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Treatment and restoration of fractured crowns
226
J. Dent.
1987;
15:
No. 5
of 5 seconds exhibited as high a bond strength as that of a 40-second etching or by duplex etching for 5 seconds. The changes in dentine surfaces treated with 40 per cent phosphoric acid gel were less than those with the phosphoric acid solution. When the dentine was etched with the phosphoric acid solution, the openings of the dentinal tubules were enlarged rapidly, even with 5 second’s etching. The phosphoric acid solution did not have any unfavourable effect on the bond strength to dentine after various washing procedures following etching. On the other hand, the phosphoric acid gel caused a slight decrease in the bond strength (approximately 196 N/ cm*) in the case of short washing time. The phosphoric acid gel contains silicic particles (aerosil) for increased viscosity. These particles were deposited on the etched dentine surfaces and could not be removed by washing. The particles remaining were particularly noticeable after a short washing time. Although the gel is convenient to use in the clinic it is liable to decrease the bond strength of the composite to the etched dentine. The viscosity of the etchants should be increased by use of an agent other than silicic particles. (13 references) H. Hisamitsu
Observation of facial changes in Japanese vowel pronunciation through Moire topography. Kashiwabara N., Yabae M., Yotsuya H. et al. (1986) Bull. Tokyo Dent. Coil. 4, 149-l 61. In this detailed three-dimensional study of facial changes during vowel pronunciation, Moire photogrammetry was used. With this technique topographic grids are projected on to the subject during photography. Thirty-two subjects participated. In speech the Japanese ‘a’ and ‘0’ sounds are long, ‘i’ medium, and ‘e’ and ‘u’ short. Mouth opening with downward and backward chin movement was greatest for the sound ‘a’. and decreased for ‘o’, ‘e’, ‘i’ and ‘u’ sounds respectively. This led to varying amounts of volume reduction in the external portion of the upper lip, the chin and the lower lip. The volume of the lateral periorbital tissues increased with ‘i’ and was reduced with ‘0’. Downward movement of the modiolus was also greatest for ‘a’ and decreased for ‘0’ and ‘u’ successively. With ‘i’ upward movement occurred. Without any further modiolar movement ‘a’, ‘e’ or ‘i’ could be sounded, depending on the amount of mouth opening. With the modiolus forward ‘0’ or ‘u’ was produced. The position of the modiolus has a decisive influence on vowel pronunciation. Volumetric changes of the lips and adjacent tissues during vowel pronunciation are due to a combination of chin and modiolus movement. (12 references) M. J. Shapiro
A study of human condylar guidance by direct measurement of crania. Ballesteros E.J.C., Herero C. J. C. and Lopez M. L. (1986) Rev. Esp. Estomatol. 34, 400-420. These authors obtained new data concerning the anatomical condylar guidance angle (CGA) of the temporomandibular joint and its relationship to the clinical condylar path angle (CPA). The CGA was measured from
enlargements of standardized photographs of each of 44 randomly chosen crania. The age and sex were determined by anatomical criteria. The figures for the CPA were obtained from the work of another Spanish investigator, Roy0 Villanova. Although the average CGA was 46”, 38.5 per cent of specimens fell into the 56-60” category. In 52 per cent of crania there was a difference between left and right CGAs of O-5” and in 36 per cent 6-10”; in the remaining 12 per cent, differences in values of up to IO” were found. The difference between the average CGA values of males and females, was negligible. However, the largest angle of 47.5” was found in a male and the smallest of 25.5” in a female. The average clinical CGA was approximately 7” less than the anatomical CPA. There was no difference between the CPA values on each side in IO.5 per cent of patients. In most patients this is O-5” but values of up to 20” are occasionally found. In males the average difference of 10” approximated the overall average, but in females the difference between the two sides was negligible. The authors infer that the difference between the CGA and CPA reflects anatomical and functional influences. The sex difference in some of the features was attributed to the virtual absence of remodelling in the glenoid fossa in females. (20 references) M. J. Shapiro
Treatment and restoration of fractured crowns. Zeng Mei-ling et al. (1986) J. Clin. Stomatol. 2,(3), 133-l 34. Twenty cases of fractured crowns (8 males, 14 females, age range 27-57 years) were selected for this study. Fracture of first permanent molars was most frequently encountered, as this tooth is subject to the largest occlusal load. Pulpless teeth may also be easily fractured because of their brittleness. Following periodontal and pulpal treatment (pulpectomy or endodontic treatment), the fractured teeth were fixed with stainless steel wires. Impressions of the teeth were then taken in order to fabricate metal full veneer crowns. The short-term and long-term results of this treatment were satisfactory. (3 references) Liao Fang-gang and Wei Yi Beijing
Effect of dental plaque formation on the degradation of restorative materials-pli changes under the dental plaque formed on the different restorations. Tsujimura M., Machida T., Katsumata K. et al. (1986) Jap. J. Conserv. Dent. 29, 1384-l 390. In this study, a composite resin (Silux; 3M. USA) and a glass-ionomer cement (Fuji ionomer type II; GC, Japan) were used with sectioned human enamel used as a control. A transistor pH electrode (Kuraray, Japan) was used to measure pH change. The electrode was placed on the restorative materials and enamel specimens respectively mounted on the occlusal surface of an artificial resin tooth on a removable denture designed for this investigation. In order to measure pH changes in the plaque formed on the specimens after 3, 5 and 7 days of denture wearing, 25 ~1 of 1 *O per cent sucrose solution was
J. Dent.
1987;
15:
No. 5
of 5 seconds exhibited as high a bond strength as that of a 40-second etching or by duplex etching for 5 seconds. The changes in dentine surfaces treated with 40 per cent phosphoric acid gel were less than those with the phosphoric acid solution. When the dentine was etched with the phosphoric acid solution, the openings of the dentinal tubules were enlarged rapidly, even with 5 second’s etching. The phosphoric acid solution did not have any unfavourable effect on the bond strength to dentine after various washing procedures following etching. On the other hand, the phosphoric acid gel caused a slight decrease in the bond strength (approximately 196 N/ cm*) in the case of short washing time. The phosphoric acid gel contains silicic particles (aerosil) for increased viscosity. These particles were deposited on the etched dentine surfaces and could not be removed by washing. The particles remaining were particularly noticeable after a short washing time. Although the gel is convenient to use in the clinic it is liable to decrease the bond strength of the composite to the etched dentine. The viscosity of the etchants should be increased by use of an agent other than silicic particles. (13 references) H. Hisamitsu
Observation of facial changes in Japanese vowel pronunciation through Moire topography. Kashiwabara N., Yabae M., Yotsuya H. et al. (1986) Bull. Tokyo Dent. Coil. 4, 149-l 61. In this detailed three-dimensional study of facial changes during vowel pronunciation, Moire photogrammetry was used. With this technique topographic grids are projected on to the subject during photography. Thirty-two subjects participated. In speech the Japanese ‘a’ and ‘0’ sounds are long, ‘i’ medium, and ‘e’ and ‘u’ short. Mouth opening with downward and backward chin movement was greatest for the sound ‘a’. and decreased for ‘o’, ‘e’, ‘i’ and ‘u’ sounds respectively. This led to varying amounts of volume reduction in the external portion of the upper lip, the chin and the lower lip. The volume of the lateral periorbital tissues increased with ‘i’ and was reduced with ‘0’. Downward movement of the modiolus was also greatest for ‘a’ and decreased for ‘0’ and ‘u’ successively. With ‘i’ upward movement occurred. Without any further modiolar movement ‘a’, ‘e’ or ‘i’ could be sounded, depending on the amount of mouth opening. With the modiolus forward ‘0’ or ‘u’ was produced. The position of the modiolus has a decisive influence on vowel pronunciation. Volumetric changes of the lips and adjacent tissues during vowel pronunciation are due to a combination of chin and modiolus movement. (12 references) M. J. Shapiro
A study of human condylar guidance by direct measurement of crania. Ballesteros E.J.C., Herero C. J. C. and Lopez M. L. (1986) Rev. Esp. Estomatol. 34, 400-420. These authors obtained new data concerning the anatomical condylar guidance angle (CGA) of the temporomandibular joint and its relationship to the clinical condylar path angle (CPA). The CGA was measured from
enlargements of standardized photographs of each of 44 randomly chosen crania. The age and sex were determined by anatomical criteria. The figures for the CPA were obtained from the work of another Spanish investigator, Roy0 Villanova. Although the average CGA was 46”, 38.5 per cent of specimens fell into the 56-60” category. In 52 per cent of crania there was a difference between left and right CGAs of O-5” and in 36 per cent 6-10”; in the remaining 12 per cent, differences in values of up to IO” were found. The difference between the average CGA values of males and females, was negligible. However, the largest angle of 47.5” was found in a male and the smallest of 25.5” in a female. The average clinical CGA was approximately 7” less than the anatomical CPA. There was no difference between the CPA values on each side in IO.5 per cent of patients. In most patients this is O-5” but values of up to 20” are occasionally found. In males the average difference of 10” approximated the overall average, but in females the difference between the two sides was negligible. The authors infer that the difference between the CGA and CPA reflects anatomical and functional influences. The sex difference in some of the features was attributed to the virtual absence of remodelling in the glenoid fossa in females. (20 references) M. J. Shapiro
Treatment and restoration of fractured crowns. Zeng Mei-ling et al. (1986) J. Clin. Stomatol. 2,(3), 133-l 34. Twenty cases of fractured crowns (8 males, 14 females, age range 27-57 years) were selected for this study. Fracture of first permanent molars was most frequently encountered, as this tooth is subject to the largest occlusal load. Pulpless teeth may also be easily fractured because of their brittleness. Following periodontal and pulpal treatment (pulpectomy or endodontic treatment), the fractured teeth were fixed with stainless steel wires. Impressions of the teeth were then taken in order to fabricate metal full veneer crowns. The short-term and long-term results of this treatment were satisfactory. (3 references) Liao Fang-gang and Wei Yi Beijing
Effect of dental plaque formation on the degradation of restorative materials-pli changes under the dental plaque formed on the different restorations. Tsujimura M., Machida T., Katsumata K. et al. (1986) Jap. J. Conserv. Dent. 29, 1384-l 390. In this study, a composite resin (Silux; 3M. USA) and a glass-ionomer cement (Fuji ionomer type II; GC, Japan) were used with sectioned human enamel used as a control. A transistor pH electrode (Kuraray, Japan) was used to measure pH change. The electrode was placed on the restorative materials and enamel specimens respectively mounted on the occlusal surface of an artificial resin tooth on a removable denture designed for this investigation. In order to measure pH changes in the plaque formed on the specimens after 3, 5 and 7 days of denture wearing, 25 ~1 of 1 *O per cent sucrose solution was