Introduction

The goals of removable partial denture treatment are to restore esthetics and function, and preserve the remaining oral structures (1-4). To help achieve these goals, the prostheses should be appropriately designed and instructions regarding their construction should be accurately communicated to the dental laboratory technician (5). The important constituents of prosthodontic treatment are the design and prescription of prostheses, which should be implemented with regard to biological and mechanical factors (6). This information should then reach the dental technician in the form of a written work authorization (7). A written work authorization acts as a legal document for both dentists and dental laboratory technicians, and should therefore be decipherable, clear, brief, and easily understood by technicians. Inadequately detailed work authorizations can lead to prostheses that are inappropriately designed and may harm the patients’ remaining oral structures (6, 8).

Findings of previous studies in several countries over the past 30 years indicate shortcomings in the design and fabrication procedures of different types of prostheses in general dental practice, especially cobalt-chromium removable partial dentures (8-15). This has led some countries to stipulate ethical and legal guidelines that require the clinician to adequately design prostheses and communicate these design features to the technician (8). It was hoped that these ethical and legal guidelines would have led to an improvement. However, some studies carried out in the UK and Ireland indicated that the problem still persists (16, 17).

The aim of this study was to investigate the quality of communication between dentists and laboratory technicians regarding removable partial denture construction in Sudan, as there is no clear stipulation that outlines the dentist’s responsibility in authorizing the fabrication of any dental appliance. A study evaluating the quality of communication between dentists and dental laboratory technicians may give indication of improvements that are needed, and might contribute toward better-constructed removable prosthodontic appliances in Sudan.

Materials and methods

This was a descriptive cross-sectional study of cases involving removable partial dentures constructed by registered private dental laboratories that have the facilities to fabricate cobalt chromium RPDs in Khartoum State. Private dental laboratories outside Khartoum State could not be included as no relevant records could be found with the Ministry of Health.

All cases or prescriptions sent to the selected dental laboratories for RPD construction were included in the study while any case or prescription for a prosthetic restoration other than RPD was excluded.

The sample size was determined through the following formula: where n was the sample size, z the confidence interval 1.96, and p was 5.5% on the basis of results from a previous study (12), q was 1-p, and d, the desired margin of error, was 5%. This led to a total sample size of 80. The required sample size of each type of RPD was then calculated, i.e., for cobalt chromium (CC) partial dentures and acrylic (A) partial dentures, according to the total average of cases per month;

n = average of cases (CC)/ month× total sample size

total average of cases (A & CC) / month

Cobalt Chromium RPDs = 26 × 80 = 11 cases

190

Acrylic RPDs = 163 × 80 = 69 cases.

190

This yielded a final sample size of 11 CC-RPD and 69 A-RPD cases. The sample size from each dental laboratory was taken according to the availability of the cases within the laboratory during the time of data collection. A list of private dental laboratories in Khartoum State was obtained from the Ministry of Health. Seven of them had the facilities to fabricate CC-RPDs. The technicians of these 7 dental laboratories were interviewed by the main investigator using a questionnaire enquiring about each of the RPD cases received, and the data were entered into a spreadsheet. The questionnaire was a modified version of the one used by Al-AL Sheikh in Saudi Arabia [13], and consisted of three main sections: section A dealt with data about laboratory & type of prosthesis, section B included information about A- and CC-RPDs, while section C only pertained to data regarding CC-RPDs.

The questionnaire contained questions about 4 design components for A-RPD and 8 design components for CC-RPD. The design components for A-RPD were the teeth to be clasped, the shade of artificial teeth, the form of posterior teeth, and the posterior palatal seal. The design components for CC-RPD were the same as those for A-RPD in addition to the type of major and minor connectors, the position of the rests, and the position of the indirect retainer.

In order to evaluate the instructions accompanying RPD cases, the instructions were classified as clear, guided, poor, and none (no instruction) according to the number of design components mentioned: clear {4 (A-RPD) \7-8 (CC-RPD) design components mentioned}, guided {2-3 (A-RPD)\4-6 (CC-RPD) design components mentioned}, poor {1 (A-RPD)\1-3 (CC-RPD) design components mentioned}, and none {no design variable mentioned}. This classification was modified from that used by Lynch et al in Ireland and the UK (8). Descriptive statistics including frequency distribution tables as well as graphs were used. The Fisher exact test was used to test the difference between two groups (A-RPD and CC-RPD). SPSS version 17.0 was used for entering and analyzing the data. The aim of the study was explained to the participants before commencing the study. Approval letters from the Ethical Committee of the Faculty of Dentistry, University of Khartoum were obtained before conducting the study. Written informed consent was obtained from all laboratories that participated in the study and data protection was assured.

Results

Nineteen technicians participated in the study. They constructed 80 RPDs prescribed by dentists, of which 69 cases (86.25%) were A-RPDs and 11 cases (13.75%) were CC-RPDs. Technicians received instructions, either verbal or written, from dentists in 78.3% (54 cases) of the A-RPD cases and in all of the CC-RPD cases (11 cases). Verbal instructions were obtained in 55.1% (38 cases) and written instructions in 23.2% (16 cases) of A-RPD cases, while verbal instructions were obtained in 54.5% (6 cases) and written instructions in 45.5% (5 cases) of CC-RPD cases. It is important to note that most of the technicians, 84.2% (16 cases), believed that the design of prosthesis is the responsibility of the dentist, and only 15.8% (3 cases) thought that the design of prosthesis is the technician’s responsibility. In this study, technicians were asked to design the prosthesis in 20.3% (14 cases) of A-RPD cases but in none of the CC-RPD cases. Dentists discussed the design of the case with technicians in 24.6% (17 cases) of A-RPD cases and in 45.5% (5 cases) of CC-RPD cases. It was necessary for technicians to contact dentists for clarification of the design in 14.5% (10 cases) of A-RPD cases and 54.5% (6 cases) of CC-RPD cases. In 69 cases involving acrylic partial dentures, dentists did not indicate which teeth needed to be clasped in 47 (68.1%) cases; did not specify tooth shade in 30 (43.5%) or posterior tooth form in 56 (81.2%) of cases; and did not draw the posterior palatal seal in 24 (34.8%) of necessary cases (Table 1)

Concerning the 11 cases involving cobalt chromium partial dentures, dentists did not indicate the teeth to be clasped in 2 (18.2%) cases; selected the tooth shade in all cases, specified the posterior tooth form in only 2 (18.2%) cases; and did not draw or carve the necessary posterior palatal seal in only one case. Furthermore, the types of major connectors were determined in 7 (63.6%) cases, types of minor connector in 3 (27.3%) cases, the position of rests in 9 (81.8%) cases, and positions of indirect retainers in 5 (45.5%) cases (Table 1). For both acrylic and cobalt chromium partial dentures, technicians stated that patients’ age was mentioned in 18.8% (13 cases) of A-RPD and 54.5% (6 cases) of CC-RPD cases; patients’ gender in 37.7% (26 cases) of A-RPD and 72.7% (8 cases) of CC-RPD cases; return date in 64.7% (44) of A-RPD and 81.8% (9) of CC-RPD cases; and design diagram in 10.1% (7 cases) of A-RPD and 45.5% (5 cases) of CC-RPD cases; surveying was done by the dentist in only 18.2% (2 cases) of the CC-RPD cases (Table 2). The tooth preparations were performed in all of CC-RPD cases. Instructions given by dentists to technicians for A-RPD were considered to be clear in 8.7% (6 cases); guided in 20.3% (14 cases); poor in 34.8% (24 cases); and absent in 36.2% (25 cases) of cases (Figure 1). Similarly, instructions received by the technician with regards to CC-RPD were clear in 36.4% (4 cases), guided in 45.5% (5 cases), poor in 18.2% (2 cases) of CC-RPD cases (Figure 2). When comparing the results of A-RPD and CC-RPD cases using the Fisher’s exact test, the only significant association (p=0.004) was with the technician needing to contact the dentist for clarification of the design (Table 2).

Figure 1 Quality of instructions for A-RPD according to the number of design components

Figure 2 Quality of instructions for CC-RPD according to the number of design components

Discussion

The results of this study showed that A-RPDs were more commonly prescribed than CC-RPDs. These results are consistent with those of Radhi et al (12). These findings are disappointing as CC-RPDs are more proficient in maintaining oral health than A-RPD, and the latter may even have harmful effects on the oral tissues (10, 18, 19). Reasons for the frequent prescription of A-RPD may be the high financial cost of CC-RPD and lack of educational or clinical experience in constructing CC-RPD (13). Based on the number of design components, most of the A- and CC-RPD instructions in the current study were not considered clear. This is comparable to observations by other authors (8, 12-14, 16, 17, 20-22). This might be a reflection of inadequate communication between dentists and dental technicians, based on dentists relying on the dental technicians to construct the prostheses. Alternatively, it could be due to weak undergraduate training in writing laboratory instructions and designing RPDs. Less than a quarter of A-RPD and less than half of CC-RPD cases came with written instructions, more than those found by Neto et al (23).

Written instructions are important to technicians as they might forget the details of instructions if they were given to them only verbally. Another advantage of written instruction is that they can be considered a legal document (24). Verbal communication may be useful when technicians need additional information or clarification. In such circumstances, the importance of discussing the case face to face or over the telephone cannot be ignored (25).

Most of the technicians believed that the design of the prosthesis is the responsibility of the dentist, contrary to findings by Haj-Ali et al (15). The technicians needed to contact the dentist in only a few of the A-RPD cases but in nearly half of the CC-RPD cases. In the present study, the dentists discussed the design of the case with the technicians face to face only in approximately a quarter of A-RPD cases and about half of CC-RPD cases, similar to the results by Al-Alsheikh (14). This indicates that much more effort is needed to improve communication between dentists and technicians in order to enhance prosthodontic services.

Technicians were asked to design the prosthesis in about a fifth of A-RPD cases and had not been asked to design any CC-RPD case, which is comparable to observations by Lynch et al [17] but differs from other studies [8,13,23]. It is possible that dentists put a greater emphasis on CC-RPD instructions than A-RPD instructions because of the high cost of CC-RPDs, or because CC-RPDs were prescribed by dentists who possessed greater skills than those who prescribed A-RPDs. The results of this research showed that most of the design components for A- and CC-RPDs were not clearly prescribed, which again is similar to previous studies (13, 17, 23, 24). This again indicates that dentists leave it mainly to technicians to design the prosthesis, which is unacceptable as the dentists should be fully responsible for the RPD design, since they perform the examination, diagnosis, and treatment planning.

The age of the patient was stated in less than a fifth of A-RPD cases and in nearly half of CC-RPD cases, while patients’ gender was mentioned in almost a third of A-RPD cases and in about three quarters of CC-RPD cases. This revelation is unfortunate, as age and gender are important guides in tooth selection. The return date was mentioned in more than half of A-RPD cases and in most of CC-RPD cases. This is consistent with the results obtained by Al-Alsheikh (14), but conflicts with the results of Carneiro (15). The return date is important to organizational effectiveness of the subsequent appointment for the patient.

The dentists designed a diagram for only a few cases of A-RPD, and for around half of the CC-RPD cases, which is again similar to several studies (8, 12, 14, 22), but different from those by Lynch et al (16). Diagrams should be used more often in order to improve the quality of communication between dentists and dental technicians. A design diagram that is formed after a careful evaluation of the patient, with subsequent surveying and articulation of study casts, can be used as an acceptable work authorization for an RPD design (25).

Surveying of the casts by dentists was implemented in less than a fifth of the CC-RPD cases, which again was comparable to previous studies (8, 14, 22). It is possible that this is a consequence of poor undergraduate training, unavailability of surveyors, or ignorance of the dentists regarding the importance of surveying. Tooth preparations were performed in all of the CC-RPD cases, which may be considered positive as tooth preparations are essential for obtaining a successful treatment outcome (26). Technicians needed to contact the dentist for clarification of design significantly more for CC-RPD (p=0.004), than A –RPD cases. As previously stated by Lynch (8), the design of any prosthesis is based on mechanical and biological principles. Hence, communication between the dentist and dental technician and/or complete information provided with the impression is a very important step because if master impressions are being sent to dental laboratories with inadequate design information, the technician does not have access to crucial information relating to the nature and health (biology) of the periodontal and other tissues. This will reflect negatively on the following steps and may result in damage and injuries to dental and periodontal tissues.

There were some study limitations that should be considered when interpreting the results of this research work. First, the study was based on an interview format that relied on the memory of the technicians for details of the instructions sent with each case, particularly given that the interview was made after the try-in stage of the prosthesis. Likewise, the accuracy of the assessment also depended on the impartiality of the technician. Thirdly, the selection of the dental laboratories in this study was dependent on the existence of facilities for fabrication of CC-RPD. Therefore, the selected dental laboratories might not be representative of all dental laboratories in Khartoum State.

Conclusion

The quality of communication between dentists and laboratory technicians with regard to removable partial prosthodontic appliances was found to be inadequate. Clear guidelines outlining the dentist’s responsibility in authorizing the fabrication of removable denture appliances are necessary to help improve the current situation.