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The effect of multiple uses of disposable diamond burs on restoration leakage.

BACKGROUND: The authors tested the clinical longevity of disposable diamond burs. They cut a series of five preparations and assessed the leakage after restoring the tooth. METHODS: The authors prepared 10 teeth for Class V restorations, and used a new disposable diamond bur for each tooth. The burs were used to cut preparations in extra teeth before being used to prepare a second series of 10 teeth (third use). The authors then cut preparations in extra teeth before preparing a third set of 10 teeth (fifth use). They removed existing restorations in a second group of 30 teeth and extended the preparations using the same regimen of one, three and five bur uses. All preparations were etched and conditioned, and the teeth were restored with resin-based composite. Using a 20-volt direct-current power source and a stainless-steel counter electrode, the authors measured the leakage electrochemically in 1.0 percent sodium chloride for 30 days. RESULTS: Freshly prepared and restored teeth leaked less than reprepared teeth. Leakage was similar for the first and third uses of the bur, but was far greater for the fifth use (P < .01). The previously restored teeth that were cut with the first- and third-use burs behaved the same, but the third-use bur caused more leakage than the fifth-use bur (P < .01). CONCLUSIONS: Reuse of disposable burs can affect leakage behavior. With new preparations, use of a disposable bur to cut more than three preparations increased leakage. For teeth that were reprepared and restored, greater leakage occurred than it did with new preparations, although repeated use of a bur may reduce leakage. CLINICAL IMPLICATIONS: Disposable diamond burs may cut preparations in up to three teeth before adversely affecting leakage behavior. Restoration removal and repreparation of teeth results in greater leakage than that with freshly prepared teeth.

Dental Cavity Preparation↗

Assessment of clinical preparations for single gold and ceramometal crowns.

OBJECTIVE: Single-crown preparations at a dental teaching hospital were compared with guidelines advocated in the dental literature. METHOD AND MATERIALS: Sixty-three single complete gold crown and 151 single ceramometal crown preparations were evaluated. Impression silhouettes were measured for occlusal and axial wall tooth reductions, shoulder widths, internal shoulder angles, and axial wall convergence angles. Marginal designs, the presence of retention grooves and undercuts, and the types of cores present were also recorded. RESULTS: Cuspal reduction was generally inadequate for the ceramometal crowns, and central fossa reduction was insufficient for both complete gold crowns and ceramometal crowns. The facial shoulder widths were also generally underprepared for the ceramometal crowns. Axial wall convergence angles for both complete gold crowns and ceramometal crowns were generally much greater than recommended. Large faciolingual convergence angles for anterior ceramometal crowns were associated with the absence of cingulum walls. Few preparations had retention grooves or undercut areas. CONCLUSION: Although strict guidelines for tooth preparations for complete crowns are available and well known to dentists, the preparations in this study did not always conform to these recommendations.

Analysis of Variance↗

Comparison of chemomechanical caries removal using Carisolv or conventional hand excavation in deciduous teeth in vitro.

OBJECTIVES: The purpose of the present study was to compare the efficacy of chemomechanical caries removal (Carisolv) to conventional hand excavation in deciduous teeth. METHODS: Twenty-two freshly extracted teeth with varying degree of caries were treated using both of these methods. One part of each caries lesion was prepared using the Carisolv method and the other part using conventional hand excavation. The third (middle) part was left untreated to serve as control. Histological preparations of each tooth were then made and examined in order to compare the quality of the preparations. Length and area of residual caries, microhardness of the dentine in each group and time needed for preparation were analysed. RESULTS: The results showed that there was no significant difference in the amount of residual caries in the cavity walls treated using the two methods. CONCLUSIONS: The Carisolv method was significantly more time consuming than conventional preparation using hand excavator. However, both methods removed caries efficiently.

Dental Caries↗

A laboratory analysis of gutta-percha-filled area obtained using Thermafil, System B and lateral condensation.

AIM: To determine the percentage of gutta-percha-filled area (PGFA) in the apical third of root canals when filled with either Thermafil, System B or lateral condensation. METHODOLOGY: Sixty extracted human maxillary central incisor teeth were root filled as following: G1: lateral condensation (n = 20), G2: System B (n = 20) and G3: Thermafil system (n = 20). A horizontal section was cut 2 and 4 mm from the apical foramen of each tooth. The samples were prepared for microscopic analysis and photomicrographs of each apical surface were taken at a magnification of 50x. Through digital image analysis, the cross-sectional area of the canal and the gutta-percha was measured. The PGFA was calculated. The PGFA data obtained in the three groups were analysed using a nonparametric Friedman and Wilcoxon signed-rank tests. RESULTS: Significant differences in PGFA were found between the Thermafil System (G3) and both System B (G2) and lateral condensation (G1) (P < 0.01). The greatest PGFA occurred in the Thermafil group. No significant statistical difference was found between System B and lateral condensation (P > 0.05). CONCLUSIONS: The coated carrier gutta-percha system Thermafil produced significantly higher PGFAs than lateral condensation and System B techniques.

Anatomy, Cross-Sectional↗

[The preprosthetic preparation of the endodontically treated abutment tooth. Post and core technique: a questionnaire analysis].

The goal of the questionnaire was to determine the materials and methods that general dentists in Switzerland at present use for the treatment of non-vital abutment teeth. Questionnaires were sent to 1000 dentists from a computer generated random sample of the list of members of the SSO (Swiss Dental Society). The return ratio was 36%. The responses provided information on the current philosophies and prevailing techniques used to restore endodontically treated abutment teeth. Most of the answering dentists believed it was necessary to stabilize a root treated tooth with a post. The preferred restoration in anterior teeth was the cast post and core, while composite resin build-up with a prefabricated post was predominantly made for posterior teeth. Conical or combined cylindrical-conical posts, which had a sand-blasted surface, were predominantly used. Most of the answering dentists strove to stabilize the remaining tooth structure by circular enclosure of the tooth structure by the later crown (ferrule effect). Zinc phosphate cement was still preferred for cementation of metal posts and ceramic posts were most often fixed with the help of the acid etching technique. The most frequently described failures were retention loss or root fractures.

Acid Etching, Dental↗

To place provisionals or not--that is the question.

Porcelain labial veneers are quite possibly the most esthetic restorations that can be provided today. Their esthetic qualities are derived not only from the accurate replication of tooth structure, but also from the superior tissue response they elicit. Many of the procedures surrounding this restoration have become almost standardized in terms of preparation and the manner in which the restoration is made to become part of the tooth. But why experts who lecture about this procedure remain at odds about whether provisional restorations are necessary is baffling. As more tooth preparation became increasingly necessary to achieve the ultimate in esthetics and health, use of the provisional restoration was not incorporated, simply as a matter of established routine.

Dental Porcelain↗

The effects of cavity preparation and lamination on bond strength and fracture of tooth-colored restorations in primary molars.

PURPOSE: This in vitro study compared bond strength and fracture modes of tooth-colored restorations in 2 types of cavity preparations in human primary molars. METHODS: Standardized Class II cavities (40 dovetail and 40 box-only preparations) in extracted human primary molars were restored with packable composite resin (PC), resin-modified glass ionomer cement (RMGIC), resin-modified glass ionomer/packable composite resin laminate (RMGIC/PC), or resin-modified glass ionomer/packable composite resin laminate with an experimental bonding agent, K-14 (RMGIC/K-14/PC). The ultimate load at fracture was measured on marginal ridges, and fractured surfaces were examined microscopically. RESULTS: The mean (+/-SD) ultimate load at fracture (ULF, in Newtons) of PC and RMGIC/K-14/PC in box-only preparations (400+/-98; 386+/-82) did not differ significantly from that found in dovetail preparations (377+/-80; 317+/-92), and the mean ULF of RMGIC and RMGIC/PC in box-only preparations (307+/-44; 325+/-72) did not differ significantly from that in dovetail preparations (352+/-71; 353+/-70). No interactions were seen between materials and preparations (P=.09). Fracture modes for restorations in dovetail (predominantly mixed) and box-only preparations (predominantly mixed and adhesive) differed significantly (P=.003), but not between restorative procedures (P=.052). CONCLUSIONS: Tooth-colored restorations placed in vitro in box-only preparations did not differ in fracture resistance from those placed in dovetail preparations. On fracture loading, resin-modified glass ionomer restorations placed in box-only preparations were more likely to show adhesive failure than those placed in dovetail preparations.

Analysis of Variance↗

Fatigue load of teeth restored with bonded direct composite and indirect ceramic inlays in MOD class II cavity preparations.

PURPOSE: This study compared the fatigue life of human maxillary premolars restored with direct composites and indirect ceramic inlays in mesio-occlusodistal (MOD) cavities. MATERIALS AND METHODS: Ten human maxillary premolars were divided into two groups of five and restored with (1) direct composite restorations, or (2) pressed ceramic restorations. Standardized MOD cavities were prepared for both groups. Teeth in the direct composite group were restored with Z250 composite and Single Bond adhesive, and those in the ceramic group were restored with IPS Empress ceramic inlays. The ceramic inlays were luted with Single Bond and RelyX ARC cement. Under the applied test load of 11.17 kg, strain measurements were recorded from an electric resistance stain gauge bonded to the buccal surface. These strains were recorded for the (1) intact tooth, (2) cavity preparation, and (3) restored tooth. These strain measurements were used to calculate the relative tooth compliance values for each tooth. The fatigue loading was applied until reinforcement loss was registered by the strain gauge. RESULTS: A one-way ANOVA showed no significant compliance difference between the intact and restored tooth conditions, and no significant difference in fatigue cycles to failure between the two groups. CONCLUSION: There were both adhesive and cohesive failures in both restoration groups, indicating that the adhesive joint is not the only weak link in these restorations.

Aluminum Silicates↗

Immediate implant placement and temporization in extraction and healing sites.

While single tooth replacement can be predictably accomplished using implant therapy, this procedure is challenging in the esthetic zone where numerous criteria must be evaluated by the restorative team. If the gingival and osseous architecture of the failing tooth is acceptable, the therapeutic goal is to maintain the existing morphological condition. The optimal tridimensional implant is placed in the esthetic zone immediately after extraction or 8 to 12 weeks after extraction. The abutment connection and the nonfunctional temporary tooth restoration are prepared in advance and should respect the forms of contour of the contralateral tooth. In some specific clinical cases, not only can the patient's smile be returned after only a few hours of clinical work, but more importantly, initial capital of soft and hard tissues can be preserved. After healing, maturation, and stabilization during the 3 to 6 months of osseointegration, a compressive impression of the implant site can be taken and the implant restoration can be cemented. A multi-centric study performed by several dentists during the past 3 years have drawn interesting statistics on the rate of success, the different type of implants, and the variation of the peri-implant bone and gingival contour.

Alveolar Process↗

Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment.

OBJECTIVES: To evaluate the effects of home bleaching (carbamide peroxide) on enamel surface morphology and the degree of acid dissolution. METHODS: Buccal surfaces of 15 caries-free human premolars were used in the study. The 15 teeth were cut in half in a buccal-lingual direction at midline; in total, 15 pairs of specimens were obtained. Group A consisted of five pairs that studied surface morphology change and Group B consisted of 10 pairs that studied the susceptibility of bleached enamel to acid dissolution. Tooth halves were prepared following a fluoride-free prophylaxis paste cleaning. One half of the tooth was untreated (control), and the other half was bleached (experimental) for eight hours daily for 10 days using 10% carbamide peroxide. Tooth samples were then stored in distilled water for seven days, after which scanning electron microscopy (SEM) was performed on Group A. Only halves from the same tooth were compared to rule out natural variations between teeth. Group B was etched with 37% phosphoric acid before being examined by SEM. The severity of the acid attack was graded from I to V, and the grades of each pair were compared. RESULTS: Results of the SEM observation showed that surface porosity slightly increased after bleaching, and more surface dissolution by phosphoric acid was seen with bleached, compared to unbleached, enamel.

Carbamide Peroxide↗

Effects of carbamide peroxide whitening agents on enamel surfaces and caries-like lesion formation: an SEM and polarized light microscopic in vitro study.

Whitening enamel with carbamide peroxide (CP) to remove cosmetically displeasing stains has become common-place in dental practice. This in vitro study evaluated CP treatment effects on enamel surface morphology and caries-like lesion susceptibility. Tooth quarters were prepared from 10 caries-free human molars following a fluoride-free prophylaxis. The tooth quarters were assigned to the following treatment groups: 1) Distobuccal-10 percent NW gel (Nite White, Discus Dental); 2) Distolingual-10 percent PL paste (Platinum, Colgate); 3) Mesiobuccal-16 percent NW gel; and 4) Mesiolingual-Control. Following the manufacturers' recommended treatment, each quarter was sectioned with one portion prepared for SEM and the other portion for caries-like lesion formation. Intact enamel surfaces were present with all treatments. Enamel prism markings with exaggerated prism peripheries and mild to moderate prism core loss were seen with both 10 percent NW and 16 percent NW gels, but was more prominent with 16 percent NW gel. Amorphous surface layers with occasional exposure of indistinct prism markings occurred with 10 percent PL paste. Body of lesion mean depths were 135 microns control, 159 microns 16 percent NW, 144 microns 10 percent NW, and 122 microns 10 percent PL. Lesion depths were significantly different (p < 0.05 DMR paired design) between 10 percent PL and 16 percent NW, and between control and 16 percent NW. Whitening enamel surfaces in vitro with 10 percent carbamide peroxide paste containing dicalcium phosphate dihydrate (Colgate-Platinum) produced an amorphous surface layer and reduced caries susceptibility when compared with 16 percent carbamide peroxide gel (Nite White).

Carbamide Peroxide↗

Inhibition in vitro of caries around amalgam restorations by bonding amalgam to tooth structure.

Class 5 preparations in human molars were restored with amalgam. In half of the restorations, an experimental resin liner capable of bonding amalgam to tooth structure was used. The restored teeth were incubated in a bacterial medium containing sucrose and a culture of Streptococcus mutans. Artificial carious lesions were produced around all restorations. The experimental liner inhibited penetration of the lesions along the cavity wall. This inhibition was more effective at the occlusal side.

Dental Amalgam↗