Comparative evaluation of masticatory efficiency, clinical performance, and patient satisfaction of single implant-retained mandibular overdenture versus conventional complete denture: A prospective in vivo study

Abstract

Aim:

The aim of this within-subject prospective clinical study was to investigate the scope of single implant mandibular overdenture by assessing its masticatory efficiency, clinical performance, and patient satisfaction compared to conventional complete dentures.

Settings and Design:

Prospective In Vivo Study.

Material and Methods:

This prospective in vivo study was conducted in the Department of Prosthodontics and Crown and Bridge, Christian Dental College, Ludhiana. A total of 12 completely edentulous patients received a single implant in the mandibular anterior midline region. After the healing period, the conventional maxillary and mandibular dentures were fabricated. 15 days post insertion of the conventional dentures, patients were evaluated for masticatory efficiency, clinical performance including retention and stability, and patient satisfaction. To evaluate the masticatory efficiency blue raspberry and original pink “Hubba Bubba tape gum” were used as a test food. Colorimetric analysis was done to assess variance of hue. To assess clinical performance, retention, and stability of the mandibular denture was recorded using a digital force gauge and was tabulated as per CU-modified Kapur's criteria. OHIP-14 index was used to assess patient satisfaction. After evaluation of the parameters of conventional dentures, the denture was converted into an implant-retained mandibular denture by chairside conversion with locator attachments. 15 days post-implant loading, parameters of the implant retained mandibular overdenture were assessed again followed by statistical analysis.

Statistical Analysis Used:

The masticatory efficiency was assessed using a paired t-test. The patient satisfaction was sequentially assessed with Wilcoxon signed rank test and thereafter paired t-test was used to compare between conventional complete denture and overdenture. Clinical performance was assessed using the Wilcoxon signed rank test.

Results:

The masticatory efficiency of single implant mandibular overdenture was higher than that of conventional complete dentures. The clinical performance of the overdenture was higher than that of the conventional denture. Stability being a time-dependent parameter might need longer follow-ups for further conclusions. Patient satisfaction with single implant retained overdenture was significantly higher than conventional complete dentures.

Conclusion:

Single implant mandibular overdenture has improved masticatory efficiency, clinical performance, and patient satisfaction compared to conventional complete dentures.

INTRODUCTION

The World Health Organization's (WHO) report from 2022 states that adults who are 60 years of age and older experience complete edentulism on average by 23% around the world.[1] More than 36 million patients have been estimated to be edentulous in the United States, and the prevalence of edentulism in India, as per the Study on Global AGEing and adult health by the WHO, is 16.3% and by the Dental Council of India in people aged 65–74 years old is 29.3%.[2,3,4] The increase in edentulous patients worldwide has increased the need to restore them with a viable and affordable treatment modality.[2]

Management of completely edentulous patients is challenging in moderately to severely resorbed ridges, especially in the mandibular arch.[5] The introduction of titanium implants has enabled the rehabilitation of completely edentulous patients with endosseous implants as standard care.[6] McGill and York's consensus specified the need for mandibular two-implant overdenture as the minimal first-choice treatment option for edentulous patients.[5,6] In developing countries, two-implant overdenture costs at least 2.4 times more than conventional complete dentures.[5,6,7,8] Passia and Kern's study on mandibular single-implant overdenture reports a cumulative implant survival rate of 96.6% over an average follow-up period of 37.3 months.[9,10] A clinical study on mandibular single-implant overdenture with a follow-up of 10 years reported a 100% success rate.[9,10] Ahmed Elawady et al. found a single-implant overdenture to be superior to a two-implant overdenture in terms of bone loss and implant failure rate.[11] Coutinho et al. reported positive outcomes after a 5-year follow-up study on patient-related outcomes using mandibular single-implant overdenture.[12,13] Passia et al. conducted a study on edentulous patients to assess the intraindividual chewing efficiency and observed an improvement in masticatory efficiency, irrespective of the number of implants.[14]

Masticatory efficacy declines as a person becomes completely edentulous. A chewing efficiency of at least 25% is considered sufficient for proper food digestion. Therefore, assessing the masticatory performance of completely edentulous patients after prosthetic rehabilitation becomes important.[15,16] Studies conducted with single-implant overdenture have shown improvement in patient satisfaction, and in terms of masticatory efficiency, it provides varying results.[8,9,10,11,12,13,14,17] Recent systematic reviews show improvement in masticatory efficiency with implant overdentures, despite the implant number, and have promising results even with single-implant overdentures.[6,8,11,12,18,19] Single-implant mandibular overdenture is relatively less challenging and potentially less complicated for older populations.[6,8,19]

To the author's best knowledge, there are limited studies comparing the intraindividual chewing efficiency, assessment of clinical performance, and patient satisfaction of a single-implant overdenture. One of the primary aims of single-implant overdenture treatment is to make overdenture treatment more affordable and provide a better quality of life for a wide spectrum of patients. Toward this direction, this study attempts to compare its clinical performance, masticatory efficacy, and quality of life versus conventional complete dentures. The study's null hypothesis was that a conventional complete denture and a single-implant-retained mandibular overdenture had identical masticatory effectiveness, clinical performance, and quality of life.

MATERIALS AND METHODS

The study obtained institutional ethical committee approval (Reference number: CDC/ERC/2020/13). Twelve completely edentulous patients of either gender and of varied age groups were selected for the study based on the inclusion criteria [Table 1].

Table 1.

Inclusion and exclusion criteria

Inclusion criteria

Exclusion criteria

Completely edentulous nondenture wearers willing to participate in the study Patients who are physically and psychologically suitable for implant surgery Patients with ACP type II and type Ill mandibular residual ridge were considered in the inclusion criteria Residual bone of minimum 15 mm length and 4.0 mm diameter

<10 mm of alveolar bone height in the anterior mandible and <4 mm diameter Absolute contraindication for implant placement Recent stroke and myocardial infarction, valvular prosthesis surgery, immunosuppression, bleeding issues, active cancer therapy, drug abuse, psychological disease, and intravenous bisphosphonate use Neuromuscular coordination disorder History of head-and-neck radiation Bleeding disorder

ACP: American College of Prosthodontists

Calculation of sample size

The sample size was calculated in accordance with the results of the prior study by Burns et al.[20] The confidence range and margin of error for sample size calculation were 98% and 8%, respectively. A sample size of 12 was used in the present study using formula n = Z_α/2² P × (1 − p)/d², where Z_1−α/2 = 1.96, is the standard normal deviate at type 1 error α =0.05.

The study's methodology and intended use were fully disclosed to the participants. Before the study's commencement, written informed consent to undergo treatment was obtained. An orthopantomographic assessment of the mandibular anterior edentulous space was done. Depending on available bone, an implant of appropriate length ranging from 10 mm to 11.5 mm (10 mm: n = 8; 11.5 mm: n = 4) and diameter of 3.5–4.5 mm (3.5 mm: n = 7; 4.0 mm: n = 4; 4.5 mm: n = 1) was placed in the mandibular anterior midline region. Three months later, each participant received a set of complete maxillary and mandibular dentures made by a single practitioner in accordance with a standardized prosthodontic process. Patients were recalled after 15 days of using conventional complete dentures to allow for settling in the newly fabricated dentures. Masticatory efficiency, clinical performance, including retention and stability, and patient satisfaction were assessed [Figure 1].

Figure 1.

Schematic presentation of study design. OHIP: Oral health impact profile

One week later, locator abutment was tightened on the implant at 25 Ncm [Figure 2].

Figure 2.

Locator abutment tightened onto the single implant

A nylon cap and metal housing were incorporated at the tissue surface of the denture, according to the implant position by standard chairside pickup using autopolymerizing acrylic resin [Figure 3].

Figure 3.

Intaglio surface of mandibular single-implant overdenture

Patients were recalled after 15 days of using single-implant-retained overdenture. Masticatory efficiency, clinical performance, including retention and stability, and patient satisfaction were assessed. Follow-up was done at the end of 3 months.

Evaluation of masticatory efficiency

Although the sieve method is the gold standard for measuring masticatory efficiency, participants with impaired oral function may not always be able to break up test foods because their maximum biting strength may be lower than that needed to crush the test food.[21] Therefore, the chewing gum test developed by Schimmel et al. was used in this investigation to measure the masticatory efficiency. Silva et al. displayed that the two-color chewing gum test was reliable for assessing the masticatory function of complete denture patients.[22,23,24] It was evaluated based on their capacity for bolus-kneading by the ability to mix two colors.[22,23,24]

The same operator asked each subject to chew the test food (Hubba-Bubba Tapes^®) gums in the sour blue raspberry and original pink flavors of dimensions 30 mm × 18 mm × 3 mm for 25 cycles. The collected chewed-gum bolus was then manually pressed between two pieces of glass plates to create a wafer with a thickness of 1 mm. A digital camera was then used to take photographs of the wafer's both sides. A single JPEG file with a maximum size of 1000 pixels was created by joining both sides.[22,23,24,25,26]

A freeware ViewGum (dHAL program) was used to conduct the colorimetric analysis. The hue value was determined, and the software first converted the images into the HSI color space [Figure 4]. The variance of hue (VOH) was statistically analyzed to compare the masticatory efficiency of single-implant overdenture to that of conventional complete denture using paired t-tests.

Figure 4.

User interface in ViewGum software

Evaluation of clinical performance: Retention and stability

Retention and stability were assessed using a digital force gauge (Lutron FG 20 kg). It has great resolution and precision, a measuring capacity of 20.00 kg/44.10 lb/196.10 N, and an overload capacity of 66 lb/30 kg.[27] Measurements were tabulated based on CU-modified Kapur criteria.[20] A tiny distal hook was used to join the “pull” end of the force gauge to a 15 cm long piece of 19G stainless steel wire. The force gauge was used to pull the denture vertically, and the values were recorded when the denture was dislodged from residual ridge.[20,28]

For evaluation of stability, the force gauge's end was placed near the canine on one side of the gingival embrasure of the denture and was pushed with a horizontal push force parallel to the plane of occlusion. The amount of force required to destabilize the denture was noted.[20,28] The retention and stability values are then tabulated as per CU-modified Kapur's criteria for both conventional and single-implant-retained overdenture and then were statistically analyzed using Wilcoxon signed-rank test.

Patient satisfaction

Oral health-related quality of life (OHRQoL) was assessed using Oral Health Impact Profile (OHIP 14)[29,30,31] Each patient was given the questionnaire, and the responses were statistically analyzed by the Wilcoxon signed-rank test.

RESULTS

Masticatory efficiency

The masticatory efficiency was evaluated statistically by paired t-test, in which the average VOH was calculated for 12 patients, and a comparison was made. The average VOH for complete denture patients was 0.492 ± 0.224 standard deviation (SD), P = 0.001, and t-test value 4.440, and for single-implant-retained overdentures were 0.202 ± 0.196 SD, P = 0.001, and t-test value 4.440. The paired t-test difference between a conventional denture and single-implant overdenture was 0.289 ± 0.226 SD, (P < 0.05) and t >1, which shows that there is better mixing of different colored chewing gums with single-implant-retained overdenture in comparison to a conventional denture [Table 2].

Table 2.

Hue score

Group	Mean hue score	Median	±SD	IQR	Mean difference	t	P
CD	0.492	0.509150	0.224	0.352100–0.717193	0.289±0.226	4.440	0.001*
OVD	0.202	0.067100	0.196	0.049350–0.401500

*P<0.05 significant, paired t-test. SD: Standard deviation, IQR: Interquartile range, CD: Complete denture, OVD: Overdenture

Retention and stability

Clinical performance was assessed using the Wilcoxon Signed-Rank test, in which the retention and stability values were evaluated according to the CU-modified Kapur method. There was a statistically significant (P = 0.001) increase in retention and stability on the transformation of a complete denture to a single-implant overdenture. Retention scores of single-implant-retained overdentures (median = 2.00; interquartile range [IQR]: 2.00–2.75) were higher than that of conventional complete dentures (median = 1.00; IQR: 1.00–1.00) [Table 3].

Table 3.

Retention score

Scoring	CD, n (%)	OVD, n (%)	CD versus OVD
Score 1	11 (91.7)		Z=3.276; P=0.001*
Score 2	1 (8.3)	9 (75.0)
Score 3		3 (25.0)
Total	12 (100.0)	12 (100.0)
Median	1.00	2.00
IQR	1.00–1.00	2.00–2.75

*P<0.05 significant, Wilcoxon signed-rank test. IQR: Interquartile range, CD: Complete denture, OVD: Overdenture

Stability score of single-implant-retained overdentures (median = 2.00; IQR: 2.00–2.00) was higher than that of conventional complete dentures (median = 1.00; IQR: 1.00–1.00) [Table 4].

Table 4.

Stability score

Scoring	CD, n (%)	OVD, n (%)	CD versus OVD
Score 0	2 (16.7)		Z=3.357; P=0.001*
Score 1	10 (83.3)	1 (8.3)
Score 2		11 (91.7)
Total	12 (100.0)	12 (100.0)
Median	1.00	2.00
IQR	1.00–1.00	2.00–2.00

*P<0.05 significant, Wilcoxon signed-rank test. IQR: Interquartile range, CD: Complete denture, OVD: Overdenture

Patient satisfaction

OHIP questionnaire is a universally accepted, reliable method for evaluating patients' satisfaction levels. The patient satisfaction OHIP scores in this study were higher for single mandibular implant overdenture [Table 5]. The mean score of conventional dentures was 41.00 ± 7.758 SD with P < 0.001, and that of single-implant overdenture was 22.33 ± 4.830 with P < 0.001. Total OHIP scores of single-implant-retained overdenture (median = 22.50; IQR: 18.25–25.50) was lower than that of complete denture (median = 42.00; IQR: 34.50–47.50), with a paired t-test difference of 18.667 ± 5.33, P < 0.001, and t-test value 12.129, which signifies a higher level of satisfaction with single-implant overdenture in comparison to conventional complete denture [Table 6].

Table 5.

OHIP-14 score according to patient responses

Question	CD					OVD					Z	P	CD median	OVD median	CD IQR	OVD IQR
	1	2	3	4	5	1	2	3	4	5
Q1	1	4	6	1	-	3	9	-	-	-	2.887	0.004*	3.00	2.00	2.00−3.00	1.25−2.00
Q2	2	2	7	1	-	6	6	-	-	-	2.667	0.008*	3.00	1.50	2.00−3.00	1.00−2.00
Q3	-	3	7	2	-	4	8	-	-	-	3.066	0.002*	3.00	2.00	2.25−3.00	1.00−2.00
Q4	-	1	7	4	-	5	7	-	-	-	2.980	0.003*	3.00	2.00	3.00−4.00	1.00−2.00
Q5	-	2	6	3	1	5	7	-	-	-	2.980	0.003*	3.00	2.00	3.00−4.00	1.00−2.00
Q6	1	1	5	4	1	5	5	2	-	-	2.850	0.004*	3.00	2.00	3.00−4.00	1.00−2.00
Q7	-	3	5	4	-	4	6	2	-	-	2.879	0.004*	3.00	2.00	2.25−4.00	1.00−2.00
Q8	-	3	5	3	1	5	6	1	-	-	2.877	0.004*	3.00	2.00	2.25−4.00	1.00−2.00
Q9	-	4	3	4	1	5	6	1	-	-	3.025	0.002*	3.00	2.00	2.00−4.00	1.00−2.00
Q10	-	5	4	3	-	5	6	1	-	-	2.565	0.010*	3.00	2.00	2.00−3.75	1.00−2.00
Q11	1	2	6	3	-	8	4	-	-	-	2.836	0.005*	3.00	1.00	2.25−3.75	1.00−2.00
Q12	1	2	8	1	-	7	5	-	-	-	2.889	0.004*	3.00	1.00	2.25−3.00	1.00−2.00
Q13	-	4	7	1	-	5	7	-	-	-	2.889	0.004*	3.00	2.00	2.00−3.00	1.00−2.00
Q14	2	4	4	2	-	8	4	-	-	-	2.913	0.004*	2.50	1.00	2.00−3.00	1.00−2.00

*P<0.05 significant, Wilcoxon signed-rank test. IQR: Interquartile range, CD: Complete denture, OVD: Overdenture

Table 6.

Total oral health impact profile 14 score

Group	Mean OHIP14	Median	±SD	IQR	Mean difference	t	P
CD	41.00	42.00	7.758	34.50–47.50	18.667±5.331	12.129	<0.001**
OVD	22.33	22.50	4.830	18.25–25.50

**P<0.001 highly significant, paired t-test. SD: Standard deviation, OHIP14: Oral health impact profile, IQR: Interquartile range, CD: Complete denture, OVD: Overdenture

Statistical analysis

The masticatory efficiency and patient satisfaction of each participant with conventional dentures and implant-retained overdentures were compared sequentially using the paired t-test. Wilcoxon signed-rank test was used to determine the clinical performance, including retention and stability of conventional dentures and implant-retained overdentures. Normality of data was tested using Shapiro–Wilk test. The IBM SPSS Statistics for Windows, version 23.0 (IBM Corp., Armonk, N.Y., USA) was used to analyze the data with a significance level of 5%.

DISCUSSION

The prospective clinical study investigated the masticatory efficiency, clinical performance, and patient satisfaction of single-implant overdenture. Conventionally, there are various methods used for evaluating masticatory efficiency, which include the sieve method, the use of color-changing chewing gums, and subjective methods such as questionnaires.[21,22] Schimmel et al., for the first time, introduced the chewing gum Hubba Bubba, available in different colors.[23,24] In this study, “raspberry-flavored azure blue” and “original pink” Hubba bubba gums were used.[23,24,25] Schimmel et al. first introduced and validated the software ViewGum, a free and semi-automatic software computer program that is a good adjunct for studying masticatory efficiency with better speed and convenience.[23,24,25] This study compared the masticatory efficiency of a conventional denture and single-implant overdenture depending on the ability of bolus formation and color mixing using the two-colored chewing gum and software ViewGum. The statistical paired t-test analysis showed that the mean-VOH score was higher for complete dentures compared to single-implant overdenture, agreeing with the previous studies and concluding that masticatory efficiency was significantly improved in single-implant overdenture.

The clinical performance of the denture and overdenture was assessed by comparing the values for retention and stability using a digital force gauge which was tabulated as per CU modified Kapur's criteria.[20,27,28] The study results showed a significant improvement in retention and stability concerning single-implant-retained overdenture compared to conventional complete dentures.

In a similar study, two-implant overdentures were compared to conventional dentures by Burns et al. They stated that, even though conventional denture is a successful therapy, it might be possible to raise the level of clinical success for procedures with the implant-retained overdenture.[20,28] The implant overdenture can offer much higher retention and stability than would otherwise be attainable with effective conventional treatment.[20]

A recognized and helpful method for describing patient satisfaction is OHRQoL. The OHIP gives a subjective picture of the discomfort and disability of the patient.[29,30,31] This study used OHIP-14 to assess OHRQoL. Patient satisfaction scores with single mandibular implant-retained overdenture were highly significant compared to conventional dentures 15 days postinsertion. Follow-up was done at the end of the 1^st and 3^rd months to assess patient satisfaction, and the patients reported improved quality of life.[30,31]

The fact that gum tends to adhere to the acrylic denture base is one limitation of the study. Coating a thin layer of petroleum jelly on the polished surface of the denture before chewing improved this to a small extent. This study had follow-ups at the end of 15 days and 3 months. The study by Schimmel et al. stated that patients' adaptation pattern to masticatory efficiency is time dependent; therefore, longer follow-ups are required to assess clinical performance and patient satisfaction.[24] While the present study is a preliminary report or early evidence from a long-term study where the same patient will be assessed for various parameters for conventional removable, complete dentures and single-implant overdentures for at least 2 years. Therefore, the limited follow-up period for the present report is a limitation of the study and needs a further long-term study to assess the parameters with a larger sample.

CONCLUSION

Within the constraints of the study, it can be stated that a single-implant overdenture can be regarded as an effective treatment option for patients who are completely edentulous. It has a higher rate of clinical success than a conventional complete denture and is more affordable than an overdenture with two or more implants. The study has shown that masticatory efficiency improved with single-implant overdenture with better color mixing of two-colored chewing gum and bolus formation compared to conventional dentures. Improvement in clinical performance enhanced the patient's ability to adapt to the prostheses, gradually leading to overall progress in the quality of life and patient satisfaction.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.