Erosive loss of tooth substance is dependent on enamel surface structure and presence of pellicle - An in vitro study.

OBJECTIVE: Aim of this in vitro study was to investigate erosive tooth loss in dependence of the enamel surface structure and presence of an acquired pellicle. METHODS: Enamel specimens from 19 bovine incisors (4 specimens/incisor) were allocated to four experimental groups (n = 19). The surfaces of half of the specimens were polished (two groups), while the other half was left native (two groups). Specimens of one polished and one native group were placed in pooled human saliva (30 min) for the formation of an acquired pellicle. Thereafter, all specimens were demineralized by superfusion with hydrochloric acid (17 min, pH 2.3) with collection of the superfluent. Erosive substance loss was determined by measuring the dissolved calcium content using a colorimetric assay with Arsenazo III reagent. Differences in erosive substance loss were statistically analyzed with respect to enamel surface and pellicle. A linear mixed effects model was fitted to the data and pairwise differences between groups were evaluated (significance level α= 0.05). RESULTS: Enamel surface structure (p < 0.001) and presence of pellicle (p = 0.01) had a significant effect on erosive substance loss. Polished surfaces with pellicle showed the lowest cumulative calcium release [nmol Ca/mm2] (means ± standard deviation: 48+/-5), followed by polished specimens without (51+/-9) and native specimens with pellicle (54+/-10). No significant differences were found between these groups. Highest cumulative calcium release was found for native specimens without pellicle (61+/-9; p < 0.05). CONCLUSIONS: Both enamel surface structure and the acquired pellicle are important determinants of the susceptibility to erosive tooth loss.

The Effects of Preoperative Radiotherapy on Head and Neck Free Flap Anastomosis Success.

PURPOSE: The long-term survival benefit of neoadjuvant radiotherapy for oropharyngeal tumors is controversially discussed in the literature. To bring more light into this important debate, we evaluated our cases. PATIENTS AND METHODS: In this retrospective study the main focus was the relationship between neoadjuvant irradiation and anastomosis failure. Other influencing factors including previous operative treatment and tumor stage and type also were studied. RESULTS: In total, 7 anastomoses failed (total failure rate, 8.4%; n = 83); 1 of the 7 underwent neoadjuvant irradiation (failure rate, 3.1%; n = 32). All 7 anastomosis failures were in squamous cell carcinoma cases, with 5 of them staged as T4. CONCLUSION: Our data suggest that neoadjuvant radiotherapy for oropharyngeal carcinoma does not increase the risk of postoperative anastomosis failure compared with surgical reconstruction alone. Furthermore, the data suggest a correlation between the stage and type of tumor.