Significance of thermal cycling in microleakage analysis of root restorations

Root surface cavities prepared in extracted premolars were restored with a selection of restorative materials. Prior to eosin dye immersion, one group of teeth was kept at constant temperature whilst another group underwent thermal cycling. The teeth were sectioned transversely through the restorations and an assessment of the degree of microleakage was used to compare the sealing ability of the selected materials. Eosin dye was able to discriminate more effectively between the microleakage behaviour of the restorative materials when samples were kept at a constant temperature.

Improving interproximal access in direct provisional acrylic resin restorations

A new technique that improves interproximal access in direct provisional acrylic resin restorations is presented. In this technique a clear Mylar strip is placed interproximally and lifted off with an overimpression prior to the beginning of the tooth preparation procedures. Preparation of the tooth and fabrication of the provisional restorations then continues in the usual direct manner. The Mylar strip, now embedded in the overimpression, becomes incorporated as a separator between the adjacent provisional restorations. The acrylic resin provisional restorations are easily snapped apart and finished individually. The advantages of the technique and the need for marginal perfection around the full perimeter of the tooth are also discussed.

Marginal adaptation of the Concept inlay system

PURPOSE

To evaluate the fit of the Concept inlay system in three clinically relevant cavity preparations (an occlusal, MO and MOD).

MATERIALS AND METHODS

The processed inlays were adjusted as needed and seated on master dies. The greatest marginal discrepancy occurring along each margin was recorded and evaluated.

RESULTS

The majority of the margins exhibited gaps in the range of 20-45 microns (statistically insignificant) with the exception of the distal margin of the MO which averaged approximately 80 microns and the buccal and lingual margins of the MOD which were approximately 70 microns (both statistically larger than the 20-45 microns range). This heat and pressure cured composite inlay system is capable of producing fairly closely fitting restorations.

Evaluation and treatment of bacterial microleakage

Recent data have shown a correlation between pulp response and material biocompatibility when microleakage is prevented. Considering vital dentin, the dentist must keep in mind that it is an extension of the pulp, presenting the first line of response to the consequences of microleakage. Healing of the dental pulp is ensured when a clinical seal is provided to prevent bacterial microleakage. Microleakage is a biological phenomenon with several important clinical implications. The affective component clinically presents as dentin postoperative hypersensitivity due to the episodic hydrodynamic fluid movement within the tubule complex. The effective component is the disease process which signals the dentin and pulp complex to respond by deposition of sclerotic and reparative dentin deposition. Uncontrolled microleakage generally produces patient pain as well as to later allow bacterial infection resulting in recurrent caries and pulp inflammation. The dynamic, permeable nature of the dentin interface allows residual bacteria to proliferate following cavity preparation. Following sterile operative procedures, bacteria have been shown to percolate into the cavosurface margin resulting in recurrent caries and pulp inflammation. This report considers biological data emphasizing the clinical necessity to provide a hermetic seal to prepared dentin to prevent both dentin hypersensitivity and pulp inflammation.

An update on conventional fixed bridgework. Part 4: Clinical techniques

The first three articles of this series have emphasized the importance of careful treatment planning in conventional fixed bridgework. In this, the fourth article, attention to detail continues to be the theme. The clinical procedures for fixed bridgework (tooth preparation, temporization, impression taking and occlusal registration) will be discussed.

Marginal breakdown of fired ceramic inlays cemented with glass polyalkenoate (ionomer) cement or resin composite

The marginal breakdown of fired porcelain inlays in vivo, luted with either a dual-cured resin composite or a glass polyalkenoate(ionomer) cement, was evaluated by scanning electron microscopy. Immediately following polishing (baseline) and after 1 year, replica impressions were made of the occlusal and proximal margins of two inlays, one cemented with the resin composite and the other with the glass ionomer cement, in each of 12 patients. At baseline the best marginal adaptation was observed along the proximal margins of the composite luted inlays, while occlusally glass ionomer luted inlays showed better marginal qualities than the composite luted inlays. At 1 year the composite luted inlays showed significantly better marginal adaptation than the glass ionomer luted ones at all interfaces. The greatest breakdown was observed occlusally, especially in the glass ionomer luted inlays. Gap sizes varied proximally between 83 and 100 microns and occlusally between 107 and 143 microns. Severe ditching was observed occlusally in the glass ionomer luted inlays. The overall marginal quality was significantly better for the inlays luted with the resin composite both at baseline and after 1 year.

Effectiveness of reflective wedges on the polymerization of composite resins

Polymerization of three composite resins was evaluated after they were light cured through one of four different reflective wedges. Other experimental variables were activation times and light units used. The same conditions were used for a control group, in which photoactivation was performed directly on the test specimens. Complete polymerization was never achieved when the curing light was directed through reflective wedges.

Effects of creep value and occlusal force on marginal adaptation of amalgam filling

Creep of amalgam is thought to be a factor determining poor marginal adaptation. Clarification of the relationship between creep of amalgam in the cavity and creep value (American Dental Association specification no. 1; ADA #1) is essential to an understanding of the mechanism of marginal fracture and service life. However, only elastic stress analyses of amalgam in a cavity have been reported in the dental field. Therefore, the creep of amalgam in a class I cavity was simulated by an axisymmetric elastic creep finite-element method. The stress and time dependencies of the creep rate of amalgam were incorporated into this calculation. Creep values of 1.0 and 3.0% (ADA #1) were selected as amalgam properties. When the occlusal force on the amalgam filling was assumed in the vertical direction along the axis of the tooth, the rate of extrusion and rate of opening of the gap at the cavity margin were revealed by the simulation. The computed results show that the gap and extrusion were developed in direct proportion of the creep value and proportionally with the square of the occlusal force. Simulated results are in agreement with clinical findings of the service lives of restorations, i.e., a poor adaptation to the margin can be seen for 4-to-10-year-old amalgam fillings.

Wear and marginal adaptation of composite resin inlays

MOD inlays were made with conventional, coarse hybrid, fine hybrid, and two microfilled composite resins. They were adhesively luted in six extracted human molars for each group and were subjected to longitudinal, in vitro testing. Final wear ranged from 46.8 +/- 18.6 microns for fine hybrid composite resin to 132.0 +/- 39.3 microns for conventional composite resin for the inlays and from 19.3 +/- 6.6 microns for homogeneous microfilled composite resin to 136.3 +/- 65.1 microns for coarse hybrid composite resin on enamel antagonists. The wear of the luting composite resins ranged from 11.2 +/- 11.2 microns to 20.0 +/- 23.6 microns. Marginal adaptation at the beginning of the test exceeded 88.7% of "continuous margin" for all groups in enamel. However, marginal gaps were evident in dentin without dentinal adhesives. Marginal adaptation of the microfilled composite resin inlays deteriorated during loads even when a dentinal adhesive and an inlay primer were used. The margins of the other composite resin inlays remained stable during load application.

Marginal fit of machine-milled titanium and cast titanium single crowns

Eighteen type IV dental stone dies were fabricated from a metal master die that replicated a tooth prepared to receive a metal ceramic crown. They were divided into three groups according to the type of crowns to be made: (a) machine-milled, spark-eroded titanium crowns (Procera); (b) cast titanium crowns; and (c) noble alloy crowns (as the control). The control specimens showed the smallest mean marginal openings at 25 microns and were significantly different from both the machine-milled crowns (54 microns) and the cast titanium crowns (60 microns). The two types of titanium crowns were not significantly different from each other.

Marginal accuracy of provisional restorations fabricated by different techniques

Provisional restorations were fabricated on a cast metal model and the resulting marginal discrepancies were measured. In the control group, the restorations were fabricated directly on the die and no coolant was applied. Five other methods of fabricating provisional restorations were evaluated. The mean marginal discrepancies were as follows: Control = 0.228 mm, In Situ (control plus coolant) = 0.196 mm, Removal (removed from die to polymerize) = 0.403 mm, On/Off (repeated removal/replacement) = 0.601 mm, Reline = 0.074 mm, and Indirect = 0.161 mm. The mean marginal discrepancy for the On/Off technique was significantly greater than that for all other techniques. The mean marginal discrepancy with the Removal technique was significantly greater than that with the Control, In Situ, Reline, and Indirect techniques. No significant differences were found between the Control, In Situ, Reline, and Indirect techniques.

Marginal adaptation of resin in relation to application technique and use of a dental adhesive system

Class V abrasion, erosion and caries lesions restored with composite resin seem to be more susceptible to microleakage, because the gingival margin is usually placed in cementum and/or dentine. The purpose of this study was to evaluate the microleakage, in vitro, of a dentinal bonding system using a technique of restoration with a positive and a negative control. This study was accomplished using extracted human teeth and dye penetration technique. The teeth were examined for microleakage after one month. It was concluded that in the gingival wall of the cavity microleakage was significantly reduced when the dentinal bonding agent and composite resin was placed and polymerized incrementally from enamel, to cementum.

The CELAY system: a comparison of the fit of direct and indirect fabrication techniques

CELAY is a machinable ceramic system that is capable of milling inlays, onlays, and veneers from prefabricated industrial ceramic blocks. Direct intraoral or indirect patterns may be used to make ceramic restorations. Scanning electron microscopy was used to analyze the marginal gap of restorations obtained with both methods. The direct fabrication technique yielded significantly better marginal gap sizes (P < .01) for the interproximal areas, while with the indirect (P < .01) fabrication technique the restorations showed significantly smaller marginal gaps at the occlusal borders. The clinical relevance of these findings and their possible applications for the development of a new impression material are discussed.

New adhesives in Class V restorations under combined load and simulated dentinal fluid

OBJECTIVES

This study compared the efficacy of three dentinal adhesives using the "all etch" technique (All-Bond 2, Bisco; Scotchbond MP,3M Dental Products Co.; OptiBond, Kerr) with a dentinal adhesive which still uses phosphoric acid to condition enamel and a self-etching primer for dentin (A.R.T.-Bond, Coltene/Whaledent).

METHODS

Eight V-shaped mixed Class V restorations were placed per group in extracted human premolars. The restorations were subjected to 1,200,000 mechanical occlusal cycles (max. force 49 N; frequency 1.7 Hz) and 3,000 simultaneous thermal cycles (5-50-5 degrees C). Dentinal fluid was simulated using 1:3 diluted horse serum and fed into the pulp chamber both during restoration and loading. Percentages of "continuous margin" were assessed on SEM replicas of enamel and dentinal margins at 200x magnification immediately before and after stressing, respectively.

RESULTS

No significant differences were observed before stress between the materials either in enamel or in dentin. After stress, however, OptiBond and A.R.T.-Bond performed significantly better in dentin than the two other adhesives (Kruskal-Wallis, Mann-Whitney; p < 0.05). Although high initial values were observed, All-Bond 2 and Scotchbond MP were not stress-resistant under simulated physiological conditions.

SIGNIFICANCE

The predicted clinical potential of All-Bond 2 and Scotchbond MP is inferior to that of OptiBond and A.R.T.-Bond.

Concepts of adhesion--a review

This paper reviews the current concepts of adhesion in restorative dentistry. Despite the numerous products available in the market, adhesion occurs in one or a combination of four ways. 1. Acid-etch and formation of resin tags. 2. Formation of strongly bonded surface precipitates, to which a resin can be chemically or mechanically bonded. 3. Chemical bonding to the inorganic components of tooth structure. 4. Chemical bonding to the organic components of tooth structure. With the success of the acid-etch technique for bonding to enamel, much of today's adhesive research has been directed towards bonding to dentine. None of the currently available dentine adhesives can achieve an ideal bond to dentine.

Clinical and laboratory evaluation of adhesive restorative systems

PURPOSE

To investigate the effectiveness of Clearfil Liner Bond, Gluma 2000, and Scotchbond Multi-Purpose when applied in combination with proprietary restorative resins in V-shaped circular cavities which were cut in incisors either centrally on the labial enamel surface (Type 1) or labially crossing the cemento-enamel junction (Type 2).

MATERIALS AND METHODS

Forty teeth scheduled for extraction for periodontal reasons were treated in vivo and another 40 teeth in vitro. The in vivo restored teeth were extracted after 3 months of clinical service and the in vitro treated samples were stored in water for 1 week and thermocycled 250 times between 5 degrees C and 55 degrees C, prior to a 24-hour immersion in 0.5% fuchsin tracer solution of all specimens, sectioning and scoring interfacial dye penetration.

RESULTS

ANOVA revealed no significant differences between all in vivo samples sites, all in vitro enamel sites and the apical Type 2 sites of the Gluma samples. In contrast, the apical Type 2 leakage of CLB and SMP was significantly more pronounced, although not statistically different from each other. The results of the short-term clinical performance of the three systems was moderately more favorable than the laboratory microleakage test results.

Microleakage of resin composites with wet versus dry bonding

PURPOSE

To evaluate the effects of wet and dry bonding on microleakage of Class V composite restorations.

MATERIALS AND METHODS

Cavity preparations were made in the buccal and lingual surfaces of 25 extracted human third molars. Half of each preparation was in enamel and the other half was in cementum/dentin. The preparations were randomly assigned to five groups for bonding with Scotchbond Dual-Cure (control), Scotchbond Multi-Purpose, or All-Bond 2. Scotchbond Multi-Purpose and All-Bond 2 were applied using both wet and dry techniques. All preparations were restored with a microfill composite after bonding. The specimens were thermocycled 300 times between 5 degrees and 55 degrees C and were subjected to a silver nitrate staining technique to detect marginal leakage.

RESULTS

Specimens bonded with All-Bond 2 and Scotchbond Multi-Purpose had significantly less leakage than the control. However, there was no statistically significant difference between wet and dry bonding techniques for either material.

Glass ionomer cement surface protection

PURPOSE

To evaluate the effectiveness of various surface treatments for glass ionomer cement (GIC) by determining quantity of dye uptake spectrophotometrically.

MATERIALS AND METHODS

Sixty specimens, 4.5 mm diameter and 2 mm thick, were made from Shofu GIC and divided into 10 groups. Positive control (A) and negative control (B) specimens were not protected while experimental specimens were protected with ARM chemically-cured bonding resin (C), Durafill Bond light-cured bonding resin (D), Bondlite light-cured bonding resin (E), Colorama nail varnish (F), Shofu varnish (G), Copalite varnish (H), Vaseline (I) or Vaseline followed by Copalite (J). The discs were immersed in 0.05% methylene blue solution 10 minutes after mixing except group B specimens which were immersed in deionized water. After 24 hours the discs were removed, washed, and individually placed in 1 ml 65% nitric acid for 36 hours. The solutions were filtered, centrifuged and the absorbance determined spectrophotometrically at 590 nm. Dye uptake was expressed in microgram dye/restoration and the data analyzed by ANOVA and Tukey Kramer test.

RESULTS

The mean (SD) of dye uptake were: A:95.12 (11.28); B:0 (0); C:40.90 (5.06); D:33.89 (3.63); E:35.73 (3.36); F:3.29 (0.79); G:14.87 (2.86); H:21.99 (3.25); I:47.21 (7.06); J:29.74 (3.49). All the surface agents were effective in protecting setting restorative glass ionomer cement, but nail varnish provided the best results.

Clinical evaluation of a posterior resin composite: 3-year results

PURPOSE

To clinically evaluate a resin composite.

MATERIALS AND METHODS

Sixty restorations were inserted at a ratio of 1:3 in Class I and II preparations in molars. Caulk Prisma AP.H/Prisma Universal Bond resin composite restorative system was placed. All the restorations were evaluated using the USPHS system and M-L indirect scale; 6, 12, 24 and 36 month recalls were compared to baseline.

RESULTS

Color, interfacial staining, secondary caries, marginal integrity and surface texture (Alfa = 89%, 94%, 97%, and 100% respectively) were essentially unchanged from baseline for all restorations. One restoration failed due to secondary caries. Two were assessed with Charlie (C) ratings for marginal defects and one for wear. Direct wear analysis (Alfa = 12%) was significantly changed from the baseline. Indirect mean estimated wear measurements for each recall period, adjusted for baseline, were 21 +/- 18 microns, 54 +/- 29 microns, 67 +/- 29 microns, and 98 +/- 43 microns respectively. The wear of AP.H was characteristically linear (g2 = 0.987) for composites whose mean filler particle size approaches 1 micron or less.

Apical marginal adaptation of orthograde and retrograde root end fillings: a dye leakage and scanning electron microscopic study

A few studies have attempted to examine the correlation between clinical success of root canal therapy and in vitro examinations. In this case report we examined the apical adaptation of three orthograde fillings and four retrograde amalgam root end fillings from four radiographically successful teeth and one unsuccessful case by using dye leakage and scanning electron microscopic methods. Despite the radiographic appearance of successful root canal therapy, these examinations showed penetration of methylene blue dye through the apical foramina to the levels of the root canal filling materials in the roots treated nonsurgically and the presence of small gaps between filling materials and the dentinal walls. The methylene blue dye also penetrated through the interface between amalgam and root end cavities, and there were varying size gaps between the root end cavities and amalgam. Similar examinations on the radiographically unsuccessful retrograde filling showed the presence of gaps between the amalgam and the root end cavity preparation and complete penetration of methylene blue dye between amalgam, root canal filling materials, and the dentinal walls.

Laboratory evaluation of experimental restorative systems containing 4-META

PURPOSE

To determine the in vitro shear bond strengths and quantitative microleakage of four experimental bonding restorative systems used in conjunction with Metafil-A, an experimental composite that does not contain 4-META, and Metafil-Ex, a 4-META containing experimental composite.

MATERIALS AND METHODS

120 test specimens were prepared on dentin treated with Amalgambond Activator followed by the application of an experimental primer consisting of 35% glyceryl methacrylate. In 60 teeth the mixed Amalgambond Base and Catalyst was then applied while in the remaining 60 teeth this step was omitted. Cylinders of either Metafil-A or Metafil-Ex were bonded to the dentin surfaces and the test specimens removed from the assembly apparatus after 1 minute or after 15 minutes and the latter specimens were stored in saline at 37 degrees C for 24 hours prior to determining the shear bond strength in an Instron machine at a crosshead speed of 0.5 mm/minute. Sixty Class V preparations were made on the facial surfaces of the roots of extracted human premolars and the preparations restored with the four restorative systems. The quantitative microleakage was determined by a spectrophotometric dye-recovery method.

RESULTS

The shear bond strengths were significantly lower when the 4-META-containing Amalgambond Base and Catalyst were not applied and were unmeasurable when Metafil-A was used as the composite. The quantitative microleakage of the latter system was significantly greater than when the other restorative systems were used.