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Long-term fluoride release from glass ionomer-lined amalgam restorations.

This in vitro study evaluated the amount of fluoride released from glass ionomer-lined amalgam restorations over a period of 1 year. Class V cavities (2 x 2 x 7 mm) were prepared on the facial and lingual surfaces of 50 extracted human molars randomly distributed into 5 groups: Group 1: No restorations; Group 2: Dispersalloy amalgam alone; Group 3: same as Group 2 except 1 mm of Ketac-Silver was placed on the axial wall before amalgam insertion; Group 4: GC Lining/amalgam; and Group 5: Miracle Mix/amalgam. After restoration, each tooth was thermocycled (100x) at 5 degrees C and 55 degrees C with a dwell time of 30 seconds for baseline fluoride release levels. The teeth were placed in a polyethylene vial containing 4 ml of deionized water. At weekly intervals, each tooth was transferred to a fresh vial. Fluoride release was measured with a fluoride ion specific electrode for 10 consecutive weeks and then again at the end of 1 year. Calibration curves for low level measurements were prepared so the readings could be expressed in micrograms/ml F. At 1 year, fluoride released in micrograms/ml was: Group 1: less than 0.08; Group 2: less than 0.08; Group 3: 0.28; Group 4: 0.68; Group 5: 1.12. An ANOVA was used to evaluate the statistical difference between the groups. At the end of 1 year, measurable amounts of fluoride were recorded for all glass ionomer-lined groups with Miracle Mix and GC Lining releasing significantly more fluoride than Ketac-Silver (P less than 0.002).

Analysis of Variance↗

A 3-year clinical evaluation of two composite resins in class-II cavities.

The purpose of this investigation was to study the clinical performance of a new system with a proposed expanding liner for composite restorations introduced in the late 1980s. The present study reports on baseline data and the result after 3 years. One hundred and four class-II cavities in 95 patients were alternatively restored by Superlux Molar and the reference material P-50 APC by 12 general practitioners in 3 public dental health clinics. After 3 years 82 restorations (79%) were available for examination. The restorations were evaluated on the basis of USPHS criteria after 1 week and again after 3 years. Stone casts were used to quantitatively categorize wear in accordance with the Leinfelder method. Color slides and bitewings were taken to supplement the clinical evaluation of color match and marginal adaptation, respectively, and secondary caries. The failure rate (USPHS rating, Charlie) was four restorations of Superlux Molar and seven of P-50 APC. The average wear after 3 years of Superlux Molar was 131 microm and of P-50 APC, 128 microm. There were no statistically significant differences between the two materials with regard to, for example, handling characteristics, anatomic form, color match, marginal discoloration, or failures. A significantly higher wear rate was found after 3 years in patients with a high level of salivary lactobacilli (> 10(5) colony-forming units (CFU)/mL at base line) compared with those with lower levels. This suggests that an acidic environment might enhance the wear rate.

Analysis of Variance↗

Marginal seal of cervical tooth-coloured restorations. A laboratory investigation of placement techniques.

Incremental placement of composite resin has been suggested as a means of overcoming the contraction that occurs during polymerization of the composite material and as a consequence should allow an improved gingival dentine seal. Numerous incremental placement techniques for composite resin restorations have been documented in the literature. This study examined four different methods of placing Silux in class V cavities, located in the region of the cemento-enamel junction, and lined with Vitrabond. None of the placement methods used completely sealed either the enamel or dentine margins. Of the four techniques employed, the one which involved incremental placement of the gingival component first showed the least amount of leakage at the dentine margin. This result, however, was only significantly different from that of the bulk placement method. In the majority of cases where leakage did occur at the dentine margin, it progressed no further than the Vitrabond lining. It appeared that the high initial adherence to dentine of the light cured glass-ionomer cement prevented deeper penetration of the dye.

Bisphenol A-Glycidyl Methacrylate↗

Effect of composite resin restorations in monkeys teeth with experimentally induced pulpitis.

The short- and long-term pulpal reactions to composite resin restorations using differenct cavity lining materials have been assessed in monkey teeth with experimentally induced pulpitis. The inflammation was induced by filling cavities with soft human carious dentin and amalgam for 1 week. Healing of the inflammation and formation of reparative dentin was generally found independent of the lining materials used. The long-term response to cavities restored with carious dentin and amalgam was also healing of the primarily induced pulpal inflammation in most instances.

Animals↗

Addition of fresh amalgam to existing amalgam: microleakage study.

The purpose of this in vitro study was to determine whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed (new) and existing (old) amalgam. Forty-eight specimens were used in the experimental groups. The materials used to study microleakage in this investigation were: copal varnish, a dentin bonding agent (Clearfil New Bond), and a 4-META adhesive (Amalgambond). No significant difference in microleakage was found at the interfaces between freshly placed and existing amalgam. Significantly less microleakage was noted in specimens using the 4-META adhesive and the dentin bonding agent as compared to specimens in which no lining material was placed. Significantly less microleakage was noted in specimens using the 4-META adhesive compared to specimens using cavity varnish.

Analysis of Variance↗

Mechanical properties of bioactive amorphous calcium phosphate/methacrylate composites.

OBJECTIVES: The aim of this study was to determine whether amorphous calcium phosphate (ACP)-containing composites, which have the ability to release mineralizing levels of Ca and PO4 ions, have appropriate mechanical properties for use as base and lining materials. METHODS: Composites of pyrophosphate-stabilized ACP particulates (mass fraction of 40%) and photo-activated methacrylate resins (mass fraction of 60%) were tested for biaxial flexure strength (BFS), diametral tensile strength (DTS), and compressive strength (CS). Hydroxyapatite (HAP; mass fraction of 40%), and micro-sized glass (mass fraction of 50%) composites as well as a commercial visible light curable base/liner were also tested. The significance between mean values was determined by Student-Newman-Keuls multiple comparisons (p < 0.05). RESULTS: BFS of dry and wet (24 h at 37 degrees C in water) ACP composites (60.3 and 62.0 MPa, respectively) were significantly lower than those of the comparison materials (79.2-109.3 MPa). CS values were likewise lower (62.9 MPa dry and 67.6 MPa wet vs 80.6-196.8 MPa) except for the wet base/liner (58.5 MPa). DTS of the dry ACP composite (21.8 MPa) was comparable with that of the HAP (22.8 MPa) and glass (25.5 MPa) composites, but lower than that of the base/liner (36.2 MPa). DTS decreased significantly when the ACP composite was wet (17.8 MPa). SIGNIFICANCE: These results suggest that the remineralizing ACP polymeric composites, although mechanically weaker in some respects than other polymeric composites, have properties suitable for use as base and lining materials.

Analysis of Variance↗

Marginal leakage in class V composite resin restorations with glass ionomer liners in vitro.

This in vitro study evaluated the use of a glass ionomer lining cement in conjunction with composite resin in class V preparations in terms of marginal sealing ability. Two preparations, the occlusal walls in enamel (etched) and the gingival walls in dentin, were place in each tooth. One contained the etched glass ionomer liner, a dentin bonding agent, and a microfill composite resin. The second contained the dentin bonding agent and the microfill composite resin. The teeth were thermocycled, stained with methylene blue dye, sectioned, and evaluated for leakage at the occlusal and gingival margins on a scale of 0 to 3. No significant leakage was recorded at the occlusal margin for either restoration. Leakage at the gingival margin was significantly reduced for the lined restorations, and in no instance did the dye penetrate beyond the liner, which suggests that the lining cement may significantly decrease leakage at the gingival aspect of composite resins in class V restorations.

Composite Resins↗

Strength of base materials.

PURPOSE: To compare the punch resistance of VariGlass and Vitrebond. MATERIALS AND METHODS: Discs measuring 1.4 cm in diameter and 1.5 mm thick of VariGlass (VG) and Vitrebond (VT) light-activated lining materials, were prepared and submitted to punch testing in a universal testing machine at 7 minutes, 30 minutes and 24 hours after mixing. RESULTS: VG showed higher resistance to punch testing than the VT in the three periods evaluated (P< 0.01). The results were further compared to previous data obtained from three calcium hydroxide lining cements which gave much lower values than VG and VT (P< 0.01).

Acrylic Resins↗

Microleakage of dentin-amalgam bonding agents.

PURPOSE: To evaluate in vitro the microleakage of various dentin bond/resin liner systems when used with both a spherical and an admixture alloy. MATERIALS AND METHODS: Class V cavity preparations were prepared on 60 noncarious extracted human molar teeth with one margin in enamel and another in dentin and restored with either Dispersalloy or Tytin alloy. Treatment groups utilizing either no liner, Copalite varnish, Amalgambond Plus/HPA, Tenure with Panavia EX Dental Adhesive, Syntac with Dual Cem, and All-Bond 2 with Liner F were tested. Samples were thermocycled, stained, and sectioned to evaluate microleakage. RESULTS: A significant reduction in microleakage at the enamel and dentin margins was found in all dentin bond system/resin liner groups when compared to unlined and Copalite-lined alloys. There were no significant differences in total microleakage scores between the alloy types. Statistically significant differences in microleakage were detected between some systems. The Tenure with Panavia EX treatment group exhibited a significantly lower total microleakage when used with Tytin. The Syntac/Dual Cem treatment groups exhibited a significantly higher total microleakage when used with Dispersalloy.

Analysis of Variance↗

Bonding of amalgam to tooth structure: tensile adhesion and microleakage tests.

Amalgam can be bonded to etched enamel by a thin coat of Panavia resin cement with a resulting mean bond strength of 1404 psi to enamel and 469 psi to dentin as tested in tension. Less microleakage was observed in resin-bonded amalgam restorations than in Copal varnish-lined or unlined restorations. The technique could be used clinically with possible implications for cavity design, fracture resistance of restored teeth, and recurrent caries. These properties as well as the variables affecting bond strength need further exploration.

Acid Etching, Dental↗

A new light-activated adhesive cavity liner: an in vitro bond strength and microleakage study.

A new formulation of a light-activated calcium hydroxide-based cavity liner was developed for this study. Its shear bond strength and marginal microleakage in a Class V cavity preparation were compared to those of commercially available light-activated liners and conventional glass ionomer liners: GC Lining Cement (GC), Ketac-Bond (ESPE), Time Line (Caulk), Vitrabond (3M), XR lonomer (Kerr), and Zionomer (DenMat). The new formulation had significantly higher shear bond strength to dentin than the commercially available materials. Its microleakage along gingival (cemento-dentin) walls was statistically equivalent to one of the other materials and significantly better than all the others.

Analysis of Variance↗

Fracture resistance of premolars with MOD amalgam restorations lined with Amalgambond.

A comparison was made of the fracture resistance of premolar teeth with mesial-occlusal-distal (MOD) amalgam preparations lined with either a resin containing 4-META (Amalgambond) or copal varnish (Plastodent) and restored with a spherical alloy (Tytin). Restored teeth were aged for 7 or 67 days at 37 degrees C in 100% humidity and thermocycled between 5 and 55 degrees C for 3500 cycles. There was no significant difference in the mean fracture resistance between teeth lined with Amalgambond and teeth lined with Plastodent under any of the test conditions. SEM analysis of thermocycled specimens showed no evidence of maintained adhesion between the Amalgambond and amalgam.

Analysis of Variance↗

Evaluations of the interface between amalgam and dentin with a single component dentin bonding system.

The purpose of this scanning electron microscope study was to observe the dentin-amalgam interface after utilizing a standard restorative liner and a single-component dentin adhesive. Continuous interface gaps of over 15 mu were observed in specimens containing no lining and Copal varnish. Discontinuous 5 microns gaps were observed in specimens treated with PQ1. Additionally, specimens treated with PQ1 exhibited resin interpenetration into the dentin surfaces.

Adhesives↗

A simulated clinical appraisal of base materials for amalgam restorations.

Eight materials were placed as bases on the pulpal surface of cavities prepared in extracted teeth. Seven minutes after mixing of the material commenced, amalgam was condensed on to the lined cavity. The restored teeth were sectioned subsequently for microscopic examination. The results suggested that all uniformly mixed, carefully placed base forming materials that have reached the state of "clinical set" are able to withstand loads applied during amalgam condensation irrespective of their strength.

Calcium Hydroxide↗

Microleakage in the sandwich technique.

This study assessed the microleakage and if it was possible to reproduce the success that is seen in the oral cavity with properly placed "sandwich" restorations. Simulated Class V erosion lesions were prepared in extracted human molar teeth and restored using a Type III glass ionomer lining cement mixed mechanically at a high powder:liquid ratio of 3:1 or greater with resin composite laminated to it leaving cement exposed at the gingival margin. To update the technique for modern materials a dual cure glass ionomer lining cement was placed in a second series with resin composite laminated to it completely covering the gingival margin. The restorations were stored in water for two weeks before temperature cycled and immersed in dye. The results showed minimal leakage relative to most other published studies and that most leakage was related to the setting shrinkage of the resin composite.

Composite Resins↗

Effectiveness of three cavity varnishes in reducing marginal microleakage of amalgam restorations: an in vitro study.

Dentin Adhesit, Cavi-Line and Kavite Lak cavity varnishes were applied to the walls of prepared Class V cavities in fifty-two caries free extracted molar teeth before placing amalgam fillings. Tests with Methylene Blue dye after thermocycling showed that all cavity varnishes showed significantly lesser marginal leakage when compared with the control group without any cavity varnish.

Dental Amalgam↗

The use of liners under amalgam restorations: an in vitro study on marginal leakage.

OBJECTIVE: Marginal leakage of amalgam restorations may lead to secondary caries and pulpal damage. The purpose of this study was to determine the effect various cavity liners might have on microleakage. METHOD AND MATERIALS: Mesio-occlusodistal amalgam restorations with margins on enamel and dentin were treated with different liner materials (an adhesive system, a topical fluoride gel, a cavity varnish, and a glass-ionomer cement) in vitro. Following restoration, the teeth were submitted to thermocycling in a stained solution and sectioned to allow assessment of microleakage. RESULTS: On enamel, the control group (no liner) and the glass-ionomer-lined group had equivalent leakage scores and were superior to every other group. On dentin, only the glass-ionomer specimens had superior performance. The cavity varnish and fluoride-lined specimens exhibited the highest leakage scores. CONCLUSION: The use of liners does not reduce microleakage on amalgam restorations when the cavity margins remain on enamel. On dentin margins, a glass-ionomer liner can reduce microleakage.

Adhesives↗