A PREP panel, practice-based, evaluation of the handling of the kerr demi-ultra light curing unit

Practice-based research

The importance of practice-based research has been emphasized by Mandel, who considered that ‘research is not only the silent partner in dental practice, it is the very scaffolding on which we build and sustain a practice’.¹

A wide variety of research projects may be considered to be appropriate to general dental practice including, assessment of materials, devices and techniques, clinical trials of materials, assessment of treatment trends, and patient satisfaction with treatment.² In this regard, the volume of clinical material seen in general dental practice makes dental practice an area of central importance in the assessment of new techniques, devices and materials, as success of a material, device or technique could be considered to be its performance in everyday use in a particular dentist's office.

Central to good performance of dental materials are, not only their physical properties, but also their ease of use, since it could be suggested that a device or material which handles easily will be more likely to produce an optimally performing restoration than one which is difficult to use. The assessment of the handling of a new device, in this case a Light Curing Unit (LCU) with novel features, is therefore of importance.

The performance of a material or device by one operator is necessarily subjective but, when practitioners band together to form a group in order to assess the handling of new materials in dental practice, the results are likely to be more objective and open to generalization. All of this is possible when practitioner-based research groups are teamed with the expertise available in academic institutions. A UK-based group of practice-based researchers is the PREP (Product Research and Evaluation by Practitioners) Panel. This group was established in 1993 with 6 general dental practitioners, and has grown to contain 33 dental practitioners located across the UK, with one in mainland Europe.³ The group have completed over 70 projects, ‘handling’ evaluations of materials and techniques and, more recently, clinical evaluations (n = 8) of restorations placed under general dental practice conditions, with the restorations being followed for periods of one to five years.

Light Curing Units (LCUs)

The derivation of light curing chemistry from the UK paint industry into dentistry heralded the introduction of so-called command set resin-based materials in the early 1980s and the concordant development of resin composite materials to the sophisticated aesthetic materials that we know today. Early LCUs were bulky and unreliable, but later versions proved to be reliable, albeit with the potential problems of reducing light output with time as the light source degraded. However, the introduction of LCUs utilizing an LED as the light source in the late 1990s proved to be a worthwhile innovation, since these used less power and could therefore be battery operated, resulting in more versatile LCUs as a power cable was not needed to connect the LCU to a dental unit. Early LED LCUs did not have the light output of gold standard LCUs, such as the Demetron 500 and, indeed, some needed up to 21 separate LEDs to provide sufficient light intensity to cure a resin composite restoration. As with computer technology, these deficiencies were quickly overcome and today's LED LCUs have more than adequate light curing potential, all through one LED. Advantages of LED light units include a constant output which does not degrade with time, their low power needs and ease of use, but they require a light guide to transmit the light from the LEDs which are housed within the body of the LCU. This problem has been overcome by the introduction of the Kerr Demi-Ultra LCU, in which the LEDs providing the light output are placed close to the tip of the light guide. This LCU also uses an innovative power source. The question therefore is ‘What will a group of general dental practitioners think of this innovation?’.

It is therefore the aim of this project to evaluate the in-practice handling and use of Kerr's Demi-Ultra LCU (Figure 1).

Methods

Results

Of the 15 evaluators from the PREP panel, four were female and the average time since graduation was 29 years, with a range of 11–46 years.

Background information based on the evaluators' existing LCU

The number of LCUs currently in use in the evaluators' practices varied from 2 (5 evaluators), to 3–5 (9 evaluators), while one evaluator had 6 LCUs. Five evaluators had a halogen LCU, two had a corded LED and all 15 had cordless LEDs. Reasons given for their choice of LCU included:

Halogen:

‘Original light and still used’ (4 similar);

‘Original Kerr Optilux (10+ years old) and still second brightest in the practice’.

Corded LED:

‘Built into Kavo chair’.

Cordless LED:

‘Ease of use, ease of charging, relatively cheap’;

‘Changed to this on assumption they give correct wavelength and intensity’;

‘Power and flexibility’;

‘Lightweight, easy to position, good price for multiple purchase’ (2 similar);

‘Lightweight, free with large order, 360 ° head turning, good battery life’;

‘Free with composite kit order’ (3 similar).

The evaluators were asked how often they charged the battery if they used a cordless LCU, with the results being as follows:

(a) After every patient	6 evaluators
(b) After multiple patients	2 evaluators
(c) Once during the day	1 evaluator
(d) Charge a spare battery separate to the light	1 evaluator
(e) At the end of the day/overnight	2 evaluators
(f) Other: ‘always kept on charge’, ‘once a week’

When the evaluators were asked what they considered the life of an LCU to be, the result was as follows:

(a) 2 years or less	2 evaluators
(b) 3–4 years	2 evaluators
(c) 5–6 years	6 evaluators
(d) 7–10 years	3 evaluators
(e) More than 10 years	2 evaluators

Regarding the sizes of curing tips used by evaluators, none used 2 mm or larger than 10 mm, while two used 4 mm, ten used 8 mm and four used 10 mm.

The reasons given for the size of tip that the evaluator used were:

‘Size it came with’ (7 similar);

‘Good coverage and spread of light’ (3 similar);

‘2 mm too small’;

‘Came with 8 mm and I wouldn't want a larger size’.

Evaluators used a wide variety of different LCUs. The reasons given for the choice of light included:

Ease of use (7 evaluators);

Cost (6 evaluators);

Ergonomics (6 evaluators);

Powerful output (5 evaluators);

Reliability (4 evaluators); and

Lightweight (4 evaluators).

The ease of use of the LCU used by evaluators prior to the present study was rated (on a VAS where 1 = difficult to use and 5 = easy to use) as follows:

With regard to a stated preference of LED or conventional LCUs, 13 evaluators stated that they preferred LEDs, giving reasons for their choice, such as:

‘Quieter’ (3);

‘Bright, lightweight, no heat, cordless’ (2 similar);

‘Cooler to use’ (2 similar);

‘Smaller – therefore easier to handle. No fan – quieter and good output’ (2 similar);

‘ No cord to hang over patient in a badly designed surgery’.

However, one dentist commented that his ‘halogen light still gives one of the brightest readings in the practice’. When the evaluators were asked if they were prepared to pay extra for an LED LCU compared with a conventional LCU, 80% (n = 12) stated they were.

Regarding testing the irradiance of the evaluators' current light, this was carried out by an in-built light meter by 7 evaluators, a separate light meter by 5 evaluators, while 4 evaluators used a test composite depth of cure device, with one evaluator commenting that ‘The old Ivoclar gadget is still simple and reliable’. All the evaluators (100%) stated that an in-built light meter was an advantage. The irradiance of the light was tested once a week by 4 evaluators, once a month by 4 evaluators, once every 6 months by 5 evaluators and once per year by one evaluator. No evaluator tested his/her LCU on a daily basis.

With regard to disinfecting their LCUs, wipes were used by 14 evaluators, spray by 2 evaluators and a barrier by 14 evaluators. One evaluator used an autoclave, given that he had a halogen unit with an autoclavable light tip. Typically, a combination of barrier bag and wipes was used.

The ease of cleaning of the evaluators' current LCUs was rated as follows (on a VAS where 1 = difficult to clean and 5 = easy to clean):

When asked the design of their current LCUs, the results were as follows:

Regarding weight, this was stated to be satisfactory by 93% (n = 14).

All 100% (n = 15) stated that their current light was comfortable to hold.

When the evaluators were asked how easy their current light was to place below an occlusal restoration in an UL7 in order to cure the restoration fully the result was as follows (on a VAS where 1 = difficult to place and 5 = easy to place).

Comments: ‘Depends on inter-arch space’ (3 evaluators).

Results after familiarization with the Kerr Demi-Ultra LCU

The presentation of the Kerr Demi-Ultra LCU was rated (on a VAS where 1 = poor and 5 = excellent) by the evaluators as follows:

Comments:

The evaluators rated the instructions (on a VAS where 1 = poor and 5 = excellent) as follows:

Comments:

When the evaluators were asked if the Demi-Ultra LCU was comfortable to hold, 80% (n = 12) stated that it was. Comments included:

The evaluators were asked to rate the ease of cleaning of the Demi-Ultra LCU (on a VAS where 1 = poor and 5 = excellent) with the following result:

Comments:

Replies following clinical use of the Kerr Demi-Ultra LCU

The total number of light cured direct placement restorations placed during the evaluation was 1013, comprising 190 Class I, 252 Class II, 165 Class III, 188 Class IV and 218 Class V. The Demi-Ultra LCU was used for 11 indirect restorations, treatment of dentinal hypersensitivity (6 evaluators), repair of fractured porcelain (3 evaluators), bonding amalgams (4 evaluators), and placing orthodontic brackets (4 evaluators).

Regarding the performance of the Demi-Ultra LCU in clinical use, 93% (n = 14) of the evaluators stated that the controls worked satisfactorily.

Comments included:

The weight of the Demi-Ultra LCU was stated to be satisfactory by 9 evaluators (60%). Nine (60%) of the evaluators stated that the power source/capacitor life was sufficient. Comments from the remainder were:

When the evaluators and their dental nurses were asked to rate the ease of use of the Demi-Ultra LCU (on a VAS where 1 = difficult to use and 5 = easy to use) the result was as follows:

The evaluators were asked if they considered any changes essential to the acceptability of the Demi-Ultra LCU, with the following results:

When the evaluators were asked what they liked most about the Demi-Ultra LCU, evaluators made the following comments:

Regarding the durability/reliability of the Kerr Demi-Ultra LCU, 9 evaluators rated it as ‘very’, and 2 as ‘good/average’, although 2 evaluators commented that ‘the evaluation was too short to comment on long-term durability’. Ten (67%) of the evaluators found the 40-second re-energizing a useful feature, but two commented that they ‘Didn't know about it’.

The curing time of the Demi-Ultra LCU (25 x 10 seconds on full charge) was rated as ‘plenty’ by 10 evaluators and ‘adequate’ by one evaluator, with 4 stating that it was ‘not enough, especially for orthodontic cases’.

Regarding heat generated by the Demi-Ultra LCU, 7 evaluators considered this to be ‘much less’ or ‘less’, with 7 evaluators noting ‘no difference’.

Regarding the overall rating of the Demi-Ultra LCU, 8 evaluators rated this as ‘excellent’, 3 as ‘good’, with 2 rating it as ‘below average’ and one as ‘poor’.

The evaluators were asked to rate particular features of the Demi-Ultra LCU in terms of importance (where 5 = most important and 1 = least important) with the following results:

Ten (67%) of the evaluators stated that they would purchase the Demi-Ultra LCU for use in their practice if available at an average price. Nine (60%) of the evaluators would recommend the Demi-Ultra to a colleague to use in their practice.

Final comments were:

Discussion

Light Emitting Diode (LED) LCUs use a semiconductor material system based upon gallium nitride to generate blue light of selected wavelengths of between 400 and 500 nm without needing to use filters.⁴ This has been considered to be a much more efficient means of converting electric energy into light compared with halogen light technology.⁵ Advances in LED technology have been considered to make it possible, today, to produce LED LCUs which provide an equivalent energy to high intensity halogen or plasma arc LCUs,⁴ and these new LED LCUs have become available without the need for cooling fans. In addition, the majority of LED LCUs can be battery powered because of their low power consumption.⁴ Indeed, Pelissier and colleagues, in 2011,⁶ considered that energy-efficient blue LED lights are rapidly replacing their halogen lamp predecessors as the standard light source in clinical dentistry.

From these comments, it could be concluded that LED LCUs are now state-of-the-art for the curing of resin-based restoratives in dental practice. It was therefore deemed appropriate to carry out a ‘handling’ evaluation of a recently introduced LED LCU, the Kerr Demi-Ultra, which possesses a number of novel features, such as its 40-second re-energizing feature, its ultracapacitor and the LEDs being positioned at the tip of the light, rather than the light being transmitted by a light guide. The Kerr Demi-Ultra Curing Light has therefore been subjected to an extensive evaluation by 15 members of the PREP panel in which 1013 light cured restorations were placed.

The presentation of the Unit scored very highly (4.8 on a VAS where 1 = poor and 5 = excellent) and, though the instructions scored well, comments were made that they were too voluminous and that users’ attention should have been drawn more to the 40-second re-energizing feature, this being emphasized by the fact that two evaluators stated they were not aware of this feature. Also with regard to design, the aesthetically pleasing design of the Kerr Demi-Ultra Curing Light was commented on by several evaluators. However, one comment could be considered to sum up most aspects of the Demi-Ultra, namely that it was considered to be a worthy successor to the Optilux Demetron light, for many years considered to be the gold standard.

The effectiveness of the Demi-Ultra LCU was marginally higher than the currently used LCU. The ease of use score, though above average at 3.9 (on a VAS where 1 = difficult to use and 5 = easy to use) was lower than the current LCU which scored 4.6 on the same scale. The ease of use of the control buttons when the barrier bag was in place caused several comments as did the slipperiness of the unit again when the barrier bag was in place. This may be due, in part, to the evaluators needing to use standard barrier bags at the start of the evaluation, rather than the type manufactured by Kerr specifically for their LCU which only became available later in the evaluation. Several suggestions were made to improve the design of the control buttons – these suggestions have been fed back to the manufacturer.

The pricing of the Kerr Demi-Ultra curing light would appear to be an important consideration when nearly half the evaluators would pay between £200 and £400 for an LCU of similar quality and the other half would pay a maximum of £800.

The results of the present evaluation may be considered to add to another handling evaluation of the Kerr Demi-Ultra carried out in the US, which carried out a comparison of the curing and thermal properties of the Demi-Ultra and other LCUs.⁷ These evaluators found that the depth of cure of the Demi-Ultra compared favourably with other comparable LCUs and that the maximum temperature at the light tip was the lowest of the lights that they tested.

Finally, Shortall and co-workers⁸ have produced a comprehensive and thereby useful list of the selection criteria for a clinician considering purchase of a new LED LCU. These include:

It would appear that the Kerr Demi-Ultra fulfils the majority of these criteria.

Conclusions

The number of evaluators who would purchase the Kerr Demi-Ultra curing light (67%) and recommend it to colleagues (60%) indicates the good reception of this LCU. The acceptability of the unit would possibly be further enhanced by modifying the instructions to highlight the 40-second re-energizing feature and also modification of the control button design to differentiate them and make them easier to operate when the barrier sleeve is in place.