Oral electrochemical action after soft drink rinsing and consumption of sweets

The aim of this study was to investigate the influence of pH changes in dental plaque and saliva on the magnitude of the galvanic current created when amalgam restorations make contact in the oral cavity. Ten persons with 46 contacts between amalgam fillings in all participated in the experiments. Potential, polarization, and pH measurements were performed before and after Coca-Cola and orange juice rinsing and intake of sweets, which were used as test products. Distilled water was used as a control. The measurements were performed 2, 5, 10, 20, and 30 min after the rinsing or intake. There was no statistically significant difference in the current magnitude after any test product or between the time intervals after the different products. The results indicated that changes of the plaque and saliva pH for a short time after food and soft drink intake do not influence the magnitude of the galvanic current flowing between amalgam restorations in contact.     

Effect of a buffering sugar-free lozenge on intraoral pH and electrochemical action.

Two double-blind crossover studies were performed to test a sugar-free lozenge containing bicarbonate and phosphate buffers (Profylin). The studies were performed in groups of 20 and 13 individuals. In Study I active buffering or placebo lozenge (not buffered) was given, and the pH of plaque and saliva was measured after 2, 5, 10, 20, and 30 min. In study II the lozenges were given 10 min after a sucrose rinse, and both the pH and the potential and polarization of amalgam restorations that made contact in the oral cavity were measured. In study I both lozenges increased the pH of plaque and saliva, but the values after sucking on the active lozenge were significantly higher than after placebo. In study II a pH recovery of plaque and saliva after the sucrose rinse was recorded for both types of lozenge, but it was most pronounced for the active, buffering lozenge. A statistically significant difference was, however, found only 5 min after sucking on the lozenge. No influence on the current magnitude was observed. The results thus indicate that the buffering sugar-free lozenge raises the pH of plaque and saliva and accelerates the pH recovery after a sucrose rinse but seems to have no influence on the galvanic current magnitude of amalgam restorations in contact.     

Galvanic interaction between gold and amalgam: effect of zinc, time and surface treatments

BACKGROUND: Previous studies have investigated the electrolytic action of oral electrogalvanism. However, the reasons why certain treatments or materials are successful in reducing galvanic current have not been addressed fully. This study assessed galvanic current with several materials, surface conditions and treatments. METHODS: The authors measured galvanic currents between a type 3 cast gold alloy and Dispersalloy Dispersed Phase Alloy (zinc) (Dentsply Caulk, Milford, Del.) under different surface conditions using a zero-resistance-ammeter technique in a synthetic saliva solution for 10 hours. In addition, the galvanic currents between the same gold and Tytin alloy (non-zinc) (Kerr, Orange, Calif.), experimental zinc alloy (same makeup as that of Tytin, with the addition of zinc) and non-zinc dispersed-phase experimental alloy (essentially the same physical and chemical makeup as that of Dispersalloy, with the exclusion of zinc) were measured. Triplicate tests were performed for each condition. RESULTS: The statistical analysis indicated that electrogalvanic activity is reduced significantly when the amalgam surface is treated with tin oxide or silver nitrate. Both zinc-containing amalgams in their as-carved condition exhibited higher anodic charge densities than did their zinc-free counterparts. Galvanic current measured in Dispersalloy was reduced with the passage of time after carving. CONCLUSION: Galvanic interaction between cast gold and amalgam is reduced with time and surface treatments, but is increased considerably when the amalgam contains zinc. CLINICAL IMPLICATIONS: Amalgam restorations containing zinc that are in contact with gold restorations occasionally elicit galvanic pain. Selection of a non-zinc-containing amalgam will reduce the level of galvanic interaction. Galvanic pain from occlusal contact is reduced or eliminated when the restoration is brushed with tin oxide immediately after carving or is treated with 2 percent silver nitrate. Some patients may benefit from having their teeth separated with nonconducting rubber dam material.     

口腔修复常用合金间瞬间电偶电流值的测定

目的 测定异种金属咬合接触时产生的电流值。方法 在人工唾液中体外模拟异种金属（金合金、纯钛、高含锌银汞和低含锌银汞）瞬间咬合接触时的回路。记录浸泡初各偶对的电位及瞬间接触电流值,继续浸泡8 h后再次测量,记录瞬间接触电流值。结果 多次瞬间接触引起的电流值变化无规律性。初浸时,金合金/纯钛、金合金/高含锌银汞、低含锌银汞/高含锌银汞偶对产生较大的峰值电流,纯钛/高含锌银汞偶对与其他偶对的电流值间差别有统计学意义（P<0.05）;浸泡8 h后,纯钛/高含锌银汞、纯钛/低含锌银汞偶对分别与金合金/纯钛、金合金/低含锌银汞、金合金/高含锌银汞的电流值间差别有统计学意义（P<0.05）;偶对浸泡8 h前后相比,只有金合金/高含锌银汞偶对的电流值间差别没有统计学意义>0.05）,金合金/低含锌银汞、纯钛/高含锌银汞的电流增加。高含锌银汞的电位较负,而且实验中始终为阳极,被加速腐蚀。结论 临床医师不可忽视使用异种金属修复体早期无不适感的病例。金合金/纯钛、金合金/高含锌银汞、低含锌银汞/高含锌银汞偶对若存在于口腔中,有可能对患者造成危害。金合金/低含锌银汞、纯钛/高含锌银汞偶对也不宜共存于口腔中。临床应尽量使用低含锌银汞或者无锌银汞合金。     

pH值对口腔修复常用合金间瞬间电偶电流的影响

目的:研究不同pH值对口腔修复常用合金间瞬间电偶电流的影响。方法:在3种pH值人工唾液中体外模拟异种合金瞬间咬合接触时的回路,浸泡初记录各偶对的电位及15个瞬间接触电流值。结果:金合金与纯钛在3种pH值中偶合所测得的电流与其他偶对差别均有统计学意义(P<0.05);金合金与无锌银汞、含锌银汞偶合产生的电流,仅次于金合金与纯钛偶合产生的电流;纯钛与无锌银汞、含锌与无锌银汞产生的电流也较大;纯钛与含锌银汞在3种pH值的溶液中产生电流最低、与其他偶对差别均有统计学意义(P<0.05)。结论:金合金与纯钛偶合,在3种pH值的溶液中产生电流均为最大,临床上危害最大;金合金与无锌、含锌银汞偶合,纯钛与无锌银汞、含锌与无锌银汞产生的电流也较大,临床慎用。纯钛与含锌银汞在3种pH值溶液中产生电流均处于最低,临床可共存应用。     

Existence of an electrically insulating layer in amalgam-containing galvanic couples.

OBJECTIVE: Avoiding the placement of amalgam and noble metal restorations in interproximal contact is recommended due to anticipated galvanic corrosion of the amalgam. There is a similar concern for amalgam/amalgam galvanic couples. It was the objective of this study to determine if an electrically insulating layer forms in the contact area of these galvanic couples. The existence of an electrically insulating layer, which could reduce the galvanic corrosion rate, would be indicated by different corrosion potentials for the two restorations of the couple. METHODS: Using a convenience sample of 158 human subjects, corrosion potentials were measured on each restoration of three types of galvanic couples: amalgam/noble metal (n=8), amalgam/amalgam (n=93) and noble metal/noble metal (n=7). Measurements were made with a Ag/AgCl micro-reference electrode and a high impedance voltmeter. All restorations were at least 6 months old. RESULTS: Statistical analysis showed that the mean absolute corrosion potential differences and the simultaneous confidence intervals of the couples were, respectively, amalgam/noble metal: 62 (31)mV and (27, 99)mV, amalgam/amalgam: 11 (14)mV and (7, 15)mV and noble metal/noble metal: 7 (10)mV and (0, 19)mV. SIGNIFICANCE: The amalgam/noble metal couples had consistent and mostly large corrosion potential differences between their restorations, which indicated the presence of an electrically insulating layer. An electrically insulating layer was also indicated for the amalgam/amalgam and noble metal/noble metal couples. The layer is probably composed of non-metallic corrosion products, biofilms, and possibly, dental calculus, which could reduce galvanic corrosion rates to small or negligible values.     

Galvanic currents between gold and amalgam

The galvanic currents between gold and amalgam were determined in vitro in aerated artificial saliva kept at 37°C. Using conventional amalgam, the current between gold and amalgam was rapidly fluctuating, and both the magnitude of this fluctuation and the maximum current density increased with increased ratio between the gold and the amalgam surface area (G/A). The current density exhibited by the non-γ₂ amalgam was lower, independent of G/A, and showed no fluctuations.     

In vivo galvanic currents of intermittently contacting dental amalgam and other metallic restorations.

OBJECTIVE: It was the objective of this study to determine the magnitude of in vivo galvanic currents produced by simulating electrical contact between occluding metallic restorations, and to examine the influence of restoration age, difference in pre-contact corrosion potentials, and surface area. METHODS: A convenience sample of 106 human subjects was studied. A Ag/AgCl micro-reference electrode and a high impedance voltmeter were used to measure the pre-contact corrosion potentials. Galvanic couples (n = 194) were next formed by simultaneously contacting occluding restorations with gold-plated probe tips for 15 s. The resulting current-time transients were measured with a zero-resistance ammeter and recorded with an electronic data acquisition program. The vast majority of couples measured contained at least one dental amalgam restoration. RESULTS: Galvanic current-time transients were typically characterized by an immediate and rapid rise to a peak current, followed by an exponential decay to a much lower value at 15 s. For couples with a restoration < or = 12 mo old, median peak current and median current at 15 s were 2.26 microA (range 0.24-13.06 microA) and 0.57 microA (range 0.03-6.47 microA), respectively. For couples with a restoration >12 mo old, median peak current and median current at 15 s were 1.40 microA (range 0.24-12.09 microA) and 0.37 microA (range 0.00-3.05 microA), respectively. Couples with fresh amalgams (< or = 6 mo) generally had elevated currents (range 2.56-102.54 microA). SIGNIFICANCE: A wide range of galvanic currents resulted from electrical contact of restorations in vivo. These currents were influenced by restoration age and total surface area of the galvanic couple. For amalgam-amalgam couples, the difference in the pre-contact corrosion potentials may be useful in predicting galvanic currents, when the difference is at least 24 mV.     

Galvanic currents between dental alloys in vitro

The galvanic current densities between gold, amalgam and cobalt-chromium, three different classes of dental alloys, were determined in vitro in artificial saliva kept at 35 degrees C. The maximum current density of 200 microA/dm2 was obtained between the conventional amalgam and a type III gold alloy. Galvanic currents of lesser magnitude could also be measured between amalgams high in copper and the other alloys. No measurable current densities were obtained between gold alloys and between gold and cobalt-chromium alloy with the exception of a casting and a solder gold alloy commonly used in combination.     

Galvanic currents between dental alloys in vitro

The galvanic current densities between gold, amalgam and cobalt-chromium, three different classes of dental alloys, were determined in vitro in artificial saliva kept at 35°C. The maximum current density of 200 μA/drn²was obtained between the conventional amalgam and a type III gold alloy. Galvanic currents of lesser magnitude could also be measured between amalgams high in copper and the other alloys. No measurable current densities were obtained between gold alloys and between gold and cobalt-chromium alloy with the exception of a casting and a solder gold alloy commonly used in combination.     

不同部位菌斑pH的动态变化及其与唾液的关系

目的：测定口腔不同部位菌斑在进食后pH的动态变化，探讨不同部位菌斑产酸力的差异及唾液在产酸代谢过程中的作用。方法：采用微型pH电极接触法原位测试患龋状况不同者上、下颌，健康部位与龋坏部位菌斑及唾液pH在含漱糖液前后1h内的变化。结果：不同部位菌斑pH在漱糖后均呈先下降后上升的趋势；患龋状况不同者健康部位菌斑pH在用糖后的变化无统计学差异；上颌菌斑pH变化幅度均较下颌明显；龋洞内菌斑pH变化幅度均较健康部位明显；唾液与菌斑pH间无明显相关性。结论：口腔不同部位菌斑内的产酸代谢活动存在差异，这可能主要与不同部位唾液对糖的清除有关；而唾液的缓冲作用对菌斑的产酸代谢无明显影响。     

Galvanic interaction between titanium and gallium alloy or dental amalgam.

OBJECTIVES: The objective was to examine in vitro the galvanic interaction between titanium and a high-copper dental amalgam or a gallium-based direct filling alloy at different area ratios, and to relate the observed interactions to the electrochemical characteristics of the alloys. METHODS: The tested materials were cast titanium, a single-composition, spherical high-copper amalgam, and a gallium-based direct filling alloy. Polarization curves were recorded. The galvanic couples were prepared at Ti/filling alloy ratios of 1:1, 2:1, 4:1 and 6:1. The couples were exposed to synthetic saliva at 37 degrees C and the galvanic currents and potentials were measured as a function of time. The results were analyzed by ANOVA and Tukey tests (p < or = 0.05). RESULTS: Freshly abraded titanium initially was anodic to both the amalgam and the gallium alloy, but the polarity reversed after a period of exposure. The galvanic potential and current density increased with the increasing Ti/alloy area ratio. The potential increase was smaller and the current increase larger for the Ga alloy than for the amalgam. The difference was consistent with the polarization characteristics. The galvanic current density was of the order of 10(-8) A/cm2 for the Ti/amalgam couple, and 10(-7) to 10(-6) A/cm2 for the Ti/gallium alloy couple. SIGNIFICANCE: The results show that the galvanic interaction between titanium and direct filling alloys is small. High copper dental amalgams should suffer little galvanic corrosion when in contact with Ti. For gallium direct filling alloys, the galvanic interaction may be more detrimental because of the inherently lower corrosion resistance.     

A galvanic study of different amalgams

Due to the difference in open circuit potential (OCP) versus SCE for Aristaloy amalgam (-969 mV) and Dispersalloy amalgam (-549 mV) in Ringer's solution at 25 degrees C, a galvanic cell was created with Dispersalloy amalgam as cathode and Aristaloy amalgam as anode. The galvanic corrosion current was studied as a function of time for the above cell as well as for a cell of type III dental gold (OCP is +0-5 mV) versus Aristaloy amalgam. The initial corrosion current of the latter cell (105 micronA) is about twice that for the cell of Aristaloy amalgam versus Dispersalloy amalgam (54 micronA), however, their passivating behaviour is quite similar. Also, an interrupted galvanic corrosion test simulating the oral 'make and break' situation was performed. A much higher corrosion current than the steady state was found when the two electrodes resumed contact.     

An in vitro study of galvanic currents between amalgam and gold alloy electrodes in saliva and in saline solutions

The galvanic currents between amalgam and gold alloy electrodes were higher in saline solutions than in saliva. Conventional amalgam supported higher currents than high copper amalgams when short-circuited with a gold alloy. The galvanic currents were not affected or affected only to a very small degree when whole saliva from different persons were compared. Higher currents were recorded when short-circuiting conventional amalgam and gold alloy electrodes using parotid saliva than when using whole saliva collected from one person. However, removing molecules with a molecular weight higher than 10(4) from whole and parotid saliva did not seem to affect the galvanic currents.     

An in vitro study of galvanic currents between amalgam and gold alloy electrodes in saliva and in saline solutions

Abstract – The galvanic currents between amalgam and gold alloy electrodes were higher in saline solutions than in saliva. Conventional amalgam supported higher currents than high copper amalgams when short-circuited with a gold alloy. The galvanic currents were not affected or affected only to a very small degree when whole saliva from different persons were compared. Higher currents were recorded when short-circuiting conventional amalgam and gold alloy electrodes using parotid saliva than when using whole saliva collected from one person. However, removing molecules with a molecular weight higher than 10⁴ from whole and parotid saliva did not seem to affect the galvanic currents.     

A measurement of galvanic current and electrical potential in extracted human teeth

When opposing teeth with amalgam and gold restoration are in contact, current flows in the mouth at the instant the dissimilar metals touch. In this study, this condition was simulated by use of resistors and extracted human teeth with amalgam and MOD gold inlay restorations. When both teeth were in contact in a physiological saline solution, we measured current and electrical potential generated in each pulp chamber. Galvanic current generated in the tooth with amalgam was always larger (as much as 18.2 times at the instant of contact) than that in the tooth with gold. Electrical potential generated in the tooth with amalgam was always larger (as much as 9.7 times at the instant of contact) than that in the tooth with gold. It should be emphasized that the larger current generated in the tooth with amalgam was caused mainly by its larger electrical potential. These results correspond well with the clinical phenomenon of galvanic pain, which occurs in the tooth with amalgam rather than in the tooth with gold.     

口腔修复常用合金稳态电位的测定

目的 评价口腔修复常用合金的稳态电位及其发生腐蚀的倾向。方法 测量五种修复常用合金在人工唾液中的初浸电位及24h后的稳态电位，并作统计学分析。结果 得出五种材料的电偶序为：金合金、纯钛、钴铬合金、无锌银汞、含锌银汞。浸泡24h前后，金合金、纯钛、钴铬合金均为正移，而无锌银汞则负向移动。无锌银汞和含锌银汞的电位有显著性差异（P〈0．05）。结论 金合金、纯钛、钴铬合金是耐腐蚀性较好的材料。无法避免不同金属的同时应用时，应尽量选择电偶序中相邻的两种金属。建议临床使用无锌银汞代替含锌银汞。     

Effect of chitosan rinsing on reduction of dental plaque formation

The purpose of the present study was to investigate whether the use of a chitosan mouthrinse could be efficacious in reducing plaque and saliva mutans streptococci level. A randomized crossover clinical trial was performed to evaluate the effect of a rinse with 0.5% chitosan for 14 days on plaque formation and mutans streptococci counts in saliva. Twenty-four subjects were randomly assigned either the chitosan rinse or a placebo rinse in addition to their usual oral hygiene procedures. Following the baseline examination, each subject was given a prophylaxis. They were instructed to rinse with 20 ml of the mouthrinse twice daily for 30 seconds. Plaque scores were measured after a 14-day rinsing period, and mutans streptococci counts in saliva were also determined at the start and the end of the each rinsing period. The procedures were repeated with the alternate rinse after a 14-day washout period. Rinsing with 0.5% chitosan was significantly more effective in plaque reduction using the Quigley & Hein Index (chitosan: 1.44, placebo: 1.62, p < 0.001) and Plaque Severity Index (chitosan: 0.138, placebo: 0.186, p = 0.003). The mutans streptococci count in saliva was less after the chitosan rinsing (chi 2 cal = 13.51, p = 0.035) than placebo rinsing. In conclusion, the chitosan rinsing was effective in reducing plaque formation and counts of salivary mutans streptococci after a 14-day rinsing period. These results would appear to warrant further investigation into the potential value of chitosan as an effective anti-plaque agent for use in oral hygiene products.     

Eight-year study on conventional glass ionomer and amalgam restorations in primary teeth

The aim of this randomized clinical study was to compare the longevity and the cariostatic effects of conventional glass ionomer and amalgam restorations in primary teeth placed in everyday practice in the Danish Public Dental Health Service. All restorations inserted during a 7-month period by 14 clinicians in 2 municipalities were included in the study. The sample consisted of 515 conventional glass ionomer restorations and 543 amalgam restorations in 666 children aged between 2.8 and 13.5 years. The restorations were in contact with 592 unrestored surfaces in primary and permanent teeth. The study was terminated after 8 years, with 2% of the restorations in function and 7% patient dropouts. Fifty percent of the teeth restored with glass ionomer and 63% of those with amalgam were exfoliated with the restoration in situ, while 42% of the glass ionomer and 20% of the amalgam restorations had been repaired or replaced. Fracture of restoration, endodontic complication, and loss of retention were the major reasons for failure. The 50% survival time for glass ionomer restorations in all cavity types was 42 months, while the median survival time for amalgam restorations could not be estimated but exceeded 7.8 years (P < 0.001). Progression of caries lesions on tooth surfaces adjacent to amalgam restorations required operative treatment on 30% of the teeth, while only on 16% of teeth adjacent to glass ionomer restorations. The 75% survival time was 40 months for surfaces in contact with glass ionomer compared to 25 months for surfaces in contact with amalgam (P = 0.005). Multivariate analyses were performed in order to assess the influence of a number of factors on the longevity of restorations, occurrence of prevalent failures, and caries treatment of surfaces in contact with the restorations. Owing to the high frequency of failures of the conventional glass ionomer restorations, it was concluded that they are not an appropriate, universal alternative to amalgam for restorations in primary teeth, although they reduce caries progression and the need for operative treatment of adjacent surfaces.     

Galvanic corrosion of selected dental alloys

Samples prepared from three different amalgam brands were coupled to two gold alloys and orthodontic brackets. In the resulting galvanic cells, the amalgam coupled to gold were anodic, exhibiting galvanic current densities about one order of magnitude higher than the uncoupled corrosion current densities of 0.2-0.5 microA. Coupling amalgams to orthodontic brackets resulted in galvanic current densities of the same magnitude as the uncoupled samples. Corrosion current densities at the anode were found to be up to six times higher than the measured galvanic current densities. Brushing caused transient increases in galvanic current densities that decayed within 100 s to the previous steady state levels. Brushing of amalgam/bracket couples, caused an anodic peak followed by brief polarization reversal during which the brackets were anodic.