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At least 73 records · Page 4Linked to original sources
PubMed2005

Expression of osteocalcin and Jun D in the early period during reactionary dentin formation after tooth preparation in rat molars.

We examined, in rats, the expression of osteocalcin and Jun D in the early stage of reactionary dentin formation after tooth preparation and the accompanying morphological changes. Reverse transcription/polymerase chain reaction analysis revealed strong expression of osteocalcin mRNA in pulp tissue at 2 and 3 days post-preparation compared with that in control teeth. Light microscopy demonstrated that, at the dentin-pulp interface, damaged odontoblasts were detached from the dentin matrix immediately after preparation, with neutrophils lining the dental surface after 1 day. After 2-3 days, differentiated odontoblasts appeared at the interface. Reactionary dentin with tubular structures was formed under the cavity after 10 days. Immunoelectron microscopy showed that trace amounts of osteocalcin were expressed in odontoblasts at 2 days post-preparation, and abundant osteocalcin was found in the highly developed Golgi apparatus and granules at 3 days post-preparation. Osteocalcin was also found on type I collagen fibrils in newly formed predentin. The existing dentinal tubules were filled with osteocalcin-coated type I collagen fibrils. We observed, by immunohistochemistry, that Jun D was temporally expressed in the nuclei of the odontoblasts at 1 and 2 days post-preparation. However, no Jun D was found in the dental pulp cells at any other time or in control teeth. Thus, osteocalcin expression is correlated with reactionary dentin formation, and Jun D is associated with osteocalcin expression in odontoblasts. Osteocalcin may also serve as an obturator of the dentinal tubules to protect dental pulp vitality against external irritants after preparation.

Animals↗
PubMed1996

Surface roughness of dentin after tooth preparation with different rotary instrumentation.

Although surface finish can be a critical variable in clinical performance, there is a dearth of information regarding surface characteristics of teeth prepared for artificial crowns. This study characterized teeth prepared for complete cast restorations using three representative types of rotary instruments. One hundred and five standardized tooth preparations for complete crowns were performed using a modified milling machine on extracted human teeth with diamond, tungsten carbide, and tungsten carbide finishing burs of similar shape (n = 35). The prepared dentin was analyzed with a surface profilometer and a scanning electron microscope (SEM). Differences between rotary instrument groups were determined with parametric ANOVA and Tukey's Studentized Range (HSD). Statistically significant differences in the surface topography of prepared teeth were open. Mean surface roughnesses (Ra) were 8.6 and 6.8 mum for teeth prepared with diamond and tungsten carbide burs. Teeth completed with finishing burs appeared to result in a smoother surface (1.2 mum).

Analysis of Variance↗
PubMed1990

Getting the "feel" of it: the non-visual component of dimensional accuracy during operative tooth preparation.

The purpose of this study was to determine what portion of a dentist's dimensional accuracy in the use of the high-speed rotary handpiece for operative tooth preparation can be attributed to visual control during the preparation. Dental students in a performance simulation laboratory recorded an 87.5 per cent handpiece control accuracy during a maxillary occlusal preparation, using normal intraoral mirror vision. When visual contact was eliminated during preparation, the accuracy declined only 13 per cent, to 74.5 per cent. The results of this study lend support to the development and use of dental clinical simulations and approaches which encourage proprioceptive and other non-visual skills, in addition to visual skills, during preclinical and clinical dental education.

Dental Cavity Preparation↗
PubMed1994

Seven-step tooth preparation for a gold onlay.

This article describes seven sequential steps for an onlay preparation: penetration and extension, axial reduction, cuspal reduction, supragingival shoulder, supragingival bevel, intracrevicular bevel, and finishing. Details and rationale of each step are reviewed, and the number of burs and diamond stones are minimized. The tooth preparation is designed to provide maximal retention with innocuous occlusal forces, esthetics, and preservation of tooth structure. The slip joint on the facial and lingual walls of the proximal boxes facilitates seating of single- or multiple-unit castings. These seven sequential clinical steps for a gold onlay have been successful.

Dental Cavity Preparation↗
PubMed1984

Multiple handpiece delivery system for tooth preparation.

A cart-type handpiece delivery system has been modified to provide the operator with five high-speed and one low-speed air-driven handpieces. This relatively simple dental unit is versatile and can be adapted to a variety of tooth preparation techniques. The product of organization is efficiency, which encourages optimum results with an economy of actions and a reduction of stress.

Dental Cavity Preparation↗
PubMed1994

The periodontal-restorative interface in fixed prosthodontics: tooth preparation, provisionalization, and biologic final impressions--Part II.

The delicate dento-gingival attachment apparatus must be treated with utmost care during all phases of preparation in the crevicular region. There is little room for error within these minute dimensions. The learning objective of this article is to encourage the dentist to be ever vigilant when approaching the subcrevicular tissues during biomechanical tooth preparation, provisionalization, biologic final impressions, and final cementation. Part I, published in the January/February, 1994, issue of PP&A, discussed the emergence profile, retraction, preparation modalities, and provisionalization. Part II discusses final impressions and casts derived from information provided by morphologically correct provisionals, surgically directed provisionalization, and final functional and aesthetic rehabilitative results.

Adult↗
PubMed1990

Predicting esthetics of laminate veneers without tooth preparation.

High expectations may contribute to stress in the patient and dentist during dental treatment. Esthetic and restorative results can be predicted for laminate veneers by using a powder blower and a liquid dispenser preoperatively to form self-cured resin veneers. Trial veneers are formed in a precision "salt and pepper" technique that conserves materials and time. The trial veneers are placed, without tooth preparation, on the treatment site so that the patient can preview the planned treatment and so that the dentist can explain proposed treatment in a reversible procedure. This may circumvent misunderstandings between dentist and patient and allow the consideration of alternate treatment plans.

Acrylic Resins↗
PubMed1992

An evaluation of smear layer with various desensitizing agents after tooth preparation.

According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded clinically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin.

Adult↗
PubMedDate not supplied

The periodontal-restorative interface in fixed prosthodontics: tooth preparation, provisionalization, and biologic final impressions. Part I.

The delicate dento-gingival attachment apparatus must be treated with utmost respect during all preparational maneuvers in the crevicular region. There is little room for error within these minute dimensions. To avoid irreparable harm during chemo-mechanical manipulation of the attachment apparatus, the dentist must always think on a histologic level in order to respect the cellular integrity of the periodontium. The learning objective of this article is to encourage the dentist to be ever vigilant when approaching the subcrevicular tissues during biomechanical tooth preparation, provisionalization, biologic final impressions, and final cementation. Part I discusses the emergence profile, retraction, preparation modalities, and provisionalization; it is presented in this issue. Part II will cover final impressions and casts, derived from information provided by morphologically correct provisionals, surgical provisionalization, and final rehabilitative results; it will appear in the April, 1994, issue of PP&A.

Crowns↗
PubMed2005

The in vitro performance of laser fluorescence and caries-detector dye for detecting residual carious dentin during tooth preparation.

OBJECTIVE: The aim of this in vitro study was to compare the performance of a laser fluorescence device (DIAGNOdent) and a caries-detector dye for detecting residual dentinal caries. METHODS AND MATERIALS: Forty extracted human molar teeth with deep dentinal carious lesions on their approximal surfaces were used for the study. The caries were removed by a new chemomechanical system, Carisolv. Three independent observers checked all cavities for residual caries using caries-detector dye and DIAGNOdent. The presence or absence of residual caries was verified using polarized light microscopy as the gold standard. Three observers recorded two different measurements at the same site after 2 weeks to determine intra- and interexaminer reproducibility of the DIAGNOdent. RESULTS: Average kappa values of 0.61 for interexaminer reproducibility and 0.94 for intraexaminer reproducibility were determined. The specificity of caries-detector dye was found to be 100% and the specificity of the DIAGNOdent was 86%. CONCLUSION: Although DIAGNOdent showed greater sensitivity than caries-detector dye (P < .05), low sensitivity values for each diagnostic system may lead to teeth with residual caries being undetected. Therefore, it might be advisable to reconsider the criteria for detecting residual caries during tooth preparation.

Coloring Agents↗
PubMed2005

Dentin exposure in tooth preparations for porcelain veneers: a pilot study.

STATEMENT OF PROBLEM: The various clinical techniques available for even reduction of a tooth surface to receive a porcelain veneer restoration do not produce a consistently even conservative reduction. In addition, it is not known which technique is most conservative of enamel. PURPOSE: The purpose of this pilot study was to assess the effectiveness of 3 clinical techniques, namely, dimple, depth groove, and freehand, in producing an intraenamel preparation. The relation between overpreparation beyond the commonly accepted depth of preparation of 0.5 mm and dentin exposure was also examined. MATERIAL AND METHODS: A single operator prepared 3 groups of 5 extracted maxillary central incisors to a depth of 0.5 mm using dimple, depth-groove, and freehand methods of tooth preparation. The prepared teeth were scanned using an x-ray microtomography scanner. The reconstructed images were studied using software that provided a volume-rendering routine so that, by choosing suitable x-ray linear attenuation coefficient thresholds, enamel (2.78 cm(-1) at 40 keV) and dentin (1.63 cm(-1) at 40 keV) surfaces could be viewed. The percentage area of enamel conserved was analyzed from these images. Coordinate metrology was used to produce color-coded images depicting the depth of preparation. The Kruskal-Wallis test was used to determine the statistical significance (alpha=.05) in the difference between the mean percentage area of enamel conserved in the 3 technique groups. The coordinate metrology and x-ray microtomography images were visually compared to study the correlation between overpreparation and dentin exposure. RESULTS: The Kruskal-Wallis test did not demonstrate significant difference (P=.07) between the 3 techniques in conserving enamel. However, the dimple technique showed a greater trend to retaining a larger mean percentage area of enamel (77.5% +/- 14.2) compared to depth-groove (50.1% +/- 17.5) and freehand (76.8% +/- 24.4) techniques. Preparation depth in the range of 0.4 to 0.6 mm was largely seen to be intraenamel, except in the cervical region. CONCLUSION: Within the limitations of this pilot study, the 3 different techniques tested did not differ significantly in conserving enamel.

Dental Porcelain↗
PubMed2006

The bonding area of intra- and extra-coronal tooth preparations.

PURPOSE: To assess the accuracy of preparation surface area measurements (mm2) using the Cerec digital mouth camera in vitro and to analyze a collection of 514 Cerec camera in vivo optical impressions of preparations from 274 patients according to the size of preparation/bonding area (mm2) METHODS: The surface area (mm2) of model preparations with known dimensions namely of one occlusal (1) and one mesio-occluso-distal (2) cavity as well as of one central incisor (3) and one molar (4) crown preparation was calculated from linear (a) design dimensions, (b) slide-gauge and (c) coordinate-measuring-machine data as benchmark measurements and from repeated (n=10) (d) laser-scan (control), (e) Cerec-camera mounted on a support, (f) handheld Cerec-camera measurements. Data of (d), (e) and (f) was statistically analyzed. From a collection of data sets clinically recorded with the Cerec camera, the surface areas of 514 preparations from 274 patients were analyzed according to the type of tooth and type of preparation. RESULTS: Occlusal cavity mm2 data 1(d) 48 +/- 0.4, 1(e) 48 +/- 0.2, 1(f) 48 +/- 0.6 and mod cavity mm2 data 2(d) 137 +/- 2, 2(e) 138 +/- 1, 2(f) 138 +/- 4 did not differ between (d), (e) and (f) (P> 0.05) confirming the hypothesis for inlay cavities. Incisor crown preparation mm2 data 3(d) 82+0.4 differed (P< 0.001) from 3(e) 85 +/- 0.2 and 3(f) 85 +/- 0.6 as well as molar crown preparation mm2 data 4(d) 133 +/- 0.6 differed by 3.5% (P< 0.001) from 4(e) 137 +/- 0.4 and 4f) 138 +/- 1. Clinical cavity and crown preparation area data obtained from in vivo Cerec camera recordings differentiated between type of tooth and type of cavity. 2D data of "classic", "reduced" and "endo" type crown preparations did not differentiate clearly.

Ceramics↗
PubMed1999

Survival of Dicor glass-ceramic dental restorations over 14 years. Part II: effect of thickness of Dicor material and design of tooth preparation.

STATEMENT OF PROBLEM: The influence of different restorative design features on the long-term survival of Dicor glass-ceramic restorations is not well understood. PURPOSE: This study examined the relationship of different types of restorations and methods of preparation with the survival of Dicor glass-ceramic restorations functioning in vivo. MATERIAL AND METHODS: A total of 1444 Dicor glass-ceramic restorations were placed on the teeth of 417 adults. Failure was defined as a restoration that required remake because of material fracture. Survival of restorations of different types and with different methods of preparation was described by using Kaplan Meier survivor functions. Statistical significance between restoration type and preparation method was determined with the log rank test. RESULTS: Probability of survival of a typical partial coverage restoration was 92% at 11.3 years. There was no statistically significant difference between the survival of inlay or onlay restorations. For the 91 cores used for pulpless teeth, none failed over a total cumulative monitoring period of 419 years. There was no significant difference in survival of acid-etched Dicor restorations that were placed on shoulder or chamfer preparations. Thickness measured at the midpoint of the labial, lingual, mesial, distal, and midocclusal surfaces did not relate to risk of failure. CONCLUSIONS: The majority of Dicor glass-ceramic partial coverage inlay and onlay restorations and cores survived over time. Survival of restorations with either chamfer or shoulder preparations did not differ whether the restoration was acid-etched. Thickness of the restoration measured at the midaxial point of each surface did not relate to survival.

Acid Etching, Dental↗