This in-vitro study was conducted in Department of Prosthodontics and Implantology, Goverment Dental College and Hospital, Hyderabad, Telangana, India, from 2014 to 2015. The ethical clearance for this study has been obtained from the academic ethical clearance committee of Goverment Dental College and Hospital headed by Principal of the institution. The materials required were: 1) Retraction cords sizes 0, 1 and 2 (Ultrapak plain cord, Ultradent, South Jordan, U.S.A); 2) Retraction medicaments i.e., 15.5% ferric sulfate and 10% aluminum chloride (M.P. Sai Biomed, Mumbai, India); 3) Fluids used were artificial saliva (Saliveze, Wyvren Medical Ltd., Ledbury, U.K.), human plasma (G.V.K. Bio., Hyderabad, India); 4) Electronic analytical balance to measure weights (Sartorius, Sartorius India, Secunderabad, India); 5) Blotting paper (Yash Filters, Ahmedabad, India); 6) Pipette (Eppendorf India Ltd., Kilpauk, Chennai, India).

Each retraction cord was cut into 30 samples of 5cm length [Table/Fig-1]. Medicaments used were 15.5% ferric sulfate and 10% aluminium chloride [Table/Fig-2]. Of these 30 samples, 10 samples were used to measure dry weight. Of the remaining 20 samples of each thickness, 10 samples were immersed in 15.5% ferric sulphate and remaining 10 samples were immersed in 10% aluminum chloride. These were left immersed for a period of 20 minutes. The excess fluid was removed by blotting paper [Table/Fig-3] saturated in corresponding test solution held between thumb and index finger. Initial weight was recorded on electronic analytical balance [Table/Fig-4]. Following this, five cords from each group were immersed in plasma solution and remaining in artificial saliva solution [Table/Fig-5] for 10 minutes. Then these were taken out and weight was again measured. The amount of the fluid absorbed was determined by subtracting the weight before fluid immersion from the weight after fluid immersion. The amount of fluid absorbed in the dry retraction cord was obtained by subtracting the weight of dry cord from the weight of cord after fluid immersion (weight after immersion into test medicament). The amount of fluid absorption after medicament treatment was obtained by subtracting the weight after medicament immersion from the final weight after fluid immersion (weight after immersion into plasma or artificial saliva). Methodology of how the samples were divided into sub-groups is described in [Table/Fig-6].

[Table/Fig-1]:

Retraction cords cut into 30 samples.

[Table/Fig-2]:

Retraction medicaments.

[Table/Fig-3]:

Blotting paper.

[Table/Fig-4]:

Electronic analytic balance.

[Table/Fig-5]:

Artificial saliva and human plasma.

One-way ANOVA comparison was done between a dry cord, ferric sulfate and aluminium chloride at room temperature [Table/Fig-7]. The results of Bonferroni Post-hoc test show that there is a significant difference in absorbency between dry cord and ferric sulfate immersed cord. However, there was no significant difference between ferric sulfate and aluminium chloride immersed cords. Nevertheless the absorbency is more with ferric sulfate treatment [Table/Fig-8]. The results of present study show that the fluid absorbency with or without medicament increases as the thickness of the cord increases [Table/Fig-9,10].

[Table/Fig-10]:

The results of the present study shows that fluid absorbency with or without medicaments increases as the thickness of the cord increases.

With respect to treatment with 10% aluminium chloride, the cord which absorbed maximum fluid is size “2” in accordance with Spearman’s correlation test and the fluid which got absorbed highest was human plasma [Table/Fig-11,12].

[Table/Fig-11]:

As the thickness of the cord increases the amount of saliva absorption also increases. Saliva absorption is more in a retraction cord immersed in 15.5% ferric sulfate [Fe₂(SO₄)₃] compared to untreated cord and cord immersed in 10% aluminium chloride (AlCl₃) in all thicknesses.

[Table/Fig-12]:

As the thickness of the cord increases the amount of plasma absorption increases. The amount of plasma absorption is more in a retraction cord immersed in 15.5% ferric sulfate compared with the cord immersed in 10% aluminium chloride and untreated dry cord.

With respect to treatment with 15.5% ferric sulfate, the cord which absorbed maximum fluid is size “2” in accordance with Spearman’s correlation test and the fluid which got absorbed highest was human plasma [Table/Fig-11,12].

Of the two medicaments used in the study, artificial saliva and plasma absorption was more with 15.5% ferric sulfate when compared with 10% aluminum chloride irrespective of cord thickness [Table/Fig-12]. The fluid which was highly absorbed was human plasma in both the medicaments [Table/Fig-11,12].

The rationale behind the present study was to find out an effective mechanico-chemical retraction method with minimum systemic effects. Maintaining the marginal integrity of the tooth is one of the most important basic principles of tooth preparation [9]. From the periodontal point of view, it is preferable to place the gingival finish lines of restoration supra-gingivally [10], but studies show that sub-gingival margins do not cause gingival inflammation [11]. The dentist may be forced to place the margin sub-gingivally for aesthetics or other reasons like caries, existing restoration and when additional retention is required. Among various medicaments used as retraction agents, the one used in this study was 10% aluminium chloride and 15.5% ferric sulfate because they cause minimal tissue damage [6], is readily available and less systemic effects.

A study by Jokstad A revealed that the consistency of gingival retraction cord, twined or knitted, seems to be more important than the medicament when related to preference [12]. It is not surprising that the consistency of retraction cord has been associated with packing easiness and cord fraying. It is more difficult to explain why haemostasis, sulcus dilation, bleeding on removal, and dryness of sulci were rated better for knitted than twined retraction cords.

According to study done by Kumbuloglu O et al., proper hemostatic action is dependent on the amount of medicament solution absorbed by the cord during soaking, which is also dependent on length, thickness, structure, moistening properties of cord and length of soaking time [13]. Also for successful gingival retraction, soaking time in medicament is crucial for proper ingress of medicament into cord. An optimum time for soaking of retraction cords in medicaments is 20 minutes [14]. In current study, the retraction cords in the first group were incubated in their medicament solutions for 20 minutes before using, as recommended by Csempesz F et al., [15].

Fluid absorbing capacity of cords does not decrease when soaked in haemostatic solution like alum and aluminum chloride. However, study done by Garg SK et al., has proved that thicker retraction cords have better fluid absorbency than thinner cords irrespective of medicament used. Hence, it has been concluded that the amount of fluid absorbed increases in linear proportion with the size of cord [16].

Structurally Ultrapak cords have chain like interlocking loops which gives them an advantage of bending in any direction passively. When compared to conventional cords Ultrapak cords have superior medicament retention capacity of up to 2.5 times [17]. In order to find out the effect of cord diameter on absorbency of fluid three different sizes (0, 1 and 2) were selected. All the cords were of same length (5cm) and from same manufacturer.

Studies were done earlier to evaluate the chemical medicament absorption by the retraction cords (Runyan DA et al.,) [18]. This study aimed at determining whether the medicaments hamper or enhance or have no action on fluid absorbency of the knitted retraction cords. The retraction cords in addition to displacing the gingiva absorb moisture and fluids present in the sulcus to create a dry field for impression making.

The logic behind the selection of blood and saliva as immersion fluids was that we encounter these fluids during retraction and have to be cleared off for an acceptable impression. To simulate crevicular fluid in-vitro, human plasma was chosen as it contains proteins similar to crevicular fluid and blood [19]. To simulate saliva in-vitro, artificial saliva was chosen.

Clinical Implications: Fluid absorbency of the cords is important to maintain a dry field. Medicaments should not hamper this property of the retraction cords. So, this study helps in inferring that 15.5% ferric sulfate is a better medicament to increase the fluid absorbency of the retraction cords.

The limitations of the current study include that 15.5% ferric sulphate is acidic. The plasma used in the study differs from GCF in a few high molecular weight proteins and the artificial saliva doesn’t constitute all the components in saliva.

The current study was planned in view of mechanico-chemical retraction methods being extensively used in day today clinical practice. Further there is a scope for research towards more effective and less cumbersome retraction methods.

Medicaments and retraction cords are used in mechanico-chemical means of retraction of gingiva. The study gives a conclusion that irrespective of the medicament used, with increase in thickness of the retraction cord the fluid absorption increases. Both the medicaments can be safely used along with retraction cords as they do not decrease the fluid absorbency of the retraction cords when placed in gingival sulcus. The medicament better among the two (15.5% ferric sulfate and 10% aluminum chloride) used in this study was ferric sulfate for absorption of both human plasma and artificial saliva.