REVIEW ARTICLE

https://doi.org/10.5005/jp-journals-10019-1336
International Journal of Prosthodontics & Restorative Dentistry
Volume 11 | Issue 4 | Year 2021

Effect of Two Different Impression Techniques on Masticatory Performance of Complete Denture Wearers: A Systematic Review

Nachammai Nagarajan1, Bappaditya Bhattacharjee2, Ankita Singh3, Atul Bhatnagar4

1-4Faculty of Dental Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Corresponding Author: Atul Bhatnagar, Faculty of Dental Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India, Phone: +91 7080866678, e-mail: atuldent@hotmail.com

ABSTRACT

Aim and objective: The aim of this review was to evaluate the efficacy of the masticatory performance of the complete dentures. The objective of this review was to evaluate scientific evidence of the impact of simplified impression technique versus conventional impression technique on masticatory performance of complete denture wearers.

Materials and methods: Three electronic databases (PubMed, Web of Science, and Cochrane library) were searched until 30th October 2020, without any publication year limit. Manual search of the references cited in the included studies and gray literature were also included. Randomized clinical trials that assessed objectively the masticatory performance between complete dentures fabricated from two different impression techniques were included.

Results: A total of 398 studies were obtained through search in 3 electronic databases (PubMed- 229, Web of Science- 155, and Cochrane library- 14). Qualities of randomized controlled clinical trials were assessed by Cochrane’s tool for Systematic Reviews of Interventions. Heterogeneity of data and measurement methods between the studies limited the scope of their meta-analysis. Nine studies remained after the removal of duplicates and screening of titles and abstracts. Applying eligibility criteria remainder three randomized controlled clinical trials were included after removing six studies.

Conclusion: No significant difference was found objectively in masticatory performance of individuals wearing complete dentures fabricated either by simplified impression technique or conventional impression technique.

How to cite this article: Nagarajan N, Bhattacharjee B, Singh A, et al. Effect of Two Different Impression Techniques on Masticatory Performance of Complete Denture Wearers: A Systematic Review. Int J Prosthodont Restor Dent 2021;11(4):191-197.

Source of support: Nil

Conflict of interest: None

Keywords: Complete denture, Masticatory performance, Simplified impression

INTRODUCTION

Life expectancy has increased with resultant growing number of geriatric population in the recent times owing to the better availability of medical and health facilities. Literature suggests a direct relationship between aging and tooth loss.1,2 Teeth loss is associated with poor masticatory efficiency leading to difficulties in chewing different types of food items, particularly hard food stuffs, this inadvertently leads to inadequate nutrient intake, and weight loss, which is a factor in frailty.3-5 Oral rehabilitation of edentulous patients, is of utmost importance to their overall health and quality of life.

The treatment options for complete edentulism have been extensively studied over the past decades. It is documented that conventional complete denture (CCD) wearers have reduced chewing efficiency of up to 12-30% as compared to dentate individuals.6-19 Use of implant supported dentures for mandibular arches are common improvements compared to CCDs as far as patient satisfaction is concerned but implant treatment modality is comparatively costly.10,11 Conventional complete dentures are still the most sought after treatment modality for complete edentulism, and probably their need will remain for years to come.5,11 The premise that complicated and elaborate procedures are more successful lacks evidence base and are being frequently questioned. Functional ability of complete dentures is largely dependent on accurate recording and reproduction of intraoral surface details. For complete denture fabrication it may be noticed that there is hint of global shift towards novel and simpler approach to techniques and procedural steps. Simplified impression techniques are being used in recent times. Simplified impression is generally known as a technique in which impression is made by using a single impression material in a custom modified stock tray. Step of fabricating custom tray for making final impression is generally not followed in simplified impression in comparison to conventional impression technique.12-15

Recent randomized clinical trials have been conducted with an objective to evaluate the influence of impression techniques on functionality of prosthesis.9,16-21 One of the main goals of complete denture fabrication is rehabilitation of functional parameters like masticatory ability and masticatory efficiency.22-27 Numerous factors such as salivary secretion, tongue motor skill, the height and shape of the residual alveolar ridge, and the stability and retention of the complete dentures influences the masticatory function.3,28 Mastication can be assessed by two main approaches- one is clinical comminution test of food measurement and other by investigating through interviews and questionnaires. Colorimetric method is another newer approach to evaluate the masticatory performance objectively by using materials which can change color after chewing. Different color indicator dyes are generally used in this method. Masticatory ability is defined as individual’s own assessment of masticatory function, whereas masticatory performance is a measure of the comminution of food attainable under standardized testing conditions. The overall capacity to reduce food during mastication is known as masticatory efficiency.29 The aim of present systematic review was to evaluate the efficacy of complete dentures, in relation to masticatory performance, fabricated by employing simplified and conventional impression techniques.

MATERIALS AND METHODS

Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines were employed and a checklist was followed for current systematic review.30

Focused question: “Do simplified impression technique show better masticatory performance compared to a conventional impression technique in a complete denture wearer?”

Inclusion and Exclusion Criteria

Eligibility criteria were set according to the patient, intervention, comparator, outcome, studies (PICOS) model before the literature search (Table 1).

Table 1: PICOS strategy
Elements Contents
Population (P) Completely edentulous individuals.
Intervention (I) Complete denture fabricated using one-step impression technique.
Comparator (C) Complete denture fabricated using conventional two-step impression technique and border molding.
Outcome (O) Objective evaluation of masticatory performance.
Study design (S) Clinical trials, prospective and retrospective studies, In-vivo studies.

The inclusion criteria were:

  • Published articles which compared two different impression techniques in completely edentulous individuals

  • Published articles which evaluated masticatory performance of completely edentulous individuals through objective method

  • Randomized control clinical trials

  • Prospective and retrospective studies

  • In-vivo studies.

The exclusion criteria were:

  • Animal studies, in vitro studies, literature reviews

  • Case reports and case series

  • Published articles in nonenglish languages

  • Studies with incomplete data.

Outcome Measures

Comparison of Masticatory performance of completely edentulous individuals wearing complete denture fabricated by conventional two-step impression technique and simplified impression technique through objective methodology.

Search Strategy

A comprehensive search was done with no publication year limits by two independent reviewers (N.N., B.B.). Following electronic databases were searched for published studies- PubMed, Web of Science, and Cochrane library. In addition to this manual search for references mentioned in the included studies and manual search of gray literature was also carried out. Keywords and MeSH terms used during literature search were “Masticatory performance,” “complete denture,” “complete edentulism,” “impression method,” and “Dental impression technique.” Boolean operators (OR, AND) were used in combination with the keywords to search published studies. Combination of search terms used during literature search were:

  • “Masticatory performance” AND “complete denture”

  • Masticatory performance” AND “complete edentulism”

  • “Masticatory performance” AND “complete denture” AND “dental impression technique”

  • Masticatory performance” AND “complete edentulism” AND “dental impression technique”

  • Masticatory performance” AND “complete denture” AND “dental impression technique” OR “impression method”

  • Masticatory performance” AND “complete edentulism” AND “dental impression technique” OR “impression method”

Data Extraction

The data was extracted by two independent reviewers (N.N., B.B.) from all the included studies and filled into predetermined forms. From each study, following data was obtained: study design, publication year, country, sample size, sample gender, sample age, intervention,and follow-up period. Any disagreements between the reviewers were solved through discussion.

Risk of Bias and Quality Assessment

Recommendations of the Consolidated Standards of Reporting Trials statement (CONSORT) were used for assessing the risk of bias across the included studies.31 Assessment of risk of bias for individual study was carried out using the Cochrane’s tool for Systematic Reviews of Interventions.32 The domains were assessed: sequence generation, allocation sequence concealment, blinding, incomplete outcome data, selective outcome reporting, and other sources of bias. Bias score low, unclear or high was used to assess the overall risk of bias in each study. The risk of bias was scored as "no" to indicate a high risk of bias, "yes" to indicate a low risk of bias and "unclear" to indicate either a lack of information or uncertainty over the potential risk of bias. The extracted data was stratified and tabulated according to chronological order. Information relating to various characteristics of the included studies was described in a summary like format.

RESULTS

Study Selection

Literature search of electronic databases retrieved a total 398 studies (PubMed- 229, Web of science- 155, and Cochrane library- 14). Among all the studies, 83 duplicate records were removed. A total of 306 studies were removed after screening title and abstracts. Total nine studies were included for full text reading.9,16,18,20,33-37 Among nine studies, three randomized controlled clinical trials which assessed masticatory performance objectively by colorimetric assay were included for qualitative analysis.9,33,34 Six studies were excluded due to various reasons listed in (Table 2).16,18,20,35-37 Study selection procedure was conducted by two independent reviewers (BB, NN). Disagreements between the reviewers were resolved through discussion. Study selection procedure has been shown in Flowchart 1.

Table 2: List of excluded studies
Study Reason of exclusion
Heydecke et al.,200835 Patient’s ratings were obtained through visual analogue scales for the masticatory ability and other amenities.
Regis et al.,201318 Employed Oral Health Impact Profile for edentulous (OHIP-EDENT) instrument for assessing oral health related quality of life (OHRQoL) and masticatory performance.
Jo et al.,201536 General patient satisfaction measured using visual analogue scales and OHRQoL measured using the OHIP-EDENT-J questionnaire scores.
Nuñez et al.,201520 OHRQoL measurements made by OHIP-Edentulous scale and assessed patient’s perception in relation to overall satisfaction through visual analogue scale.
Kawai et al.,200516 Assessments of patient satisfaction, OHRQoL and problems associated with the dentures were done through telephone interviews and using a standardized flow sheet.
Lira-Oetiker et al.,201837 Overall patient satisfaction assessed by means of numerical rating scale.

Flowchart 1: Study selection process

Quality Assessment

Qualities of randomized controlled clinical trials were assessed by Cochrane’s tool for Systematic Reviews of Interventions.32 Two of the three included trials mentioned allocation concealment and adequate sequence generation procedure during randomization.9,34 Blinding procedure was clearly mentioned in all the studies. All the studies measured prespecified outcome criteria and mentioned exclusion of patient with proper reasoning. Overall two of the included studies had low risk of bias and one had unclear risk of bias (Table 3).

Table 3: Quality assessment of included studies
Study Adequate sequence generation Allocation concealment Blinding Incomplete outcome data Selective outcome reporting Other risk of bias Overall risk of bias
Cunha et al.,20139 Yes Yes Yes Yes Yes Yes Low
Komagamine et al.,201933 No Yes Yes Yes Yes Yes Unclear
Albuquerque et al.,202034 Yes Yes Yes Yes Yes Yes Low

Study Description

Included studies in the review compared masticatory performance using different colorimetric assay in different follow-up periods. Two parallel armed clinical trials and one crossover trial fromtwo2 different countries were included in this systematic review. Different artificial colored test food were used during mastication in the included studies like polyvinyl acetate capsule containing fuchsine beads, yellowish green chewing gum containing xylitol, citric acid, and dyes.9,33,34 All included studies used colorimetric measurement to assess the masticatory performance. All the included studies used a similar simplified impression technique by using irreversible hydrocolloid in stainless steel stock tray. In conventional impression technique three different types of impression materials (zinc-oxide eugenol, polyether, and silicone) were used in three different studies. Facebow was not used in simplified impression group in one study, apart from this occlusal form, material of teeth, condylar inclination of articulators were same in both the groups in all studies. Characteristics of the included studies are presented in (Table 4).

Table 4: Characteristics of the included studies
Study Study design Country Sample description Impression techniques used Follow-up period
Cunha et al.,20139 Randomized controlled clinical trial Brazil Forty two edentulous patients,
Both male and female, age >45 years		 Edentulous participants were randomly allocated into two groups- Group S and Group C.
Group S received new dentures made from single preliminary impression technique using irreversible hydrocolloid. Impressions were taken in metallic stainless steel stock trays containing wax modified borders (utility wax).
Participants of group C undergone another additional step for final impression. Zinc-oxide eugenol was used as a final impression material in a custom tray.		 Three months after insertion
Komagamine et al.,201933 Randomized controlled crossover clinical trial Japan Twenty seven edentulous patients,
Both male and female, age >55 years		 The conventional method (C) used a border molded (two red and green stick compounds) self-cure acrylic custom tray and silicone impression material. The simplified method (S) used a stock tray and alginate.
Participants were randomly divided into two groups. In C-S group, conventional method was used firstly followed by simplified method and the order was reversed in the S-C group.		 ne month after denture insertion
Albuquerque et al.,202034 Randomized controlled clinical trial Brazil Fifty two edentulous patients, age >45 years Participants were randomly divided into two groups according to impression technique used to obtain the mandibular work cast.
One group received simplified impression with irreversible hydrocolloid in stainless steel stock trays containing modified borders with utility wax.
Other group received secondary impression with polyether in custom tray made up of self-cure acrylic tray. Border molding was done with green stick compound.		 Three and 6 months after denture insertion

Cunha et al.9 evaluated masticatory performance after 3 months of denture fabrication by colorimetric and questionnaire based methods. Chewing a hyperboloid silicone-based test food for 30 seconds was a preliminary step for adaptation. After 3 minutes in the next step participants chewed a capsule of polyvinyl acetate containing fuchsine beads for 20 cycles. Three minutes after that again same task was done for 40 cycles. Resultant solution was filtered. Fuchsine concentration (mg/mL) was measured through spectrophotometer. The capsule was opened and dissolved it in distilled water. There was no significant difference between the groups of edentulous patients, in terms of mean fuchsine concentration and respective 95% confidence intervals (CI) regardless of number of masticatory cycles.

Komagamine et al.33 evaluated masticatory performance by instructing the participants to chew a color-changing chewing gum (thickness of 1.5 mm) gum 60 times freely, at a rhythm of chewing once per second. Cross-over design with washout period of 1 month was used in this study to minimize the effect of patient related variables. After chewing L,*a,* and b* values of colored chewing gum were measured with colorimeter applying CIECLB color system at the five different points; the centre, and approximately 3 mm above, below, and to the right and left of the centre. In addition to this occlusal contact area and occlusal force of the patients were also evaluated by scanning device. Perceived chewing ability was measured by questionnaire-based approach using different food items. No significant difference was found in terms of masticatory performance (= 0.357) and in terms of chewing ability and occlusal surface area between two groups. Occlusal contact areas were significantly more in conventional group.

Third study by Albuquerque et al.34 assessed masticatory performance 3 and 6 months after denture insertion by using colorimetric method using yellowish-green chewing gum containing xylitol, citric acid and red, yellow, and blue dyes. Progression of chewing was indicated by changing of color into red. Participants chewed the gum a total of 40 masticatory cycles at an interval of 3 minutes. Score was obtained by using scale containing 10 distinct colors and choosing a closest color from the scale. Results showed that masticatory performance between groups was similar in both periods (3 months: p = 0.62; 6 months: p = 0.61) and stable in both evaluations (SI: p = 0.93; TI: p = 0.59).

DISCUSSION

This scientific evidence-based systematic review was aimed to review the effect of impression procedures on masticatory performance in treatment of edentulous patients. As an objective methods of assessment have less interexaminer and interparticipant variability than subjective assessment, studies that used objective methodology for assessment of masticatory performance were included in the review. In all the included studies impression technique was different in between test and control groups. There were variations in terms of used materials for prosthesis and demographic characteristics of the participants in between the studies but primary inclusion criterion of the review was usage of two different impression techniques.

Adaptability and psychological acceptance of the patients are major influencing factors for success of any removable complete dentures. Although no significant difference was found in one study in between the groups in terms of masticatory performance, some participants of simplified impression group showed better ability to feed than the other participants.9 No specific relationship found in between the choice of impression material and this finding. According to the authors adaptability of the participants and selection of food items may have a role which influenced the results of the study.9

There was no difference found between the groups during assessment of masticatory performance in another study in which a relatively rigid impression material (polyether) was used in the secondary impression stage.34 Masticatory time to complete chewing cycles was increased in the follow-up period in case of conventional group. Although in terms of masticatory performance simplified impression technique showed promising results but there were increased looseness of mandibular complete dentures during the follow up period. Two mandibular complete dentures had to be relined after installation due to improper tissue-denture base contact. Preciseness of tray modification and flow of the impression material have to be controlled to get an adequate border extension if we use stock tray in any single impression technique for completely edentulous patients. Inadequate peripheral seal and tissue contact of denture bases can lead to remake of dentures which can lead to poor adaptability of the prosthesis.

Komagamine et al.33 employed a cross-over study design which was different from the two other included studies. Other two studies used parallel arm design in which results might be influenced by some patient-related variables like adaptability, resistance of mucosa to external forces, residual ridge quality. Dummy silicone-based secondary impression was made in simplified impression group to maintain a blinded protocol for the participants. Masticatory performance assessed by ability of mixing food and perceived chewing ability. Follow-up time of the participants was reduced because of increased appointment number and cross-over study design. Included participants had different degree of resorbed ridge which may have modified the stability of denture thereby influencing the masticatory performance.

Several studies have been done on simplified complete dentures by omitting several fabrication steps but studies investigating the effect of impression procedure on masticatory performance are few. According to a previous systematic review, Regis et al.18 suggested that two-step impression procedures may not be mandatory for the success of conventional complete denture fabrication in relation to clinical aspects of denture quality and patient’s perceptions. However, the included studies in this review had other confounding factors (facebow transfer, remounting procedure, selection of articulator) apart from difference in impression techniques. Various studies on simplified complete denture have concluded that there is no significant difference in masticatory function of complete dentures fabricated from two impression techniques based on patient’s perception and Oral Health Related Quality of Life (OHRQoL). Ten-year follow-up of randomized controlled study by Kawai et al.16 indicated that simplified method of complete denture fabrication was more cost-efficient than that of conventional technique.

A randomized crossover trial by Heydecke et al.35 also approved that the simplified denture fabrication method outstands the traditional technique in terms of the patient satisfaction ratings also. Similarly, Lira-Oetiker et al.37 showed no significant difference in terms of patient satisfaction and denture quality evaluated between simplified and conventional techniques. Likewise, Nuñez et al.20 identified patient’s perception of treatment outcomes to be similar between the simplified and conventional protocol.

Limitations of present review were low number of randomized clinical trials in accordance to the inclusion criteria and articles were only in English language. Although only three studies were found to be eligible for inclusion in this systematic review, they were randomized controlled clinical trials, defined by the National Health and Medical Research Council (NHMRC) guidelines as level of evidence II.38 Heterogeneity of data and measurement methods in between the studies limited the scope of meta-analysis of these articles. Inconsistency in terminology usage pertaining to function of mastication observed in one article. One of the included studies used different terms in relation to masticatory functions of the participants in their study (Table 5). As many of terms (chewing ability, mixing ability) do not have any clear definition according to guidelines,39 it may be difficult for the readers to correlate. Although from this review it can be concluded that simplified impression technique showed comparable masticatory performance to conventional impression technique in complete denture wearers. As per knowledge of the authors previous systematic review was conducted on simplified complete denture but importance of impression technique was not evaluated exclusively.40 Only one of the included articles in this review was selected in the previous review and subjective responses were reported more than objective assessment.40 However, in future comparative studies assessing influence of impression techniques on retention, stabilit,y and support of complete dentures must be undertaken. Anatomical variances and patient-related variables and compatibility also must be evaluated before selecting any type of impression techniques for complete denture. Further standardized studies are needed on this topic to generate significant evidence of acceptability and suitability of complete dentures made from simplified impression techniques in terms of masticatory performance tested by objective method.

Table 5: Terminologies used in included studies
Study Terms used in objective Terms used in methodology Terms used in conclusion
Cunha et al.,20139 Masticatory performance, masticatory ability Masticatory performance, masticatory ability Masticatory performance, masticatory ability
Komagamine et al.,201933 Masticatory performance Masticatory performance, mixing ability, perceived chewing ability Masticatory performance, mixing ability, perceived chewing ability
Albuquerque et al.,202034 Masticatory performance, masticatory ability Masticatory performance, masticatory ability Masticatory performance, masticatory ability

CONCLUSION

The present systematic review concluded that there was no significant difference in terms of masticatory performance in between the complete dentures fabricated by simplified impression and complete dentures fabricated by conventional impression method. All 3 included studies found no significant difference in terms of masticatory performance between both the impression techniques through an objective method.

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