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PubMedDate not supplied

[Secondary caries as a problem].

A large number of the all operative work performed in a dental office is amalgam fillings. Secondary caries continuous to be a serious problem although amalgam has been improved to a large extent. All efforts that have been made to eliminate the problem of secondary caries associated with amalgam fillings have not been very successful so far. There is always a lack of permanent seal between restorations and the prepared tooth surfaces so that microleakage always exists. The purpose of this paper was to search the literature on the subject and find ways and attempts that have been made on the elimination of secondary caries. On the other hand was aimed to present and discuss the application of fluorides into the cavity preparation as a preventive method of eliminating secondary caries as well as the possible effects of fluorides on the dental pulp if they exist. The literature gives a lot of information on the subject and fluorides in the cavity before the filling insertion seems to be a safe and approved method against secondary caries. Regarding the effect of fluorides on the pulp it is indicated that when the proper agent and technique is used there is no any deleterious effect and the method is not contraindicated.

Dental Amalgam↗
PubMed1998

Tooth structure loss apical to preparations for fixed partial dentures when using self-limiting burs.

STATEMENT OF PROBLEM: Burs with guide pins may be used to limit the depth of tooth preparation for fixed partial dentures. The effects of guide pins on tooth structure apical to the finish line after tooth preparation for fixed partial dentures has not been recorded. PURPOSE: This in vitro study recorded loss of tooth structure within 1.0 mm apical to the finish line of teeth prepared with straight cylinder and tapered cylinder self-limiting burs and one conventional bur. MATERIAL AND METHODS: Forty-five extracted human teeth were randomly divided into three groups. The facial surface of each tooth was prepared with two types of diamond burs with guide pins and a conventional diamond for the control. The surface was profiled before and after tooth preparation. Profiled surfaces were analyzed and the groups were compared using analysis of variance and the Tukey-Kramer HSD test (alpha = 0.05). RESULTS: No significant difference was recorded between the control group and the group prepared with a round-ended tapered cylinder self-limiting pin. However, there was a statistically significant difference between the control and cylindrical pin groups, and between the two groups prepared with self-limiting diamonds. CONCLUSION: This study revealed abrasion apical to the finish line of the preparation in all groups. The cylindrical guide pin group exhibited the greatest loss of tooth surface.

Analysis of Variance↗
PubMedDate not supplied

A clinical study of the "open sandwich" technique in pediatric dental practice.

PURPOSE: This study evaluated the clinical efficacy of the "open sandwich" restoration for pediatric dental practice. METHODS: Three pediatric dentists used a standardized preparation and restorative technique to place the restorations. The prepared tooth was etched with a phosphoric acid semigel and rinsed. A resin modified glass ionomer (Fuji II LCor Photac-Fil) was placed short of the margins and then light cured. The resin modified glass ionomer was covered with an occlusal layer of a microhybrid flowable composite (Aeliteflo or Flow-it). The same preparation for the experimental restorations was used for the control conventional amalgam (Tytin) restorations. The restorations were evaluated at 6-month intervals and ranked with a modified United States Public Heath Survey (USPHS) scale as follows: Alfa: No discernible marginal opening or stain; Beta: Slight opening of margin discernible with dental explorer, but without stain; Charlie: Open margin and stain; Delta: Recurrent caries or restoration failure. Restoration failures were categorized according to etiology, pulpal necrosis, bruxism, marginal leakage, isthmus fracture, or adhesive failure. RESULTS: All recalled experimental restorations, except 8, were rated as either Alpha or Beta. Six failed due to isthmus fracture and 2 due to pulpal necrosis. Fifteen restorations had delaminating of the flowable composite from the resin modified glass ionomer. The use of the "open sandwich" technique compared favorably with a similar study using adhesive amalgam restorations. CONCLUSIONS: The "open sandwich" technique can be successfully used in a pediatric dental practice.

Acid Etching, Dental↗
PubMed1993

Dentin: microstructure and characterization.

Dentin consists of several identifiable structures: tubules with cell processes and fluid; highly mineralized peritubular dentin; and intertubular dentin consisting mainly of collagen and deposited apatite. The structural organization and microstructural variations reflect formative influences, such as tooth size and shape, and alterations caused by age, insult, and disease. However, details of structure-chemistry-property relationships for this anisotropic biologic composite are limited. Materials scientists are focusing on an array of new spectroscopic, analytical, and imaging techniques that are yielding improved understanding of structural variations and their dependence on specimen preparation, tooth type, location, storage conditions, and chemical and physical modifications. Such studies should lead to the major refinements in structure-properties models for dentin that are required for continued advances in dental composite resins and adhesives.

Biomechanical Phenomena↗
PubMedDate not supplied

Treatment of loss of tooth substance using dentine-bonded crowns: report of a case.

This article discusses the treatment of a bulimic patient with severe tooth substance loss. The patient was provided with dentine-bonded crowns in view of the need for only minimal tooth preparation, their potential for good aesthetics and good patient acceptance. The crowns have performed satisfactorily in clinical service for 4 years.

Adult↗
PubMedDate not supplied

[Microbial permeability of dentin].

This is a review of the literature about the contemporary aspects of microbial permeability of dentin. They are discussed the factors that are responsible for this question and analytically: the structure of dentin, the composition of dentin in organic and inorganic ingredients, the response mechanisms of dentin, that is the irritation dentin and sclerotic dentin, the hypermineralized zone under carious lesions, the role of saliva and dentinal fluid, the role of pulp and its microcirculation against the invasion of microbes and, the role of smear layer. Also this article refers to the immunological reaction of the pulp and finally to the role of dentist in the permeability of dentin, because the more conservative is a tooth preparation the less is the permeability of dentin. In conclusion, the microbial permeability of dentin is a very complicated biological phenomenon that needs more study and further investigations.

Dental Pulp↗
PubMed1994

A technique for developing a master cast with previously made dies.

This article describes a technique for preparing final working casts to be used in the laboratory phase of restorative treatment. The goal is to produce accurate working casts that have stable dies which are easily removed from the base and reliably replaced. Most casts with removable dies are made from a single master impression. However, individual dies are sometimes made previously from individual tooth (preparation) impressions. In such cases, transfer copings are required to relate the dies and produce the final working cast. Hollow plastic casting sprues are used as temporary dowels in this technique until a transfer coping pickup impression has been made. After the dies are seated and secured in the transfer coping pickup impression, the plastic casting sprues are replaced with conventional brass dowel pins. This technique ensures well-placed dowel pins that will facilitate easy and accurate withdrawal and replacement of the dies.

Dental Casting Technique↗
PubMed1993

Effect of luting media on the compressive strengths of two types of all-ceramic crown.

This study evaluated the effect of selected luting media on the compressive strength of two types of all-ceramic crown. Tooth preparation was standardized; each preparation had a shoulder width of approximately 1.2 mm, and all internal preparation angles were rounded. Hi-Ceram and Dicor all-ceramic crowns were fabricated and cemented into the preparations with zinc phosphate, glass-ionomer, or composite resin cement. Coronal compressive fracture strengths were determined, using a set of unrestored teeth as a control. There were no statistically significant differences among the mean compressive strengths of the three luting media, and there was no statistically significant difference between the mean compressive strength of Dicor and that of the natural tooth control.

Aluminum Oxide↗
PubMed1996

The effect of marginal thickness on the distortion of different impression materials.

An impression of the margins of a prepared tooth and adjacent gingival sulcus must be of sufficient thickness to withstand distortion and tearing when the impression is removed from the mouth. The purpose of this study was to compare the dimensional accuracy of Elite, Examix, and Express polyvinyl siloxanes; Permadyne polyether; and Permlastic polysulfide elastomeric impression materials. These materials were used to make impressions of a metal model that simulated prepared abutments with gingival sulci of various widths. A traveling microscope was used to measure the abutments and impression widths, and the number of defects in each impression was recorded. Between 70% and 100% of the abutment impressions with sulcular widths of 0.05 mm exhibited defects, which prevented accurate measurements in this group. Express material demonstrated a high number of defects in the 0.10 and 0.16 mm sulcular width groups. No great difference in average maximum distortion values or coefficients of variation (CV) were detected among the materials used to make impressions of abutments with sulcular width groups of 0.2 to 0.4 mm. For the sulci of 0.16 mm and less, Examix and Permiastic materials exhibited distortion and a CV comparable to the impressions of the wider sulcular groups, whereas Elite and Permadyne showed greater distortions and CVs. The differences were not statistically significant (analysis of variance) because of the larger CV among the groups. The larger coefficient of variation in the 0.1 and 0.16 mm sulcular width groups demonstrated inconsistencies in obtaining good impressions of abutments with such narrow sulcular widths.

Analysis of Variance↗
PubMed2001

Four-year clinical evaluation of posterior resin-based composite restorations placed using the total-etch technique.

PURPOSE: To report the 4-year clinical performance of posterior resin-based composite restorations placed using the total-etch technique. MATERIALS AND METHODS: Over a period of 1 year, 726 restorations (248 molars, 478 premolars; 260 Class I, 466 Class II; 540 replacements, 186 primary decay) were placed on conservative preparations, using the incremental placement technique in a clinical environment. Baseline data were collected, and the restorations were evaluated after 4 years. Z100 and Scotchbond Multi-Purpose (SBMP) (3M Dental Products, St. Paul, Minnesota) were used as the restorative system. The criteria evaluated were color match, marginal adaptation, anatomic form, cavosurface marginal discoloration, axial contour, interproximal contact, secondary caries, postoperative sensitivity, and tooth vitality. RESULTS: At baseline, 24% of the teeth restored presented postoperative sensitivity; 86% of the sensitive teeth were from the replacement group. At 4 years, all teeth were vital to cold test. Eighteen restorations (2.5%) presented clinically detectable marginal fracture. The shade was acceptable in all restorations. Cavosurface marginal discoloration was observed in 47 restorations (6.5% bravo scores). Axial contour, interproximal contact, and marginal adaptation received 100% alfa scores. No secondary caries was diagnosed in any of the teeth examined. None of the examined restorations required replacement. CLINICAL SIGNIFICANCE: Under controlled clinical conditions, posterior resin-based composite restorations placed with the total-etch technique and restorative Z100/SBMP have the potential to present a high success rate at 4 years. None of the examined restorations required replacement, and there was no clinically detectable wear in any of the restorations. Simultaneous etching of enamel and dentin followed by the application of a resin adhesive can be considered an adequate modality of pulp protection in nonexposed tooth preparations.

Acid Etching, Dental↗
PubMed2003

Etching with EDTA--an in vitro study.

In the present study, 25% EDTA, in gel form, was used to analyse its micromorphological effects on tooth surfaces with the objective to see the effectiveness of EDTA in etching so as to replace phosphoric acid as an etchant. EDTA has neutral pH (6.4 - 7.4) and is known to open & widen the dentinal tubules as well as remove the smear layer. An in vitro study was conducted on orthodontically extracted premolars with 25% EDTA as an etchant which was applied on prepared tooth surfaces for 15 seconds, 1 minute and 3 minutes. The effects of EDTA gel was observed under SEM and results tabulated and evaluated. There was statistically significant differences between the 3 etching time groups and the results indicate that etching with 25% EDTA for 15 seconds is inadequate. The best results were obtained in the 3 minute time etch group. The results so obtained can be attributed to the fact that EDTA acts selectively and/or requires more time for action.

Acid Etching, Dental↗
PubMed1990

[Composite resin inlays and onlays].

The establishment and development of composite resins has led to their use as a posterior restorative material. Although posterior composites have evolved considerably, both clinical studies and experience have confirmed that several problems still remain concerning their clinical properties and the relative complexity of handling the material. In order to resolve these problems, two different manufacturers have introduced composite resin systems for the fabrication of direct or indirect resin inlays and onlays which are cemented into the acid-etched preparation with a modified composite resin. Both systems are based on the same concept: the polymerization of the resin takes place out of the mouth in a special oven where a specific heat-curing procedure is followed. There is an essential difference between the two systems. When the direct resin system is used, the inlay is formed and partly light-cured into the tooth preparation, then it is removed for further polymerization. When the indirect system is used the procedure takes place in the lab where the inlay is formed on the die. This article presents both systems, the step-by-step procedure that has been followed in several clinical cases as well as their advantages and disadvantages.

Bicuspid↗
PubMed2003

The use of mineral trioxide aggregate to create an apical stop in previously traumatized adult tooth with blunderbuss canal. Case report.

The case presented here demonstrates an alternative to conventional treatments in managing a non-vital blunderbuss canal. The use of MTA (mineral trioxide aggregate) to establish an apical stop allows for expedient completion of root canal therapy with predictable results. Following root canal therapy, non-vital bleaching techniques may be employed, offering a means of restoring the tooth to its natural shade without the need for additional tooth preparation. Surgery is avoided, and the technique can easily be followed by the general practitioner.

Adult↗
PubMed1982

Effects of cement on crown retention.

This study indicates that the frequent clinical technique of permanently cementing a crown without removing all traces of a temporary ZOE cement from the tooth has no adverse effect on retention. Circumferential grooving of the tooth preparation did not significantly increase retention. In contrast, cutting a shallow groove in the crown significantly improved retention. Therefore, it would appear that the grooving of the gold casting might be advantageous in conditions where the crown restoration has minimal retention. Significant improvement in retention with grooving of the restorations was accompanied by a change in the location of the cement film. The cement was retained in the crown coronal to the groove rather than on the tooth. This finding was interesting, since previous retention studies showed that adhesive failure occurred at the metal-cement interface. From this data it appears that a primary factor of crown retention is the adhesion or mechanical interlocking of the cement to the crown. This would explain why small variations in cement film thickness, such as those due to the use of die relief, have little effect on retention. In view of these findings, the current concepts on cement retention and cement adhesiveness should be reevaluated.

Crowns↗
PubMed1996

Hardness, strength, and ductility of prefabricated titanium rods used in the manufacture of spark erosion crowns.

Depending on the size of the prepared tooth spark eroded and milled, Procera crowns (Nobelpharma AB, Göteborg, Sweden) are manufactured from one of five diameters of pure titanium rods. In this study microindentation hardness tests were performed on the outer 400 microns and center of 10 samples for each type of rod. Five tensile samples were also machined for each of the diameters and tested in tension in a universal testing machine. Cast titanium samples were similarly prepared and tested. Some significant differences in hardness and considerable differences in strength and ductility were identified between the prefabricated rods. In comparison, cast titanium was significantly harder and stronger but less ductile.

Analysis of Variance↗
PubMed1990

Clinical considerations of microleakage.

Most dental materials permit the microleakage of bacteria and bacterial products from oral fluids to reach dentin. Thus, an understanding of the clinical consequences of microleakage demands that we analyze the permeability characteristics of dentin. The more dentin surface that is exposed during tooth preparation, the greater the potential for microleakage. Thicker dentin is less permeable than thin dentin. Dentin over pulp horns is more permeable than central dentin. Similarly, the dentin making up axial walls is more permeable than dentin forming the pulpal floor of cavities. Coronal dentin is much more permeable than root dentin. In addition to the number of tubules per unit area, tubule diameter, and the location of the dentin in a tooth, another extremely important variable is the presence or absence of a smear layer. When smear layers are created, grinding debris are forced into each tubule to form a smear plug. Smear plugs are usually 1- to 2-microns long but may be 10-microns long. They are much longer than the smear layer thickness and they reduce dentin permeability more than the overlying smear layer. Smear layers constitute a natural cavity liner that reduces the permeability of dentin far more than any cavity varnish. However, its presence limits the strength of dentin bonding agents because of the relatively low cohesive forces holding the smear layer together and to dentin. If it is removed, the bond strengths of dentin adhesive resins increases, but removal also increases the potential liability for pulpal inflammation if the bond is not uniformly perfect.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Cements↗