Amalgam Phase-Down Part 2: UK-Based Knowledge, Opinions, and Confidence in the Alternatives

Class II composite restoration technique teaching: A randomised controlled crossover laboratory-based trial involving a novel ringless sectional matrix technique

INTRODUCTION

Objectives were to assess how different techniques (including a novel ringless sectional matrix approach) affect students' restorative outcomes, and their preferences for and preparedness to clinically implement new techniques with the aim of introducing appropriate techniques to the undergraduate curriculum.

MATERIALS AND METHODS

Students performed two class II composite restorations in plastic teeth using two sectional matrix techniques (separating ring vs. without [ringless]), and two composite restorative techniques (incremental vs. injection-moulded bulk-fill). Restorations were assessed on multiple parameters which were combined to rate them as "good" or not. Online surveys assessed students' preferences for and preparedness to clinically implement new techniques.

RESULTS

Contact area concavity (OR = 106, p < .001) and cervical marginal overhang (OR = 7.4, p < .001) were much more likely with the separating ring compared to the ringless sectional matrix technique. "Good" restorations were 29.5 times more likely when using ringless compared to separating ring techniques and 3.3 times more likely when using the injection-moulding bulk-fill compared to layered composite technique. A majority of students preferred the ringless to separating ring sectional matrix technique and the injection-moulding bulk-fill to layered composite technique. Large majorities felt prepared to implement the new techniques clinically with no or minimal guidance.

CONCLUSIONS

A classic sectional matrix technique with separating ring resulted in a much greater occurrence of contact area concavity and cervical marginal overhang than a novel ringless approach. When allied with student preferences and clinical preparedness, inclusion of the novel ringless approach in the undergraduate curriculum can be supported alongside bulk-fill injection-moulding techniques.

The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T

OBJECTIVES

To measure mercury release from standardised hydroxyapatite/amalgam constructs during MRI scanning and investigate the impact of static field strength and radiofrequency (RF) power on mercury release.

METHODS

Amalgam was placed into 140 hydroxyapatite disks and matured for 14-days in artificial saliva. The solution was replaced, and samples split into five groups of 28 immediately prior to MRI. One group had no exposure, and the remainder were exposed to either a 3T or 7T MRI scanner, each at high and low RF power. Mercury concentration was measured by inductively coupled plasma mass spectrometry. Groups were compared using one-way ANOVA, and two-way ANOVA for main effects/ interaction of field strength/ RF power.

RESULTS

Mercury concentration was increased in the 7T groups (high/ low: 15.43/ 11.33 ng mL^-1) and 3T high group (3.59) compared to control (2.44). MRI field strength significantly increased mercury release (p < .001) as did RF power (p = .030). At 3T, mercury release was 20.3 times lower than during maturation of dental amalgam, and for the average person an estimated 1.50 ng kg^-1 of mercury might be released during one 3T investigation; this is substantially lower than the tolerable weekly intake of 4,000 ng kg^-1.

CONCLUSION

Mercury release from amalgam shows a measurable increase following MRI, and the magnitude changes with magnetic field strength and RF power. The amount of mercury released is small compared to release during amalgam maturation. Amalgam mercury release during MRI is unlikely to be clinically meaningful and highly likely to remain below safe levels.

Developments in resin-based composites

With the phasing down of dental amalgam use in response to the Minamata Convention, it is likely that resin-based composite restoratives will be the dental material of choice for the direct restoration of compromised dentition in the UK, at least for the foreseeable future. The current materials have a finite lifespan, with failures predominately due to either secondary caries or fracture. Consequently, there is considerable in vitro research reported each year with the intention of producing improved materials. This review describes the recent research in materials designed to have low polymerisation shrinkage and increased mechanical properties. Also described is research into materials that are either antimicrobial or are designed to release ions into the surrounding oral environment, with the aim of stimulating remineralisation of the surrounding dental tissues. It is hoped that by describing this recent research, clinicians will be able to gain some understanding of the current research that will potentially lead to new products that they can use to improve patient treatment in the future.

Provides an overview of recent research developments aimed at improving the performance of resin-based composites.

Details the recent developments in monomers and fillers to produce resin-based composites that either have lower polymerisation shrinkage or better mechanical properties compared to current commercially available products.

Describes recent research on developing resin-based composites that can act as potential sources of antimicrobial or remineralising agents.

Sectional matrix solutions: the distorted truth

Sectional matrix techniques offer more predictable solutions to achieving contact areas when placing direct interproximal posterior composites than circumferential matrix techniques, resulting in reduced reported complaints of food packing from patients. Despite this, a large majority of UK dentists and therapists don't currently use them. Sectional matrix systems are technique-sensitive to use, which can be a barrier to implementation for inexperienced users. The matrices can easily distort during their placement and stabilisation and when placing the restorative material. This can result in unwanted, clinically relevant problems in the resulting restorations, some of which may not be discernible once they have occurred. This paper explores the advantages and disadvantages of sectional matrices and the processes and techniques involved in their use, before discussing the potential for distortion at each step. It offers solutions to some of the commonly seen problems which will provide more predictable outcomes for those already using these techniques and encourage non-users to add them to their armamentarium.