A comparative evaluation of immediate versus delayed loading of two implants with mandibular overdenture: An in vivo study.

INTRODUCTION: Implant-supported overdenture has been a common treatment for edentulous patients for the past several years and predictably achieves good clinical results, especially in those patients who were uncomfortable with their conventional dentures, as they provide additional retention and support. The concept of immediate loading is more applicable to completely edentulous patients because of their functional and esthetic requirements. Hence, the present study aims to evaluate the outcomes of immediate loading of mandibular two-implant-retained overdenture and compare it with the conventional delayed loading concept.
METHOD: This in vivo study was conducted to compare immediate versus delayed loading of two implants with mandibular overdenture. A total of 20 completely edentulous patients (10 delayed loading and 10 immediate loading) were included in the study and certain parameters, i.e., bone loss around implants, periodontal pocket depth, pain and discomfort, implant stability, and microflora around implants, were measured immediately and after healing period of 3 and 6 months. RESULT: It can be analyzed from the observations that patients were more satisfied with delayed loading in terms of comfort, speech, function, pain, and chewing efficiency as compared to immediate loading.
CONCLUSION: It is concluded that implants loaded under delayed protocol seem to have a higher success rate as compared to those that are loaded immediately.

INTRODUCTION

Edentulous patients with a severely resorbed mandibular residual ridge represent a significant health-care problem in the growing elderly population, which often experiences difficulty with chewing, speech, loss of retention and stability.[1] The loss of retention and stability may cause denture stomatitis, denture-induced residual ridge resorption, and diminished masticatory function as compared to natural teeth.[2] For the past several years, the emphasis from the conventional denture therapy has been shifted toward the implant-supported overdenture which is potentially a preferred treatment option for edentulous patients.

To improve retention and stability of complete denture, particularly mandibular denture, several designs have been formulated, but the most commonly used design for the mandibular overdenture is two implants in the lateral–canine areas with a ball attachment as it is less expensive and most commonly used in clinical practice to serve most of the patients.[3] The different protocols advocated for the loading of the dental implants are immediate loading, early loading, progressive loading, and delayed loading. However, immediate and delayed loading protocols are commonly considered in completely edentulous patients.

MATERIALS AND METHODS

This prospective in vivo study was conducted to compare immediate versus delayed loading of two implants with mandibular overdenture. A total of 20 completely edentulous patients (10 delayed loading and 10 immediate loading) were included in the study and certain parameters, i.e., bone loss around implants, periodontal pocket depth, pain and discomfort, implant stability, and microflora around implants, were measured immediately and after healing period of 3 and 6 months as plotted in Graphs 1 and 2.

Graph 1

Gender Wise Distribution of Study Sample in Different Loading Protocols

Graph 2

Mean Age in Both Groups

After signing informed consent, the patients were consecutively included in the study and scheduled for an initial screening, [Figures 1 and 2] i.e., patient's chief complaint, previous dental and medical history, evaluation of mandibular alveolar ridge, and jaw relationship, and further panoramic radiographs (Kodak, India) and computed tomography (GE, Japan) were done for all patients.

Figure 1

Pre-operative photograph for delayed loading of implant

Figure 2

Intra oral mandibular arch

New maxillary and mandibular complete dentures were made for all patients followed by follow-up sessions after denture delivery. When patients were comfortable with their new dentures, the implant surgery appointment was scheduled. After this, the conventional mandibular denture was duplicated in heat cure clear acrylic resin (Pyrax, India) for the fabrication of surgical guide into which the holes were drilled with a rounded carbide bur, attached to a straight handpiece mounted on the milling machine, which aids in the proper placement of implants.

Intraoral surgical and extraoral site were painted with Betadine. The required area, i.e., 33 and 43, was anesthetized by mental nerve block with 2% lignocaine hydrochloride (Lignox, Indoco Remedies Ltd., India) with 1:200,000 adrenaline. A mid-crestal incision was given distally from one side of canine to contralateral side of canine [Figure 3]. Then, the round bur was used and the bone at the implant site was ditched using the surgical guide [Figure 4] into which the holes were drilled using a milling machine. After this, the pilot drill was placed over the entry point and lightly pumped up and down until the cortical plate was penetrated [Figure 5]. The saline irrigation was carried out throughout the drilling procedure. The implant (Alfa Bio, Israel, 3.3 mm × 10 mm) vial was opened, and the implant body was placed first manually into the prepared site intraorally, and then using a thumb wrench, the implant was inserted into the prepared site in a clockwise manner by exerting a downward pressure. The implant was ratcheted until it demonstrated a rock-like integration prior and the second implant was placed in the same way [Figure 6].

Figure 3

Mid crestal incision

Figure 4

Surgical guide in patient mouth

Figure 5

Pilot drill

Figure 6

Two implants in place

The flap was sutured (3-0 Nonresorable, Ethicon, India) after tightening the cover screws, postoperative instructions were given, and intraoral periapical radiographs were done to confirm the proper placement of implants. After 3 months, the dentures were modified to accept the housings and delivered to the patients [Figures 7–10]. However, in case of immediate loading, the dentures were modified immediately. After this, occlusion was established and the dentures were delivered to the patients. Then, patients were recalled after 24 h, 72 h, 4 weeks, and 6 months, and complaints of soreness and discomfort were assessed and the dentures were relived in those areas [Figures 11–14].

Figure 7

Metal housing with nylon cap attached over ball abutment

Figure 10

Post-operative radiograph

Figure 11

Preoperative photograph for immediate loading

Figure 14

Post-operative radiograph

Mandibular denture with metal housing and nylon cap

Post-insertion view of delayed loading of implant

Ball abutment placed immediately after placement of implant

Post insertion

RESULTS

The statistical analysis was carried out using SPSS version 19.0 software (IBM Corporation, Armonk, New York, USA). The significance between the groups was done using Chi-square statistics and independent “t”statistics and P < 0.05 was considered statistically significant. The data were collected, evaluated, and statistically analyzed and tabulated.

It can be analyzed from the observations that patients were more satisfied with delayed loading in terms of comfort, speech, function, pain, and chewing efficiency as compared to immediate loading.

Crestal bone loss when compared within and between the groups was found to be statistically nonsignificant for both right and left side implants as shown in Tables 1–4 and plotted in Graphs 3 and 4. Periodontal pocket depth when compared within the groups was found to be statistically significant at 0 and 3 months and nonsignificant at 6 months for both right and left side implants as shown in Tables 5–8 and plotted in Graphs 5 and 6. Pain and discomfort when compared within the groups were found to be statistically nonsignificant for the right side and statistically significant at 0 month and nonsignificant at 3 months and 6 months for the left side implants as shown in Tables 9–12 and plotted in Graphs 7 and 8. Implant stability when compared within and between the groups was found to be statistically nonsignificant for both right and left side implants as shown in Tables 13–16 and plotted in Graphs 9 and 10. Microflora around implants when compared within and between the groups was found to be statistically nonsignificant for both right and left side implants as shown in Tables 17–20 and plotted in Graphs 11 and 12.

Table 1

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Crestal bone loss for Right side implants (mm)

Crestal bone loss	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	0.00+.000	0.000	0.00+.000	0.000
At 3 months	1.450+.5986	0.1893	1.850+.5297	0.1675
At 6 months	0.660+1.2501	0.3953	0.830+.9707	0.3070

S.D- Standard deviation, S.E.M- Standard error of mean

Table 4

Comparison of Crestal bone loss for Left side implants between Group I and II (using independent ‘t’ test)

Crestal Bone Loss	Probability of unpaired ‘t’ test	P/Significance
At 0 month	-	-
At 3 months	1.985	0.063/Non Significant
At 6 months	0.755	0.460/Non Significant

Graph 3

Crestal Bone Loss at Right Side Implants in Different Loading Protocols

Graph 4

Crestal Bone Loss at Left Side Implants in Different Loading Protocols

Table 5

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Periodontal Pocket Depth for Right side implants (mm)

Periodontal Pocket Depth	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	4.10+.316	0.100	5.00+.667	0.211
At 3 months	3.30+.675	0.213	4.10+.568	0.180
At 6 months	3.30+.949	0.300	3.60+1.075	0.340

Table 8

Comparison of Periodontal Pocket Depth for Left side implants between Group I and II (using independent ‘t’ test)

Periodontal Pocket Depth	Probability of unpaired ‘t’ test	P/Significance
At 0 month	3.674	0.002/Significant*
At 3 months	3.973	0.001/Significant*
At 6 months	1.309	0.207/Non Significant

Graph 5

Periodontal Pocket Depth at Right Side Implants in Different Loading Protocols

Graph 6

Periodontal pocket depth at the left side implants in different loading protocols

Table 9

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Pain & Discomfort for Right side implants

Pain & Discomfort	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	2.80+.422	0.133	3.00+.000	0.000
At 3 months	1.50+.972	0.307	1.90+1.197	0.379
At 6 months	0.40+1.265	0.400	0.80+1.687	0.533

Table 12

Comparison of Pain & Discomfort for Left side implants between Group I and II (using independent ‘t’ test)

Pain & Discomfort	Probability of unpaired ‘t’ test	P/Significance
At 0 month	2.449	0.025/Significant*
At 3 months	1.152	0.264/Non Significant
At 6 months	1.000	0.331/Non Significant

Graph 7

Pain and discomfort at the right side implants in different loading protocols

Graph 8

Pain and discomfort at the left side implants in different loading protocols

Table 13

Percentage of Delayed and Immediate loaded implants (Group I and Group II respectively) for Implant Stability for Right side implants

Implant Stability	Delayed Loading Cases (%)		Immediate Loading Cases (%)
	Dull	Crystal	Dull	Crystal
At 0 month	100.0	0	100.0	0
At 3 months	10.0	90.0	20.0	80.0
At 6 months	10.0	90.0	20.0	80.0

Table 16

Comparison of Implant Stability for Left side implants between Group I and II (using Chi-square test)

Implant Stability	Chi square test	Degree of Freedom (df)	P/Significance
At 0 month	-	-	-
At 3 months	1.053	1	0.305/Non Significant
At 6 months	1.053	1	0.305/Non Significant

Graph 9

Implant stability at the right side implants in different loading protocols

Graph 10

Implant stability at the left side implants in different loading protocols

Table 17

Percentage of Delayed and Immediate loaded implants (Group I and Group II respectively) for Microflora around Right side implants

Microflora	Delayed Loading Cases (%)		Immediate Loading Cases (%)
	G+ve, G-ve	G-ve	G+ve, G-ve	G-ve
At 0 month	100.0	0	100.0	0
At 3 months	90.0	10.0	80.0	20.0
At 6 months	90.0	10.0	80.0	20.0

Table 20

Comparison of Microflora around Left side implants between Group I and II (using Chi-square test)

Microflora	Chi square test	Degree of Freedom (df)	P/Significance
At 0 month	-	-	-
At 3 months	1.053	1	0.305/Non Significant
At 6 months	1.053	1	0.305/Non Significant

Graph 11

Microflora around right side implants in different loading protocols

Graph 12

Microflora around left side implants in different loading protocols

DISCUSSION

In this study, a comparative evaluation of immediate versus delayed loading of two implants with mandibular overdenture was done. The treatment protocol involved fabrication of new conventional complete dentures for all the patients, which after 3 months for delayed loaded and immediately after implant placement for immediate loaded was modified to implant-retained overdentures. During surgery, a modified mid-crestal incision was given, starting slightly distal to the canine but not crossing the midline (i.e., two mini flaps). Its advantages include smaller flap with less resultant discomfort and swelling because muscle attachment is uninvolved and smaller flap with less resultant bone loss.

Naert et al. reported in their 10-year randomized clinical study that the ball group scored best in relation to retention and patient satisfaction for overdenture patients.[4] Whereas, Sadowsky reported that solitary ball attachments appear to be less expensive and less technique sensitive.[5] Davis and Packer also in their 5-year study stated that patients with mandibular overdentures retained by two implants interforaminally had higher satisfaction scores than complete denture patients.[6]

In 1977, two-stage protocol or delayed loading concept was introduced and primary reasons cited for this approach were to reduce the risk of bacterial infection and to prevent apical migration of the body of the implant, and following this procedure, a second-stage surgery is necessary to uncover these implants and place a prosthetic abutment. But later in 1979, the concept of immediate loading of implants, which can be defined as an implant-supported temporary or definitive restoration in occlusal contact at the same appointment or shortly thereafter of the implant insertion. Since then, this protocol is known as “teeth in a day”.[7] However, among the two protocols, delayed loading procedure guarantees that the implant is well protected during its incorporation in bone when the osseous interface has not been established properly, as evidenced from experimental and clinical studies.[8]

CONCLUSION

A comparison of immediate versus delayed loading of two implants with mandibular overdenture leads to the conclusion that implants loaded under delayed protocol seem to have a higher success rate as compared to those that are loaded immediately, as immediate loading needs skills, so should be done carefully. More clinical trials are needed to understand the predictability of the protocols for immediate and delayed loading.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Table 2

Comparison of Crestal bone loss for Right side implant between Group I and II (using independent ‘t’ test)

Crestal Bone Loss	Probability of unpaired ‘t’ test	P/Significance
At 0 month	-	-
At 3 months	1.583	0.131/Non Significant
At 6 months	340	0.738/Non Significant

Table 3

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Crestal bone loss for Left side implants (mm)

Crestal Bone Loss	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	0.00+.000	0.000	0.00+.000	0.000
At 3 months	1.200+.3496	0.1106	1.650+.6258	0.1979
At 6 months	0.260+.4377	0.1384	0.470+.7631	0.2413

Table 6

Comparison of Periodontal Pocket Depth for Right side implants between Group I and II (using independent‘t’ test)

Periodontal Pocket Depth	Probability of unpaired ‘t’ test	P/Significance
At 0 month	3.857	0.001/Significant*
At 3 months	2.869	0.010/Significant*
At 6 months	0.662	0.517/Non Significant

Table 7

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Periodontal Pocket Depth for Left side implants (mm)

Periodontal Pocket Depth	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	3.80+.422	0.133	5.00+.943	0.298
At 3 months	3.00+.000	0.000	4.10+.876	0.277
At 6 months	3.00+.000	0.000	3.40+.966	0.306

Table 10

Comparison of Pain & Discomfort for Right side implants between Group I and II (using independent‘t’ test)

Pain & Discomfort	Probability of unpaired ‘t’ test	P/Significance
At 0 month	1.500	0.151/Non Significant
At 3 months	0.820	0.423/Non Significant
At 6 months	0.600	0.556/Non Significant

Table 11

Mean & S.D of Delayed and Immediate loaded implants (Group I and Group II respectively) for Pain & Discomfort for Left side implants

Pain & Discomfort	Delayed Loading Cases		Immediate Loading Cases
	MEAN+S.D	S.E.M	MEAN+S.D	S.E.M
At 0 month	2.60+.516	0.163	3.00+.000	0.000
At 3 months	1.20+.422	0.133	1.50+.707	0.224
At 6 months	0.00+.000	0.000	0.30+.949	0.300

Table 14

Comparison of Implant Stability for Right side implants between Group I and II (using Chi-square test)

Implant Stability	Chi square test	Degree of Freedom (df)	P/Significance
At 0 month	-	-	-
At 3 months	0.392	1	0.531/Non Significant
At 6 months	0.392	1	0.531/Non Significant

Table 15

Percentage of Delayed and Immediate loaded implants (Group I and Group II respectively) for Implant Stability for Left side implants

Implant Stability	Delayed Loading Cases (%)		Immediate Loading Cases (%)
	Dull	Crystal	Dull	Crystal
At 0 month	100.0	0	100.0	0
At 3 months	0.0	100.0	10.0	90.0
At 6 months	0.0	100.0	10.0	90.0

Table 18

Comparison of Microflora around Right side implants between Group I and II (using Chi-square test)

Microflora	Chi square test	Degree of Freedom (df)	P/Significance
At 0 month	-	-	-
At 3 months	0.392	1	0.531/Non Significant
At 6 months	0.392	1	0.531/Non Significant

Table 19

Percentage of Delayed and Immediate loaded implants (Group I and Group II respectively) for Microflora around Left side implants

Microflora	Delayed Loading Cases (%)		Immediate Loading Cases (%)
	G+ve, G-ve	G-ve	G+ve, G-ve	G-ve
At 0 month	100.0	0	100.0	0
At 3 months	100.0	0.0	90.0	10.0
At 6 months	100.0	0.0	90.0	10.0