Examining the Effect of Gravity on Different Irrigation Systems: An In vitro Study.

BACKGROUND: Periapical extrusion is frequently observed during endodontic therapy. It can lead to acute injury of periapical tissues, resulting in interappointment pain or swelling. The effect is pronounced in teeth with immature apex, which are more susceptible to the extrusion of irrigant. The aim of this study was to evaluate the effect of gravity on the apical extrusion of irrigating solution with different irrigation protocols in single-rooted premolars.
METHODOLOGY: A total number of 80 permanent single-rooted teeth (premolars) with same working length (WL) were divided into two main groups: Group A: Penetration depth of irrigation syringe to 2 mm from the WL and Group B: Penetration depth of irrigation syringe to 4 mm from the WL. Each group was subdivided into four subgroups. (n = 10). The extruded debris and irrigants were weighed, and the data were statistically analyzed by the analysis of variance and the Tukey test.
RESULTS: Irrespective of the irrigation technique used, the amount of irrigant extruded from the apex showed a statistically significant difference related to the effect of gravity (P < 0.05). There was no statistically significant difference observed between irrigation methods (P > 0.05).
CONCLUSION: The degree of apical extrusion of irrigant was dependent on the type of irrigation technique and gravity. Greater caution should be taken during irrigation to prevent postoperative pain. Copyright:

INTRODUCTION

In endodontic treatment, chemomechanical debridement is an important part. Many different irrigation techniques and devices have been used to improve disinfection of the root canal system. For optimal effectiveness of the irrigation, the irrigant should make direct contact with all parts of the canal wall. A flushing action, which is crucial and dependent on the many factors such as the insertion depth, diameter of the needle, and the final size and taper of the prepared root canal, is necessary for optimal cleaning of the root canal. The conventional endodontic manual irrigation syringe and needle is the most widely used technique because it is very easy to manipulate and affords good control of needle depth and the volume of irrigant delivered.[12345] However, it's safety has always been questioned because of the positive pressure used to introduce the irrigant into the canal, which could cause the solution to extrude into the periapex despite strict control of the working length (WL) and result in severe tissue damage and postoperative pain. Tissue reactions following instrumentation short from the apex are milder than those reactions that follow instrumentation beyond the apex. Therefore, the amount of apically extruded debris should be minimized to minimize postoperative reactions.[3] Extrusion during endodontic irrigation has been researched with both in vitro and in vivo models using various delivery systems and techniques. A majority of in vitro studies are performed on the mandibular model to investigate the extrusion from the root apex.[67] Gravitational force that influences every object in the universe. Since the chair/patient position differs during endodontic treatment on the maxillary or mandibular teeth, it can be acknowledged that the gravitational force will have different influences on the flow and velocity of irrigant in both the jaws. The influence of gravity has not been elucidated on apical extrusion of irrigant in the case of immature permanent teeth.[8910] Thus, the aim of the study was to investigate the effect of gravity on apical extrusion of irrigant in the case of permanent premolars teeth.

METHODOLOGY

Preparation of the samples

Eighty freshly extracted single rooted premolar with mature apex were used in this study. After access opening for all teeth the WL was determined by placing #10 K file with a rubber stop carefully inserted into each canal until it was just visible in the apical foramen, this length was noted and 1 mm was subtracted to give the WL of the canal and all the selected teeth WL corrected to 19 mm. The teeth were prepared with Protaper (Dentsply, Maillefer) hand system in crown-down approach, and the instruments were used according to the manufacturer's instructions. The apical enlargement was done to size F3 (D0 = 30) 8. In each group, 30 s irrigation 9 with 4 ml of normal saline was used after each file with total irrigation time of 120 s. After canal preparation, a method of Myers and Montgomery10 was followed, the apex of teeth were forced through a precut hole in a rubber stopper, then placed on the glass shell vials. A 27G needle was placed through the stopper into the flask to equalize the air pressure inside and outside the vial. In this study, we used open-end needle gauge 23 and double side-vented needle gauge 23 with disposable syringe and open-end needle gauge 23 and double side-vented needle gauge attached to (Aqua-pick 300) which produced water jet with 100 psi pressure and with 1800 pulsations per minute on its end and fix them by a glue to used it inside canal.

Grouping

Prepared specimen were divided into two Groups A and B, and each groups were subdivided into four subgroups of 10 teeth each [Table 1].

Table 1

Grouping of the premolars

Group A: Irrigation was made to 2 mm from working length

Group A1: Irrigation was made by open-end needle with syringe

Group A2: Irrigation was made by double side-vented needle with syringe

Group A3: Irrigation was made by open-end needle attached to Aqua-pick300

Group A4: Irrigation was made by double side-vented needle attached to Aqua-pick300

Group B: Irrigation was made to 4 mm from the working length

Group B1: Irrigation was made by open-end needle attached to syringe

Group B2: Irrigation was made by double side-vented needle attached to syringe

Group B3: Irrigation was made by open-end needle attached to Aqu-pick300

Group B4: Irrigation was made by double side-vented needle attached to Aqua-pick300

Preparation of a model for the simulation of effect of gravity is on in the maxillary and mandibular arches. For simulating the tooth position in both the arches extra-orally, a custom-made model with a base and arm fixed at 45° inclined plane was made by wooden sticks. The hole was drilled into the wooden sticks of base and inclined arm to receive the tooth model assembly and simulate the tooth position in the maxillary arch and mandibular arch.

Debris and irrigants weighting

After complete instrumentation and irrigation specimens were removed from the apparatus and the vial then weighed three times on a precision electronic balance (Acculab-R-LSeries LA 60, Totalcomp, Inc, Fair Lawn, NJ, USA). The weight of the irrigant was calculated as the difference between the pre and post instrumentation weights. All irrigation and weighing procedures were carried out by the same operator.

RESULTS

The aqua-pick device with double side-vented needle with penetration depth of 4 mm from full WL had the lowest amount of apically extruded irrigants compared with the other experimental groups (P < 0.001) while aqua-pick with double side-vented needle inserted 2 mm from the full WL had the highest amount of apically extruded irrigants among the experimental groups. Furthermore, there was a statistically high significant difference between the groups according to the one-way analysis of variance (ANOVA) and Tukey test ANOVA (P < 0.001), as shown in Table 2. The mean and standard deviation of extruded irrigant for each group (gram) * was for maxilla 0.4187 ± 0.5000 and for mandible 0.6539 ± 0.5230. The amount of irrigant extruded from the apex showed a statistically significant difference related to the effect of gravity (P < 0.05). There was no statistically significant difference between irrigation methods (P > 0.05).

Table 2

Tukey test was made between groups

Tukey	HSD groups	Mean difference	P	Significant
A1	A2	0.50187*	0.000	HS
	A3	0.60122*	0.000	NS
	A4B1	−0.50111*	0.000	HS
	B2	−0.70138*	0.000	HS
	B3	−0.50100*	0.000	HS
	B4	−0.90110*	0.000	HS
A2	A3	−0.00003*	0.000	HS
	A4	−0.50149*	0.000	HS
	B1	−0.60129*	0.000	NS
	B2	−0.50147*	0.000	HS
	B3	−0.60131*	0.000	HS
	B4	−0.21321*	0.000	HS
A3	A4	−0.60129*	0.000	HS
	B1	−0.50141*	0.000	HS
	B2	−0.60121*	0.000	HS
	B3	−0.50141*	0.000	NS
	B4	−0.60113*	0.000	HS
A4	B1	−0.50000*	0.000	HS
	B2	−0.60120*	0.000	HS
	B3	−0.50147*	0.000	HS
	B4	−0.20223*	0.000	HS
B1	B2	−0.80131*	0.000	HS
	B3	−0.60000*	0.000	NS
	B4	−0.22222*	0.000	HS
B2	B3	−0.60129*	0.000	HS
	B4	0.04810	0.000	HS
B3	B4	0.09405	0.000	HS

*The mean difference is significant at the 0.05 level. HSD: Honestly significant difference, NS: Not significant, HS: Highly significant

DISCUSSION

Irrigation needles are designed primarily to maximize effective irrigation while protecting the periapical tissues.[1112] Studies determining the best irrigation needle design are lacking and therefore, newly designed irrigation tips are constantly introduced on the market.[512] Periapical extrusion has been extensively studied and reported in the literature in terms of irrigating solution, bacteria, and debris.[13] The majority of the studies on extrusion have used permanent teeth with mature apex with limited experiments performed on immature or open apex teeth. Since the flow of irrigant is governed by the external forces such as pressure difference, buoyancy, and gravity, the influence of later on the peri-apical extrusion cannot be ruled out. Currently, limited studies have examined the effects of gravity on extrusion in the tooth with mature apex.[101415] However, this is the first study to demonstrate the effect of gravity on periapical extrusion of irrigating solution in immature anterior teeth. Varieties of irrigation and agitation systems have been developed to improve the disinfection. Nevertheless, some peri-apical extrusion may be observed regardless of the irrigation system or technique used, when the root canal is prepared up to apical constriction, and apical patency is preserved.[16] The absence of apical constriction provides the irrigating solution and unhindered access to periapical tissues in mature teeth. The risk of extrusion further increases in immature teeth with divergent or parallel root canals with the absence of apical constriction and wide apical foramen. A negative pressure irrigation technique is recommended in such teeth to minimize periapical extrusion.[9] The results of a recent in vivo study suggest that Er, Cr: YSGG laser activated or passive ultrasonic irrigation is safe to use in teeth with open apex.[17] Since it is difficult to clinically assess and quantify debris or solution extruded, the majority of data are based on ex vivo studies. Different methods have been reported in the literature to quantify the periapical extrusion using linear measurement, volume, weight, and electrolyte concentration.[1718] The inability to replicate the periapical environment is the biggest limitation of in vitro studies. The floral foam has been used in few experiments to simulate the resistance by periapical tissues. However, absorption of fluid by foam repeatedly results in the underestimation of extrusion.[19] Irrigation with Aqua-pick and double side-vented needle with penetration depth of 4 mm from the apex produced less amount of apical extrusion of irrigants this in agree with previous studies.[41314] Side vented is closed apically thus create more pressure on the walls of the root canal and improves the hydrodynamic activation of an irrigant and reduces the chance of apical extrusion which allows the irrigant to reflux and causes more debris to be displaced coronally, while avoiding the inadvertent expression of the irrigant into periapical tissues. According to the result of this study, the depth of insertion 4 mm from the WL produced less apically extruded irrigants when compared to 2 mm from the working length. The further the needle is positioned away from the apex, the less apical pressure is developed this finding was in agreement with previous study.[14]

CONCLUSION

The degree of apical extrusion of irrigant was dependent on the type of irrigation technique and gravity. Greater caution should be taken during irrigation to prevent postoperative pain.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.