Radiant Exitance of Old, New, and Damaged LED Light Curing Units.

PURPOSE: This study aimed to determine the radiant exitance of new, damaged, and 16-year-old light-curing units (LCUs) with and without infection control barriers, and before and after removal of any debris. METHODS AND MATERIALS: Old LCUs consisted of 62 SmartLite iQ2 lights (Dentsply Sirona, York, PA). New LCUs consisted of 58 SmartLite Focus (Dentsply Sirona) and 58 Valo Grand (Ultradent, South Jordan, UT, USA) LCUs. Each LCU was examined for damage and debris on its tip. A handheld radiometer (CheckUp with BlueLight Analytics app, Halifax, Nova Scotia, Canada ) was used to measure the radiant exitance using a 10-second exposure time. Measurements were made with and without infection control barriers. If debris was present, the radiant exitance was measured before and after removal of debris with and without the barriers. All measurements were repeated three times. The means of the measurements were used for statistical analyses, which consisted of paired t-tests, analysis of variance (ANOVA), and Tukey post-hoc analyses conducted with a 0.05 level of significance. RESULTS: Infection control barriers significantly reduced the radiant exitance of all LCUs, ranging from 4.35% to 6.91% depending upon the LCU and the presence of debris or damage. Clean undamaged SmartLite Focus (907 mW/cm2) and Valo Grand (Ultradent) LCUs (883 mW/cm2) with barriers had statistically higher radiant exitance than older clean undamaged SmartLite iQ2 (Dentsply Sirona) LCUs (719 mW/cm2) with barriers. All LCUs exceeded the recommended 400 mW/cm2 radiant power to cure 2 mm of Filtek Supreme Ultra shade A2 composite resin (3M ESPE, St Paul MN, USA). CONCLUSION: Infection control barriers, debris, damage, and age all significantly reduced radiant exitance of the lights.

Evaluation of flexural, diametral tensile, and shear bond strength of composite repairs.

OBJECTIVE: Repairing composite restorations may be a more conservative treatment than replacing the entire restoration. The objective of this in vitro study was to determine the best repair method by measuring flexural, diametral tensile, and shear bond strength of repaired composites in which the surfaces were treated with chemical primers (Add & Bond or Silane Bond Enhancer), a bonding agent (Optibond Solo Plus [OBSP]), or mechanical retention with a bonding agent. METHODS: Filtek Supreme Ultra shade B1B was placed in special molds to fabricate specimens that served to test the flexural, diametral tensile, or shear strength of the inherent resin substrate. The same molds were modified to make specimens for testing repair strength of the resin. Repairs were made immediately or after aging in deionized water at 37°C for seven days. All repair sites were finished with coarse Sof-Lex discs to simulate finishing new restorations or partially removing aged restorations. Repair surfaces were treated with one of the following: 1) phosphoric-acid etching and OBSP; 2) Add & Bond; 3) phosphoric-acid etching, Silane Bond Enhancer, and OBSP; or 4) quarter round bur, phosphoric-acid etching, and OBSP. Specimens were placed back in the original molds to fabricate specimens for diametral tensile or flexural testing or in an Ultradent jig to make specimens for shear bond testing. Composite resin in shade B5B was polymerized against the treated surfaces to make repairs. Two negative control groups for the three testing methods consisted of specimens in which repairs were made immediately or after aging without any surface treatments. Controls and experimental repairs were aged (water 37°C, 24 hours) before flexural, diametral tensile, or shear testing in an Instron Universal testing machine at a crosshead speed of 0.5 mm/min. RESULTS: Experimental flexural repair strengths ranged from 26.4% to 88.6% of the inherent substrate strength. Diametral tensile repair strengths ranged from 40% to 80% of the inherent substrate strength, and shear bond strength repairs ranged from 56% to 102%. Geometric means were statistically analyzed with two-way analysis of variance on their log-transformed values. Significant differences were determined using Tukey honestly significant difference (p<0.05). CONCLUSIONS: Depending on the mechanical property being tested, surface treatments produced different results. OBSP produced more consistent results than chemical primers.

Evaluating dentin surface treatments for resin-modified glass ionomer restorative materials.

This in vitro study evaluated the effect of six surface treatments on the shear bond strength of three resin-modified glass ionomers (RMGIs) to dentin. Occlusal surfaces of caries-free third molars were reduced to expose only dentin. Surface treatments were smear layer intact (negative control), Cavity Conditioner, EDTA, Ketac Primer, Self Conditioner, and etching with 35% phosphoric acid followed by the application of Optibond Solo Plus. Filtek Z250 composite resin bonded with Optibond Solo Plus served as a positive control. Conditioning agents were used according to the manufacturers' instructions. After surface treatments, Fuji II LC, Riva LC, Ketac Nano, and Filtek Z250 were placed in copper-band matrices 5 mm in diameter and 2 mm in height and were light-cured for 20 seconds. Specimens were stored in 100% humidity for 24 hours, after which they were placed in deionized water for 24 hours at 37°C. They were then tested under shear forces in an Instron Universal Testing Machine at a crosshead speed of 0.5 mm/min. A two-way analysis of variance and Tukey honestly significant difference statistical analyses (p<0.05) indicated significant interaction between RMGIs and conditioning agents. Acid etching followed by Optibond Solo Plus provided highest bond strengths for all three RMGIs, which were not statistically different from the positive control.

Resin-bonded fixed partial dentures: a review of three decades of progress.

The resin-bonded fixed partial denture has undergone significant changes in design, materials and tooth preparation since its development in 1973. The selection of resin cement and micromechanical retention have closely paralleled alloy-resin-bonding research. Despite impressive in vitro research results, only 74 percent of the prostheses are still functional at the end of four years. Understanding the limitations, indications and design of resin-bonded fixed partial dentures will result in improved longevity and patient satisfaction.

Necrotizing sialometaplasia: literature review and case reports.

The authors describe necrotizing sialometaplasia, a benign inflammatory lesion primarily involving the minor salivary glands of the hard palate. The lesion presents itself as a deep-seated palatal ulcer with clinical and histologic features mimicking those of a malignant neoplasm. The lesion is believed to be the result of vascular ischemia initiated by trauma. An incisional biopsy is required to confirm the diagnosis, and the lesion heals by secondary intention within four to 10 weeks.

Comparing the resistance of dentin bonding agents and pins in amalgam restorations.

This in vitro study involving 84 caries-free molar specimens examined the resistance of complex amalgam restorations retained by two dentin bonding agents--Amalgambond and Amalgambond Plus--four regular TMS pins, six regular TMS pins and four pins in conjunction with Amalgambond. Analysis indicated that the Amalgambond restorations were significantly weaker than the other types. Amalgambond Plus restorations were significantly stronger than the Amalgambond restorations but not different from the remaining groups. The authors concluded that complex amalgam restorations should be retained with a combination of adhesive and mechanical retention.

Retention of complex amalgam restorations using self-threading pins, amalgapins, and Amalgambond.

PURPOSE: To compare the shear fracture resistance of complex amalgam restorations retained by four regular TMS pins, four amalgapins, Amalgambond, or four amalgapins in conjunction with Amalgambond. MATERIALS AND METHODS: Sixty maxillary molars free of caries were mounted in acrylic resin and the occlusal surfaces were ground flat to within 2 mm of the CEJ. The specimens were randomly divided into four groups of 15 teeth. Each group provided one of the four different methods of resistance. Dispersalloy was condensed into the prepared specimens. The specimens were adjusted to provide 4 mm height of amalgam. After 1000 thermocycles, the specimens were loaded at a 45 degree angle to the occlusal surface at a crosshead speed of 1 mm/second. RESULTS: Statistical analysis revealed that Amalgambond, four amalgapins and four amalgapins in conjunction with Amalgambond provided more resistance to shear force than four regular TMS pins.

A new method of attaching cast gold occlusal surfaces to acrylic resin denture teeth.

Historically, cast gold occlusal surfaces for complete or removable partial dentures have been fabricated with retentive loops or beads and luted to prepared denture teeth with acrylic resin or attached to tooth-colored, heat-processed acrylic resin. At present, alternatives to mechanical retention for attaching resin to metal include chemical bonding of the resin after placement of intermediate ceramic or tin layers and the use of chemically adhesive resin cements. Compared to mechanical retention, the chemical bonding of resin to metal requires less gold and allows more room for properly contoured and esthetic resin. Additionally, this chemical bond limits microleakage at the resin-metal interface. In the following technique, cast gold occlusal surfaces are fitted to onlay preparations of acrylic resin denture teeth set in a processed denture base. The castings are air-abraded, tin plated, and luted to the denture teeth with Panavia dental adhesive. This method is quick, easy, and economical.

Evaluation of tin plating systems for a high-noble alloy.

The tensile bond strength of Panavia EX to a high-noble alloy prepared by abrasive spraying and tin plating was measured. Two different intraoperatory tin plating systems were compared. Disk-shaped specimens were cast in type III gold, abrasive sprayed with aluminum oxide, and divided into three groups of 30 specimens each. Specimens in one group were tin plated by using a Kura Ace Mini unit, those in the second group were tin plated by using a Micro Tin unit, and those in the third group were not tin plated and served as the control group. Disks within each group were luted to each other with Panavia EX. The specimens were thermocycled and tested in tension. There was no significant difference between the two tin plated groups; however, the luting bond of both experimental groups was significantly stronger than was that of the control (P < .05).

Tensile strength of three resin cements following two alloy surface treatments.

Retainers for composite retained prostheses ("Maryland bridges") have traditionally relied upon an etched base metal alloy for micromechanical retention. This study compared the tensile bond strength of three resin cements using two alloy surface treatments. Rexillium III and Olympia disks were cast, oxidized, and given simulated porcelain firings. Paired specimens were cemented with Comspan, Panavia EX, or C & B Metabond after air abrasion with aluminum oxide or silicoating. Air-abraded Olympia disks were tin plated prior to luting with Panavia EX. Electrolytically etched Rexillium III specimens luted with Comspan served as controls. Specimens were thermocycled and tested in tension. Highest tensile bond strengths were achieved with: (1) Olympia specimens, where the bonding surface was air abraded but tin plated before cementation with Panavia EX, and (2) Rexillium III specimens, where the bonding surface was air abraded or silicoated and the disks were cemented with C & B Metabond.