Resin tags formation by modified Renewal MI formulations in a carious dentine model.

Objectives: To determine which components in a new restorative material (Renewal MI) improve its ability to form resin tags within demineralized dentine. Methods: Varied components included polylysine (PLS), monocalcium phosphate (MCP), powder to liquid ratio (PLR), 4-methacryloyloxyethyl trimellitate anhydride (4META), and polypropylene glycol dimethacrylate (PPGDMA). Urethane dimethacrylate (UDMA), containing PPGDMA (24 wt%) and 4META (3 wt%), was mixed with glass filler with MCP (8 wt%) and PLS (5 wt%). PLR was 3:1 or 5:1. Reducing MCP and/or PLS to 4 and 2 wt% respectively or fully removing MCP, PLS, 4META or PPGDMA gave 16 formulations in total. Renewal MI, Z250 (with or without Scotchbond Universal adhesive) and Activa were used as commercial comparators. Collagen discs were obtained by totally demineralizing 2 mm thick, human, premolar, coronal dentine discs by immersion in formic acid (4M) for 48 h. The restorative materials were then applied on top (n = 3), before dissolving the collagen in sodium hypochlorite (15%). SEM/EDX was employed to determine resin tags length, composition, and surface coverage. Results: Tags were >400, 20 and 200 µm and covered 62, 55 and 39% of the adhesion interface for Renewal MI, Scotchbond and Activa, respectively. With experimental formulations, they were 200 and >400 µm long with high vs. low PLR and composed primarily of polymerized monomers. Percentages of the adhesion interface covered varied between 35 and 84%. Reducing PLS or MCP caused a decline in coverage that was linear with their concentrations. Reducing MCP had lesser effect when PLS or PLR were low. Removal of 4META caused a greater reduction in coverage than PPGDMA removal. Conclusion: PLS, MCP, 4META, PPGDMA and low PLR together enhance Renewal MI tags formation in, and thereby sealing of, demineralized dentine.

The effect of varying monocalcium phosphate and polylysine levels on dental composite properties.

OBJECTIVES: The aim was to quantify effects of polylysine (PLS, 2 or 5 wt%) and monocalcium phosphate (MCP, 4 or 8 wt%) on properties of dental composites. METHODS: Light-activated, lower surface polymerisation kinetics versus sample depth (1-4 mm) of 4 formulations were quantified using ATR-FTIR. Water sorption and solubility (at 1 week) were assessed following ISO/4049. PLS release (over 1 month) and biaxial flexural strength (over 6 months) of fully-cured, water-immersed, 1 mm thick discs were determined. Surface mineral precipitation, following immersion in simulated body fluid (SBF), was assessed by SEM. Z250 was used as a conventional composite comparator. RESULTS: With 40s light exposure, increasing depth (from 1 to 4 mm) led to enhanced delay before polymerisation (from 3 to 17s) and decreased final conversion (72-66%) irrespective of PLS and MCP level. Increasing PLS and MCP raised solubility (4-13 µg/mm3). Water sorption (between 32 and 55 µg/mm3) and final PLS release (8-13% of disc content) were raised primarily by increasing PLS. Higher PLS also reduced strength. Strength reached minimum values (69-94 MPa) at 3 months. Surface mineral deposition was enhanced by increased MCP. For Z250, polymerisation delays (3-6s) and final conversions (55-54%) at 1-4 mm depth, solubility (0 µg/mm3), water sorption (16 µg/mm3) and strength (180 MPa) were all significantly different. CONCLUSION: Delay time increased whilst final conversion decreased with thicker samples. Higher PLS enhances its percentage release, but lower level is required to keep water sorption, solubility and mechanical properties within ISO 4049 recommendations. Doubling MCP raises solubility and enhances minerals reprecipitation with minimal mechanical property compromise.

Renewal MI Dental Composite Etch and Seal Properties.

This study's aim was to assess whether the Renewal MI composite can self-etch enamel, seal sound cavities, and stabilize demineralized dentine. Etching was assessed using scanning electron microscopy (SEM). Cavity sealing was quantified using the ISO-11405 dye microleakage test. Demineralized dentine stabilization was evaluated by visualizing resin tag formation, enzyme activity and mineral precipitation at the adhesion interface. Renewal MI provided a mild etching of sound enamel in comparison with 37% phosphoric acid. It provided a comparable seal of sound cavities to Z250/Scotchbond Universal adhesive and a superior seal to Activa, Fuji IX and Fuji II LC. With demineralized dentine, Renewal MI formed 300-400 µm resin tags covering 63% of the adhesion interface compared with 55 and 39% for Z250/Scotchbond and Activa. Fuji IX and Fuji II LC formed no resin tags. A higher tag percentage correlated with lower surface enzyme activity. Unlike Activa and Fuji II LC, Renewal MI promoted mineral precipitation from simulated body fluid, occluding adjacent dentinal tubules within 6 months. These novel etching and sealing properties may facilitate Renewal MI's application in minimally invasive dentistry.

Variations in provision of dental general anaesthetic for children in England.

Introduction Dental general anaesthetic (DGA) remains one of the main modalities to deliver treatment to paediatric patients. The main central registry system which is used as a proxy measure of DGA provision is the Hospital Episode Statistics (HES) data on hospital admission of children for dental extractions. This database does not accurately reflect the number of DGAs as it omits non-hospital-based providers and the data includes treatment under sedation.Aims The aim is to describe the paediatric DGA service provision across England and determine type of provider (NHS Trusts or Community Dental Services [CDSs]), type of lists (extraction or comprehensive care) and the speciality planning the service.Methods Potential providers were identified using the provider-level analysis in HES database (for NHS trusts) and the NHS Business Services Authority and internet-based search engine (for CDS providers). All potential providers were contacted (n = 204) and provided with a pro forma to collect data.Results Response rate was 82% and 115 providers confirmed provision of paediatric DGA. These were mostly NHS trusts (72%). Not all providers appeared in the HES database (25%). Half of the providers provided separate lists for exodontia versus comprehensive care. Only 32% of the lists were planned by specialists in paediatric dentistry. All regions, apart from London, had some comprehensive care lists planned by non-paediatric dentists.Conclusion The results highlighted the inaccuracies in the HES, variation in service provision across England and the lack of paediatric speciality-led DGA services. Paediatric DGA needs to be better recorded and commissioned.