ABSTRACT
BACKGROUND: Modern dental composite restorations are wholly dependent on the use of Visible Light Curing devices. The characteristics of these devices may influence the quality of composite resin restorations. OBJECTIVE: To determine the characteristics of light curing units (LCUs) in dental clinics in Nairobi and their effect on light intensity output, depth of cure (DOC) and surface micro-hardness (SMH) of dental resin composite. DESIGN: Laboratory based, cross-sectional analytical study. SETTING: Public and private dental clinics in Nairobi, Kenya. SUBJECTS: Eighty three LCUs which were in use in private and public dental health facilities in Nairobi, Kenya and resin composite specimens. RESULTS: Of the 83 LCUs studied, 43 (51.8%) were Light Emitting Diodes (LEDs) and 39(47.0%) were Quartz-Tungsten-Halogen (QTH) and 1 (1.2%) was Plasma Arc Curing (PAC) light. Mean light intensity for QTH and LED lights was 526.59 mW/cm2 and 493.67 mW/cm2 respectively (p=0.574), while the mean DOC for QTH lights was 1.71 mm and LED was 1.67 mm (p=0.690). Mean Vickers Hardness Number (VHN) for LED was 57.44 and for QTH was 44.14 (p=0.713). Mean light intensity for LCUs < or = 5 years was 596.03 mW/cm2 and 363.17 mW/cm2 for units > 5 years old (p=0.024). The mean DOC for the two age groups was 1.74 mm and 1.57 mm respectively (p=0.073). For SMH, the < or = 5 years and >5 years age groups gave a mean VHN of 58.81 and 51.46 respectively (p=0.1). On maintenance history, the frequency of routine inspection, duration since the last repair/replacement of a part or other maintenance activity and the nature of the last maintenance activity were determined and were not found to have influenced the light intensity, DOC and SMH. CONCLUSION: The LCU age has a statistically significant influence on its light intensity (p=0.024) while the type and maintenance history have no significant influence on its light intensity and composite DOC and SMH (p=0.574, p=0.690, p=0.713 respectively).
Subject(s)
Acrylic Resins/radiation effects , Composite Resins/radiation effects , Curing Lights, Dental , Polyurethanes/radiation effects , Cross-Sectional Studies , Equipment Design , Hardness , Humans , Kenya , Surface PropertiesABSTRACT
OBJECTIVE: To determine the light intensity emitted by light curing units (LCUs) and its effect on the cure characteristics of composites polymerised with it. DESIGN: A laboratory based cross sectional study. SETTING: Public and private dental clinics in Nairobi, Kenya. RESULTS: Thirty five (42.17%) LCUs produced light of intensity ≤300mWcm⻲ while 43 (51.8%) LCUs had their intensities between 300 and 1200mWcm⻲. Mean DOC and surface hardness for the 0-300mWcm⻲ LCUs was 1.34mm and 46.60VHN respectively. The mean DOC increased steadily from the lowest intensity group (1.34mm) to the 1200-15OOmWcm⻲ group (2.32 mm) and then declined to 1.98mm for the 1500-1800mWcm⻲ group. Statistical analysis showed significant differences in the mean DOC (p=0.000) and surface micro-hardness (p=0.002) for the different intensity groups. CONCLUSION: Light intensity output of LCUs has a significant influence on the cure characteristics of dental composites with both DOC and surface micro-hardness increasing with increase in light intensity up to 1500mWcm⻲.
Subject(s)
Composite Resins/radiation effects , Curing Lights, Dental , Hardness , Cross-Sectional Studies , Dental Equipment , Humans , Radiation DosageABSTRACT
OBJECTIVES: The aim was to study dimensional time-dependence of resin/ionomer formulations from 5 min age to one month and to separate out the intrinsic setting shrinkage and hygroscopic expansion effects, by using non-aqueous and aqueous storage media, respectively. METHODS: Materials studied included: A: resin-, B: metal- and C: polyphosphonate-modified glass-ionomer cements [GICs]; and controls of D: poly-acid modified composite [compomer]; and E: resin-composite. Separate specimen groups (n = 5) were stored in different storage-media: (i) silicone fluid; (ii) de-ionized water. Experiments were repeated at 23 and 37 degrees C. Volumetric changes of specimens (4 mm diameter x 6 mm height) were obtained via accurate mass measurements (to 10(-4) g), using Archimedes principle, with silicone or water also used as the Archimedean fluid. These measurements were made periodically over a 30 day period, post fabrication. RESULTS: In silicone at 23 degrees C, all materials underwent further gradual intrinsic shrinkage (after 5 min from mix). This was highly significant (p < 0.05) for the RM-GIC (A). At 37 degrees C, however the RM-GIC expanded, indicating that its cure is temperature-sensitive. In water, at 23 and 37 degrees C, the shrinkage was either partially offset (materials C, D, E), or replaced by appreciable expansions (materials A and B). Differences between RM-GIC (A) and MM-GIC (B) were significant (p < 0.05). SIGNIFICANCE: The deployment of dual storage media made an important contribution to the separate analysis of the volumetric changes due to the on-going setting chemistry in these systems and the time-dependent effects of an aqueous environment.
Subject(s)
Dental Restoration, Permanent , Glass Ionomer Cements/chemistry , Silicon Dioxide , Zirconium , Analysis of Variance , Chemical Phenomena , Chemistry, Physical , Compomers/chemistry , Composite Resins/chemistry , Humans , Hydrogen-Ion Concentration , Materials Testing , Metals/chemistry , Methacrylates/chemistry , Organophosphates/chemistry , Organophosphorus Compounds/chemistry , Resin Cements/chemistry , Resins, Synthetic/chemistry , Silicates/chemistry , Silicones/chemistry , Statistics as Topic , Surface Properties , Temperature , Time Factors , Water/chemistryABSTRACT
A survey of 272 University of Nairobi undergraduate students was undertaken to assess their dental chairside experience and what reasons they gave for failing to seek dental treatment. Most respondents considered dental treatment uncomfortable and painful. The cost of treatment and fear arising from information given by other dental patients were important reasons that kept the respondents from visiting a dental clinic. This paper reveals the need for the dental profession to play a greater role in reducing costs of treatment and odontophobia.
Subject(s)
Dental Anxiety/psychology , Dental Care/economics , Dental Care/psychology , Patient Acceptance of Health Care , Students/psychology , Universities , Female , Health Care Costs , Humans , Kenya , Male , Surveys and Questionnaires , Urban HealthABSTRACT
The objective of this study was to determine the knowledge and attitude of Nairobi University students towards dental health care in Kenya. A self administered questionnaire given to 400 students in person who responded and handed them over immediately. The students had a mean age of 22.4 years, 45.3% were males and 54.5% were females. Extractions, restorations and replacement of teeth were known to majority of the students. However, almost half of the students preferred extraction to restoration and 49.2% considered restoration of deciduous teeth unnecessary. 79% indicated that they would undergo scaling. It is therefore recommended that an effective mode of transmitting positive information about various dental treatment modalities be established.
