Journal of Dental Implant Research 2022; 41(2): 25-35  https://doi.org/10.54527/jdir.2022.41.2.25
Evaluation of machining tolerance and vertical microgaps of biohpp peek and cadcam milled zirconia abutments over titanium implants
Praveen Sundar, Hariharan Ramakrishnan , Jayakrishnakumar Sampathkumar , Nagarasampatti Sivaprakasam Azhagarasan
Ragas Dental College & Hospital, Chennai, India
Correspondence to: Hariharan Ramakrishnan, https://orcid.org/0000-0003-4466-5744
Ragas Dental College & Hospital, 2/102, East Coast Road, Uthandi, Chennai 600119, Tamilnadu, India. Tel: +04424530006, Fax: +04452123995, E-mail: abcv2005@yahoo.com
Received: March 30, 2022; Revised: May 20, 2022; Accepted: June 16, 2022; Published online: June 30, 2022.
© The Korean Academy of Implant Dentistry. All rights reserved.

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose: To compare the machining tolerance and vertical microgap at two different implant–abutment interfaces.
Materials and Methods: Twenty-four titanium implants (Bioline, Israel) with an internal hex were divided into two groups, A (Bio-HPP PEEK abutment, Norris, Israel) and B (CADCAM milled zirconia abutments, Dentgallop, USA), and embedded in clear auto polymerizing resin and tightened to a torque of 35Ncm. The machining tolerance was then evaluated using a coordinate measuring machine (GMT Grano7-10-6, India) and vertical microgap at the implant abutment interface using a scanning electron microscope (JEOL 6000 PLUS, Japan) at six regions (front right, front centre, front back, back right, back centre, and back left). Data obtained were tabulated and statistically analyzed using an independent t-test.
Results: Mean machining tolerances at the implant–abutment interface of the group A and B samples were 126.75 μm and 536.33 μm, respectively, on the x-axis. An independent t-test showed a significant difference in the machining tolerance and vertical microgaps between the two groups in four regions. The microgaps values of four zones of the Group A samples were significantly less than the Group B samples. The front centre zones of the Group A samples had the least vertical microgap compared to the six zones of the Group B samples. The front right zones of the Group A samples had the highest vertical microgaps that were still less than the vertical microgaps of the Group A samples in all six zones (P<0.05).
Conclusions: Bio-HPP PEEK abutment-titanium implant interfaces showed a significantly lower machining tolerance and vertical microgaps than the titanium implant-CADCAM Milled zirconia abutment interfaces.
Keywords: PEEK, Zirconium oxide, Dental implant-abutment, SEM
INTRODUCTION

The importance of passive coordination between the supra-structural framework and transmucosal abutment of the implant prosthesis carries great clinical application. Spector et al.1) evaluated three different impression methods to reproduce the position of the implant in the master model. They found that the transfer abutment replica distortion ranged from 20 to 180 µm. Various implant components are used in both the clinical and experimental stages of all processes involved in the manufacture of implant frameworks.

All implant components are machined to fit perfectly, but there is always a unique machining tolerance between the mating surfaces. Machining tolerance is the difference in a stationary position (horizontal displacement) between components when the components are held in place by their respective mounting screws2,3). Two factors that contribute to machining tolerances are dimensional variation and surface roughness. Dimensional tolerances indicate how much a machined component can deviate from its "exact dimensions". The surface roughness of the machined part affects the fit of the contact surface2,3).

Partially and completely edentulous prosthetic rehabilitation with dental implants had evolved into the routine procedure of restorative dentistry with a success rate of over 90%4,5). This is mainly due to the well predictable nature of osseointegration. traditional Branemark’s protocol uses a two-step process in which the abutment and the prosthetic external hex connection (restoration) are performed after the implant fixation has been integrated for a while5-7). Internal hexagonal connections have become more important to overcome the mechanical problems of external hexagonal connections. Its reduced vertical platform distributes the load within the vertical axis of the implant and withstands the joint opening5-7). Connection shape between the implant and the abutment has been changed several times from the traditional 0.7 mm high Branemark’s external connection structure, spline implants, to an internal, conical, hexagonal, and octagonal connection8).

Most abutments fail in the contiguous region and the screws used to clamp the implant and abutment must provide a stable joint. This is achieved by properly tightening the prosthesis screws that create the preload4,9). Preload or clamping force is determined by the torque meter according to the manufacturer's recommendation (Ncm). This clamping force must be maintained and exceed the joint separation force. This is usually caused by occlusal overload5-12). Applying controlled torque with different screw designs has significantly reduced mechanical complexity but has not eliminated it. Another important clinical area of connection geometry is the presence of microgap at the implant-abutment interface between the mating parts.

Binon6) reported on the importance of fitting accuracy between implant components. This is because incompatibility between these two interfaces leads to frequent screw loosening, irreversible screw fractures, and osseointegration destruction. Misalignment of the implant-abutment interface causes overload and does not disperse the axial load, resulting in a passive fit between the prosthesis and abutment, peri-implantitis and mucositis, bone loss, and "micro Pump effect"9,12,13).

The size of the microgap increases during loading conditions because the number of microorganisms increases under loading rather than unloaded conditions. Various studies have assessed the size of the microgap at the implant-abutment interface, averaging about 50 µm microgap. Rismanchian et al.14) reported for a 7∼74 µm microgap. Piattelli et al.15), the microgap size is estimated to be 2∼7 µm for screw abutments and 7 µm for cement abutments. Stock abutments have fewer mechanical complications than cast-on individual abutments, as the stock abutments are precisely milled and found likely to fit accurately with their corresponding fixture.

Microgap can be measured in implants using a variety of techniques Abutment Interface, Probing by Dental Explorer10), Periotest device10), direct X-ray observation4), electron scanning Microscope (SEM)5,14,16-18), Scanning Laser Microscope (SLM)12), Optical Microscope (O.M.)17), 3D Microtomography Technology4,19), Optics Coherence tomography10). Among these methods of analyzing the microgap of implant abutments Scanning electron microscope (SEM) is a well-documented method. This type of analysis proves to be highly validated.

Machining tolerance is the horizontal misfit of the implant and the abutment and vertical microgap is the gap between the implant-abutment junction. The null hypothesis adopted for this study was that there would be no differences in values of machining tolerance and vertical microgap between Premachined bio-HPP PEEK abutment and CADCAM milled Zirconia abutment.

MATERIALS AND METHODS

A 20 mm×20 mm×20 mm cube made of stainless steel created by milling the large metal block (Neema industries, India) which is used as an index for the fabrication of similar-sized acrylic blocks used in this study.

High Viscosity Condensed Polysiloxane Impression Material Made of Putty and Indurent Gel – catalyst - Zetaplus (Zhermack., Italy) is used to get the index of the stainless steel die. Take the required amount of condensed polysiloxane (base), take the appropriate amount of Indurent gel (catalyst) according to the manufacturer's instructions, and repeatedly fold the material with your fingertips to obtain an uniform dough. The mixed condensed polysiloxane base and curable gel (catalyst) were placed over the stainless steel die, a metal holder is used to hold the polysiloxane material and allowed to stand until set. After setting, the stainless steel was removed from the index. After setting, the stainless steel die was removed from the index and examined for defects. The putty index thus obtained was used to prepare specimens of standardized dimensions for this study.

The silicone mold was positioned in the dental surveyor (Bego, Germany) as the base was parallel to the floor. The survey platform was positioned parallel to the ground using a spirit level indicator (Jinhua Hengda Tools, China). A cover screw (BIOLINE Dental Implant System Ltd., Israel) was attached to the implant with a hand hex driver (NORIS Dental Implant System Ltd., Israel). With the help of a straight mandrel, an implant with a cover screw was attached to the vertical axis of the surveyor's arm. The surveying arm was adjusted so that the implant was placed in the center of the silicone mold and the implant abutment platform was placed 3 mm above the surface of the silicone mold.

After positioning the implant, the space around the implant was filled with clear auto polymerized acrylic resin (DPI, India). The silicone mold was filled so that the implant abutment platform was 3 mm above the surface of the resin block.

The resin was allowed to polymerize and the resin block was removed from the silicone mold. 24 clear acrylic blocks were made, each stabilizing one implant.

In this present study, we used twelve, HPP PEEK, internal hexagon abutments (NORIS Dental Implant System Ltd., Israel), and twelve CADCAM milled Zirconia abutments (Dentgallop, USA). Based on abutments used the samples which are embedded and numbered were assigned to two test groups.

Group I test samples are comprised of Bio-HPP PEEK abutments were connected to their respective implants and were labeled as SA 1 to SA 12 (n=12) (Fig. 1).

Figure 1. Group A test samples comprised of Bio-HPP PEEK abutments connected to their respective implants and labeled as SA 1 to SA 12.

Group II test samples comprised of CADCAM milled zirconia abutments were connected to their respective implants and were labeled as SB 1 to SB 12 (n=12) (Fig. 2).

Figure 2. Group B test samples comprised of CADCAM milled zirconia abutments connected to their respective implants and labeled as SB 1 to SB 12.

All implants are evaluated before connecting using a coordinate measuring machine (CMM) (GMT Guindy Grano7-10-6, India) which is capable of measuring in x, y, and z-axis (x- horizontal axis, y- horizontal axis, and z –vertical axis) and z angulation with an accuracy of ±10 the CMM was connected to a data processer that gives the measured value, the probe used in CMM was first calibrated. Then the abutment is placed over its respective implant and torque of up to 35 Ncm based on manufacturer instruction. An implant was placed in the holder on the CMM working table. Under machine control, the x, y coordinates of 20 equally spaced points around the cylindrical section of the implant were measured. CMM computed the centers of the implant (Fig. 3). A torque wrench was used to attach an abutment to an implant with the abutment screw to 35 Ncm. The abutment was connected to the implants. Before the abutment was tiglıtened, the abutment was displaced by hand in the x-direction to a position. An abutment was tiglıtened to 35 Ncm. Under machine control, the x, y coordinates of 20 equally spaced points around the cylindrical section of the abutment were measured (Fig. 4). The CMM computed the centers of the implant (A) and abutment (B). From the computed centers of A and B, Y1 (Distance between A and B) was computed. The abutment was loosened and the abutment was displaced in the y-direction to the position. Similarly, Y2 was computed from the two computed centers A and C. This allowed computation of the y-direction tolerance (Y1, + Y2). The x-direction tolerance (X1+x2) was computed in an identical way.

Figure 3. Under machining tolerance, centre of the implant was identified.

Figure 4. Diagramatic representation of axis involved in machining tolerance.

The clogging debris might interfere with accurate visualization of the implant-abutment interface was removed by subjecting the test sample to copious rinsing with distilled water and ethyl alcohol. After that 10 minutes of ultrasonic bath, cleaning is done in Digital Ultrasonic cleaner (Beijing Ultrasonic Co., China) and dried with the hairdryer (PHILIPS, Dutch). To prevent further contamination until the Scanning electron microscope analysis the samples were preserved in an air-tight container. Since SEM uses electrons and creates higher magnification and resolution images, to get more electro-conductive gold-sputtered using Gold Sputtering Machine (JOEL Smart Coater, Japan) used before the SEM procedure under SEM the implant-abutment interface of each test sample was evaluated at 10 kV acceleration voltages. Different magnifications are used from suitable lower magnification to higher magnification to obtain the proper image of the implant-abutment interface to get the accurate measurement of the microgap. Individually each test sample was evaluated at six surfaces. Initially, all implant abutment samples were placed in SEM source (JOEL JCM-6000 plus, Tokyo, Japan), the vertical reference line is marked in the outer surface of the abutment facing the reader, the microgap was measured at 3 points (left edge, center, right edge) with the help of digital images SEM device software and analyzer. Then rotate the sample 180 degrees and the same 3 measurement points (left edge, center, right edge) as the other vertical reference lines were recorded all samples are evaluated under 300x magnification. An image measuring pixel counting software is used to obtain the image of each test sample (Fig. 5, 6). In this software, the SEM images were installed into the software file. The known distance, pixel, unit of the specific SEM images was transferred to the measuring scale of the software. The microgaps were measured with the linear measuring scale of the software.

Figure 5. SEM image of front right region of Implant-HPP PEEK abutment interface.

Figure 6. SEM image of back centre region of implant-CADCAM milled zirconia abutment interface.
RESULTS

The basic and mean data of each test group for machining tolerances are provided in tables (Table 1A2B) and statistically analyzed using independent t-test (Table 3). The basic and mean data of each test group for microgaps are provided in (Tables 47), and statistically analyzed using independent’t’ test (Table 8).

Table 1 A. Comparative evaluation of the Machining tolerance of Group A samples

Sample No.X (µm)Y (µm)


X1X2X1+X2Y1Y2Y1+Y2
SA1826214411383196
SA23922617382155
SA352841368085165
SA466571237877155
SA54738859252144
SA63751887986165
SA785681535177128
SA84290132112127239
SA992621547255127
SA10837615910797204
SA1163841474768115
SA126574139153153306


Table 1B. Mean levels of Machining tolerance among Group A samples

Machining tolerancenMeanSDMinimumMaximum
X1+X212126.750031.6576161.00159.00
Y1+Y212174.916754.45007115.00306.00

Inference: Table 1A, 1B indicates the mean machining tolerance of X1+X2 and Y1+Y2 for a sample size of 12, with minimum and maximum values in Group A samples.



Table 2A. Comparative evaluation of the Machining tolerance Group B samples

Sample No.X (µm)Y (µm)


X1X2X1+X2Y1Y2Y1+Y2
SB132611444087107195
SB2357217574243155
SB331527458914242184
SB442122164284164248
SB53877846380167247
SB632131163214376219
SB715032447418781268
SB824839764527111138
SB9247132379167274441
SB10414264678117186303
SB11280262542701181
SB12294843784768115


Table 2B. Mean levels of Machining tolerance among Group B

Machining tolerancenMeanSDMinimumMaximum
X1+X212536.3333106.50935378.00678.00
Y1+Y212207.8333106.1678255.00441.00

Inference: Table 2A, 2B indicates the mean machining tolerance of X1+X2 and Y1+Y2 for a sample size of 12, with minimum and maximum values in Group B samples.



Table 3. Mean comparison of Machining tolerance between Group A and Group B using independent t-test

Machining toleranceGroup AGroup BP-value


MeanSDMeanSD
X1+X2126.750031.65761536.3333106.509350.000*
Y1+Y2174.916754.45007207.8333106.167820.350

*P<0.05 considered statistically significant.

Inference: Table 3 represents the mean difference between Group A and Group B samples in x-axis shows a significant difference between the machining tolerance with higher difference between them in which mean value of Group A is lesser than that of mean value of Group B. In y-axis Group A and Group B shows no significant difference between the groups in the machining tolerance.



Table 4. Comparative evaluation of the Vertical Microgap of Group A samples using SEM under 300× magnification

Sample no.Front right (µm)Front centre (µm)Front left (µm)Back right (µm)Back centre (µm)Back left (µm)Average (µm)
SA19.445.329.598.218.2210.548.553
SA28.256.755.367.818.456.717.222
SA37.235.656.127.346.677.236.707
SA47.436.727.788.739.9310.128.452
SA58.859.2510.017.256.128.328.300
SA66.234.895.736.565.527.366.048
SA79.218.379.167.257.266.007.875
SA88.245.336.146.866.116.896.595
SA97.757.216.297.959.247.367.633
SA106.197.288.676.469.416.177.363
SA116.967.895.587.806.787.807.135
SA129.026.897.115.765.678.557.167

Inference: Table 4 shows the minimum and maximum vertical microgap values in various zones. Front right with minimum value 6.19 µm and maximum value 9.44 µm. Front centre with minimum value 4.89 µm and maximum value 9.25 µm. Front left with minimum value 5.36 µm and maximum value 10.01 µm. Back right with minimum value 5.76 µm and maximum value 8.73 µm. Back centre with minimum value 5.52 µm and maximum value 9.93 µm. Back left with minimum value 6.00 µm and maximum value 10.54 µm. Total average with minimum value 6.05 µm and maximum value 8.55 µm.



Table 5. Mean levels of Vertical Microgap among Group A

Vertical MicrogapnMeanSDMinimumMaximum
Front right127.88501.133776.199.44
Front centre126.79581.327774.899.25
Front left127.41001.599665.3610.01
Back right127.3317.832225.768.73
Back centre127.34831.631075.529.93
Back left127.75421.424556.0010.54
Total average127.4208.776626.058.55

Inference: Table 5 represents the mean and SD levels of vertical microgap among Group A in various regions representing the mean values for individual regions with minimum and maximum values. Average value for all the region also given.



Table 6. Comparative evaluation of the Vertical Microgap of Group B samples using SEM under 300× magnification

Sample no.Front right (µm)Front centre (µm)Front left (µm)Back right (µm)Back centre (µm)Back Left (µm)Average (µm)
SB110.6511.259.357.3211.259.369.863
SB27.636.345.496.137.166.286.505
SB313.2611.4210.3613.6914.2310.6912.275
SB46.326.178.169.326.146.327.072
SB59.325.218.649.347.119.328.156
SB610.879.3212.658.327.429.369.657
SB76.118.369.3116.2411.5611.3610.490
SB810.3610.2611.369.148.369.249.787
SB98.367.219.3310.6910.476.478.755
SB1010.256.479.357.356.127.367.817
SB1110.1913.029.037.478.818.899.530
SB129.668.3011.096.888.817.038.628

Inference: Table 6 shows the minimum and maximum vertical microgap values in various zones. Front right with minimum value 6.11 µm and maximum value 13.26 µm. Front centre with minimum value 5.21 µm and maximum value 13.02 µm. Front left with minimum value 5.49 µm and maximum value 12.65 µm. Back right with minimum value 6.13 µm and maximum value 16.24 µm. Back centre with minimum value 6.12 µm and maximum value 14.23 µm. Back left with minimum value 6.28 µm and maximum value 11.36 µm. Total average with minimum value 6.51 µm and maximum value 12.28 µm.



Table 7. Mean levels of Vertical Microgap among Group B

Vertical MicrogapnMeanSDMinimumMaximum
Front right129.41002.031526.1113.26
Front centre128.61082.466235.2113.02
Front left129.51421.797705.4912.65
Back Right129.32002.977396.1316.24
Back centre128.96832.477026.1214.23
Back left128.44421.729466.2811.36
Total average129.04461.573966.5112.28

Inference: Table 7 represents the mean and SD levels of vertical microgap among Group B in various regions representing the mean values for individual regions with minimum and maximum values. Total average value for all the region also given.



Table 8. Mean comparison of Vertical Microgap between Group A and Group B using independent t-test

Vertical MicrogapGroup AGroup BP-value


MeanSDMeanSD
Front right7.88501.133779.41002.031520.033*
Front centre6.79581.327778.61082.466230.035*
Front left7.41001.599669.51421.797700.006*
Back right7.33170.832229.32002.977390.036*
Back centre7.34831.631078.96832.477020.072
Back left7.75421.424558.44421.729460.298
Total average7.42080.776629.04461.573960.004*

*P<0.05 considered statistically significant.

Inference: Table 8 represents significant difference in mean vertical microgap values for front right, front centre, front left, back right region and total average between Group A and Group B ,in which Group A shows lesser mean vertical microgap values than Group B in right, front centre, front left, back right region and total average was also significant. In other regions mean values between Group A and Group B were insignificant.



T test revealed very less decreased machining tolerance which was significant between samples of both the groups along X horizontal axis, than along Y axis. Out of total of six different zones along implant abutment interfaces of samples of both groups, microgaps values of four zones of Group A was less and significant. Front centre zones of Group A samples had the least vertical microgap compared to six zones of Group B samples and was significant. Front right zones of Group A samples had highest vertical microgap among them ,and was still lesser than vertical microgaps of Group A samples in all of their six zones.

DISCUSSION

The results of this study showed that there is statistically significant difference in the machining tolerance between the BioHPP PEEK abutment group and CADCAM milled zirconia abutment group. BioHPP PEEK abutment group showed smaller tolerance values on comparison with CADCAM milled zirconia abutment group along the x-axis of implant-abutment interface which was highly significant between the groups and insignificant in the y-axis of the implant-abutment interface. In this study, the BioHPP PEEK abutment showed the mean tolerance value of 127 µm along the x-axis and 175 µm along the y-axis, for CADCAM milled zirconia abutment group showed 536 µm along the x-axis and 208 µm along the y-axis.

The abutment when rotated from the initial passive adjustment position, tightening the abutment screw and aligning the abutment with the implant will create stress, regardless of machining tolerances. Thus, while machining tolerances can be beneficial in achieving passive tuning over a wide range of positions, there is a limit to this adaptation to three-way interface relationships between components are mixed. Although the magnitude of the machining tolerance is important, because the larger this value is, the larger the range of passively adjusted positions, and therefore the larger the strain value tolerable, from a practical point of view. In the clinical situation, this range of passive tuning positions can be much more limited. Therefore, these tolerances are not sufficient to provide a passive fit2).

The presence of microgaps can cause mechanical and biological complications such as peri-implantitis, screws loosening, abrasions, wear, potential bone loss and micropump effects. These complications had been verified in several studies5,19-22).

The connection configuration of the Branemark protocol is external with a hexagon that provides anti-rotation support for the superstructure and also simplifies implant insertion23). The main drawback of Branemark’s system is mechanical instability when exposed to off-axis forces. In certain situations, we may need to use a custom abutment such as in patients with reduced interdental space and the restoration of misaligned implants24). Abutments can be customized in a variety of ways, including casting, milling, and laser sintering. Surface irregularities due to the customization process can increase the microgap at the interface between the implant and the abutment. Zirconia abutment can be used when bluish titanium halos through thin soft tissues and is a major esthetic concern25). The main disadvantage of the CAD/CAM milled zirconia abutment is its poor marginal fit26).

Many studies have reported the importance of implant and abutment compatibility5,14,16-18,27-30). However, a standardized method for measuring the interface between implants and abutments is not yet established18). Measurement of microgap at the interface between the implant and abutment using the scanning electron microscope (SEM) is a well-documented method and has proven to be efficient5,14,16-18,27,28). Followed by SEM, 3D Microtomography Technology had been used4,29,30). In this study, we have used SEM to evaluate the microgap.

Results of this study showed that there is statistically significant vertical microgap between the Bio-HPP PEEK abutment and CADCAM milled zirconia abutment. Bio-HPP PEEK abutments showed smaller vertical microgap values on comparing with CADCAM milled zirconia abutments. The vertical microgap between Bio-HPP PEEK abutment and titanium implant ranges from 6.7 to 7.8 µm whereas the vertical microgap between CADCAM milled zirconia abutment and titanium implant ranges from 8.4 to 9.5µm. This could be due to the fact reported in a previous study where minimal microgap values and misfit values in prefabricated abutments than in castable abutments22).

In this study, we had evaluated vertical microgap in 6 different regions namely front right, front center, front left, back right, back center, and back left, of which front right, front center, front left, back right showed significant differences between the groups. The mean vertical microgap value in front right, front centre, front left, back right region of Group A was found to be lesser than Group B and this difference is significant. In back centre region and back left region this difference is insignificant. This could be due to introduction of human errors by way of premature load during torquing or due to unknown lab errors.

Baldassarri et al.31) reported the mean vertical microgap value of 1.6 µm, 5.7 µm, 8.4 µm, 11.8 µm in CADCAM milled zirconia abutment on using different implant system. Cunha et al.32) reported that vertical microgap values of 5.7 µm, 9.53 µm, 10.62 µm on comparing fit accuracy between CADCAM milled zirconia abutments over three Implant systems. In our study, the mean microgap value of 12.28 µm for CADCAM milled zirconia abutments group is in close similarity to these two studies.

In a study by Rismanchian et al.14), the value of vertical microgap was given as 7 to 74 µm depending on the type of abutment. Fernández et al.9) reported vertical microgap is range from 0.73 to 11.30 µm depending on the type of abutment. Tsuge et al.33) report average microgap from 3.2 to 5.6 µm. In the study by Scarano et al.34) vertical microgaps for the screw type abutment was 60 µm and the cement type abutment was 40 µm. Piattelli et al.15) reported 27 µm microgap for screw type and 7 µm microgap for cement type prosthesis. In a study by Jansen et al.35), the amount of microgap was 10 µm for all implants tested. Bajoghli et al.12) evaluated the vertical microgap and it varied from 2 to 25 µm in conical connection in three Different Implant Systems. Filho et al.36) reported the vertical microgap value with a range of 1 to 28 µm by using different manufacturer abutments. In this study, the mean microgap in the Bio-HPP PEEK abutment group is 7.42 µm, and the mean microgap in the CADCAM milled zirconia abutment group is 9.04 µm and these two different values fall within the range of vertical microgap values of the previous studies9,12,14,15,35).

The present test results of vertical microgap of Group A samples couldn't be compared with previous studies of similar nature due to the non-availability in various scientific databases.

Machining tolerance is also known as horizontal misfit between machined implant components, similarly vertical microgap is also known as vertical misfit between the machined implant components. From the test results of the current study, it gives an impression that Group A implant components interface with the least machining tolerance values in the x-axis, also showed the least vertical microgap values on comparing with Group B samples, and both of these values of machining tolerance and vertical microgap were statistically significant on comparing with Group B. The null hypothesis was rejected since there were significant differences in machining tolerance values and vertical microgap values between the two groups.

The present study had some limitations, the microgap was measured around the outer perimeter of the implant-abutment interface and no information about inner regions was provided. However, this approach has been used in previous investigations, therefore justifying the methodology utilized. In machining tolerance measurements we have only measured 2-dimensional distortion and 3-dimensional measurement will provide more information. CADCAM milled Bio-HPP PEEK abutments could be in future studies. Artificial saliva was not used in this study to simulate the clinical situation. Future could include the same.

CONCLUSION

Bio-HPP PEEK Abutment- Titanium implant interfaces showed significantly decreased machining tolerance value and vertical microgaps than that of Titanium implant-CADCAM Milled zirconia abutment interfaces.

CLINICAL SIGNIFICANCE

Regular Clinical use of Bio HPP Peek abutments is recommended over titanium implants.

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