Influence of beverage type and ingestion time on tooth corrosion / 대한치과재료학회지

This study was conducted to analyze the effects of beverages on tooth corrosion by selecting drinks that are enjoyed by modern people. Drinks were selected for carbonated beverages (Coca Cola), energy drinks (Red Bull), orange juice, beer (Hite) and water (Evian). Bovine tooth was immersed for 1 hour, 24 hours and 48 hours. The root mean square (RMS) values were obtained by scanning the bovine tooth at pre-immersion and immersion time after impression making. Two-way ANOVA, one-way ANOVA, and Tukey-test were used to compare differences between groups (α=0.05). The RMS value tended to increase with longer immersion times in all beverages, and there was a significant difference (p < 0.05) between before immersion-1hr and before immersion-48 hr. The mean of RMS according to the type of beverage was significantly different and there was a significant difference according to the change of immersion time (p < 0.05). In order to prevent tooth corrosion, it is necessary to change the method of ingestion or to reduce the time of ingestion.

Wear properties of lithium disilicate glass-ceramic and bovine tooth enamel:An in vitro study / 实用口腔医学杂志

Objective:To investigate the wear characteristics of bovine enamel and lithium disilicate glass ceramic under simulated oral environment.Methods:18 cylindrical lithium disilicate glass-ceramic specimens with the length of 8 mm and diameter of 3 mm were randomly divided into 2 groups (n =9),9 lithium disilicate glass-ceramic specimens and 9 bovine enamel specimens were served as the antagonists respectively.The specimens were then loaded in a wear simulator and subjected to friction force of 10 N for 540 000 cycles in artificial saliva and room temperature(speed 100 r/min,turning radius of 2.5 mm,uniform circular motion) condition.During the testing,10 checkpoints were applied to measure the height loss of the specimens with 3D profilometer,then wear curves were plotted.Scanning electron microscopy were applied to investigate the worn surfaces at different wear stages.Results:At every checkpoints,bovine enamel wear height loss was larger than the lithium disilicate specimens (P ＜ 0.05);bovine enamel wear curve exhibits a runningin period,steady wear period and severe wear period 3 stages of wear,while wear curves of lithium disilicate glass ceramics exhibit onlyrunning-in period and steady wear period 2 wear stages.Both groups had the corresponding micro-morphological features in different periods.Conclusion:Bovine enamel and lithium disilicate glass ceramics show a phase dynamic evolution law under the simulated oral environment.Bovine enamel is more susceptible to wear than lithium disilicate,suggesting that clinical attention should be paid to prevent the excessive wear of natural teeth caused by lithium disilicate glass ceramic restorations.

Radiodensity evaluation of dental impression materials in comparison to tooth structures

In the most recent decades, several developments have been made on impression materials' composition, but there are very few radiodensity studies in the literature. It is expected that an acceptable degree of radiodensity would enable the detection of small fragments left inside gingival sulcus or root canals. OBJECTIVE: The aim of this study was to determine the radiodensity of different impression materials, and to compare them to human and bovine enamel and dentin. MATERIAL AND METHODS: Twenty-five impression materials, from 5 classes, were studied: addition and condensation silicones, polyether, polysulfides and alginates. Five 1-mm-thick samples of each material and tooth structure were produced. Each sample was evaluated 3 times (N=15), being exposed to x-ray over a phosphor plate of Digora digital system, and radiodensity was obtained by the software Digora for Windows 2.5 Rev 0. An aluminum stepwedge served as a control. Data were subjected to Kruskal-Wallis and Dunn's method (α=0.05). RESULTS: Different materials and respective classes had a different behavior with respect to radiodensity. Polysulfides showed high values of radiodensity, comparable to human enamel (p>0.05), but not to bovine enamel (p<0.05). Human dentin was similar only to a heavy-body addition silicon material, but bovine dentin was similar to several materials. Generally, heavy-body materials showed higher radiodensity than light-body ones (p<0.05). CONCLUSION: Impression materials' radiodensity are influenced by composition, and almost all of them would present a difficult detection against enamel or dentin background in radiographic examinations.

Comparison of resin push-out strength to root dentin of bovine- and human-teeth.

Aim : To compare the push-out strength of bovine- and human-root dentin and, thus, evaluate the suitability of bovine-root dentin to substitute human-root dentin for bond strength testing. Materials and Methods : Ten single-rooted human-teeth and ten bovine incisors were prepared using a #3 bur of a fiber post system (12 mm long). The posts were duplicated with resin cement (Duolink). The root canals were treated with All Bond 2 adhesive system and the resin posts were cemented using Duolink. The specimens were cut perpendicular to their long axis, yielding disc-specimens with 1.5 mm thickness, which were submitted to a push-out test (1 mm/min). Ten bond strength values per group (n = 10) were used for statistical analysis (Student t test, a =.05). Results : Statistically significant differences were found for the bond strength values between bovine- (4.1 ± 1.3 MPa) and human-root dentin (8.6 ± 5.7 MPa) (P =.0001). Conclusion : The push-out strengths of bovine- and human-root dentin were statistically different.