How good are our impressions? an audit of alginate impression quality in the production of removable prostheses

Methodology

A prospective audit was carried out with two cycles over a six-month period on alginate impressions for the provision of removable prostheses. A sample size of 10 impressions per cycle were recorded and assessed according to the criteria and standards set below. A data sheet was compiled listing the purpose of the impression, the type of tray used and the quality score from the clinician, a peer review score from another dentist in the practice and the dental technician.

Criteria and standards

A protocol was established to provide a reproducible method for completing an alginate impression:1^,2

Criteria and standards were established to create a scoring system for the impressions (Table 1).

This was based on criteria set in three separate studies assessing impressions quality3^,4^,5^,6 and formulated with input from a local dental laboratory. This enabled the scoring system to remain impartial. A target was set for the standard of alginate impressions taken in the first audit cycle. This was to take impressions of a score above ‘3’ and to score a ’4’ or a ‘5’ at least 50% of the time.

A sample was taken in the first cycle of 10 alginate impressions. Examples of impressions with their scoring are displayed in Figure 1.

Results of first cycle

The results are displayed in Table 2. They reveal a failure in matching the above criteria, with some impressions scored as a ‘1’ and ‘2’. An average of 43.3% impressions were scored ‘4’ or ‘5’.

Discussion

The results of the first cycle reveal that 90% of impressions taken were a minimum standard of 3 (satisfactory) or above when self assessed, in comparison to 80% when assessed by the peer review scorer and the laboratory. This reveals that not only did the author not meet his initial standard set, but also his marking was more flattering than that of the independent adjudicators. Another finding from the results demonstrates a higher score being given when a rigid special tray is used for a secondary impression, in contrast to when a plastic stock tray is used for primary impressions.

Implementing change

Actions taken to improve the author's impression-taking ability came from evidence-based research1 which entailed a ‘how to guide’ using dental alginate. Tutorials with the DF1 trainer in tray extension and manipulation with green stick were helpful.

Recommendations that the author took forward to the next audit cycle included anticipating tray extension on every patient to make sure impression material is never unsupported and prone to distortion. Also based on the author's findings and research, metal rim lock trays were then to be used for primary impressions.5 As the standards were not met on the first audit cycle, the standard set was unchanged. One could argue that the initial criteria may have been set too high, however, it should not be acceptable to score anything less than a ‘3’ and, therefore, it was important to improve impression-taking skills before performing the second cycle of audit.

Results of second cycle

The results for the second audit cycle are displayed in Table 3. They reveal success in matching the criteria set with all impressions at a minimum score of ‘3’ and an average of 56.6% scoring at ‘4 or 5’. These fulfil the initial standards set.

Reflection and recommendations for future audit

The results of the second cycle indicate an overall improvement in being able to produce an impression of good quality.

There are aspects of the audit which the author feels need improvement before further cycles take place:

Overall, the audit has provided a significant opportunity to be both self-reflective and self-critical, whilst encouraging a team approach to improve the quality of patient care.