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Latex protective barriers such as gloves and rubber dam material have been used widely in restorative procedures for crown and bridge. However, the chemical used during latex glove fabrication is thought to inhibit the polymerization of elastomeric impression materials used for impression making which has a detrimental effect on the dimensional accuracy and surface definition of resultant casts used for restorative procedures. The objectives of the study were to examine the surface of different elastomeric impressions on contact with various gloves.
This clinical study included a total of eighty specimens of two types of the putty elastomeric impression material were hand manipulated by wearing three different gloves materials and is placed on a marked area of a clean and alcohol-treated glass slab at room temperature. The specimens examined for any signs of polymerization inhibition. The specimen will be rated as being “inhibited” if any residue remains on the glass slab and absence of the above will result as “no inhibition.”
The results showed no interference with the polymerization inhibition of the selected elastomers followed by the nitrile glove. The latex gloves showed inhibited set of the elastomeric impression material but set after sometime confirming time-dependent inhibition of the impression material.
This study shows that the use of latex and sometime nitrile gloves during crown and bridge procedures should be contraindicated and the use of vinyl gloves should be stressed when working with elastomeric impression materials.
An accurate reproduction of impression is of critical importance in the field of prosthodontics, implant, and restorative dentistry. With proper material selection and manipulation, accurate impressions can be obtained for fabrication of tooth- and implant-supported restorations. At the same time, the possible exposure to the transmission of infectious agents has given rise to concerns with cross-infection control to prevent cross-contamination. Among the adopted precautions, the routine use of disposable gloves, mainly latex ones, is an essential measure to break the chain of infection.[2,3,4] Latex gloves contain a sulfur compound, zinc diethyldithiocarbamate, used during latex glove fabrication, is a preservative and vulcanizing accelerator, which can completely inhibit polymerization of elastomers in concentrations as low as 0.005%.
In this study, two different brands of putty A-silicone putty impression material [Figure 1] - Zhermack clinical elite HD and C-silicone impression material - Zhermack clinical zetaplus; three different brands of gloves were used [Figure 2] (Latex [serjun], vinyl, and nitrile gloves) glass slab (to serve as the test surface to be impressed), blunt instrument (mixing spatula), and fast-drying alcohol. Base and catalyst putty material was dispensed and according to the manufacturer's directions. First, the putty impression materials are kneaded with the bare hands until homogenous mix was obtained for all the putty impression materials. Later, eighty specimens are prepared using both addition and condensation elastomeric impression materials and were divided into two groups: Group I addition elastomeric group and Group II condensation elastomeric group, and the specimens were obtained by a standardized plastic circular mold 20 mm in diameter and 7 mm in length. The addition elastomeric group is divided into Group A, B, C, and D and condensation elastomeric group is divided into Group A1, B1, C1, and D1 with ten specimens each were mixed with hands and gloved hands placed in an clean and alcohol-treated glass slab [Figure 3]. Each of the hand-manipulated material is allowed to set for 10 min or as per the manufacturer's specification when in contact with the surface to be impressed and then examined and carefully evaluated independently to determine the extent of polymerization of the impression material manipulated by various types of commercially available gloves.
The degree of polymerization was evaluated, and these observations were subjectively rated as “inhibited” if any residue remains on the glass slab or any area of tackiness on the glassy surface of the specimen. The absence of the above is rated as “no inhibition.”
The observations were also scored on a scale of 1–5 as follows:
Following the determination that complete inhibition has occurred, confirmation by the surface resistance to instrumentation was performed. The procedure described above is done for both groups of elastomers individually wearing different types of gloves and evaluated for polymerization inhibition of the same.
In the study, Table 1 shows addition silicone putty material with each ten specimens where Group B (latex gloves) showed four specimens inhibited and six specimens, noninhibited and rest Group A (control), Group C (vinyl gloves), and Group D (Nitrile gloves) showed none inhibited. Chi-square analysis was used to determine the inhibition and noninhibition between individual groups and Chi-square analysis revealed statistically significant results (P = 0.004). Table 2 shows condensation silicone putty material with each ten specimens where Group B1 (latex gloves) showed ten specimens inhibited, and six specimens from Group D1 (Nitrile gloves) inhibited and rest Group A1 (control) and C1 (vinyl gloves) showed noninhibited. Same Chi-square analysis was used to determine the inhibition and noninhibition between individual groups and Chi-square analysis revealed highly statistically significant results (P < 0.001).
Graph 1 shows the polymerization inhibition frequency between Group A, Group B, Group C, and Group D for addition silicone putty material. Group B shows the frequency of inhibition and rest Group A (control), Group C (vinyl gloves), and Group D (Nitrile gloves) showed noninhibited.
Graph 2 shows the polymerization inhibition and the noninhibition frequency between Group A1, Group B1, Group C1, and Group D1 for condensation silicone putty material. Group B1 and Group D1 showed frequency of inhibition and the rest Group A1 (control) and Group C1 (vinyl gloves) showed noninhibited.
The increased wearing of gloves during dental treatment has created new problems for general dental practitioners but remain prevalent in clinical use because of the attributes of puncture resistance, durability, and user satisfaction.[6,7] Clinical misadventures can be avoided by knowing the manipulated variables when using elastomeric impression materials.
Latex gloves and rubber dam are two prominent infection barriers within the scope of infection control guidelines. Polymerization inhibition of elastomeric material with the use of latex gloves leads to partial or incomplete polymerization which has a detrimental effect on dimensional accuracy and surface definition of the resultant casts used for restorative procedures. Sulfur as a reactive element contained within latex gloves or rubber dam material may react with chloroplatinic acid catalyst in elastomeric impression material, even with concentrations as low as 0.05% may totally inhibit the polymerization reaction.[6,9]
Polymerization inhibition can occur when putty materials are mixed with latex gloves, when the impression material is in contact with a rubber dam, and even by indirect intraoral contact of teeth and soft tissue structures with latex glove before impression making, and the inhibition of set is limited to the most superficial layer of the impression material. Even contact of the internal surface of the impression tray with gloved hands can also result in failure of the impression material adjacent to the tray to polymerize.
Polymerization inhibition of VPS impression material may not always be readily observed through an entire impression arch. Subtle surface changes or localized areas of an impression material inhibition within a full arch impression might be easily hidden or missed on clinical observation.
Polymerization inhibition of VPS impression material might be reduced or eliminated by mechanical decontamination before impression procedures.
Transferred small particulate contaminants from latex gloves were not found to be removable by any of the cleaning methods evaluated and that such procedures may be unsuccessful on the surface of vinyl gloves. The clinical removal of invisible, microscopic, trace contaminants from the clinical field does not appear possible. Cleansing attempts may not reduce the potential for inhibition of VPS impression material polymerization caused by sulfur contaminants. Gauze or brush rubbing with or without surfactant cannot remove the trace elements demonstrated to be present following contamination with sulfur-containing materials.
The use of surfactant can improve wettability of VPS materials after exposure to saliva, water, and disinfectants. Polymerization inhibition during the initial pilot study, when the impression materials were allowed to set in sustained, direct contact with the gloves suggesting a time-dependent interaction between the glove component and the PVS polymerization reaction. Within the recognized limitations of the experimental design, there was no inhibition of the three tested VPS materials when indirectly exposed to these gloves by rubbing contact, as long as the gloves were not exposed to alcohol. He suggested that the rubbing of the treatment area with wet or washed glove hands is unlikely to cause polymerization inhibition and that when the impression material or the impressed surface previously exposed to latex glove in contact with alcohol is avoided; risk of polymerization inhibition is reduced. He stated that it is of potential clinical relevance because of widespread use of alcohol in practice and it may prove prudent for dentists to avoid unnecessary alcohol exposure when making impressions with PVS materials.
A study was, therefore, undertaken to evaluate the polymerization inhibition of some commercially available elastomeric impression materials (an addition silicone, a condensation silicone, and a polyether) on contact with various types of gloves (latex, synthetic, nitrile, vinyl, and flavored glove) and surfactants (rubbing alcohol) available in the market.
Polymerization inhibition of elastomeric impression materials has been studied in a number of ways the extent of polymerization of the impression material by visually scoring the material as either inhibited or noninhibited according to the following criteria. Inhibited was scored if one or more of the following was encountered in the impression:
If none of these criteria were observed, the impression was scored “noninhibited.” One of these is the retarded set or total inhibition of addition silicones caused by natural latex gloves.
A pilot study confirmed that polymerization inhibition is easily determined through visual examination and evaluation of topographic character of the material although other methods have been used. The material is either completely polymerized or inhibition is immediately and obviously evident. When polymerization inhibition occurs, unset residue remains on the impressed surface, the partially polymerized impression material remains tacky to touch, and the material is subject to permanent distortion when slightly scraped with a blunt hand instrument.
Another method after dispensing impression material on a glass slab exposed to various combinations of variables to simulate clinical contamination resulting from contact by gloved hands and then cleaning the glass slab with soap and water, followed by rinsing with tap water for 60 s and drying. The specimen was then lifted from the testing surface at the applicable time as per manufacturer's instructions and then examined independently to determine if polymerization inhibition occurred. If any residue remained on the glass surface, the specimen was rated as being inhibited, and absence of residue resulted in a rating of no inhibition.
In the present study, putties were mixed according to manufacturer's instructions and placed on a glass slab. Setting was determined by sliding the end of a cement mixing spatula over the mixed putty. Complete setting was determined to be present when the instrument would not permanently indent the material.
For Maintaining Standarisation A Single Operator Used Gloves Of 3 Different Materials To Hand Manipulate The Elastomeric Impression Material And Placing It On A Clean Glass Slab And Alcohol Treated Slab At Room Tmperture And Was Evaluated Invitro For Polymerisation. The Required Base And Catalyst Was Calculated From The Given Proportion System
All the impression materials were mixed after gloving hands within 30–40 s and placed on the clean glass slab (control) and an alcohol-treated glass slab. Mixing and placement of the impression material were done in 60 s. The working time was measured as the loss of tackiness of the mixed impression material using a blunt instrument. Each of the hand-manipulated material is allowed to set for 10 min or as per the manufacturer's specification when in contact with the surface to be impressed and then examined and carefully evaluated independently to determine the extent of polymerization of the impression material manipulated by various types of commercially available gloves.
The procedure described is done for both groups of elastomers individually wearing different types of gloves and evaluated for polymerization inhibition of the same.
A pilot study evaluated the degree of polymerization and subjectively scored his observations on a scale of 1–5 as follows:
Following the determination that complete inhibition has occurred, confirmation by surface resistance to instrumentation was performed. No further determination of polymerization inhibition was performed for conditions 1–4.
The clinical significance of the study reveals that the vinyl and nitrile gloves can be used to make impressions without any inhibition of impression material and therefore the resultant casts obtained from these impressions are highly accurate, thus yielding a more precise final restoration
This in vitro study showed that different gloves reacted differently on contact with elastomeric impression materials when exposed directly to the glove alone or the glove/surfactant combination. The latex glove inhibited the polymerization of the elastomers after mixing directly with the glove; hence these elastomers should be protected from exposure directly or indirectly to latex gloves or its variants, and sometimes even nitrile showed inhibition. The vinyl glove did not inhibit the polymerization of the addition silicone and condensation silicone. Unnecessary alcohol exposure should be avoided.
There are no conflicts of interest.