3.1 The Restorative Effect of Metal Prefabricated Crowns and all Ceramic Crowns for Deciduous Teeth
In recent years, pulpotomy has been widely accepted and recognized as a common method of pulp preservation for primary caries, and its postoperative effects have been widely accepted and recognized. By preserving some of the pulp, the health of dental tissue is maintained, and normal replacement of primary and permanent teeth is maintained [7, 8]. Previous studies have shown [9–11] that using pre crown restorations can improve the success rate of pulp treatment in affected teeth compared to traditional restorative materials. Traditional restorative materials such as resin and glass ionomer cement, although commonly used in dental restoration, have certain limitations in clinical efficacy. Traditional restoration materials have poor wear resistance and are prone to wear over time. However, the patient's own saliva secretion is vigorous, making it difficult to ensure the moisture barrier effect, which can easily lead to micro leakage at the edge of the filling material in the later stage, thereby affecting the restore effect. In addition, external factors such as poor treatment compliance in pediatric patients may lead to the inability of traditional filling restoration to achieve ideal results [12].
Scholars have confirmed that PMC is superior to resin based composite materials in restoring patient occlusal function and restoring effects, with more ideal results [13] and simpler operation methods [14]. It does not require a lot of time to adjust, providing a higher quality solution for children with primary molars caries and root canal treatment restoration [15]. PMC also has a longer clinical service life compared to other filling materials, especially suitable for single deciduous teeth with caries on more than two tooth surfaces [16]. Therefore, scholars recommend using PMC to restoration primary molars in children prone to caries [17]. In recent years, the application of ZC in clinical practice has not only met the aesthetic requirements of children and parents, but also achieved satisfactory results in the restoration of dental caries [18, 19].
The FDI clinical evaluation criteria for restorations are superior in sensitivity and accuracy compared to the modified USPHS (United States Public Health Service) criteria [20]. Therefore, this study selected the clinical evaluation criteria for FDI restorations proposed by Hickel et al. [5] in 2007, and selected some evaluation indicators to analyze the lifespan of the restorations. The value range of each scoring criterion is between 1 and 5 points. When the score range of the restoration is between 1 and 3 points, the success rate is used for evaluation; When scoring 4–5 points, evaluate using failure rate; When scoring 1–4 points, the retention rate is used for evaluation. Researchers can selectively use FDI restorative evaluation criteria based on the actual score range for restorative life analysis and comparison, without blindly pursuing the use of all indicators [21]. According to the research objectives, the most commonly used and simple evaluation indicators were selected for this study: surface and edge coloring of the restoration, aesthetic anatomical morphology, fracture and fixation, adjacent anatomical morphology, imaging examination, postoperative sensitivity and pulp vitality, secondary caries, acid erosion and wear, and periodontal health.
This study focuses on children with first molar caries and conducts follow-up examinations at different time intervals after restoration. After 3 months of completion of restoration, the PMC group and ZC group were respectively evaluated for FDI restorative performance evaluation indicators. The results showed that the overall restoration effect of the two groups was similar, and the restore treatment effect was satisfactory. Consistent with the research results of Mathew et al. [22]. The probability of detachment or fracture in the ZC group after restoration is lower. Most studies have shown that the success rate of ZC restoration is as high as 95–100% during 12–36 months of follow-up observation after deciduous tooth restoration [23, 24]. In this study, only one case in the ZC group experienced partial crown fracture one year after restoration. Through case analysis, it may be related to insufficient space during tooth preparation, inverted abutments, excessively sharp edges of abutments, and poor daily usage habits of the patient [17]. Murad and other scholars believe that the complete retention of ZC mainly depends on pulp treatment strategies and restorative physician techniques, rather than the physical and chemical properties of the crown [25]. PMC has advantages in retention rate and crown integrity, which may be related to the following factors: (1) PMC has good ductility and retention, can bear large stress, enhance tooth compression and fracture resistance, and prevent crown collapse [26]; (2) Only a small amount of tooth preparation is required during the dental preparation process [27]; (3) PMC has good elasticity, which can reduce the occurrence of edge fracture, allowing the complete transition of the deciduous dentition to the mixed dentition, and providing normal physiological gaps for the permanent dentition [28].
3.2 The Impact of Metal Prefabricated Crowns and all Ceramic Crowns on Periodontal Health in Deciduous Teeth
GI, BI, and PLI are all important indicators for evaluating periodontal health [29, 30]. Previous clinical studies have mainly focused on the effectiveness of PMC in the restoration of dental caries in children. Based on the observation of the PMC group restoration, this study added the restoration effect of the ZC group and the impact of two types of pre formed crowns on the periodontal health of children with dental caries. The results showed that the PMC group showed varying degrees of improvement in GI, BI, and PLI compared to the ZC group, indicating that PMC restoration has a certain impact on the periodontal health of children with dental caries. This may be due to the PMC neck edge not tightly fitting, the crown edge extending too long, and food residue retention, which leads to an increase in local irritant factors such as plaque, soft plaque, and tartar, resulting in an increased risk of gingivitis [33]. Meanwhile, the periodontal health after PMC restoration is also affected by various factors such as unhealthy dietary habits and sugar intake frequency.
Compared with PMC, ZC can prevent Streptococcus mutans from adhering to its surface, reduce plaque accumulation on the surface of the crown, and its good biocompatibility can also reduce irritation to the surrounding gums, reducing plaque deposition [23]. In addition, the surface of ZC crowns is smooth, which can prevent the adhesion of microorganisms and dental plaque [34], avoiding the growth of biofilm on the uneven surface caused by PMC trimming, curling, and cutting, thereby increasing the risk of gingivitis.
This study also found a certain negative correlation between the periodontal health status of the PMC group after restoration and age. The older the age, the lower the periodontal health-related indicators, indicating a decrease in the incidence of gingivitis. This may be due to the increased oral hygiene behavior and health awareness among children as they age. Therefore, for children receiving PMC restoration treatment, it is necessary to strengthen oral hygiene education, urge them to cultivate good oral hygiene habits, effectively control plaque formation, and achieve the goal of maintaining oral health. However, there was no significant correlation between the periodontal health status and age in the ZC group after restoration, which may be related to the generally low periodontal health indicators in the ZC group and the good biocompatibility of all ceramic crowns.
3.3 Limitations
This study collected case data using a retrospective cohort study method, but lacked data collection on baseline clinical indicators of pediatric patients; After strict screening of case standards, the number of cases included is relatively small, which may cause some deviation in the statistical analysis of clinical indicators. In the future, further expansion of the sample size and the use of randomized controlled trials are needed to deepen the research content and extend the clinical observation period for further analysis.