Requirements of Back to Back Crowns in Children Aged 2 to 6 Years in Mandibular Arch-An Observational Study

Ivan Obadiah1, Deepa Gurunathan*2, Vignesh Ravindran2 1Saveetha Dental college and hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai 600077, Tamil Nadu, India 2Department of Pediatric and Preventive Dentistry, Saveetha Dental college and hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai 600077, Tamil Nadu, India


INTRODUCTION
Managing dental caries successfully in a pediatric population involves many challenges and requires ef icient skills and knowledge in framing a treatment plan with good prognosis (Ludwig et al., 2014). Early childhood caries (ECC) is a serious community health problem in many countries across the world, including both developing and industrialized countries (Uribe, 2009). Its consequences are capable of affecting the quality of life of the children affected and also their parents (Sharna et al., 2019). After intervening the symptoms of the patient such as pain, swelling or sensitivity by pulp therapy, restorations etc., it is important to preserve the treatment done and also it is mandatory to regain the function of the treated tooth. Full coverage restorations serve best in such situations in providing a better prognosis (Miller and Feinberg, 1962) Preformed metal crowns also commonly referred to as stainless steel crowns were brought up to pediatric dentistry by Humphrey in 1950 (Nash, 1939). It has been noticed that they are delivering superior prognosis than that of large multi-surface amalgam restorations and also proven to have longer clinical lifespan than two or three surface amalgam restorations (Dawson et al., 1981). Stainless steel crowns have a strong advantage or relative lack of sensitivity to oral conditions during placement and cementation. In an uncooperative crying child it is often possible to place a well-itting crown without compromising longevity or quality of the restoration. Therefore, inability to ef iciently control saliva is an indicator for choosing the stainless steel crown as the restoration of choice. However its main disadvantage is the metallic appearance. In children with excessive carious lesions that have widely distributed throughout their dentition, it is commonly observed that both the primary molars i.e irst and second primary molars in any quadrant of the primary dentition is carious and requires a full coverage restoration to regain its function. (Kindelan et al., 2008) Stainless steel crowns are indicated for various cases like following pulp therapy, in case of proximal carious lesions and also as a full-coverage abutment for space maintainers. In cases where two adjacent teeth require stainless steel crowns, speci ic adaptations were required to be done in the crowns to it them. Among the vast wide range of pediatric dental patients, speci ic requirements for back to back stainless steel crowns are not studied and analysed. This study is speci ically designed to enumerate the usage of back to back stainless steel crowns in the mandibular arch of children aged 2 to 6 years and to determine the requirements of the same.

MATERIALS AND METHODS
This study was conducted in a university setting among the pediatric dental patients visiting the department of pediatric and preventive dentistry in Saveetha Dental College and Hospital. The ethical approval was given by the institutional review board. Data collection and analysis was done by two examiners.
This retrospective observational study was conducted from June 2019 to March 2020. A total of 1571 cases were reviewed and cross-veri ication was carried out by postoperative photo igures. Sampling bias was minimized by keeping the eligibility criteria speci ic, which is, teeth requiring back to back stainless steel crowns in mandibular arch. A total of 134 pairs of back to back crowns were included after review.
The case reports were analysed from the patient record software of the university. 1571 cases which included stainless steel crowns were manually veriied with photo igures for segregating them as back to back crowns and also to restrict the population age from two to six years. The variables which were to be studied in study are the reasons for the requirement of back to back crowns like pulp therapy, class ll carious lesions and space-maintaining abutments.
Statistical analysis was done using SPSS Software version 23. Chi-square test was carried out to determine the correlation between the requirements of back to back stainless steel crowns.
Sample selection was done based on the following Inclusion criteria 1. Children of age 2 to 6 years 2. Children who required back to back crowns in mandibular arch

Exclusion criteria
1. Children who are above 6 years of age 2. Children who didn't require back to back crowns in the mandibular arch.
3. Children with special health care needs.

RESULTS AND DISCUSSION
A total of 134 pairs of back to back crowns which denote 368 teeth individually, were analysed. Majority of the patients in this study were categorized under the age group of 3 to 5 years ( Figure 1). The age of the patients who required more of pulp therapy in this study were the age group of 4 years ( Figure 2). Males were found to be treated more with back to back crowns than females ( Figure 3). Both the quadrants in the mandibular arch, that is the right and left quadrants were equally distributed ( Figure 4). 86.7% of the teeth requiring back to back crowns underwent pulp therapy. 28.5% of teeth required class 2 restorations. 19.2% of the teeth required both pulp therapy and class 2 restorations. Statistically, signi icant difference observed between pulp therapy and class 2 restorations (pvalue -0.003). Back to back stainless steel crowns were not given in mandibular arch as an abutment to space maintainer (Table 1). In Figure 1, X-axis represents the age of the patients participated in this study, Y-axis represents the number of participants; The majority of the patients requiring back to back stainless steel crowns in mandibular arch were from 3 years to 5 years of    age. In Figure 2, X-axis represents the age of the patients participated in this study, Y-axis represents the number of participants; Blue represents Class II restorations and Green represents Pulp therapy; Pulp therapy was the commonly observed reason for the requirement of back to back stainless steel crowns in mandibular arch. In Figure 3, X-axis represents the gender of the patients participated in this study, Y-axis represents the number of participants; Blue represents Class II restorations and Green represents Pulp therapy; Male children were highly treated with back to back crowns. In Figure 4, X-axis represents the name of the teeth involved, Yaxis represents the frequency of occurrence; Blue represents Class II restorations and Green represents Pulp therapy; Back to back stainless steel crowns in mandibular arch were equally distributed among the quadrants. Statistically signi icant difference observed between pulp therapy and class 2 restorations (chi-square -2.78; p-value-0.003 ) From the above results, it is clear that the most common requirement for back to back stainless steel crowns in mandibular arch in children aged 2 to 6 years was pulp therapy. Conventionally, pulp therapy in primary teeth were carried out using endodontic hand iles to shape and clean the root canals. But, recently an effective and ef icient rotary endodontic ile exclusive for primary teeth was introduced (Jeevanandan, 2017). All the cases in this study were rendered pulp therapy using this rotary ile system. These rotary iles for primary teeth were proven to be ef icient in operating time compared to hand iles (Panchal et al., 2019). Not only canal preparation time is reduced in using rotary iles in pedodontics, but also the obtu-ration quality despite the behaviour of the child was proven to be better than conventional preparation using hand iles (Govindaraju et al., 2017b,a;Jeevanandan and Govindaraju, 2018). To add to these ef icient studies, these pediatric rotary iles have proven to be more effective than reciprocating iles also (Lakshmanan et al., 2020;Nair et al., 2018).
The awareness and knowledge about these pediatric rotary iles have spread widely across many pediatric dentists and also among general dental practitioners (Govindaraju et al., 2017c). But just as the common saying "prevention is better than cure", more care has to be taken in preventing early childhood caries, sparing the child the hazardous outcomes of dental caries in an young age and also the trauma and stress undergone through a dental procedure. One of the most highly carried out preventive strategies against early childhood caries is the use of luoride. Fluoridated toothpastes were readily available over the counter and have proven ef icient in preventing dental caries (Ramakrishnan and Bhukri, 2018) Studies had been carried out in assessing the luoride content of bottled drinking water thereby improvising the preventive purview (Somasundaram et al., 2015). An innovative study has been carried out and proven the ef iciency of chewable toothbrushes for children which is an easy and commendable strategy in prevention of dental caries in children (Govindaraju, 2017). As the placement of a stainless steel involves reduction of tooth structure which is an invasive procedure, less invasive techniques such as predicting the dental status using biological markers should be studied more. A biochemical approach in preventing the early childhood caries is more effective as various markers can be assessed and proper measures can be taken (Subramanyam et al., 2018).
In this present study, out of 368 back to back crowns, 319 teeth required pulpectomy, 105 teeth required class 2 restorations and 71 teeth required pulp therapy followed by class 2 restorations. In a study, the mean prevalence of cavitated lesions in primary dentition was found to be 33.85%. Males were more affected than females. Mandibular molars and maxillary anterior teeth were the predominantly affected teeth (Sachdeva et al., 2015). In another prevalence study regarding dental caries in primary dentition, it has been found that the decay experience was common in second primary molars (Warren et al., 2002). According to recent studies, posterior teeth which have been rendered pulp therapy should be provided with a full coverage restorations and if cuspal coverage is to be obviated, short term strengthening is essential (Tikku et al., 2010). Proximal carious lesions are also a major reason for the requirement of a full coverage restoration in primary teeth (Azizi, 2014). Rising failure rate of Class 2 restorations using high viscosity Glass ionomer cement due to proximal breakdown was observed in a study, proving the need for a full coverage restoration in proximal caries (Scholtanus and Huysmans, 2007). Class 2 resin restorations show more failure than class 2 amalgam restorations (Overton and Sullivan, 2012).
In this present study all the stainless steel crowns were luted with type 1 glass ionomer cement. Studies of extracted primary molars have proven that the stainless steel crowns that were luted with resin modi ied glass ionomer cements have lesser microleakage than conventional cement. A study comparing conventional crown preparation for stainless steel crowns with that of halls technique, showed no statistically signi icant differences in microleakage between these two preparations (Gruythuysen et al., 2010).
Stainless steel crowns are given in permanent teeth also after endodontic procedures or even in case of cuspal fractures due to trauma. However in primary teeth cuspal fractures are uncommon. The awareness and knowledge in handling traumatic dental injuries among general dentists have grown enormously over the years (Ravikumar et al., 2017). Discussing about crowns in pediatric dentistry, esthetic crowns like zirconia crowns are gaining popularity among dentists as well as the patients. Providing a crown to a grossly decayed tooth or a tooth with proximal caries will prevent space loss due to migration of the adjacent teeth into the cavitated surface of the tooth. This thereby prevents future malocclusion sparing the need for orthodontic intervention. However, interdental spacings in permanent dentition due to developmental malformations like high frenum attachment has to be corrected through surgical intervention (Christabel, 2015).
In the mandibular arch, if there is any premature loss of primary tooth space maintainers like band and loop, extended band and loop, distal shoe were given in unilateral cases. In bilateral loss of tooth, lingual arch space maintainer is given. In cases, where the abutment tooth is carious or requires pulp therapy, this band is replaced with a stainless steel crown. In this present study, no such tooth was found with back to back stainless steel crowns. Not only pediatric dental patients are encountered with dental caries and pulpal in lammation but also, with much worse pathology like dental abscess, cysts and tumors such as ranula. (Packiri, 2017). Treating a child after acquiring dental caries is essential in preventing further detrimental progressions but preventing early childhood caries must be the irst goal for the parents, pedodontists and also the care takers of the children. Because, dental caries are not considered as a serious health issue by many parents till they are asymptomatic, which will eventually lead to a symptomatic problem. Dental neglect (Gurunathan and Shanmugaavel, 2016) is a serious issue leading to invasive treatment like pulp therapy which needs to be preserved by a full coverage restoration. This present study enumerated the common requirements for back to back stainless steel crowns in mandibular arch speci ically in children of age 2 to 6 years thereby providing a better insight of the progression and clinical manifestations of early childhood caries in such scenarios. The limitations of this study were that it doesn't include treatments done over a wide geographic region rather included the treatments done only by a few operators. This might have biased the formulation of the treatment plan leading to crown placement in a tooth which would have been arguable by a different clinician. More studies, including more different techniques and treatment plans should be carried out for more speci ic results and outcomes.

CONCLUSIONS
Out of 1571 stainless steel crowns given in the past year, 23% of them was back to back crowns in the mandibular arch. The most common requirement for back to back stainless steel crowns in the mandibular arch for children aged 2 to 6 years was pulp therapy. Next common requirement for back to back stainless crowns in the mandibular arch for children aged 2 to 6 years was found to be Class 2 carious lesions.