Improving the Prognosis of Compromised First Permanent Molars in Children

Abstract

First permanent molars (FPMs) are widely regarded as being the most susceptible to developing dental caries. Due to the timing of hard tissue formation, these teeth are also more prone to idiopathic hypomineralisation enamel defects, known as molar-incisor hypomineralisation (MIH). Molar-incisor hypomineralisation affects one out of six children globally and in the United Kingdom (UK), its prevalence is around 16%. The most important treatment decision regarding compromised FPMs (cFPMs) is whether to retain or extract them. Unfortunately, this conversation typically occurs very early in a child's life due to the importance of considering the ‘ideal’ timing should extraction be favoured. According to the National Clinical Guidelines, elective extraction of FPMs with ‘a questionable long-term prognosis’ should be considered. This technique is based on a pragmatic orthodontic approach towards extracting FPMs that are considered to be of poor prognosis at the optimal time to permit spontaneous space closure during the dentition development. However, this often means a costly and upsetting hospital general anaesthesia (GA) admission. Thus, the aim of this project was to improve the prognostic evaluation of cFPMs in children through the understanding of the current protocol of management of children with cFPMs referred to specialist centres and defining the diagnostic thresholds of management of cFPMs and its compatibility with the contemporary operative evidence-based science and materials. To ultimately change the current orthodontic guidelines used in the UK and followed by other countries and reduce the number of hospital admissions of GA in children. To achieve this aim, a question was raised about the current management of children with cFPMs and the diagnostic threshold of extraction decision. Only a few national and international survey-based research papers have investigated management of children with cFPMs. Thus, to answer these questions, an evaluation of the protocol of management of children with cFPMs referred to specialist paediatric dental department at a London hospital NHS trust (Guy’s and St Thomas’ Hospital NHS Trust (GSTT)) was conducted. A framework/ database was established, and a retrospective evaluation was performed, based on the clinical case-records of medically fit children referred for management of cFPMs at GSTT. The presence of hypomineralisation and/or post-eruptive breakdown (PEB) and the proposed care plans were recorded while radiographic signs of severity were scored using the ICDAS index after researcher calibration. At Guy's and St Thomas' NHS Foundation Trust (GSTT), 249 records were included in a four-month period. Nearly 81% of the patients were planned for extraction of at least one cFPM, while 19.3% were managed without extractions. More than half of the extraction cases (n=105) had radiographic radiolucencies that did not exceed the middle third of dentine in the worst-affected FPM. General anaesthesia was used in 97.5% of the cases and 40.8% had never received previous treatment in any of their affected FPMs. Children who were referred with cFPMs at GSTT tended to undergo hospitalisation for extraction under GA. The management at GSTT poses further research questions about the current care protocol for patients with cFPMs referred to other specialist care centres in the UK. Two additional UK hospital specialist centres (Newcastle University Dental Hospital (NUDH) and Liverpool University Dental Hospital (LUDH)) were also included in the retrospective evaluation using the validated methodology developed in the first study. From 233 and 116 case notes screened in NUDH and LUDH, 200 and 80 met the selection criteria, respectively. Thirty-nine percent at NUDH and 56% at LUDH were planned to have extraction of at least one FPM. Nearly 58% in NUDH and 40% of patients in LUDH had a maximum radiographic radiolucency severity that did not exceed the middle third of dentine in the worst-affected cFPM. GA was the most used method of pain control within the three national centres (75.6%, 60% and 97.5% in NUDH, LUDH and GSTT, respectively) and a substantial number of the extraction cases (82.1%, 80% and 40%, respectively) received no previous treatment in any of their cFPMs. Collectively, these analyses have shown a national trend in the management of children with cFPMs within the three sampled centres in the UK. The children who were referred to the UK centres due to cFPM(s) tended to undergo hospitalisation for extraction. The clinical rationality of the local (UK) approach was questioned. Further questions were raised about the current care protocol for children with cFPMs referred to specialist centres globally, and the current diagnostic thresholds of management of cFPMs in children internationally. Thus, a multi-centre retrospective evaluation employed the same methodology to access how specialist paediatric dental departments at seven international centres in five different countries managed children referred with cFPMs and to compare with the three national (UK) centres. The following international centres and number of records have been included: King Saud University Medical City / KSU (269), King Abdulaziz Medical City / KAMC (160), University of Jordan Hospital / UJ (154), Warszawski Uniwersytet Medyczny / WUM (104), Miły Uśmiech Stomatologia / MUS (49), Academic Centre for Dentistry Amsterdam / ACTA (99) and University of Pittsburgh / UPITT (117) over a consecutive period in 2019. In contrast to UK centres, extraction cases were minority in each international centre, being 1% or less in KSU, WUM and MUS and reaching 8-10% in KAMC, ACTA and UPITT. The highest percentage of extraction cases internationally was recorded in UJ (25.3%) where it was still lower than all other UK centres. The majority of the extraction cases in the international centres had a minimum radiolucency reaching the inner third of dentine or documented as restored in the worst-affected element (99.9% at KSU; 100% at KAMC and 89.7% at UJ; 100% at WUM; 70% at ACTA; 100% at UPITT). Although GA was also present as a method of pain control in the international centres, whenever extraction was planned, alternative modalities such as inhalation sedation or local anaesthesia alone were present and predominant in a few of the sampled international centres (69.2% in KAMC, 70% in ACTA). In chapter five, the feasibility of a biochemical threshold to differentiate between the clinical severities of MIH-affected enamel using non-invasive Raman spectroscopic analysis was investigated. Stereomicroscopic images of extracted human FPMs, showing demarcated opacities in enamel, were scored by four independent examiners, to assess their severity. Using high-resolution Raman microscopy, the ratio of the characteristic vibration mode of the normalised amide I, carbonate and phosphate bands were calculated from 621 points scanned on a line scan across the different severities of the opacities. The logistic regression analysis indicated that the cut-off values (carbonate / phosphate) and (amide 1/ phosphate) between the white-creamy (WC) and yellow-brown (YB) lesions were 0.13 and 0.12 peak ratio respectively, which meant that >0.13 in carbonate / phosphate or >0.12 for amide 1/ phosphate represented YB tissue and <0.13 or <0.12 respectively represented WC tissue with 90% sensitivity and 92.6% specificity (p <0.0001) for carbonate / phosphate cut-off value and 95% sensitivity and 94.7% specificity (p <0.0001) for amide 1 / phosphate cut-off value. The logistic regression analysis indicated that the cut-off value of peak ratio between WC and sound tissue was 0.01 with 98.9% sensitivity and 10.5% specificity (p =0.001), whereas it was equal to 0.23 for amide 1 / phosphate cut-off value between WC and sound tissue with 98.9% sensitivity and 5.3% specificity. The defined Raman diagnostic thresholds were validated against the clinical severity. For the diagnostic threshold between WC versus YB lesions, examiners’ visual characterisation and the validated Raman carbonate / phosphate and amide 1/ phosphate cut-off threshold showed a substantial agreement ( Kappa=0.63 and 0.69 respectively). Thus, Raman spectroscopy could be used objectively in in-vitro studies discriminating the clinical severity of MIH demarcated opacities. In chapter six, a clinical-based minimally invasive (MI) treatment protocol to manage different severities of cFPMs in children is proposed. This protocol is applied into a proposition for a future clinical observational cohort study. The developed research methodology considered not affecting the ideal time of extraction if still needed. The feasibility of applying this observational clinical study to test the efficiency of MI as an alternative for the current management of extracting affected FPMs under GA was assessed. The clinical treatment protocol and the methodology were reviewed by four GSTT-NHS specialists, a research team, including restorative and paediatric academics and consultants in the field and two independent reviewers. The feasibility study showed a potential recruitment of (5.4 / week) at GSTT, thus a total of about 130 patients is expected in six months, considering that 70% of the patients will agree to join the study that informed the feasibility of 91 patients in six months.