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The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time.

BACKGROUND: Different concentrations of carbamide peroxide (10 to 22 percent) have been used successfully as bleaching agents, but the adverse effects on enamel microhardness at different times are unknown. METHODS: The authors analyzed seven bleaching agents and a placebo. The agents were applied on the surface of human dental fragments for eight hours per day for 42 days and stored in vials containing artificial saliva. Microhardness measurements were performed at baseline, eight hours and seven, 14, 21, 28, 35 and 42 days, as well as at seven and 14 days after treatment had ended. RESULTS: Enamel treated with different bleaching agents or a placebo experienced a similar decrease in microhardness values over time, with the exception of fragments exposed to Opalescence PF 20 percent (Ultradent Products, South Jordan, Utah), or OPA20. Until the 49th day, the enamel exposed to OPA20 exhibited the lowest differences from baseline values. After 14 posttreatment days, enamel treated with placebo, Nite White 10 percent Excel (Discus Dental, Los Angeles), Nite White 16 percent Excel and Opalescence 10 percent exhibited the greatest differences from baseline values. An increase in enamel microhardness occurred at the end of the posttreatment period, although baseline values were not reached. CONCLUSIONS: Different concentrations of carbamide peroxide agents result in decreases in enamel microhardness. A post-bleaching period in artificial saliva resulted in recovery of baseline microhardness values (one agent) or an increase in values, although baseline values were not reached for these products. Clinical Implications. Higher concentrations of carbamide peroxide containing 0.11 percent ion fluoride can bleach teeth in a shorter period, with fewer hazardous effects on the enamel mineral content.

Carbamide Peroxide↗

Effect of water storage on tooth displacement in maxillary complete dentures.

The purpose of this study was to investigate the effect of water storage at 37 degrees C (1 week, 1 month and 3 months) on tooth displacement in maxillary complete dentures. Ten maxillary dentures were constructed with Clássico acrylic resin using the conventional method of packing in metallic flasks. Metallic reference pins were placed in the incisal border of the central incisors (I), labial cusp of the first premolars (PM), and mesiolabial cusp of the second molars (M). Twelve hours after final flask closure, the acrylic resin was cured in water at 74 degrees C for 9 h. The flasks were removed from the thermo-polymerizing unit after water-cooling and the dentures were deflasked, finished and stored in water at a temperature of 37 degrees C for 1 week, 1 month and 3 months. At deflasking and at the water storage intervals, the I-I (incisor to incisor), PM-PM (pre-molar to pre-molar), and M-M (molar to molar) transversal distances, and LI-LM (left incisor to left molar) and RI-RM (right incisor to right molar) anteroposterior distances were measured using an optical microscope with 0.0005 mm accuracy. Data were submitted to ANOVA and Tukey's test (5%). Comparing the evaluation periods for each individual transversal and anteroposterior reference point, no statistically significant differences were observed among deflasking and the water storage intervals for I-I, PM-PM, M-M and RI-RM distances (p>0.05). For LI-LM, however, deflasking values were statistically different from those of 1-week, 1-month and 3-month water storage intervals (p<0.05), which, in turn, did not differ statistically to each other (p>0.05). These results confirm the complexity of tooth displacement in complete dentures. From a clinical standpoint, the difference observed in LI-LM distance after water storage would not be detected by the patients during clinical use.

Dentures↗

Dimensional stability of distances between posterior teeth in maxillary complete dentures.

The aim of this study was to assess the displacement of posterior teeth in maxillary complete dentures stored in water at 37 degrees C. Twenty acrylic resin-based maxillary complete dentures were constructed with the anterior teeth arranged in normal overlap and the posterior teeth in Angle class I. Metallic pins were placed on the labial cusp of the first premolars (PM), and on the mesiolabial cusp of the second molars (M). The final acrylic resin pressing was made in a metallic flask with aid of the RS tension system, and polymerized in a moist-hot cycle at 74 degrees C for 9 hours. The dentures were deflasked after cooling in their own polymerizing water or after cooling in polymerizing water plus bench storage for 3 hours, and stored in water at 37 degrees C for periods of 7, 30, and 90 days. Following deflasking and after each storage period tested, the PM-PM (premolar to premolar), M-M (molar to molar), LPM-LM (left premolar to left molar), and RPM-RM (right premolar to right molar) distances were measured with an STM Olympus microscope, with an accuracy of 0.0005 mm. Collected data were submitted to ANOVA and Tukey's test (5%). There was no statistically significant difference for the PM-PM, M-M, and LPM-LM distances after all storage periods when the flask cooling methods were considered. With exception of the RPM-RM distance after the 30-days water plus bench storage period, the other distances remained statistically stable.

Acrylic Resins↗

A newer approach in positioning teeth for dental prosthetics using lateral cephalometric, trans-cranial radiographs, and the Denar-Witzig articulator: a case of hypodontia in an adolescent patient.

Traditionally in full denture prosthetics, anterior teeth are set on the models, independent of the effects on the face. More enlightened dentists, will then adjust the wax-up for speech, and some effects on the lips. Consideration is infrequently given to restoring the face by repositioning the teeth and mandible. Rarely is thought given to the effects of occlusion on the posture of the body. This report uses several techniques to restore facial esthetics and body posture. The techniques used include a cephalometric radiograph, transcranial radiographs, an articulator that has an adjustable "TMJ" (Denar-Witzig), and Symmetrigraf Posture Chart. This clinical report describes a newer approach in the positioning of maxillary anterior teeth for a patient with hypodontia and nail dysplasia syndrome, and the overall effect of this approach on the face and posture of the patient. Conventionally the precise form of the maxillary wax rim is fabricated with considerable variation from technician to another, based on the technicians training. This variation is evident on the position of the labial aspect of the rim horizontally and vertically. The wax rim is then further adjusted chair side based on subjective evaluation of the face. The maxillary anterior teeth position is established without considering that the lip position is not yet accustomed to the wax rim.

Adolescent↗

Use of acellular dermal matrix graft in the treatment of gingival recessions: a case report.

Case presentation in which a 12-years-old boy presented with two large gingival recessions on the maxillary central incisors, secondary to a lateral luxation. In the surgical procedure, an acellular dermal matrix graft (ADMG) was placed as a substitute for a free gingival graft. Twelve months later, complete root coverage was achieved, showing that ADMG, a biomaterial recently developed for mucogingival surgery, can be successfully used in the treatment of gingival recessions in pediatric patients.

Bicycling↗

Light microscopic and color television image analysis of the development of staining on chlorhexidine-treated surfaces.

Tooth staining with the use of chlorhexidine preparations is the major problem of long term application. Evidence suggests that the staining arises from a cationic/anionic interacation of chlorhexidine with components of certain dietary materials. The purpose of this in vitro study was to compare visually the development of tea and coffee staining on acrylic and tooth specimens treated with chlorhexidine and to follow the development of tea staining on perspex by light microscopy and color television image analysis. All specimens were maintained in their respective beverage for 5 days with test specimens removed three times a day and placed for 2 minutes in an 0.2% chlorhexidine solution. Both test tooth and acrylic specimens showed comparably and markedly increased staining by the beverages compared with control specimens. Color television image analysis of test specimens demonstrated more marked and rapid development of tea staining when studied on a daily basis. Microscopic examination revealed the staining to be made up of small particles of material which increased in size and coalesced with time. Again, marked differences were apparent in the stain on test and control specimens. The results of this in vitro method provided further evidence for a dietary aetiology to chlorhexidine staining and were consistent with clinical findings. Such a method may be useful to assess staining arising from the use of other anti-plaque agents.

Acrylic Resins↗

[The evaluation of wear resistance of hybrid denture teeth].

Wear characteristics of hybrid denture teeth, plastic denture teeth which were partially reinforced with metal, was evaluated. The plane specimens were made up with resin and metal. Light curing veneering resin, new metacolor, heat curing veneering resin, Mitel-OM and PMMA (Poly methyl methacrylate) were used for resin parts, while gallium containing filling alloy, silver alloy, palladium alloy and titanium containing chromium cobalt alloy were used for metal parts. The specimens were abraded by the rod specimens of palladium alloy with abrasion test machine. The wear depth and width were measured at 1, 5, 10 and 20 x 10(4) times of abrasion which stroke was 10 mm each. The specimens of heat cured veneering resin reinforced with chromium cobalt alloy showed the least wear loss while the specimens of PMMA reinforced with silver alloy did the most. The difference of wear ratio between light cured and heat cured veneering resin was not statistically significant.

Dental Alloys↗

The Carolina bridge: a novel interim all-porcelain bonded prosthesis.

UNLABELLED: Numerous bonded bridge designs have been advocated over the years for the temporary or permanent replacement of missing teeth. Both metal and all-porcelain designs of bonded bridges have been advocated, with varying degrees of success. However, all of these designs involve some degree of tooth preparation, making them irreversible in nature. The Carolina bridge, a novel all-porcelain bonded pontic, requires no significant tooth preparation, making it an outstanding option as an interim prosthesis. The key to success is the availability of adequate surface area interproximally to ensure optimally strong resin composite connectors. CLINICAL SIGNIFICANCE: This article describes the indications, contraindications, and clinical technique for the placement of an ultraconservative all-porcelain bonded bridge for the interim replacement of single incisors.

Composite Resins↗