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3 cases of contact dermatitis due to a Chinese herbal orthopaedic solution Tieh Ta Yao Gin and its putative ingredients are reported. Patch testing demonstrated allergy to mastic and myrrh, natural gum resins widely used in traditional Chinese medicine to relieve pain and swelling due to traumatic injury.
Naturally occurring gums and resins with beneficial pharmaceutical and nutraceutical properties were tested for their possible protective effect against copper-induced LDL oxidation in vitro. Chiosmastic gum (CMG) (Pistacia lentiscus var. Chia resin) was the most effective in protecting human LDL from oxidation. The minimum and maximum doses for the saturation phenomena of inhibition of LDL oxidation were 2.5 mg and 50 mg CMG (75.3% and 99.9%, respectively). The methanol/water extract of CMG was the most effective compared with other solvent combinations. CMG when fractionated in order to determine a structure-activity relationship showed that the total mastic essential oil, collofonium-like residue and acidic fractions of CMG exhibited a high protective activity ranging from 65.0% to 77.8%. The other natural gums and resins (CMG resin 'liquid collection', P. terebinthus var. Chia resin, dammar resin, acacia gum, tragacanth gum, storax gum) also tested as above, showed 27.0%-78.8% of the maximum LDL protection. The other naturally occurring substances, i.e. triterpenes (amyrin, oleanolic acid, ursolic acid, lupeol, 18-a-glycyrrhetinic acid) and hydroxynaphthoquinones (naphthazarin, shikonin and alkannin) showed 53.5%-78.8% and 27.0%-64.1% LDL protective activity, respectively. The combination effects (68.7%-76.2% LDL protection) of ursolic-, oleanolic- and ursodeoxycholic- acids were almost equal to the effect (75.3%) of the CMG extract in comparable doses.
This study introduces a modified dynamic testing mode with gradual load increase and examines whether this could be an alternative to customary methods of static loading or chewing simulation. Seventy-two extracted human maxillary root-canal-treated central incisors were randomly divided into six groups with 12 teeth each. Three groups were restored with titanium posts cemented with chemically curing resin cement. The other three groups were restored with glass-fiber posts cemented with dual-curing composite cement. All teeth were capped with full ceramic crowns. Both kinds of restoration were tested by linear compressive (static) loading, a modified gradual (cycling) dynamic loading, and by chewing simulation followed by static loading until failure occurred. The maximum load capacity was recorded. Statistical comparison showed that maximum load capacities of the same post material obtained from gradual dynamic loading did not differ significantly from that of linear compressive loading or of chewing simulation. In contrast, comparisons of different post materials under static loading resulted in significantly different load capacities. Dynamic testing with gradual load increase can be considered an economic alternative for chewing simulation, because it provides equivalent results. Both procedures, however, imply different conclusions than static loading with respect to post materials.
Diabetes has many manifestations, including increased vulnerability to bacterial and fungal infections, that may be of concern to the dental profession. Oral candidosis and other opportunistic fungal infections may be early, nonspecific signs of uncontrolled diabetes. Rhinocerebral involvement often extends to the paranasal sinuses, pharynx, palate, orbit, and brain, causing severe tissue destruction and necrosis. This clinical report describes a young woman with diabetes who developed mucormycosis of the maxilla. Tissue destruction resulted in loss of the entire premaxilla, the anterior half of the hard palate, and all maxillary teeth except for the right and left second molars. An interim clear acrylic resin prosthesis was fabricated to restore facial contours and speech and to allow mastication. This prosthesis subsequently was duplicated, and teeth were added for improved lip support, esthetics, and mastication.
A method of curing light-cured composite resins by transillumination to cement acid-etched fixed partial dentures was adapted to bond solid mesh-backed lingual orthodontic brackets. Results of this investigation showed that the bond strengths of the orthodontic brackets bonded with light-cured composite resins were significantly less (P less than 0.05) than the bond strengths of the orthodontic brackets cemented with traditional adhesives and orthodontic composite resins. Notwithstanding, the bond strengths achieved with the transilluminated light-cured composite resins should be adequate to withstand the forces of mastication and orthodontic movements. There was no correlation of bond strengths of the brackets cemented with the transilluminated light-cured composite resins when compared to the faciolingual widths of the teeth.
PURPOSE: The aim of this study was to test in vitro the resistance of a modified resin-bonded fixed partial denture (RBFPD) to detachment using a laboratory setup simulating load fatigue of mastication forces. The effect of varying the cement type was also investigated. MATERIALS AND METHODS: Extracted teeth were used to prepare specimens each consisting of a premolar and a molar with a space equivalent to a molar in between. Five test groups were prepared (n = 7). Specimens in group 1 were prepared to receive conventional RBFPDs with proximal grooves, occlusal rests, and lingual wings. Specimens in groups 2 and 3 were prepared to receive modified RBFPDs with retentive-slot restorations. Specimens in group 4 were prepared to receive RBFPDs with retentive-slot restorations only, whereas specimens in group 5 were prepared similarly to the ones in groups 2 and 3 but with inlay preparations instead of the retentive slots. Castings were made and their fit surfaces microetched. In groups 1, 2, 4, and 5 castings were cemented with Cement-It, whereas castings of group 3 were cemented with Panavia 21. Slot cavities of groups 2, 3, and 4 were restored with a resin composite. Specimens were subjected to compressive load cycling for 230,000 cycles at 4 Hz under water. Castings were then separated from the abutments under tensile loading. RESULTS: Mean separation forces were: group 1 = 361 N, group 2 = 525 N, group 3 = 562 N, group 4 = 449 N, and group 5 = 417 N. Groups 2 and 3 had significantly higher mean separation forces than groups 1 and 5. Separation of castings in groups 2 and 3 was associated with a higher frequency of cohesive fracture of the abutments than in group 1. Adhesive failure was uncommon among specimens of groups 2, 3, and 4. CONCLUSION: The modified RBFPDs of groups 2 and 3 had better potential for retention. Increased resistance to dislodgment of the modified RBFPDs was not directly related to the surface area of the castings, nor was it related to the type of resin cement, but rather to mechanical interlocking of the castings with the retentive-slot resin composite restorations.
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PURPOSE: To evaluate in a pilot study whether (1) loading of restored teeth in a chewing simulator is an adequate method to reproduce clinical data about the retention rate of restorations placed in noncarious cervical lesions by means of the one-step self-etching adhesive system Prompt-L-Pop, and (2) whether eccentric loading contributes to the loss of Class V fillings. MATERIALS AND METHODS: In 12 extracted mandibular premolars with noncarious buccal cervical lesions of similar dimensions, restorations were placed without preparation using Prompt-L-Pop and Tetric Ceram. The adhesive was applied in one layer and cured at 650 mW/cm2 for 10 s, while the composite was placed in two increments and cured at 1200 mW/cm2 for 10 s. After storage in water at 37 degrees C for 7 days, the teeth were mounted in a chewing simulator that uses pneumatic cylinders as force actuators and subjected to a centric load of 50 N and 1,200,000 load cycles at a frequency of 1.6 Hz and simultaneously to 3125 thermocycles (5 degrees C/55 degrees C). The antagonists were standardized and made of Empress ceramic material. Every 100,000 load cycles, the fillings were evaluated with regard to retention. In the second phase, the same teeth were loaded on the lingual cusps with new antagonists for another 1,200,000 cycles. RESULTS: Neither during centric nor eccentric loading was any restoration loss observed. CONCLUSION: The short-term loading of extracted teeth with Class V fillings in a chewing simulator was inadequate to reproduce the data of clinical studies on the retention rate of a self-etching adhesive system. Obviously, long-term degradation mechanisms (eg, hydrolysis) acting on the composite/dentin interface play a more crucial role when it comes to the loss of retention of Class V restorations. Eccentric loading alone did not contribute to the loss of fillings, so that the theory--which maintains that this type of occlusal stress is a major cause for abfractions or the retention loss of restorations placed in abfraction lesions--may be questioned.
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STATEMENT OF PROBLEM: In a clinical study, all-ceramic resin-bonded fixed partial dentures showed a high rate of fractures within the first years of service but remained in function as cantilevered restorations. No data are available on the fracture strength of such cantilevered restorations. PURPOSE: This in vitro study evaluated the influence of design and mode of loading on the fracture strength of all-ceramic resin-bonded fixed partial dentures. MATERIAL AND METHODS: Forty-eight frameworks were copy milled using the aluminum-oxide ceramic In-Ceram, glass-infiltrated, and circularly veneered with feldspathic porcelain to replace a maxillary incisor on a test cast. The airborne particle-abraded restorations were bonded to acid-etched human abutments using composite. Twenty-four restorations used a conventional 2-retainer design and another 24 restorations used a cantilevered single-retainer design. Subgroups of 8 specimens were subjected to a quasi-static load in the direction of the long axis of the abutments (0 degrees) or in an angle of 45 degrees. Additional subgroups were subjected to dynamic loading under 45 degrees with either 50 or 25 N in a dual-axis chewing simulator until fracture. RESULTS: Mean fracture strengths, under 45-degree quasi-static loading, were between 134 and 174 N and under 0-degree loading about 233 N. Samples subjected to dynamic loading fractured after 25 to over 200,000 loading cycles. CONCLUSION: Direction of loading exhibited a significant influence on the fracture strength, regardless of the retainer design. The applied dynamic loading force, regardless of the retainer design, had a significant influence on the loading cycles until fracture.
The authors present a few cases maxillary and facial reconstruction with restoration of the esthetic appearance, mastication and phonation, using the obturator muscles and prostheses made up of acrylic resin and silicone elastomers.
The purpose of this study was to evaluate how the different mechanical properties of two luting agents (acrylic resin cement and resin composite cement) influenced their bond strength to dentin, after cyclic loading that simulated chewing. Stainless steel rods were bonded to the flattened dentin surfaces with each luting agent. After immersion in water for 24 hours, half the specimens of each group were tested for tensile bond strength and the remaining half were subjected to a vertical load (75.6 N, 1.2 Hz) using an acrylic stylus--which upon contact with the specimen would rotate counterclockwise and then counter-rotate. Bond strength of the resin composite cement with self-etching was found to be significantly lower than the other adhesive systems. After 100,000 cycles, the bond strength of resin composite cement was significantly decreased while acrylic resin cement showed no decrease in bond strength.
PURPOSE: To determine the in vitro wear resistance and microstructural stability of composites in which the beta quartz insert was used. MATERIALS AND METHODS: Three different sized inserts were used in conjunction with P-50 and Herculite XR posterior resin composites. The study was designated to create varying gap dimensions between the insert and wall of the preparation (0.75, 1.25 and 1.50 mm). In addition, one half of the inserts contacted the dentin floor of the cavity whereas the other half rested on 1.0 mm of composite. The controls consisted of resin composite only. Using an in vitro wear testing device, all specimens were subjected to 400,000 cycles of masticatory loading. Upon completion of testing, profilometric tracings and SEM were used to determine relative wear, patterns of wear and microstructural changes. Differences, in wear values were analyzed by two-way ANOVA. RESULTS: The wear values for P-50 and Herculite XR controls were 24.8 and 31.3 micrometers, respectively. No significant differences were detected (P<0.05) in amount of wear between the control specimens and the insert specimens, regardless of size. The same results were obtained regardless of whether the insert rested on dentin or resin composite. SEM evaluations however, revealed excellent interfacial continuity after wear testing. While the inserts did not influence the wear resistance, they may provide an excellent means for maintaining functional occlusion.
OBJECTIVES: The reliability and validity of the adhesive bond toughness of dentin/composite resin interfaces were studied from the standpoint of fracture mechanics. METHODS: The fracture toughness (KIC) and fracture energy (JIC) values of two different composite resins (Brilliant Dentin and P50) were determined by using single edge notch (SEN) specimens loaded in three point bending and the results were analyzed by the t-test method (p < 0.1). The fracture loads of dentin/composite resin interface with different initial crack lengths were obtained experimentally. The adhesive fracture energy (J(adh)), residual fracture energy (J(res)) and effective (total) fracture energy (J(eff)) for the symmetrical bimaterial (SBM) joint specimen for dentin/composite resin interfaces were calculated and the applied fracture energy (J(appl)) values under the mastication force were obtained for the axisymmetric tooth models. All numerical calculations were carried out by the finite element method and software programs were prepared according to fortran 77. RESULTS: The fracture toughness and energy values obtained experimentally for Brilliant Dentin were found to be higher than those for P50. It was seen that, calculated J values (J(adh) and J(res)++) changed with the crack length; but the effective fracture energy (J(eff)++) was independent of the crack length, as expected. The applied fracture energy (J(appl)) and effective fracture energy (J(eff)) are considerably smaller than the experimentally determined JIC values of composite resins. SIGNIFICANCE: The bonded interface tends to produce microscopic flaws which could act as critical stress risers promoting interfacial failures. The initiation and propagation of such flaws under the mastication forces can be followed by fracture toughness (KIC) or fracture energy (JIC) in linear elastic fracture mechanics (LEFM).
BACKGROUND: An in vitro device has been developed to predict the long-term clinical performance of posterior composite resins. In contrast to most systems, it is based on three-bodied wear--the type of wear generated by food bolus during mastication. METHODS: The authors wear-tested two groups of materials that included posterior composite resins, a castable ceramic, an amalgam and an unsalinated composite resin. After the wear-testing device concluded 400,000 cycles, the authors evaluated replicas of restoration surfaces for material loss. They used scanning electron microscopy to determine the mechanism of wear. RESULTS: The authors detected considerable differences in wear among the various materials included in the study. All of the differences, however, fell within the range of results obtained from the positive and negative controls (unsilanated composite resin and ceramic, respectively). A comparison of the in vitro wear values with the wear values obtained from a series of ongoing clinical studies at the same institution revealed a high level of agreement. Furthermore, replicas of the laboratory-tested composite resin samples revealed the same wear patterns as those generated from clinical restorations. The variation coefficients for the in vitro data generally did not exceed 5 percent, whereas those for the clinical data commonly averaged 20 percent. CONCLUSIONS: Based on the results of this study, the authors conclude that the in vitro testing device is reliably capable of predicting long-term clinical wear values. The results obtained after 92 hours of wear testing correlated closely with those obtained after three years of clinical testing. CLINICAL IMPLICATIONS: Long-term clinical studies are both time-consuming and expensive. Reliable in vitro wear-testing techniques allow manufacturers to develop or modify composite resin systems in considerably shorter periods.
A wear test method based on a new concept was developed for predicting the wear rate of posterior composite restorations in vivo. The concept based on the conclusions derived from our clinical tests on posterior composites that composite restorations would be deteriorated chemically and by repeated compressive stress as well as by abrasion by food passing during mastication. New wear tests were performed on several posterior restorative materials under various conditions to compare the effect of abrasion using the tooth-brush. The results of wear rate using the present test on specimens stored in a 0.1 N-NaOH solution (37 degrees C) for 6 days were parallel to those measured in clinical tests. However, the abrasion test results obtained using a tooth-brush on deteriorated specimens did not match the clinical data. These findings suggested that degradation or aging of specimens and repeated compressive stress are necessary for the wear test to simulate the wear of posterior composites in vivo.
PURPOSE: The purpose of this investigation was to compare the fracture toughness of several core materials. MATERIALS AND METHODS: Five core build-up materials were tested: (1) glass ionomer, (2) resin-modified glass ionomer, (3) titanium-reinforced composite, (4) composite resin with fluoride, and (5) amalgam. Fracture toughness determinations were made using 3-point flexure of beams with a central single-edge notch. The notch was standardized by the use of a special mold into which each of the materials was condensed. Ten beams of each material were tested on an Instron test machine (Instron Corp, Canton, MA) at a crosshead speed of 1.25 mm/min. The maximum loads were determined from which the fracture toughness values (KIC) were calculated. The data were analyzed statistically using analysis of variance and t tests. RESULTS: The mean fracture toughness value in MN.m-3/2 for each of them is as follows: (1) glass ionomer, 0.717 +/- 0.071; (2) resin-modified glass ionomer, 0.747 +/- 0.061; (3) titanium-reinforced composite, 1.409 +/- 0.051; (4) composite resin with fluoride, 1.660 +/- 0.086; and (5) amalgam, 1.521 +/- 0.081. There was no significant difference in the KIC values for the glass ionomer-based materials, and both of these were significantly lower than amalgam, titanium-reinforced composite resin, and composite resin with fluoride (p < .001). CONCLUSION: The titanium-reinforced composite resin, the composite resin with fluoride, and amalgam materials showed fracture toughness most likely to withstand the stresses generated during mastication.
Comatose patients may develop a neuropathologic chewing reflex that results in self-inflicted oral trauma. Loss of coordination between the tongue and chewing cycle leads to maceration of the tongue and infection. The use of a tongue-depressing stent can keep the tongue from acting as a bolus and prevent perpetuation of the reflex chewing cycle and resultant self-injury.