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PubMed1994

Evaluation of surface smoothness detected by a periodontal probe.

An investigation was designed to determine whether or not the required smoothness has been reached. This is still a controversial subject among clinicians. Ten cylindrical metal samples of equal sizes with various degrees of smoothness were prepared, and their degrees of smoothness were assessed in a blind manner by 14 periodontists, who were asked to group them as smooth or rough using a periodontal probe. Along with the metal samples, the roughness of root surfaces smoothed in clinics was also evaluated using a Profilometer. The average value defined as a smooth surface on a max.-min. scale was 1.86 +/- 0.42, and values above 3.57 were considered to be rough. Consequently, decisions taken using the sense of touch about the smoothness of a surface were confirmed to be reliable for clinical use.

Carbon↗
PubMedDate not supplied

Finishing and polishing of a hybrid composite and a heat-pressed glass ceramic.

This study assessed the finishing and polishing of a hybrid composite and a glass-ceramic. Ninety Tetric specimens were divided into three groups of 30 specimens and finished with three different finishing procedures. The 30 specimens were subsequently subdivided into six groups of five and polished using the following polishing systems: Sof-Lex disks, the Ceramiste kit, a diamond polisher, Diafix-oral, the MPS gel and the Politip system. Seventy-five IPS-Empress specimens were divided into groups of 25 and finished with three different procedures. The 25 specimens were then subdivided into five groups of five and polished with the same systems, except for the Politip technique. The polished surfaces were evaluated quantitatively by laser stylus profilometry with respect to Ra and profile-length-ratio (LR). Qualitative assessment was carried out by SEM. Quantitative results were examined statistically by one- and two-way Anova and LSD test with significance level of 0.05. The lowest roughness on composite specimens was achieved by the MPS gel and Diafix after finishing according to FM 3 and FM 2. With respect to all methods used, there were no significant differences among the five methods with the lowest Ra-values. The ceramic specimens were able to be polished to lower roughness values (p<0.001 for LR). The best results on ceramic surfaces were achieved with the MPS system after finishing according to FM 3 and FM 2. There were no significant differences among the three methods with the lowest Ra-values and the glazed surface. SEM evaluation largely confirmed the quantitative results. Composite specimens exhibited signs of selective resin matrix removal when the Ceramiste system or the Politip system were used.

Aluminum Oxide↗
PubMed2006

Molecular conformations of protonated dipropylamine in AlPO4-11, AlPO4-31, SAPO-34, and AlPO4-41 molecular sieves.

The host-guest interactions in AlPO4-11, AlPO4-31, SAPO-34, and AlPO4-41 molecular sieves prepared using the same organic structure-directing agent, i.e., dipropylamine, are investigated by a combination of Raman, 13C and 1H MAS NMR, and computer modeling studies. It was found that the organic molecules trapped within the pores of these four AlPO4-based materials exist as their protonated form and adopt distinct conformations in order to fit well with the pore structure of each host. In particular, the presence of two different types of conformations of protonated dipropylamine in the circular 12-ring channels of AlPO4-31 has been ascertained.

Aluminum Compounds↗
PubMed2002

Microtensile bond strength of self-etching adhesives to ground and unground enamel.

PURPOSE: The purpose of this study was to assess the bond strength of two self-etching primers (SEP) to ground and unground enamel. MATERIALS AND METHODS: Seventy-two bovine incisors were used in this study. The buccal enamel surface of 36 teeth was ground flat to resemble freshly cut enamel. The rest of the teeth were left intact. Two SEPs--Clearfil SE Bond, Kuraray (CSE) and Prompt L-Pop (3M ESPE) (LP)--and a conventional adhesive system, Scotchbond Multi-Purpose (3M ESPE) (SBMP) as a control, were used to bond a composite button to prepared and unprepared enamel. Microtensile test specimens were trimmed, resulting in a cylindrical cross-sectional area (0.21 mm2 to 0.47 mm2). These specimens were subjected to a tensile force at 1 mm/min until failure. Differences between adhesives and surface preparation were determined by two-way ANOVA. The samples were observed under SEM to evaluate the mode of failure. RESULTS: Bond strength values in MPa (SD) obtained from pooled data in descending order were: SBMP ground 44.54 (5.96), LP unground 42.97 (7.90), CSE unground 41.67 (11.28), LP ground 41.07 (12.07), CSE ground 38.56 (8.78), and SBMP unground 37.60 (9.55). No statistically significant differences were found (p = 0.5061) between surface preparation or adhesive systems. The mean in MPa (SD) of all the specimens that failed at the adhesive joint were: LP unground 47.13 (14.65), SBMP ground 45.28 (7.33), CSE unground 41.40 (11.07), SBMP unground 41.1 (10.04), CSE ground 39.96 (11.83), and LP ground 39.92 (15.45). No statistically significant differences were found (p = 0.5863). Failure occurred mainly at the adhesive interface. CONCLUSIONS: Surface preparation and adhesive treatment had no influence on resin composite microtensile bond strength to bovine enamel.

Acid Etching, Dental↗
PubMedDate not supplied

Effects of Er:YAG and Nd:YAP laser irradiation on the surface roughness and free surface energy of enamel and dentin: an in vitro study.

Sixty-seven extracted molars were selected (134 samples). Dentin and enamel samples were prepared by buccal and lingual surface sectioning to expose a planar enamel or dentin surface. For the roughness study, 80 samples were randomly assigned to eight groups. Enamel and dentin surfaces were etched with a 37% phosphoric acid solution, irradiated with an Er:YAG laser or irradiated with a Nd:YAP laser. Samples were then observed in SEM using BSE. For the free-surface energy study, 54 samples received the same treatment as above. Two contact angle measurements were made on each surface using a goniometer. Data were analyzed by a non-parametric statistical test. Morphological changes on enamel and dentin were greater with acid-etch and Er:YAG laser than with Nd:YAP laser. Free surface energy was significantly greater with acid-etch or Er:YAG laser than with Nd:YAP laser (p < 0.001).

Acid Etching, Dental↗
PubMed2004

The effects of air-abrasion on dentin, enamel, and metal bonding.

PURPOSE: To determine the most effective emission pressure for producing effective bond strengths of an adhesive resin to enamel, dentin and metal. METHODS: Test specimens were prepared from bovine teeth for enamel and dentin samples and from alloy disks cast in an Ag-Pd-Cu-Au alloy. All specimen substrates were ground flat and finished with 600-grit SiC paper. The prepared specimens were randomly divided into groups of eight including a control (no abrasion) or air-abraded with 50 microm Al2O3 delivered at three emission pressures of 60, 45 and 30 psi, respectively. Following conditioning, 4-META/MMA-TBB resin was bonded to the specimen surfaces. Specimens were stored in 37 degrees C water for 24 hours, then thermocycled 20,000 times (4 degrees C-60 degrees C), and shear bond tested. Data were analyzed by ANOVA for statistical significance. RESULTS: Enamel specimens showed no statistically significant difference from the control (no air abrasion). Dentin specimens displayed a significant difference from control at 60 and 45 psi, but no significant difference from the control at 30 psi. Alloy specimens showed significantly higher bond strengths from the control at all emission pressures (P< 0.05).

Air Abrasion, Dental↗
PubMed1997

Dose-response relationship of fibrous dusts in intraperitoneal studies.

The relationship between the number of fibers injected intraperitoneally and the occurrence of peritoneal mesotheliomas in rats was investigated using data from a series of carcinogenicity studies with several fibrous dusts. Based on observed tumor incidences ranging between 10 and 90%, the hypothesis of a common slope of dose-response relationships (parallel probit lines in probit analysis) cannot be rejected. In general, parallelism of probit lines is considered an indication of a common mode of action. Analysis of the shape of the dose-response relationship, with one apparent exception, shows virtually linear or superlinear behavior, i.e., from these data, there is no indication of a decrease in carcinogenic potency of an elementary carcinogenic unit at lower doses.

Animals↗
PubMedDate not supplied

Bond strength and SEM observation of CO2 laser irradiated dentin, bonded with simplified-step adhesives.

This study investigated, mechanically and morphologically, whether the dentin surface irradiated by CO2 laser could be a possible adherent when bonded with simplified-step adhesives. Buccal enamel and cementum of extracted human premolars were removed to expose a flat dentin surface. The dentin surfaces were irradiated continuously with CO2 laser at 1.0 W. Before bonding with either a single-bottle adhesive (Single Bond) or a self-etching priming system (Mega Bond), the irradiated dentin surface was treated as follows: no treatment, NaHCO3 powder abrasion and wet-grinding with 600-grit SiC paper. The treated dentin surfaces were bonded to resin composite with either of the two adhesives. Non-irradiated dentin surfaces were also used as control. Resin bonded specimens were stored in water at 37 degrees C for 24 hours and subjected to microtensile bond test. Additionally, to observe the resin/irradiated dentin interface, resin-bonded specimens were similarly prepared, sectioned into slabs, embedded in epoxy resin, polished with diamond pastes, sputter coated Au-Pd and examined with scanning electron microscopy (SEM). After SEM observation, the specimens were further polished with diamond paste to remove the Au-Pd sputter-coat, immersed in HCL and NaOCl and finally observed by SEM again. In the presence of carbonized dentin, microtensile bond strength drastically decreased but recovered to the control value by removing the carbonized dentin layer visually with SiC paper for both adhesive systems. However, the laser-affected dentin that remained on the bonded interface was easily dissolved with NaOCl and HCl.

Air Abrasion, Dental↗
PubMed1991

From contacts and bondings between bone and bioactive glass to bonding of bioactive glass and porcelain to metal alloys, different methods of fracture repair.

Bioactive glass has the ability to bond to bone. In this article the contact between glass and bone is discussed and the development of core alloy for an implant coated with bioactive glass and the oxidation of metal surface in ceramic fusion has been studied. Good bonding of coating materials to core alloys is necessary in dental implants. Using a pull test method we studied the bond strengths between various alloys and some composite materials clinically used to repair fractures of porcelain-veneered dental crowns. An experimental bioglass material was also studied. The bonding of composite materials to metal surfaces etched with hydrofluoric acid was almost as good as the bonding between metal and porcelain, or glass.

Adhesives↗
PubMed1988

Mortality among bearing plant workers exposed to metalworking fluids and abrasives.

Epidemiologic studies have reported associations between gastrointestinal cancer mortality and exposure to cutting fluids and abrasives in metal machining and precision grinding operations. Two previous studies found excess stomach cancer among workers exposed to water-based cutting fluids in bearing plants. This study reports similar findings in a third and larger population. Cause of death and work histories were determined for 1,766 bearing plant workers who died between Jan 1, 1950 and June 30, 1982. Mortality odds ratios (SMOR) and proportional mortality ratios (PMR) revealed significant excesses of gastrointestinal malignancies. The proportional mortality excess for stomach cancer among white men was greatest among those with more than 10 years' exposure in the major grinding group (PMR = 13/3.8 = 3.39; P less than .001). The SMOR by logistic regression for stomach cancer among white men was 2.3 (P = .02) for 25 years' grinding experience. For cancer of the pancreas among white men, there were significant associations with both machining and grinding jobs in straight oil (SMOR = 9.9 and 3.2, respectively, for 25 years duration). These findings could not be explained by confounding due to the ethnic background of the decedents. This study confirms previous evidence that grinding operations using water-based cutting fluids increase the risk for stomach cancer and provides moderate evidence that exposures to straight oil-cutting fluids increase the risk for cancer of the pancreas. There were indications, meriting further investigation, that non-malignant liver disease is associated with cutting fluid exposures and that lung cancer is associated with oil smoke from operations such as forging or heat treating.

Aluminum↗
PubMed2004

Effect of bur type on microtensile bond strengths of self-etching systems to human dentin.

PURPOSE: To compare the microtensile bond strength (microTBS) of five adhesives to human dentin prepared with 600-grit SiC abrasive paper (SiC), a diamond rotary instrument, or a carbide bur. The null hypothesis was that different cavity preparation instruments do not affect adhesion of resin adhesives. MATERIALS AND METHODS: Human molars (n = 45) were randomly divided into three groups according to surface treatment. Each group was bonded using a total-etch adhesive (Single Bond, 3M ESPE), one of three self-etching primer systems (Clearfil SE Bond or ABF, Kuraray; Imperva Fluorobond, Shofu), or a self-etching adhesive (One-Up Bond F, Tokuyama). A 4-mm composite crown was built over the bonded surface. Specimens were stored in water for 24 h at 37 degrees C. They were sectioned into 0.7-mm-thick slabs, trimmed to a cross-sectional area of 1 mm2, and loaded to failure at a crosshead speed of 1 mm/min using a tabletop tester (EZ-Test, Shimadzu). Microtensile bond strength data were analyzed using analysis of variance and Fisher's PLSD test. RESULTS: Surface preparation using a carbide bur generally yielded higher bond strengths than preparation using either a diamond rotary instrument or SiC abrasive paper. SE Bond had the highest mean microTBS of the five adhesives tested. CONCLUSION: Resin-dentin bond strengths can be affected by the type of instrument used to prepare the tooth. Specifically, higher bond strengths might be achieved by using carbide burs rather than diamond cutting instruments.

Acid Etching, Dental↗
PubMedDate not supplied

Polishing occlusal surfaces of direct Class II composite restorations in vivo.

This study evaluated the effects of four polishing methods on the occlusal surfaces of direct Class II composite restorations under clinical conditions. Forty premolars and 40 molars were treated with direct Class II restorations using the hybrid composite Herculite XRV (Kerr). After placement of the restorations, all of which were on occlusal surfaces, they were finished with a sequence of 30 microm diamonds and tungsten carbide instruments. Twenty restorations each, consisting of 10 premolars and 10 molars, were polished with one of the four following methods: (1) Diafix-oral (Mueller-Dental), (2) MPS gel (Premier), (3) P 403-W (Dentsply) and (4) Occlubrush (KerrHawe). Selection of the polishing methods followed a randomized protocol. Replicas of the restored teeth were fabricated and the occlusal surfaces were evaluated quantitatively for roughness with the help of profilometry. Qualitative assessment of the surfaces by SEM was done with respect to roundness of contours and surface roughness. The results were analyzed statistically by two-way ANOVA, chi-squared test for crosstables and Kruskal-Wallis test. Analysis of the quantitative data showed that there was no significant effect of the polishing methods on occlusal surface roughness (p>0.05). Localization of the restoration in premolars or molars had no effect on surface roughness (p>0.05). With respect to occlusal relief, SEM examination revealed that the use of the Occlubrush resulted in significantly more edged contours compared to the other polishing methods (p=0.008). Qualitative roughness evaluation showed that there were no significant differences among the four polishing methods (p>0.05).

Adolescent↗
PubMed2001

New method for divesting cobalt-chromium alloy castings: sandblasting with a mixed abrasive powder.

STATEMENT OF PROBLEM: Because the conventional divesting method for cobalt-chromium (Co-Cr) alloys is laborious, a more convenient method is desirable. PURPOSE: This study compared sandblasting with a mixed powder composed of aluminum oxide and glass beads to sandblasting with single powders (carborundum, aluminum oxide, and glass beads) when a Co-Cr casting was removed from the investment mold. MATERIAL AND METHODS: Rectangular plates with the 2 surfaces simulating the inner and outer surfaces of a removable partial denture framework were fabricated with Co-Cr alloys. Four kinds of sandblasting powders were used to remove the remnants of investment molds. Total time (seconds) required for each procedure was measured, as was the surface roughness (Ra) of each specimen after sandblasting. SEM was used to analyze the powders themselves and the sandblasted specimen surfaces. RESULTS: Glass beads alone and the mixed powder of aluminum oxide and glass beads generated a smoother surface compared with aluminum oxide and carborundum powders. The use of the mixed powder significantly reduced the time of the sandblasting procedure. SEM revealed that glass beads generated fewer scars, followed by the mixed powder and then aluminum oxide. The surface sandblasted by carborundum powder was always the roughest. CONCLUSION: Sandblasting Co-Cr castings with the mixed powder effectively decreased treatment time and resulted in smooth, clinically acceptable casting surfaces.

Aluminum Oxide↗
PubMed2006

MAS-NMR spectroscopy studies in the setting reaction of glass ionomer cements.

OBJECTIVES: The main objective is the characterisation of the setting reaction in glass ionomer cements based on experimental ionomer glasses with different fluorine content and a commercial glass ionomer cement liquid by using 13C CP/MAS-NMR, 29Si, 27Al and 31P MAS-NMR spectroscopy in order to receive information specifically about the cross-linking process. METHODS: Different fluorine containing glass compositions based on 4.5SiO2-3Al2O3-1.5P2O5-(5-z)CaO-zCaF(2) where z=0-3, were mixed with a commercially available polymer liquid to form glass ionomer cements. The cements were subjected to 27Al, 13C CP/MAS, 29Si, and 31P MAS-NMR analysis. RESULTS: The 27Al spectra showed clearly the formation of six-fold coordinate Al(VI), that may crosslink the carboxyl groups in the poly-acid molecules. A shift towards to more positive values of the carboxyl peak in the 13C CP/MAS-NMR spectra showed clearly the proton dissociation of the carboxyl groups. A shift towards more negative values was observed in the 29Si MAS-NMR spectra, suggesting formation of hydrated silica gel and consequently formation of additional Si-O-Si bonds. 31P MAS-NMR spectra also reflected changes in the coordination state around a PO4(3-) tetrahedron. Increasing the fluorine content of the glasses resulted generally in increased reactivity during setting, due to promoting cross-linking and repolymerisation of the silicate phase, followed by clear changes in the MAS-NMR spectra. CONCLUSIONS: The cross-linking process during the setting reaction of glass ionomer cements can be followed by MAS-NMR spectroscopy observing the conversion of Al(IV) to Al(VI). The acid base setting reaction is completed in 1 day and no further significant changes in the MAS-NMR spectra can be observed. Further study is required in order to understand the role of phosphorus.

Aluminum↗
PubMed2000

Crack initiation modes in bilayered alumina/porcelain disks as a function of core/veneer thickness ratio and supporting substrate stiffness.

We hypothesize that the fracture resistance of alumina core/porcelain veneer disks increases and that crack initiation shifts from veneer to core as the core/veneer thickness ratio (t(C)/t(V)) increases from 0.5/1.0 to 1.3/0.2, or as the elastic modulus of the supporting substrate (E(S)) to which it is resin-bonded increases from 5.1 to 226 GPa. When supported by a low-modulus substrate, disks with low t(C)/t(V) ratios exhibited cracks in the veneer and within the core, while those with high t(C)/t(V) ratios demonstrated core cracks, but not veneer cracks. None of the disks supported by Ni-Cr alloy (E = 226 GPa) exhibited core cracks. These results support the hypothesis that the crack initiation site shifts as the t(C)/t(V) ratio increases, but the increase in E(S) did not affect the crack initiation site. This study suggests that the t(C)/t(V) ratio is the dominant factor that controls the failure initiation site in bilayered ceramic disks.

Aluminum Oxide↗
PubMed2006

Influence of different tests used to measure the bond strength to dentin of two adhesive systems.

PURPOSE: To investigate the behavior of two bonding systems: self-etching primer Clearfil Liner Bond 2V (CLB) and total-etch Single Bond (SB) when submitted to two bond strength tests: shear bond strength (SBS) and microtensile (MTBS). METHODS: Flat dentin surfaces were obtained at the facial surface of extracted bovine incisors. muTBS started with adhesive application and incremental resin composite insertion. Samples were then sliced into 1 mm slabs parallel to the long axis of the tooth. Half of the specimens from each group were trimmed in order to obtain dumbbell-shaped (D) specimens with a cross-sectional area of 1 mm2, and in the other half of the group, the slabs were cut into beams (B) with a cross section of 1 mm2 area. Specimens were individually fractured on a microtensile apparatus. For SBS, crown segments were embedded in polyester resin and a flat dentin surface was exposed for bonding. After adhesive and restorative procedures were accomplished, the specimens were kept in water for 24 hours prior to bond testing. The tests were performed in a universal testing machine. MPa values were analyzed by Tukey's test (P < 0.05), two-way ANOVA (muTBS) and Student's t-test (SBS). RESULTS: Mean values (SD) on muTBS were: SB/B: 42.6 (15.1), SB/D: 35.4 (6.8), CLB/B: 14.3 (10.3) and CLB/D: 27.0 (7.9). SBS values (SD) were: SB: 17.3 (5.6) and CLB 15.9 (7.2). Beam specimens bonded with CLB presented the lowest results. SBS did not show statistical differences between groups. The results showed that the shear bond test seemed to lack the sensitivity that is required to detect subtle differences between bonding agents or procedures.

Animals↗