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At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Influence of framework design on fracture strength of mandibular anterior all-ceramic resin-bonded fixed partial dentures.

PURPOSE: The purpose of this in vitro study was to evaluate the influence of the framework design on the fracture strength of all-ceramic resin-bonded fixed partial dentures (RBFPD) in the mandibular incisor region. MATERIALS AND METHODS: Twenty-four aluminum oxide ceramic frameworks were copy milled with the Celay system, glass infiltrated, and veneered with feldspathic porcelain to replace a mandibular incisor. Forty-eight extracted human incisors were used as abutments by embedding them in a polyester resin. The master casts were fabricated according to a typical clinical case. The sandblasted restorations were bonded to the acid-etched abutment teeth with a composite resin. Twelve RBFPDs had a conventional two-retainer design, and 12 had a cantilevered single-retainer design. Subgroups of eight specimens were subjected to a quasistatic load in the direction of the long axis of the abutment teeth in a universal testing machine. Additional subgroups of four specimens were subjected under 0 degrees to dynamic loading of 25 N in a dual-axis chewing simulator. RESULTS: The mean fracture strengths under quasistatic loading were 313 N (SD 42) for the two-retainer design and 291 N (SD 100) for the single-retainer design. The mean cycles sustained by specimens subjected to dynamic loading at 25 N were 50,081 (SD 42,705) for the two-retainer design and 297,099 (SD 508,439) for the single-retainer design. There was no statistically significant influence of the framework design on the fracture strength of the restorations under quasistatic or dynamic loading. CONCLUSION: The clinical application of cantilevered all-ceramic RBFPDs in the mandible may be an alternative to all-ceramic RBFPDs with two retainers.

Acid Etching, Dental↗
PubMed1991

Estimation of the mechanical lifetime of dental restorations: method and preliminary results.

To assess the clinical performance of restorative materials with respect to mechanical failure, the shape of the restoration, the strength and fatigue properties and the loading history are important. This study deals with the feasibility of a method to estimate the mechanical lifetime of dental restorations. The method takes into account that the mechanical lifetime is a stochastic quantity determined by shape, strength and fatigue properties and by the cyclic nature of the mastication forces. The general outline of the method is described and the necessary experimental data are discussed. Preliminary estimates of the lifetime of a composite and an amalgam restoration are made. The method is found to be feasible and the estimated lifetimes of the restoration are of the same order of magnitude as found clinically.

Bicuspid↗
PubMed1992

Chewing pressure vs. wear of composites and opposing enamel cusps.

The effects of various chewing pressures on the wear of composites and enamel were assessed in vitro. Standardized composite discs (8 mm in diameter, 2 mm in height) were made of a fine-particle hybrid (FPH), a coarse-particle hybrid (CPH), and a homogeneous microfilled composite (HMC). The composite specimens were chemically degraded by immersion in 75% ethanol for 24 h, brushed for 30 min, and then thermocycled 300 times (5-55-5 degrees C) while being occlusally loaded 120,000 times at 1.7 Hz, with chewing forces of 25, 50, 75, and 100 N. Standardized human enamel cusps with a uniform contact area of 0.384 mm2 served as antagonists in the chewing machine. Wear of the composites and enamel cusps, their combined wear, and the increase of the enamel contact surfaces were quantified. An increase in chewing pressure significantly enhanced the wear of both composite and enamel in all groups except for the antagonists opposing a HMC. The FPH was most wear-resistant to in vitro chewing pressures in the range of 6.58 to 19.74 MN/m2, the CPH at 26.32 MN/m2, while the HMC was the most enamel-friendly of the three composites tested. The FPH composite had the least disintegration in the occlusal contact area. The ranking of the composites generally varied at the different chewing pressures with respect to the three types of quantified wear--that is, composite wear, enamel wear, and total wear.

Acrylic Resins↗
PubMedDate not supplied

Two-body wear of dental composites under different loads.

PURPOSE: Although dental composites are excellent for restoring the appearance of natural tooth tissues, their relatively poor resistance to wear, especially in approximal and occlusal contact areas, is still a major source of concern. The aim of this research was to study a basic wear mechanism, under 2-body wear conditions, that may be integrated into our understanding of the in vitro and in vivo wear behavior of dental composites. MATERIALS AND METHODS: An in vitro 2-body wear test was conducted on 2 selected ultrafine compact-filled dental composites under different magnitudes of sinusoidal cyclic load. The wear surfaces and cross sections of the wear layers were assessed using scanning electron microscopy (SEM) to explore the nature of the wear pattern of the dental composites under cyclic loading conditions. RESULTS: The wear losses of both composites increased with load. SEM analysis of wear surfaces and subsurface sections indicated that the composites tested displayed different wear mechanisms from low to high loads. An explanation for the wear pattern is proposed based on the observed wear behavior. CONCLUSION: The in vitro wear pattern of the ultrafine compact-filled dental composites tested is closely related to the applied load. Although the wear loss increased in a roughly linear relationship with applied load, the underlying wear mechanism involved may experience a significant change from low to high load conditions during wear.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1993

Wear rates of artificial denture teeth opposed by natural dentition.

The wear rate of polymeric or composite-based artificial denture teeth on fixed, removable and implant prostheses is important in the maintenance of cuspal form, masticatory efficiency and occlusal stability. A servo-hydraulic based artificial mouth in which an occlusion was established between artificial denture teeth, and the palatal cusp of a human maxillary third molar was established and used to assess the wear resistance of 5 artificial denture tooth materials. Volumetric wear was determined for Dentsply Trublend SLM, Dentsply IPN, Vita Vitapan, Ivoclar Orthotyp and Ivoclar Orthosit denture teeth. Scanning electron microscopy was also done to assess the textural character of the wear facets of each denture tooth sample. The lowest volume loss was observed for Trublend SLM followed by IPN, Orthotyp, Vitapan and Orthosit. Textural assessment of the materials was consistent with the objective wear data.

Acrylic Resins↗
PubMed1995

Interocclusal splint designed to reduce tenderness in lateral pterygoid and other muscles of mastication.

When a patient has discomfort in the muscles of mastication, a palpation test of the lateral pterygoid muscles is positive, and a stress test is positive, the dental occlusion may be a partial cause. The resin splint described here is designed to permit interocclusal contact exclusively at the center of the arches. This device has been shown to reduce tenderness in the lateral pterygoid and other muscles of mastication quickly, usually in 5 to 10 minutes. The splint and its advantages and disadvantages are described.

Contraindications↗
PubMed1983

The effect of mastication on marginal adaptation of composite restorations in vivo.

The marginal adaptation of composite restorations placed in vivo in acid-etched cavities in teeth with and without antagonists was compared. The results showed that functional mastication has a major influence on the marginal adaptation of composite restorations in the oral environment and must therefore be considered in the planning of future leakage experiments.

Acid Etching, Dental↗
PubMed2003

Description of a photoelastic coating technique to describe surface strain of a dog skull loaded in vitro.

There are several methods of determining strain in the facial skeleton on loading in vitro. This article describes an alternative photoelastic coating technique adapted from the commonly accepted method used by engineers to study surface strains in objects. In applying this method to the stomatognathic system, because the masticatory apparatus is loaded by muscular contraction an opposite reaction load should be distributed throughout the skeletal structure. This load distribution should slightly deform the bones to which the muscles of mastication are attached. An understanding of the resulting strain generated in the facial skeleton is important because strain distribution on loading reflects how the loads applied during mastication are partially dissipated. Preliminary descriptive results are presented, suggesting that anatomic structures influence the distribution of strain on loading. The technique described should allow in vitro investigation of the mechanical environment into which osseointegrated implants are placed and may aid in understanding their behavior.

Animals↗
PubMed2003

[Retrospective analysis of 30 cases of mandibular ameloblastoma operated in the Ivory coast from 1992 to 2000].

OBJECTIVE: We analyzed a retrospective series of 30 cases of ameloblastoma operated in the Ivory coast from 1992 to 2000. PATIENTS AND METHODS: The following techniques were used--temporary reconstructions via the endobuccal approach using a Peri prothesis in 27 cases and a resin coated Peri prosthesis in one;-- definitive reconstructions using iliac bone grafts in 3 cases and rib grafts in 14. These reconstructions were performed in a second operation via a cutaneous approach to replace the Peri prosthesis. Thirteen patients were lost to follow-up for this second phase. Mean follow-up ranged from 6 months to 13 months (mean 9.9 months). RESULTS: Satisfactory outcome was acchevied when mouth opening was greater than 10 mm and patients with an acceptable cosmetic result no longer complained of mastication or phonation problems. There were four postoperative infections after bone graft reconstruction (two of them were immediate reconstruction). The resin coated Peri prosthesis led to a skin ulceration. DISCUSSION: This study demonstrated the interest of mandibular reconstruction in undermedicalized countries where indications are dominated by reconstruction after resection for ameloblastoma. The large number of patients lost to follow-up before the second stage bone grafts points out the need for immediate reconstruction using autologous bone. Further study in a larger series would be needed to determine the cause of failure after immediate reconstruction.

Adolescent↗
PubMed1997

The effect of timing of archwire placement on in vivo bond failure.

At the commencement of fixed appliance therapy the operator has the choice of either placing bands, brackets, and archwires at one visit, and hence loading the brackets within an hour of initial placement, or placing the brackets and separators at one visit, and the bands and archwires at a subsequent visit. In the case of the latter, the brackets will only be loaded intermittently during the intervening period, for example during mastication. The present study investigated the effect of loading bonded brackets for 2 weeks prior to measuring shear debonding force in vitro, and compared the results with in vivo bond failure rates for two groups of patients whose brackets were loaded by the archwire either immediately after bonding, or not less than 1 week later. Shear testing and survival analysis indicated in vitro loading prior to testing had no significant effect on the shear debonding force. When the in vivo data were studied there was no significant difference in the rate of bond failure between those patients whose archwires were placed at the time of fitting the appliance, and those whose archwires were placed no less then 1 week after bracket placement.

Acid Etching, Dental↗
PubMedDate not supplied

[Clinico-therapeutic considerations in a serious case of amelogenesis imperfecta].

The Authors present a case of a young female patient affected with a serious hypoplasic form of Amelogenesis Imperfecta, involving all the teeth which has been completely restabilished using composite resin. The therapy used has been developed thanks to the chemical-physical qualities of last generation of composites, which allow the compete reconstruction of teeth. Such a therapy has not to be considered definitive, however it has been used as a temporary solution, waiting for final prosthetic rehabilitation. The Authors estimate that such a temporary long term treatment, that utilize composite resins, represent the ideal therapeutical choice thanks to its characteristics of endurance, cost and benefice. In our opinion this therapy prevents tooth deterioration, secures a better mastication, a partial reduction of the teeth sensibility, facilitates teeth cleaning and solves the esthetical problems with great psychological advantage.

Amelogenesis Imperfecta↗
PubMed1978

Viscoelastic properties of the periodontal ligament and mucous membrane.

Load deformation studies were carried out on the maxillary arches of three adult Macaca irus monkeys using tooth-borne and tissue-borne plates. By means of an electronically controlled dynamometer, forces with different loading rates, creep, and simulated chewing loads were applied to the plates. The displacement was measured electronically relative to posterior teeth using a linear variable displacement transducer. The six main viscoelastic features noted by other workers for individual teeth under load have been confirmed for the test plates and can be attributed to the connective tissues in the periodontium and in the mucosa. The magnitude of displacement of the tissue-borne plate, however, was appreciably greater than for the tooth-borne plate, and the recovery was far slower. Reducing the part of the plate in contact with mucosa produced greater intrusion, and reducing the number of teeth supporting the tooth-borne plate produced greater displacement.

Acrylic Resins↗