The effect of periodontal therapy on uncontrolled type 2 diabetes mellitus in older subjects.

OBJECTIVE: The purpose of this study was to examine the effect of periodontal therapy on glycemic control in older type 2 diabetic patients. METHODS: Fifty-two diabetic patients, age 55-80 years (mean age = 61 years), with glycated hemoglobin (HbA1c) 7.5-11.0% (mean +/- s.d. = 8.98 +/- 0.88) and severe periodontitis were included in the present study. The treatment group received mechanical periodontal treatment combined with systemic doxycycline, 100 mg day(-1) for 14 days. The control group received neither periodontal treatment nor systemic doxycycline. Clinical periodontal parameters, fasting plasma glucose (FPG), and HbA1c levels were measures at baseline and 3 months. RESULTS: Periodontal treatment significantly improved periodontal status of the treatment group (P < 0.05), however the reduction in the level of FPG and HbA1c did not reach significance. In the control group, no significant changes in clinical periodontal parameters, FPG and HbA1c levels were observed, except for significant increase in attachment loss (P < 0.05). Comparing the two groups, although the 3-month level of HbA1c of the treatment group was lower than that of the control group, the difference did not reach significance. CONCLUSIONS: The results of the present study indicate that the periodontal condition of older Thais with uncontrolled diabetes is: (a) significantly improved 3 months after mechanical periodontal therapy with adjunctive systemic antimicrobial treatment, and (b) rapidly deteriorating without periodontal treatment. The effect of periodontal therapy on the glycemic control of older uncontrolled diabetics will require further studies that will have to include much larger sample sizes.

Long-term flexural strengths of resin-modified glass-ionomer cements.

The use of resin-modified glass-ionomer cements (RMGICs) in restorative dentistry has expanded since their introduction about seven years ago. These materials have been shown to possess superior initial mechanical properties to those of the conventional glass-ionomer cements. However, studies on the strength of RMGICs as a function of storage time are limited. This in vitro study investigated the effects of long-term storage of RMGICs in two storage media, distilled water and artificial saliva, at 37 degrees C on their four-point and bi-axial flexural stengths for a period up to 1 yr. All materials, except Fuji Lining LC, were weak at 5 min after light exposure but reached the maximum strengths within 7 d. Subsequently, there was a small decline in strength. Generally, the specimens aged in distilled water and artificial saliva had similar strength values. The bi-axial strengths of RMGICs were significantly greater than those obtained from the four-point flexure tests by a factor of approximately three. More variations in strengths of RMGICs with time were also observed from the four-point flexure test than from the bi-axial flexure test.

Long-term surface micro-hardness of resin-modified glass ionomers.

OBJECTIVES: The presence of a resin component in resin-modified glass-ionomer cements (RMGICs) results in considerable water sorption which may affect the surface hardness of the materials. This study investigated the effect of long-term storage in aqueous solutions on the surface hardness of RMGICs. METHODS: The surface micro-hardness of four RMGICs stored in either distilled water or artificial saliva was measured using the Wallace microindentation tester at regular time intervals up to 360 days. RESULTS: There was a substantial increase in hardness during the first day of storage when RMGICs were kept in distilled water. All RMGICs except one liner/base material reached their maximum hardness within 7 days and maintained their hardness for up to 1 year. RMGICs stored in artificial saliva were relatively softer and showed a decrease in surface hardness with time. CONCLUSIONS: The post-hardening reaction overcame the plasticising effect of water when RMGICs were stored in distilled water. However, progressive and high water uptake of specimens stored in artificial saliva resulted in a decrease in their surface hardness.

Water sorption characteristics of resin-modified glass-ionomer cements.

When restorative materials take up water, their dimensions and structural integrity may be affected. This study determined, using gravimetric measurements, the water sorption characteristics of four resin-modified glass-ionomer cements (RMGICs) immersed in either distilled water or artificial saliva. The dimensional changes on water storage were also determined. The RMGICs exhibited differing characteristics as they absorbed water. Percentage water uptake and solubility of the liner/base RMGICs were significantly greater than those of the restoratives. Higher rates of water uptake, i.e. higher values of sorption diffusion coefficients, were found in the materials from one manufacturer. The desorption diffusion coefficients of the four cements were not significantly different from one another, but were significantly higher than the sorption coefficients, indicating rapid water loss from the desiccated cements. All the cements expanded on immersion in water and contracted during desorption. Greater weight increase and greater volumetric expansion were observed on long-term storage in artificial saliva than in distilled water.

Factors contributing to the temperature rise during polymerization of resin-modified glass-ionomer cements.

Part of the setting reaction of a resin-modified glass-ionomer cement (RMGIC) is a photoinitiated polymerization. As a result of the polymerization exotherm, the temperature of the cement may rise during setting. This study investigated the temperature rise for two liner/base- and two restorative-type RMGICs. The effects of factors such as specimen thickness, exposure time and environment temperature were investigated. The thermal diffusivity of the cements was also evaluated. Temperatures were measured using a thermocouple embedded in the centre of 6-mm diameter specimen discs of 1, 2, or 3 mm thickness. The exposure times used to cure the specimens varied from 15 to 60 s. The test were carried out at either 25 or 37 degrees C. The temperature rises attributable to the polymerization reaction ranged from 11 to 26 degrees C for the liner/base cements and from 8 to 17 degrees C for the restorative cements. Increasing the specimen thickness reduced the temperature rise only when inadequate exposure times were used. Raising the environmental temperature resulted in a smaller temperature rise. The thermal diffusivities were determined from cylindrical specimens. These ranged from 1.9 x 10(-3) to 2.5 x 10(-3) cm2 s-1, the lining cements showing lower values than the restorative materials.

Temperature rise in ion-leachable cements during setting reaction.

Resin-modified ion-leachable cements have been developed for use as aesthetic restorative materials. Their apparent improved physical and handling properties can make them more attractive for use than conventional glass-ionomers. However, they contain monomers which are known to contract on polymerization and produce a polymerization exotherm. This study evaluated the temperature rise during setting and the rate of dimensional change of several ion-leachable materials. The resin-modified ion-leachable cements demonstrated greater temperature rises and higher rates of contraction than conventional materials. Generally, the behaviour of these resin-modified materials was similar to that of composite resins. However, some resin-modified cements produced a temperature rise of up to 20 degrees C during polymerization which was greater than that of the composite resin. This temperature rise must be taken into account when using the materials in direct contact with dentine in deep cavities without pulp protection. Longer irradiation time than the recommended 20 s did not significantly increase the maximum temperature rise but slightly extended the time before the temperature started to decline. The temperature of the environment had a significant effect on the rate of dimensional change in some materials. The rate of polymerization contraction of light-activated cements was directly related to the observed temperature rise.

Influence of humidity on dimensional stability of a range of ion-leachable cements.

The dimensional changes of a variety of dental restorative materials, occurring during and after setting, were investigated. The materials were tested under four different environmental conditions: 25 degrees C at laboratory humidity, 25 degrees C at 100% humidity, 37 degrees C at laboratory humidity and 37 degrees C at 100% humidity. Two materials setting by an acid-base reaction were also examined when protected with both a conventional varnish and a low-viscosity light-curable resin. The dimensional changes were recorded continuously using linear variable displacement transducers (LVDTs) over periods of up to 2 h. The materials investigated showed varying magnitudes of dimensional change. The shrinkage of conventional glass-ionomer cements (Fuji II and Opusfil) were the highest at 37 degrees C in air. This was attributed to the highest rate of water loss in the most desiccating environment. The shrinkage observed for the materials which set, even only in part, by a polymerization reaction will probably be due to the water loss and/or polymerization shrinkage. Exposure of these materials to a high-humidity environment reduced the shrinkage because of the swelling associated with water absorption. Application of the varnish and the protective resin over the cement surfaces also reduced shrinkage in Fuji II due to prevention of water exchange. The apparatus used in this study provided a simple and reliable method for measuring linear dimensional change. Data obtained in this study were comparable, where appropriate, to the values found in the literature.