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At least 325 records · Page 18Linked to original sources
PubMed2006

Use of CVDentUS diamond tips for ultrasound in cavity preparation.

AIM: The aim of this study was to evaluate the use of CVDentUS tips for preparing cavities with ultrasound by dentists certified to use the Chemical Vapor Deposition (CVD) system. METHODS AND MATERIALS: One thousand sixty (1060) questionnaires were sent via e-mail inquiring about the use of the system with regard to the indication for use, need for anesthesia, final form of cavity preparation, and tip wear. RESULTS: Of the valid answers, 81.4% of the dentists used this system for tooth preparation in up to 60% of cases treated. For these procedures, 17.8% did not require use of local anesthesia while using the system. The final form of preparation compared to high speed diamond tips was considered to be more conservative by 48.3% of the certified professionals. With regard to wear, tip and/or adapter fractures, and low cutting speed, 44.4% of users reported problems. DISCUSSION: The CVD system seems to be used for tooth cavity preparation by the majority of the certified dentists. This is due to the resultant conservation of tooth structure despite the necessity of anesthesia and the limitations with regard to the lack of cutting efficiency of CVDentUS and tip wear. CLINICAL SIGNIFICANCE: The CVD system seems to present limitations with regard to cutting efficiency, wear, and the use of anesthesia in a majority of restorative procedures.

Dental Cavity Preparation↗
PubMed2006

Axial-wall inclination angle and vertical height interactions in molar full crown preparations.

OBJECTIVE: This study has been designed to evaluate the interaction of axial wall heights with inclination angles in full crown tooth preparations. The interaction of these parameters was related to the resulting preparation surface area. MATERIALS AND METHODS: A right regular pyramid was used to simulate a single mandibular molar preparation with known convergence angles and vertical heights. Various combinations of these two variables allowed the calculation of surface areas with a formula for the area of a pyramid and right triangles through trigonometric manipulations. The pyramidal model system had a 9-mm square base with vertical heights from 3- to 5-mm and single-side inclination angles from 2 to 25 degrees. The occlusal surface was a flat, square or rectangular surface and was included in the total area. RESULTS: A percentage of surface area lost or gained served as the dependent variables. The significance levels were set at 10.0% or greater magnitude of loss/gain in a surface area compared to the ideal 2 degree-level. Significant area loss was demonstrated in all alpha-level comparisons. The largest change was found in the 5-mm height grouping compared to the 3-mm height grouping, -36.6% difference between groups at the 2 degree-level. CONCLUSIONS: Axial single-side inclination angles greater than 10 degrees in 3- and 4-mm height-molars are detrimental to maximum surface area in full crown restorations. The 5-mm axial wall height with < or = 10 degree single wall has been shown to maximize the luting agent surface area between restoration and tooth structure.

Crowns↗
PubMed2003

In vitro marginal fit of three all-ceramic crown systems.

STATEMENT OF PROBLEM: Studies on marginal discrepancies of single restorations using various systems and materials have resulted in statistical inferences that are ambiguous because of small sample sizes and limited numbers of measurements per specimen. PURPOSE: The purpose of this study was to compare the marginal adaptation of single anterior restorations made using different systems. MATERIAL AND METHODS: The in vitro marginal discrepancies of 3 different all-ceramic crown systems (Celay In-Ceram, conventional In-Ceram, and IPS Empress 2 layering technique), and a control group of metal ceramic restorations were evaluated and compared by measuring the gap dimension between the crowns and the prepared tooth at the marginal opening. The crowns were made for 1 extracted maxillary central incisor prepared with a 1-mm shoulder margin and 6-degree tapered walls by milling. Thirty crowns per system were fabricated. Crown measurements were recorded with an optical microscope, with an accuracy of +/-0.1 microm, at 50 points spaced approximately 400 microm along the circumferential margin. The criterion of 120 microm was used as the maximum clinically acceptable marginal gap. Mean gap dimensions and standard deviations were calculated for marginal opening. The data were analyzed with a 1-way analysis of variance (alpha=.05). RESULTS: Mean gap dimensions and standard deviations at the marginal opening for the incisor crowns were 87 +/- 34 microm for control, 83 +/- 33 microm for Celay In-Ceram, 112 +/- 55 microm for conventional In-Ceram, and 46 +/- 16 microm for the IPS Empress 2 layering technique. Significant differences were found among the crown groups (P<.05). Compared with the control group, the IPS Empress 2 group had significantly smaller marginal discrepancies (P<.05), and the conventional In-Ceram group exhibited significantly greater marginal discrepancies (P<.05). There was no significant difference between the Celay In-Ceram and the control group. CONCLUSION: Within the limitations of this study, the marginal discrepancies were all within the clinically acceptable standard set at 120 microm. However, the IPS Empress 2 system showed the smallest and most homogeneous gap dimension, whereas the conventional In-Ceram system presented the largest and more variable gap dimension compared with the metal ceramic (control) restoration.

Aluminum Oxide↗
PubMed1999

Full-ceramic CAD/CIM anterior crowns and copings.

The purpose of the investigation was to examine the marginal and internal fit of Cerec anterior crowns and crown copings. The marginal and internal fit of Cerec anterior crowns (n = 18) and copings was examined on each of six anterior model tooth preparations, with different types of butt-margin crown preparation design on different teeth: 1.) straight flat (tooth 22), 2.) following the CEJ with mid-approximally steep curvature angles of 90 degrees mesial and 40 degrees distal (tooth 21) and 3.) same as 2, but with obtuse angles of 130 degrees and 150 degrees (tooth 41). The anterior crowns were machined on Cerec 2 units using Mark II ceramic (Vita), and the Cerec copings using In-Ceram Spinell (Vita). Laboratory slip-cast In-Ceram spinell anterior crown copings served as controls (n = 18). All reconstructions were seated (with adhesive) on the preparations, and the width of the marginal interface was measured circumferentially using SEM at 150x magnification. After cross-sectioning all samples in the bucco-oral direction, the internal fit was measured using this same technique. The marginal width of computer machined Cerec CAD/CIM anterior crowns (59.9 +/- 5.6 microns) was significantly (p < 0.01) lower than that of machined (73.4 +/- 12 microns) and slip-cast In-Ceram spinell copings (75.5 +/- 17 microns). The internal fit values of the slip-cast copings (94.1 +/- 20 microns) were significantly (p < 0.001) lower than those of the Cerec Mark II anterior crowns (141.3 +/- 21 microns) and copings (146.8 +/- 17 microns). Cerec CAD/CIM machined anterior full-ceramic crowns and copings showed excellent fit in comparison with slip-cast In-Ceram spinell copings. In terms of the marginal and internal fit, there were no significant differences (p > 0.05) between the different butt-margin preparation designs. Selected clinical cases demonstrate the high esthetics of anterior Cerec crowns.

Acrylates↗
PubMed1988

Tooth-colored inlays and onlays.

Today's dental patient concerned about attractive restorations is looking for a dentist who incorporates the newest and best techniques into practice. This article discusses a newer concept that pleases both the patient and dentist: restorations that are bonded into acid-etched tooth preparations with composite resin cement--tooth-colored inlays and onlays. Basic questions asked by practitioners about these esthetic restorations are addressed; characteristics, performance expectations, comparisons with cast gold inlays and onlays, and comparisons with amalgam are presented, in addition to other relevant information for today's dental practitioner.

Apatites↗
PubMed2006

A comparison of the visual and technical assessment of preparations made by dental students.

The preparation of acrylic teeth in a simulated clinical environment (phantom head) plays an essential role in pre-clinical dental education where evaluation is performed visually by instructors. The aim of this investigation was to verify the quality criteria of a tooth preparation for a metal-ceramic crown (tooth No. 21) with the help of digital measurement. Thirty-six acrylic teeth were prepared by students and one tooth was prepared ideally by a trained dentist: These were examined and compared. Five experienced instructors independently assessed the quality criteria with the use of a criterion list. Afterwards, the teeth were scanned with the 3D-laser scanner 'es1' (Etkon Company, Munich, Germany). The calculation of the correlation coefficient demonstrated a satisfactory correlation between visual and digital rating concerning convergence angle, shoulder width and occlusal reduction. Greater differences between experimental groups were observed with regards to other criteria on the applied criterion list. A directed calibration of the evaluators and a re-evaluation of some measurements would be necessary to gain more precise results.

Computer-Assisted Instruction↗
PubMed1997

Crown foundations with a custom matrix, composites, and reverse carving.

This article describes a restorative technique for the formation of composite cores for artificial crowns. The procedure uses a semirigid matrix with reverse carving to form the cores on substantially compromised teeth. The matrix allows the placement of the composite under pressure to reduce voids and gaps and permits completion of multiple cores simultaneously. Reverse carving enables development of a common axis for multiple cores. The dentist can perform the tooth preparation for the crown at the time of the core restoration. The effort commonly applied to developing tooth morphologic features in the core can be invested instead in the formation of the interim restoration. The remaining tooth structure, pin or post placement, and location of the finish line can be evaluated with the insight of a crown foundation and not merely as a traditional restoration.

Composite Resins↗
PubMed2005

Quantitative evaluation of axial wall taper in prepared artificial teeth.

The purpose of this study was to quantitatively evaluate the axial wall taper of prepared artificial teeth using a non-contact three-dimensional shape measuring system. A total of 54 artificial teeth prepared by pre-clinical dental students for complete cast restorations were evaluated. For quantitative analysis, five cross sections were computer-graphically placed perpendicularly to the z-axis. The surface coordinate values (x, y, z) of each cross section were converted into polar coordinate values (r, theta), which were then graphically rendered to a two-dimensional plane. At four points, each 90 degrees from the distal center point of the cross section, the axial wall taper was quantitatively calculated using a formula based on the differences in radius between the highest and lowest positions of the cross sections of the prepared tooth. The average calculated taper was 5.8 degrees in the distal region, 21.7 degrees in the buccal region, 14.9 degrees in the mesial region and 12.5 degrees in the lingual region. These results suggest that the axial wall taper of prepared teeth can be quantitatively evaluated using this measuring system.

Computer Graphics↗
PubMed2004

Clinical considerations for adhesive bridgework.

Many dental practitioners do not use adhesive bridges because of concerns over high failure rates. Techniques for these restorations should be based on the fundamental principles of bridge design which require rigid, accurately fitting frameworks and careful control of the occlusion. The abutments generally require little if any tooth preparation. Greater security will result from more extensive coverage of abutment teeth: the routine use of relative axial tooth movement is a predictable method for creating the space that this approach requires.

Cementation↗
PubMed2004

Fracture resistance of metal-free composite crowns-effects of fiber reinforcement, thermal cycling, and cementation technique.

STATEMENT OF PROBLEM: The improved mechanical properties of contemporary composites have resulted in their extensive use for the restoration of posterior teeth. However, the influence of fiber reinforcement, cementation technique, and physical stress on the fracture resistance of metal-free crowns is unknown. PURPOSE: This in vitro study evaluated the effect of fiber reinforcement, physical stress, and cementation methods on the fracture resistance of posterior metal-free Sinfony crowns. MATERIAL AND METHODS: Ninety-six extracted human third molars received a standardized tooth preparation: 0.5-mm chamfer preparation and occlusal reduction of 1.3 to 1.5 mm. Sinfony (nonreinforced crowns, n=48) and Sinfony-Vectris (reinforced crowns, n=48) crowns restoring original tooth contour were prepared. Twenty-four specimens of each crown type were cemented, using either glass ionomer cement (GIC) or resin cement. Thirty-two crowns (one third) were stored in humidity for 48 hours. Another third was exposed to 10,000 thermal cycles (TC) between 5 degrees C and 55 degrees C. The remaining third was treated with thermal cycling and mechanical loading (TCML), consisting of 1.2 million axial loads of 50 N. The artificial crowns were then vertically loaded with a steel sphere until failure occurred. Significant differences in fracture resistance (N) between experimental groups were assessed by nonparametric Mann-Whitney U-test (alpha=.05). RESULTS: Fifty percent of the Sinfony and Sinfony-Vectris crowns cemented with glass ionomer cement loosened after thermal cycling. Thermal cycling resulted in a significant reduction in the mean fracture resistance for Sinfony crowns cemented with GIC, from 2037 N to 1282 N (P=.004). Additional fatigue produced no further effects. Fiber reinforcement significantly increased fracture resistance, from 1555 N to 2326 N (P=.001). The minimal fracture resistance was above 600 N for all combinations of material, cement and loading. CONCLUSION: Fracture resistance of metal-free Sinfony crowns was significantly increased by fiber reinforcement. Adhesive cementation may be recommended to avoid cementation failure.

Air Abrasion, Dental↗
PubMed2000

Pulp reactions to different preparation techniques on teeth exhibiting periodontal disease.

To evaluate the histopathological outcome of two preparation techniques (featheredge preparation/shoulder preparation) on teeth exhibiting pulp reactions due to age and periodontal disease, 11 teeth were prepared for full veneer crowns. Laboratory made resin crowns were fixed with a zinc phosphate cement for a period of 90 days. After extraction, adjacent pulpal areas were histopathologically rated according to the BRD criteria comprising the parameters (i) Bacterial invasion, (ii) Regenerative parameters, (iii) Degenerative parameters. Degenerative reactions were more correlated with tooth preparation than with advanced periodontal disease. The severity of endondontal reactions depends more on remaining dentin thickness than on the type of preparation.

Acrylic Resins↗
PubMed2004

Effectiveness of preparation guidelines for an all-ceramic restorative system.

PURPOSE: To evaluate, in a clinical field-test, the implementation of manufacturer's preparation guidelines for the all-ceramic CICERO system. METHODS: General dental practitioners from the northwest region of The Netherlands were asked to make complete crown preparations in accordance with the specific guidelines of the CICERO system. 3,446 tooth preparations were evaluated with regard to shoulder angle, shoulder width and top angle. They were quantified using a special software program. The results were compared with criteria defined in the manufacturer's preparation guidelines. RESULTS: On a multivariate level all (main and interaction) effects were significant (P < 0.05) excluding the interaction effect of the location of measurement on the tooth by the upper or lower jaw. The value of the shoulder angle showed a strong relation with the tooth position in the mouth as well as with the location of measurement on the tooth. The shoulder width in the lower jaw was significantly smaller when compared to the width in the upper jaw. The shoulder width of the lower incisors was the smallest and also showed the largest variance per tooth. On a group level (incisor, cuspid, premolar, molar), except for the shoulder width of the lower incisors, the average values of all preparation parameters were within the borders as defined in the preparation guidelines of the manufacturer. However, on an individual tooth level nearly all preparations showed to have one or more locations with imperfections.

Bicuspid↗
PubMedDate not supplied

Pulp-dentin biology in restorative dentistry. Part 2: initial reactions to preparation of teeth for restorative procedures.

Pulpal complications involving inflammation, degradation, and necrosis are the result of a series of traumatic injuries. The restorative dentist must minimize the trauma to dentin and pulp inflicted during clinical procedures, including that inflicted during tooth preparation. Part 11 of this series discusses the structural and physiologic changes in the pulp-dentin complex that result from crown and cavity preparation and the clinical implication of these changes.

Acid Etching, Dental↗
PubMedDate not supplied

[Hemodynamics in the pulp of abutment teeth after their preparation for metal-ceramic denture restoration].

The paper presents the results of functional examination of pulpal and periodontal vessels in 57 patients who underwent preparation of supporting teeth for making cermet dentures. Pulpal hemodynamics was studied by using rheodentography before and 1, 3, 7, 14, 21, and 28 days after tooth preparation. After preparation, the tooth pulp exhibited inflammatory sings which gradually alleviated and 14-28 days later there was stabilization of rheographic parameters of regional hemodynamics. In patients with intact periodontium, circulatory recovery occurred on days 14-21, while in those with periodontitis it took place on days 21-28.

Dental Abutments↗
PubMed2004

The effect of a resin-based sealer on crown retention for three types of cement.

STATEMENT OF PROBLEM: In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products. PURPOSE: This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents. MATERIAL AND METHODS: Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test. RESULTS: Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement. CONCLUSIONS: Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.

Analysis of Variance↗
PubMed2000

Enhanced resilience and esthetics in a Class IV restoration.

The purpose of this article is to give the reader a better understanding of the complex restorative challenge in achieving true harmonization of the primary parameters in esthetics (i.e., color, shape, and texture) represented by the replacement of a single anterior tooth. The case presented demonstrates the restoration of a Class IV fracture taking esthetic consideration of the anatomic variations of the adjacent teeth to produce a direct composite resin in harmony with the surrounding dentition. The basic procedure includes tooth preparation, development of the body layer, internal characterization with tints, development of the artificial enamel layers, shaping and contouring, and polishing. In understanding the total morphology of a tooth and using natural teeth as the basis for morphological thinking, the clinician possesses the knowledge to create restorations with a more natural appearance. Use of a recently developed optimized-particle composite and this morphological thinking allowed the author to achieve a restoration in harmony with the surrounding dentition. Continuing technological breakthroughs allow the clinician to implement and maximize new products to attain more predictable and esthetic results as demonstrated by this methodological protocol of incremental application of composite resins and modifiers to transform the Class IV fracture into a final restoration that mimics nature.

Adult↗
PubMed2004

Cervical margin design with contemporary esthetic restorations.

The contemporary dentist has a wide variety of options to use in the restoration of extensively damaged or previously restored teeth. Metal-ceramic and all-ceramic crowns are frequently used to restore esthetics and function. One of the essentials for success with either option is proper tooth preparation, which includes proper selection and preparation of the cervical margin of the preparation.

Ceramics↗
PubMed2000

Method for marginal measurements of restorations: accessory device for toolmakers microscope.

Standardization of measurements for marginal fit of castings is critical. This study describes the fabrication of a device that allowed fixation of specimens on a Toolmakers microscope with identical conditions according to tri-dimensional positioning of specimens, measuring location, and seating force. The device also allows mapping of the marginal discrepancies on the entire marginal perimeter of the tooth preparation.

Calibration↗