All Purpose Abrasives is a leading supplier of abrasives, grinding consumables, diamond products and a range of grinding and abrasive equipment across Australia.
All Purpose Abrasives are stockists of a wide range of grinding consumables including reinforced grinding products such as flap discs, grinding wheels, wire brush products, cut off wheels, flexible discs, zec discs and depressed centre grinding wheels.
Also available are bonded abrasives for automotive, rail, saw sharpening and foundry applications in addition to a range of tapes and packaging supplies.
All Purpose Abrasives stocks diamond products such as diamond cutting blades, continuous rim and segmented blades, cup grinding wheels, diamond flexible linishing belts, dressers and truing nibs.
Other products include coated abrasives, sand paper abrasive belts, sponges, flap wheel abrasives, metal polishing abrasives and compounds, crimped wire wheels, bevel brushes, hand wire brushes, pipeline wire brushes, twist knot wire wheels, cup brushes, mops, finishing belts, hand abrasive pads and convolute wheels.
Their product range also includes grinding and abrasive machinery, hand tools, metal polishing machinery, bandsaws and bandsaw blades, measuring equipment, cutting tools, specialist drills, dust extraction systems, industrial air tools and surface finishing chemicals.
2011年7月28日星期四
2011年7月25日星期一
Carborundum board to mull 2-for-1 stock split
Coated abrasives maker Carborundum Universal said on Monday that its board will consider a 2-for-1 stock split at the company’s board meeting to be held on August 5. Shares of the company ended 0.07% higher at R307.25 in a firm Mumbai market.
Supreme Industries declares 150% dividend
Supreme Industries has informed the Bombay Stock Exchange that the board of directors of the company has recommended final dividend of 150% or R3 per share on 12,70,26,870 equity shares of R2 each face value.
Ravalgaon Sugar to pay 150% annual dividend
Ravalgaon Sugar Farm has informed the Bombay Stock Exchange that the board of directors of the company has decided to recommend a dividend at the rate of 150% or R75 on equity share of R50 each for the year ended March 31, 2011.
Graphite India declares dividend of R3.50
Graphite India has informed the Bombay Stock Exchange that board of the...
Supreme Industries declares 150% dividend
Supreme Industries has informed the Bombay Stock Exchange that the board of directors of the company has recommended final dividend of 150% or R3 per share on 12,70,26,870 equity shares of R2 each face value.
Ravalgaon Sugar to pay 150% annual dividend
Ravalgaon Sugar Farm has informed the Bombay Stock Exchange that the board of directors of the company has decided to recommend a dividend at the rate of 150% or R75 on equity share of R50 each for the year ended March 31, 2011.
Graphite India declares dividend of R3.50
Graphite India has informed the Bombay Stock Exchange that board of the...
2011年7月21日星期四
Chilean volcano darkens Argentine tourism outlook
The 100 million tons of pyroclastic ash and rock spewed by an Andean volcano has meant hundreds of millions of dollars in losses for communities more accustomed to profiting from the dramatic mountain landscape.
The Cordon Caulle volcano opened a new gash along a ridge just across the border and upwind from Argentina. For six weeks now, it has been belching ash into the sky, grounding flights across the lower third of South America for most of the winter tourist season. Lodges and restaurants have been ghostly at resorts normally filled with skiers. Airport runways, Andean slopes and sheep and cattle ranches are coated in thick, abrasive volcanic material.
"Every time the wind blows, no matter the direction, we get ash and sand," Villa La Angostura Mayor Ricardo Alonso said.
In his town, a lakeside Andean jewel just northeast of the volcano, only 62 of the town's 152 hotels are operating, and many of the visitors aren't high-paying skiers but volunteers helping to shovel out the mess, Tourism Secretary Juan Jose Fioranelli said, adding that officials are still tallying the losses.
Still mostly missing in the neighboring resort city of Bariloche are big-spending Brazilians, usually so numerous that Argentines jokingly refer to the city as "Braziloche." Bariloche's population of 140,000 usually hosts 250,000 tourists this time of year, including 40,000 Brazilians. The municipal government this week estimated losses at $150 million.
Since the eruption began June 4, the volcano has released energy equal to 70 atomic bombs, or 2 percent of the world's electricity capacity, during the first week alone, scientists at Argentina's National University of Rio Negro calculated. The ash has blown around the Southern Hemisphere several times, grounding jets as far away as Australia and New Zealand.
Airline industry losses could total $50 million, said Helane Becker, an airlines analyst with Dahlman Rose & Company. Carriers with many routes in Argentina, such as state-owned Aerolineas Argentina and Chile-based LAN Air Lines, will suffer most, but U.S. and European carriers also have been affected, she said.
Aerolineas is still flying a vastly reduced schedule, with 30 flights canceled and more than a dozen postponed on Thursday alone due to the continuing ash cloud, which can severely damage jets in flight. All flights to Bariloche remain suspended until at least Tuesday, and flights to two other regional airports through the end of the month.
Argentine agriculture also has suffered. In the hardest-hit province of Rio Negro, which is dotted with sheep and cattle ranches, farm losses total $24 million, said Adolfo Sarmiento, an agricultural engineer at Argentina's National Institute of Agricultural Technology. Wool producers have lost as much as $3.8 million, he said, with ash making grazing difficult for 1,400 operations that manage hundreds of thousands of sheep, cows and goats.
Geologists say the eruption has diminished considerably from its peak in June, when the plume rose 6 miles (10 kilometers) and stretched across the continent. Chile's government has allowed about 3,500 evacuees, most of them small farmers living below the volcano, to return home.
But a NASA satellite photo this week showed the volcano still spewing ash nearly 2 miles (3 kilometers) high in a column that stretched for 50 miles (80 kilometers) over Argentina, adding to the gritty layers of snow and ash.
Experts have estimated that in Villa La Angostura alone, 5 million cubic meters of volcanic sand must be removed, Fioranelli said. That's roughly equivalent to covering the entire island of Manhattan in 2 inches of the grit. Hundreds of people who started with snow shovels now have heavy equipment helping them dump the mess into nearby quarries.
Chile's National Geology and Mines Service remained on "red alert" Thursday, saying the eruption isn't done yet. There is still a chance of more outbursts, and small earthquakes from underground volcanic activity still rattle the area. Lava and toxic gases still spew from the crater, creating a nightly light show extending about 1,600 feet (500 meters) above the volcano.
Argentine President Cristina Fernandez has declared a regional economic emergency, doubling assistance to poor families and postponing tax payments for restaurants, hotels and other tourism businesses that don't lay off workers.
Aerolineas has arranged buses so people can reach Patagonian resorts such as Bariloche, where more than 500 hotels and hundreds of restaurants depend on the brief June through August ski season. Airports are closed just when Argentines usually take advantage of school holidays to explore the trails above Nahuel Huapi lake.
"I can't say the winter season is lost, but it is going to be very difficult to overcome the situation because it has been catastrophic," Mayor Alonso said.
Local businesses have lost about half their annual earnings, said Sergio Rossi, who runs Villa La Angostura's hotel and restaurant association.
Hotel owner Santiago Perrota's property can sleep 90. Now the hotel is completely empty.
"We're going to lose the winter months anyway, because the eruption is still going on. The ash is still flying," Perrota said. "And we don't want to have people remember us in this situation. We don't want people to remember us without happiness."
Daniel Garcia, who runs the Bariloche tourism chamber, said some vacationing students and tourists have been arriving by bus from Buenos Aires, a road trip of more than 20 hours.
The airport that serves both Bariloche and Villa La Angostura remains officially closed, but it received its first jet in 44 days on Sunday, a charter flight from Brazil that was diverted by weather from Esquel, more than 180 miles (300 kilometers) to the south. Tourism officials hoped it would show the airport is operable, but for now travelers are still being flown to Esquel and bused for hours through the Patagonian desert to reach the slopes.
The Cordon Caulle volcano opened a new gash along a ridge just across the border and upwind from Argentina. For six weeks now, it has been belching ash into the sky, grounding flights across the lower third of South America for most of the winter tourist season. Lodges and restaurants have been ghostly at resorts normally filled with skiers. Airport runways, Andean slopes and sheep and cattle ranches are coated in thick, abrasive volcanic material.
"Every time the wind blows, no matter the direction, we get ash and sand," Villa La Angostura Mayor Ricardo Alonso said.
In his town, a lakeside Andean jewel just northeast of the volcano, only 62 of the town's 152 hotels are operating, and many of the visitors aren't high-paying skiers but volunteers helping to shovel out the mess, Tourism Secretary Juan Jose Fioranelli said, adding that officials are still tallying the losses.
Still mostly missing in the neighboring resort city of Bariloche are big-spending Brazilians, usually so numerous that Argentines jokingly refer to the city as "Braziloche." Bariloche's population of 140,000 usually hosts 250,000 tourists this time of year, including 40,000 Brazilians. The municipal government this week estimated losses at $150 million.
Since the eruption began June 4, the volcano has released energy equal to 70 atomic bombs, or 2 percent of the world's electricity capacity, during the first week alone, scientists at Argentina's National University of Rio Negro calculated. The ash has blown around the Southern Hemisphere several times, grounding jets as far away as Australia and New Zealand.
Airline industry losses could total $50 million, said Helane Becker, an airlines analyst with Dahlman Rose & Company. Carriers with many routes in Argentina, such as state-owned Aerolineas Argentina and Chile-based LAN Air Lines, will suffer most, but U.S. and European carriers also have been affected, she said.
Aerolineas is still flying a vastly reduced schedule, with 30 flights canceled and more than a dozen postponed on Thursday alone due to the continuing ash cloud, which can severely damage jets in flight. All flights to Bariloche remain suspended until at least Tuesday, and flights to two other regional airports through the end of the month.
Argentine agriculture also has suffered. In the hardest-hit province of Rio Negro, which is dotted with sheep and cattle ranches, farm losses total $24 million, said Adolfo Sarmiento, an agricultural engineer at Argentina's National Institute of Agricultural Technology. Wool producers have lost as much as $3.8 million, he said, with ash making grazing difficult for 1,400 operations that manage hundreds of thousands of sheep, cows and goats.
Geologists say the eruption has diminished considerably from its peak in June, when the plume rose 6 miles (10 kilometers) and stretched across the continent. Chile's government has allowed about 3,500 evacuees, most of them small farmers living below the volcano, to return home.
But a NASA satellite photo this week showed the volcano still spewing ash nearly 2 miles (3 kilometers) high in a column that stretched for 50 miles (80 kilometers) over Argentina, adding to the gritty layers of snow and ash.
Experts have estimated that in Villa La Angostura alone, 5 million cubic meters of volcanic sand must be removed, Fioranelli said. That's roughly equivalent to covering the entire island of Manhattan in 2 inches of the grit. Hundreds of people who started with snow shovels now have heavy equipment helping them dump the mess into nearby quarries.
Chile's National Geology and Mines Service remained on "red alert" Thursday, saying the eruption isn't done yet. There is still a chance of more outbursts, and small earthquakes from underground volcanic activity still rattle the area. Lava and toxic gases still spew from the crater, creating a nightly light show extending about 1,600 feet (500 meters) above the volcano.
Argentine President Cristina Fernandez has declared a regional economic emergency, doubling assistance to poor families and postponing tax payments for restaurants, hotels and other tourism businesses that don't lay off workers.
Aerolineas has arranged buses so people can reach Patagonian resorts such as Bariloche, where more than 500 hotels and hundreds of restaurants depend on the brief June through August ski season. Airports are closed just when Argentines usually take advantage of school holidays to explore the trails above Nahuel Huapi lake.
"I can't say the winter season is lost, but it is going to be very difficult to overcome the situation because it has been catastrophic," Mayor Alonso said.
Local businesses have lost about half their annual earnings, said Sergio Rossi, who runs Villa La Angostura's hotel and restaurant association.
Hotel owner Santiago Perrota's property can sleep 90. Now the hotel is completely empty.
"We're going to lose the winter months anyway, because the eruption is still going on. The ash is still flying," Perrota said. "And we don't want to have people remember us in this situation. We don't want people to remember us without happiness."
Daniel Garcia, who runs the Bariloche tourism chamber, said some vacationing students and tourists have been arriving by bus from Buenos Aires, a road trip of more than 20 hours.
The airport that serves both Bariloche and Villa La Angostura remains officially closed, but it received its first jet in 44 days on Sunday, a charter flight from Brazil that was diverted by weather from Esquel, more than 180 miles (300 kilometers) to the south. Tourism officials hoped it would show the airport is operable, but for now travelers are still being flown to Esquel and bused for hours through the Patagonian desert to reach the slopes.
2011年7月18日星期一
Guidelines for using Vacuum Release Trays
The VR Tray should be positioned on a vacuum plate designed to deliver vacuum to the underside of the tray. Stand-alone stations are commercially available however, with proper care applying a house vacuum to the backside of the tray (through the hole in the back of the tray) should also work. Best removal results are obtained by applying a vacuum of 25" of Hg. The Gel membrane may appear to be in the Release Mode even under relatively low vacuum conditions, but a full vacuum is necessary for optimal release.
Pick-up Tools
The largest tweezers tool compatible with the array size should be used in order to deliver the maximum twist or rotation motion. The Gel holding strength is weakest in the peel direction, therefore, the array can be easily removed from the Gel by simply applying rotation.
Array contact/Removal
Contact force between the pick-up tool and the array should be minimized so the array is not pressed into the Gel membrane. Once the array is properly engaged by the pick-up tool, the rate of ascent should initially be slow. Rapid ascent may tend to separate the array from the tool.
Membrane Tear
Gel membranes are relatively fragile and should he handled with care. If a membrane tears, then vacuum leakage at the tray will occur, which can inhibit array removal.
Vacuum Release is a trademark of Gel-Pak. Figures courtesy of Gel-Pak.
Through our Materials Chemistry Centers of Excellence in research and manufacturing we develop advanced, enabling materials for your micro/nanoelectronics, alternative energy, display/optoelectronics, nanotechnology and related materials science and engineering applications. Specialties include ALD precursors, ultra-high purity inorganic halides, fuel cell materials, electronic grade dyes, specialty monomers and cGMP grade polymers.
Pick-up Tools
The largest tweezers tool compatible with the array size should be used in order to deliver the maximum twist or rotation motion. The Gel holding strength is weakest in the peel direction, therefore, the array can be easily removed from the Gel by simply applying rotation.
Array contact/Removal
Contact force between the pick-up tool and the array should be minimized so the array is not pressed into the Gel membrane. Once the array is properly engaged by the pick-up tool, the rate of ascent should initially be slow. Rapid ascent may tend to separate the array from the tool.
Membrane Tear
Gel membranes are relatively fragile and should he handled with care. If a membrane tears, then vacuum leakage at the tray will occur, which can inhibit array removal.
Vacuum Release is a trademark of Gel-Pak. Figures courtesy of Gel-Pak.
Through our Materials Chemistry Centers of Excellence in research and manufacturing we develop advanced, enabling materials for your micro/nanoelectronics, alternative energy, display/optoelectronics, nanotechnology and related materials science and engineering applications. Specialties include ALD precursors, ultra-high purity inorganic halides, fuel cell materials, electronic grade dyes, specialty monomers and cGMP grade polymers.
2011年7月14日星期四
Buy Carborundum; target of Rs 347: Firstcall Research
“Carborundum Universal, popularly known as CUMI, is engaged in manufacturing of coated and bonded abrasives, super refractories, electro minerals, industrial ceramics and ceramic fibres in India. Incorporated in 1954, the company was formed as a collaboration between Murugappa Group, Carborundum Inc, USA, and the Universal Grinding Wheel Co of the UK. CUMI manufactures over 20,000 different types of abrasives, refractory products and electro minerals. Globally, the company has a presence in 43 countries with retail network of 200,000 outlets. The company's manufacturing facilities are situated in 14 locations. Most of CUMI's manufacturing plants have received ISO 9002 certification for its quality management. The company operates its in-house research and development operations and collaborative research with foreign institutions in order to sustain its position in India and aboard.”
“During the quarter, the company disclosed a consolidated profit of Rs. 494.30 million as against of Rs.324.30 million for the quarter ended March 31, 2010. Net sales are increased by 19% to Rs. 4344.20 million from Rs. 3653.50 million in the same quarter previous year. In the same period, consolidated operating profit of the company was at Rs. 895.00 million, a rise of 33% over the prior year period. Company EPS is stood at Rs.5.29 for the quarter ended March 2011.”
“Net Sales and PAT of the company are expected to grow at a CAGR of 17% and 25% over 2010 to 2013E respectively. On the basis of EV/EBITDA, the stock trades at 8.75 x for FY12E and 8.74 x for FY13E. Price to Book Value of the stock is expected to be at 3.08 x and 2.51 x respectively for FY12E and FY13E. Earning per share (EPS) of the company for the earnings for FY12E and FY13E is seen at Rs.20.19 and Rs.22.76 respectively. At the current market price of Rs.307.00, the stock is trading at 15.21 x FY12E and 13.49 x FY13E respectively. We expect that the company will keep its growth story in the coming quarters also. We recommend ‘BUY’ in this particular scrip with a target price of Rs 347 for medium to long term investment,” says Firstcall Research report.
“During the quarter, the company disclosed a consolidated profit of Rs. 494.30 million as against of Rs.324.30 million for the quarter ended March 31, 2010. Net sales are increased by 19% to Rs. 4344.20 million from Rs. 3653.50 million in the same quarter previous year. In the same period, consolidated operating profit of the company was at Rs. 895.00 million, a rise of 33% over the prior year period. Company EPS is stood at Rs.5.29 for the quarter ended March 2011.”
“Net Sales and PAT of the company are expected to grow at a CAGR of 17% and 25% over 2010 to 2013E respectively. On the basis of EV/EBITDA, the stock trades at 8.75 x for FY12E and 8.74 x for FY13E. Price to Book Value of the stock is expected to be at 3.08 x and 2.51 x respectively for FY12E and FY13E. Earning per share (EPS) of the company for the earnings for FY12E and FY13E is seen at Rs.20.19 and Rs.22.76 respectively. At the current market price of Rs.307.00, the stock is trading at 15.21 x FY12E and 13.49 x FY13E respectively. We expect that the company will keep its growth story in the coming quarters also. We recommend ‘BUY’ in this particular scrip with a target price of Rs 347 for medium to long term investment,” says Firstcall Research report.
2011年7月11日星期一
Natcore to Coat Fabric with Nanoparticle Materials
Georgia Institute of Technology has awarded a subcontract to Natcore Technology to coat a fabric with nanoparticle solutions.
Natcore will use its proprietary liquid phase deposition (LPD) technology to carry out the coating process. The fabric coated with nanoparticle materials will be utilized to produce wet suit-type clothes, which will protect users from viral and bacterial agents when they are exposed to polluted water for a longer time.
Professor Andrew R. Barron, co-founder and director of Natcore, has developed the nanomaterial at the Rice University lab. Natcore has partnered with New York-Based Eastman Kodak Company to carry out a roll-to-roll coating process by utilizing the new nanomaterial solution. Natcore will deliver the coated fabric to Georgia Tech for fabrication and testing of a small number of wet suits. The suits produced from the nano-coated fabric could offer safety for first responders, Navy SEALS, oil platform divers and others who are exposed to polluted water.
The President and Chief Executive Officer of Natcore, Chuck Provini stated that the contract is provides an excellent opportunity to the company to apply its LPD technology.
Natcore will use its proprietary liquid phase deposition (LPD) technology to carry out the coating process. The fabric coated with nanoparticle materials will be utilized to produce wet suit-type clothes, which will protect users from viral and bacterial agents when they are exposed to polluted water for a longer time.
Professor Andrew R. Barron, co-founder and director of Natcore, has developed the nanomaterial at the Rice University lab. Natcore has partnered with New York-Based Eastman Kodak Company to carry out a roll-to-roll coating process by utilizing the new nanomaterial solution. Natcore will deliver the coated fabric to Georgia Tech for fabrication and testing of a small number of wet suits. The suits produced from the nano-coated fabric could offer safety for first responders, Navy SEALS, oil platform divers and others who are exposed to polluted water.
The President and Chief Executive Officer of Natcore, Chuck Provini stated that the contract is provides an excellent opportunity to the company to apply its LPD technology.
2011年7月6日星期三
The Cave Singers, No Witch
Over two previous albums, this Seattle-based outfit weren't easy to pigeonhole (alt.country, boho-folk, indie.something?) but were always interesting because of that, not least for singer Peter Quirk's distinctive vocals which were "quirky" for want of a better word. Here, however, they really throw in some visceral, edgy material (the abrasive and tense Black Leaf, the psychedelic spook voodoo of Outer Realms) alongside brooding backwoods menace (Falls where an Appalachian Doors get old time religion and quit town in a hurry) and strange, evocative narratives (Haller Lake). Quirk's singing has become stronger and more tar-coated, the arrangements for small string parts and keyboards are more complex and there are discreet influences from drone music, blues and Middle Eastern melodies alongside their strong core of alt-folk.
Things falter a little around the midpoint (Clever Creatures sounds like Lou Reed gone to Texas, the harmonica-embellished Haystacks you might have heard from the likes of Peter Case and the Waterboys) but the dreamy folk of Distant Sures and unexpected Indo-electronica of Faze Wave redeem things.
An interesting and worthwhile direction from a band which has always been worth hearing and seldom delivers the expected. If they are new to you, here's where you make their strangely compelling acquaintance.
Things falter a little around the midpoint (Clever Creatures sounds like Lou Reed gone to Texas, the harmonica-embellished Haystacks you might have heard from the likes of Peter Case and the Waterboys) but the dreamy folk of Distant Sures and unexpected Indo-electronica of Faze Wave redeem things.
An interesting and worthwhile direction from a band which has always been worth hearing and seldom delivers the expected. If they are new to you, here's where you make their strangely compelling acquaintance.
2011年7月4日星期一
Are whitening toothpastes a bright idea?
Whitening mania is especially obvious in the toothpaste aisle. Just about every major brand now comes in special whitening formulas.
While strips and trays work by soaking the teeth in bleach for long stretches of time, whitening toothpastes take a faster approach. They generally rely on abrasives (toothpaste companies prefer to call them "polishers") that help remove surface stains left behind by coffee, cigarettes, juices and foods.
Crest, a Procter & Gamble brand, offers 3D White Vivid and 3D White Advanced Vivid. Both varieties contain hydrated silica as an abrasive. The advanced version, which comes out of the tube in two separate chambers, also has sodium hexametaphosphate, a compound that helps loosen the stains so the abrasives can do their job. Users are instructed to brush after meals or at least twice a day. Expect to pay about $4 for the 4.1-ounce tube of either product.
Rembrandt, a Johnson & Johnson company, has built its brand around the promise of whitening. Both its Intense Stain and Deeply White toothpastes contain hydrated silica. Deeply White also has the bleaching agent urea peroxide. Users are instructed to brush twice daily "and after meals if possible." A 3-ounce tube of Intense Stain costs about $8, and a 2.6-ounce tube of Deeply White goes for about $7.
The claims
The label for Crest 3D White Vivid claims it can remove 80% of surface stains in two weeks, and the advanced version says it removes 90% of surface stains in the same period of time. Alissa Fitzgibbons, a spokeswoman for Procter & Gamble, says "a lot of consumers see great results" from the toothpastes. She adds that people who want extra whitening often try Crest WhiteStrips or other bleaching products.
The Rembrandt website says the peroxide in the Deeply White toothpaste targets "deep stains" in the teeth and that Intense Stain is "expertly formulated to remove tough stains, prevent new stains from sticking and actively restore and strengthen tooth enamel." Teresa Panas, a spokeswoman for Johnson & Johnson, says that Deeply White "polishes away surface stains and safely whitens below the enamel." She also says that Intense Stain contains "micro-polishers" that go to work on stains "like red wine, soda, coffee and tobacco."
The bottom line
There's no doubt that whitening toothpastes can clean stains off teeth and give them a little extra gleam. But the term "whitening" is misleading, says Dr. Vincent Mayher, a Haddonfield, N.J., dentist and the past president of the Academy of General Dentistry. Unlike trays and strips that can bleach deep within a tooth, he explains, toothpastes can reach only the surface. Besides, he adds, bleaches in toothpastes are useless because they'll get rinsed away before they do anything.
Still, getting rid of surface stains can really brighten a smile, and Mayher says whitening toothpastes can be worth a try as long as a user doesn't expect miracles. If a person has his or her teeth bleached, whitening toothpastes can help keep the teeth from turning yellow again, he adds.
But Mayher also warns of potential problems. Over time, he says, an abrasive toothpaste could wear away the outer layer of enamel on a tooth, exposing the yellowish dentin beneath. "You could actually end up making your teeth look less white." Plus, the abrasives in whitening toothpastes can be painful for some people, so those with sensitive teeth should be careful, he adds.
In a study published this year in the Journal of Clinical Dentistry, investigators at Thermetric Technologies Inc., a dental research firm in Noblesville, Ind., and the Health Science Research Center at Indiana University-Purdue University in Fort Wayne tested the abrasiveness and cleaning power of 26 whitening toothpastes on enamel from cow teeth. Crest White Vivid ranked 17th in terms of cleaning but was the fourth-most abrasive. Anything with an RDA (relative dentin abrasion) score above 100 is generally considered highly abrasive, and anything above 150 is considered potentially damaging to enamel. Crest White Vivid scored above 200.
Rembrandt Intense Stain was only mildly abrasive (RDA about 90), but it was also in the middle of the pack in terms of cleaning power. The toothpaste with the top marks for stain removal — Ultrabrite Advanced Whitening from Colgate — was also one of the most abrasive, reaching an RDA of about 260. The study didn't include either Crest 3D White Advanced Vivid or Rembrandt's Deeply White.
In general, the most effective whitening toothpastes are also the most abrasive, says Bruce Schemehorn, the lead author of the study. To his mind, the ideal whitening toothpaste would be both gentle on the enamel and tough on stains. "I've been studying this for 30 years, and I haven't found it yet," he says.
While strips and trays work by soaking the teeth in bleach for long stretches of time, whitening toothpastes take a faster approach. They generally rely on abrasives (toothpaste companies prefer to call them "polishers") that help remove surface stains left behind by coffee, cigarettes, juices and foods.
Crest, a Procter & Gamble brand, offers 3D White Vivid and 3D White Advanced Vivid. Both varieties contain hydrated silica as an abrasive. The advanced version, which comes out of the tube in two separate chambers, also has sodium hexametaphosphate, a compound that helps loosen the stains so the abrasives can do their job. Users are instructed to brush after meals or at least twice a day. Expect to pay about $4 for the 4.1-ounce tube of either product.
Rembrandt, a Johnson & Johnson company, has built its brand around the promise of whitening. Both its Intense Stain and Deeply White toothpastes contain hydrated silica. Deeply White also has the bleaching agent urea peroxide. Users are instructed to brush twice daily "and after meals if possible." A 3-ounce tube of Intense Stain costs about $8, and a 2.6-ounce tube of Deeply White goes for about $7.
The claims
The label for Crest 3D White Vivid claims it can remove 80% of surface stains in two weeks, and the advanced version says it removes 90% of surface stains in the same period of time. Alissa Fitzgibbons, a spokeswoman for Procter & Gamble, says "a lot of consumers see great results" from the toothpastes. She adds that people who want extra whitening often try Crest WhiteStrips or other bleaching products.
The Rembrandt website says the peroxide in the Deeply White toothpaste targets "deep stains" in the teeth and that Intense Stain is "expertly formulated to remove tough stains, prevent new stains from sticking and actively restore and strengthen tooth enamel." Teresa Panas, a spokeswoman for Johnson & Johnson, says that Deeply White "polishes away surface stains and safely whitens below the enamel." She also says that Intense Stain contains "micro-polishers" that go to work on stains "like red wine, soda, coffee and tobacco."
The bottom line
There's no doubt that whitening toothpastes can clean stains off teeth and give them a little extra gleam. But the term "whitening" is misleading, says Dr. Vincent Mayher, a Haddonfield, N.J., dentist and the past president of the Academy of General Dentistry. Unlike trays and strips that can bleach deep within a tooth, he explains, toothpastes can reach only the surface. Besides, he adds, bleaches in toothpastes are useless because they'll get rinsed away before they do anything.
Still, getting rid of surface stains can really brighten a smile, and Mayher says whitening toothpastes can be worth a try as long as a user doesn't expect miracles. If a person has his or her teeth bleached, whitening toothpastes can help keep the teeth from turning yellow again, he adds.
But Mayher also warns of potential problems. Over time, he says, an abrasive toothpaste could wear away the outer layer of enamel on a tooth, exposing the yellowish dentin beneath. "You could actually end up making your teeth look less white." Plus, the abrasives in whitening toothpastes can be painful for some people, so those with sensitive teeth should be careful, he adds.
In a study published this year in the Journal of Clinical Dentistry, investigators at Thermetric Technologies Inc., a dental research firm in Noblesville, Ind., and the Health Science Research Center at Indiana University-Purdue University in Fort Wayne tested the abrasiveness and cleaning power of 26 whitening toothpastes on enamel from cow teeth. Crest White Vivid ranked 17th in terms of cleaning but was the fourth-most abrasive. Anything with an RDA (relative dentin abrasion) score above 100 is generally considered highly abrasive, and anything above 150 is considered potentially damaging to enamel. Crest White Vivid scored above 200.
Rembrandt Intense Stain was only mildly abrasive (RDA about 90), but it was also in the middle of the pack in terms of cleaning power. The toothpaste with the top marks for stain removal — Ultrabrite Advanced Whitening from Colgate — was also one of the most abrasive, reaching an RDA of about 260. The study didn't include either Crest 3D White Advanced Vivid or Rembrandt's Deeply White.
In general, the most effective whitening toothpastes are also the most abrasive, says Bruce Schemehorn, the lead author of the study. To his mind, the ideal whitening toothpaste would be both gentle on the enamel and tough on stains. "I've been studying this for 30 years, and I haven't found it yet," he says.
订阅：
博文 (Atom)