The fit of a restoration can be considered “passive” if it does not create any static loads within the prosthetic system or in the surrounding bone tissue. In case of misfit between abutment and prosthesis, compressive and traction loads could be directed to the restoration, resulting in loosening of the prosthesis and abutment screws, fracture of the restoration, bone micro fractures surrounding the implants and even fracture of the implant body^1-6). Such a misfit will also lead to problems with articulation of working cast, axial contouring of interproximal contacts, open margins, lack of retention and resistance to displacement^7,8).

Marginal discrepancies caused by the misfit might enhance plaque accumulation, affecting soft and/or hard tissue around the implants^9-11). The clinically acceptable level of discrepancy of the framework have been reported in the range of 10 µm to 150 µm based on various clinical studies^12-14). An accurate impression is mandatory to ensure acceptable fit of an implant-supported prosthesis^2,15,16). The accuracy of impression is influenced by various factors such as depth and angulations of implants, position of implants, impression materials, impression technique, type of impression trays, different impression level (implant or abutment level), design of impression copings, splinting or non-splinting of impression copings, time delay for impression pouring^8,10,17-21).

The direct (open tray) and indirect (closed tray) techniques have been advocated in the literature for implant/abutment level impressions to ensure the passive fit of the prosthesis^7,22-27). Also, the closed tray technique is found to be more accurate when the inter-implant angulation is within 15°∼20° in a randomly distributed single implant situation in a partially edentulous arch^28,29). The reorientation of the impression coping – implant replica assembly within the impression might reflect an error in the vertical axis^24,25,30-33). The instances of impression material being distorted or damaged is also possible while using closed tray technique in multiple implant situations, especially if implants are not parallel to each other^4,17,34).

The advantage of the open tray technique is that, the coping remains within the impression and so there need not be any concern for replacing it into its respective space as done in closed tray impression technique^{4,7,17,25,30,35,36)}. Also, the concern of angulated implants deforming the impression material upon removal of the impression does not arise. Splinting of the open tray impression coping has been suggested by many authors in order to maintain the accurate inter-implant relationship, when compared to that obtained with non-splinted impression copings^18,35,37). Individual variations in hand-tightening torque might lead to rotation of impression copings within the impression³⁸⁾. The impression material used for making implant impressions should possess sufficient rigidity to prevent accidental rotation of the coping and exhibit minimal positional distortion^21,31). Various impression materials are recommended for making implant impressions which will include polyether and addition silicone^{21,24,35,37,39,40)}. Polyether has been suggested for completely edentulous multiple-implant situations due to its excellent resistance to permanent deformation, favourable shore hardness, low strain under compression and high tear resistance^17,41). The use of polyether impression material for a partially edentulous situation presents the difficulty of retrieving the set impressions intraorally because of its high rigidity^42,43). Addition silicone with its more favourable modulus of elasticity allows easy removal of the set impression in a partially edentulous situation^41-43). The elastic recovery of the vinylpolysiloxane allows set impression to be removed without distortion even though the angulation of the impression copings is unfavourable³⁹⁾. Every step in the implant prosthesis fabrication introduces certain degree of inaccuracies, one of the method to enhance the precision is omitting some of the fabrication steps and utilization of a well-developed industrialized engineering approach by means of Computer Aided Design and Computer Aided Manufacturing (CAD/CAM). Computer Numeric Controlled (CNC) – milled titanium framework was shown to exhibit better fit than cast frameworks and restorations. Vigolo et al.^8,44) compared the master cast accuracy in two studies. Lorenzoni et al.⁴⁵⁾ compared the accuracy of implant impressions with different impression materials and reported no difference. None of these studies compared the accuracy of the fit of implant crowns obtained from the implant level impression techniques for a single-tooth implant replacement. Studies on the accuracy of the fit of the implant crowns fabricated from different impression materials using open tray impression technique are lacking in the literature. In view of the above, there is a need to identify the ideal impression material to obtain the accurately fitting implant crown in single-tooth implant replacement using open tray impression technique.

A cuboidal stainless steel block was fabricated with the dimensions of 26 mm×15 mm×14 mm. A cylindrical well was milled in the stainless steel block with the diameter of 4.4 mm and depth of 9 mm. An elevated metal projection with dimensions of 9 mm×7 mm×6 mm was also milled proximal to the cylindrical well to simulate a natural tooth. A rectangular flat surface of 3 mm×2 mm was created on the axial surface of the simulated natural tooth adjacent to the cylindrical well while milling the stainless steel block. A step feature was milled on the periphery of the stainless steel block with a dimension of 2 mm×2 mm to aid in the orientation of the custom open tray.

An implant replica (Nobel Replace, Nobel Biocare AB, Goteborg, Sweden) of 4.3 mm diameter with the internal tri-channel connection was connected to its respective open tray impression coping (Nobel Replace, Nobel Biocare AB, Goteborg, Sweden). The cylindrical well of the stainless steel block and axial surfaces of the implant replica were air abraded with 110 µm alumina particles (Aluminium oxide; Delta, Vijay Dental Depot, India). The Type I Glass Ionomer cement (GC Corporation, Tokyo, Japan) was mixed according to the manufacturer's instruction and was applied to walls of the cylindrical well and the axial surface of the implant replica. The implant replica-impression coping assembly was cemented to the cylindrical well of the stainless steel block in such a way that the interface of the implant replicaimpression coping assembly was kept 2 mm above the top plane of the stainless steel block. Thus, the reference model was obtained.

The open tray impression coping was connected to the implant replica (Fig. 1). Modelling wax (Hindustan Dental Products, India) was adapted over the simulated natural tooth and the open tray impression coping on the reference model to obtain the uniform spacer thickness. Vinylpolysiloxane impression material (Aquasil Soft Putty & Light body, Denstply, Germany) was used to make impression of the spaced reference model. Impression was poured with Type IV dental stone (Ultrarock, Kalabhai, India). Thus, the spaced primary cast of the reference model was obtained.

Figure 1. Reference model showing implant replica –impression coping open tray assembly with simulated natural tooth by the side.

A light polymerizing resin sheet (Delta, Vijay Dental Depot, India) of 2 mm thickness was adapted on the spaced primary cast. Later, it was placed inside the light curing unit for 6 minutes and light cured. The tray was removed from the model and kept inside the curing unit for another 6 minutes. A round opening was made on the occlusal surface of the tray to gain access to the open impression tray coping screws. The finished tray was placed on the reference model to verify its proper orientation. In this manner, 20 custom trays were made for open tray implant level impressions. All the trays were left undisturbed for 24 hours, for the trays to become dimensionally stable prior to impression making. These trays were used to make open tray implant level impressions.

A total of 20 custom trays were fabricated. The custom trays were grouped as Ten custom trays were randomly selected for making impressions with vinylpolysiloxane material (Group I) (n=10). Ten custom trays were randomly selected for making impressions with polyether material (Group II) (n=10). The open tray implant level impression coping (Nobel Replace Internal trichannel;, Nobel Biocare AB, Goteborg, Sweden) was connected to the implant replica of the reference model with the screw driver. The custom tray was coated with a thin layer of vinylpolysiloxane tray adhesive (3M ESPE; Seinfeld, Germany) and allowed to dry for fifteen minutes as per the manufacturers' recommendation. Putty consistency vinylpolysiloxane impression material (Express XT Penta putty; 3M ESPE, Seinfeld, Germany) was machine mixed (Pentamix 2, 3M ESPE, Seinfeld, Germany) and loaded into the custom tray keeping the tip immersed in the material all the time. The light body (Light body Express XT; 3M ESPE, Seinfeld, Germany) was syringed around the impression coping and the simulated natural tooth by another operator simultaneously. The tray was positioned on the reference model immediately. The excess impression material that had flown over the coping of the custom tray was removed to expose the head of the coping screw through the window in the custom tray. The impression was allowed to set undisturbed for 3 minutes as per the manufacturers’ recommendation. After the complete polymerization of the impression material, the coping screw was unscrewed with a screw driver and the impression was retrieved from the reference model. A total of ten open tray implant level impressions were made using vinylpolysiloxane impression material and they were designated as Group I.

Medium body polyether (Impregum Penta; 3M ESPE, Seinfeld, Germany) was machine mixed (Pentamix 2, 3M ESPE, Seinfeld, Germany) and loaded into the custom tray keeping the tip immersed in the material all the time. It was also syringed around the impression coping and the simulated natural tooth by another operator using the Pentasyringe. The tray was then positioned on the reference model immediately. The excess impression material that had flown over the coping of the custom tray was removed to expose the head of the coping screw through the window in the custom tray. The impression was allowed to set undisturbed for 6 minutes as per the manufacturers’ recommendation. After the complete polymerization of the impression material, the coping screw was unscrewed with a screw driver and the impression was retrieved from the reference model. A total of ten open tray implant level impressions were made using polyether impression material and they were designated as Group II.

The above impressions were boxed with boxing wax. Type IV dental stone was mixed using the vacuum mixer (Twister Evolution Vacuum Mixer, Renfert, USA) following the manufacturers’ recommendation of 100 gm of powder to 20 ml of water. The mixed dental stone was poured within the boxed impression using vibrator (Confident Dental Equipments Ltd, Bangalore, India). The cast was allowed to set for 2 hours. Then the cast was retrieved from the impression after unscrewing the coping screw. All casts were poured in a similar manner to standardize the errors due to the dental stone expansion. A total of 20 master casts were obtained, 10 casts for each Group.

The implant crowns were fabricated by CAD/CAM method using third party software and milling machine. Desktop scanner (IDENTICA T500, MEDIT corp., Seoul, Korea, Yenadent D15 milling machine). After milling, the implant crown was connected to the implant replica of their respective working cast using an abutment screw. All 20 screw retained titanium implant crowns were milled for Group I (n=10) and Group II (n=10), (Fig. 2, 3). Then the proximal contact of each implant crown was evaluated with 8 µm thickness articulating foil to ensure uniform contact with the adjacent simulated natural tooth for all the test samples. Each implant crown was removed from the working cast and connected to the implant replica of the reference model with 35 Ncm torque using calibrated torque wrench and subjected for the evaluation of the interface gap and the proximal gap. The same procedure was repeated for all the 20 test samples (Group I - n=10, Group II - n=10). The interface gap of the implant crown and the implant replica and the proximal gap of the implant crown on the reference model was evaluated under Scanning Electron Microscope for each sample. The interface gap on the implant crown adjacent to the simulated natural tooth was considered as the mesial point and the interface point away from the simulated natural tooth was considered as the distal point. When viewed from the side with the simulated natural tooth on the left and the implant crown on the right side, the area viewed was considered as the buccal aspect and the opposite side was considered as the palatal aspect.

Figure 2. Milled screw retained titanium implant crowns – Group I.

Figure 3. Milled screw retained titanium implant crowns - Group II.

The reference model with the implant crown was secured onto the carbon stub with double adhesive tape. The model was placed in such a way that the interface part between the implant crown and the implant replica was perpendicular to the beam of light produced in the SEM. The carbon stub with the reference model was introduced and the height was adjusted to +18 mm in the software to accommodate the height of the reference model in the SEM. The machine was closed and the vacuum was created. The implant abutment interface was focused and the brightness and contrast were adjusted. An image of the interface area between the implant replica and the implant crown was captured at 25X magnification. The mesial (proximal to the simulated natural tooth) and distal (opposite side of the simulated natural tooth) points at the interface were then captured under 190X magnification (Fig. 4). In order to evaluate the interface gap, the gap between the implant replica and the implant crown at the mesial and distal points were measured. The same procedure was repeated for all the test samples (Group I- n=10, Group II- n=10). The reference model with the implant crown was secured onto the carbon stub with double adhesive tape. The model was placed in such a way that the occlusal part of the implant crown and the simulated natural tooth was perpendicular to the beam of light produced in the SEM. The carbon stub with the reference model was introduced and the height was adjusted to +25 mm in the software to accommodate the height of the reference model in the SEM. The machine was closed and the vacuum was created. The proximal contact area from the occlusal view was focused. The brightness and contrast were adjusted. An image of the proximal area of the simulated natural tooth and the implant crown was captured at 37X magnification. In order to evaluate the proximal gap, the gap between the implant crown and the simulated natural tooth at the buccal and the palatal proximal contact points were measured at 190X magnification (Fig. 5). The same procedure was repeated for all the test samples (Group I - n=10, Group II - n=10). All the measurements were made by the single operator to avoid inter operator error. The mean values of each group were obtained and they were statistically analyzed, tabulated using Mann Whitney non parametric test (SPSS25,IBM,USA). Level of significance was P<0.05 considered significant.

Figure 4. SEM image of mesial and distal point at interface at 190X magnification. Arrow shows the interface gap.

Figure 5. SEM image of buccal and palatal point at interface at 190X magnification. Arrow shows the interface gap.

The mean interface gap at the mesial and distal points of the implant crowns obtained from vinylpolysiloxane and polyether materials were 20.72 µm and 4.9 µm and 15.15 µm and 8 µm respectively. The interface gap at the mesial points was significantly higher than the distal points.

The mean proximal gap at the buccal and palatal points of the implant crowns obtained from vinylpolysiloxane and polyether material were 26.43 µm and 72.49 µm and 19.95 µm and 57.9 µm respectively. The proximal gap at the palatal point was significantly higher than the buccal point. The higher value at the palatal point could be attributed to rotation and/or axial inclination of the impression coping (Table 1, 2).

Table 1 . Basic values of the interface gap at the mesial, distal, buccal and palatal points of the implant crowns obtained from vinylpolysiloxane material (Group I)

Sample no.	Mesial (µm)	Distal (µm)	Sample no.	Buccal (µm)	Palatal (µm)
1	04.17	03.14	1	01.04	50.01
2	81.00	05.21	2	82.58	97.92
3	40.77	02.09	3	40.48	117.28
4	10.42	02.09	4	01.04	41.52
5	15.63	04.17	5	29.07	47.75
6	06.23	03.14	6	17.71	33.33
7	08.33	06.25	7	28.22	127.40
8	10.45	10.42	8	03.29	110.03
9	04.17	07.29	9	15.32	47.92
10	26.04	5.21	10	45.52	51.72
Mean	20.72	4.90	Mean	26.43	72.49

The mean interface gap at the mesial and distal points of the implant crowns obtained from vinylpolysiloxane material were 20.72 μm and 4.90 μm respectively. The mean proximal gap at the buccal and palatal points of the implant crowns obtained from vinylpolysiloxane material were 26.43 μm and 72.49 μm respectively.

Table 2 . Basic values of the interface gap at the mesial, distal, buccal and palatal points of the implant crowns obtained from polyether material (Group II)

Sample no.	Buccal (µm)	Palatal (µm)	Sample no.	Mesial (µm)	Distal (µm)
1	13.45	36.33	1	10.34	06.27
2	15.32	47.92	2	10.38	09.37
3	16.49	93.81	3	11.38	08.33
4	20.83	83.94	4	12.46	10.42
5	18.77	19.72	5	08.30	07.27
6	00.00	19.22	6	38.41	01.03
7	00.00	32.16	7	06.21	04.17
8	10.42	92.39	8	20.83	18.62
9	45.09	56.43	9	28.93	10.38
10	59.17	97.94	10	05.19	04.15
Mean	19.95	57.90	Mean	15.15	08.00

The mean interface gap at the mesial and distal points of the implant crowns obtained from polyether material were 15.15 μm and 8 μm respectively. The mean proximal gap at the buccal and palatal points of the implant crowns obtained from polyether material were 19.95 μm and 57.9 μm respectively.

On comparison of the mean interface gap at the mesial point, the implant crowns obtained from polyether material showed lesser values than those from vinylpolysiloxane material without any statistical significance. On comparison of the mean interface gap at the distal point, the implant crowns obtained from vinylpolysiloxane material showed lesser values than those from polyether material without any statistical significance. The lesser interface gap at the distal point associated with vinylpolysiloxane could be attributed to its excellent dimensional stability than polyether (Table 3, 4).

Table 3 . Comparative evaluation of the mean interface gap at the mesial, distal, buccal and palatal points of the implant crowns obtained from vinylpolysiloxane material (Group I) using Mann - Whitney test

Group I		Mean (µm)	Standard deviation	P-value	Group II		Mean (µm)	Standard deviation	P-value
	Mesial	20.72	24.07	0.009*		Mesial	15.15	10.71	0.048*
	Distal	04.90	02.60			Distal	08.00	04.81

*P<0.05, statistically significant.

Mann-Whitney test shows the P-value is 0.009. Since the P-value is less than 0.05, there is statistically significant difference between the interface gap at mesial and distal points. The interface gap at themesial point was higher than the distal point with statistically significant difference for Group I. Mann-Whitney test shows the P-value is 0.002. Since the P-value is less than 0.05, there is statistically significant difference between the proximal gap at buccal and palatal points. The proximal gap at the palatal point was higher than the buccal point with statistically significant difference for Group I.

Table 4 . Comparative evaluation of the mean interface gap at the mesial, distal, buccal and palatal points of the implant crowns obtained from polyether material (Group II) using Mann-Whitney test

Group I		Mean (µm)	Standard deviation	P-value	Group II		Mean (µm)	Standard deviation	P-value
	Buccal	26.43	25.27	0.002*		Buccal	19.95	18.66	0.005*
	Palatal	72.49	36.09			Palatal	57.90	31.44

*P<0.05, statistically significant.

Mann-Whitney test shows the P-value is 0.048. Since the P-value is less than 0.05, there is statistically significant difference between the interface gap at mesial and distal points. The interface gap at the mesial point was higher than the distal point with statistically significant difference for Group II. Mann-Whitney test shows the P-value is 0.005. Since the P-value is less than 0.05, there is statistically significant difference between the proximal gap at buccal and palatal points. The proximal gap at the palatal point was higher than the buccal point with statistically significant difference for Group II.

On comparison of the mean proximal gap at the buccal and the palatal points of the implant crowns obtained from vinylpolysiloxane and polyether materials, the proximal gap at the buccal and palatal points of the vinylpolysiloxane group was higher than polyether group without any statistical significance (Table 5, 6). P<0.05 was considered significant.

Table 5 . Comparative evaluation of the mean interface gap at the mesial and distal point of the implant crowns obtained from vinylpolysiloxane (Group I) and polyether (Group II) materials using Mann-Whitney test

Group	Mesial		P-value	Group	Distal		P-value
	Mean (µm)	Standard deviation			Mean (µm)	Standard deviation
I	20.72	24.07	1.000	I	04.90	02.60	0.112
II	15.15	10.71		II	08.00	04.81

Mann-Whitney test shows the P-value is 1.00. Since the P-value is greater than 0.05, there is no statistically significant difference between Group I and Group II at the mesial point. The interface gap at the mesial point of Group I was higher than Group II without any statistical significance. Mann-Whitney test shows the P-value is 0.112. Since the P-value is greater than 0.05, there is no statistically significant difference between Group I and Group II at the distal point. The interface gap at the distal point of Group II was higher than Group I without any statistical significance.

Table 6 . Comparative evaluation of the mean proximal gap at the buccal and palatal point of the implant crowns obtained from vinylpolysiloxane (Group I) and polyether (Group II) materials using Mann-Whitney test

Group	Buccal		P-value	Group	Palatal		P-value
	Mean (µm)	Standard deviation			Mean (µm)	Standard deviation
I	26.43	25.27	0.472	I	72.49	36.09	0.273
II	19.95	18.66		II	57.90	31.44

Mann-Whitney test shows the P-value is 0.472. Since the P-value is greater than 0.05, there is no statistically significant difference between Group I and Group II at the buccal point. The interface gap at the buccal point of Group I was higher than Group II without any statistical significance. Mann-Whitney test shows the P-value is 0.273. Since the P-value is greater than 0.05, there is no statistically significant difference between Group I and Group II at the palatal point. The interface gap at the palatal point of Group I was higher than Group II without any statistical significance.

Elastic deformation may result from non-parallel implants while retrieving the tray from the mouth. The open tray implant level impression technique has been used for single as well as multiple implant situation. The open tray technique allows for the impression coping to remain within the impression after retrieval of the set impression^3,32,46). This reduces the effect of the implant angulation, the deformation of the impression material upon removal of the set impression. Various methods have been suggested by several authors such as splinting, and modification of impression copings to reduce the rotational tendency of the 60 impression coping during the implant replica connection^18,35,37). However, splinting of impression copings is not possible in single implant or randomly distributed single implants in a partially edentulous arch. But during fastening of the analog to the impression coping, there are chances of rotation of the coping within the impression thereby causing a rotational distortion^4,18,30,36). The rotation of impression copings with such open tray impression will likely influence the passive fit of abutment/prosthesis, contact points with the adjacent teeth and occlusion⁸⁾. The resistance to the rotation of the impression coping can be achieved by selecting a rigid elastomeric impression material. The rotational resistance of different elastomeric impression materials was studied by Wee²¹⁾ and he concluded that condensation silicone, polysulfide, hydrocolloids and plaster did not show greater accuracy compared to either vinylpolysiloxane or polyether. The purpose of this study was to comparatively evaluate the accuracy of different elastomeric impression materials with open tray implant level impression technique in single -tooth replacement.

After retrieval of the set impressions, the implant replica was connected to the open tray impression coping within the impression by hand tightening^{4,21,27,30,47-49)}. There is no consensus reported in the literature for the amount of torque to be given while connecting the implant replica to the impression coping^2,27). Many studies have compared the accuracy of implant impressions in single-tooth implant replacement by comparing the three-dimensional orientation of the implant replica in the working cast using reference points^8,30,44,50). The accuracy of the impressions can be clinically correlated only by evaluating the fit of the implant crowns/frameworks intraorally^1,32). An error in the impression may present as occlusal and/or interproximal contacts different from those achieved by the technician on the working cast⁸⁾. It may also lead to the mechanical complications of screw loosening, screw fracture and implant fracture; biological complications of unfavourable soft tissue, hard tissue reactions due to plaque accumulation at the interface⁷⁾. Hence, it was decided to fabricate the implant crowns on the working casts to evaluate the accuracy of the implant impressions.

Many studies reported that CNC milled crowns exhibited better fit than cast gold⁵¹⁾, silver palladium1 and Co-Cr frameworks. This milling system has a machining accuracy of 7 µm which is within the clinically acceptable range of 10 µm∼30 µm^2,4,52,53). All the milled implant crowns were evaluated for the uniform proximal contact on the rectangular area on its respective working cast using 8 µm thickness articulating foil.

The implant crowns were connected to the implant replica of the reference model with 35 Ncm torque as per the manufacturers’ recommendation. The 35 Ncm torque value was selected to achieve the preload for the abutment screw to simulate the intraoral condition. Scanning Electron Microscope was used in this study to measure the interface gap and the proximal gap. Nikon Measuroscope, Optical Microscope⁵⁴⁾, Scanning Laser Microscope⁵⁵⁾ were used in other studies to measure the interface gap with a magnification range of 10X to 40X. The Scanning Electron Microscope used in this study has the magnification of 3,00,000 X and 0.01 µm accuracy.

Daoudi et al.³⁰⁾ investigated the accuracy of two different impression techniques with two different impression materials in single-tooth implant replacement. There was axial rotation and a change in axial inclination of the replica with the open tray impression technique. The amount of rotational error and change in axial inclination was higher in vinylpolysiloxane than polyether material without any statistical significance. Daoudi et al.⁴³⁾ in another study compared three implant level impression techniques in single implant situation using vinylpolysiloxane impression material. The results showed significant differences in implant replica position with closed tray and open tray impression technique in rotational axis. Vigolo et al.⁴⁴⁾ evaluated the accuracy of master cast obtained using modified and unmodified open tray impression copings for single tooth replacement using polyether material. The results showed that there was a significant rotational discrepancy with unmodified open tray impression copings. The results of the above studies were in agreement with the results of the current study. However, direct comparisons of the results of this present study cannot be made due to the differences in the methodology. The interface gap at the mesial and the distal points were within the clinically acceptable range of 30 µm⁵⁶⁾.

Within limitations of the present study, the interface gap observed at the mesial point was higher than that observed at the distal point with statistical significance for both Groups I and II. The proximal gap observed at the palatal point was higher than that observed at the buccal point with statistical significance for both Groups I and II. On comparison between the groups, the interface gap at the mesial point and the proximal gap at the buccal and palatal points of the implant crowns obtained from polyether impression material were lesser than that observed with vinylpolysiloxane group but without any statistical significance. However, the interface gap observed at the distal point was higher with polyether group compared to vinylpolysiloxane group without any statistical significance. The interface gap for the implant crowns obtained from vinylpolysiloxane and polyether materials were within the clinically acceptable range of 10 µm to 30 µm^4,56-58). The higher value at the mesial point could be attributed to the premature contact of the proximal aspect of the implant crown preventing its complete seating at the interface. It indicates rotation and /or axial inclination of the impression coping. The lower values associated with polyether may be due to its higher rigidity and minimal positional distortion. The reduction in the interface gap at the mesial point of the polyether group could be attributed to lesser rotation of impression coping resulting in proper seating of the restoration at the interface.

The study has not explored the influence of saliva, bulk of impression material, the depth of implant placement, the design of impression copings, machining tolerance of individual components, strain on the interproximal surface, strain on the abutment screw and tolerance of the bone and the periodontal ligament. Future research on the accuracy of implant level impression technique with various impression materials can be done keeping in mind of the above stated factors.

Both Polyether and Vinylpolysiloxane can be used in clinical conditions for making open tray implant level impressions for single tooth replacements because interface gaps observed at four different areas between two groups were insignificant.