Abstract
Aims and objectives: the aim of this dissertation was to determine the effectiveness of a minimally invasive indirect clinical pulp protection technique in preserving pulp vitality in symptomatic teeth in vivo. The objectives were firstly to assess the in-vitro characteristics and mechanical behaviour of the interfaces between MTA and the overlying restorations of GIC and resin composite. The second objective was to assess the effect of each excavation technique (rotary drill versus CarisolvTM gel) in promoting the remineralization of caries-affected dentine capped with mineral trioxide aggregate in deep carious teeth in-vitro. The third objective was to compare clinically and radiographically the one year outcomes of indirect pulp protection performed using mineral trioxide aggregate (MTA) in teeth with deep carious lesions excavated using a minimally invasive clinical protocol (CarisolvTM gel chemomechanical system and an operating microscope) with a control protocol (rotary burs with no magnification) in patients presenting with signs and symptoms of reversible pulpitis. The fourth objective was to determine the reduction in bacterial load before and after excavation with the two clinical protocols and to identify the bacterial flora composition / diversity in superficial and deep carious dentine samples within teeth included in the clinical trial.Materials and methods: The in-vitro study involved shear bond strength testing and SEM fractography of MTA discs bonded to RC with an etch and rinse adhesive or conventional GIC after 10-minute, 24-hour, 72-hour and 30-day of MTA setting intervals. The other in-vitro study involved using Raman spectroscopy and Knoop microhardness of the MTA/dentine interface at 24 hours and 14 days intervals in cavities of teeth excavated either with rotary bur or CarisolvTM gel. In addition, SEM was used to assess surface topography of dentine after excavation with gel/bur. 3 A one year duration, randomised controlled clinical trial was undertaken which involved recruiting patients with signs of reversible pulpitis from King’s College London Dental Institute at Guy’s Hospital. Standardised clinical and radiographic investigations involving CBCT and PA radiographs at baseline and one-year follow-up were used to assess pulp pathology (presence/absence of PA radiolucencies). Caries was excavated conventionally using rotary burs/no magnification in the control group and CarisolvTM gel/operating microscope in the minimally invasive group. Each tooth received an indirect pulp capping with MTA followed by an intermediate layer of GIC before placing a resin composite (RC) restoration in one visit. In addition, bacterial load and composition of the bacterial flora were assessed using non-culture-based DNA extraction, qPCR and sequencing of the 16S rRNA gene by using next-generation high throughput sequencing.
Result: In-vitro studies showed higher shear bond strength of RC to MTA after 24hr, 7 and 30 days compared to that of GIC to MTA which was higher in the initial 10 minutes setting group. Also baseline mineral content and microhardness of dentine were significantly lower in samples excavated with CarisolvTM gel in comparison to those excavated with rotary burs (p≤0.05). However, there were comparable mineral levels after 14 days between them after storage in simulated body fluid (p≥0.05), SEM images showed partially open dentine tubules with less smear layer after CarisolvTM gel excavation compared to more occluded dentine tubules with an abundance of smear layer after rotary bur excavation. Results from the clinical trial show 101 restorations (55 and 46 restorations in control and minimally invasive groups respectively) were placed randomly in 86 patients as part of the clinical trial. Success rates were 73.3% and 90% in the control and the minimally invasive groups, respectively. The minimally invasive protocol in molar teeth showed a higher odds ratio of success compared to the 4 control protocol and premolars, respectively. CBCT detected more PA lesions than PA radiographs. Teeth with “severe” reversible pulpitis symptoms lost vitality more often than teeth with “mild” symptoms. Microbiological analysis showed no significant difference in reduction of bacterial load between the minimally invasive technique and the control protocol. Lactobacillus was the most abundant genus in the superficial and deep caries samples and there was no significant difference in bacterial composition between superficial and deep carious dentine.
Conclusions: Placement of RC over partially set MTA in one visit vital pulp therapy avoided considering the low bond strength values achieved after 10 min from placement. Although CarisolvTM gel excavation retains more caries-affected dentine in comparison to bur excavation, remineralisation of this remaining tissue is evident after two weeks. The use of CarisolvTM gel provides an alternative to rotary burs in terms of preserving tooth structure and ability to provide dentine remineralization, a clinical advantage in minimally invasive operative dentistry. The minimally invasive protocol was more effective in preserving pulp vitality in teeth with reversible pulpitis compared to the control protocol. The minimally invasive protocol was able to reduce bacterial numbers in dentine caries after excavation as well as the control protocol. There was no significant difference in bacterial composition between superficial and deep carious dentine samples. However, it was noted that carious lesions can be classified according to the relative abundance of Lactobacillus species. Carious lesions with low-Lactobacillus abundance were dominated by other bacterial taxa which were frequently isolated from root canal infections.
| Date of Award | 1 Nov 2017 |
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| Original language | English |
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| Supervisor | Francesco Mannocci (Supervisor) & Avijit Banerjee (Supervisor) |