Review of possible predictors for pain perception with class 1 5 cavity preparations using Er,Cr:YSGG laser: a retrospective clinical in vivo study

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1 Laser Dent Sci (2017) 1:9 21 DOI /s ORIGINAL ARTICLE Review of possible predictors for pain perception with class 1 5 cavity preparations using Er,Cr:YSGG laser: a retrospective clinical in vivo study Marina Polonsky 1 & Norbert Gutknecht 2,3,4 & Rene Franzen 5 Received: 10 December 2016 /Accepted: 2 March 2017 /Published online: 10 April 2017 # Springer International Publishing 2017 Abstract Aim The study recorded 400 responses from 301 patients, aged 6 93, who all had carious lesions prepared with the erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) 2780-nm laser system. Different parameters, including gender, delivery method, power settings, tooth position, class type of cavity preparation, and patients age, were compared and analyzed for possible predictive values in anticipating the patients pain experience. Methods Class 1 5 cavity preparations were made using the Er,Cr:YSGG laser. All carious lesions fit ICDAS code 4 5 classifications. Power setting of 3.75 W was used for posterior teeth class 1 4 preparations and 2.5 W for all primary teeth, permanent anterior teeth, and all class 5 preparations. Nonanxious patients, who agreed to start cavity preparation without a local anesthetic, were instructed to stop the procedure * Marina Polonsky polonmar@gmail.com Norbert Gutknecht ngutknecht@ukaachen.de Rene Franzen franzen@aalz.de Alta Vista Laser Dental Centre, Ottawa K1H 7T6, Canada Department of Operative Dentistry Periodontology and Pediatric Dentistry, Pauwelsstrasse 30, Aachen, Germany Aachen Dental Laser Center, Pauwelsstrasse 30, Aachen, Germany Postgraduate Education and Research, Pauwelsstrasse 30, Aachen, Germany AALZ GmbH-Aachen Dental Laser Center, Zentrum für Bio-Medizintechnik, RWTH Aachen Campus-Campus Melaten, Pauwelsstrasse 17, Aachen, Germany and ask for an anesthetic injection, should they perceive a level of pain greater than their tolerance level. Anxious patients were not included in this study. Pain perception using the visual analog scale (VAS) along with the percentage of patients who needed a local anesthesia injection were recorded. The data was then analyzed using one-way ANOVA test, at significance level of α = 0.05, and Tukey pair-wise comparison, at 95% confidence interval. Results Eighty-five percent of cavity preparations were pain free; 15% of the preparations were found to have a degree of pain associated with them. However, only 6% requested a local anesthetic injection. There was no significant difference found between the two methods of delivery: gold handpiece (HP) vs. turbo HP. No significant differences were observed between males and females, regarding pain perception (13% vs. 18%, respectively). Posterior teeth were significantly more sensitive to laser cavity preparation, compared to anterior teeth, as indicated by the VAS pain scores (P value = ). Regarding anterior teeth, class 5 was significantly more sensitive to laser cavity preparations, when compared to class 1. In posterior teeth, there were no statistically significant differences between class 1 and 5, although pain perception was the most prevalent in class 2 preparations. Using higher-power settings (3.75 W vs. 2.5 W) for cavity preparation, the resulting pain response was significantly higher, as indicated by the VAS pain scores (P value = ). As the patients age increases, the frequency of those experiencing pain decreases, with the exception of a sudden spike for the cohort aged 26 35, who proved to be the most sensitive to laser cavity preparation; this group was significantly different from all other age groups (P value = ). Conclusions The Er,Cr:YSGG laser system is an effective method for pain-free cavity preparations for 85% of the general patient population, who do not suffer from dental anxiety.

2 10 Laser Dent Sci (2017) 1:9 21 Certain patient selection criteria, including age, power settings, and class type of cavity preparation, are important in achieving an overall positive and pain-free expedience. Keywords Pain perception. Laser. Er,Cr:YSGG. Cavity preparation Introduction Use of the dental turbine has been the standard of practice for cavity preparations since 1945 [1], regardless of its strong association with unpleasant sounds, smells, vibrations, and the need for local anesthesia. Elimination of anxiety triggers, namely, the B4S^ rule (sights, sounds, sensations, and smells) [2] is important for all patients undergoing restorative dental procedures. The sight of a drill and a local anesthetic needle syringe, along with a high-pitched sound and high-frequency vibration of the dental turbine, are the significant sources for dental anxiety, which drive the expectation of dental pain [3 5]. Lasers have been shown to produce 400 times less vibration, than does a burr preparation [6], and achieve an improved patient experience, as evidenced by a number of pediatric studies. These findings were based upon a change to a more pleasant sound, less vibration, and to a certain degree, low-level laser therapy effect [7 9], which acts to provide a form of analgesia. Furthermore, a simple signaling system, such as a Braised hand^ to indicate discomfort and request stop of the procedure, gives control to the patient and is particularly useful in decreasing anxiety in both children and adults [10]. Hard tissue dental laser systems, like the Er:YAG 2940 nm and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) 2780 nm, can remove hard tissues, such as enamel and dentin, with minimal thermal side effects. Increased pulpal temperature, during erbium laser cavity preparation, has been shown to be equivalent to a high-speed dental turbine with water spray [11]. In fact, some research has shown a reduction in pulpal temperature with the Er:YAG preparation when compared to conventional burrs [12]. The Er,Cr:YSGG laser is a free-running pulsed (FRP) laser system which delivers energy in the mid-infrared spectrum, through a fiber-optic trunk fiber with contra-angle handpiece (HP) that resembles a high-speed drill. The removal of dental hard tissue is accomplished by a process of thermo-mechanical photon-induced, watermediated ablation. The resultant micro-explosive force of photons on water droplets is responsible for the mechanism of removal of hard dental tissues, without the thermal side effects on the pulp, which is responsible for the pain and post-operative sensitivity [13, 14]. In the last 10 years, numerous studies have been published showing reduced pain perception and improved patient acceptance of laser cavity preparations, with both the Er:YAG [15, 16] andthe Er,Cr:YSGG pulsed laser systems [17, 18]. The aim of this study was to collect a significantly large data sample, as compared to earlier studies, and secondly to explore possible links between pain perception during laser cavity preparations and other parameters. Variables, including gender, delivery method (gold HP vs. turbo HP), power settings, tooth position, class 1 5 type of cavity preparations, and the age of the patient, were compared and analyzed in the hope of giving clinicians the ability to predict the need for local anesthesia. The data was collected from the following: patients aged 6 93, class 1 5 cavity preparations, primary dentition in pediatric patients, permanent teeth in young and middle-aged adults, and medically compromised elderly patients, all of which represents the typical scope of a general dental practice. Methods and materials Patient selection This study included 301 patients (141 females and 160 males, aged 6 93), with a total of 400 cavities to be prepared, at the Alta Vista Laser Dental Centre in Ottawa, Canada. The procedure and possible side effects were explained to the patients, Fig. 1 a, b Radiographic appearance of typical carious lesions accepted into the study

3 Laser Dent Sci (2017) 1: anesthetic injection would be administered. No specific medical conditions were excluded from this study. Patients who were too apprehensive to consider dental work without anesthetic were not included. Recurrent decay under existing composite restorations was accepted in the study. Laser parameters The Er,Cr:YSGG 2780-nm, free-running pulsed laser system with fiber-optic trunk fiber delivery system using a gold HP or a turbo HP paired with an MZ6 (600 μm) or MX7 (700 μm) fiber tips, respectively. For all class 1 4 preparations in the posterior teeth, the following laser parameters were used: pulse duration 60 μs (H mode), power 3.75 W, repetition rate 15 Hz, pulse energy 250 mj/pulse, fluence 50 J/cm 2 for MZ6 tip in gold HP and 65 J/cm 2 for MX7 lens in turbo HP, and air/ water spray 60% A/80% W. For primary teeth, anterior teeth, and all class 5 preparations, the following laser parameters were used: pulse duration 60 μs (H mode), power 2.5 W, repetition rate 15 Hz, pulse energy 165 mj/pulse, fluence 33 J/cm 2 for MZ6 tips in gold HP and 43 J/cm 2 for MX7 lens in turbo HP, and air/water spray 60% A/80% W. Fig. 2 a, b Pre-op and post-op photos of typical carious lesions accepted into the study and informed consent was obtained (from a guardian, with pediatric patients). To be included in the study, patients had to have been diagnosed with clinically and radiographically significant carious lesions according to ICDAS (code 4 5) [19], which extended mm into dentin (Figs. 1 and 2). Patients also had to be agreeable to trying the cavity preparation with the Er,Cr:YSGG laser system and without a preliminary injection of local anesthetic. This agreement implied a certain degree of comfort with dental procedures and lack of anxiety. All patients were assured that should they desire anesthesia, the procedure would be stopped and a local Clinical procedure The HP was held at a 45 angle to the surface of the tooth and pointing away from the pulp. The tip distance from the surface was 3 mm for the MX7 lens in turbo HP, as this is the focal point for this type of laser delivery system. With MZ6 tip in gold HP, the laser energy is divergent as it leaves the tip and, therefore, was held 1 mm away from the surface to be ablated this maximizes the energy density and still has a sufficient layer of water between the tip and the tooth surface. MZ6 tips were discarded after each cavity preparation, as per manufacturer recommendations. The laser parameters were not changed during the entire tooth preparation. No laser analgesia pre-conditioning techniques were used prior to commencing cavity preparations Fig. 3 Pie chart of overall study results

4 12 Laser Dent Sci (2017) 1:9 21 Table 1 Results for gender and delivery method comparisons Male vs. female Gender Total Pain Anesthetic Cold Average pain Average pain (non-zero) Male Female Total Male 56% 13% 6% 6% Female 44% 18% 7% 6% Total 100% 15% 6% 6% Gold vs. turbo Delivery Method Total Pain Anesthetic Cold Average pain Average pain (non-zero) Gold Turbo Total Gold 50% 15% 7% 3% Turbo 50% 15% 6% 9% Total 100% 15% 6% 6% [20]. Patients who completed the procedure without the need for anesthesia were asked if they experienced (1) nothing, (2) cold sensitivity, or (3) pain. If the response was pain, patients were then asked to use the visual analog scale (VAS) to further quantify the level of pain. A score of B0^ means no pain at all, whereas a score of B10^ means the worst pain imaginable. Patients, who requested that the procedure be stopped to administer an anesthetic injection, were also asked to rate their level of pain, according to the VAS, immediately following the procedure. Patients who felt cold sensation, but did not perceive it as pain, were grouped together with Bno pain^ cohort. Verification of preparation completion was performed with one-fourth or one-half LA round burrs in a slow-speed turbine, depending on the size of preparation. Final decontamination and smear layer removal were completed using the following settings: power 2.5 W, repetition rate 50 Hz, 80% W/60% A Fig. 4 Bar graph showing gender comparison

5 Laser Dent Sci (2017) 1: used to analyze the data collected. Minitab statistical software used for data analysis. Results Fig. 5 Photo comparing turbo HP with MX7 lens tip and gold HP with MZ6 tip spray, pulse duration 60 μs (H mode), pulse energy 50 mj/ pulse, fluence MZ6 10 J/cm 2, and fluence MX7 13 J/cm 2,with the same HP and tip as the entirety of the cavity preparation. Restorative materials Futurabond DC self-etching adhesive bonding system (Voco, Germany) and GrandioSO flowable and hybrid composite resin (Voco, Germany) are the restorative materials. Statistics One-way ANOVA at α = 0.05 significance level and Tukey pair-wise comparisons at 95% confidence interval (CI) were The study prepared, in total, 400 cavity preparations on 301 subjects (141 females and 160 males), aged The time allotted for the procedure was the same as for a conventional high-speed drill preparation. Cavity preparations with the Er,Cr:YSGG laser system were pain free in 85% (331) of all cases (Fig. 3). Pain perception was reported in 15% (59) of all preparations (28 males and 31 females). Out of the 15% which were painful, only 6% (25) required local anesthesia (13 males and 12 females). The differences between the male (13%) and the female (18%) positive response to pain perception were not statistically significant, 4.4 average non-zero VAS pain score for positive responses in males and 5.1 average nonzero VAS pain score for positive responses in females (Table 1 and Fig. 4). The comparison of two different delivery methods (Fig. 5), the gold HP with MZ6 tip and the turbo HP with MX7 lens tip, also revealed no significant differences (Fig. 6), a finding which was surprising considering that there is a 33% higher fluence when using the turbo HP. Using the gold HP with MZ6 tip resulted in 15% (30) positive VAS pain scores, and 7% (14) needed local anesthesia. Fig. 6 Bar graph showing gold HP vs. turbo HP comparison

6 14 Laser Dent Sci (2017) 1:9 21 Fig. 7 Bar graph showing power setting comparison When using the turbo HP with MX7 lens, 15% (29) of patients had a positive VAS pain score; however, only 6% (11) asked for local anesthesia. Positive pain responses for gold HP MZ6 were similar in the anesthetic (VAS 3 8) and no-anesthetic (VAS 2 7) groups, with an average non-zero value of 4.7. Positive pain responses for turbo MX7 were similar in anesthetic (VAS 2 7) and no-anesthetic (VAS 1 6) groups, with an average non-zero value of 4.8 (Table 1). One minor difference, though not statistically significant, occurred with those experiencing cold sensitivity; 5 (3%) patients reported this effect with the gold MZ6 and 18 (9%) with the turbo MX7 (Table 1). Patients that felt pain, but opted to continue without anesthetic, explained their reasoning for this option; the 2 3 hours of numbness left them in a worse state than a few seconds of perceived pain during the laser cavity preparation. Pain perception was reported in 8% (18/219) of cavities prepared with lower 2.5-W power setting and in 23% (41/ Fig. 8 Tukey pair-wise comparison showing 95% confidence interval and significant difference in power settings

7 Laser Dent Sci (2017) 1: Table 2 Results for power setting and tooth position comparisons Power Total Pain Anesthetic Cold Average pain Power comparison 2.5 W W Total Tooth position comparison Anterior Posterior Total Average pain (non-zero) 181) of cavities prepared with the higher 3.75-W power setting (Fig. 7). The one-way ANOVA test and Tukey pair-wise comparison, with 95% CI, showed significance to P value = (Fig. 8). In patients who did experience pain, the VAS scores ranged from 1 to 7 (average 3.8) in the 2.5- W group and from 2 to 8 (average 5.2) in the 3.75-W group. Only 4 out of 18 patients with pain perception from the 2.5-W group requested anesthesia (VAS score = 2 7); 21 out of 41 patients who experienced pain in 3.75-W group ended up requesting anesthesia (VAS score = 2 8) (Table 2). When comparing the results for anterior vs. posterior teeth, they are quite similar to the power setting comparison (Table 2); 4% (6/134) of anterior teeth and 20% (53/ 266) of posterior teeth felt pain during laser cavity preparation (Fig. 9). The one-way ANOVA test and Tukey pair-wise comparison, with 95% CI, also showed significance to P value = (Fig. 10). In the patients who experienced pain, the VAS scores ranged from 2 to 6 (average 3.7) in anterior teeth and from (average 4.9) in posterior teeth. None of the patients who experienced pain sensation in anterior group requested local anesthesia, whereas 25 out of 53 patients who experienced pain in posterior teeth (VAS range 2 8) chose to complete the cavity preparation following a local anesthetic injection (Table 2). When looking at class 1 5 comparisons, in anterior vs. posterior teeth, we chose not to include 16 preparations on primary teeth due to the lower-power settings used for posterior class 1 and 2 cavity preparations. In total, 384 cavity preparations from 288 subjects (129 females and 159 males), aged 8 93, were included for this analysis. The anterior class 1 5 comparisons for pain responses are illustrated in Fig. 11. The one-way ANOVA test and Tukey pair-wise comparison, with 95% CI, showed significance to P value = for class 1 and class 5 groups (Fig. 12). The small sample size of the class 3 and class 4 groups, at 3% each, was not large enough to show any significant differences with other classes of preparations. Of the 4.5% (6/134) of patients who experienced pain, 4 of them were from the class 5 group, 1 from the class 1, and lastly 1 from class 2. The VAS pain scores ranged from 2 to 6 (average 3.7). None of the patients who experienced pain chose to receive local anesthesia (Table 3). Posterior class 1 5 comparisons (Fig. 13) did not show any statistically significant differences in pain perception between them (Fig. 14). The class 4 group showed the lowest pain perception; however, due to the small sample size of 0.4% (1/250), this finding can be disregarded. Of Fig. 9 Bar graph showing tooth position comparison

8 16 Laser Dent Sci (2017) 1:9 21 Fig. 10 Tukey pair-wise comparison showing 95% confidence interval and significant difference in tooth position the 20% (52/250) of preparations where pain was experienced, the highest number, at 25% (33/132), was from class 2 group, followed by 17% (2/12) from class 3 group, 17% (7/41) from class 5 group, and 16% (10/64) from class 1 group (Table 3). The VAS pain score average was 4.9 for the posterior teeth; the highest (5.4) belonged to class 1, followed by (4.9) in class 2. Classes 3 and 5 both averaged a 4.5 VAS pain score. Of the 48% (25/52) of cavity preparations in which pain was experienced, a local anesthetic was requested before completion in 17 cases from class 2, 4 from class 1, 1 from class 3, and finally 3 from class 5. Although differences between posterior classes were not statistically significant, most of the pain perception and request for local anesthesia were found in the class 2 preparations. The class 5 posterior group scored similar, with respect to pain perception, even though the preparations were performed with a lower-power setting of 2.5 W. This suggests that the cervical area is more sensitive than all other tooth surfaces. Class 5 anterior teeth and class 5 posterior teeth showed similar levels of pain perception, since both were prepared with the same power setting, at 2.5 W (Fig. 15). This again confirms that the difference found between anterior and posterior teeth is a function Fig. 11 Bar graph showing anterior class 1 5 comparison

9 Laser Dent Sci (2017) 1: Fig. 12 Tukey pair-wise comparison showing 95% confidence intervals and significant difference between class 1 and class 5 cavity preparations of the power settings used and not the anatomical differences between anterior and posterior teeth. In our final analysis of the data, we tried to narrow down the age group most likely to experience pain with laser cavity preparations, by separating primary teeth from permanent, then further sub-dividing permanent dentition data into 10- year age span groupings (Fig. 16). Pain perception was found to be the highest in the age group, from which 55% (21/ 38) felt pain, with 34% (13/38) requesting local anesthesia, Table 3 Results for anterior and posterior class 1 5 comparison Total Pain Anesthetic Cold Average pain Anterior class Class I Class II Class III Class IV Class V Total Posterior class Class I Class II Class III Class IV Class V Total Average pain (non-zero) with average VAS pain score of 5.8. This group differed significantly from all other age groups, according to one-way ANOVA test and Tukey pair-wise comparison, showing 95% CI, with P value = (Fig. 17). In primary teeth preparations, 6% (1/16) of patients felt pain, though none asked for anesthesia, with the average VAS pain score at 4.0. In the 8 14-year age group, 17% (2/12) felt pain and 8% (1/12) asked for anesthetic, with an average VAS pain score at 5.5. In the year age group, 8% (3/39) felt pain with 3% (1/39) asking for local anesthetic, with an average VAS pain score of 5.3. In the year age group, 18% (7/39) felt pain with 8% (3/39) asking for local anesthetic, with average VAS pain score of 4.7. In the year age group, 17% (14/ 81) felt pain with 8% (5/81) asking for local anesthetic, with an average VAS pain score of 3.6. Out of remaining three age groups, 1% (2/193) felt sufficient pain to request a local anesthesia injection, with progressively less pain being felt with increasing age. Pain experiences in this older cohort are as follows: 9% (7/78) in the year age group, 5% (3/58) in the year age group, and 4% (1/39) from the 76+ year group (Table 4). Discussion The aim of this study was to assess variations in pain perception (and need for local anesthesia) with respect to multiple parameters, namely gender, delivery method, power settings, tooth position, class 1 5 type of cavity preparation, and patient age. To the best of our knowledge, this is the largest retrospective in vivo clinical study ever carried out, using

10 18 Laser Dent Sci (2017) 1:9 21 Fig. 13 Bar graph showing posterior class 1 5 comparison the Er,Cr:YSGG laser for cavity preparation. There were 400 cavities prepared in 301 patients, aged 6 93, which is representative of a typical population in a general dental practice. Of all the scientific research conducted and published, within recent years, pulsed laser systems, like Er:YAG and Er,Cr:YSGG, have been shown to be equally as safe as mechanical high-speed drills, with respect to pulpal temperature rise [21]. The speed of cavity preparations has also increased with the development of lasers with shorter pulse duration and higher peak powers, as compared to older generation lasers. The speed of these devices is now similar to preparations carried out with high-speed drills, particularly in carious tooth structure. In fact, the ability of this laser system to remove tissues with higher water content (like carious dentin) faster than healthy tooth structure offers a unique minimally invasive, selective caries removal potential [22]. Lasers also demonstrate many other benefits, including a caries-preventive effect [23, 24], reduced need for acid etching of the prepared tooth structure [25], improved bond strength in composite resin restorations and glass ionomer cements [26], and a comparable degree of micro-leakage with solvent-free bonding agents, as compared to conventional rotary instruments [27]. Fig. 14 Tukey pair-wise comparison showing 95% confidence intervals and no significant differences

11 Laser Dent Sci (2017) 1: Fig. 15 Tukey pair-wise comparison showing 95% confidence intervals for anterior class 5 vs. posterior class 5 and no significant difference Additionally, cavity disinfection of up to 0.5 mm below the surface was observed using the Er,Cr:YSGG laser system [28]. The non-contact mode of operation of this laser system offers patients the benefits of no vibratory sensations and a lack of the typical Bdrill^ noise. As the tip is not in contact with the tooth surface, this method of cavity preparation is much more agreeable to the patient [6 8]. In addition, many other studies have reported that lasers produce a mild local anesthetic effect, which allows for shallow cavity preparations to be completed without local analgesia [9, 29]. Pain perception, however, during different types of laser cavity preparations remains unpredictable and is a puzzlement to many dental practitioners. The consensus is that around 80% of cavity preparations can be completed without dental anesthesia, which is greatly encouraging for a positive patient experience [30 32]. Our study gives further support to these claims that laser-induced analgesia leads to improved patient comfort, in up to 85% of patients. Pain perception is neither affected by gender nor by the delivery method. Anterior teeth were shown to be significantly less sensitive than posterior teeth, likely due to lower-power settings used to complete these preparations. Within anterior teeth, class 1 preparations were significantly less sensitive than class 5 lesions and that Fig. 16 Bar graph showing age group comparison

12 20 Laser Dent Sci (2017) 1:9 21 Fig. 17 Tukey pair-wise age group comparison showing 95% confidence intervals and significant difference in year-old group class 5 preparations were the most sensitive of all preparations performed under lower-power settings. This indicates that the cervical area of the tooth is more likely to elicit a pain reaction, when using lasers for preparations. In posterior teeth, pain was most prevalent in class 2, though not to a statistically significant level. A closer look at prevalence Table 4 Table summary of data for primary teeth and 10-year span age group comparison Age Total Pain Anesthetic Average pain Average pain (non-zero) Primary Total Primary 4% 6% 0% % 17% 8% % 8% 3% % 55% 34% % 18% 8% % 17% 6% % 9% 1% % 5% 0% % 3% 3% Total 100% 15% 6% 0.7 h4.8 of pain, with respect to patient age, found that young adults, age 26 35, are the most likely to experience pain with laser preparations, when using the Er,Cr:YSGG system. This finding mimics the dental anxiety study by Stouthard et al. [33], whereby the year age group was the most likely to experience high levels of dental anxiety. Future studies should focus on finding ways to reduce levels of dental anxiety in young adults to help improve their experience with laser cavity preparations. Investigations into using different wavelengths for preconditioning analgesia may also prove beneficial in the following: preparations of deeper carious lesions, improving success rates in the more sensitive class 5 cases, and in posterior teeth where higher-power settings must be used to avoid prolonged working time. Conclusions From the results of our retrospective in vivo clinical study, and within its limitations, it can be concluded that the Er,Cr:YSGG laser system has demonstrated a lack of pain perception in 85% of the cavity preparations in non-dentally anxious population. In young adults, aged 26 35, the success rate drops significantly to 45%. Power settings used to perform caries removal play a significant role in inducing pain perception. Class 5 is the most painful of all cavity preparation in anterior teeth,andclass2isthemostpainfulcavitypreparation in posterior teeth. Using higher power in posterior teeth leads to significantly higher pain, as reported in 79% of the cases. Lastly, using lower-power settings in anterior teeth increases the pain-free experience up to 96%.

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