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Compomers adaptation to Class I and V cavities in permanent teeth.

This study evaluated the adaptation of Compoglass, Dyract and Hytac to Class I and V cavities and the effect of etching on that adaptation. Sixty molars were used, divided for the three compomers used, which were subdivided for Class I and V and redivided into etched and nonetched cavities (5 each). Standard Class I and V cavities were prepared. The adhesives were applied and the cavities restored with the compomers. The restoration was finished and the cavosurface margins examined under the light microscope for any gap formation. The restored cavity was sectioned in two halves, which were fixed in glutaraldehyde and polished. The restoration-tooth interface was examined under the light microscope for any existent gap. Then one half from each tooth was prepared for SEM examination. The results revealed good adaptation of the compomers at the cavosurface margins except nonetched Class V cavities restored with Dyract. Restorations in Class V were more adapted than Class 1. Dyract and Compoglass showed better adaptation inside the cavity than Hytac. Cementum wall displayed good adaptation with all restorative materials. Etched cavities showed consistent hybrid layer formation whereas nonetched cavities showed interrupted hybrid layer with poor resin penetration.

Acid Etching, Dental↗

Real-time atomic force microscopy of root dentine during demineralization when subjected to chelating agents.

AIM: To explore the potential of atomic force microscopy (AFM) for the examination of changes to dentine surfaces during demineralization and evaluate qualitatively the effect of EDTA, EDTAC and citric acid. METHODOLOGY: Nine canine teeth were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, each root was embedded in an epoxy cylinder and discs approximately 5 mm thick were cut. A standard metallographic procedure was then used to prepare the surfaces for observation. From the central portion of these samples, two specimens were symmetrically prepared per tooth so that a total number of 18 samples was produced. To allow the use of a liquid cell during AFM, the samples were embedded in silicone rubber and were then randomly divided into three groups, as follows: group 1: 17% EDTA (pH 7.7), group 2: 17% EDTAC (pH 7.7) and group 3: 10% citric acid (pH 1.4). Topographical images were acquired during the demineralization process, allowing real-time observation of the dentine surface. Two operators assigned scores to the AFM images using a double-blind method. anova analysis with random effects (P < 0.05) was used to compare the results. RESULTS: The average scores were 6.13 +/- 0.35 for EDTAC, 7.36 +/- 0.23 for EDTA and 14.55 +/- 1.21 for citric acid. Citric acid was statistically different from EDTA and EDTAC while EDTA and EDTAC were not statistically different. CONCLUSIONS: The most effective demineralizing substance was citric acid. The methodology developed for real-time observation of dentine surfaces is a valuable method to evaluate demineralization.

Chelating Agents↗

Aesthetic changes with four anterior units.

Cosmetic dentistry has evolved with the advent of more robust porcelain materials and ever-stronger bonding agents. This series of three articles aims to provide a practical overview of what is now possible both functionally and cosmetically from the preparation of a small number of teeth, through a whole smile, to full mouth rehabilitation. A complete diagnosis is the starting point to planning any cosmetic or functional changes. Guidance is given on the techniques used but adequate training must be considered essential before embarking upon modification in occlusal schemes or even minor adjustments in smile design. Conservative use of porcelain laminate veneers can result in significant aesthetic improvements to a patient's smile and it is not always necessary to prepare all the teeth visible in a smile.

Cementation↗

Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns.

The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate cement using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Crown retention and marginal discrepancy were influenced by the preparation convergence design.

Cementation↗

The response of human premolars to cyclic loading.

The aim of the study was to obtain data on the dynamic strength of both intact and prepared premolars for partial veneer crowns. Cyclic loading was performed in a modified Amslers high-frequency pulsator with varying force (between 400 and 1400 N). The greatest dynamic strength was exhibited by the intact samples. The greater the load the fewer the cycles necessary to fracture the tooth. A statically significant difference was found (P < 0.05) between the magnitude of cyclic loads and the different types of specimens tested.

Analysis of Variance↗

Conventional and digital radiographic methods in the detection of simulated external root resorptions: a comparative study.

OBJECTIVES: The purpose of this study was to evaluate and to compare the efficacy of a conventional and a digital radiographic method in diagnosing simulated external root resorption cavities. METHODS: Human dry mandibles containing teeth were covered with bovine muscle slices in order to simulate the soft tissues. Nine teeth from each dental group were investigated. Three periapical radiographs of each tooth were taken in an orthoradial, mesioradial and distoradial aspect using conventional film (Insight Kodak F-speed; Eastman Kodak, Rochester, NY) and a digital sensor (DRS Gnatus System; Gnatus, Ribeirao Preto, Brasil). The teeth were extracted using a forceps and had 0.7 mm and 1.0 mm deep cavities prepared on their vestibular, mesial and distal surfaces at the cervical, middle and apical thirds. Following preparation, each tooth was replaced in its alveolus and new radiographs were taken. Three dental professionals, an endodontist, a radiologist and a general practioner, evaluated the images. RESULTS: A larger number of cavities (P<0.05) were detected by the digital method when compared with the conventional method, for all depths of lesions. CONCLUSIONS: The results of this study suggest that the digital radiographic method is more sensitive than conventional radiography to detect simulated external root resorption cavities.

Animals↗

Thickness of the remaining enamel after the preparation of cingulum rest seats on maxillary canines.

PURPOSE: This study evaluated the level of tissue removal that takes place on enamel and dentin during cingulum rest seat preparation. MATERIAL AND METHODS: A quantitative evaluation of the thickness of the remaining enamel of cingulum seat preparations to receive removable partial denture rests was carried out in 20 maxillary canines with a light optical microscope. RESULTS: Thirty percent of the preparations were overextended into dentinal tissue, and 85% had depths that were insufficient to receive rests.

Cuspid↗

Esthetic proportions versus biologic width considerations: a clinical dilemma.

Combining harmonious proportions of final restorations with periodontal health and stability surrounding these restorations is a basic fundamental in esthetic dentistry. However, when one can adversely affect the other, a clinical dilemma arises. This article describes a case with unfavorable proportions that may be worsened due to an existing unfavorable preparation design. A simple approach for diagnosis and treatment of such a situation is presented.

Adult↗

Effect of cavity disinfection on bond strength to dentin.

The application of a disinfecting step in cavity preparation and tooth restoration is gaining wider acceptance. This study examined the effect of two commercially available disinfecting agents on the shear bond strength to dentin using a fourth generation dentin bonding agent. The agent tested permitted an evaluation of both dry and wet bonding techniques. It was found that the commercial preparations did not adversely affect shear bond strength to dentin in either the dry or wet application.

Analysis of Variance↗

Clinical evaluation of marginal fit of a new experimental all-ceramic system before and after cementation.

PURPOSE: The purpose of this in vivo study was to evaluate the marginal fit of inlay and crown abutments for fixed partial dentures (FPD) made from a new all-ceramic material. MATERIALS AND METHODS: Sixteen patients were selected for the study. After abutment preparation, impressions were made and master dies were fabricated. FPDs were made with the experimental heat-pressed lithium-disilicate glass-ceramic following the manufacturer's recommendations. At random, one abutment of each FPD was chosen for evaluation (11 crown and 8 inlay abutments). Impressions of the restoration margins were taken before and after adhesive cementation. Replicas of the abutment margins were investigated by SEM. The marginal discrepancies were evaluated in sections of 200 microm. The highest value of each section was applied, and the mean of all sections of each replica was used for statistical analysis. RESULTS: The median of the marginal discrepancies before cementation was 96 microm for crowns and 89 microm for inlays. After adhesive cementation, the median increased for crowns to 130 microm and for inlays to 92 microm, a significant increase in the marginal discrepancies caused by cementation for crowns, but not for inlays. There were no significant differences between the discrepancies of crowns and inlays before or after cementation. CONCLUSION: The maximum marginal discrepancies found in this study were between 50 and 265 microm before cementation and between 70 and 285 microm after cementation, with no significant differences between the means for crowns and inlays. Adhesive cementation caused a significant increase of the marginal discrepancies for crown, but not inlay, abutments.

Cementation↗

Integrating posterior crowns with partial dentures.

This article outlines those considerations which are important in integrating posterior crowns with partial dentures. Planning the support and retention of the denture prior to crown construction will enhance patient treatment. Modification of the crown preparation to incorporate rest seats, retentive areas, guide planes and a planned path of insertion may be necessary.

Bicuspid↗

[Preparation trauma in stomatology].

In this paper authors deal with the causes of preparation trauma in stomatology. They have studied effects of high temperature on human cells cultured in vitro. Based both on literature data and on their own experience they summarize basic principles of preparation which prevent preparation trauma. They summarize how to eliminate as much as possible factors that damage hard dental tissues and pulp.

Cell Line↗

Fracture resistance of five pin-retained core build-up materials on teeth with and without extracoronal preparation.

Core build-ups should provide satisfactory strength and resistance to fracture both before and after crown preparation. This paper examines the resistance to fracture of core build-ups in different materials and the fracture resistance of core build-ups when these have been reduced for full crown preparation. Standardized core build-ups were made on groups of extracted molar teeth of similar size, with 10 teeth per group. Three resin-composite (prisma APH: Dentsply, Weybridge, UK; Ti-Core, Essential Dental Systems, NJ, US and Coradent, Vivadent, Liechtenstein), one cermet (Ketac-Silver, ESPE GmbH, Seefeld, Germany) and one amalgam material (Duralloy, Degussa Ltd, Cheshire, UK). These specimens were subjected to compressive force on a universal testing machine and the force at fracture noted. Standardized full crown preparations were made on a further five groups of core build-up specimens using the same materials as above. These prepared specimens were subjected to compressive force on a universal testing machine and the force to fracture noted. The results indicated that amalgam core build-ups demonstrated higher fracture resistance than the other materials examined. There was a general decrease in the fracture strength of the specimens following crown preparation, with the teeth restored with the amalgam core build-ups showing a greater percentage reduction in fracture strength than the other materials tested. Prepared core build-ups in a hybrid composite material provided the highest fracture resistance. The cermet material used provided the lowest resistance to fracture in both the core build-up and crown preparation specimens. In terms of fracture resistance, no advantage was apparent in using the two composite materials designated as being specifically appropriate for core build-ups.

Analysis of Variance↗

Polyethylene fiber-reinforced composite inlay fixed partial dentures: two-year preliminary results.

PURPOSE: Polyethylene fiber-reinforced composite inlay fixed partial dentures (FPDs) have been under development for some time. There is a lack of data on the clinical performance of such prostheses. This prospective clinical study evaluated the clinical performance of polyethylene fiber-reinforced composite FPDs over two years. MATERIALS AND METHODS: Twenty-eight polyethylene fiber-reinforced composite inlay FPDs were fabricated for 19 patients. The treatment plan included removal of the existing restorations, placement of an ultrahigh molecular weight polyethylene (UHMWP) fiber ribbon, and final restoration with a light-curing hybrid resin. The 28 polyethylene fiber-reinforced composite inlay FPDs were examined clinically after 2 years. RESULTS: All 28 FPDs were intact at the 2-year examination. There were no signs of fracture, debonding, or discoloration. CONCLUSION: Based on the results of this descriptive study, the polyethylene fiber-reinforced composite inlay FPDs were considered clinically successful at the 2-year examination.

Adult↗

[Stress analysis of the post and core system under loading].

PURPOSE: To analyze the stress of the post and core system by using finite element analysis and study the influence of the "crown materials" on the analytic results. METHODS: Three groups of 3D finite element models of maxillary incisors were established according to the fabricating standard of the post and core system by using I-DEAS finite element analysis software. Group A was consisted of the cast metal post and core, the tooth structure after preparation and the periodontal structure. Group B was composed of the PFM, the cast metal post and core, the tooth structure after preparation and the periodontal structure. Group C was composed of the resin crown, the cast metal post and core, the tooth structure after preparation and the periodontal structure. The three groups were loaded and analyzed under the same loading according to the mean value of the bite force of incisors. RESULTS: (1)The maximum stress of dentin in group A was twice higher than that in group B. The maximum primary stress, minimum primary stress and maximum shear stress of group A were respectively 236.35, 228.83 and 218.05 percent of those in group B. The difference of maximum stress values of group B and group C was neglectable. (2) The maximum stress distribution of dentin in group A and group B was quite different (the stress was concentrated in labial and lingual side of the cervical dentin in group A, otherwise in group B it was concentrated in the area around the alveolar and the labial and lingual side of the dentin which was opposite to the tip of the cast metal post and core). The maximum stress distribution of dentin in group A and group B was almost the same. CONCLUSIONS: Different materials of the crown did not influence the result of 3D finite element stress analysis of the post and core system.

Bite Force↗

Preparations for porcelain laminate veneers in general dental practice.

OBJECTIVE: To investigate variations in preparations for porcelain laminate veneers (PLVs) in general dental practice. DESIGN: Laboratory-based retrospective analysis of dies for PLVs. SETTING: General dental practice in England and Wales (1994). METHODS: A sample (95 cases) of laboratory models from general dental practice featuring preparations for PLVs was randomly selected from a full service commercial dental laboratory. Aspects of the preparations were quantified and compared with accepted preparation criteria distilled from a review of the literature. RESULTS: The teeth found to be most frequently prepared for PLVs were maxillary incisors (48%). The majority of cases investigated were for one veneer only (56%). The margins of the preparations were variably positioned with more than half of the preparations (55%) having no clear margin. In accordance with current guidelines the incisal edge tended to have been reduced during preparation (47%). In contrast, most teeth were underprepared with an average depth of preparation of 0.16 mm (SD 0.60 mm, 95% CI-0.1, 0.42). CONCLUSIONS: There was little evidence that established guidelines for the preparation of teeth for PLVs had been applied in full.

Dental Porcelain↗

Endodontic treatment of a supernumerary tooth fused to a mandibular second molar: a case report.

Since abnormal tooth morphology can predispose to caries and periodontal disease, careful management of fused teeth is essential. In this paper we report a rare case of a fused molar and supernumerary tooth and describe its management. Caries was removed from the tooth complex under local anesthesia. The pulp chamber of the supernumerary tooth was exposed without involvement of second molar pulp chamber. The root canal of the supernumerary tooth was prepared using the step back technique and copious irrigation with 2.6% sodium hypochlorite. Obturation using the lateral condensation technique with gutta-percha and AH26 sealer was subsequently performed and final restoration was accomplished with composite resin. Nine months after the treatment, no clinical or radiographic concern is apparent, and the second molar tooth has remained vital.

Adult↗

Bactericidal eradication from carious lesions of prepared abutments by an antibacterial temporary cement.

PURPOSE: The aim of this study was to observe the antibacterial potential of polycarboxylate temporary cement containing a mixture of metronidazole, ciprofloxacin, and cefaclor on carious lesions of prepared abutments that were designed to leave caries on the abutments. MATERIAL AND METHODS: Antibacterial efficacy was estimated in vitro and in vivo by measuring bacterial recovery from the lesions. Bacteria counts ranged from 10(4) to 10(7) both in vitro (nine samples) and in vivo (five samples) in time-zero samples, just before the application of the antibacterial cement. RESULTS: No bacteria were recovered from carious lesions in vitro (six samples) or in vivo (four samples) after the lesions were covered by the antibacterial temporary cement. For the remaining samples, some bacteria (5 to 80 counts per sample) were recovered, with one notable exception in which marginal leakage provided a bacteria count of 10(3). Bacteria counts ranging from 10(3) to 10(5) occurred in carious lesions covered by temporary cement without antibacterial agents, which indicated that temporary cement alone was not a potent disinfectant. CONCLUSIONS: The results of this study indicated that the antibacterial temporary cement can be useful for eradicating bacteria from carious lesions of prepared abutments.

Adult↗