A comparison of patient experience, chair-side time, accuracy of dental arch measurements and costs of acquisition of dental models

Olja Glisic; Louise Hoejbjerre; Liselotte Sonnesen

doi:10.2319/020619-84.1

Editorial Type:

Article Category: Research Article

Online Publication Date: 01 Jul 2019

A comparison of patient experience, chair-side time, accuracy of dental arch measurements and costs of acquisition of dental models

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Page Range: 868 – 875

DOI: 10.2319/020619-84.1

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ABSTRACT

Objective:

To compare patient experience, chairside time, dental arch distances, and costs of dental models derived from intraoral scans and alginate impressions in pre-orthodontic children and young adolescents.

Materials and Methods:

Fifty-nine children and young adolescents (9–15 years, mean: 12.70 years) had an intraoral scan and an alginate impression prior to orthodontic treatment. During the procedures, chairside time was registered in minutes and patient experience was assessed by a Visual Analogue Scale questionnaire. Four maxillary dental arch distances were measured on digital models, on plaster casts, and directly in the mouth (intraoral). The cost of each procedure was presented graphically. Differences between the two procedures were tested by paired t-test and general linear model.

Results:

Patient experience was statistically better during intraoral scan compared with alginate impression regarding comfort, gag reflex, breathing, smell/sound, taste/vibration, and all statements concerning anxiety (P < .05). No significant difference in chairside time between the two procedures was found. No statistically significant differences in dental arch distances between digital models and plaster casts were found, but dental arch distances measured intraorally differed significantly from both digital models and plaster casts (P < .05). Cost calculation showed that the digital procedure was 10.7 times more expensive than the conventional procedure initially and, that after 3.6 years, the two procedures were equal in cost.

Conclusions:

Children preferred intraoral scan rather than alginate impression. Chairside time was equal for the two procedures as were the measurements of maxillary dental arch distances. The two procedures were equal in cost at 3.6 years.

Keywords: Children; Intraoral scan; Alginate impression; Experience; Chairside time; Cost calculation

INTRODUCTION

Prior to orthodontic diagnostics and treatment planning, dental models are very often used to evaluate the dentition and occlusion.¹ The conventional alginate impression is generally considered unpleasant,² especially for those with a sensitive gag reflex, and it has previously been shown that patient experience at the beginning of an orthodontics treatment is important for the compliance and treatment outcome.³ The patient experience of intraoral scan compared with conventional alginate impression in young orthodontic patients has only been investigated in a few studies.^4,5

The chairside time during treatment may also influence the patient experience.⁶ The time requirements for intraoral full-arch scans compared to conventional alginate impression differ and only a few studies have been performed involving children and young adolescents.^4,5 Therefore, further investigations of patient experience and chairside time between alginate impression and intraoral scan may be needed in children and young adolescents with severe malocclusion prior to orthodontic treatment.⁷

Patient experience and chairside time may not be the only factors to consider before implementing a new technique in the clinic, such as using an intraoral scanner. The reliability and cost also may be considered. It has been proposed that digital models from intraoral scanning reproduce the intraoral structures more accurately compared with plaster casts⁶ but no studies have so far compared both techniques with direct intraoral measurements. Additionally, one study proposed that the cost of an intraoral scanner can be recovered in reduced overhead and increased practice efficiency and may pay for itself within two years,⁸ but further studies may be needed to evaluate the economic perspective.

The aim of the present study was to compare patient experience, chairside time, dental arch distances, and costs of dental models derived from digital intraoral scans and alginate impressions in pre-orthodontic children and young adolescents with severe malocclusion.

MATERIALS AND METHODS

All pre-orthodontic children and adolescents who met the inclusion criteria were recruited from the Postgraduate Clinic in Orthodontics, Department of Odontology, University of Copenhagen in the period from September 2016 to October 2017. The inclusion criteria were: (1) children and adolescents between 9 and 15 years, (2) no previous orthodontic treatment or experience with digital intraoral scan or alginate impression technique, and (3) indication for orthodontic treatment according to the Danish Procedure for Screening the Child Population for Severe Malocclusion entailing Health Risks.⁹ Patients who declined participation and patients with craniofacial syndromes or other general diseases were excluded.

The total group comprised 59 patients, 28 girls, and 31 boys, aged 9 to 15 years (mean: 12.83 years and 12.56 years, respectively). Informed oral consent was obtained from legal guardians and assent was obtained from patients prior to conducting the study. The protocol was approved by The Danish Data Protection Agency (SUND-2016-77). Power analysis using the mean prevalence regarding validity, time consumption, and patient comfort reported in recent studies^4,10–12 showed that at least 42 subjects were required to have sufficient power (90%) to identify statistically significant differences at the 5% level of significance.

Two operators performed the following procedures:

Alginate Impression and Intraoral Scan

Each patient had an alginate impression at the first appointment and an intraoral scan at the following appointment (performed by the same operator), prior to orthodontic treatment.

Alginate impressions were obtained with a 180-hour irreversible hydrocolloid impression material (GC Aroma Fine Plus fast set; GC Corporation, Tokyo, Japan) and standard perforated metal trays (Zenith Dental, Agerskov, Denmark) with the patient seated upright. Immediately after the impressions, a wax bite registration (Alminax; Associated Dental Products Ltd, Swindon, Wiltshire, UK) and a silicone bite registration (Occlufast Rock, Zhermack S.p.A, Badia Polesine, Italy) with the patient's teeth in centric occlusion were performed. The alginate impressions were poured with plaster (Hinrizit, Ernst Hinrichs, Goslar, Germany).

The intraoral scan was performed using 3Shape scanner (3Shape, TRIOS Classic, version 1.4.6.0, Copenhagen, Denmark) with the patient lying down, in the following sequence: lower jaw, upper jaw, and bite registration, according to the manufacturer's recommendation. The examiners had no prior experience with intraoral scanning but received 10 hours of theoretical instruction and hands-on intraoral training on five subjects before scanning the first patient. They were thereby equally calibrated.

Patient Experience

Immediately after taking the alginate impression and performing the intraoral scan, the patients were asked to complete a questionnaire regarding comfort and anxiety on a modified 100-mm Visual Analogue Scale (VAS) with elements from face rating scales,^13,14 including a smiling face at the lowest score (0 mm) and a sad face without tears at the highest score (100 mm). Each VAS score was measured to the nearest millimeter.

Comfort was evaluated by seven questions regarding time perception, comfort, gag reflex, breathing, smell/sound, taste/vibration, and temperature during the procedures (Figure 1).^4,15 Anxiety was evaluated by six statements: feeling uneasy, feeling insecure, feeling upset, feeling afraid, feeling nervous, and feeling happy (Figure 2).¹⁶

Figure 1. . Patient comfort evaluated by seven questions:4, 15 (1) Did the impression/intraoral scan take a long time to make? (2) Was it uncomfortable to have the impression/intraoral scan taken? (3) Was your gag reflex triggered while the impression/intraoral scan was taken? (4) Was it difficult to breathe while the impression/intraoral scan was taken? (5) Were you bothered by the smell/sound of the impression/intraoral scanner material? (6) Were you bothered by the taste/vibrations of the impression material/intraoral scanner? (7) Were you bothered by the temperature of the impression material/intraoral scanner? — **Figure 1** Patient comfort evaluated by seven questions:^{4, 15} (1) Did the impression/intraoral scan take a long time to make? (2) Was it uncomfortable to have the impression/intraoral scan taken? (3) Was your gag reflex triggered while the impression/intraoral scan was taken? (4) Was it difficult to breathe while the impression/intraoral scan was taken? (5) Were you bothered by the smell/sound of the impression/intraoral scanner material? (6) Were you bothered by the taste/vibrations of the impression material/intraoral scanner? (7) Were you bothered by the temperature of the impression material/intraoral scanner?
Citation: The Angle Orthodontist 89, 6; 10.2319/020619-84.1

Figure 2. . Patient anxiety evaluated by six statements:16 (1) I felt uneasy while the impression was being taken/during the scanning. (2) I felt insecure while the impression was being taken/during the scanning. (3) I felt upset while the impression was being taken/during the scanning. (4) I felt afraid while the impression was being taken/during the scanning. (5) I felt nervous while the impression was being taken/during the scanning. (6) I felt happy while the impression was being taken/during the scanning. — **Figure 2** Patient anxiety evaluated by six statements:¹⁶ (1) I felt uneasy while the impression was being taken/during the scanning. (2) I felt insecure while the impression was being taken/during the scanning. (3) I felt upset while the impression was being taken/during the scanning. (4) I felt afraid while the impression was being taken/during the scanning. (5) I felt nervous while the impression was being taken/during the scanning. (6) I felt happy while the impression was being taken/during the scanning.
Citation: The Angle Orthodontist 89, 6; 10.2319/020619-84.1

Chairside Time

The chairside time was measured to the nearest minute during the procedures. For the alginate impression, the chairside time included alginate mixing with the water, impressions of the upper and lower arches and bite registrations, as well as any impressions that needed to be retaken. For the intraoral scan, the chairside time included scans of the upper and lower arches including the palate, bite registration, and intermediate trimming of the scan as well as any scans that needed to be retaken.

Dental Arch Distances

Maxillary dental arch distances were measured directly in the mouth (I), on the plaster cast (G), and on the digital model (S) to the nearest 0.01 mm (Figure 3). An intraoral digital caliper (G&H Orthodontics, Franklin, IN, USA) was used to measure the distances in the mouth and on the plaster cast. On the digital models, the 3Shape software was used to measure the distances (OrthoSystems 2015-1, Version 1.6.1.10, Patch 10). The following four distances were registered in all three settings:¹⁷

TC3:
Distance between the cusp tips of the permanent upper canines
TC6:
Distance between the mesiofacial cusp tips of the permanent upper first molars
TC6,3+:
Distance between the mesiofacial cusp tip of the permanent upper right first molar and the cusp tip of the permanent upper right canine
TC+3,6:
Distance between the mesiofacial cusp tip of the permanent upper left first molar and the cusp tip of the permanent upper left canine

Figure 3. . Illustration of measurements intraorally (a), on plaster casts (b), and on digital models (c). The measurements are defined previously.17, 25 — **Figure 3** Illustration of measurements intraorally (a), on plaster casts (b), and on digital models (c). The measurements are defined previously.^{17 25}
Citation: The Angle Orthodontist 89, 6; 10.2319/020619-84.1

Costs Calculation

The cost of both procedures was estimated on an assumption of 310 dental models per year, according to the recommendation of the annual number of new patients for two full-time municipal Specialists in Orthodontics in Denmark. The monetary evaluations for each of the two procedures included the initial cost of the equipment and the accumulative yearly cost. The accumulative yearly cost was calculated by adding the price of materials and other expenses for the 310 models per year for each of the procedures.

The initial equipment for alginate impression included impression trays, alginate load on trays, spatulas, and an alginate mixer (Hauschild Dental, AM-501; 2017, Hamm, Germany). Materials and other expenses for manufacturing plaster casts included alginate powder, bite registration material, disinfection agents, and laboratory cost of plaster cast manufacturing.

The initial equipment for intraoral scanning included a computer (Alienware, Dell Headquarters, Round Rock, TX, USA), software (3Shape Ortho Analyzer), and 3D intraoral scanner (3Shape, TRIOS 3). Materials and expenses for producing 3D models included scanner tip and software update fees.

All prices included were list prices with no economic deals and no discounts included in the calculation. The present study did not incorporate costs associated with replacement of the equipment.

Reliability and Method Error

The intra- and inter-observer reliability was determined by repeating all measurements after 4 weeks on 25 randomly selected plaster casts and 25 randomly selected scans.

No systematic error was found tested by paired t-test. The method error ranged from 0.001 to 0.050¹⁸ and the reliability ranged from 0.99 to 1.¹⁹

Statistical Analyses

The statistical analyses were performed using SAS (v 9.4, Cary, NC, USA) software. The results of the tests were considered to be significant at P < .05.

The continuous data were tested by Q–Q plots on the residuals and was normally distributed. Age and gender distribution was tested by a t-test and an exact test based on binominal distribution. Differences in patient experience and the effect of age and gender were assessed by General Linear Model. Differences in dental arch distances and chairside time were assessed by paired t-test. Description of costs was presented graphically.