Success of Dental Implant Influenced by Abutment Types and Loading Protocol.

Background: Dental implants are considered better, latest, and most advanced technique of teeth replacement in present times with more teeth loss and increased related concerns. Aims: The present clinical trial was carried out to assess marginal bone loss and implant failure in immediate and delayed loading implants. The study also evaluated healing using Polymerase Chain Reaction (PCR) and the effect of risk factors on marginal bone loss. Materials and
Methods: The 44 subjects were randomly divided into two groups with immediate loading and delayed loading protocols. Various soft-tissue parameters were seen clinically. Quantitative PCR was done to detect biomarkers. The collected data were subjected to statistical evaluation with a level of significance at P < 0.05 and the results were formulated.
Results: Concerning marginal bone loss, it was seen that for delayed loading, the bone loss at the implant level was 1.52 ± 0.14, 0.19 ± 0.11, and 0.40 ± 0.12, respectively, at placement, 1 and 2 years. Plaque and mucosal bleeding scores were low at the time of placement with respective values of 0.96 ± 0.12 and 28.42 ± 3.15 for the delayed loading group and 0.98 ± 0.11 and 30.24 ± 3.15 for the immediate loading group. Tartrate-resistant acid phosphatase (TRAP) showing remodeling was high at 3 months in delayed loading (13.3 ± 8.5). Alkaline Phosphatase (ALP) was highest in delayed loading at 3 months (25.2 ± 7.7) and immediate loading at 2 days (32.6 ± 13).
Conclusion: Both immediate loading and delayed loading implants show similar results in terms of bone loss, soft-tissue parameters, and biomarkers in sulcular fluids with relatively few and manageable complications. Copyright:

INTRODUCTION

With the increase in life expectancy, more older individuals, and hence, edentulous are increasingly requiring rehabilitation owing to dental caries and periodontal disease. Tooth loss results in decreased overall quality of life, nutritional impairment, low self-esteem, and compromised aesthetics which are restored by rehabilitation. Dental implants are considered better, latest, and most advanced technique of teeth replacement. Cost-effectiveness can be a drawback for dental implants. However, the initial cost may be high but survival rates are better than tooth-supported prostheses.[1]

Two major factors that determine implant success are abutment use and loading protocols. Recently abutments are debated for cost, leakage risk, and aesthetic compromise. However, abutments are advocated for load sharing and improved implant conditions near the alveolar bone. Also, screw loosening is the most commonly encountered complication of abutments mainly in an externally connected prosthesis. Soft-tissue levels are determined the same around conventional implants and immediate/early loaded implants. Controversial data exist regarding the roughness of implant surface on surrounding implant tissue where a few studies report better soft-tissue dimension with more roughness and others to fail for proving the same.[2]

Initially, implants were loaded 3–6 months after placement, whereas, recently, immediate loading has been advocated. However, despite controversial data, recently the results of both loading procedures have proved the same. Marginal bone loss can also lead to implant failure with a permissible loss of 2 mm within the first 5 years. More bone loss is seen from placement to prosthesis than 5 years after prosthesis. Repeated abutment change does not affect bone loss.[3]

Oral hygiene, mucosal bleeding, probing pocket depth, bleeding on probing, radiographic changes, and/or crevicular fluid assessments are used to evaluate implant success/failure along with other technical complications.[4] The present clinical trial was carried out to assess marginal bone loss and implant failure in immediate and delayed loading implants, technical and biological complications with implants, the effect of the abutment, and their surface design on marginal bone and soft-tissue loss. The study also evaluated healing using PCR and the effect of risk factors on marginal bone loss.

MATERIALS AND METHODS

The present prospective randomized clinical trial was carried out on 44 subjects who were followed for 2 years after obtaining the ethical clearance from the concerned committee. The study was carried out on 44 subjects within the age range of 47–71 years with a mean age of 56.4 years.

The inclusion criteria for the study were partially edentulous subjects with no associated systemic disease or medication history, and the subjects with sufficient bone levels for implants and stability. The exclusion criteria were subjects with malocclusion that put additional force on implants, smokers, and parafunctional habits.

These 44 subjects were then randomly divided into two groups including the test group and the control group. The test group included 22 subjects with immediate loading and the control group had 22 subjects in which delayed loading was done. In all subjects, titanium implants of Nobel Biocare™ were placed and titanium multiabutments were used. In 44 subjects, 108 implants were placed mainly on the regular platform and rarely narrow platform implants. All procedures were carried out by a single operator expert in the field.

Following surgery, immediate loading using a temporary prosthesis in the test group was done within 3 days of implant placement and the final prosthesis was cemented at 6 months. For the control group, direct permanent restoration of porcelain over titanium abutment was given at 3 months after implant placement. The prosthesis comprised three units in 14 subjects of both the groups (n = 28) and four units in 8 subjects of each group (n = 16). Patients were examined at 2 days, 1 week, 4 weeks, 3 months, 6 months, 12 months, and 24 months after placement. Implants were considered a failure if they were mobile or had periapical radiolucency on any examination visit.

The parameters assessed on examination were probing pocket depth, bleeding on probing, marginal bone loss, and coronal height of soft-tissue. For gene expression analysis, crevicular washings were collected. Quantitative PCR was done to detect interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), osteocalcin (OC), alkaline phosphatase (ALP), cathepsin K (CK), tartrate-resistant acid phosphatase (TRAP), and 18S ribosomal RNA.

The collected data were subjected to statistical evaluation incorporating ANOVA using IBM SPSS software 2012; version 21.0, Armonk, NY, and the results were formulated keeping the level of significance at P < 0.05.

RESULTS

At the end of 2 years, 2 patients died of natural cause in each group leaving a total of 42 subjects for final consideration. After 1 year, four implants were lost, and two in each group were then excluded. Further, at 2 years, no implants were lost showing comparable success rates in the two groups. Concerning marginal bone loss, it was seen that for delayed loading, the bone loss at implant level was 1.52 ± 0.14, 0.19 ± 0.11, and 0.40 ± 0.12, respectively, at placement, 1 and 2 years. These consecutive values for immediate loading groups were 1.63 ± 0.14, 0.21 ± 0.10, and 0.12 ± 0.17 which were statistically non-significant. The overall bone loss for immediate loading implants at placement, 1 and 2 years were 1.32 ± 0.10, 0.34 ± 0.10, and 0.19 ± 0.11, respectively. These consecutive values for the delayed loading group were 1.23 ± 0.10, 0.31 ± 0.08, and 0.20 ± 0.09. Significantly lower bone loss was seen in milled abutment and higher in oxidized at 1 year. At 2 years, a significant lower bone loss was in milled abutment sites [Table 1].

Table 1

Marginal bone loss at consecutive recalls in study groups

Reference Point	Delayed Loading			Immediate Loading
	At placement	1 year	2 years	At placement	1 year	2 years
Level of Implant	1.52±0.14 (n=18)	0.19±0.11	0.40±0.12	1.63±0.14 (n=18)	0.21±0.10	0.12±0.17
Oxidized	1.08±0.15 (n=17)	0.54±0.12	0.9±0.15	1.30±0.15 (n=17)	0.42±0.21	0.29±0.19
Milled	1.08±0.12 (n=17)	0.19±0.12	0.11±0.13	0.95±0.19 (n=18)	0.41±0.16	0.29±0.19
Total (n=52)	1.23±0.10	0.31±0.08	0.20±0.09	1.32±0.10	0.34±0.10	0.19±0.11

Concerning soft-tissue evaluation, plaque, mucosal bleeding, peri-implant probing depth, bleeding on probing, and soft-tissue height were evaluated. Plaque and mucosal bleeding scores were low at the time of placement with respective values of 0.96 ± 0.12 and 28.42 ± 3.15 for the delayed loading group and 0.98 ± 0.11 and 30.24 ± 3.15 for the immediate loading group which increased at 1 year to 1.13 ± 0.26 and 35.12 ± 0.12, and 1.12 ± 0.22 and 36.42 ±0.21, respectively, for delayed and immediate loading groups. Probing pocket depth and bleeding on probing increased from baseline to 1 year for both groups and then decreased. These alterations were non-significant with final values for the delayed and immediate groups as 0.11 ± 0.13 and 0.29 ± 0.19, respectively. Bleeding on probing increased consecutively at all recalls. Soft-tissue height increased from placement to 1 year and decreased at 2 years in both groups with the final value of 2.20 ± 1.02 mm and 2.01 ± 0.22 mm for delayed and immediate loading groups [Table 2].

Table 2

Soft-tissue changes at consecutive recalls in study groups

Soft-tissue parameter	Delayed Loading			Immediate Loading
	At placement	1 year (p)	2 years (p)	At placement	1 year (p)	2 years (p)
Plaque Score	0.96±0.12	1.13±0.26	1.61±0.12	0.98±0.11	1.12±0.22	1.62±0.17
Mucosal Bleeding (%)	28.42±3.15	35.12±0.12	38.4±2.15	30.24±3.15	36.42±0.21	38.2±2.19
Probing depth	1.08±0.12	0.19±0.12	0.11±0.13	0.95±0.19	0.41±0.16	0.29±0.19
Bleeding on Probing (buccal)	10.22±2.10	12.32±2.08	14.26±3.09	11.32±2.14	13.34±3.10	15.19±1.12
Bleeding on Probing (proximal)	10.26±1.10	11.22±1.08	16.26±3.09	10.32±3.14	11.34±2.24	15.19±1.12
Soft-tissue height	1.19±0.21	2.24±0.18	2.20±1.02	1.82±0.16	2.02±0.14	2.01±0.22

Regarding complications, manageable peri-implantitis was seen in five implants (two delayed, three immediate) at the end of 1 year (two in each group) and in additional four implants at 2 years which were managed well. At 1 year, two subjects reported porcelain chipping. Crevicular washings had considerable sulcular fluid at 1 month which diminished with hardly any fluid at 1 or 2 years. At 1 month, the fluid showed various cells including monocytes, granulocytes, and mesenchymal cells, some entrapped in cellulose meshwork.

Various biomarkers evaluated using qPCR showed that IL-1β was high at 2 days (974.4 ± 425.1) in delayed loading and was non-significant at all other times in both groups. TRAP showing remodeling was high at 3 months in delayed loading (13.3 ± 8.5). ALP was highest in delayed loading at 3 months (25.2 ± 7.7) and immediate loading at 2 days (32.6 ± 13). TNF-α was highest on day 2 in the immediate loading group (97.2 ± 54.6) as shown in Table 3.

Table 3

Biomarkers in study groups

Marker	Delayed Loading			Immediate Loading
	2 days	1 month	3 months	2 days	1 month	3 months
TNF-α	47.7±28.5	11.2±2.6	15.3±6.0	97.2±54.6	11.4±7.6	15.3±11.1
Alkaline Phosphatase	11.3±1.2	6.8±2.2	25.2±7.7	32.6±13	11±9.2	4.3±1.4
TRAP	3.1±1.2	2.6±0.6	13.3±8.5	2.4±0.9	1.5±0.4	1.1±0.2
Osteocalcin	1.5±1.2	3.1±0.7	43.4±27.4	2.4±1.4	1.3±0.4	2.4±1.2
IL-1β	974.4±425.1	436.7±149.3	577.1±142.4	312.7±285.6	249.6±124.5	292±97.4

DISCUSSION

The present study found no difference in implant survival for both the groups with four implant losses. Overall, bone loss for immediate loading implants at placement, 1 and 2 years were 1.32 ± 0.10, 0.34 ± 0.10, and 0.19 ± 0.11, respectively. Significantly lower bone loss was seen in milled abutment and higher in oxidized at 1 year. At 2 years, a significant lower bone loss was in milled abutment sites. These findings were consistent with Weng D, et al.[5] in 2010 and Piattelli A, et al.[6] in 2003, where authors found no difference in the immediate and delayed loading groups in marginal bone loss.

Plaque and mucosal bleeding scores were low at the time of placement with respective values of 0.96 ± 0.12 and 28.42 ± 3.15 for the delayed loading group and 0.98 ± 0.11 and 30.24 ± 3.15 for the immediate loading group, which increased at 1 year to 1.13 ± 0.26 and 35.12 ± 0.12, and 1.12 ± 0.22 and 36.42 ±0.21, respectively, for the delayed and immediate loading groups. For bleeding, a significant difference (P< 0.05) was seen from placement to 1 year and no significant difference from 1 to 2 years. Probing pocket depth and bleeding on probing increased from baseline to 1 year for both groups and then decreased. These alterations were non-significant with final values for the delayed and immediate groups as 0.11 ± 0.13 and 0.29 ± 0.19, respectively. These findings agreed with the findings of Schou S, et al.[7] in 2008, where similar results regarding soft-tissue parameters were reported.

Manageable peri-implantitis was seen in five implants (two delayed, three immediate) at the end of 1 year (two in each group) and in additional four implants at 2 years which were managed well. At 1 year, two subjects reported porcelain chipping. These results were comparable to Lang LP, et al.[8] in 2004 and Pjetursson BE, et al.[9] in 2012, where complications around implants were managed well.

Various biomarkers evaluated using qPCR showed that IL-1β was high at 2 days (974.4 ± 425.1) in delayed loading and was non-significant at all other times in both groups. TRAP showing remodeling was high at 3 months in delayed loading (13.3 ± 8.5). TNF-α was highest on day 2 in the immediate loading group (97.2 ± 54.6). These findings were the same as those by Schierano G, et al.[10] in 2008 and Lachmann et al.[11] in 2007 with similar biomarker levels in implant sulcus.

CONCLUSION

Within its limitations, the present study concludes that both immediate loading and delayed loading implants show similar results in terms of bone loss, soft-tissue parameters, and biomarkers in sulcular fluids with relatively few and manageable complications. However, the study had a few limitations like small sample size and monitoring periods. Hence, more longitudinal studies with larger sample and long monitoring periods are required to reach a definitive conclusion.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.