Effect of NaPi-mediated phosphate transport on intracellular pH

Extracellular pH has been shown previously to influence transport via type-II Na+/phosphate (NaPi) transporters by modifying the affinity of the carrier for Na+ and by altering the availability of divalent and monovalent phosphate. As the transport of monovalent phosphate would be expected to acidify, and that of divalent phosphate to alkalinize the cell interior, the effect of phosphate transport on cytosolic pH was studied using ion selective microelectrodes in Xenopus oocytes expressing NaPi-3 or NaPi-5. At an alkaline extracellular pH (pHe) of 8.0, addition of phosphate elicited a strong inward current, depolarization of the cell membrane and cytosolic alkalinization. At pHe 6.0 the phosphate-induced inward current and depolarization were reduced and the alkalinization completely abolished. In conclusion, at alkaline pHe phosphate transport is enhanced and the transport of divalent phosphate prevails. At pHe 6.0, phosphate transport is attenuated and is accomplished by transport of both divalent and monovalent phosphate.

Comparison of resin-bonded prosthesis groove parallelism with the use of four tooth preparation methods

STATEMENT OF PROBLEM

A precise preparation is required to develop resistance form resulting in mechanical stability of the framework for resin-bonded prostheses (RBPs).

PURPOSE

The effects of 4 methods of tooth preparation (freehand, guiding pin, extraoral parallelometer, and intraoral parallelometer) on the deviation of proximal grooves from a preestablished path of insertion (guide planes) were investigated under clinical conditions.

MATERIAL AND METHODS

Tooth preparation of proximal grooves was performed by 32 dentists on resin substitutes of posterior segments intraorally with a single test patient. A Latin-square randomized cross-over design was selected as the experimental design.

RESULTS

The significant least angular deviation of proximal grooves from path of insertion was achieved with an intraoral parallelometer (mean +/- SD 3.15 +/- 1.67 degrees). Compared with freehand tooth preparations (4.37 +/- 2. 11 degrees), neither use of a guiding pin (4.10 +/- 1.62 degrees) nor an extraoral parallelometer (5.06 +/- 2.33 degrees) improved the results.

CONCLUSION

Divergence of guiding grooves from path of insertion was reduced with the use of an intra-oral parallelometer. This should improve mechanical stability of posterior RBPs.

A new approach in restorative treatment of external root resorption. A case report

This case report describes the treatment of an external root resorption with extensive loss of tooth structure and bone at the labial surface of an upper left central incisor. The area of bone loss and root resorption was surgically exposed and an impression was taken using curing silicone. An individual ceramic insert was fabricated, allowing endodontic retreatment through an artificial root canal. The insert was incorporated using a dentin bonding system and a dual curing luting composite. Following endodontic retreatment and internal bleaching, a ceramic veneer was bonded to the tooth to obtain good esthetics and to improve stability. Twenty months after surgical treatment no further root resorption could be detected radiographically. A shallow residual pocket but no bleeding on probing was found.

Salivary anti-hsp65 antibodies as a diagnostic marker for gingivitis and a possible link to atherosclerosis

Levels of specific salivary IgA antibodies against mycobacterial heat shock protein (hsp) 65 are significantly increased in patients with gingivitis when compared to clinically healthy subjects. The process of identifying the hsp65 epitopes recognized by the salivary antibodies, binding to overlapping 15-mer-hsp65 peptides, was assessed. Time-resolved fluorescence immunoassays using 15-mer overlapping peptides spanning the whole hsp65 molecule revealed six distinct sequences recognized by anti-hsp65 IgA antibodies. Due to the high degree of sequence homology between mycobacterial hsp65, cognates of the hsp60 family of oral bacterial flora and human hsp60, these six epitopes may serve as cross-reactive autoantigens in certain circumstances in vivo and could incite an autoimmune response that contributes to the initiation of gingivitis.

The effect of sodium fluoride at prophylactic and toxic doses on renal structure and function in the isolated perfused rat kidney

To assess the renal effects of fluoride, isolated rat kidneys were perfused in single pass mode for 120 min. Five, 15 and 50, as well as 150, 500 and 1500 mumol NaF were administered 60, 80 and 100 min after starting the perfusion, respectively. Kidneys were perfused with constant pressure (100 mmHg). The perfusate consisted of a substrate supplemented Ringer solution containing hydroxy ethyl starch (HES) to produce isoncotic conditions. Concentrations below 500 mumol/l NaF did not induce major changes in the main parameters of renal function. Only upon admixture of the highest concentration of 1500 mumol/l NaF severe changes in renal function could be observed, resulting in complete anuria and a drastic reduction of renal perfusion to 5% of control, associated with a cessation of glomerular filtration. Due to the lack in tubular load, tubular reabsorptive processes inevitably declined to zero. The morphological analysis of kidneys exhibited to 500 mumol/l NaF revealed the occurrence of vesicular material within the urinary space. These vesicles could electron microscopically be identified as membrane enclosed material of podocytic origin. The interstitium was widened. Upon admixture of 1500 mumol/l NaF, kidneys responded with a decrease of the interstitial space. Moreover, epithelial cell swelling, hydropic degeneration of all proximal and distal tubular segments, bleb formation and intraluminal casts were observed frequently. Glomerular capillaries were filled with fine precipitates and their endothelium was severely damaged. The results of our studies in the isolated perfused rat kidney (IPRK) model clearly demonstrate a direct dose dependent acute nephrotoxic effect of NaF only for extremely high doses, which, however, may be reached in human cases of severe fluoride intoxication. On the contrary, for low fluoride doses, especially for those concentrations occurring in human plasma upon cariesprophylactic intake of fluorides, no signs of direct acute nephrotoxic action could be observed in the IPRK model.

Caries susceptibility and renal excretion of calcium

Clearance studies were performed for 2 days in two groups of age-matched young female volunteers: those with low caries prevalence and those with high caries prevalence. Both groups were kept on a low-calcium diet for 1 week and received 0.5 g calcium at the beginning of the second day. In both groups, glomerular filtration rate, urinary flow rate and renal excretions of sodium, calcium, and phosphate were subject to significant circadian variations. In both groups the administration of calcium led to a significant increase in renal excretion of sodium and calcium and a significant decrease in that of phosphate. On the first day, calcium excretion was significantly greater in those with low caries prevalence than in those with high caries prevalence, pointing to altered calcium homeostasis in this group.

[The Pontic. Preventive consideration of pontic design]

When fixed partial dentures are provided for edentulous areas of the alveolar ridge, the previously impaired masticatory and phonetic functions as well as esthetics are restored immediately; in the long run, the restoration helps to stabilize the occlusion, thus maintaining the integrity of the temporomandibular joints and the neuromuscular system. The reabsorption of connective tissues following the loss of teeth as well as the changes in the dimensions of edentulous areas that occur over time will have to be taken into account in that the basic shape of the tooth or teeth to be replaced needs to be modified. Pontics usually present a larger surface than natural teeth; on this surface, plaque may accumulate. The self-cleaning mechanisms are ineffective on the surfaces facing the adjacent teeth or the tissues of the alveolar ridge. For this reason, the pontics and their flexible or rigid connectors to the abutments must be considered the weakest parts of the restoration. The long-term success of the restoration, once periodontal treatment and optimum prosthodontic care have been provided, depends on whether considerations of periodontal prevention played a role in the design of the restoration and on postinsertion periodontal care.