Advancements in Preventive Strategies and Enamel Regeneration: Navigating the Complexities of Dental Care in the Age of Technology

Abstract

In our technology-driven world, rising dental injuries have prompted re-evaluation of treatment methods. Key focuses include preventing carious lesions through early detection and good oral hygiene. Precise diagnostic tools enable tailored treatments, such as fluoridation, sealing, pH-adjusting diets, resin infiltration, and ozone remineralization. Dental enamel is crucial for tooth function. Researchers aim to replicate its complex structure for biocompatible materials. Hydroxyapatite’s unique properties are vital for hard tissues like bones, enamel, and dentin. Enamel development involves ameloblasts in pre-eruptive and post-eruptive stages. Saliva aids post-eruptive maturation but can lead to bacterial adhesion and enamel demineralization. Preventing enamel demineralization hinges on ion transport and critical pH levels, while low calcium levels impact enamel cells. Dietary sugars interact with bacteria, causing demineralization, but saliva aids remineralization. Caries risk depends on factors like diet, oral hygiene, and tooth morphology. Personalized approaches like Caries Management by Risk Assessment (CAMBRA) for caries risk assessment (CRA) are crucial. Traditional enamel protection methods involve fluoride and dental sealants, but concerns exist about fluoride toxicity and bacterial resistance. Modern alternatives include resin infiltration for early caries, argon laser technique for lesion protection, and ozone therapy to combat decay, offering noninvasive options for enamel care.

1. Introduction

We find ourselves in an era characterized by rapid technological advancements, unlike any other time in history. However, despite this progress, we continue to grapple with an alarming increase in dental injuries across all age groups. This contemporary predicament raises questions about the effectiveness of our current treatment approaches and the validity of our problem-solving strategies.

Within the realm of medical science, carious lesions are officially recognized as a disease, aptly named carious disease. Consequently, it’s crucial to acknowledge that, unlike many other health conditions, carious lesions are preventable. To stave off the development of carious lesions, it becomes imperative to diligently assess the risk of tooth decay and identify demineralization lesions in their early stages. Furthermore, it is essential to formulate and implement the most efficient preventive measures.

To this day, the most renowned method for averting cavities remains fluoridation. Over time, this practice has persisted and is still applied through various means such as gels, varnishes, mouthwashes, and toothpaste formulations. A secondary preventive approach entails sealing fissures and gaps with sealing materials, including resins and ionomer-based cements.

However, in addition to these major preventive techniques, the maintenance of oral hygiene plays a pivotal role in ensuring the success of these methods. Moreover, the dietary habits of the individual can either bolster or undermine the effectiveness of the aforementioned therapies. Daily consumption of carbohydrates and sugars in various forms causes a decline in salivary pH levels, exposing tooth enamel to recurrent acid attacks, resulting in the development of demineralization lesions.

Hence, the effectiveness of any preventive strategy against carious lesions hinges on imparting health education regarding nutrition and oral hygiene to induce a transformation in patient behavior and lifestyle. This underscores the idea that dental issues are not contagious but rather stem from individual behaviors.

Consequently, the management of enamel quality should initiate with the identification and regulation of individual-level risk factors, followed by education on sound dietary choices and dental hygiene practices. Subsequently, non-invasive preventive enamel treatments can be considered.

Regarding these treatments, the approach must be distinctive. To select the most suitable therapy, accurate diagnosis by the dentist is essential. Various medical instruments, such as intraoral cameras, Diagnodent, VistaCam iX, or the office version of CLMS, facilitate this precise diagnosis.

Following a meticulous examination and diagnosis, the appropriate treatment can be determined, which may involve fluoridation, sealing, dietary adjustments to elevate salivary pH, infiltration using low-viscosity resins, or Ozone remineralization (O3T).

1.1 Enamel: understanding the structure and characteristics of dental enamel

The outermost layer of a tooth is composed of dental enamel, making it the hardest tissue in the human body. Conversely, the innermost part of the tooth is occupied by the dental pulp, a crucial component housing specialized cells, nerves, and blood vessels. The dental pulp, in conjunction with dentin, constitutes the pulpo-dental organ, playing a vital role in preserving the tooth’s vitality [1].

It directly enables and powers the mechanical processes of cutting, breaking, and grinding, making its mechanical characteristics highly impressive [2]. These attributes result from the flawless realization of the prismatic spatial microstructure of hydroxyapatite. Enamel’s exceptional mineralization as a cellular tissue is attributed to its composition, comprising 97% inorganic matter, 3% organic matter, and 1% water.

Over the past few years, experts in the dental materials and dental medicine field have been striving to replicate a biomimetic enamel-like structure possessing identical mechanical characteristics [3]. Innovative methods, including surfactant-assisted techniques, hydrogel systems, and high-temperature, high-pressure hydrothermal systems, have even been employed to endeavor the regeneration of hydroxyapatite (HA) crystals [3].

Replicating the in vitro biomechanical traits of enamel poses a challenge due to their intricate nature, stemming from the hierarchical organization of enamel prisms across multiple tiers. These prismatic frameworks are intricately interwoven and closely knit, comprising hydroxyapatite (HA) crystals aligned in parallel [4]. Research has indicated that dental synthetic materials designed to mimic enamel-like structures exhibit superior biocompatibility when compared to materials with randomly arranged structures [4]. As a result, it is imperative, in the pursuit of materials for promoting enamel remineralization, to faithfully replicate the prism structure found in dental enamel [5].

The distinctive microstructure of enamel extends perpendicularly from the enamel-dentin junction to the enamel surface [6], resulting in anisotropic mechanical properties [6]. Research has quantified enamel hardness through Young’s moduli measurements, revealing values in the range of 85–90 GPa parallel to the crystalline rod axis and 70–77 GPa perpendicular to it. The average hardness registers at approximately 4.79 GPa parallel to the enamel rods and 3.8 GPa perpendicular to them, with a hardness of approximately 0.7 ± 0.02 MPa*m^1/2 [5, 7].

1.2 Exploring the world of hydroxyapatite (Ca10(PO₄)₆·2(OH))

Hydroxyapatite is a fundamental component found not only in the hard tissues of the human body but also in various other structures. In the skeletal system, for instance, it constitutes 65% of its composition, playing a critical role in conferring rigidity and strength to bones. Additionally, HA holds a central position as the primary mineral component in both enamel and dentin [8].

Literature studies have indicated that in enamel, HA crystals typically range in size from 48 to 78 nm [8]. These crystals exhibit a hexagonal shape and collectively form rod-like structures within the enamel, in contrast to the flattened rods found in mature dentin, which measure approximately 60–70 nm in length [9].

The remarkable stability and low solubility of HA in nature can be attributed to its calcium-phosphorus ratio of 1:67 [9]. Over time, owing to its exceptional properties, the calcium-phosphorus system has garnered significant attention in medical research, finding applications in fields such as implantology, the skeletal system, and drug delivery systems [10].

1.3 Delving into enamel mineralization

Describing the intricacies of enamel development and maturation is a formidable task. This process, in terms of its duration, can be likened to the gestation of an embryo within the womb, but it unfolds over a considerably longer period than enamel amelogenesis [1]. Achieving full maturity in the crown formation of specific permanent teeth may even span up to 5 years [1]. Once maturity is attained, dental enamel comprises a substantial 95% of its weight in hydroxyapatite crystals [1].

A diverse assembly of specialized cells [11] contributes to the formation of enamel. Collaboration among these cells, both intercellular and with the surrounding tissues, is a noteworthy aspect of this process, involving transformative elements with distinct functions [11, 12, 13].

Among these cells, ameloblasts hold the utmost significance. These tall and columnar epithelial cells, characterized by structures like the “Tomes process” [14, 15], bear the responsibility for both mineralizing and shaping enamel [11].

Furthermore, the developmental islands play a pivotal role in facilitating proper enamel development. Enamel, being an acellular organ, lacks the capacity for remodeling once it undergoes mineralization [11]. Enamel development is a multifaceted process comprised of two distinct stages: the pre-eruptive and post-eruptive phases. In the initial stage, mineralization is orchestrated by pre-eruptive cells. Here, ameloblasts play a central role in directing the synthesis of matrix proteins and commencing the formation of enamel crystals [1].

The process of amelogenesis at this level unfolds in two developmental phases: secretory and maturation. In the secretory phase, ameloblasts initiate the release of matrix proteins from the enamel and commence their outward migration from the enamel organ [16, 17].

Within the secretory stage, four distinct cell layers are discernible: an inner layer of secretory ameloblasts, an intermediate zone comprising one or two layers of slender cells, the stellate reticulum layer, and an outer layer forming the enamel’s outer epithelium [18, 19]. The vascular network responsible for supplying essential nutrients during enamel development circulates and interacts with the outer epithelial layer of the enamel [18, 19].

Ameloblasts hold particular significance in this context as they synthesize four primary structural proteins and two proteases (metalloprotease 20—MMP20—and Kallikrein 4) that collectively contribute to the shaping and spatial organization of the initial hydroxyapatite (HA) [14, 15].

Among the four principal structural proteins, amelogenin takes precedence. It is the most abundantly secreted and plays a pivotal role in the growth and organization of the enamel structure, governing its morphology [20]. As an intrinsically disordered protein, amelogenin assumes a crucial role in controlling the polymorphism of calcium phosphate [21, 22].

The second enamel protein is ameloblastin. While its exact function remains to be fully elucidated, it is believed to be indispensable for enamel formation [1]. Enamelin, though present in the least quantity, is consistently found at all stages during enamel formation [1] and collaborates with amelogenin with a strong affinity for apatite crystals [23].

The fourth protein in this lineup is amelotin, and its exact role remains a mystery; what’s clear is that it is secreted by maturing ameloblasts. These proteins are distributed in various locations within the enamel, underscoring their vital role in enamel development [24]. In the inner enamel layer, these proteins are found in fragments, while in the outer layer, intact protein molecules are prevalent [24].

During the maturation stage, there’s a notable shift in ameloblast function, transitioning from a secretory role to one integral to the mineralization process [25]. They reconfigure themselves to assume the responsibility of calcium transport [1, 26], a function of paramount importance during the maturation phase. Any disruption in calcium transport can result in incomplete enamel mineralization [13].

Kallikrein 4 (kallikrein-related peptidase 4 (KLK4)) also plays a crucial role, as it breaks down proteins in the enamel matrix. This enzymatic degradation by KLK4 creates space for the expansion of mineral crystals [1]. Following this degradation, ameloblasts absorb the smaller fragments, which are subsequently broken down by lysosomes [1].

After a tooth’s eruption, it exhibits a layer of enamel covered by an enamel film [27]. In this post-eruptive maturation stage, the primary role shifts to saliva, as it facilitates the diffusion of calcium, phosphorus, potassium, magnesium, and fluoride ions to the enamel surface through interaction with saliva [27].

While the salivary film aids in the post-eruptive maturation stage of enamel, it can also potentially contribute to bacterial adhesion, potentially leading to enamel demineralization and the development of carious lesions [1, 27].

1.4 Understanding enamel demineralization

The formation of enamel crystallites is heavily influenced by ion transport, particularly involving Ca²⁺ and PO₄ 3 ions [5]. These ions are transported into the enamel matrix, leading to changes in the Ca/PO₄ ratio within the calcified enamel matrix [5].

In systems with cation-selective membranes, crystal growth results in an increased length/width ratio, a decreased width/thickness ratio, and elevated Ca²⁺ and PO₄ concentrations [13]. For instance, H⁺ ions play a crucial role in promoting crystal growth in the longitudinal direction [5].

When crystal growth occurs in membranes with lower pH values and reduced PO₄ concentrations, it tends to exhibit preferential growth in the c-axis direction [5].

Regarding enamel demineralization, the focus shifts to pH levels, as hydroxyapatite dissolution is enhanced with decreasing pH and the concentrations of Ca²⁺, PO₄³⁻ (and OH-) in the solution [28]. The degree of saturation concerning HA (DS HA) is defined as the ratio of the product of the ionic activity for HA to the solubility constant for HA, known as K-HA [28].

The crucial point at which pH decreases significantly is referred to as the “pH-critical” point, signifying the pH level at which a solution reaches saturation concerning a particular mineral. At this juncture, dental enamel exists in equilibrium, with neither dissolution nor precipitation of minerals occurring [28]. The critical pH for enamel is now widely accepted to be between 4.5 and 5.5 [29].

The degree of saturation (DS) of the plaque solution in relation to polycyclic aromatic hydrocarbons (PAH) plays a central role in influencing the rate of tooth demineralization [30]. This is predominantly determined by the pH value and the concentrations of calcium and hydrogen phosphate ions.

A sharp decline in pH is immediately associated with a reduction in DS, leading to a sudden escalation in the demineralization rate and subsequently an increase in calcium ion concentration [30].

When the pH falls below a critical threshold, the system becomes undersaturated, significantly heightening the potential for enamel demineralization [28].

Numerous studies are underway to explore the factors influencing the critical pH and enamel dissolution [31]. For instance, the concentrations of calcium and phosphate in saliva, particularly in contact with enamel, can impact the degree of saturation. According to mechanical in vitro studies, calcium exhibits a 20-fold higher efficacy than phosphate in inhibiting enamel dissolution [31, 32]. Consequently, variations in calcium concentrations exert a more pronounced effect than other minerals [31].

In vitro investigations reveal that calcium concentration can swiftly return to its initial level once the pH surpasses 5.5, effectively halting the demineralization process. It has been observed that, after the removal of glucose, it takes approximately 40 min for the pH to exceed the critical level and around 140 min to revert to the equilibrium value of 6.5 [30].

1.5 Exploring the role of calcium in dental enamel

The analysis of enamel’s macro-elemental composition reveals that it possesses the highest concentration of Ca2+ among all bioapatites, constituting approximately 37% of its mineral content by weight. Following closely behind, PO43- accounts for roughly 17% of the composition.

According to the literature, it has been suggested that the uptake of Ca2+ in ameloblasts is a passive process, facilitated by the extracellular to intracellular [Ca2+] gradient, with the cytosol having the lowest concentration of calcium. Subsequently, Ca2+ can be eliminated from the cytoplasm through the plasma membrane Ca2 + -ATPase (PMCA).

In a comparison of enamel’s calcium concentration with those of other tissues, it becomes evident that enamel contains over nine times more Ca2+ than muscle or liver. This substantial calcium presence in enamel, approximately 90% of it, is incorporated during the maturation process, and its entry into enamel cells is of a passive nature.

Transcellular Ca2+ transport emerges as a crucial process during amelogenesis. In this process, calcium enters polarized ameloblasts at the level of the blood supply and is subsequently released into the extracellular space of enamel, where it contributes to the formation of calcium hydroxyapatite.

Hypocalcemia has a significant impact on enamel cells, resulting in the formation of cysts within the ameloblast layer and the abnormal distribution of enamel proteins [33]. Researchers have observed that low dietary Ca2+ intake in nursing mothers is the cause of hypocalcemia [34], which, in turn, leads to undermineralization of enamel in their offspring.

Fortunately, this condition was successfully addressed through a 10-day calcium supplement administered to the mothers [34]. As a result of this research, the potential existence of a stock-operated Ca2+ entry system (SOCE) was acknowledged [35]. In this proposed system, calcium enters enamel cells and is subsequently transported to the endoplasmic reticulum (ER), followed by exocytosis to the apical pole, a phenomenon known as the “transcytosis hypothesis” [17, 35].

1.6 Risk factors for enamel health

Dental caries is regarded as a disease resulting from the simultaneous interplay of dietary sugars, inadequate oral hygiene, and the passage of time [31]. Bacteria present in dental plaque produce organic acids, causing a drop in the pH within the plaque, a process primarily driven by the metabolism of dietary carbohydrates [31].

When the pH within the plaque repeatedly falls below the “critical pH,” the enamel of the teeth initiates a process of demineralization, leading to the formation of an initial carious lesion [36]. This initial demineralization lesion is characterized by the loss of minerals from the subsurface enamel while maintaining a relatively intact surface layer [36].

Numerous studies on enamel emphasize the connection between sugar and carbohydrate consumption and the occurrence of tooth decay [37]. Any fermentable carbohydrate can be metabolized by specific oral bacteria, resulting in the production of organic acids (e.g., lactic, acetic, propionic) as byproducts [38], contributing to the formation of demineralization lesions.

The quantity of sugar in one’s diet plays a crucial role in assessing the risk of caries, with research findings suggesting that both the amount of sugar consumed and the frequency of sugar consumption between meals are risk factors [37].

While the acid-induced dissolution of enamel leads to structural loss and demineralization, it is worth noting that this process can be reversed over time through remineralization. This remineralization is facilitated by calcium and phosphate from saliva within the oral environment [39].

As the acid demineralization lesion continues to progress, the structural integrity of the enamel beneath the surface deteriorates, eventually resulting in the formation of a clinically detectable cavity [31]. Extensive research and discussion have been dedicated to the role of biofilm in the etiology of caries [40].

Dental plaque constitutes a biofilm comprised of billions of bacteria, the majority of which are exclusive to the oral cavity. One of the most renowned oral bacteria is Streptococcus mutans, which holds a prominent role as a major etiological factor in the development of carious lesions [31].

Streptococcus mutans excels in producing lactic acid when exposed to sugars and polysaccharides, facilitating its adhesion to enamel and the colonization of other pathogenic microorganisms [31]. Nevertheless, it’s important to note that the formation of carious enamel lesions is not solely attributed to the actions of a single microorganism. Acid production within dental plaque is a collective effort involving all acid-producing oral bacteria, collectively leading to a reduction in plaque pH [28, 31].

Below the “critical pH,” typically considered to be within the range of 4.5–5.5 [28], the dental surface (DS) experiences undersaturation with respect to hydroxyapatite (HA), leading to the dissolution of enamel. The pH of dental plaque is influenced by various factors, including plaque thickness, composition, location, permeability, and the concentration of fluoride, calcium, and phosphate [29].

Following the consumption of sugar and fermentable carbohydrates, the plaque’s pH rapidly plummets below pH 5.5, a process that occurs within minutes [41]. Research indicates that this acidic condition can persist for up to 20 min before gradually returning to a more neutral state. As the pH rises to values around 7 or higher, DS becomes supersaturated with respect to HA. In such conditions, enamel is capable of reclaiming mineral ions in a reparative remineralization process [41].

Repetitive exposure of enamel to low pH levels, without adequate time for repair, can shift the balance toward the formation of extensive carious lesions [41]. Salivary flow plays a crucial role in the host’s resistance to caries [42].

For instance, individuals with reduced or completely absent salivary flow are often susceptible to severe caries. Saliva serves as a protective buffer against acids, contributing significantly to the maintenance of tooth integrity [31]. Moreover, in terms of enamel remineralization, saliva provides essential ions, including fluoride. It also exhibits antibacterial and antifungal properties due to the presence of lysosomes [31].

Another contributing factor to caries is the tooth’s morphology and structural defects that may facilitate the accumulation of dental plaque. These factors are further influenced by the individual’s behavior in terms of oral hygiene practices and regular visits to the dentist [43].

With recurrent acid attacks on enamel, the consequence is the development of porosity within the enamel structure. If these porosities are not followed by a process of remineralization and improved oral hygiene practices, they can eventually merge, leading to the formation of carious cavities [44].

For an accurate diagnosis and treatment plan, it is essential for the dentist to determine whether a lesion is active, progressing rapidly, or has ceased its development. If the lesion is confined to the enamel layer, it can be halted and may even undergo a remineralization process [45].

In Europe, the initial demineralization lesion has been referred to as the “white spot” for several years. This lesion is described as a smooth, white, or opaque area without cavities, making it prone to plaque accumulation [45].

During this white spot stage, it is possible to arrest the progression of the lesion and eliminate the porosities. If dietary chromogens become trapped during the remineralization process, it can result in the appearance of a “brown stain” [31].

Although caries can develop on any surface of the tooth, nearly 90% of cases occur on the occlusal surfaces. Research conducted over time has shown that these areas do not respond as efficiently to remineralization compared to the smooth interdental or buccal surfaces [31].

2. Managing dental caries

Traditional patient assessment lacks a comprehensive form that tailors prevention and treatment methods to the individual patient’s caries risk. Instead, it heavily relies on invasive treatments [46].

Accurate caries risk assessment (CRA) and personalized patient management are essential for proper treatment. This approach involves a thorough analysis and control of risk factors, along with the development of customized treatment plans [46].

Several standards for classifying and managing caries currently exist. These systems were initially introduced in 2002, notably leading to the establishment of the International Caries Detection and Assessment System (ICDAS). In 2009, ICDAS underwent modifications with the addition of activity tests proposed by the International Caries Classification and Management System (ICCMS) [47]. Other systems for caries risk assessment include those by the American Dental Association (ADA), Caries Management by Risk Assessment (CAMBRA), and Cariogram [48]. Among these, the CAMBRA system stands out for its comprehensive coverage of caries risk factors [48].

2.1 Factors influencing caries risk

To ensure effective management of carious lesions and the selection of appropriate dental treatments, a comprehensive evaluation of the risk of dental caries is imperative. This assessment significantly influences the likelihood of future lesions and shapes the treatment plan [49]. To ascertain the accuracy of the prognosis and the impact of the chosen therapy, it is essential to reevaluate the post-treatment risk [48]. This step is a crucial component of enamel lesion management [48].

Among the various systems discussed in the previous section, the CAMBRA system stands out as the most extensive in terms of the number of risk factors associated with enamel damage, followed by ADA, Caries Risk Assessment Tool (CAT), and Cariogram [50]. Studies have indicated that the CAT and CAMBRA systems perform well for the 3-year-old age group but may not optimally predict enamel lesion prognosis [51]. Such an incomplete analysis could lead to an overestimation of caries risk in younger age groups, potentially resulting in unnecessary treatments [49].

The CAMBRA protocol is regarded as the most detailed and comprehensive approach. Within this protocol, a patient’s profile is meticulously examined by evaluating risk factors such as acidogenic bacteria, fermentable carbohydrates, and low salivary flow, as well as protective factors like fluoride and antibacterial therapies [46]. Following this thorough analysis, the patient is categorized into a specific caries risk level. Based on this framework, a personalized treatment plan is devised, which may include restorative treatments, preventive therapy, or a combination of both. Treatment options may involve fluoride application, a chlorhexidine mouthwash, dental sealants, and salivary enhancers [46].

The protocol equips practitioners with all the necessary instruments for its implementation, including a questionnaire designed to identify risk factors, risk indicators, and protective factors [46]. Naturally, when employing any protocol, all patient data are taken into consideration.

Within the CAMBRA system, risk factors for enamel damage are categorized as follows:

1. CRA – the probability of the patient developing new carious lesions.

2. Preventive factors – encompassing health education and preventive therapy that aid in lesion prevention or remineralization.

3. Risk factors – factors linked to the patient’s dietary and nutritional choices contributing to lesion development.

4. Caries indicators – derived from clinical examinations.

5. Carious lesion – distinguishing between cavitated and non-cavitated lesions [52].

The control of dental caries involves the application of protective factors and the reduction of pathological risk factors [52, 53]. Managing carious lesions is most effectively undertaken through a precise assessment of caries risk (CRA) and the acquisition of comprehensive information about the patient’s specific risk factors.

The development of an efficient strategy to foster healthy habits among patients must also address the modification of their behavior concerning oral hygiene and periodic oral evaluations [54]. Conducting a caries risk assessment (CRA) for each individual patient is indispensable as the foundation for caries management across all age groups [52].

2.2 Managing caries risk assessment for individuals aged 6 and above

For the comprehensive evaluation of caries risk assessment (CRA) in patients aged 6 and older, the CAMBRA system offers the most precise guidelines:

1. Thoroughly examine the patient’s dental and medical history.

2. Assess preventive measures and interventions.

3. Conduct a clinical examination to detect early enamel lesions and prevent their progression.

4. Categorize the caries risk into levels: low, moderate, high, or extreme.

5. Develop an individualized treatment plan that includes preventive or restorative measures, based on the caries risk classification in point f.

6. Implement chemical therapies, such as fluoride or other relevant substances, tailored to the detected risk factors.

7. Apply minimally invasive enamel procedures to deter enamel degradation.

8. Schedule periodic reassessments.

9. Modify the treatment plan as needed after the reassessment [52].

2.2.1 Enhancing protective factors

Protective factors encompass environmental, biological, or chemical elements that play a role in preventing enamel damage or facilitating its remineralization [55].

One of the most influential biological factors affecting caries risk assessment (CRA) is the patient’s living environment, which includes factors such as the fluoridation of the water supply in their region or their engagement in activities like travel, work, or education in areas with similar conditions [56]. This consideration is of paramount importance because residing in such areas or using fluoride toothpaste in combination with fluoride-based mouthwash, or recently receiving topical fluoride applications, can result in an excessive influx of fluoride into the body. This excess has the potential to transform a protective factor into a potentially harmful, toxic element [56].

Regarding chemical preventive measures, the regular use of a 0.12% chlorhexidine (CHX)-based mouthwash proves beneficial on a monthly basis. Caution is warranted in this regard since overconsumption of CHX can lead to unsightly brown stains on the enamel surface [55]. The selection of treatment is contingent upon the patient’s CRA level and, notably, their age [55].

2.2.2 Factors posing risk

The foremost risk factors include:

1. Daily consumption of carbohydrates, particularly snacks.

2. General health conditions necessitating medications that induce hyposalivation.

3. Substance abuse.

4. Inadequate oral hygiene practices.

5. Confirmed salivary dysfunction or hyposalivation.

6. Significant occlusal irregularities.

7. Extensive gingival recession with dental root exposure.

8. Use of dental appliances [1].

2.2.3 Indicators of disease

The dentist should clinically monitor various factors, including whether carious lesions have penetrated into the dentin, whether there are incipient demineralization lesions on intact enamel surfaces, and whether new patients within the system have received dental fillings in the past year [52].

Employing a caries risk assessment (CRA) framework facilitates the identification and categorization of patients into specific risk groups. This simplifies the dentist’s oversight of the treatment protocol and the development of an effective risk factor management plan to prevent carious lesions. Additionally, it empowers the patient to gain insight into adjusting their lifestyle, especially concerning diet, nutrition, and oral hygiene, thereby influencing the progression of these lesions [52].

3. Utilizing nanotechnology for enhancing mineralization in dental tissues

The utilization of nanotechnology within the field of dentistry has unveiled a wealth of potential, giving rise to a novel area of research. Nanotechnology’s versatile applications in dentistry encompass preventing biofilm formation, regulating the demineralization-remineralization equilibrium, combating caries [57], aiding in caries treatment, and even fabricating materials for dental implants [1].

To achieve these outcomes, calcium phosphate nanoparticles have been harnessed, displaying their ability to impede demineralization and enhance remineralization through the controlled release of calcium and phosphate ions [57].

Nanomaterials play a pivotal role in diminishing biofilm buildup, inhibiting the demineralization process, and can also be employed to counter cariogenic bacteria [1]. Substances like silver nanoparticles (Nag) and quaternary ammonium methacrylate (QAM) exhibit robust antimicrobial properties and exceptional durability, making their integration into dental materials exceptionally advantageous for enhancing antibacterial capabilities and promoting enamel remineralization [57].

Research has explored nanoparticles derived from highly soluble calcium phosphate phases, including monocalcium phosphate monohydrate, dicalcium phosphates, or amorphous calcium phosphates (ACPs), which facilitate the release of calcium and phosphate in carious lesions to promote remineralization [1, 57].

Furthermore, studies have revealed that a combination of glycine-guided hydroxyapatite and amorphous calcium phosphate (ACP) nanoparticles effectively remineralizes enamel [1, 57].

3.1 Biomimetic enamel mineralization

Biomineralization is a complex process that enables living organisms to accumulate inorganic ions through the involvement of protein molecules. Understanding this intricate process is vital, as it provides valuable insights into the formation of hard tissues, including bones and teeth [57].

The concept of biomimetic mineralization, which emulates the natural mineralization mechanisms of teeth, holds promise as an excellent alternative for restorative therapies when comprehended and applied [58]. Dental caries, a prevalent oral cavity ailment worldwide, arises from an imbalance between the remineralization and demineralization phases of dental hard tissue [58, 59].

Numerous remineralization approaches, such as fluoride, surfactants, electrolyte deposition, hydrothermal methods, and hydrogen peroxide, have been introduced to address initial enamel caries restoration and inhibit further demineralization [58, 59].

Tooth biomineralization encompasses both enamel and dentin mineralization. Dentin mineralization closely resembles bone mineralization, as both rely on collagen-based mineralization. In contrast, enamel lacks collagen, with amelogenin playing a pivotal role in mineralization [1].

Enamel, being an acellular tissue, presents a significant challenge for self-regeneration. Currently, the control of hydroxyapatite (HA) assembly, the fundamental component of enamel, remains undiscovered [50]. Consequently, numerous recent studies aim at biomimetic mineralization to replicate the enamel growth process [60].

To date, various typical methods for biomimetic remineralization have emerged, including ACP-induced mineralization, ion flow-induced mineralization, protein-induced mineralization, and in situ mineralization [60].

4. Conventional and contemporary approaches to preventing and assessing enamel quality decline

4.1 Traditional approaches to enamel examination

4.1.1 Initial evaluation

The primary objective of the examination is to visually identify alterations in enamel color and translucency, as well as changes in the enamel structure. An initial, tooth-by-tooth inspection on wet surfaces can reveal the presence of cavities, white or brown spots, and also allow for an assessment of caries activity. It is crucial, at this stage, to inspect for bacterial accumulation and signs of periodontal pathology at suspected sites.

The role of hygiene in ensuring diagnostic accuracy cannot be overstated, encompassing both direct visual assessment and the use of supplementary diagnostic methods. Utilizing magnifying loupes significantly enhances the initial detection rate of carious lesions.

Changes in color and translucency provide valuable insights into the demineralization status of the surface and subsurface areas, especially when compared to adjacent healthy regions. [61]

4.1.2 Radiographic evaluation

Bitewing radiographs are the preferred technique for the early identification of carious lesions, particularly on proximal surfaces. When compared to a simple visual examination, radiographic assessments typically uncover approximately twice as many proximal lesions that extend into the dentin. Radiographs also provide the ability to estimate the depth of these carious lesions.

For the permanent dentition, it is advisable to utilize two bitewing radiographs, allowing for direct and tangential coverage of all proximal surfaces within the molar-premolar segment. It is essential to note, however, that radiography cannot detect demineralization lesions.

4.2 Contemporary approaches to enamel examination

4.2.1 Digital scanned images

Traditional intraoral cameras offer the capability for immediate image viewing and digital image storage. While these images are valuable for patient education on oral hygiene, they often lack the necessary quality for accurate diagnosis of carious lesions.

Chemiluminescent intraoral scanners, on the other hand, provide precise measurements of mineral loss in hard tooth structure. They rely on the absorption of fluorescent chemicals released by microorganisms in carious lesions on tooth enamel when illuminated by a diode laser with varying wavelengths [62].

In contrast, an intraoral photoluminescence camera emits visible blue light at different wavelengths to capture and encode images of teeth that exhibit fluorescence [63]. Notably, red porphyrin emits fluorescence during the early stages of carious lesions. The quantitative light-induced fluorescence method (QLF) stimulates yellow luminescence in a wavelength range above 520 nm using a 405-nm wavelength light source. The potential for early diagnosis hinges on the intensity of a tooth’s natural fluorescence, which is influenced by the presence of carious lesions [64].

Optical coherence tomography (OCT) represents an even more non-invasive imaging technique with enhanced accuracy and resolution. This method is employed across various medical fields, including optometry, dental services, dermatology, and internal medicine [65].

Optical coherence tomography, in particular, stands out for its ability to detect incredibly small demineralized areas on both the surface and within the enamel, mitigating the limitations associated with other optical methods used in assessing tooth decay [66].

Extensive research in dental practice has solidified OCT’s capability to produce clear images of dental tissue, offering a promising avenue for the precise measurement of early enamel carious lesions [67].

The analysis using OCT reveals mineral loss and accurately gauges the extent of demineralization within the lesion. It also allows for a more objective and precise assessment of the intensity of initial enamel carious lesions, as the quantifiable index obtained through OCT correlates significantly with enamel demineralization [65].

Additionally, various techniques, such as atomic force microscopy (AFM), microradiography, scanning electron microscopy (SEM), surface profilometry, and CLMS [61], can be employed to quantify micromorphological changes in dental enamel resulting from erosion or abrasion [61].

For over three decades, confocal laser scanning microscopy (CLSM) has been a valuable tool in dentistry, facilitating the analysis of dental materials, their properties, dental enamel, including erosion and demineralization, and even enabling the three-dimensional (3D) examination of dental plaque formation and accumulation. Furthermore, CLSM plays a vital role in the evaluation of dental implants, which have seen a surge in popularity in recent years [2].

Continuing to demonstrate its significance in dentistry, CLSM provides 3D visualizations of tooth structure, tooth surfaces, materials, and the colonization of bacteria, aiding in the exploration of tooth enamel and beyond [2].

The confocal microscope is employed to acquire high-resolution optical images, completely eliminating interference from other light wavelengths within the section. The digital nature of confocal microscope images allows for extensive post-processing and a remarkable enhancement in resolution compared to conventional microscopes [2].

In this process, the primary light source emits a point-like beam that is reflected by mirrors. Simultaneously, fluorescence, with its longer wavelength, passes through the objective lens and is captured. The fluorescence is then directed to the photodetector through the confocal objective, while fluorescence from other planes within the specimen is effectively blocked [2].

One of the standout features of CLSM is its ability to eliminate extraneous data outside the focal plane, resulting in exceptional 3D imaging performance. Unlike conventional microscopes, CLSM experiences few limitations in terms of imaging, with the main restrictions being associated with magnification and the diameter of the focusing objective [2].

Confocal laser scanning microscopy (CLSM) produces a focused beam while effectively filtering out unrelated light, allowing it to penetrate deep into the dental tissue under examination, resulting in the creation of high-quality 3D images. Both the illumination and detection are precisely directed to the same focal point, which is systematically moved across the sample’s surface to collect the image data [68].

For in-depth tissue analysis in medical research, CLSM proves indispensable as it meets the specific requirements. However, it’s worth noting that, to perform this analysis effectively, the sample thickness must surpass the axial resolution of the objective lens [68].

4.3 Conventional approaches to enamel demineralization prevention

4.3.1 Fluoridation: enhancing dental health

The outermost enamel layer can exhibit fluoride concentrations exceeding 1000 ppm, while the underlying layer typically ranges from 20 to 100 ppm (81). Nevertheless, even these concentrations fail to significantly reduce the acid solubility of artificial carbonate apatite [15].

Fluoride has been recognized as a potent agent for preventing dental caries, and the most prevalent method of prevention involves daily brushing with fluoridated toothpaste. Nonetheless, concerns arise with fluoride applications, particularly regarding potential toxicity at high doses [69].

Widespread fluoride availability has led to the emergence of fluoride-resistant strains of S. mutans and other oral bacterial species, diminishing the efficacy of fluoride in acid production [69].

Fluoride levels within dental biofilm and saliva have the potential to aid in enamel remineralization and inhibit demineralization [70]. Fluoride is released when the flow rate is low due to acid formation, and it can either facilitate tooth structure remineralization or impact microbial activity [70].

Professional fluoride varnish treatments have also proven effective in reducing the risk of recurrent dental caries, provided they are administered correctly and in accordance with post-lesion risk assessments [70].

4.3.2 Sealing the pits and fissures: an overview

Pit and fissure sealing has long been employed as a preventive and management strategy for dental caries in both primary and permanent teeth. The application of pit and fissure sealants on molars and premolars has proven effective in averting occlusal surface damage [70].

In line with the recommendations of the American Academy of Pediatric Dentistry (AAPD), sealants are advised exclusively for sound occlusal surfaces on permanent molars and unaffected occlusal carious lesions [71].

Although various types of sealants are available in the market, their precise effectiveness remains challenging to ascertain due to a lack of substantial evidence [72].

The sealing material must possess antibacterial properties to hinder the proliferation of microorganisms in dental plaque and safeguard healthy tissues. Furthermore, it should exhibit the appropriate consistency to readily penetrate the grooves and fissures of molars and premolars throughout their entire depth and length [73].

According to the literature, the essential characteristics of the sealing material encompass:

• Biocompatibility.

• Ease of handling and processing.

• High penetration capability and low viscosity.

• Resistance to abrasion.

• Minimal post-polymerization shrinkage.

• Esthetic appeal [73].

Initially, dental sealants were crafted using glass-ionomer cements; however, their effectiveness diminished over time. Subsequently, resin-based sealants emerged as a more enduring and widely adopted alternative. These resin-based materials are available in various forms, including opaque, translucent, and a range of colors, catering to a diverse patient base, including children [74].

Various resin-based sealant materials gradually release fluoride, thereby enhancing their dental preventive capabilities. For improved adhesion, it is essential to etch these materials with orthophosphoric acid before applying them to the enamel surface [74].

Due to the proximity of the enamel adjacent to the sealed area during the etching process, experts advise applying a fluoride layer once the sealing procedure is completed. This additional fluoride layer contributes to the remineralization of enamel affected by the acid etching process [74].

The primary purpose of the sealant is to establish a protective barrier between the most susceptible region to caries and the oral environment. It’s crucial to note that the long-term effectiveness of dental sealants in preventing caries is contingent on their retention over time [75].

In general, it is recommended to apply sealants to the pits and fissures of primary molars at ages 3–4, first permanent molars at ages 6–8, and the remaining two permanent molars and premolars at ages 10–12.

A number of dentists have ceased the use of dental sealants as a treatment method, likely due to a lack of awareness concerning their effectiveness and a limited understanding of the criteria for sealant application. The proficiency and expertise in executing this medical procedure are pivotal, making the difference between a successful sealing procedure and an ineffective one [76].

For long-term effectiveness, strict adherence to the steps for preparing the dental sealant is imperative. The actual sealing of the tooth represents a critical stage. Proper isolation serves as the cornerstone for the success of any dental treatment, whether it involves sealing, composite filling, or endodontic procedures.

The indications for sealing pits and fissures encompass:

• Pits and fissures featuring intact enamel.

• Minimal opacities are also suitable for sealing.

• Deep and retentive pit and fissure morphology.

• Absence of clinical or radiographic evidence of caries.

• The tooth should have erupted recently, within the past 4 years,

• Availability of adequate isolation [77].

Contradictions for sealing pits and fissures include:

Large pits and fissures due to the potential for self-cleaning and clinical signs of interproximal caries.

• Radiographic evidence of caries.

• The presence of multiple restorations.

• Absence of any other preventive treatment.

• Partial tooth eruption.

• Inadequate isolation [77].

To ensure the enduring effectiveness of the sealing material, periodic evaluation is essential. During these assessments, the dentist should not only examine the tooth surface through tactile and visual means but also employ modern diagnostic devices like VistaCam or Diagnodent for precise evaluations [77].

The assessment should focus on the seal’s integrity and its adaptation to the neighboring enamel. If there is material loss, the appearance of marginal staining, or marginal dehiscence, the dental sealant should be replaced [77].

The necessity for sealant application should be reviewed during routine preventive care sessions [70, 78].

The recommendations for using dental sealants as a preventive measure have been highly beneficial, as years of expert studies have demonstrated the method’s effectiveness in preventing and halting the development of carious lesions. By filling the grooves and fissures with sealant material, children can better maintain the cleanliness of the occlusal surfaces of their posterior teeth, which are prone to retention loss [79].

However, as every study has concluded, the long-term effectiveness relies on biannual follow-ups and, if necessary, reapplication [79].

In general, it is recommended to seal the pits and fissures of primary molars at ages 3–4, first permanent molars at ages 6–8, and the remaining two permanent molars and premolars at ages 10–12.

The need for sealant application should be periodically reassessed during routine preventive care sessions [70, 78].

4.4 Contemporary approaches to preventing enamel demineralization

4.4.1 Infiltration with low-resin viscosity

Icon, developed by DMG-Hamburg, represents a groundbreaking dental material characterized by its low viscosity. This innovative resin is ideally suited for the microinvasive treatment of white spot lesions, demineralization, and incipient carious lesions, encompassing occlusal, buccal, and interproximal surfaces [77].

Low-resin viscosity therapy occupies an intermediate position between preventive and restorative treatments [80]. By infiltrating these lesions with resin, which acts to occlude the enamel porosities that serve as conduits for acids and minerals, caries progression can be halted [80].

Furthermore, low-viscosity infiltrating resin can also be employed to address the appearance of white spot lesions that arise post-orthodontic treatment. Research has shown that this material boasts long-term durability and produces stunning esthetic outcomes. The opacity of white spot lesions diminishes almost instantly during treatment, restoring the enamel to its natural appearance [81].

In contrast to methods such as fluoride therapy or calcium casein pastes, resin-filled microporosities do not evaporate, delivering immediate esthetic enhancements [80, 82].

In cases involving early carious lesions that are beyond the scope of fluoride therapy, resin infiltration has demonstrated its effectiveness in inhibiting the progression of caries [80, 82].

4.4.2 Laser technology as a preventive approach

Numerous in vitro and preliminary in vivo experiments have revealed the protective potential of argon laser therapy against the onset and progression of enamel carious lesions [83].

The utilization of laser technology in dental medicine represents a revolutionary approach with a wide range of applications. It not only facilitates early carious lesion detection but also offers treatment options. Additionally, oral surgery and periodontology can benefit significantly from laser technology [83].

In the realm of pediatric dentistry, laser technology holds particular appeal due to its ability to provide a relaxed, non-invasive experience for children. Moreover, it proves valuable in pediatric endodontic procedures, such as pulpotomies and pulp hemostasis [83].

Combining argon laser irradiation with topical acidulated phosphate fluoride treatment results in the creation of a protective barrier against carious lesions and a significant reduction in lesion depth [84]. This laser effectively enhances the resistance of both sound enamel and demineralized lesions to caries [83].

The laser prevents the formation of a smear layer, thereby enhancing the adhesive strength of composites. Additionally, it can be employed for laser enameloplasty before sealant placement, further bolstering caries resistance and potentially eliminating the need for traditional etching [83].

The laser also strengthens the bond between resin-based materials and the enamel surface. Using a laser before applying sealing materials proves highly advantageous, as it may obviate the need for enamel etching [83].

4.4.3 Utilizing ozone therapy (O3T)

Ozone (O3) is a highly reactive compound consisting of three oxygen atoms, acting as both an oxidant and oxidizer [85]. Ozone therapy, as a non-invasive alternative for addressing tooth decay, offers distinctive advantages when compared to other available treatments. The primary objective of ozone therapy for carious lesions is to diminish the causative microbiota, reduce risk factors, arrest the caries process, and promote remineralization. Enamel remains vulnerable throughout one’s life, continually exposed to the oral environment. The acidic conditions created by bacteria, dietary factors, and beverages contribute to dental issues, affecting four out of five primary teeth in children and over half of permanent teeth in adults [11, 86]. Given that enamel is categorized as acellular tissue, it lacks the capacity for self-regeneration or reshaping, making the lesions irreversible and necessitating restoration with artificial materials.

A key challenge in non-invasive approaches to prevent carious lesions and promote enamel remineralization lies in controlling dental plaque. Ozone can remove proteins from carious lesions, facilitating the diffusion of calcium and phosphate ions through the lesions, thereby promoting remineralization [87]. Moreover, ozone offers environmental benefits, as it rapidly degrades and exhibits low cytotoxicity when in contact with organic compounds. These characteristics suggest a promising future for ozone in restorative and preventive dentistry [87].

Due to its potent oxidation capabilities, ozone can oxidize bacterial cell walls, leading to lysis, and can transform the pyruvic acid produced by bacteria into acetic acid and carbon dioxide, thereby halting or reversing the progression of caries. While the antimicrobial properties of ozone are well documented [85, 88, 89, 90, 91], its potential for remineralization by enhancing dentin tubule permeability is less explored. As a demineralizing agent, ozone appears to enhance the diffusion of salivary ions to the degraded dentin surface, facilitating remineralization [85, 92, 93, 94]. In this context, ozone can counteract the acidic proteins produced by cariogenic bacteria, which are responsible for osmotic stimulation, leading to fluid movement within dentin tubules and resulting in hypersensitivity [93, 94, 95].

Considering the various therapeutic effects of ozone outlined above, it is important to note that these effects arise from diverse mechanisms of action, including:

• Antimicrobial properties: Ozone acts as an antimicrobial agent by destroying viral capsids and disrupting the reproductive cycle through peroxidation.

• Immune modulation and antioxidant activity: Ozone serves as an immune modulator and antioxidant agent by stimulating immunoglobulin synthesis, maintaining cell redox balance, and increasing cellular levels of glutathione (GSH) peroxidase.

• Anti-hypoxic effect: Ozone enhances oxygen saturation in hemoglobin, thereby counteracting hypoxia.

• Anti-inflammatory action: Ozone’s anti-inflammatory impact is achieved by influencing the synthesis of interleukins, prostaglandins, and leukotrienes.

• Bioenergetics enhancement: Ozone activates protein synthesis and boosts cellular metabolism, contributing to its bioenergetic effect.

• Detoxification: Ozone promotes cellular aerobic processes, including the Krebs cycle, glycolysis, and fatty acid oxidation, thus facilitating detoxification.

• Biosynthetic function: Ozone enhances the metabolism of carbohydrates, proteins, and lipids, impacting biosynthetic processes [96].

Ozone can be applied to the tooth’s surface using either gas or water delivery methods. It possesses robust bio-oxidative properties, is highly bactericidal, and has found utility in dentistry for the treatment of dental caries in both enamel and dentin, as well as for addressing root caries and dental hypersensitivity [92].

5. Conclusions

In conclusion, the current era, marked by rapid technological advancements, has paradoxically witnessed a concerning surge in dental injuries across all age groups. The persistence of such issues prompts a critical evaluation of our existing treatment methodologies and problem-solving approaches. While carious lesions are officially recognized as a preventable disease, the ongoing escalation of dental problems necessitates a reexamination of preventive strategies. Fluoridation, sealing techniques, and maintenance of oral hygiene are conventional methods that have endured the test of time. However, the evolving landscape introduces innovative approaches like biomimetic enamel mineralization, offering promising alternatives for restorative therapies. The integration of digital scanned images, chemiluminescent intraoral scanners, intraoral photoluminescence cameras, and optical coherence tomography in enamel examination represents a significant stride toward non-invasive and accurate diagnostics. The multifaceted nature of enamel demineralization prevention requires a holistic approach, encompassing dietary adjustments, individual risk factor management, and education to induce transformative changes in patient behavior. In this ever-evolving landscape, the identification and regulation of individual-level risk factors, coupled with advancements in biomimetic mineralization and cutting-edge diagnostic technologies, pave the way for a comprehensive and effective paradigm in the prevention and management of enamel demineralization.

Conflict of interest

The authors declare no conflict of interest.