In defence of this situation, it has been claimed that while the ADA is prepared to promote the patented Branemark system for osseointegration it doesmot afford the same facility to DOFOS. However, there is a vast difference between the commercial patenting of a product which is available on the open market and about which scientific evidence for its efficacy abounds in the public domain, and the patenting of a system which, it would seem, limits dissemination of its methodology to those who agree to be bound by the terms of a legal contract. Let us have open discussion and informed opinion so that all can share in the supposed benefits of this treatment system. This open dissemination of knowledge has always been the hallmark of a profession like ours, and it is to be hoped it will always remain so!
DENTAL MATERIALS AND DENTAL PULP Sir, The article by Hume and Massey (Aust Dent J 1990;35:32-7) was a timely and comprehensive coverage of how, why, and with what pulps are kept alive. In the latter part of the paper three choices of therapeutic approach are discussed. The first two, zinc oxide-eugenol and calcium hydroxidesalicylate, are clearly categorized as cements, whereas in the discussion of the third, Lederrnix,* the paste version of this is not clearly distinguished from the powder and liquid type which becomes a cement. The paste is non-setting and must always be removed prior to final restoration, whereas the cement may be placed on a more permanent basis. These Ledermix products have now been on the market, virtually unaltered, for more than 25 years and their credentials are unquestionably better established now than was the case say a decade ago. Incidentally, a good deal of the research that has brought about this state of affairs, particularly in respect of the paste, has been and still is done in Australia. It is, therefore, reasonable to expect an ongoing and probably increasing place for these materials which years ago were identified as A and ‘Lederlc, Wolfratshausen, West Germany. Australian Dental Journal 1990;35:3.
B to distinguish the paste from the cement in a nomenclatural sense. Now the manufacturer simply describes both forms as being Ledermix, even though less than 3 per cent of the identified components are common. This creates quite a basis for confusion in the minds of many dentists and this confusion can spill over into the scientific literature. Page 36 of Hume and Massey’s paper is no exception in this regard. A simple proposal to achieve a less ambiguous situation is that the manufacturer change the name of one (or both) of them. More specifically, the cement material could retain the description ‘Ledermix’ because it does have to be mixed - or better still be called Ledercem or Lederset. The paste material which is simply dispensed straight from its tube could be retitled Lederpaste. The practising profession could then more readily know exactly what product was being referred to in either the literature or in professional dialogue and correctly use whichever one of them was appropriate in a particular clinical situation. A.
P. MARTIN.
Suite 64, 183 Macquarie Street, Sydney, NSW, 2000. 15 March 1990. 301
DENTAL MATERIALS AND DENTAL PULP Sir, Dr Martin is right. It is confusing to have two physically distinct products which have quite different clinical applications marketed under the same name. T h e principal therapeutic components, triamcinolone and demeclocycline, are common to both, but reasonable clinical usage of the two is quite different. Massey and I were referring to the cement.
Sir, We note Dr Martin’s letter with interest and are very appreciative of his feedback. T h e most obvious answer would appear to be to label the paste as ‘Ledermix Paste’ to differentiate it from the cement. We will look into this. J. W. KETELBEY, Medical and Clinical Research Director, Lederle Laboratories Division.
W. R. HUME. Department of Operative Dentistry, Westmead Hospital Dental Clinical School, Westmead, NSW, 2145. 2 May 1990.
Cyanamid Australia Pty Ltd, 4 Gibbon Road, Baulkham Hills, NSW, 2153. 7 May 1990.
CRACKED TOOTH SYNDROME Sir, I was most interested to read the recent article on Cracked Tooth Syndrome (Aust Dent J 1990;35: 105-12)as indeed all general practitioners would be if the incidence is as high as suggested: 80-100 per year in the average general practice. This certainly has been my experience, and indicates that I would have treated 2400 to 3000 cases since 1960, which is about the time I first became aware of the condition. T h e first indication to me came when patients reported with a fractured cusp. Examining my records showed that hypersensitivity to chewing and sometimes cold had been reported 6-18 months earlier. This hypersensitivity resulted with the fracture of the cusp. Once aware of the condition and having developed a regimen for diagnosis, I treated two with full crowns which were unsuccessful and I was somewhat embarrassed. Subsequently, I made a practice of removing the involved cusp before restoring with pin amalgam or crown. For many years this produced almost 100 per cent success. Since the advent of posterior composites, it has become possible to restore these teeth without removal of the fractured cusp or cusps, and this is a much simplified technique which was not mentioned by Ehrmann and Tyas in their article. T h e strength of the bonding is sufficient to prevent the crack ‘springing’ and the symptoms disappear. Needless to say, as with all posterior composites, fastidious attention to detail is essential. Also it is not advisable to rely on bonding parallel to the direction of enamel rods as these may separate. Increased bevelling, particularly in the embrasures 302
of Class I1 cavities, is advisable to increase the area and strength of bonding to the ends of the enamel rods. Success with this technique has been almost 100 per cent and the few failures can probably be attributed to direct pulpal involvement of the crack as suggested in the article. It is interesting to surmise whether some such pulpal involvements are in fact successfully ‘sealed’ by the bonding of dentine which is now possible. I would like to comment on two other aspects in the article. T h e reported high incidence of cracked tooth syndrome (CTS) in teeth which are unrestored or restored with Class I amalgams is quite contrary to my clinical experiences. I cannot remember a case with an unrestored tooth and extensively few with Class I restorations. T h e incidence with Class I1 restorations is extremely high especially when they have been prepared conscientiously according to Black’s principles with sharp line angles and flaring proximal boxes. My second comment concerns the high incidence of cracked teeth which have no symptoms. These are usually revealed during the removal of an old amalgam restoration for some other reason. I wonder if the authors can provide some explanation for the presence of symptoms in some cases and not in others as it would appear, from the success of conservative treatment, that direct pulpal involvement is uncommon. JOHN
SOUTHWICK.
240 Victoria Avenue, Chatswood, NSW, 2067. 7 May 1990. Australian Dental Journal 1990;35:3.
DENTAL MATERIALS AND DENTAL PULP Sir, The article by Hume and Massey (Aust Dent J 1990;35:32-7) was a timely and comprehensive coverage of how, why, and with what pulps are kept alive. In the latter part of the paper three choices of therapeutic approach are discussed. The first two, zinc oxide-eugenol and calcium hydroxidesalicylate, are clearly categorized as cements, whereas in the discussion of the third, Lederrnix,* the paste version of this is not clearly distinguished from the powder and liquid type which becomes a cement. The paste is non-setting and must always be removed prior to final restoration, whereas the cement may be placed on a more permanent basis. These Ledermix products have now been on the market, virtually unaltered, for more than 25 years and their credentials are unquestionably better established now than was the case say a decade ago. Incidentally, a good deal of the research that has brought about this state of affairs, particularly in respect of the paste, has been and still is done in Australia. It is, therefore, reasonable to expect an ongoing and probably increasing place for these materials which years ago were identified as A and ‘Lederlc, Wolfratshausen, West Germany. Australian Dental Journal 1990;35:3.
B to distinguish the paste from the cement in a nomenclatural sense. Now the manufacturer simply describes both forms as being Ledermix, even though less than 3 per cent of the identified components are common. This creates quite a basis for confusion in the minds of many dentists and this confusion can spill over into the scientific literature. Page 36 of Hume and Massey’s paper is no exception in this regard. A simple proposal to achieve a less ambiguous situation is that the manufacturer change the name of one (or both) of them. More specifically, the cement material could retain the description ‘Ledermix’ because it does have to be mixed - or better still be called Ledercem or Lederset. The paste material which is simply dispensed straight from its tube could be retitled Lederpaste. The practising profession could then more readily know exactly what product was being referred to in either the literature or in professional dialogue and correctly use whichever one of them was appropriate in a particular clinical situation. A.
P. MARTIN.
Suite 64, 183 Macquarie Street, Sydney, NSW, 2000. 15 March 1990. 301
DENTAL MATERIALS AND DENTAL PULP Sir, Dr Martin is right. It is confusing to have two physically distinct products which have quite different clinical applications marketed under the same name. T h e principal therapeutic components, triamcinolone and demeclocycline, are common to both, but reasonable clinical usage of the two is quite different. Massey and I were referring to the cement.
Sir, We note Dr Martin’s letter with interest and are very appreciative of his feedback. T h e most obvious answer would appear to be to label the paste as ‘Ledermix Paste’ to differentiate it from the cement. We will look into this. J. W. KETELBEY, Medical and Clinical Research Director, Lederle Laboratories Division.
W. R. HUME. Department of Operative Dentistry, Westmead Hospital Dental Clinical School, Westmead, NSW, 2145. 2 May 1990.
Cyanamid Australia Pty Ltd, 4 Gibbon Road, Baulkham Hills, NSW, 2153. 7 May 1990.
CRACKED TOOTH SYNDROME Sir, I was most interested to read the recent article on Cracked Tooth Syndrome (Aust Dent J 1990;35: 105-12)as indeed all general practitioners would be if the incidence is as high as suggested: 80-100 per year in the average general practice. This certainly has been my experience, and indicates that I would have treated 2400 to 3000 cases since 1960, which is about the time I first became aware of the condition. T h e first indication to me came when patients reported with a fractured cusp. Examining my records showed that hypersensitivity to chewing and sometimes cold had been reported 6-18 months earlier. This hypersensitivity resulted with the fracture of the cusp. Once aware of the condition and having developed a regimen for diagnosis, I treated two with full crowns which were unsuccessful and I was somewhat embarrassed. Subsequently, I made a practice of removing the involved cusp before restoring with pin amalgam or crown. For many years this produced almost 100 per cent success. Since the advent of posterior composites, it has become possible to restore these teeth without removal of the fractured cusp or cusps, and this is a much simplified technique which was not mentioned by Ehrmann and Tyas in their article. T h e strength of the bonding is sufficient to prevent the crack ‘springing’ and the symptoms disappear. Needless to say, as with all posterior composites, fastidious attention to detail is essential. Also it is not advisable to rely on bonding parallel to the direction of enamel rods as these may separate. Increased bevelling, particularly in the embrasures 302
of Class I1 cavities, is advisable to increase the area and strength of bonding to the ends of the enamel rods. Success with this technique has been almost 100 per cent and the few failures can probably be attributed to direct pulpal involvement of the crack as suggested in the article. It is interesting to surmise whether some such pulpal involvements are in fact successfully ‘sealed’ by the bonding of dentine which is now possible. I would like to comment on two other aspects in the article. T h e reported high incidence of cracked tooth syndrome (CTS) in teeth which are unrestored or restored with Class I amalgams is quite contrary to my clinical experiences. I cannot remember a case with an unrestored tooth and extensively few with Class I restorations. T h e incidence with Class I1 restorations is extremely high especially when they have been prepared conscientiously according to Black’s principles with sharp line angles and flaring proximal boxes. My second comment concerns the high incidence of cracked teeth which have no symptoms. These are usually revealed during the removal of an old amalgam restoration for some other reason. I wonder if the authors can provide some explanation for the presence of symptoms in some cases and not in others as it would appear, from the success of conservative treatment, that direct pulpal involvement is uncommon. JOHN
SOUTHWICK.
240 Victoria Avenue, Chatswood, NSW, 2067. 7 May 1990. Australian Dental Journal 1990;35:3.
