Accuracy of Digital Intraoral Scans Three-dimensional Surface Analysis Compared with Plaster Models Dental Measurement in Mixed Dentition

Abstract

Aims and background

This study aimed to assess the accuracy of digital intraoral scans in capturing the three-dimensional (3D) surface of teeth and dental arches in mixed dentition, compared with conventional plaster models. Intraoral scanning technology has seen rapid advancements in recent years, revolutionizing orthodontic and dental practices. However, its accuracy in mixed dentition remains a subject of investigation.

Materials and methods

Children with mixed dentition (n = 34) were selected according to specific criteria. Digital intraoral scanning was performed using the Medit i500, and conventional plaster models were created following alginate impression techniques. The arch widths on the 3D digital models were measured using Medit Link software, while the conventional models were measured using calipers. Both sets of data were then analyzed using Moyer's analysis.

Results

The results of the study showed no significant difference (p > 0.05) between the mean space analysis measurements obtained conventionally and digitally in the mixed dentition phase using Moyer's analysis method.

Conclusion

Despite minor discrepancies compared to conventional plaster models, digital intraoral scans offer a clinically acceptable level of accuracy for orthodontic diagnosis and treatment planning. The benefits of digital scanning, including improved patient experience and enhanced digital workflows, make it a promising tool for modern dental and orthodontic practices.

Clinical significance

There is no significant difference between space analysis measurements in the mixed dentition phase using Moyer's analysis on conventional and 3D digital models.

How to cite this article

Nelwan SC, SD Karuniadewi AA, Nowwarote N, et al. Accuracy of Digital Intraoral Scans Three-dimensional Surface Analysis Compared with Plaster Models Dental Measurement in Mixed Dentition. Int J Clin Pediatr Dent 2024;17(12):1363–1369.

Introduction

Alginate is the most common impression material used in dental practice. Alginate impressions have been the standard in most dental practices due to their low cost, fast setting time, minimal instrumentation, and simple execution technique manipulation. Typically, they are used for initial study impressions for medical and diagnostic purposes.¹ Although alginate impressions are among the most frequently used, they have several limitations, such as being messy to work with, having poor dimensional stability, and exhibiting various distortions that can affect the accuracy of the impression.² An alginate impression that is free of bubbles, pores, shreds, and dimensional changes can be considered accurate. Alginate impressions should be poured using dental stone to obtain a plaster model.^1,2

Technological innovations are taking hold in the world of dentistry. Digital models are increasingly replacing traditional plaster models in orthodontics, as they provide superior options for storing, accessing, and sharing data. These models are effectively applied in diagnosis and treatment planning, and working in a virtual environment streamlines procedures, saving time.³ Digital study models can be created through three distinct methods: direct intraoral scanning, indirect surface scanning of stone casts, or utilizing cone-beam computed tomography (CBCT) scans.⁴ In orthodontics, digital models serve various purposes such as analyzing teeth and occlusion, simulating treatment, designing and producing appliances, and evaluating treatment outcomes.⁵

Studies conducted by orthodontic researchers revealed that the prevalence of malocclusion among Indonesian adolescents of school age was 90% in 1983 and 89% in 2006. These studies showed that a significant majority of children in their growth phase experienced malocclusion, underscoring the importance of initiatives to reduce its prevalence. Early examinations and preventive measures are suggested strategies for addressing malocclusion.⁶ Mixed dentitions necessitate a high-accuracy assessment of arch length discrepancies to ensure successful orthodontic treatment. Traditionally, space analysis in mixed dentitions involves comparing the actual mesiodistal width of the supporting area with a standard value.⁴

Space analysis for mixed dentition includes Huckaba analysis, Moyer's analysis, Tanaka–Johnston analysis, total space analysis, Hixon and Oldfather method, and Nance Carey's analysis.⁷ The important information required during the period of mixed dentition is whether there will be enough room to accommodate the unerupted canines and the first and second premolars. Moyer's analysis provides this information quickly, without the need for a fullmouth, long-cone survey, which can be difficult to obtain when dealing with apprehensive young children or parents who are opposed to radiation. In Moyer's study, probability charts were created to estimate the combined widths of canines and premolars based on the total width of the mandibular incisors for both dental arches.⁸

The gold standard for diagnostic measurements is using a caliper on a stone-cast dental model. However, study models made of dental stone are prone to damage and loss of accuracy due to external forces.⁴ Conventional alginate impression techniques can also be particularly difficult for patients who have severe gag reflexes, experience irritation, and feel discomfort. It requires storing raw materials and allocating space for plaster models, which are susceptible to damage, loss, and deterioration.⁵ Especially, younger patients often prioritize comfort and thus favor the digital impression technique.⁹

Liczmanski et al. conducted a study in 2020 on intraoral scanning in children requiring orthodontic treatment during the mixed dentition phase, where the results of intraoral scanning were more detailed and less prone to errors compared to conventional alginate impressions. However, the study did not include measurements of jaw arch length and mesiodistal width of teeth.⁹ Al-Dulaimy et al., in their 2022 research, compared the accuracy of measuring jaw arch length in children during the mixed dentition phase between gypsum and digital models. In Ahmed's study and several previous studies, digital models were obtained from scanning gypsum models using an intraoral scanner (IOS), but direct scanning on children's intraoral was not performed. Previous studies have also confirmed the usefulness of intraoral scanning in the diagnosis and treatment planning of malocclusion.¹⁰

This research intends to evaluate the accuracy of digital mixed dentition space analysis results by performing direct full-arch intraoral scans in children's mouths compared to conventional measurements on plaster models.

Materials and Methods

The devices and materials required for this research include:

Devices

• Medit i500 IOS (Medit Corp., Seoul, Korea).

• Digital caliper (Mitutoyo).

Materials

• Alginate impression material (Hygedent, Beijing).

• Dental stone (Pro Model Super 11, Formula Saint-Gobain, French).

• Rubber mixing bowl.

• Alginate spatula.

• Impression trays.

Methods

This research uses a cross-sectional design. The subjects in this research were pediatric patients at Universitas Airlangga Dental Hospital, with a total of 34 children in the mixed dentition phase.

Inclusion Criteria

• Patients with age range 8–12 years.

• Patients in the mixed dentition stage, with all first permanent molars in the maxilla and mandible, and permanent central and lateral incisors in the mandible, have erupted completely.

• Patients with dental malocclusion requiring orthodontic treatment.

• Patients with early loss of primary teeth requiring space maintainer or partial denture treatment.

Exclusion Criteria

• Individuals with a history of emotional, psychological, or developmental disabilities, epilepsy, seizures, cleft lip or palate, other craniofacial abnormalities, or prolonged use of anticonvulsant medications.

• Patients who have experienced dentoalveolar injuries.

Procedure

Participants were chosen according to the specified inclusion and exclusion criteria, and informed consent was collected prior to the study. All participants underwent oral prophylaxis as a preparatory step.

Two types of procedures were carried out for each participant:

• A digital impression captured using the Medit i500 IOS (Medit Corp., Seoul, Korea).

• A conventional impression created with alginate material (Hygedent, Beijing).

All required materials were prepared and arranged before the patient was seated (Fig. 1). Full-arch intraoral scans were performed using the Medit i500 IOS (Medit Corp., Seoul, Korea), with the digital images generated via Medit Link software. Alginate impressions were taken for both the upper and lower jaws using Hygedent alginate impression material (Beijing). These impressions were then poured with dental stone (Pro Model Super 11, Formula Saint-Gobain, France) to create conventional study models. The bases were poured using dental plaster. The sampling process was carried out by a single operator, who performed impressions and intraoral scans on three to four patients in 1 day.

Figs 1A to F:

(A) Rubber bowl and alginate mixing spatula; (B) Impression trays; (C) Alginate impression material (Hygedent, Beijing); (D) Dental stone (Pro Model Super 11, Formula Saint-Gobain, French); (E) Medit i500 IOS (Medit Corp., Seoul, Korea); (F) Caliper (Mitutoyo)

The available space in each dental arch was calculated by summing four linear measurements: from the mesial edge of the right first permanent molar to the distal edge of the right lateral incisor, from the distal edge of the right lateral incisor to the mesial edge of the right central incisor, from the mesial edge of the left central incisor to the distal edge of the left lateral incisor, and finally, from the distal edge of the left lateral incisor to the mesial edge of the left first permanent molar. The first measurement method used Medit Design from Medit Link software, which is Medit's official software, with a measurement accuracy of up to 0.001 mm, covering the available space measurement and the mesiodistal width of the four incisors on the digital model (Fig. 2). The second measurement method used a caliper (Mitutoyo) with an accuracy of 0.01 mm on the study model (Pro Model Super 11, Formula Saint-Gobain, France), covering the available space measurement and the mesiodistal width of the four incisors (Fig. 3).

Figs 2A to C:

Measurement of arch perimeter on digital models using Medit Link software

Fig. 3:

Measurement of arch perimeter on conventional plaster models using caliper (Mitutoyo)

Space analysis in mixed dentition was conducted using Moyer's analysis method on both plaster and digital models. The required space was assessed by measuring the mesiodistal distances of all permanent lower incisors. To estimate the mesiodistal dimensions of the permanent canines and premolars in each arch, the measured mesiodistal width of the four lower incisors was entered into Moyer's probability table with a 75% probability (Table 1). The required space is calculated by taking the estimated mesiodistal distances of the permanent canines and premolars from Moyer's probability table, multiplying it by 2, and adding the mesiodistal width of all permanent incisors measured for each arch.

Table 1:

Probability tables of Moyer's for predicting the sizes of unerupted cuspids and bicuspids

A. Mandibular bicuspids and cuspids
Males
21/12 =	19.5	20.0	20.5	21.0	21.5	22.0	22.5	23.0	23.5	24.0	24.5	25.0	25.5
%
95	21.6	21.8	22.0	22.2	22.4	22.6	22.8	23.0	23.2	23.5	23.7	23.9	24.2
85	20.8	21.0	21.2	21.4	21.6	21.9	22.1	22.3	22.5	22.7	23.0	23.2	23.4
75	20.4	20.6	20.8	21.0	21.2	21.4	21.6	21.9	22.1	22.3	22.5	22.8	23.0
65	20.0	20.2	20.4	20.6	20.9	21.1	21.3	21.5	21.8	22.0	22.2	22.4	22.7
50	19.5	19.7	20.0	20.2	20.4	20.6	20.9	21.1	21.3	21.5	21.7	22.0	22.2
35	19.0	19.3	19.5	19.7	20.0	20.2	20.4	20.67	20.9	21.1	21.3	21.5	21.7
25	18.7	18.9	19.1	19.4	19.6	19.8	20.1	20.3	20.5	20.7	21.0	21.2	21.4
15	18.2	18.5	18.7	18.9	19.2	19.4	19.6	19.9	20.1	20.3	20.5	20.7	20.9
5	17.5	17.7	18.0	18.2	18.5	18.7	18.9	19.2	19.4	19.6	19.8	20.0	20.2
Females
95	20.8	21.0	21.2	21.5	21.7	22.0	22.2	22.5	22.7	23.0	23.3	23.6	23.9
85	20.0	20.3	20.5	20.7	21.0	21.2	21.5	21.8	22.0	22.3	22.6	22.8	23.1
75	19.6	19.8	20.7	20.3	20.6	20.8	21.1	21.3	21.6	2.9	22.1	22.4	22.7
65	19.2	19.5	19.7	20.0	20.2	20.5	20.7	21.0	21.3	21.5	21.8	22.1	22.3
50	18.7	19.0	19.2	19.5	19.8	20.0	20.3	20.5	20.B	21.1	21.3	21.6	21.8
35	18.2	18.5	18.8	19.0	19.3	19.6	19.8	20.1	20.3	20.6	20.9	21.1	21.4
25	17.9	18.1	18.4	18.7	19.0	19.2	19.5	19.7	20.0	20.3	20.5	20.8	21.0
15	17.4	17.7	18.0	18.3	18.5	18.8	19.1	19.3	19.6	19.8	20.1	20.3	20.6
5	16.7	17.0	17.2	17.5	17.8	18.1	18.3	18.6	18.9	19.1	19.3	19.6	19.8
B. Maxillary bicuspids and cuspids
Males
21/12 =	19.5	20.0	20.5	21.0	21.5	22.0	22.5	23.0	23.5	24.0	24.5	25.0	25.5
(%)
95	21.2	21.4	21.6	21.9	22.1	22.3	22.6	22.8	23.1	23.4	23.6	23.9	24.1
85	20.6	20.9	21.1	21.3	21.6	21.8	22.1	22.3	22.6	22.8	23.1	23.3	23.6
75	20.3	20.5	20.8	21.0	21.3	21.5	21.8	22.0	22.3	22.5	22.8	23.0	23.3
65	20.0	20.3	20.5	20.8	21.0	21.3	21.5	21.8	22.0	22.3	22.5	22.8	23.0
50	19.7	19.9	20.2	20.4	20.7	20.9	21.2	21.5	21.7	22.0	22.2	22.5	22.7
35	19.3	19.5	19.9	20.1	20.4	20.6	20.9	21.1	21.4	21.6	21.9	22.1	22.4
25	19.1	19.3	19.6	19.9	20.1	20.4	20.6	20.9	21.1	21.4	21.6	21.9	22.1
15	18.8	19.0	19.3	19.6	19.B	20.1	20.3	20.6	20.8	21.1	21.3	21.6	21.8
5	18.2	18.5	18.8	19.0	19.3	19.6	19.8	20.1	20.3	20.6	20.8	21.0	21.3
Females
95	21.4	21.6	21.7	21.8	21.9	22.0	22.2	22.3	22.5	22.6	22.8	22.9	23.1
85	20.8	20.9	21.0	21.1	21.3	21.4	21.5	21.7	21.8	22.0	22.1	22.3	22.4
75	20.4	20.5	20.6	20.8	20.9	21.0	21.2	21.3	21.5	21.6	21.8	21.9	22.1
65	20.1	20.2	20.3	20.5	20.6	20.7	20.9	21.0	21.2	21.3	21.4	21.6	21.7
50	19.6	19.3	19.9	20.1	20.2	20.3	20.5	20.6	20.8	20.9	21.0	21.2	21.3
35	19.2	19.4	19.5	19.7	19.8	19.9	20.1	20.2	20.4	20.5	20.6	20.8	20.9
25	18.9	19.1	19.2	19.4	19.5	19.6	19.8	19.9	20.1	20.2	20.3	20.5	20.6
15	18.5	18.7	18.8	19.0	19.1	19.3	19.4	19.6	19.7	19.8	20.0	20.1	20.2
5	17.8	18.0	18.2	18.3	18.5	18.6	18.8	18.9	19.1	19.2	19.3	19.4	19.5

All data were tabulated and statistically analyzed. The data were analyzed using SPSS 16.0 for Windows XP. The Kolmogorov–Smirnov and Shapiro–Wilk tests were used to examine the normality of the data for each variable. Levene's test was applied to check the homogeneity of variances. Since the data adhered to a normal distribution, bivariate analysis was conducted with the independent t-test to determine if there were significant differences between the two variables. All tests were considered statistically significant if the p-value was 0.05 or lower.

Results

Quantitative data analysis was used for the results of this study. The normality of the data for each variable was assessed using the Kolmogorov–Smirnov and Shapiro–Wilk tests, with p-values >0.05 indicating that the data followed a normal distribution. The homogeneity of variance was then tested using Levene's test, which resulted in a p-value >0.05, confirming homogeneity. With the fulfillment of the normality and homogeneity requirements, further testing was conducted using the independent t-test with a significance level of p < 0.05 to determine the differences in space analysis results between plaster models and digital models.

The independent t-test analysis results revealed that the t-value for available space in the upper jaw was 0.635 with a probability of 0.527 (p > 0.05), indicating no significant difference between the available space analysis results for the upper jaw on plaster models and digital models. The t-value for available space in the lower jaw was –1.461 with a probability of 0.149 (p > 0.05), indicating no significant dissimilarity between the available space analysis results for the lower jaw on plaster models and digital models. The t-value for required space in the upper jaw was –0.641 with a probability of 0.523 (p > 0.05), indicating no substantial difference between the required space analysis results for the upper jaw on plaster and digital models. The t-value for required space in the lower jaw was 1.003 with a probability of 0.320 (p > 0.05), indicating no substantial dissimilarity between the required space analysis results for the lower jaw on plaster models and digital models (Table 2). The conclusion of this research showed no substantial difference (p > 0.05) between the mean space analysis measurements obtained conventionally and digitally in the mixed dentition phase using Moyer's analysis method.

Table 2:

Intergroup comparison of space analysis on plaster models and digital models

		t-test for equality of means
		t	df	Sig. (two-tailed)	Mean difference	Std. error difference	95% confidence interval of the difference
							Lower	Upper
RA available space	Plaster model	−.286	66	.776	−.33422	1.16758	−2.66537	1.99693
	Digital model	−.286	65.998	.776	−.33422	1.16758	−2.66537	1.99694
RB available space	Plaster model	−.634	66	.528	−.65382	1.03106	−2.71240	1.40475
	Digital model	−.634	65.998	.528	−.65382	1.03106	−2.71240	1.40475
RA required space	Plaster model	−.073	66	.942	−.06735	.91829	−1.90079	1.76608
	Digital model	−.073	65.961	.942	−.06735	.91829	−1.90081	1.76610
RB required space	Plaster model	−.152	66	.880	−.12412	.81690	−1.75511	1.50687
	Digital model	−.152	65.967	.880	−.12412	.81690	−1.75513	1.50689

Discussion

Space analysis refers to the examination of the maxillary and mandibular arches across three spatial planes (vertical, sagittal, transverse) and is a tool in determining orthodontic diagnosis and treatment planning. Space analysis is divided into analysis for deciduous teeth, permanent teeth, and mixed dentition. Mixed-stage dentition space analysis includes: Moyer's analysis, Huckaba analysis, Tanaka–Johnston analysis, Hixon and Oldfather method, Nance Carey's analysis, and total space analysis.⁷ Discrepancy in the model refers to the difference between available space and required space. Discrepancy in the model is used to determine the type of treatment for the patient, whether it includes extraction or nonextraction of permanent teeth. Available space is defined as the space from the mesial of the right first permanent molar to the mesial of the left first permanent molar (second premolar to second premolar) that will be occupied by the permanent teeth in their correct positions. Required space is the total mesiodistal width of the permanent teeth from the mesial of the right first permanent molar to the mesial of the left first permanent molar (second premolar to second premolar).¹¹

Moyer's method of mixed dentition space analysis is based on the correlation between one set of teeth and another, enabling the prediction of the dimensions of unerupted teeth by examining the size of the teeth that have already erupted in the oral cavity. The group of teeth used as a guide is the mandibular permanent central and lateral incisors. Moyer's probability table has been developed to predict the combined mesiodistal dimension of the maxillary and mandibular permanent canines and premolars based on the combined mesiodistal dimension of the four mandibular permanent incisors (Table 1).⁷ The advantages of using Moyer's analysis method include minimal error rates, precise knowledge of the range of possible errors, equal accuracy when performed by both novice and expert operators, requiring little time, and no need for special equipment.⁷

In this study, 34 patients aged between 8 and 12 years were selected. Digital models were generated using the Medit i500 IOS (Medit Corp., Seoul, Korea), and the space analysis measurements were computed with the Medit Link software. Conventional study models were obtained from alginate impressions cast with dental stone. The conventional space analysis measurements were obtained from the plaster models using a digital caliper (Mitutoyo).

Thanks to technological advancements, dentists now have access to new tools that improve the accuracy of orthodontic diagnosis and treatment planning. Converting plaster models into digital files offers highly precise diagnostic data. Digital models from IOSs address the storage issues associated with plaster models. Additionally, they provide benefits such as immediate access to three-dimensional (3D) data without the need to retrieve physical models, the capability to conduct precise treatment planning and diagnostics for a range of orthodontic cases, along with the convenience of sharing virtual images worldwide for referrals and consultations.⁵

The results of this research revealed no statistically significant dissimilarity between space analysis assessments obtained from conventional plaster models and digital models. A previous study by Zhang et al. also found no substantial differences between plaster models and intraoral scans. Bland–Altman analysis revealed that the differences between the two models were within acceptable limits. These findings suggest that dental measurements obtained directly from intraoral scans are reliable for clinical use and can be viable alternatives to plaster models.¹² In research by Liczmanski et al., it was confirmed that the dimensional dissimilarity between intraoral scans and conventional alginate impressions in mixed dentition is clinically acceptable. Although some studies have reported statistical differences in the trueness and precision of intraoral scans, the authors concluded that their clinical accuracy is comparable to, or even better than, that of alginate impressions.⁹

Several studies have demonstrated that all linear dental measurements from digital models, derived from scans of alginate impressions and plaster models, are valid, reliable, and reproducible for diagnostic purposes. Both manually and digitally measured models showed similar results for vertical and transverse measurements, with most showing no significant differences. These findings align with those of various other studies.³ Labib et al., in their study, found that intraoral scan measurements tend to be slightly larger than impression measurements. Compared to the overall bias, these values can be regarded as negligible and clinically insignificant.³ This aligns with the results of this study, where the average measurements on digital models were approximately ± 0.2 mm larger than those on conventional models.

The study assessing the accuracy of digital intraoral scans in comparison to conventional plaster models for dental measurements in mixed dentition presents important implications for dentists and dental practice. Another benefit of intraoral scanning is that image setups are simple to store, as they don't take up the extensive space required by plaster models. They can provide adequate information for clinicians to develop treatment plans, thus eliminating the need for space to store plaster casts.¹⁰ Patients, especially children and adolescents, often find digital intraoral scanning more comfortable and less invasive than conventional impression techniques. The study's confirmation of accuracy reinforces the trend toward improved patient experiences in orthodontic practices. Digital scans reduce chair time and streamline workflows.¹³ The study's findings support using these scans for efficient treatment planning and communication among dental professionals. Digital records are easily stored and can be readily accessed for future reference. This aspect simplifies patient follow-ups, facilitates research, and enhances record-keeping. Digital scans can also be integrated with orthodontic software and 3D printers for precise appliance fabrication. The study's results validate the use of digital scans within these advanced workflows.¹⁴

In conclusion, this study highlights the accuracy and clinical viability of digital intraoral scans in mixed dentition cases, reinforcing their role in modern orthodontic and dental practices. The findings support the ongoing transition toward digital workflows, emphasizing the importance of staying updated with technological advancements to provide patients with the best possible care.

Conclusion

This study offers valuable information on the accuracy of digital intraoral scans in cases of mixed-stage dentition. Despite minor discrepancies compared to traditional plaster models, digital intraoral scans offer a clinically acceptable level of accuracy for orthodontic diagnosis and treatment planning. The benefits of digital scanning, including improved patient experience and enhanced digital workflows, make it a promising tool for modern dental and orthodontic practices. Further research is warranted to explore the long-term clinical outcomes and cost-effectiveness of digital intraoral scanning in mixed dentition cases.

*Clinical Significance

There is no significant difference between space analysis measurements in the mixed dentition phase using Moyer's analysis on conventional and 3D digital models.