Abstract
Objectives
To compare the cost and to evaluate cost-effectiveness of fabricating mandibular complete dentures (CDs) using two different impression methods.
Methods
A crossover randomized controlled trial including 27 edentulous participants was performed. Mandibular CDs were fabricated using two different impression methods, as follows: (i) conventional method using a custom tray border moulded with impression compound and silicone and (ii) simplified method using a stock tray and alginate.
Cost analysis was performed from a clinical practitioner’s perspective. The total cost included labor cost, which was calculated using the time spent by dentists and technicians in fabricating CDs and their hourly wages, and the material costs, which were calculated using purchase prices. To evaluate cost-effectiveness, we used general patient satisfaction as an indicator of effectiveness and calculated the incremental cost effectiveness ratio (ICER). ICER represents the cost per one unit of effectiveness.
Results
The trial was completed by 24 participants. The total cost was 43,904 Japanese Yen (JPY) (330.91 EUR / 395.78 USD) for the conventional method and 39,792 JPY (299.93 EUR / 358.70 USD) for the simplified method, and this difference was statistically significant (p < 0.001). The ICER showed a cost of 633 JPY (4.77 EUR / 5.70 USD) for every one point change in general patient satisfaction.
Conclusions
The results indicated that the total cost of the conventional method was significantly higher than that of the simplified method (p < 0.001).
Clinical significance
The conventional impression method for fabricating mandibular CDs, which took additional 633 JPY (4.77 EUR / 5.70 USD) for improvement of general satisfaction, is supposed to be clinically meaningful 1
1 100JPY = 0.76EUR 100JPY = 0.89USD.
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1
Introduction
Although complete dentures (CDs) are the most common treatment of choice among edentulous patients , they often cause discomfort and difficulty in chewing . This is particularly true for mandibular dentures due to the complex anatomical features in the region that make it difficult to achieve favorable results, even for experienced prosthodontists . Several studies focus on the methods (conventional or simplified) used for the fabrication of CDs . The conventional method, which is called the traditional method by some researchers, includes two dental impressions, where the first is a preliminary impression and the second is the final impression. A face-bow transfer is used to record maxillomandibular relations. Conversely, the simplified method uses a single impression only and does not include a face-bow transfer. Currently, even though most dental schools recommend the use of the conventional method for CD fabrication, available literature suggests that many practitioners still prefer the simplified method due to limited knowledge, increased time, and the cost associated with the alternative . Treatment techniques have greatly developed in most fields, resulting in an increase in the choice of methods available for various clinical treatments. This, in turn, has made the decision-making process more complicated from an individual and political perspective . Practitioners must choose the treatment method considered most appropriate from a medical, social, ethical, and economical aspect, and various meta-analyses and decision analysis reports have attempted to aid them with this . Implementation of new treatment procedures is usually governed by financial considerations, making it necessary for efficacy studies to include cost comparisons . The term “cost-effectiveness” is one that is commonly used in the economic evaluation of healthcare. The idea is to determine whether the intervention of interest provides better results at lower costs compared with the alternative approach , and the results may help practitioners and patients make informed decisions on their treatment of choice .
There have been some comparative studies regarding differences in methods for CD fabrication . In these studies, except that conducted by Omar et al. , the conventional method included twice impressions, a face-bow transfer and a semi-adjustable articulator, and the simplified included a single impression without a face-bow transfer and using a semi-adjustable articulator with standard settings. The studies of Kawai et al. and Regis et al. used the same protocols but different tools to measure the primary outcome. No significant differences in participant ratings for general satisfaction and oral health-related quality of life (OHRQoL) were observed between the two groups. Several randomized controlled trials (RCTs) have performed a cost analysis and concluded that the conventional method was more expensive than the simplified method . Omar et al. conducted a four-armed, double-blinded, randomized trial comparing the two methods, wherein they used the same conventional method for all groups at the clinical phase and omitted select steps during the laboratory phase in three groups. They reported no significant differences in participant ratings for general patient satisfaction between the four groups. However, they did not carry out a cost analysis comparison of the two methods . In their systematic review comparing the same two methods, Paulino et al. reported that the simplified method was more efficient than the conventional method in terms of time and cost, mainly because the latter method yielded the same general patient satisfaction and OHRQoL at a higher cost . A study group in the U.K conducted a crossover RCT where they compared final impressions made from two different impression materials, silicone and alginate . They reported no differences in the clinical procedures between the groups and the conventional method was used in both groups, which includes the final impression made by border moulded individual trays and the face-bow transfer. Hyde et al. reported that using silicone impression material instead of alginate for CD fabrication resulted in significantly higher OHRQoL, although the cost associated with it was also increased . Their analysis showed that the incremental cost-effectiveness ratio of using silicone impression materials for fabrication of CDs was 3.41 Great Britain pound (GBP) per one point of OHIP-EDENT . In their clinical review, Carlsson et al. reported that there was insufficient robust evidence in support of any one protocol for the fabrication of CDs. Moreover, the scientific evidence in support of the need for different combinations of materials and techniques for different clinical situations was also lacking. Previous RCTs have mainly evaluated both maxillary and mandibular CDs, and there are no studies that focus only on mandibular CDs that are known to be problematic .
Previously, we carried out an RCT that compared the two impression methods (conventional and simplified) and found that mandibular CDs fabricated using the conventional method resulted in greater patient satisfaction . As a follow-up to this, our current study aimed to compare the cost and evaluate the cost-effectiveness of the two methods. For the purposes of this study, the simplified method meant only using a single alginate impression, and the conventional method was for making a final impression with a silicone impression in border-moulded custom trays for CD fabrication. There was no difference in the maxillomandibular relation records between the two methods. With a null hypothesis, there would be no difference in the cost between the simplified and the conventional method groups.
2
Materials and methods
2.1
Study design
The protocol for our single-center, blinded, randomized, controlled, crossover clinical trial was approved by the Ethics Committee of the Faculty of Dentistry, Tokyo Medical and Dental University (TMDU) under the register number 946, and was published in the University Hospital Medical Information Network (UMIN) Center (UMIN-CTR Clinical Trial, Unique trial Number: UMIN000009875). Details of the RCT protocol have been reported previously . Allocation to the group C-S and the group S-C was performed based on the classification system for complete edentulism of The American College of Prosthodontists (ACP) with stratified randomization. The conventional method was used on group C-S first, followed by the simplified method. The group S-C underwent the procedures in the reverse order. Blinding of participants was possible as they were not told the order of fabrication or which method was used first (simplified or conventional).
2.2
Participants
The participants were edentulous in both arches, currently used dentures, and required a new pair of CDs. The inclusion/exclusion criteria and sample size estimation of this study were reported in our previous paper . In total, 27 participants were recruited by telephone from patient records of the Dental Hospital, TMDU. All participants gave informed consent, signed a letter of consent, and underwent a preliminary examination, including a panoramic radiographic survey.
2.3
Clinical procedures
The clinical steps of the conventional and simplified methods were the same in this study ( Fig. 1 ). First, a preliminary impression was taken using alginate impression material in a metal edentulous stock impression tray (Schreinemakers metal edentulous impression trays, Clan Dental Products, Maarheeze, Netherlands). Thereafter, custom trays were fabricated using auto-polymerizing resin, which were then border moulded with impression compound and silicone impression material and used to obtain a final impression. In case of the simplified method, the mandibular master cast was made using the first alginate impression, and the second (final) impression was taken only for the purpose of blinding. Thereafter, the two methods were alike in terms of procedures used, including recording of maxillomandibular relations, mounting in an average-value articulator (Gysi simplex OU-H3, COMATSU, Saitama, Japan), denture fitting, and denture delivery. Thereafter, adjustments were carried out four times every week starting from the point of initial delivery. Table 1 shows the materials used in each procedure of this trial.
| Material | Product name | |
|---|---|---|
| Clinical procedure | ||
| Preliminary impression | Alginate | Aroma Fine Plus, GC Corporation, Tokyo, Japan |
| Final impression | Impression compounds | Kerr Impression Compound, Kerr Corporation, Orange, CA, USA |
| Silicone impression material | Exadenture, GC Corporation, Tokyo, Japan | |
| Maxillomandibular relation record | Wax | Paraffin wax, GC Corporation, Tokyo, Japan |
| Delivery & Adjustment | Pressure indicator pastes | DENT-SPOT, Showa yakuhin kako Corporation, Tokyo, Japan |
| Articulating papers | Articulating paper, GC Corporation, Tokyo, Japan | |
| Laboratory procedure | ||
| Study model | Hard plaster | New plastone II, GC Corporation, Tokyo, Japan |
| Custom tray | Autopolymerizing resin | Ostron II, GC Corporation, Tokyo, Japan |
| Occlusal rim | Autopolymerizing resin | Ostron II, GC Corporation, Tokyo, Japan |
| Wax | Paraffin wax, GC Corporation, Tokyo, Japan | |
| Master cast | Super-hard plaster | Vel-Mix Classic stone, KaVo Dental System Japan Corporation, Tokyo, Japan |
| Mounting | Hard plaster | New plastone II, GC Corporation, Tokyo, Japan |
| Arrangement | Artificial teeth | Real Crown anterior, Shofu Corporation, Tokyo, Japan |
| Veracia SA posterior, Shofu Corporation, Tokyo, Japan | ||
| Fabricating denture | Investment material | Advastone, GC Corporation, Tokyo, Japan |
| Heat-curing acrylic resin | Acron, GC Corporation, Tokyo, Japan | |
2.4
Cost analysis
The cost analysis in this study was performed from the perspective of a decision-maker, that is, a clinical practitioner seeking optimal treatment for each patient. In order to calculate the cost of material and labor, we recorded the actions undertaken, disposable materials used, and time taken for each procedure from preliminary impression to 4th adjustment, excluding the dummy impression [ Fig. 1 ]. Both clinical and laboratory procedures were recorded. Time spent by a dentist included setup, treatment, clean up, and chart report writing, while that spent by a dental technician included all laboratory procedures . Materials used for clinical and laboratory procedures were also recorded.
Cost calculation was carried out after completion of the 4th adjustment for both methods, and all costs were calculated in Japanese yen (JPY) [100 JPY = 0.68 GBP in May 2017]. Labor costs were calculated by taking the time spent by the dentist and dental technician into consideration, along with their mean hourly wages which were estimated from the data reported by the Ministry of Health, Labor and Welfare, Japan in 2014. The purchase prices for TMDU Dental Hospital were used to calculate costs of materials.
The Mann–Whitney U test at a significance level of 0.05 was used to compare costs between the two groups. All analyses were performed using SPSS ver.16.0.
2.5
Cost-effectiveness analysis (CEA)
In the CEA, general patient satisfaction was used as indicators of effectiveness. General patient satisfaction was measured using a 100-mm visual analog scale (VAS) . The outcome of the CEA was incremental cost incurred per general patient satisfaction. The results have been presented as ICERs which represent the ratio of the incremental cost to incremental effect, that is, the additional cost per one unit of outcome gained, in this case per general patient satisfaction point gained.
2
Materials and methods
2.1
Study design
The protocol for our single-center, blinded, randomized, controlled, crossover clinical trial was approved by the Ethics Committee of the Faculty of Dentistry, Tokyo Medical and Dental University (TMDU) under the register number 946, and was published in the University Hospital Medical Information Network (UMIN) Center (UMIN-CTR Clinical Trial, Unique trial Number: UMIN000009875). Details of the RCT protocol have been reported previously . Allocation to the group C-S and the group S-C was performed based on the classification system for complete edentulism of The American College of Prosthodontists (ACP) with stratified randomization. The conventional method was used on group C-S first, followed by the simplified method. The group S-C underwent the procedures in the reverse order. Blinding of participants was possible as they were not told the order of fabrication or which method was used first (simplified or conventional).
2.2
Participants
The participants were edentulous in both arches, currently used dentures, and required a new pair of CDs. The inclusion/exclusion criteria and sample size estimation of this study were reported in our previous paper . In total, 27 participants were recruited by telephone from patient records of the Dental Hospital, TMDU. All participants gave informed consent, signed a letter of consent, and underwent a preliminary examination, including a panoramic radiographic survey.
2.3
Clinical procedures
The clinical steps of the conventional and simplified methods were the same in this study ( Fig. 1 ). First, a preliminary impression was taken using alginate impression material in a metal edentulous stock impression tray (Schreinemakers metal edentulous impression trays, Clan Dental Products, Maarheeze, Netherlands). Thereafter, custom trays were fabricated using auto-polymerizing resin, which were then border moulded with impression compound and silicone impression material and used to obtain a final impression. In case of the simplified method, the mandibular master cast was made using the first alginate impression, and the second (final) impression was taken only for the purpose of blinding. Thereafter, the two methods were alike in terms of procedures used, including recording of maxillomandibular relations, mounting in an average-value articulator (Gysi simplex OU-H3, COMATSU, Saitama, Japan), denture fitting, and denture delivery. Thereafter, adjustments were carried out four times every week starting from the point of initial delivery. Table 1 shows the materials used in each procedure of this trial.
