A Comparison of Conventional Versus Digital PAR (Peer Assessment Rating) Scores Using an Intraoral Scanner

In dentistry, Peer Assessment Rating (PAR) is an objective way of quantifying how maligned a patient's teeth are by scoring orthodontic study models. It can also be used to assess treatment outcome by comparing pre- and post-treatment scores. Traditionally, PAR scoring is performed manually on plaster casts by a trained and calibrated individual. The plaster casts consume considerable amounts of storage space and the process of manual scoring can be time consuming and expensive. The recent decades have seen a rise in popularity of intra oral scanners in dentistry to produce digital study models. These obviate the need for physical storage space and a software can be used to calculate PAR scores more conveniently and at a faster speed. A review of the current literature showed that the CS 3600 intra oral scanner by Carestream Dental demonstrated acceptable accuracy for clinical use.

In this study, patients will receive the usual impressions and their moulds will be PAR scored manually (usual care pathway). In addition, they will also receive intra oral scans with Carestream 3600 and the digital models will be scored by a computer. Manual and digital scores will be compared and analysed for any significant discrepancies.

CS 3600 intra oral scanner is already licenced for the use in dentistry and is routinely used by some dental practitioners to substitute conventional impressions and plaster models in restorative, implant and orthodontic diagnosis and treatment planning. The scanner is 220 x 38 x 58 mm in size and operates with video capture technology. It emits no radiation.

Peer Assessment Rating (PAR) is an objective way of quantifying how severe a malocclusion is by scoring orthodontic study models. It can also be used to assess treatment outcome. All National Health Service (NHS) orthodontic providers in the United Kingdom are contractually bound to submit PAR score changes for at least 20 of their treated cases plus 10% of the remainder of their case load every year. Traditionally, PAR scoring is performed manually on plaster casts by a trained and calibrated individual. The plaster casts must be retained as part of the patient's medical records and hence consume considerable amounts of storage space. The process of manual scoring is also time intensive. Digital models obviate the need for physical storage space and a software can be used to calculate PAR scores more conveniently and at a faster speed. A review of the current literature showed that the CS 3600 intra oral scanner by Carestream Dental demonstrated acceptable accuracy for clinical use. The purpose of this study is to assess the accuracy of PAR scores obtained from digital models with those obtained manually from conventional models for the same patient at one given point in time.

Aims: Against this background, the aim of this study is to compare digital PAR scoring using the CS 3600 intraoral scanner with conventional PAR scoring.

Objectives: The objectives are to investigate whether PAR scoring on models acquired through direct and indirect digitisation produces any significant errors when compared with conventional PAR scoring on plaster models. The study will also seek to measure the chairside time taken to produce upper and lower full arch scans and bite registration with CS 3600 versus the time taken to produce equivalent alginate impressions and wax bite. Furthermore, the time taken for digital scoring will be measured and compared with the conventional method. Finally, patient preference with regard to intraoral scans versus impressions will be investigated.

Method: The sample size was confirmed using a power calculation. The sample will consist of 66 orthodontic patients at Kingston Hospital, excluding any patients with fixed appliances or bonded components. All patients will receive conventional impressions as well as intraoral scans, serving as their own controls. Plaster casts poured from the impressions will also be scanned to produce indirect digital models. PAR scoring will then be performed by one investigator on all three models (plaster casts, direct and indirect digital models) for comparison. A second investigator will record the time taken to perform scans and impressions as well as the time taken to complete digital and conventional scoring. Immediately after the clinical procedure patients will be given a questionnaire evaluating their preference.

Data analysis: Data from the PAR scorings and questionnaires will be recorded and analysed using SPSS following consultation with a bio-statistician. The data will then be graphically represented in the form of tables and charts.

Eligibility Criteria:
Inclusion Criteria:

1. Patients undergoing orthodontic treatment at Kingston Hospital
2. Patients who have completed their orthodontic treatment and are attending for retainer reviews at Kingston Hospital
3. age 11-50

Exclusion Criteria:

1. patients with fixed or bonded appliances
2. age \<11 or \>50
3. Inability to gain informed consent due to communication barriers