Shivaughn Marchan

The prevalence and severity of non-carious cervical lesions in a group of patients attending a university hospital in Trinidad

Non-carious cervical lesions (NCCLs) are often encountered in clinical practice and their aetiology attributed to toothbrush abrasion, erosion and tooth flexure. This paper aims to determine the prevalence and severity of NCCLs in a sample of patients attending a university clinic in Trinidad and to investigate the relationship with medical and dental histories, oral hygiene practices, dietary habits and occlusion. Data were collected via a questionnaire and clinical examination. Odds ratios were used to determine the association of the presence of lesions and the factors examined. One hundred and fifty-six patients with a mean age of 40.6 years were examined of whom 62.2% had one or more NCCLs. Forty five per cent of the lesions were sensitive to compressed air. Younger age groups had a significantly lower correlation with the presence of NCCLs than older age groups. Other significant factors included patients who reported heartburn, gastric reflux, headaches, bruxism, sensitive teeth and swimming or had a history of broken restorations in the last year. There was also significant correlation of NCCLs in patients who brushed more than once a day or used a medium or hard toothbrush. Patients with vegetarian diets and those who reported consuming citrus fruits, soft drinks, alcohol, yoghurt and vitamin C drinks were associated with the presence of lesions. Significant associations were also found in patients with group function, faceting, clicking joints or those who wore occlusal splints.

Effect of Reduced Exposure Times on the Microhardness of Nanocomposites Polymerized by QTH and Second-generation LED Curing Lights

This study investigated the effectiveness of polymerization of various curing regimes on five nanocomposite restorative materials—Z350, Grandio, Clearfil Majesty Esthetic, Ice and Tetric EvoCeram—by utilizing microhardness measurements. Five (n=5) disc-shaped specimens of each material were subjected to one of three curing regimes: curing with a halogen light for 20 seconds, curing with an LED light for 20 seconds and curing with an LED light for 10 seconds. Immediately following curing, hardness measurements were made with a Vickers indenter at five different locations on both the top and bottom surfaces of each disc. The mean for each surface was calculated. Data were analyzed using a one-way ANOVA and post-hoc Tukey HSD (α=0.05). The results demonstrated that among the Z350 composite samples, top and bottom microhardness values showed no statistical differences when cured with the halogen 20 second or LED 20 second regimes (p>0.05). Comparison of the top and bottom values of discs cured with the LED 10 second regime demonstrated significant differences (p<0.0001). Grandio samples cured with the halogen 20 second regime showed no statistical differences between top and bottom microhardness values (p>0.05); however, the bottom values of Grandio discs cured with the LED 20 second and 10 second regimes were significantly lower when compared with top surface values (p=0.001 and p<0.0001, respectively). Clearfil Majesty Esthetic, Ice and Tetric Evo Ceram samples cured with the halogen 20 second regime produced significantly lower bottom microhardness values, while both LED regimes produced top and bottom surfaces that were statistically comparable. The conclusion may be drawn that LED 10 second curing regimes were insufficient to cure Z350 and Grandio, while they were adequate for curing Clearfil Majesty Esthetic, Ice and Tetric EvoCeram.

In vitro evaluation of the retention of zirconia-based ceramic posts luted with glass ionomer and resin cements

The retention of zirconia-based ceramic posts (CosmoPost system) luted with glass ionomer and resin cements was evaluated. Thirty-two extracted, caries-free, unrestored teeth were selected and stored in chlorhexidine and water solution. The teeth were endodontically treated and randomly assigned to two groups (n=16). Each tooth was decoronated and prepared to a depth of 10.0 mm from root surface to receive a 1.4 mm diameter zirconium dioxide post. Each group had posts cemented with either glass ionomer cement (Fuji I) or resin cement (Variolink II). The post/teeth specimens were embedded in resin blocks and subjected to tensile testing. The tensile force required to dislodge the cemented posts in a tensile testing machine was recorded. The mean stress values of both groups were analyzed for statistical differences using ANOVA and Students t-test. Significance level was set at 5%. Mean peak forces at failure (N) and standard deviation for the tested cements were the following: Fuji I = 121.8 (+/-17.4) and Variolink II = 228.1 (+/-36.8). Posts luted with the resin cement presented statistically significant higher tensile bond strength than those retained with glass ionomer (p<0.05). It may be concluded that zirconia posts cemented with resin-based cement (Variolink II) failed at statistically significant higher values compared to those cemented with glass ionomer cement (Fuji I). Regardless of the cement type, the posts failed adhesively at the cement/post interface when subjected to a tensile force.

Cusp Fracture Resistance of Maxillary Premolars Restored with the Bonded Amalgam Technique Using Various Luting Agents

Objective. This in vitro study uses measurements of fracture resistance to compare maxillary premolars restored with the bonded amalgam technique using a new resin luting cement, glass ionomer, and resin-modified glass ionomer as the bonding agents. Materials. Eighty-five sound maxillary premolars were selected and randomly assigned to one of five test groups of 17 teeth each. One group of intact teeth served as the control. The remaining groups were prepared to a standard cavity form relative to the dimensions of the overall tooth and restored with amalgam alone or a bonded amalgam using one of three luting agents: RelyX Arc (a new resin luting cement), RelyX luting (a resin-modified glass ionomer), or Ketac-Cem μ (a glass ionomer) as the bonding agents. Each tooth was then subjected to compressive testing until catastrophic failure occurred. The mean loads at failure of each group were statistically compared using ANOVA with a post hoc Bonferroni test. Results. It was found that regardless of the luting cement used for the amalgam bonding technique, there was little effect on the fracture resistance of teeth. Conclusion. Cusp fracture resistance of premolars prepared with conservative MOD cavity preparations is not improved by using an amalgam-bonding technique compared to similar cavities restored with amalgam alone.

Surface Properties of Dental Nanocomposites After Finishing WithRigid Rotary Instruments

This study evaluated the surface characteristics of three nanoparticle resin composites (Z350, Heritage 7 Nanohybrid, and Ice) using profilometry and scanning electronic microscopy (SEM) after subjecting them to sequential finishing procedures using rigid rotary instruments. Fifteen 8 mm × 8 mm × 2 mm specimens were fabricated for each tested composite and subjected to one of the following finishing regimens: finishing with green stones followed by white stones, finishing with 45-μm diamond followed by 15-μm diamond, finishing with a 12-fluted carbide followed by a 20-fluted carbide. After finishing, the surfaces were subjected to profilometric testing. Eight parallel tracings were used to scan the finished surface of each specimen. For each recorded profile, the average roughness (Ra) and extreme value descriptor (Rmax) were recorded. On completion of the profilometric testing, two specimens from each group were randomly selected for qualitative assessment by SEM. Profilometric data was analyzed using a one-way analysis of variance and post hoc Scheffe tests. The results demonstrated that the three control groups of the tested nanocomposites behaved as a coherent group with respect to surface roughness. With the exception of the nanohybrid Heritage 7 finished with the carbide instruments, all composites showed an increase in surface roughness. The Z350 and Ice finished with the carbide finishing instruments showed no statistically significant increase in Ra, but both of these composites showed significantly rougher surfaces when finished with diamonds compared with controls. The nanohybrids Ice and Heritage 7 demonstrated significantly higher roughness in terms of Rmax when finished with stones. The SEM correlated well with roughness measurements. The conclusion may be drawn that diamonds and stones produce unacceptable surfaces in terms of roughness on the tested nanocomposites whereas finishing carbides produce acceptable surfaces.