The duration of finishing and polishing of acrylic removable orthodontic appliances in the Dental Technology Study Program at Universitas Airlangga, Surabaya, Indonesia


Sianiwati Goenharto, Elly Rusdiana, Alif Yansyah

Department of Health, Faculty of Vocational Studies, Universitas Airlangga, Surabaya, Indonesia.

*Corresponding Author E-mail:



Objective: This study was intended to quantify the duration of finishing and polishing of removable orthodontic appliances by Dental Technology Study Program students. Material and Methods: This descriptive observational study employed total sampling. Fifteen of 6th semester students participated in the study, each of them producing three removable orthodontic appliances with the duration of finishing and polishing being recorded. Data was analyzed descriptively. Results: The duration of the finishing and polishing of orthodontic plates by Dental Technology Study Program students varied widely from 9 to 420 minutes with a mean of 71.20 minutes, both between individual students and between the first, second and third orthodontic plates. Conclusion: It is concluded that the duration of finishing and polishing in the fabrication of an orthodontic plate by the students was between 9 and 420 minutes. The duration varied depending on the design of the appliances, the skill of the students in processing or when performing the finishing and polishing.


KEYWORDS: Orthodontic appliances, Finishing, Polishing, Acrylic dust, Dental technician.




Removable orthodontic appliances consist of active components, retentive components and acrylic plates1. The baseplate performs several functions, such as perpetuating the strength of the active component to anchorage, blocking unwanted tooth shift and protecting the palatal spring. It can be modified to produce anterior and posterior bite planes2. Since ages, polymethyl methacrylate (PMMA) has been used in dentistry3. Acrylic orthodontic plates are generally made from cold cured acrylic material. Compared with the heat cured variety, cold cured acrylic is more economical and less time-consuming. Cold cured acrylic consists of monomer liquid that consists of methyl methacrylate (MMA) and polymer powder that consist of PMMA4. MMA monomer is flammable, colourless and transparent with a sharp and pervasive odour. Various case studies have reported that MMA causes lung, skin and eye irritation5.


Dental technicians can potentially be exposed to harmful substances, one possible risk being caused through the inhaling of dust that may contain toxic substances6. Dust is routinely produced during the process of making removable orthodontic appliances. After the acrylic has set, finishing and polishing with the abrasive material is carried out. The resulting dust can endanger health, pneumoconiosis being one example of this risk7. 
Dental technicians need to exercise caution in anticipating the potential negative impact of their contact with dust by minimizing its duration. Research into the degree of exposure to dust that a dental technician might experience when manufacturing a removable orthodontic appliance, especially when finishing and polishing have yet to be undertaken. The study reported here was conducted to quantify the required duration of finishing and polishing involved in the manufacture of a removable orthodontic appliance.
Ethical Aspects:
This study was approved by Universitas Airlangga Faculty of Dental Medicine Health Research Ethical Clearance Commission (Certificate No: 043/HRECCFODM/V/2018). The subjects were explained about the procedure and asked the informed consent regarding the commencement of this study.
Study Design and Sample:
This descriptive observational study was conducted between March and May 2018 at the Dental Technology Study Program, Universitas Airlangga, Surabaya. The inclusion criteria were orthodontic acrylic plates in any designs made by sixth-semester students of the Dental Technology Study Program. Total sampling was employed, and a group of 15 students participated in the study, each of whom produced three orthodontic acrylic plates. The exclusion criteria were the acrylic plates that broke from processing stage or not an orthodontic plate.
Data collection:
Acrylic processing was conducted after the application of springs and clasps to the dental cast. After that, the model was soaked in water for approximately ten minutes before the separation material (Meliosep, Germany) was applied to the surface of the dental cast. This was allowed to dry before the acrylic processing, involving the use of cold cured acrylic material (Ortho Resin, UK) was carried out with layering or sprinkle technique. At this point, the model was put into a polyclav (Remanium Dentaurum, Germany) filled with water heated to a temperature of 130F / 50℃ at a pressure of two standard atmospheres and left for 30 minutes (6). The acrylic plate was subsequently removed from the dental model and made ready for finishing. The finishing time was calculated through a stopwatch (Casio, Japan). Finishing was performed using a handpiece and micromotor (Saeshin Strong 204, South Korea) incorporating a bur for use on an acrylic material. Finishing was undertaken to reduce the excessively large acrylic area, with the acrylic plate being smoothed with sandpaper. 
Data Analysis:
The polishing process involved the use of a slurry pumice cone and a polishing machine (Silfradent, Italy), followed by brushing with kryte to produce a shiny plate. The finishing and polishing times were recorded. In cases where the finishing and polishing process was not carried out continuously, the interruption was not considered. Data were collected and tabulated by Microsoft Excel software and analyzed descriptively to calculate the mean value.
The duration of the finishing and polishing of removable orthodontic plates is shown in Table 1.  From table 1 it appears that the time required for finishing and polishing 1st, 2nd and 3rd plate have a big variety and also among all students.  The average finishing and polishing time for 3 orthodontic plates was 71.2 minutes. The fastest time was obtained by the 14th student with 9 minutes, while the longest was the 10th student, 420 minutes. of the 1st, 2nd and 3rd plate, the fastest was achieved by the 13th student with a time of 18.35 minutes and the longest was by the 10th students with a time of 217.67 minutes.
Table I. Duration of finishing and polishing of removable orthodontic plates (minutes)


1st plate

2nd plate

3rd plate

Mean (x)













































































Work is an integral part of everyday life8 . Producing product in scheduled time is important to satisfy customer needs9 and time management is needed to enhance the productivity10. Before insertion into the mouth of the patient, the orthodontic plate must be well-polished.  Rough surfaces will render it uncomfortable, while an increase in plaque accumulation and biofilm formation will reduce the sheen of the acrylic plate11. Orthodontic appliances are made from self-cured acrylic with higher porosity and greater surface roughness12. In order to obtain a smooth and shiny acrylic plate, both finishing and polishing are performed. While acrylic polishing can be carried out chemically, the disadvantages of this method include a reduction in mechanical resistance compared to mechanical polishing, adverse effects on resin resistance and structure and a greater degree of deformation13. Therefore, the performance of the procedure on self-cured acrylic plates is contraindicated14. Research also demonstrated that mechanical polishing produces a smoother surface than its chemical equivalent15,16.

Safety is an issue of basic significance in all fields 17 and environmental awareness is a matter of concern18. The mechanical finishing and polishing of acrylic plate produce dust that can endanger health. Based on the results of this study, the duration of a dental technician’s contact with dust when finishing and polishing an orthodontic acrylic plate varies between 9 and 420 minutes. In fact, the calculation of a meantime cannot be considered absolute due to differences in the design of appliances and operators, although the latter had received the same training in the manufacture of a removable orthodontic appliance.
The results indicated that the duration of the finishing and polishing process performed by dental technicians varied. In the case of the first student, the duration of finishing and polishing was 21, 27 and 25 minutes. The time required is relatively short and stable with an average duration of 24 minutes. This relatively short period can be achieved by the skillfulness of the operator performing the finishing and polishing processes. Besides, acrylic processing was conducted effectively with the result that the amount of excess acrylic which increases the finishing time was minimized.
The second student recorded 65, 115 and 45 minutes. These results fluctuated, probably because each job has a different degree of difficulty. In the second acrylic plate, a longer duration of 115 minutes was required. In this case, an error occurred in the installation of the maxillary Coffin spring which lacked symmetry around the median line and whose repair prolonged the finishing time.
With the third student, the duration of finishing and polishing of the second acrylic plate was longer due to the addition of a maxillary Coffin spring. A design incorporating Coffin springs prolongs the finishing and polishing process because it is completed twice, once before and once after the Coffin spring has been installed. In the case of the fifth student, the second acrylic plate underwent extremely lengthy (180 minutes) finishing and polishing. This is because, after polishing, the acrylic plate did not fit into the working model (rocking) and, consequently, had to be remade.
Concerning the ninth student, the average duration of 110 minutes was probably due to the lack of involvement of skilled dental technicians in the finishing and polishing process. For the tenth student, the first plate required 420 minutes. This maximum duration was caused by several factors, including the acrylic plate being of such thickness that it required a protracted finishing time or it being so thin after finishing that the acrylic process had to be repeated. The mean duration of finishing and polishing in the case of the tenth student was the highest of all the samples (217 and 67 minutes). It would appear that this student was less skilled in completing the finishing and polishing process causing it to require a relatively long time.
The thirteenth student recorded the fastest times with an average of 18 and 33 minutes. Due to the skill of the operator, the acrylic processing was completed effectively, efficiently and carefully with the result that the finishing and polishing process could be undertaken more easily. The shortest time was achieved in the case of the fourteenth student, the first acrylic plate requiring only nine minutes. This relatively brief duration was achieved because the procedure was performed on the lower jaw which is comparatively smaller than the upper jaw. 
The results of this study indicate that several factors influence the duration of the finishing and polishing of acrylic plates, such as appliance design and operator skills. The addition of the maxillary Coffin springs prolongs the finishing and polishing process which is divided into two phases: after the acrylic plate has been rendered smooth and shiny, the Coffin springs are added while finishing and polishing is performed on the embedded part. 

Dental laboratory air has a high level of pollution due to grinding dust, especially extraordinarily fine, invisible particles capable of penetrating the lungs and causing severe damage 19. The potential risk is one of inhaling dust during finishing and polishing. This physical hazards can affect  the overall health of workers20. Preventive measures can be taken by providing a workspace of an optimal standard. Dental laboratories must be spacious, clean, have efficient air ventilation and a separate work table for finishing and polishing 21,22.

During finishing and polishing, dental technicians should wear respirable dust masks preventing the inhalation of acrylic dust. The majority of dental technicians persist in using surgical masks even though they prove less useful for respirable dust whose particles are sufficiently small to penetrate them. Also, the use of gloves and glasses is also essential in order to achieve optimal protection 23,24.

It was concluded that the duration of finishing and polishing in the manufacture of an orthodontic acrylic plate by Dental Technology Study Program students ranged between 9 and 420 minutes. The duration varied according to appliance design and the skill of the students when processing or completing the finishing and polishing. Precautions, skill, the speed of working and personal protective equipment are required to minimize the danger of dust causing respiratory diseases.

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Received on 28.04.2020            Modified on 03.02.2021

Accepted on 04.07.2021           © RJPT All right reserved

Research J. Pharm.and Tech 2021; 14(12):6527-6530.

DOI: 10.52711/0974-360X.2021.01128