Christopher Tredwin

Hydrogen peroxide tooth-whitening (bleaching) products: Review of adverse effects and safety issues

Hydrogen peroxide in the form of carbamide peroxide is widely used for tooth whitening (bleaching), both in professionally- and in self-administered products. Adverse effects have become evident. Cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure. Tooth sensitivity is experienced in 15-78% of patients undergoing external tooth bleaching. However, clinical studies addressing other adverse effects are lacking. Direct contact with hydrogen peroxide induces genotoxic effects in bacteria and cultured epithelial cells, but the effect is reduced or totally abolished in the presence of metabolising enzymes. Several carcinogenesis studies, including the hamster cheek pouch model, indicate that hydrogen peroxide (H2O2) might possibly act as a promoter. Until further clinical research is concluded to address the question of possible carcinogenicity, it is recommended that: tooth-bleaching products using concentrated H2O2 should not be used without gingival protection; that H2O2 containing products should be avoided in patients with damaged or diseased soft tissues. For nightguard vital bleaching, minimal amounts of low dose H2O2 (including in the form of carbamide peroxide) are preferred, thereby avoiding prolonged and concentrated exposures.

Drug-induced Disorders of Teeth

It is essential that every health care professional who is involved with the prescription or recommendation of drugs be fully aware of any resultant disorders that may arise as a side-effect. A range of drugs can affect the teeth. In this review article, drugs that have the potential to induce changes in teeth have been classified as those leading to tooth discoloration (intrinsic and extrinsic), physical damage to tooth structure (enamel, dentin, and cementum), and alteration in tooth sensitivity.

Review of nanomaterials in dentistry: interactions with the oral microenvironment, clinical applications, hazards, and benefits.

Interest in the use of engineered nanomaterials (ENMs) as either nanomedicines or dental materials/devices in clinical dentistry is growing. This review aims to detail the ultrafine structure, chemical composition, and reactivity of dental tissues in the context of interactions with ENMs, including the saliva, pellicle layer, and oral biofilm; then describes the applications of ENMs in dentistry in context with beneficial clinical outcomes versus potential risks. The flow rate and quality of saliva are likely to influence the behavior of ENMs in the oral cavity, but how the protein corona formed on the ENMs will alter bioavailability, or interact with the structure and proteins of the pellicle layer, as well as microbes in the biofilm, remains unclear. The tooth enamel is a dense crystalline structure that is likely to act as a barrier to ENM penetration, but underlying dentinal tubules are not. Consequently, ENMs may be used to strengthen dentine or regenerate pulp tissue. ENMs have dental applications as antibacterials for infection control, as nanofillers to improve the mechanical and bioactive properties of restoration materials, and as novel coatings on dental implants. Dentifrices and some related personal care products are already available for oral health applications. Overall, the clinical benefits generally outweigh the hazards of using ENMs in the oral cavity, and the latter should not prevent the responsible innovation of nanotechnology in dentistry. However, the clinical safety regulations for dental materials have not been specifically updated for ENMs, and some guidance on occupational health for practitioners is also needed. Knowledge gaps for future research include the formation of protein corona in the oral cavity, ENM diffusion through clinically relevant biofilms, and mechanistic investigations on how ENMs strengthen the tooth structure.

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol–gel method: Bonding to titanium and scanning electron microscopy

OBJECTIVES Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) production has been characterised and optimised by the sol-gel method and the dissolution and biological properties of these materials were investigated. It was the objective of this study to investigate the potential bond strength and interaction of these materials with titanium. METHODS HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the FHA and FA sol-gels. Using a spin coating technique the sol-gels were coated onto commercially pure titanium disks and crystallised at various temperatures. Using scanning electron microscopy (SEM) and elemental analysis, the surface characteristics, coating thickness and interaction of the Ti substrate and coating were investigated. The bond strengths of the coating to the Ti were investigated using an Instron Universal Load Testing Machine. Statistical analysis was performed with a two-way analysis of variance and post hoc testing with a Bonferroni correction. RESULTS (1) Coating speed inversely influenced the coating thickness. (2) Increasing fluoride ion substitution and heating temperature significantly increased bond strength and (3) increasing fluoride ion substitution increased the coating thickness. SIGNIFICANCE FHA and FA synthesised using the sol-gel technique may offer a superior alternative to coating titanium implants with HA and plasma spraying. HA, FHA and FA materials synthesised by the sol-gel method may also have a use as bone grafting materials.

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method. Optimisation, characterisation and rheology.

OBJECTIVES Currently, most titanium implant coatings are made using hydroxyapatite and a plasma spraying technique. There are however limitations associated with plasma spraying processes including poor adherence, high porosity and cost. An alternative method utilising the sol-gel technique offers many potential advantages but is currently lacking research data for this application. It was the objective of this study to characterise and optimise the production of Hydroxyapatite (HA), fluorhydroxyapatite (FHA) and fluorapatite (FA) using a sol-gel technique and assess the rheological properties of these materials. METHODS HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethylphosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the sol-gel derived FHA and FA. Optimisation of the chemistry and subsequent characterisation of the sol-gel derived materials was carried out using X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA). Rheology of the sol-gels was investigated using a viscometer and contact angle measurement. RESULTS A protocol was established that allowed synthesis of HA, FHA and FA that were at least 99% phase pure. The more fluoride incorporated into the apatite structure; the lower the crystallisation temperature, the smaller the unit cell size (changes in the a-axis), the higher the viscosity and contact angle of the sol-gel derived apatite. SIGNIFICANCE A technique has been developed for the production of HA, FHA and FA by the sol-gel technique. Increasing fluoride substitution in the apatite structure alters the potential coating properties.

Academic environment in a newly established dental school with an enquiry‐based curriculum: perceptions of students from the inaugural cohorts

INTRODUCTION Established in 2007, Peninsula Dental School offers a highly innovative, enquiry-based, student-led, patient-centred curriculum. It is one of the first dental schools in UK to be based exclusively in a primary care setting. This study was carried out to evaluate the academic environment at Peninsula Dental School and to identify differences between expectations of new entrants and perceptions of senior cohorts. METHODS This was a cross-sectional survey utilising an online questionnaire based on Dundee Ready Educational Environment Measure (DREEM). The subjects were 234 dental students from all years in this enquiry-based Bachelor of Dental Surgery programme. RESULTS The response rate to the questionnaire was 56.42% with an equal gender distribution of the participants. The overall mean DREEM score of the four cohorts was 143.58 (SD ± 20.84), and the mean score for individual items was 2.87 (SD ± 0.41). The reliability of the DREEM data as a whole was strong (α = 0.93). The difference in questionnaire means for the new entrants and the senior cohorts was not significant (P > 0.05). The ANOVA results showed that there were no significant effects of age, gender or ethnicity on the mean DREEM scores. The MANOVA results showed a significant effect of ethnicity with regard to perceptions of teachers and atmosphere. CONCLUSIONS An enquiry-based, student-centred curriculum at the Peninsula Dental School provides a positive academic environment for the students.

An Analysis of the Effect of a Vent Hole on Excess Cement Expressed at the Crown–Abutment Margin for Cement‐Retained Implant Crowns

PURPOSE The labial margins of anterior implant-retained crowns are often positioned subgingivally for a superior esthetic appearance. One of the consequences of subgingival margins is the increased risk of leaving excess cement behind following cementation. This can lead to potential problems, including peri-implant inflammation, soft tissue swelling, soreness, bleeding or suppuration on probing, and bone loss. The purpose of this laboratory study was to investigate the effect of placement, location, and diameter of a vent hole on the amount of cement being expressed at the margin of an anterior implant abutment-retained crown. MATERIALS AND METHODS Three implant crown copings were fabricated to fit on the same custom abutment. Three vent diameters (0.75, 1.25, and 1.65 mm) and three locations on the palatal surface of the coping (cervico-palatally, mid-palatally, inciso-palatally) were chosen for vent hole placement. For each test, the coping was cemented onto the abutment under standardized conditions. A preweighed thin coating of cement was applied to the fit surface of the coping. The amount of cement expressed at the margin and vent hole was measured by weight and calculated as a proportion of the amount of cement placed in the coping before seating. The procedure was completed 15 times for each variable. The results were statistically analyzed using univariate ANOVA with post hoc Bonferroni-adjusted independent samples t-tests. RESULTS The presence of a vent hole influenced the proportion of cement expressed at the coping margin (p < 0.05). The location of a vent hole influenced the proportion of cement expressed at the coping margin (p < 0.05), with the exception of the mid-palatal and inciso-palatal positioning where there was no significant difference (p= 0.61) between groups. The diameter of the vent hole did not significantly influence the proportion of cement expressed at the coping margin (p= 0.096). CONCLUSIONS When using anterior cement-retained implant crowns, the use of a 0.75-mm mid-palatal or inciso-palatal vent hole to minimize the amount of cement expressed at the margin during cementation should be considered.

The influence of maxillary central incisor height-to-width ratio on perceived smile aesthetics

Objective To determine the influence of varying the width-to-height ratio of maxillary central incisors on perceived smile aesthetics.Design Cross-sectional study.Setting Postgraduate dental teaching hospital.Methods A posed female smile was digitally modified using Adobe Photoshop®. Three images were created; central incisors with normal form, tooth wear and delayed apical migration. For each image the length of the teeth was altered to create a set of nine images with normal form (66% to 96% width-to-height ratios), and sets of five images with tooth wear and with delayed apical migration (78% to 96% ratios). The images in each set were ranked in order of most to least attractive by 32 dentists, 32 technicians and 32 patients.Results An 82% width-to-height ratio was perceived as the most attractive for normal central incisors although there is variability in the responses. There is a definite trend towards the extremes of very long or very short teeth being less attractive. The very long central incisors, and those with tooth wear were perceived as unattractive. The patients rated fewer images from the tooth wear and delayed apical migration sets as unattractive compared to the dentists and technicians.Conclusion The width-to-height ratios perceived as most attractive correspond with the higher end of ideal ratios proposed in the dental literature (75-80% width-to-height ratio). Significant differences exist between the aesthetic perceptions of dentists, technicians and patients and there is lack of agreement within each group, in particular within the patient group. The individual variability in patient response should be taken into account during treatment planning.

Antibacterial activity and biofilm inhibition by surface modified titanium alloy medical implants following application of silver, titanium dioxide and hydroxyapatite nanocoatings

Abstract One of the most common causes of implant failure is peri-implantitis, which is caused by bacterial biofilm formation on the surfaces of dental implants. Modification of the surface nanotopography has been suggested to affect bacterial adherence to implants. Silver nanoparticles are also known for their antibacterial properties. In this study, titanium alloy implants were surface modified following silver plating, anodisation and sintering techniques to create a combination of silver, titanium dioxide and hydroxyapatite (HA) nanocoatings. Their antibacterial performance was quantitatively assessed by measuring the growth of Streptococcus sanguinis, proportion of live/dead cells and lactate production by the microbes over 24 h. Application of a dual layered silver–HA nanocoating to the surface of implants successfully inhibited bacterial growth in the surrounding media (100% mortality), whereas the formation of bacterial biofilm on the implant surfaces was reduced by 97.5%. Uncoated controls and titanium dioxide nanocoatings showed no antibacterial effect. Both silver and HA nanocoatings were found to be very stable in biological fluids with material loss, as a result of dissolution, to be less than 0.07% for the silver nanocoatings after 24 h in a modified Krebs-Ringer bicarbonate buffer. No dissolution was detected for the HA nanocoatings. Thus, application of a dual layered silver–HA nanocoating to titanium alloy implants creates a surface with antibiofilm properties without compromising the HA biocompatibility required for successful osseointegration and accelerated bone healing.

Preparedness of dental graduates for foundation training: a qualitative study

Aims The aims of this study were to articulate the concept of preparedness of dental graduates for foundation training programme in the United Kingdom and identify the essential attributes of preparedness.Methods A qualitative approach using semi-structured interviews was used to explore the concept of preparedness. The study was carried out in the South West region of England. Participants were recruited from a range of stakeholders in dental education and foundation training using purposive sampling. Participants were recruited using email through appropriate professional channels. Stakeholders included dental students (DS), dental academics (DA), foundation dental practitioners (FDP), foundation trainers (FT), general dental practitioners (GDP) and a postgraduate dental deanery representative (DDR). Interviews were transcribed verbatim and data were imported into NVivo 9 and analysed thematically.Results Sixteen interviews were carried out with representation from all stakeholder groups. Participants expressed their views on a range of issues related to the preparedness of dental graduates.Conclusions This study provides useful insights into the concept of preparedness as perceived by the stakeholders. The findings of this study may offer clarity on the essential attributes required by dental graduates upon entry into foundation training.