placement to superstructure placement can be completed within only 1 day. CONCLUSION: This procedure for immediate implant-supported oral rehabilitation using a photocurable resin skull model and a laser-welding apparatus may be useful for any implant system and patient.

Dental Articulators↗