Previous dental experiences and associated pain or anxiety can negatively affect children’s cooperation during subsequent dental visits. Effective pain management ensures a positive dental attitude, encourages patient cooperation, and fosters trust in the dental environment. However, pain management methods, including local anesthetic injections, can lead to several side effects, such as discomfort, severe needle phobia, and increased general anxiety, mistrust, and nervousness in children. As a result, there has been a growing interest in alternative pain management strategies, remarkably non-invasive and minimally invasive techniques such as low-level laser therapy and acupressure, to provide painless dentistry for children (1–7).

Low-level laser therapy (LLLT), recently recommended in the literature as photobiomodulation (PBM), involves the application of low-intensity laser or diode light with specific wavelengths. It has several biological interactions with irradiated tissues, stimulating cellular activity and promoting tissue repair (8). The exact mechanism by which PBM produces its analgesic effects is not fully understood. However, it has been suggested that LLLT may provoke several mechanisms responsible for pain sensation, such as modulation of the inflammatory response in tissue, stimulation of the body’s natural pain-relieving mechanisms, and direct effects on nerve fibers (9). PBM works by inhibiting pain transmission signals through the impact on nociceptors and reducing the release of pro-inflammatory mediators like prostaglandins and cytokines. Studies have shown that PBM is more effective in reducing pain associated with C fibers than A-delta fibers, supporting the hypothesis that it may preferentially target specific nerve pathways involved in pain transmission (8, 10). This has important clinical implications. Furthermore, PBM increases the production of endogenous opioids, such as endorphins, which contribute to pain relief (11). These mechanisms make PBM a promising non-invasive alternative to conventional pain management strategies in pediatric dentistry. However, the effectiveness of LLLT may vary based on different dental procedures and individual patient characteristics related to pain and anxiety (12–17).

Molar incisor hypomineralization (MIH) is a developmental disorder that affects dental enamel, primarily impacting the newly erupted first permanent molars and permanent incisors (18). Teeth affected by MIH are more prone to caries, and defective tissues are easily fractured under normal chewing forces. Abnormal tissue morphology and composition result in hypersensitivity to external stimuli such as cold and air, and even worsen the difficulty in achieving adequate local anesthesia. This makes dental treatment challenging for this group of patients.

Data from the literature showed the prevalence of MIH from 3.6 to 25%, depending on various populations. The etiology of MIH is complex. Some etiological factors are hereditary, while others remain unexplained (19, 20). A well-balanced diet is crucial for the proper formation and mineralization of dental tissue, beginning in the embryonic period when tooth buds start to develop and continuing throughout pregnancy (21). During pregnancy and lactation, there is an increased demand not only for energy but also for a range of vital nutrients and minerals. Key minerals include calcium, phosphorus, magnesium, iron, zinc, copper, iodine, and selenium. Additionally, important vitamins that should be included are: D, A, B1, B2, niacin, choline, pantothenic acid, B6, B12, C, E, and folate (21). By managing maternal nutrition, it may be possible to mitigate the risk of dental abnormalities associated with inadequate intake of essential structural materials. Among other considerations in the study of Mafla et al., mothers’ psychological factors (depression, eating disorders, and intake of alcohol) were significantly linked to the presence of MIH (22). Other authors indicated that prenatal maternal infection, premature birth, and postnatal childhood infections (chickenpox, parotitis, measles) were significantly associated with primary teeth hypomineralization and MIH (23). There is a clear lack of direct correlation between molar incisor hypomineralization and congenital disorders. However, it is essential to recognize that during surgical procedures, mechanical trauma to the developing tooth buds may result in structural or morphological alterations. These changes could clinically resemble the hypoplasia commonly described in the literature, rather than the hypomineralization typically associated with MIH (24).

Effective management of dental procedures relies on successful local anesthesia, which is particularly important for children with MIH who may experience heightened sensitivity and discomfort even to tooth brushing (25). Hypomineralized tissues, such as altered enamel and dentin, can hinder the diffusion of anesthetics and reduce the effectiveness of local anesthesia. It clinically results in observed high pain levels and an anxious attitude in children affected by MIH. Because of these challenges, it is essential to research supplemental approaches that can enhance the pain management for this group of patients (26, 27).

Low-level laser therapy (LLLT), recently known as photobiomodulation (PBM), has emerged as a viable supplementary treatment for various medical and dental applications (28). PBM has garnered increased interest in dentistry due to its potential benefits, including enhancing the effects of local anesthesia, accelerating wound healing, and managing pain and inflammation (29). Recent research indicates that PBM increases the permeability of nerve cells, facilitating easier diffusion of anesthetic drugs, leading to faster onset and longer duration of LA. Additionally, studies have shown that PBM can alter nociceptive pathways, reducing pain perception (30–33).

Presently, the clinical studies presented the impact of Photobiomodulation Therapy (PBMT) on pain management during local anesthesia injections in children affected by MIH are scarce (32, 33). Additionally, it is emphasized that altering laser parameters, such as wavelength, energy, fluence, mode, and time of irradiation, can produce different clinical outcomes. Therefore, evaluating the analgesic effects of various laser protocols on pain control during injections is a reasonable approach (31–34).

This study evaluates the additional effect of PBM on local anesthesia efficacy in maxillary permanent molars affected by MIH.

Forty-five children diagnosed with MIH, aged between 7 and 15 years (mean age 11.2 ± 2.1) from the Pediatric dentistry clinic, Poznan, Poland, were taken for the study (Table 1). It has been reported that 60% (n = 27) of participants were affected by MIH, with only molars involved; hypomineralized incisors and molars were found in 40% (n = 18) of children.

Patients with decayed maxillary molars on both the right and left sides, who were indicated for an invasive procedure requiring local anesthesia, were enrolled in the study. They were then randomized into two groups: the intervention group (which received photobiomodulation therapy in addition to standard anesthesia) and the control group (which received standard anesthesia alone). Each group consisted of 45 teeth.

The patients were scheduled for two visits within 10 days to treat both maxillary molars. The heart rate, other symptoms accompanying the procedure (sweating, skin reactions, hyperventilation), ball squeezing test, VAS, and FLACC scale were recorded in the patients before and after administration of local anesthesia.

It has been reported significantly lower pain perception in the intervention group than the control group (mean VAS score: 2.1 ± 0.8 vs. 6.2 ± 1.2, p < 0.001) (Table 2). Additionally, a greater proportion of participants in the intervention group reported only minimal pain (55.6%), while the control group had the same proportion reporting severe pain (55.6%) (Figure 3).

According to the FLACC scale, patients from the intervention group showed significantly lower pain perception than the control group (median values 3, vs. 7, p < 0.001) (Table 3).

They presented only mild discomfort in the PBM group vs. severe pain in the control group, where supplemental anesthesia was needed (Figure 2).

Participants in the control group represented higher mean HR scores, 113.2 ± 6.1 and 84.6 ± 6.1, respectively, in the intervention group, p < 0.001 (Figure 4). First measurements HR1, before PBM, showed no significant differences between groups (p = 0.624). However, the second measurements, H2, after PBM and local anesthesia, demonstrated significant differences, p < 0.001 (Table 4).

Pain sensation assessed by squeezing balls held in the patient’s hands was higher in the control group, and 66.7% (p = 0.006) of children squeezed both balls, signaling strong pain (Table 5). In the PBM group children demonstrated little pain squeezing one ball, and only at the beginning of the clinical procedure. This test provides a practical and reliable method for assessing pain perception in pediatric patients, and the results further support the effectiveness of the intervention in reducing pain.

The most common symptom representing anxiety and pain was sweating observed on the forehead in 5 (11.1%) patients from the control group, followed by hyperventilation and skin reactions (Table 6).

Anxiety triggers various psychophysiological responses, primarily linked to increased activity in the sympathetic branch of the autonomic nervous system. This affects several bodily systems: cardiovascular system (an increase in blood pressure and heart rate), sweat glands (heightened sweat production and increased electrical conductivity of the skin), muscles (muscle tone increases, leading to spasmodic movements and tension), respiratory system (sighing and a feeling of breathlessness), digestive system (dry mouth and constipation). All of these physiological changes can be used to assess a patient’s anxiety levels (2).

In the intervention group, a significantly faster beginning of anesthesia effect was observed than in the control group (mean onset time: 3.6 ± 0.9 min vs. 6.1 ± 0.8 min, p < 0.001). Additionally, the extent of anesthesia was significantly longer in the intervention group (mean duration: 70.2 ± 3.9 min vs. 50.7 ± 8.9 min, p < 0.001) (Table 7).

Pediatric patients in a dental office can exhibit nervousness, fear, and distrust based on their background, age, and developmental skills. In anxious situations, children may show signs of fear and agitation. These can include deep breathing, shivering, crying, or becoming withdrawn and refusing to speak or play. If the stress continues for a long time, it might affect the pain perception. Children might express their discomfort before a procedure by trying to fight or run away. This reaction can be emotionally distressing for the child, their parents, and the dental professionals involved (1–7).

Children with MIH often experience high levels of dental anxiety and difficulty tolerating treatment due to sensitivity and previous painful dental experiences. Affected enamel is softer, more porous, and prone to breakdown under regular chewing forces. Leads to post-eruptive enamel breakdown (PEB) soon after eruption when young patients are more sensitive to unpleasant situations (18, 25). Successful adhesion with recommended self-etching adhesives provides better bond strength to hypomineralized enamel than all-etch single-bottle alcohol-based adhesives. It has also been proposed to pre-treat the enamel with 5% sodium hypochlorite in order to remove intrinsic proteins encasing the hydroxyapatite and therefore facilitate etching and resin penetration. This method of covering crowns affected by MIH with composite can help reduce hypersensitivity and pain sensation in those patients (42).

Premature tooth loss necessitates orthodontic treatment, which can be particularly challenging for patients affected by MIH. Cohesive failures are common with brackets bonded to MIH-affected enamel, primarily due to reduced bond strength, which can result in enamel surface fractures when the brackets are removed. Frequent rebonding of these attachments can slow down the progress of treatment with fixed appliances (43). Considering that bonded molar tubes show a higher failure rate and more decalcification than do molar bands, it seems reasonable to choose orthodontic bands in patients with severely MIH-affected molars. It is important to emphasize that orthodontic bands can create additional areas for dental plaque retention, making proper oral hygiene more challenging and increasing the risk of caries. Severely affected teeth with MIH and extensive restorations can greatly benefit from the use of orthodontic bands, which serve as temporary retainers, maintaining these restorations for a period sufficient to postpone definitive rehabilitation after orthodontic treatment. Beyond the consideration of adhesive challenges, cases involving functional appliances using molar clasps (e.g., Twin-block) for retention may require modification of the appliance design or consideration of alternative treatment approaches (e.g., aligner technique) (44). Extracting severely affected molars at 8–10 years old has been demonstrated to result in optimal spontaneous space closure. After 10 years old, if extraction is considered, there is a higher likelihood of experiencing failure in spontaneous space closure, poor angulation, and an unsatisfactory contact point relationship with the second premolar. In addition, orthodontists should confirm the presence of the third permanent molar once studies have suggested a possible association between MIH and dental agenesis (45).

Measuring pain in children is particularly difficult. However, they often have a particular vocabulary, fewer experiences, and rely on fearsome stories from family or peers that may significantly affect their ability to express themselves, especially in a new, anxious situation. Children’s reaction to pain and ability to describe it are influenced by various factors such as their developmental stage, environment, anxiety, and psychological aspects. Therefore, it seems crucial to introduce more objective and adaptable pain measures for children (3, 38, 41, 46).

This study aimed to evaluate the potential of pre-treatment photobiomodulation to reduce the pain experienced by patients during the treatment of decayed maxillary molars affected by molar-incisor hypomineralization. PBM appears to be a promising method for minimizing pain associated with injections, providing children with a more comfortable dental experience.

Some studies have recently investigated the effect of PBM on injection pain in healthy adult patients, which is consistent with our results and explains the analgesic properties of LLLT. Presently, a few studies have addressed this topic in children, and each study represented a different protocol regarding the laser type and parameters, the method of application, mode, sample chosen, and specific teeth and anatomical area tested (46, 47). Different study protocols, methodologies, and designs made the analysis incomparable. Nevertheless, studies on MIH patients are minimal, and the results may differ according to particular hypersensitivity and pain level in this group of children (32, 33).

In our study evaluating the effectiveness of photobiomodulation, we used a diode laser with a wavelength of 635 nm and an energy density of 12 J/cm² for the intervention group. It has been reported in several studies that PBM is most effective within a therapeutic wavelength range of 630–940 nm, as this range allows for deeper tissue penetration and produces beneficial biological effects in the targeted area (47). Cronshaw et al. conducted a systematic review and meta-analysis, which indicated that the recommended dose for pain relief using PBM in contact mode with tissues falls between 10 and 30 J/cm² (48). According to this recommendation, we designed our laser protocol in the intervention group.

The effectiveness of laser PBM for pain relief is still under investigation. Some studies have examined the combined effect of topical anesthetic gel and laser PBM, while others have focused solely on the impact of laser PBM (31, 46, 47, 49). This diversity in research protocols has rendered the results of trials found in the literature inconsistent, highlighting the necessity and value of our study design.

We applied a 5% lignocaine gel, the most common and effective topical anesthetic in pediatric dentistry, for both the intervention and control groups. In some studies, a 20% benzocaine gel was used exclusively in the control group, while in another study, a pre-anesthetic topical gel was applied to all participants (49). Several studies have reported that the topical anesthetic benzocaine may cause allergic and toxic reactions, such as methemoglobinemia. For this reason, we chose to use lignocaine gel before injection for both group in our study (49).

Various authors have combined different techniques before administering injections to reduce pain associated with local anesthesia delivery (49, 50). Sattayut (50) conducted research to compare the effects of a 780 nm diode laser, benzocaine, local mechanical pressure, and light touch during palatal injections. They found no statistically significant differences in pain scores among the low-intensity laser (administered with an energy of 3.6 J), 20% benzocaine, mechanical pressure, and light touch (50).

The question was how the type of dental procedure might influence the analgesic effect of LLLT. Tuk et al. (51) investigated the effects of an 810 nm diode laser to assess the analgesic benefits of low-level laser therapy (LLLT) on injection sites in patients scheduled for third molar removal. They reported that the laser, with an applied energy of 5.94 J, did not significantly reduce the pain experienced during local anesthetic injections before the surgery (51).

Our study did not replicate the findings of Ghabraei et al. (52), who reported no significant difference in pain levels between the laser and placebo groups. However, our research specifically focused on patients with a history of MIH, which differs from the criteria used by Ghabraei et al. (52). In our trial, we included patients with MIH who experienced higher pain levels, and we reported differences in pain scores measured using the VAS and the FLACC scale. Also, the physiological symptoms of pain and anxiety (sweating on the forehead, hyperventilation, and goose bumps) were more common in the control group compared to the PBM group (20% vs. 8%).

Our results agreed with Shekarchi et al. (31), who revealed that laser PBM significantly decreased the injection pain. They tested the effect of PBM using an 808 nm diode laser, with 250 mW power and 32.5 J/cm² fluence in contact mode for 65 s, compared to topical anesthetic gel. It has been demonstrated that the lower pain level experienced in the PBM group may be connected with the analgesic effect of the light–tissue interaction (31).

Moreover, our results did not align with those of Uçar et al. (46). Researchers were studying the effects of PBM, both alone and in combination with topical anesthesia, such as gels. In this study, an 810 nm diode laser with a power of 0.3 W and a fluence of 69 J/cm² was used for 20 s in non-contact mode. They found no statistically significant difference between the two groups; however, the topical anesthesia and PBM group reported higher ‘no pain’ scores (46). In comparison to our study, they utilized different laser parameters, and their patients age and health status varied.

Furthermore, Elbay et al. (47) found no statistically significant difference in pain experiences between the group that received photobiomodulation (PBM) combined with topical anesthesia and the group that received placebo PBM and topical anesthesia. They evaluated the effects of various PBM parameters using a 940 nm diode laser in non-contact mode, with fluence levels of 69, 103, and 138 J/cm² (47). The results of Elbay et al. (47) study showed no statistically significant differences in heart rate (HR), facial pain scale (FPS), and subjective evaluation of anesthesia (SEM) between the two groups during the pulpotomy and stainless steel crown (SSC) procedures. This study revealed that the effectiveness of local anesthesia was comparable in the PBM and control groups (47).

In our study, heart rate as an objective pain survey, measured before LA and during procedure, demonstrated lower mean scores after 10 min in the PBM group (84.6 bpm ± 6.1) versus the control (113.2 bpm ± 6.1). Still, there was no statistically significant difference between groups. Similarly, the ball squeezing test demonstrated higher response to pain sensation in the control group, where both balls squeezed 66.7% of children and 37.8% in the PBM group, with no statistically significant differences (p = 0.006).

Aykanat and Elbay (32) conducted a study on children aged 7–12 years, using photobiomodulation with a diode laser at 940 nm in continuous mode, at a power of 0.5 W and an energy density of 78 J/cm². LLLT was performed before LA and planned pulp treatments (32). It has been demonstrated less pain sensation after PBM, as “no-pain” was declared by 29% of patients in the laser group and 20% in the control group. Moreover, the control group reported moderate-to-high pain levels more frequently than the experimental group (43% vs. 20%). Lower pain perception after PBM may correspond with the need for additional anesthesia. It has been noted that 49% of the control group needed supplemental injection during the treatment of teeth affected by MIH, and only 31% of the experimental group (PBM). Nevertheless, it has no statistically significant difference between the laser and control group (32).

Other studies done by Shahnawaz et al. (33) examined 70 participants with MIH. They reported higher anesthesia efficiency in the intervention group (PBM), a faster onset, and a longer duration of anesthesia with significantly lower pain perception than the control group (33). It corresponds with our findings, where in addition to more efficient pain control and lower pain perception, the intervention group reported a faster onset of anesthesia, with an average onset time of 4.2 min compared to 6.7 min in the control group. Our observations suggest that PBM combined with computer-controlled local anesthesia delivery (CCLAD) may improve the anesthesia effectiveness: faster onset and prolonged action without unpleasant sensations at the stage of initial delivery of anesthetic solution into the tissue. It has a positive impact on dental treatment in children, permitting faster initiation of dental procedures. Furthermore, the prolongation of anesthesia was higher in the intervention group, averaging 75.4 min compared to 65.3 min in the control group. The extended duration of anesthesia in the intervention group suggests that PBM may also provide better control over pain for a more extended period, which is often needed to perform a procedure in young patients.

Research indicates that PBM can effectively reduce children’s pain during dental treatments and improve patient comfort, particularly for teeth affected by MIH. It can foster a more positive view of dental care, building trust and cooperation between children and dental professionals. The study’s results showed that in the intervention group, PBM had a positive impact on pain management while treating maxillary permanent molar teeth affected by MIH.

Children who received photobiomodulation in addition to standard anesthesia reported significantly lower pain levels during dental procedures compared to those who received only standard anesthesia. The mean Visual Analog Scale (VAS) score for pain perception in the intervention group was 2.1, notably lower than the control group’s mean score of 4.5. Respectively lower pain score observed in FLACC scale in intervention group (median 3 [1–5]) and in control group median 7 [5–8], is significant, p < 0.001. This suggests that PBM can be an effective tool in reducing pain during dental procedures for children with MIH.

The pain perception and origin of sensations, central sensitization, and somatization are well-studied in adults; however, they have not yet been thoroughly examined in children. The reactions and perceptions of these pain phenomena in children differ markedly from those in adults. Conducting further research in this age group will provide valuable insights into effective pain management (53).

MIH strongly impacts patients at a functional and aesthetic level. Patients with this dental condition often describe not only pain and hypersensitivity, but also problems when chewing, smiling, and speaking. Esthetically, MIH has a great impact when it occurs in the anterior teeth (54). Studies showed an increase in the prevalence of caries in patients with MIH. In severe cases, MIH can lead to enamel fracture and premature tooth loss. This also has an impact on oral-health-related quality of life (55).

Based on the results of our study, PBM may be recommended as a non-pharmacological pain management technique for treating children with MIH, where local anesthesia alone is not effective. This approach of pain control minimizes pain during LA injections and fosters trust in children, ultimately leading to better behavior and cooperation during subsequent dental treatments.

The results of this study indicate that photobiomodulation improves pain management in maxillary permanent molar teeth affected by molar incisor hypomineralization. Participants in the intervention group reported notably lower pain perception, as measured by the Visual Analog Scale (VAS), FLACC scale, ball squeezing test, and physiological pain symptoms. Additionally, they experienced a faster onset and longer anesthesia duration than the control group.