GB2351086A - Infrared radiation curing of ionomer cements - Google Patents

Abstract

Dental ionomer cements are cured using infrared radiation at wavelengths ranging 0. 1-100 m. This results in dental ionomer cements having accelerated setting speeds, surface hardness and accelerated resistance to water contamination. Further the dental ionomer cements may be polished immediately following the infrared curing. Further disclosed is the use of infrared radiation consecutively or simultaneously with UV radiation for curing dental ionomer cements.

Description

1 2351086 CURING OF CEMENTS APPLICANTS Interdental limited Interdental

House 37 St Peters Street Tiverton Devon EX16 6NW UgWNTORS Ademola. Olaseni Akinmade Christopher Eagleton Wilde Robert Maurice Hooper The device and concept of effecting (e.g. accelerating) the set of acid- base, especially "ionomer" cements, (union of metal oxides and glasses with polymers in the presence of water) to achieve up to a 10-fold improvement in their "instantaneous" surface hardness. Cement formulations curable by this means include all those that contain ionorner (acid-base) components. These are the so-called conventional, resinmodified, resin-based and all other resinous ionomer-containing formulations. The improvements derivable from the IR curing include the possibility of finishing/polishing ionomer cements and the increased resistance to water-solubility immediately following IR curing. These are particularly desirable in dental formulations of conventional, non-resin- based glass-ionomer cements.

1 NOVEL CURING OF IONOMER CEMENTS lonomer cements have found use in dentistry as adhesive restorative materials. Ionomer is the term coined for the reaction between basic glasses or oxides and ionic polymers. Commonly employed ionic polymers include poly(alkenoic acid)s, poly(vinyl phosphonic acid) and copolymers of these two acid types. These cements set automatically once the glass has been mixed with the suitable polymer in the presence of water. The cements formed from glass in this way were later termed Conventional glass-ionomer cements. These cements, introduced into the market in the mid 1970s, usually achieve a state of clinically set over a period of 4 - 6 minutes from the onset of mix. They also have working times of 2 - 4 minutes, during which time the cement can be manipulated, into the dental cavity. The later day version of the glassionomer cements were resin- modified formulations that attained clinical set on "command" from the energy of blue light (400 nin - 50Onm). These cements had the advantages of- i) variable working time to suit dental practitioner and procedure; ii) low water susceptibility due to the presence of the resin and the fast attainment of clinical set.

This invention relates to the use of infrared radiation (IR) as a suitable source of energy for accelerating the set of ionomer cements. In this way, it is similar to the existing blue light. However, unlike the blue light, which causes electronic transitions in the outer valence shells of photoinitiators chemicals, the IR causes the vibrational motion of atoms, molecules and chain segments of the components of the ionomer cements. These include the constituents of the: i) atoms of the glass AI, Ca, Si, etc; and ii) parts of the acidic groups of the polymers and other acids, C =Q 0-11, P=Q etc. In this way, Infrared radiation (0. 1 micron micron) but preferable (3 microns - 15 microns) will energise the parts of the ionomer cements directly involved in the acid/base reaction. This translates to a noticeable increase in the speed of set of the cements. Since these cements progressively become less susceptible to water contamination as they set, the IR curing of ionomer cements also reduces the vulnerability of freshly mixed cements to water attack. The IR cured cements also take-up polish more readily due to their accelerated development of hardness. Therefore, IR is a means of replicating the advantages of the existing light curing of ionomer cements. It also has the added advantage of also being applicable to non- resin-based formulations.

The IR curing of ionomer cements can be demonstrated for all formulations containing the ionomer constituents. These include the reaction products of glasses, oxides and other precursors of the constituent metal atoms of ionomer cements - Ca, Si, 0, F, Zn, N1g, AI, and other suitable tri- and divalent atoms in cement formulations. Examples of the other component of the formulations are: i) alkenoic acid(s); ii) phosphonic acid(s); iii) sulphonic acid(s); iv) any combinations in the form of physical blends and copolymers of the preceding acids. Also included are ionomer cements in resin-modified, resin incorporated and formulations containing polymerisable "half ester- half acid" chemicals and photoinitiators.

0 The invention claims right on the concept of using IR, particularly of the range (3-15 microns) to accelerate the set of acid-base cements. We also include the use of IR radiation in both resinous, resin included and resin-modified formulations as well as the Conventional acid-base cements. Finally, the use of IR, either as the only source of external activation of ionomers or consecutively or simultaneously with any other energy source, e.g. blue light is covered by our invention. The invention will now be described by way of examples of experimental data.

2 The state and speed of the acid-base reaction of ionomer cements can be followed by measuring the pH of the setting cement pastes. The pH of ionomer cements starts from about 1.5 and then rises rapidly at first and then more slowly, as cements set. The viscosity and the hardness of the cements also follow this trend. At the same time, the resistance to water dissolution increases. Therefore, pH is a measure of the efficacy of the IR curing, while improved surface hardness, early take-up of polish and resistance to water dissolution are the measurable deliverables and criteria for confirming the usefulness of the IR curing of ionomer cements.

A number of components necessary to build an infrared pulsing device were purchased from L.O.T Oriel Instruments, Stratford, Connecticut, USA. The two important components of the device were the illuminator and the IR element. The illuminator consisted of. 1. A built-in power supply with the current regulated output specifically designed for the IR element 2. A soft-start regime when the power is applied to avoid "socking" the IR element 3. A precision 10-turn output current control and digital display of the current and voltage The IR element used was a high temperature, oxidation resistance wire. The coil was supported on a grooved alumina support mandrel. The radiating area was 0. 14 inches (3.6 mm) wide and 0. 14 inches (3.6 mm) long.

pH Measurements With a current setting of 1.80 amps and 4.5 V, the effect of distance of IR element from the surface of the cements being cured was investigated using pH measurements. In these experiments cement comprising powder [100 parts glass, 10 parts poly(acrylic acid) and 3 parts tartaric acid] and liquid [25 parts poly(acrylic acid), 12.5 parts tartaric acid and 62.5 parts water] were mixed at 4:1 ratio. The cements (termed KG23/5) were mixed and the experiment conducted at room temperature (19C). Cements were mixed and placed in a thin layer at the tip of a Flat head Combination BDH pH electrode connected to an lonmeter. In this experiments, the cements at the end of the electrode were placed at requisite distance from the IR element and irradiation commenced at t = 90s from the onset of mix. The results of these experiments are presented in Table 1. From the Table, the efficacy of the IR curing can be observed. IR curing (for all the cements from I cm to 8 cm distance from the IR element) increased the rate of rise in the pH of the cements. Not surprisingly, the closer the cement was to the IR element, the more efficient the IR curing was.

Following these experiments, the effect of IR curing on the pH of various commercial dental ionomer cements was determined. These cements included Fuji IX and Fuji 11 LC [Ex. GC Corp, Japan] and Diamond Carve [Ex. Kemdent, LTK]. Fuji IX is a polycarboxylate-based Conventional cement. Diamond Carve is a polyphosphonate-based Conventional cement, while Fuji II LC is a resin-modified glass-ionomer cement, with carboxylic acid ionomer content. The pHs of these cements, IR cured and otherwise, were determined using a regime of 1.8 amps (4.5V). Cements were cured from a distance of 4 cm from the cement surface and from t = 90s from the onset of mix. The Fuji II LC was light cured for 40s. Table 2 presents the results of these experiments. In Table 2, "F IV is Fuji IX, "F LC" is Fuji II LC and "DC" is Diamond Carve. As can be observed from Table 2, IR curing was effective in increasing the speed of pH increase in all the setting pastes of the cements evaluated. These results suggest that IR curing is effective in all the classes of the commercial ionomer cements (glass polyalkenoates and glass polyphosphonates) and in resin-modified ionomer cements.

1 j (4- Solubitity Measurements The solubility of the experimental cement (KG23/5) was determined as a function of distance from the IR element. These experiments were carried out at ambient temperature (I 9C) and using an IR curing regime of 1.8A (4.5V) and curing time of 60s (90-150s from the onset of mix). The solubility measurements were made with the aid of a JENWAY Total Dissolved Solids (TDS) meter (model 4076). 1 gram of cement was mixed and placed in stainless steel rings of 13-mm diameter by 2-mm height. These cement discs were then subjected to IR curing and placed at the bottom of glass vials containing 10.00 g of distilled water at time t 3.00 0.20 minutes from the onset of mix. The TDS of the distilled water had been predetermined as 4.3 mg/l. This value has been subtracted from the readings of the cement containing aqueous solutions in the readings presented in Table 3. The TDS of the solutions increase as solids dissolve from the cement into the water. Therefore, the improvement in the resistance to water dissolution of the ionomer experimental cement is obvious from the low TDS values of cements upon IR curing. As indicated from the pH measurements of Table 1, the efficiency of the IR irradiation decreases with distance away from the IR element.

The solubilities of commercial dental cements were also determined in the manner described. The effect of IR curing on the solubilities of Fuji IX, Fuji 11 LC, KG23/5 and Diamond Carve is presented in Table 4. The solubilities of all the cements evaluated reduced with IR irradiation. Noteworthy is the fact that the solubility of Fuji 11 LC was significantly improved by the IR curing. In the experiments, Fuji II LC was light cured on one side and its solubility evaluated. In the IR experiment, Fuji II LC was first light cured for 40s and then IR cured for 60s. The reduction in the susceptibility to water of Fuji 11 LC at the point of introduction (t= 3.00 minutes) is due to the fact that the acid-base reaction of the cement has been deliberately retarded to accommodate the light curing reaction. From the results of the experiment, it appears desirable to IR cure light cure, resin-modified ionomer cements after the initial light curing.

Mechanism of ER curing - Temperature Effect In an attempt to judge the efficacy and to explore the mechanism of the IR curing of the ionomer cements, a series of experiments were undertaken. These included: i) evaluating the temperature increase of 1.00g of cement upon light curing; and ii) evaluating the hardness of cements isothermally, achieved via Ig curing and also by placing cements in pre-heated ovens.

The temperature rise of 1.00g of cements measured at the IR cured surface with the aid of a ktype thermocouple connected to a Digitron Instrument ltd thermometer were determined as function of distance of the cements from the IR element. IR curing commenced at t = 90s. The IR curing regime employed was 1.80 amps (4.5 V). The results of these experiments are contained in Table 5. From this Table, the increase in temperature with IR curing time and distance towards the IR element is clear. Although the temperature rose towards I OOC, after 60s of IR curing, i.e. at t = 150s, the temperature attained was less than 60 'C in all cases. The maximum temperature indicated for the curing of dental ionomer cements will be 40 - 60 s. This is in line with the current practice of 40 s blue light curing of resin-modified glassionomer cements. In order to judge the effect that this temperature rise had on the efficacy of the IR curing, Diamond Carve cements were mixed and flattened between two glass slides in the stainless steel rings. Cement samples were stored at 60'C to simulate the effect of IR irradiating the cement for 60 s from a distance of I cm from the cement surface. Cement samples were also subjected to this IR regime and stored at 37C. Finally, cements were mixed and stored without IR curing at 3 7'C. All cements were exposed to 100 % rh environment at t = 5 minutes. The scratch hardness measured by a Leitz Vickers indenter was determined. From these measurements, made at t = 15, 30, 60, 180 and 300 minutes, the hardness of the cements were evaluated. The results of these experiments are presented in Table 6 and Figure 1.

4 The 15 and 30-minute hardness values of the IR cured cements are significantly superior to those of the non-IR-cured variants. This proves the efficacy of IR curing of ionomer cements. The fact that the hardness of all the cements, IR cured and otherwise, were eventually similar (after 3 hours) indicates that the IR curing is basically a "rate of reaction acceleration" phenomenon. Indeed, it is a surface phenomenon that has negligible effect on the bulk mechanical properties of ionomer cements. This is confirmed by the results presented in Table 7, giving details of the surface hardness and compressive strength of the experimental KG2315 cement.

Surface Hardness Measurements The efficacy of the IR curing of ionomer cements as a means of creating "command" cured dental cements can be clearly observed from Table 8 and Figure 2. The profiles for the surface hardness of Conventional and the current light cured resin-modified cements are typified by those of KG23/5 and Fuji II LC respectively in Table 8. While conventional glassionomer cements develop hardness sluggishly in a logarithmic fashion, light cure cements exhibit a linear trend, with a much higher "instantaneous" hardness than the Conventional cement variants. Also, in addition, the 15 minute value of the light cured cements is - 50 % the 24 hour (or final) hardness value. This is in contrast to the case with the Conventional cements with a scratch hardness value of 15 minutes/24 hours (0.0 1 value) of - 10 %. This is a main reason why conventional glass- ionomer cements do not take-up polish until they are mature, well over 24 hours old. The efficacy of the IR curing can therefore be measured by the attainment of the 50% "0.01 " scratch hardness value. (Fuji II LC has a value of 53%).

Clearly, the IR regime employed on the KG23/5 cements (1.8 Amps and 60s from 1 cm from the cement surface) met this objective, with a value of 82 %. The effect of IR regime on the scratch hardness and the "0.0 1 " value for the KG23/5 cement is presented in Table 9, 10 and Figure 3. From Table 10, the IR regimes that create command cure cements comparable to those currently existing are: 1 cm distance from IR element and 20-60 s IR curing 2 cm from the IR element and 40-60 s IR curing 3 cm from the IR element and 6-0 s IR curing Finally, in a series of experiments, the efficacy of the IR curing of ionomer cements and the estimation of the IR affected area of cements were determined. This was achieved by placing the IR element underneath holes drilled at judicious distances apart into a 3-mm thick aluminium plate. Directly on top of these holes in a series of experiments, were placed cement discs resting on wooden rods. These cements were then irradiated with IR for 60s and with the IR element a distance of 1 cm or 2 cm away from the cement surface. In this way, the 3 D map of the surface hardness of the cements placed over 1, 2, 4 and 6-mm diameter holes were determined. The 31) surface hardness map of cements IR cured for 60s, 1 cm away from the IR element and over the 4-cm hole is presented in Figure 4. The "mountain" topography was obtained by the careful mapping of the co-ordinates from which the scratch hardness values were obtained. In Figure 4, the scratch on the cement was created between 5 and 10 minutes from the onset of mixing the cement. The value on the x-axis is distance in mm. This shows that an area the shape of an ellipse of dimensions 7 mm by 5 mm had attained the maximum hardness of 450 MPa 500 MPa.

(0 TABLE 1. THE EFFECT OF DISTANCE FROM THE IR ELEMENT ON THE pHs OF KG2315 CEMENTS Cement age (s) No IR 1 cm IR 2 cm IR 3 cm IR 4 cm IR 5 cm IR 6 cm IR 7 cm IR 8 cm IR 1.32 1.05 1.11 1.24 1.08 1.04 0.93 1.21 1.19 1.36 1.07 1.14 1.26 1.09 1.02 0.94 1.23 1.19 1.38 1.12 1.21 1.3 1.11 1.06 0.97 1.25 1.21 1.41 1.2 1.29 1.35 1.15 1.1 1 1.27 1.24 1.43 1.3 1.38 1.41 1.19 1.14 1.04 1.29 1.27 1.45 1.43 1.47 1.48 1.25 1.19 1.09 1.31 1.3 1.47 1.49 1.54 1.55 1.32 1.25 1.13 1.35 1.34 1.5 1.56 1.6 1.6 1.39 1.31 1.19 1.38 1.39 1.52 1.63 1.65 1.65 1.45 1.36 1.23 1.44 1.43 1.54 1.69 1.7 1.71 1.5 1.41 1.29 1.47 1.47 1.56 1.75 1.75 1.75 1.55 1.46 1.34 1.52 1.52 210 1.58 1.81 1.79 1.79 1.6 1.51 1.38 1.56 1.57 220 1.6 1.86 1.84 1.84 1.65 1.54 1.42 1.59 1.6 230 1.62 1.92 1.88 1.87 1.69 1.58 1.46 1.64 1.63 240 1.64 1.97 1.92 1.9 1.73 1.61 1.5 1.67 1.66 250 1.66 2.03 1.96 1.93 1.77 1.66 1.53 1.7 1.7 260 1.67 2.08 1.99 1.96 1.82 1.69 1.55 1.72 1.72 270 1.69 2.13 2.03 1.99 1.84 1.72 1.59 1.75 1.75 280 1.71 2.17 2.07 2.02 1.87 1,75 1.62 1.78 1.78 290 1.73 2.22 2.1 2.05 1.9 1.78 1.64 1.8 1.8 300 1.74 2.26 2.14 2.08 1.94 1.81 1.67 1.83 1.82 310 1.76 2.31 2.18 2.1 1,97 1.84 1.7 1.85 1.84 320 1.77 2.35 2.22 2.14 2 1.87 1.72 1.87 1.87 330 1.79 2.39 2.25 2.16 2.03 1.9 1.75 1.89 1.89 340 1.8 2.42 2.29 2.19 2.06 1.92 1.78 1.91 1.91 350 1.82 2.45 2.32 2.22 2.09 1.95 1.8 1.93 1.92 360 1.83 2.48 2.35 2.24 2.12 1.98 1.83 1.96 1.95 370 1.84 2.51 2.38 2.27 2.15 2 1.85 1.97 1.97 380 1.86 2.54 2.41 2.29 2.17 2.02 1.87 1.99 1.98 390 1.87 2.57 2.43 2.32 2.2 2.05 1.9 2.01 2 400 1.89 2.6 2.46 2.34 2.23 2.07 1.92 2.03 2.02 410 1.9 2.63 2.49 2.37 2.26 2.1 1.95 2.05 2.04 420 1.9 2.65 2.51 2.4 2.28 2.12 1.97 2.07 2.06 430 1.92 2.68 2.54 2.42 2.3 2.15 1.99 2.09 2.07 440 1.92 2.71 2.56 2.44 2.33 2.17 2.01 2.11 2.09 450 1.93 2.73 2.58 2.46 2.35 2.21 2.04 2.13 2.11 460 1.95 2.76 2.61 2.48 2.38 2.23 2.07 2.15 2.13 470 1.95 2.79 2.63 2.51 2.4 2.25 2.09 2.16 2.15 480 1.96 2.84 2.65 2.53 2.42 2.27 2.12 2.18 2.16 490 1.97 2.86 2.67 2.55 2.44 2.29 2.14 2.2 2.18 500 1.98 2.88 2.68 2.57 2.46 2.31 2.17 2.21 2.19 510 1.99 2.9 2.7 2.58 2.48 2.34 2.21 2.23 2.2 520 1.99 2.92 2.71 2.6 2.5 2.35 2.24 2.25 2.23 530 2 2.93 2.73 2.63 2.52 2.38 2.26 2.26 2.25 540 2.01 2.94 2.74 2.64 2.54 2.39 2.29 2.28 2.26 550 2.02 2.96 2.76 2.66 2.56 2.4 2.32 2.3 2.27 560 2.02 2.97 2.78 2.68 2.58 2.43 2.35 2.31 2.29 570 2.03 2.98 2.8 2.69 2.59 2.45 2.37 2.33 2,31 580 2.04 2.99 2.82 2.71 2.61 2.47 2.4 2.35 2.31 590 2.04 3 2.83 2.73 2.63 2.49 2.42 2.36 2.33 600 2.05 3.01 2.85 2.75 2.64 2.5 2.44 2.37 2.34 6 TABLE 2. THE EFFECT OF IR CURING ON THE pHs OF GLASS-IONOMER CEMENTS Cementage(s)l FIX IFIX-IRI FLC IFLC-IRIFLC-LCIIRI DC 15C-IR 1.4 1.18 1.91 1.96 1.78 1.7 1.6 1.42 1.18 1.93 1.95 1.82 1.73 1.62 1.44 1.23 1.95 1.98 1.89 1.75 1.67 1.47 1.28 1.96 2.03 1.95 1.78 1.74 1.49 1.35 1.98 2.11 2.01 1.81 1.81 1.52 1.44 2 2.2 2.05 1.84 1.9 1.55 1.53 2.03 2.29 2.09 1.86 1.98 1.59 1.63 2.05 2.34 2.12 1.89 2.02 1.62 1.71 2.08 2.4 2.15 1.92 2.07 1.65 1.8 2.1 2.43 2.16 1.94 2.12 1.68 1.89 2.13 2.47 2.18 1.97 2.17 210 1.71 1.96 2.16 2.52 2.2 2 2.2 220 1.74 2.03 2.19 2.56 2.22 2.02 2.25 230 1.78 2.1 2.22 2.6 2.23 2.04 2.3 240 1.81 2.17 2.25 2.63 2.25 2.06 2.34 250 1.84 2.24 2.28 2.65 2.26 2.08 2.38 260 1.87 2.3 2.31 2.67 2.27 2.1 2.42 270 1.9 2.37 2.33 2.68 2.28 2.13 2.45 280 1.92 2.42 2.36 2.7 2.29 2.14 2.49 290 1.95 2.48 2.38 2.73 2.31 2.15 2.52 300 1.98 2.54 2.4 2.74 2.32 2.17 2.55 310 2.01 2.6 2.42 2.75 2.32 2.18 2.59 320 2.03 2.67 2.44 2.75 2.33 2.2 2.62 330 2.06 2.77 2.46 2.77 2.34 2.21 2.65 340 2.08 2.85 2.47 2.79 2.36 2.22 2.67 350 2.1 2.91 2.49 2.8 2.37 2.23 2.7 360 2.13 2.97 2.5 2.81 2.37 2.24 2.73 370 2.15 3.01 2.51 2.82 2.38 2.26 2.75 380 2.17 3.07 2.53 2.83 2.39 2.27 2.77 390 2.2 3.12 2.54 2.84 2.4 2.28 2.79 400 2.22 3.17 2.55 2.85 2.42 2.29 2.82 410 2.24 3.21 2.56 2.86 2.41 2.3 2.83 420 2.26 3.24 2.57 2.87 2.43 2.31 2.86 430 2.28 3.27 2.58 2.88 2.44 2.31 2.88 440 2.3 3.31 2.59 2.89 2.46 2.32 2.9 450 2.32 3.33 2.6 2.9 2.48 2.33 2.92 460 2.34 3.36 2.61 2.91 2.49 2.34 2.94 470 2.36 3.38 2.62 2.91 2.52 2.35 2.95 480 2.38 3.4 2.62 2.92 2.54 2.36 2.96 490 2.4 3.42 2.63 2.94 2.58 2.37 2.96 500 2.42 3.44 2.64 2.95 2.59 2.38 2.97 510 2.44 3.46 2.64 2.98 2.59 2.38 3 520 2.46 3.48 2.65 3.01 2.61 2.39 3.01 530 2.48 3.49 2.66 3.03 2.61 2.4 3.03 540 2.5 3.5 2.66 3.05 2.65 2.41 3.03 550 2.51 3.51 2.67 3.09 2.67 2.42 3.05 560 2.53 3.52 2.68 3.12 2.68 2.42 3.05 570 2.55 3.54 2.68 3.14 2.71 2.43 3.06 580 2.57 3.55 2.69 3.15 2.73 2.44 3.09 590 2.58 3.56 2.69 3.16 2.74 2.45 3.1 600 2.6 3.57 2.7 3.17 2.74 2.46 3.1 7 TABLE 3. THE EFFECT OF DISTANCE ON THE SOLUBILITY OF KG23/5 CEMENTS Cement age (s) 1.0 cm 2.0 cm 3.0 cm 4.0 cm 5.0 cm N;--IR 3.6 12.3 13.4 15.4 70.4 220 2.2 3.8 12.4 14.3 15.8 70.8 240 2.4 4 12.5 15.1 16 69.8 260 2.5 4.1 12.9 15.6 16.1 69.4 280 2.6 4.3 13.4 15.9 16.3 69.5 300 2.7 4.5 13.8 16.1 16.5 95.1 320 2.7 4.6 14.1 16.3 16.8 117 340 2.9 4.7 14.3 16.4 16.9 128.5 360 3.1 4.7 14.4 16.5 17 142.8 380 3.3 4.8 14.4 16.6 17.1 150.1 400 3.4 4.9 14.4 16.6 17.3 151.3 420 3.5 4.9 14.4 16.5 17.3 153.8 440 3.6 4.9 14.4 16.5 17.4 155.8 460 3.6 5 14.4 16.4 17.5 157.4 480 3.6 5 14.4 16.3 17.6 158 500 3.6 5 14.5 16.2 17.7 159.8 520 3.6 5.1 14.5 16 17.8 161 540 3.6 5.1 14.5 16 17.9 162 560 3.5 5.1 14.6 15.9 18 165.7 580 3.5 5.2 14.6 15.8 18.1 169 600 3.5 5.2 14.6 15.7 18.2 171 660 3.4 5.2 14.6 15.6 18.5 174 720 3.4 5.2 14.7 15.6 18.7 177.5 780 3.4 5.3 14.7 15.5 19 180 840 3.4 5.3 14.7 15.4 19.1 182.5 900 3.4 5.3 14.6 15.4 19.3 184.6 960 3.4 5.3 14.6 15.3 19.5 186.7 1020 3.4 5.3 14.8 15.2 19.5 190.7 1080 3.4 5.3 14.8 15.2 19.6 194 1140 3.4 5.3 14.8 15.1 19.7 197.5 1200 3.4 5.3 14.8 15.1 20.1 212 1260 3.4 5.4 14.8 15 20.1 224 1320 3.4 5.4 14.8 15 20.1 227 1380 3.4 5.4 14.8 14.9 20.2 230 1440 3.4 5.4 14.5 14.9 20.2 232 1500 3.4 5.4 14.7 15 20.3 235 1560 3.4 5.4 14.8 15 20.3 237 1620 3.5 5.4 14.9 14.9 20.3 239 1680 3.5 5.4 14.6 14.8 20.3 241 1740 3.5 5.4 14.5 14.8 20.4 242 1800 3.5 5.4 14.5 14.8 20.4 244 8 TABLE 4. THE EFFECT OF IR CURING ON THE SOLUBILITY OF GLASS-IONOMER CEMENTS SOLUBILITY (mg1l) Cement Fuji 11 LC Fuji IX-IR DC-IR KG23/5-IR Fuji 11 LC Fuji IX KG2315 DC Age (s) (40s LC+IR) (40s LC) 240 9.2 5.5 6.4 11.7 62 56 69.8 24.4 260 9.5 5.6 6.9 11.2 63.7 61 69.4 24.7 280 9.6 6 7.31 11.7 65 65 69.5 24.9 300 9.7 8 8 12.7 66 67.5 95.1 25.1 320 9.9 8.1 8.5 13.4 66.1 69.5 117 25.3 340 9.9 8.3 8.8 14.3 66.1 70.9 128.5 25.4 360 10.1 8.5 8.9 15.1 65.8 71.9 142.8 26 380 10.2 8.6 9 15.6 65.5 72.8 150.1 26.2 400 10.3 8.8 9 15.9 65 73.5 151.3 26 420 10,3 8.9 9.1 16.1 64.6 74.2 153.8 26.1 440 10.3 9.1 9.1 16.3 64.2 74.7 155.8 26.1 460 10.3 9.3 9.1 16.4 63.8 75.2 157.4 26.1 480 10.3 9.5 9.2 16.5 63.5 75.6 158 26.4 500 10.3 9.6 9.2 16.6 63.1 76.1 159.8 26.5 520 10.3 9.8 9.2 16.6 62.8 76.4 161 26.6 540 10.2 9.8 9.2 16.5 62.5 76.8 162 26.8 560 10.2 9.9 9.2 16.5 62.2 77.2 165.7 27 580 10.2 10 9.2 16.4 61.9 77.5 169 27.3 600 10.2 10.1 9.2 16.3 61.6 77.8 171 27.5 660 10.3 10.4 9.1 16.2 60.8 78.9 174 28.3 720 10.3 10.6 9.1 16 60.1 80.1 177.5 28.8 780 10.3 10.7 9 16 59.6 81.2 180 29.3 840 10.3 10.9 9 15.9 59.2 82 182.5 29.5 900 10.3 11 8.9 15.8 58.8 82.7 184.6 29.8 960 10.3 11 8.9 15.7 58.6 83.4 186.7 30 1020 10.3 11.3 8.8 15.6 58.2 84 190.7 30.2 1080 10.3 11.4 8.8 15.6 57.9 84.6 194 30.4 1140 10.3 11.5 8.8 15.5 57.7 85.3 197.5 30.6 1200 10.3 11.6 8.8 15.4 57.5 85.8 212 30.8 1260 10.3 11.7 8.8 15.4 57.3 86.3 224 30.9 1320 10.3 11.8 8.8 15.3 57.1 86.8 227 31.1 1380 10.3 11.9 8.8 15.2 57 87.7 230 31.3 1440 10.3 12 8.8 15.2 56.9 87.7 232 31.5 1500 10.3 12 8.8 15.1 56.8 88.3 235 31.6 1560 10.3 12.1 8.8 15.1 56.7 88.7 237 31.8 1620 10.3 12.1 8.8 15 56.7 89.1 239 31.9 1680 10.3 12.2 8.8 15 56.5 89.5 241 32.1 1740 10.3 12.2 8.7 14.9 56.5 89.9 242 32.2 1800 10.3 12.3 8.7 14.9 56.5 90.3 244 32.3 Cements introduced into 1 Og of water at t= 1 70s, only one surface of the disc is exposed to water. The results have the 12.7 mg/I tds of water 9 TABLE 5. THE TEMPERATURE OF KG2315 CEMENTS DURING]R PULSING (Cement, pulsed with IR at 1.8 Amps, starting from t= 90s, with the probe at the surface of the cement) Cement age (s) 1 11cm 1 2cm 3cm 4cm 5CM1 6CM 1 7im- 1 8CM 32 38.5 36.8 38.2 36.4 39.7 35.6 34.9 39.6 44 42.2 43.3 41.4 44.5 38.5 38.7 48.6 50 47.7 48.4 47 49.6 42.3 41.9 57.7 56.1 53.2 54 52.6 54.9 45.5 44.9 66.7 62.5 59 59.7 58.7 60.5 48.5 47.9 79.7 69.2 64.7 65.1 64.1 66.3 52.1 50.9 88.2 74.7 70.1 70.9 69.8 71.5 54.9 53.3 94.9 78.9 74.8 76. 74.7 76.5 57.9 56.2 103.8 81.7 78.2 80.1 78.4 80.1 60.9 58.9 210 108.1 83.8 80.9 82.9 81.7 82.7 63 61.5 220 110.2 85.1 82.9 85.9 84.1 84.4 64.9 63.6 230 111.6 86 84.2 87 85.7 85.7 66.7 65.7 240 112.7 86.5 85.2 88.3 86.9 86.9 68 67.2 250 113.4 86.5 85.7 89.6 87.9 87.6 69.2 68.5 260 113.8 86.6 86.2 91 88.6 88.1 70.2 69.3 270 113.7 86.8 86.6 92 88.9 88.7 70.6 70.1 280 112.4 86.7 86.7 92.1 89.1 89 70.7 70.6 290 109.4 86.7 86.8 92.3 89.4 89.4 70.7 71 300 108 86.7 87 92.3 89.3 89.6 71 71 310 107.2 86.3 87.1 91.9 89.5 89.7 71.2 71.1 320 106.5 86.2 87.2 92.3 89.4 89.9 71.4 71.1 330 105.9 85.8 87.2 92 89.5 90 71.4 70.9 340 105.4 85.7 87.3 91.4 89.3 89.7 71.3 70.8 350 104.4 85.6 87.5 90.9 89 89.6 71.3 70.7 360 104.4 85.3 87.6 90.6 89 89.6 71.1 70.4 370 103.6 85.3 87.6 90.5 88.9 89.5 70.9 70.1 380 103.4 85.2 87.6 89.6 88.7 89.5 70.8 70 390 103.2 85.2 87.8 89.2 88.5 89.6 70.5 69.6 400 103 85.1 88 89.1 88.6 89.7 70.3 69.6 410 102.9 85 88 89 88.5 89.7 70.2 69.1 420 102.8 84.6 87.7 88.5 88.4 89.8 69.9 69 430 102.7 84.4 87.7 88 88.2 89.7 69.8 68.6 440 102.8 84.4 87.9 87.8 88.3 89.8 69.8 68.3 450 102.8 84.4 87.8 87.7 88.3 89.9 69.8 68.2 460 102.8 84.2 87.7 88 88.2 90 69.8 67.8 470 102.9 84.2 87.6 87.8 88.4 89.9 69.7 67.8 480 102.9 84 87.5 87.8 88.3 89.9 69.5 67.7 490 102.9 83.7 87.6 87.7 88.3 89.6 69.4 67.5 500 102.9 83.8 87.7 87.6 88.1 89.2 69.1 67.4 510 103 84 87.7 87.7 88.1 89.1 68.9 66.9 520 103.1 84 87.6 87.5 88.2 89.1 69 66.4 530 103.2 84 87.6 87.2 88.3 89 68.9 66.3 540 103.3 84 87.6 87.1 88.3 88.8 68.8 66.3 550 103.4 84 87.6 87 88.6 88.7 69 65.9 560 103.5 83.9 87.5 87.3 88.5 88.7 68.9 65.9 570 103.7 83.9 87.5 87.5 88.4 88.5 69 65.6 580 103.8 83.8 87.4 87.4 88,3 88.4 69.1 65.6 590 104 84 87.3 87.5 88.2 88.7 69.1 65.2 600 104.2 84 87.3 87.5 88.2 88.7 69 65.1 TABLE 6. THE EFFICACY OF IR CURING OF KG2315 CEMENT Cement Age (mins) DC-37 (Wet)T7DC-60 (Wet) 1 DC-1 R (57 Wet) 695.8 773.1 1229.1 669.6 957.7 1130.5 893.5 1165.7 1207.1 1181.3 1379.8 1090.4 300 1019 1234.5 1150.7 FIGURE1. THE EFFECT OF IRCURING ON THE HARDNESS OF DIAMOND CARVE CEMENT 1800--- 1600- 1400- .............

too - cc i DC-37 (Wet) 800 - T W DC-60 (Wet) --4b-DC-IR (37 Wet) 600 400 i 0 50 100 q MENT AGE (Tbffi) 250 300 350 TABLE 7. THE MECHANICAL PROPERTIES OF KG2315 CEMENTS WITH IR CURING Cement age (mins) Utrength -]R Hardness IR 1 Strength - No IR 1 Hardness - No]R 0.25 44.44 0.0 10.8 337.9 0.5 34.69 0.0 31.94 641.8 1 62.32 0.0 64.05 924.5 3 99.06 0.0 94.03 1274.1 98.34 0.0 100.1 1351.6 24 115.2 1325.4 112.8 1339.5 TABLE 8. THE IR CURING OF GLASS-IONOMER CEMENTS CEMENT AGE (mins) Fuji 11 LC KG23/5 KG23/5 - IR Fuji 11 LC - IR 568.8 72.87 1010 1030 574.2 551 902 1050 659.9 730 852 1050 844.5 597 1120 1060 300 956 906 1120 1080 1440 1076.2 875 1230 1230 FIGURE 2. THE IR CURING OF GLASS-IONOMER CEMENTS 1200 1 y = 0.1391 x + 1037.7;z 0.8596 Sitx + 5%.22 l! R 1=00 1 9797 -2C0)771,81Ln(x) - 305.61 1 800 - 2 R' = 0.6835 i m z U) 0 Lu z 600 U) 400 Fuji 11 LC 0 KG236 - No]R i KG215 -]R 200- X Fuji 11 LC - IR 0, 0 50 100 150 200 250 300 350 CEMENT AGE (mins) 12 is TABLE 9. THE 15-MANUTE HARDNESS VALUES OF KG2315 CEMENT Curing time (s)l SCRATCH HARDNESS (MPa) Distance (cm) 20s 40s 60s No IR 72 1 684 956 1684 2 496 688 804 3 448 568 700 4 408 488 524 488 488 520 8 280 301 269 FIGURE 3. THE 15 MINUTE HARDNESS VALUES OF IR-CURED KG2315 CEMENT 1800 1600 =800 W h 400 0 1 2 3 DISTANCE FROM IRSOURCE 6 7 8 9 TABLE10. THE CURING EFFICACY OF VARIOUS ER REGIMES Cement Distance Hardness (0.01 value) % from]R (cm) 60s 40s 20s 1 136.9 77:7 55.6 2 65.4 55.9 40.3 3 56.9 46.2 36.4 4 42.6 39.7 33.2 42.3 39.7 39.7 1 8 21.9 24.5 22.8 13 1 6B4 894700 1 (+ FIGURE 4. THE SURFACE HARDNESS PROFILE OF DC CEMENT CURED FOR 60s 1cm FROM THE IR ELEMENT 500 450 400 3 SCRATCH HARDNESS 2 0 (MPa) 200 S5 100 - 33 E4 1.,F - D3 0 1 1 1 1 1 1 1 1 1 1 1 T l 1 1 1 't I' S1 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2W-1W M 200-250 92150.200 12 100-150 M50-100 120-50 14

Claims (7)

1. The curing of acid-base cements, especially dental "ionomer" cements by infrared radiation (0. 1 microns - 100 microns), but preferable 3 microns - 15 microns as a means of affecting, e.g. accelerating, their speed of set.

2. The curing of acid-base cements, especially dental "ionomer" cements by infrared radiation (0. 1 microns - 100 microns), but preferable 3 microns - 15 microns as a means of accelerating their development of surface hardness.

3. The curing of acid-base cements, especially 9onomer" cements by infrared radiation (0. 1 microns - 100 microns), but preferable 3 microns - 15 microns as a means of accelerating their resistance to watercontamination.

4. The above (1)-(3) improvements will produce "conventional" glassionomer cements capable of being polished immediately following IR curing. This is similar to the existing command curing of resin-modified ionomer cements by blue light

5. The IR curing of resin-based ionomer cements delivers the improvements (1)-(3), i.e. increase in speed of set, surface hardness and resistance to water solubility. These cements are already polishable following curing - (claim 4). The IR curing of non-resin ionomer cements delivers the properties (1)-(4)

6. The use of IR radiation as the sole source of external energy for the curing of ionomer cements, or the use of this radiation consecutively or simultaneously with any other energy source, e.g. blue light for all forms of compositions containing the "ionomer" reactions. At the present time, these include "conventionaP acid-base glass-ionomer cements, resin- modified glass-ionomer cements, polyacid-modified composites (compomers) and all other blends or combinations of resins and ionomer components.

7. The device(s) capable of producing infrared radiation of the type indicated in Claim (1) and typified by our experimental IR unit or any modifications or versions intended or capable of curing ionomer cements by means including IR radiation. These include devices capable of producing IR radiation only or IR and other energy radiation, e.g. blue light simultaneously or consecutively.

is