Proanthocyanidins-Loaded Nanoparticles Enhance Dentin Degradation Resistance

Previous studies reported that grapeseed extract (GSE), which is rich in proanthocyanidins (PAs), improves the biodegradation resistance of demineralized dentin. This study aimed to investigate the effect of a new GSE delivery strategy to demineralized dentin through loading into biodegradable polymer poly-[lactic-co-glycolic acid] (PLGA) nanoparticles on the biodegradation resistance in terms of structural stability and surface/bulk mechanical and biochemical properties with storage time in collagenase-containing solutions. GSE-loaded nanoparticles were synthetized by nanoprecipitation at PLGA/GSE (w/w) ratios of 100:75, 100:50, and 100:25 and characterized for their morphological/structural features, physicochemical characteristics, and drug loading, entrapment, and release. Nanoparticle suspensions in distilled water (12.5% w/v) were applied (1 min) to demineralized dentin specimens by simulating pulpal pressure. The nanoparticle delivery was investigated by scanning electron microscopy (SEM)/transmission electron microscopy (TEM), and the GSE release from the delivered nanoparticles was further characterized. The variations in surface and bulk mechanical properties were characterized in terms of reduced elastic-modulus, hardness, nanoindentation testing, and apparent elastic-modulus with a storage time up to 3 mo. Hydroxyproline release with exposure to collagenase up to 7 d was estimated. An etch-and-rinse dentin adhesive was applied to investigate the morphology of the resin-dentin interface after nanoparticle delivery. Treatment with the GSE-loaded nanoparticles enhanced the collagen fibril structural resistance, reflected from the TEM investigation, and improved the biomechanical and biochemical stability of demineralized dentin. Nanoparticles having PLGA/GSE of 100:75 (w/w) showed the highest cumulative GSE release and were associated with the best improvement in biodegradation resistance. TEM/SEM showed the ability of the nanoparticles to infiltrate dentinal tubules' main and lateral branches. SEM revealed the formation of a uniform hybrid layer and well-formed resin tags with the presence of numerous nanoparticles located within the dentinal tubules and/or attached to the resin tag. This study demonstrated the potential significance of delivering collagen crosslinkers loaded into biodegradable polymer nanoparticles through the dentinal tubules of demineralized dentin on the biodegradation resistance.

Chlorhexidine Nanocapsule Drug Delivery Approach to the Resin-Dentin Interface

In this study, we are introducing a new drug-delivery approach to demineralized dentin substrates through microsized dentinal tubules in the form of drug-loaded nanocapsules. Chlorhexidine (CHX) is widely used in adhesive dentistry due to its nonspecific matrix metalloproteinase inhibitory effect and antibacterial activities. Poly(ε-caprolactone) nanocapsules (nano-PCL) loaded with CHX were fabricated by interfacial polymer deposition at PCL/CHX ratios of 125:10, 125:25, and 125:50. Unloaded nanocapsules (blank) were fabricated as control. The fabricated nanocapsules were characterized in vitro in terms of particle size, surface charges, particle recovery, encapsulation efficiency, and drug loading. Nanocapsule morphology, drug inclusion, structural properties, and crystallinity were investigated by scanning and transmission electron microscopes (SEM/TEM), energy-dispersive x-ray analysis, Fourier transform infrared spectroscopy, and x-ray diffraction. Initial screening of the antibacterial activities and the cytotoxicity of the nanocapsules were also conducted. Nanocapsules, as carried on ethanol/water solution, were delivered to demineralized dentin specimens connected to an ex vivo model setup simulating the pulpal pressure to study their infiltration, penetration depth, and retention inside the dentinal tubules by SEM/TEM. Nanocapsules were Ag labeled and delivered to demineralized dentin, followed by the application of a 2-step etch-and-rinse dentin adhesive. CHX-release profiles were characterized in vitro and ex vivo up to 25 d. Spherical nanocapsules were fabricated with a CHX core coated with a thin PCL shell. The blank nanocapsules exhibited the largest z-average diameter with negatively charged ζ-potential. With CHX incorporation, the nanocapsule size was decreased with a positive shift in ζ-potential. Nano-PCL/CHX at 125:50 showed the highest drug loading, antibacterial effect, and CHX release both in vitro and ex vivo. SEM and TEM revealed the deep penetration and retention of the CHX-loaded nanocapsules inside dentinal tubules and their ability to be gradually degraded to release CHX in vitro and ex vivo. Ag-labeled nanocapsules revealed the close association and even distribution of nanocapsules throughout the resin tag structure. This study demonstrated the potential of introducing this novel drug-delivery approach to demineralized dentin substrates and the resin-dentin interface with nanosized CHX-loaded nanocapsules through the microsized dentinal tubules.

Characterization of riboflavin-modified dentin collagen matrix

Crosslinking is considered a possible approach to increasing the mechanical and structural stability and biodegradation resistance of the dentin collagen matrix. The aim of this study was to investigate the mechanical and chemical variations and collagen degradation resistance associated with crosslinking of the dentin collagen matrix with UVA-activated riboflavin. Dentin collagen matrix specimens were treated with 0.1 and 1% riboflavin for 2 min and photo-activated with 7 mW/cm(2) UVA (368 nm) for 2 min. The structural change of the dentin collagen network with collagenase exposure was investigated by AFM and SEM at different time-points. The variations in surface/bulk mechanical properties and biodegradation resistance were characterized by nano-indentation, conventional mechanical testing, and hydroxyproline liberation at different time-points. Chemical changes associated with riboflavin/collagen-matrix interaction were analyzed by micro-Raman spectroscopy. UVA-activated riboflavin increased the mechanical properties, mechanical stability, and biodegradation resistance of the dentin collagen matrix. Higher collagen-network structural resistance against collagenolytic challenges was found with crosslinking. micro-Raman spectroscopy showed a strong dependency, in both intensity and wave-number, of certain Raman bands (1242-1667 cm(-1)) with crosslinking indicating the collagen/riboflavin interactions. UVA-activated riboflavin (1%) more efficiently crosslinked the dentin collagen matrix within a relatively clinically acceptable time-frame compared with 0.1% riboflavin.

Adapting to changes in molecular biosciences and technologies

Dental education, like any other educational programme in a research-intensive university environment, must be research led or at least research informed. In this context, as the research and knowledge base of dentistry lies in the biological and physical sciences, dental education must be led by advances in research in both these areas. There is no doubt that biotechnology and nanotechnology have, over the past 25 years, led research in both these areas. It is therefore logical to assume that this has also impacted on dental education. The aim of this paper is twofold; on one hand to examine the effects of biotechnology and nanotechnology and their implications for dental education and on the other to make recommendations for future developments in dental education led by research in biotechnology and nanotechnology. It is now generally accepted that dental education should be socially and culturally relevant and directed to the community it serves. In other words, there can be no universal approach and each dental school or indeed curriculum must apply the outcomes in their own social, cultural and community settings.

Clinical evaluation and microstructural analysis of a direct placement gallium restorative alloy

OBJECTIVES

The objective of this study was to assess the clinical performance of a direct placement gallium alloy sealed with an established dentine adhesive system. In addition, microanalysis of a few gallium restorations that failed in clinical service was performed. Clinical factors such as pulpal sensitivity, fracture of the restoration and of the tooth, marginal deterioration, and tarnish were assessed.

METHODS

Sixty-five restorations of Galloy and 62 of Tytin (49 and 51 Class II restorations, respectively) were placed according to a predetermined scheme for randomisation in 37 patients by two operators using rubber dam isolation. For the Galloy restorations, the enamel and dentine were etched, and then sealed with PAAMA 2 dentine adhesive according to the manufacturer's instructions. After carving, PAAMA 2 was applied to the Galloy and light-cured. Cavity preparations for Tytin received no adhesive sealer. All restorations were polished at least 24 h post-operatively. Microstructural analysis of retrieved fragments of failed restorations was conducted using electron probe microanalysis.

RESULTS

At 1 year, only one Tytin restoration was found to have failed due to an isthmus fracture. The remaining restorations of Tytin were intact with no reported sensitivity. Of the 65 Galloy restorations placed, 28 had to be removed, including restorations in teeth, which were symptomatic, non-vital and/or fractured, and teeth with fractured restorations. Tarnish was present on many of the Galloy restorations. Retrieved fragments of failed Galloy restorations exhibited a dark surface at the pulpal wall interface and small cracks were observed in that surface. Internal cracks and extensive corrosion was observed using the microprobe. Gallium oxides and chlorides were identified as the predominant corrosion products.

CONCLUSIONS

The gallium alloy, Galloy, sealed with PAAMA 2 dentine adhesive system demonstrated a high clinical failure rate.

The influence of finishing time on the marginal seal of a resin-modified glass-ionomer and polyacid-modified resin composite

The aim of this study was to compare the effect of immediate and delayed finishing on the microleakage of encapsulated resin-modified glass-ionomer, Fuji II LC and a polyacid-modified resin composite, Dyract compomer at both the enamel and dentine margins. Standardized Class V cavities were prepared along the cemento-enamel junction on buccal and palatal surfaces of 24 freshly extracted non-carious premolars. Equal numbers of buccal and palatal cavities in each group were restored with Fuji II LC and Dyract compomer following the manufacturer's instructions. The groups with delayed finishing were restored 1 week earlier, stored in saline at 37 degrees C and finished on the same day as the groups with immediate finishing. The specimens were then thermocycled 500 times and subjected to dye penetration testing. The results showed that both materials leaked more at the dentine than enamel margins for both regimes of finishing methods. There was no statistical difference in the microleakage of Dyract finished immediately or later at enamel and dentine margins and Fuji II LC finished immediately or later in dentine. However, a statistical difference existed between the microleakage in Fuji II LC finished immediately and later in enamel.

Perceived masticatory function among elderly people

This study investigated the status and associations of perceived chewing ability of a group of 891 elderly people, aged 55-91 years (average age 66 years). The majority of subjects (69%) considered that they could chew well. Only 9% reported poor chewing ability. This judgement was not associated with age. More men (11%) than women (6%) had reported poor chewing ability. Subjects with better perceived general and craniomandibular health reported better chewing ability. However, although related to permanent tooth loss, the perception of chewing ability was not seemingly associated with prosthetic rehabilitation. All elderly subjects with complete dental arches had no complaints of perceived chewing difficulty. Freedom from symptoms of craniomandibular pain when chewing, bilateral chewing activity and a wide choice of food range or textures were associated with favourably perceived chewing ability. This study identifies several suitable criteria for judging masticatory function and suggests that these may be used to complement chewing ability as an alternative measure of masticatory performance. These criteria are applicable to the elderly person, in particular, and warrant adequate clinical application.

Direct tooth-colored materials for noncarious lesions: a 3-year clinical report

One hundred fifty-nine noncarious cervical lesions were restored with glass-ionomer cement, resin composite used with a dentinal bonding agent, or the laminate (sandwich) restoration, which combines both these materials. These restorations were evaluated at baseline, 1 year, and 3 years for color match, cavosurface marginal discoloration, anatomic form, marginal adaptation, and retention. There was a general deterioration of the restorations with time. Lesions restored with resin composite and a dentinal bonding agent exhibited the highest percentage of lost restorations.

Clinical evaluation of tooth-colored materials in cervical lesions

PURPOSE

To determine the 18-month clinical performance of four tooth-colored restoratives in non-carious cervical lesions.

MATERIALS AND METHODS

Buccal abrasion lesions in 83 teeth were restored with each of the following materials: Fuji Cap II, Fuji II LC, APH/Universal Bond 3, Lite Fil II A/Imperva Bond. Baseline and an 18-month recall was carried out using the Ryge (USPHS) method for retention, color match, marginal adaptation, cavosurface marginal discoloration, anatomic form and secondary caries.

RESULTS

The USPHS results (% alfa) for the four products were, respectively: color match (9%, 48%, 57%, 55%), marginal discoloration (71%, 76%, 52%, 50%), marginal adaptation (24%, 24%, 33%, 15%), anatomic form (67%, 86%, 95%, 45%) and retention (100%, 95%, 100%, 65%). Results indicated that (1) Fuji Cap II exhibited a poor color match at baseline (2) Color matching of Fuji II LC was comparable to the resin composites and (3) seven Lite Fil II/Imperva Bond restorations (35%) were dislodged after 1 1/2 years.

Symptoms of craniomandibular disorder among elderly people

This study investigated the subjective symptoms of craniomandibular disorder and the restriction in maximal mandibular opening of 891 elderly Singaporean citizens. A distribution of 22% of subjects (20% of the women and 26% of the men) reported subjective symptoms of craniomandibular disorders. The most common single symptom reported was occasional to frequent clicking sounds from the temporomandibular joints (in 15% of subjects). The other single symptoms were reported only occasionally in 2-6% of subjects. Nineteen per cent of the subjects had some restriction in maximal interincisal opening (30-39 mm) and about 1% of subjects were severely restricted in maximal opening (less than 30 mm). Subjectively evaluated limitation of wide mandibular opening was recorded for only 2% of the subjects. Background factors included general musculo-skeletal problems (54%), perceived fair to poor general health (29%), headaches (33%), work-related stress (24%), oral parafunctional clenching (4%) and grinding activity (4%). This paper confirms earlier reports that the subjective signs and symptoms of craniomandibular disorder tend to diminish in elderly people.

The effect of dentin bonding agents on the microleakage of porcelain veneers

OBJECTIVES

This in vitro study was conducted to investigate the effect of dentin bonding agents on the microleakage of porcelain veneers cemented on dentin margins.

METHODS

Forty human premolars were prepared on both the buccal and palatal surfaces. Each half was randomly assigned to eight groups. The veneer preparation of one group was cut entirely within enamel, to serve as controls. The remaining groups had cervical margins extending 1 mm beyond the cemento-enamel junction. Six dentin bonding agents were tested. The specimens were subjected to thermocycling and evaluated for marginal leakage using a silver nitrate stain technique. After sectioning, the extent of microleakage was measured at four interfaces: (1) incisal porcelain-composite; (2) incisal tooth-composite; (3) cervical porcelain-composite; and (4) cervical tooth-composite.

RESULTS

Statistical analysis showed that the cervical tooth-composite interface had a significantly higher leakage value (p < 0.05) than the other three interfaces when the cervical margins were in dentin.

SIGNIFICANCE

The dentin bonding agents tested did not significantly reduce the marginal leakage of the porcelain veneers cemented on dentin margins.

A retrospective clinical study of endodontically treated mandibular incisors in a selected Chinese population

Clinical studies of incidences of the number of canals in human teeth should correlate with the percentages obtained in laboratory samples. In this study the incidence of two canals in the mandibular incisors was compared with figures obtained from in vitro extracted teeth, as well as from one clinical study. A very low percentage was obtained from the examination of clinical records, and this could be due to racial differences in the samples examined.

A survey of approximal root concavities in an ethnic Chinese population

Eight hundred and forty teeth were surveyed, 60 approximal surfaces for each tooth type being studied. Approximal root concavities were completely absent in maxillary central incisors, in contrast with mandibular central incisors of which 73% had concavities on mesial surfaces and 93% on distal surfaces. Similarly, a markedly higher prevalence was found for mandibular lateral incisors and canines. However, mandibular first and second molars had fewer approximal concavities than their maxillary counterparts. In maxillary teeth, concavities were more frequent on distal surfaces, while for mandibular teeth no definite pattern was seen. In both maxillary and mandibular teeth, approximal concavities often started in enamel, extending down to the root surface. There were differences in the approximal root topography of Chinese teeth in comparison with other populations.

Position of the mental foramen in Singaporean Malays and Indians

The position of the mental foramen of the local Malays and Indians in Singapore was determined from a series of orthopantomograms. The most frequent location does not conform to the position cited in many anatomy, surgery, and dental anesthesia texts as being below and between the apices of the lower premolars. This data has implications in the teaching and practice of dental anesthesia. In both these races, the median location is just below the second premolar.

The geriatric dental patient

The life expectancy of our citizens has increased due to better living conditions and medical care. This poses new challenges to dental surgeons because geriatric dental patients have different needs brought on by ageing. Tooth loss, periodontal disease, alveolar bone resorption, mucosal changes, edentulism are just some of the problems faced by the elderly. Recognition of the dental needs of this special category of the population compels us to bear the responsibility of treating them now and in the future. We require a gerodontology programme that emphasizes prevention, maintenance of the oral health and understanding of their psychological status.

The use of ultrasonic endodontic instrumentation in the re-treatment of a paste-filled endodontic tooth

A technique using ultrasonic endodontic instruments in re-treating hard-paste--filled root canals is presented. The technique is time-consuming but may eliminate the necessity for a surgical approach in the re-treatment of paste-filled teeth.