Radiographic and Clinical Evaluation of Implant Prosthetic Treatment with One Piece versus Two Piece Dental Implants: A Comparative Prospective Study

ABSTRACT

Dental implants are designed to ensure natural tooth replacement based on improved design, simplified placement, and long-term survival. This study aimed to compare one-piece implant (OPI) and two-piece implant (TPI) to determine the success rate over the TPI. This study conducted on 15 patients selected with the age range of 20–60 years to place OPI and TPI. The surgical consent form duly signed by the patients was procured. The implants used were of Adin Implant System, and a follow-up examination was done at 3, 6, and 9 months after implant loading and various clinical and radiographic parameters were noted for both OPI and TPI. The clinical parameters measured were Silness, and Loe gingival index and probing depth and the radiographic parameters included crestal marginal bone loss. Independent Sample t-test and ANOVA were used for statistical analysis. The statistical analysis showed no significant difference between the OPI and TPI based on the gingival index, probing depth, and crestal bone loss. On the contrary, there was a statistical significance in comparing the same parameters during the follow-up period of 3, 6, and 9 months. Over a protracted period, OPIs are better than TPIs by the design and placement procedure. Further research with a higher sample size shall possibly establish esoteric results on a large scale.

INTRODUCTION

Dental implant treatment has turned over a new leaf in the field of dentistry. Replacement of the natural tooth by dental implants has become threadbare in contemporary dental surgery practice. With osseointegrations as the established scientific procedure, the great impetus in implantology is intended to simplify the surgical protocol, improve the design, immediate positioning, and loading of the implants to alleviate the duration of the implant restoration.[1]

After raising a soft tissue flap, which is then moved to cover the implant during healing, the traditional two-piece implant (TPI) is positioned in the bone. Subsequently, a transmucosal abutment is placed to enable the prosthesis to be connected. However, this complicated technique to replace the healing abutment with a final abutment causes more harm to the repaired or healing gingiva. In addition, localized inflammation of the soft tissue surrounding the implant can also result from microleakage and micromovement of the abutment.

The one-piece implant (OPI) is advantageous to overcome the drawback since it provides a seamless shift from the root analog to the crown analog.[2] OPI design is beneficial in terms of eliminating structural weakness (micro gap) and is also recommended to replace one or more teeth or to act as an abutment for a full or partial denture. Strong unibody design, no split parts, single-stage surgery with either a flap or flapless approach, and a straightforward restorative technique are just a few of its many benefits.[3] Additionally, a OPI eliminates the need for numerous surgical and prosthetic components, which reduces the overall cost.[1] OPI also shows reduced marginal bone loss as with a sequel of low bacterial infection.[3]

As the implant abutment angulation cannot be changed, there were significant failures in OPIs. Since then, a detailed cognizance of the site requirements and placement procedures has brought variations from the early designs with angulated abutments and surface-treated implants.[1] Concurrently, advances in science and technology led to a quantum jump in surface treatments and implant threading patterns that have been shown to promote primary stability and accelerate healing.

This study aimed to compare OPI and TPI by evaluating the clinical parameters using Loe and Silness gingival index, the probing pocket depth, and the radiographic parameter of marginal bone loss at the implanted site.

MATERIALS AND METHODOLOGY

The present study was conducted in the outpatient Department of Prosthodontics and Implantology.

Ethical considerations

The participants were explained the objectives and impact of the study. Informed consent in English and regional language was obtained from patients, and the nature of treatment and the associated risks were explained, respectively.

The patient selection’s pretreatment clinical and radiographic examination was performed, including a thorough medical and dental history, and current general and oral health status. Fifteen patients within the age range of 20–60 years were selected and given OPI and TPI bilaterally in the arch.

Inclusion criteria

1. Age group: 20–60 years old with an unequal ratio of men and women.

2. Partially edentulous patients indicated replacement with an implant.

3. The existing bone for implant placement should have sufficient volume and quality for an implant of at least 10 mm in height and 4 mm in width.

4. Good oral hygiene

5. Adequate mouth opening

6. The subjects who have agreed to participate in the study with informed consent.

Exclusion criteria

1. Subjects having any medical contraindications to implant therapy or physical reasons that could affect the follow-up

2. Insufficient bone quality

3. Inadequate mouth opening

4. Heavy smokers

5. Chronic alcoholic

6. Presence of vital anatomical structures close to the implant site

7. Patient under immunosuppressive therapy or radiotherapy

8. Psychiatric problems

9. Disorders to the implant site related to a history of radiation therapy to the head and neck, or bone augmentation.

The patients were pre-medicated with suitable antibiotics and analgesics from a day before the proposed surgery. The patients were advised to use chlorhexidine mouthwash 2–3 times daily, 3 days before surgery. Intraoral and extraoral scrubbing with povidone-iodine (CIPLADINE) solution was performed. The surgical area was anesthetized using an inferior alveolar nerve block with 2% lignocaine in a 1:1,00,000 concentration of adrenaline.

The implant placement site for both OPI and TPI was in the mandibular posterior region. The drilling procedure was done using the initial pilot drill of 2 mm diameter through the surgical stent using a gear reduction contra-angled hand piece at a low speed of 800 RPM, minimum pressure, and intermittently to avoid overheating of the bone. The pilot channel was enlarged to 2.5, 3.2, and 3.6 mm for a 3.75 mm diameter implant.

Following the same surgical protocol, TPIs and OPIs were placed for each group of patients. Once the implant was placed in position, the primary stability was checked by readings over the handpiece torque wrench, which was used for screwing the implants. Provisional restoration was cemented with non-eugenol zinc oxide cement and final restoration (metal-ceramic prosthesis) for patients with OPIs was cemented after 3 months with glass ionomer cement.[4]

In patients with TPIs, implant uncovering was performed after 3 months of implant placement. Then, a healing abutment was placed for 3 weeks, after which the implant was loaded with a metal-ceramic prosthesis. The implants used were of Adin Implant System, with dimensions of 3.75 mm diameter and 11.5 mm length were used for two cases and the rest with 4.2 mm and 11.5 mm length for both OPI and TPI.

A follow-up examination was done at 3, 6, and 9 months after implant loading and various clinical and radiographic parameters were noted for both OPI and TPI. The clinical parameters measured were Silness and Loe gingival index and probing depth. The radiographic parameters included crestal marginal bone loss (IOPAR/RVG and OPG). A radiographic examination using the paralleling technique was performed at 3, 6, and 9 months follow-up. Bone levels were measured on each implant’s left and right sides, and a mean value was calculated for each implant. On mesial, distal, lingual, and buccal sites, the probing depth was evaluated using a plastic probe, and the mean probing depth was calculated. Next, the gingival index (Leo and Silness index) was measured at 6 points using the same plastic probe on mesiobuccal, buccal, distobuccal, distolingual, lingual, and mesiolingual, and then the mean values were calculated.

The independent sample t-test was used to compare means between the groups as in OPI and TPI. The overall mean comparison between the variables of the two groups was done using ANOVA. The statistics were performed using SPSS version 20, and the P value was set at 0.05 to be significant.

RESULTS

The study aims to compare the changes in the crestal bone levels radiographically and the gingival index and probing depth clinically in OPI and TPI at 3, 6, and 9 months.

Table 1 shows a mild increase in OPI crestal bone loss compared to TPI at 3 months. But, at 6 months, the crestal bone loss of the TPI was slightly more than OPI distally, whereas, at 9 months, bone loss was slightly higher in the TPI group. On the contrary, the statistical analysis showed the P values were more than 0.05 resulting in no significant difference between the groups. So there was no significant difference in the crestal bone loss when comparing OPI and TPI at 3, 6, and 9 months.

Table 1.

Comparison of crestal bone loss radiographically between one-piece and two-piece implants using the t-test at 3, 6, and 9 months

Side	Variable	Groups	n	Mean	SD	t	P
Mesial	Crestal bone loss 3 months	One piece	15	0.96	0.44	0.213	0.833 NS
		Two piece	15	0.93	0.41
	Crestal bone loss 6 months	One piece	15	1.30	0.49	0.001	0.981 NS
		Two piece	15	1.30	0.31
	Crestal bone loss 9 months	One piece	15	1.53	0.39	0.778	0.443 NS
		Two piece	15	1.63	0.29
Distal	Crestal bone loss 3 months	One Piece	15	1.03	0.39	0.464	0.646 NS
		Two piece	15	1.10	0.38
	Crestal bone loss 6 months	One piece	15	1.40	0.38	0.464	0.646 NS
		Two piece	15	1.46	0.39
	Crestal bone loss 9 months	One piece	15	1.70	0.25	0.357	0.724 NS
		Two piece	15	1.73	0.25

NS, not significant

Table 2 shows a mild increase in the gingival index of the OPI at 9 months and the TPI at 3 months. However, on statistical analysis, the P values were more than 0.05. Hence, there is no significant difference in the gingival index when comparing OPI and TPI at 3, 6, and 9 months.

Table 2.

Comparison of Gingival index clinically between one-piece and two-piece implants using t-test at 3, 6, and 9 months

Variable	Groups	n	Mean	SD	t	P
Gingival index 3 months	One piece	15	0.20	0.11	0.617	0.542 NS
	Two piece	15	0.23	0.17
Gingival index 6 months	One piece	15	0.38	0.13	0.001	0.990 NS
	Two piece	15	0.38	0.19
Gingival index 9 months	One piece	15	0.60	0.17	0.617	0.542 NS
	Two piece	15	0.56	0.18

NS, not significant

Table 3 shows a mild increase in the probing depth of the TPI compared to the OPI at 3, 6, and 9 months. However, statistical analysis showed that the P values were more than 0.05. So there is no significant difference in the probing depth when comparing OPI and TPI at 3, 6, and 9 months.

Table 3.

Comparison of probing depth clinically between one-piece and two-piece implants using t-test at 3, 6, and 9 months

Variable	Groups	n	Mean	SD	t	P
Probing depth 3 months	One piece	15	1.10	0.17	0.674	0.506 NS
	Two piece	15	1.15	0.19
Probing depth 6 months	One piece	15	1.28	0.28	0.835	0.411 NS
	Two piece	15	1.38	0.32
Probing depth 9 months	One piece	15	1.52	0.23	0.842	0.407 NS
	Two piece	15	1.59	0.24

NS, not significant

Table 4 shows a slight increase in the crestal bone loss, gingival index, and probing depth from 3 to 9 months in both the OPI and TPI. However, on statistical analysis, all the three variables of the OPI and TPI showed a P value lesser than 0.05, which depicted that both groups showed significant differences compared to the follow-up of 3, 6, and 9 months.

Table 4.

Comparison of crestal bone loss, gingival index, and probing depth in one-piece and two-piece implants using ANOVA at 3, 6, and 9 months

Variables	Group	n	Mean SD 3 months	Mean SD 6 months	Mean SD 9 months	F	P
CBL mesial	One piece	15	0.96±0.44	1.30±0.49	1.53±0.39	6.10	0.005*
	Two piece	15	0.93±0.41	1.30±0.31	1.60±0.29	15.24	0.000*
CBL distal	One piece	15	1.03±0.39	1.40±0.38	1.7±0.25	13.42	0.000*
	Two piece	15	1.10±0.38	1.46±0.39	1.73±0.25	12.09	0.000*
GI	One piece	15	0.20±0.11	0.38±0.13	0.60±0.17	30.83	0.000*
	Two piece	15	0.23±0.17	0.38±0.19	0.56±0.18	12.31	0.000*
PD	One piece	15	1.10±0.17	1.20±0.28	1.52±0.23	11.51	0.000*
	Two piece	15	1.15±0.19	1.38±0.32	1.59±0.24	10.62	0.000*

*Significant

DISCUSSION

A two-stage surgical approach is recommended by the original Branemark concept of osseointegration. The TPI concept is a pioneer in leading modern dental implantology and is backed up with scientific documentation with a survival rate of 94.6%, according to Fanali et al.[5] However, it is also possible to accomplish and sustain osseointegration with a OPI with improved implant design, evaluation of the factors impacting osseointegration, simplification of surgical procedure, and loading of implants.

These implants have also demonstrated a long-term survival rate. In addition, they are designed to reduce complications compared with TPIs.[6] OPIs do not experience the typical screw-loosening concerns and are fail-resistant against microleakage and micromovements between abutment and fixture.[7] Due to the solid design of these implants, interdental bone and gingival papillae are conserved when they are used in the aesthetic zone at a sufficient distance from adjacent teeth.[3]

On the contrary, the OPI has its disadvantages also. For example, postsurgical corrections are merely possible in these implants. Hence, for a OPI design, bone quality and quantity, intra-occlusal and intermaxillary space, and keratinized gingiva should all be evaluated. According to a clinical evaluation by Hahn, the one-piece system had good stability, aesthetics, and patient satisfaction with a success rate of 96.7% and a shorter treatment duration as postsurgical visits were not necessary.[8]

Mahoorkar et al.[2] discussed the advantages of OPIs over TPIs in the aspects of surgical technique, immediate placement of the implant, and the restorative phase or prosthetic phase. OPI exhibited 100% success rate except where the abutment needs to be angulated for better esthetics and function. According to Kamble et al.,[9] a OPI had a success rate that varied from 93.2% to 100%. In a 10-year follow-up study conducted by Eldibany and Rodriguez,[10] the initial loading in conjunction with one-piece post-extraction implants in the mandible employing atraumatic threaded bone expander demonstrated a 98% success rate.

Bilichodmath et al.[11] assessed the clinical performance of the OPI as an effective treatment strategy for patients with aesthetic concerns. With the immediate loading, the patient experienced little postoperative pain and excellent soft tissue recovery. The quick loading of a one-piece system, as shown by Dwivedi and Jain,[12] enabled for better tissue recovery and improved gingival mucosa adhesion to establish a healthy and adherent collar to the implant, thereby eliminating the need for a second surgical treatment.

In the present study, OPI showed a mild increase of mesial crestal bone loss in contrast to TPI at 3 months. But, at 6 and 9 months, the crestal bone loss of the TPI was slightly more than OPI. However, the statistical significance suggested no difference between the two implants. But on comparing mesial and distal sides, the crestal bone loss in 6 and 9 months varied vividly in distal than mesial.

This was in accordance with a retrospective study conducted by Ormianer et al.[13] where the results showed a cumulative implant survival rate of 100% following a 5-year post-restoration monitoring period. Additionally, there was no significant difference between the two groups in terms of the amount of bone loss or prosthetic problems, and both implant types had comparable clinical effectiveness. Kurnia et al.[14] evaluated the advantages and disadvantages of OPI and TPI based on two cases, and they concluded that the lack of a micro gap in a OPI was better in preventing crestal bone resorption.

The present study demonstrated that the gingival index remained almost equal in both implant groups after 6 months of loading. Further, a mild increase in OPI compared to TPI at 9 months and after was exhibited. The mandibular overdentures supported by two osseointegrated OPIs had a better effect on bacteriological alterations around the implant abutments than the TPI design, according to Abdelwahed et al.[15]

The study conducted by Beyari on probing depth, plaque accumulation, periotest values, and marginal mucosal conditions revealed no noticeable changes for one-piece small implants. The periotest readings did, however, change significantly and increased within the acceptable range for the implant’s stability.[16] Similarly, in the present study, though there was a significant difference in the gingival index within OPI and TPI, the mean values slightly increased from 3 to 9 months but remained within the accepted range.

Evaluation in the probing depths showed a mild increase in TPI to that of OPI at 3, 6, and 9 months. This was in accordance with the clinical study by Judgar et al.,[17] in which they compared the sulcus depth around unloaded OPI and TPI and assessed that the statistical difference was not significant. Hermann et al.[18] histometrically evaluated the biologic width around one-piece and two-piece titanium implants in the mandibular canine. The results showed that surrounding one-piece non-submerged implants, as opposed to two-piece non-submerged or two-piece submerged implants, the biologic width measurements were more similar to those of natural teeth.

The present study illustrates that OPIs demonstrate comparable results to that of the TPIs in terms of clinical parameters using Loe and Silness gingival index, the probing pocket depth, and the radiographic parameter of marginal bone loss. The results of the study indicate the justification of further research that should be extended for a larger group of subjects and should be followed up for extended periods.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.