Threshold analysis in the presence of both the diagnostic and the therapeutic risk

The well-established a priori probability of illness threshold in medical decision making, introduced by Pauker and Kassirer (N Engl J Med 293:229–234, 1975; N Engl J Med 302:1109–1117, 1980), involves the diagnostic risk only. We generalize the threshold analysis by adding the therapeutic risk, i.e., in accounting for the risk that a treatment might sometimes fail. We derive a priori probability of illness threshold as a function of the probability of successful treatment, as well as the inverted function, where the successful treatment probability threshold is a function of the a priori probability of illness. The thresholds in the general model are higher than those in the special cases where one of the two risks is absent. Applications show that the changes in the thresholds can be substantial. Our general model might explain empirical findings of much higher thresholds than the Pauker–Kassirer model suggests.     

A clinical and histologic evaluation of implant integration in the posterior maxilla after sinus floor augmentation with autogenous bone,bovine hydroxyapatite,or a 20:80 mixture

PURPOSE: This study was designed to clinically and histologically evaluate the integration of titanium implants in different grafting materials used for maxillary sinus augmentation procedures. MATERIALS AND METHODS: A total of 21 patients and 36 maxillary sinuses were augmented with (1) autogenous particulated bone from the mandibular ramus, (2) bovine hydroxyapatite (BH) with membrane coverage, or (3) an 80/20 mixture of BH and autogenous bone. The grafts were allowed to heal for 6 to 9 months prior to placement of microimplants for histology and standard implants for prosthetic rehabilitation. After another 6 months of healing, when abutments were connected, the microimplants were retrieved for histologic and morphometric analyses. The outcome of the standard implants was clinically evaluated after 1 year of loading. RESULTS: The mean bone-implant contact was 34.6 +/- 9.5%, 54.3 +/- 33.1%, and 31.6 +/- 19.1% for autogenous bone, mixture of 20% autogenous bone/80% BH, and 100% BH, respectively. The corresponding values for the bone area parameter were 37.7 +/- 31.3%, 39.9 +/- 8%, and 41.7 +/- 26.6%. The BH area was found to be 12.3 +/- 8.5% and 11.8 +/- 3.6% for 20% autogenous bone/80% BH and 100% BH, respectively. There were no statistically significant differences for any parameter between any of the groups. After 1 year of loading, 6 of the 33 implants placed in autogenous bone grafts, 2 of the 35 implants placed in the BH/autogenous bone mixture, and 2 of 43 implants placed in BH were lost. There were no statistically significant differences between any of the groups. DISCUSSION: The histomorphometric analysis showed no differences between the 3 groups, indicating that autogenous bone graft can be substituted with bovine hydroxyapatite to 80% or 100% when used for maxillary sinus floor augmentation. The effect of adding autogenous bone remains unclear but may allow for a reduction of the healing time. CONCLUSION: The results from this clinical and histologic study indicate that similar short-term results can be expected when using autogenous bone, BH, or a mixture of them for maxillary sinus floor augmentation and delayed placement of dental implants.     

Influence of impression material and time on the 3-dimensional accuracy of implant impressions.

OBJECTIVE: To investigate, in vitro, the effect of time on the 3-dimensional accuracy of open-tray implant impression copings made of polyvinyl siloxane and polyether impression materials. METHOD AND MATERIALS: Reference models with 4 internal connection implants were fabricated. Four sets of 71 direct impressions were made with square impression copings using an open-tray technique. One set of impressions was made with polyether material (material A) and each of 3 polyvinyl siloxane materials (materials B, C, and D). Three-dimensional changes in spatial orientation of the implant analogs were measured over 48 hours using an optical measurement device. Deviation values were summed over 4 points and averaged per impression. Global differences were tested with a nonparametric Kruskal-Wallis test followed by pairwise comparisons using the Mann-Whitney U test. RESULTS: The mean dimensional accuracy of implant impressions significantly differed over time (P < .001). Materials A and B were found to produce comparable results, For materials C and D there was a significant increase in deviations, with a maximum increase at 2 hours. Deviations for material C were comparable to materials A and B at 48 hours. Baseline values were not maintained by any material. CONCLUSIONS: Within the limits of this in vitro study, it can be concluded that time cannot be neglected as a factor affecting the accuracy of implant master casts.     

All-ceramic systems: laboratory and clinical performance

Several all-ceramic systems have been developed in dentistry to meet the increased expectations of patients and dentists for highly aesthetic, biocompatible, and long-lasting restorations. However, early bulk fractures or chippings have led the research community to investigate the mechanical performance of the all-ceramic systems. This overview explores the current knowledge of monolithic and bilayer dental all-ceramic systems, addressing composition and processing mechanisms, laboratory and clinical performance, and possible future trends for all-ceramic materials.     

Short-term anti-plaque effect of two chlorhexidine varnishes

BACKGROUND: Chlorhexidine (CHX) varnishes have been mainly used for the prevention of caries in high-risk populations. Reports regarding their anti-plaque effect on a clinical level are limited to non-existing as opposed to their microbiological impact on plaque formation. AIM: The aim of this preliminary investigation was to evaluate the anti-plaque effect of two CHX varnishes applied on sound enamel in relation to a positive control, a negative control and to one another. METHODS: Sixteen healthy subjects volunteered for this randomized-controlled, single-blind, four-treatment-four-period crossover-designed clinical trial. A 3-day plaque re-growth model was used to determine de novo plaque accumulation following CHX rinsing, Cervitec application, EC40 application and no therapy. The amount of plaque was measured using the Quigley and Hein plaque index and "automatic image analysis" (AIA). RESULTS AND CONCLUSIONS: Varnish treatment resulted in significantly higher plaque levels than CHX rinsing irrespective of the varnish that was used (p< or =0.002), implying that the latter is likely to remain the gold standard as an anti-plaque agent. However, highly significant differences were also found in favour of both varnish systems when compared with no therapy (p<0.001), which indicates that varnish treatment is an effective means of inhibiting plaque formation in a short time span. Cervitec exhibited slightly, yet significantly, higher plaque levels in comparison with EC40 as determined by AIA (p=0.006). Large-scale trials with a longer observation period are necessary to substantiate these results.     

Postoperative nausea and vomiting after surgery for prognathism: not only a question of patients' comfort. A placebo-controlled comparison of dolasetron and droperidol.

INTRODUCTION: The aim of this study was to evaluate the efficacy of dolasetron and droperidol (DHB) for preventing postoperative nausea and vomiting (PONV) in patients undergoing surgery for prognathism. MATERIAL AND METHODS: In a randomised, placebo-controlled, double-blind trial, the efficacy of 12.5 mg dolasetron i.v. and 1.25 mg DHB was evaluated in preventing PONV in 83 patients undergoing surgery for prognathism. Patients were allocated randomly to one of three groups: group A (n=27) received 12.5 mg dolasetron intravenously (i.v.), group B (n=27) received 1.25 mg DHB i.v. and placebo group C (n=29) received saline 0.9%. If patients complained of retching or vomiting or if patients demanded antiemetics, 20mg metoclopramide (MCP) i.v. was given. Postoperative nausea, postoperative vomiting, or nausea and vomiting was assessed in the postoperative period at 0-4 h and overall between 0 and 24 h. RESULTS: A significant reduction in the incidence of postoperative nausea and/or vomiting was observed in the dolasetron group (33%) when compared with DHB (81%) and placebo (86%) treated patients. No other significant differences between the DHB and the placebo group were found. Dolasetron (11%) significantly reduced vomiting in comparison with the DHB (52%) and placebo group (52%). The use of postoperative MCP per patient was significantly lower in the dolasetron group when compared with both other groups. Dolasetron significantly reduced the postoperative nausea and/or vomiting-score when compared with both other groups. There was no significant difference between DHB- and placebo-treated patients with regard to nausea and/or vomiting. CONCLUSION: Intravenous dolasetron (12.5 mg) is more effective than either intravenous DHB (1.25 mg) or placebo for preventing PONV after surgery for prognathism. It also was significantly superior to either DHB or placebo concerning nausea and vomiting and the need for MCP rescue medication.     

A histomorphometric comparison of the bone graft-titanium interface between interpositional and onlay/inlay bone grafting techniques

PURPOSE: To analyze the bone graft-implant interface of titanium microimplants (MIs) placed at the time of bone grafting or after a healing period of 6 months and retrieved after another 6 to 14 months of healing. Integration of MIs placed in interpositional bone grafts (IBGs) in conjunction with a Le Fort I osteotomy was compared with the integration of those placed in onlay/inlay bone grafts (OBGs). MATERIALS AND METHODS: The severely atrophied edentulous maxillae of 23 patients (14 women, 9 men) were restored with autogenous bone grafts (either IBG [n=8] or OBG [n=15]) and titanium implants. Six-month periods were allowed between grafting, implant placement, and abutment connection. The bone-implant interface was studied histologically with the use of unloaded titanium MIs. RESULTS: Sixty-eight MIs were either (1) placed simultaneously with grafting and retrieved after 6, 12, or 14 months or (2) placed after 6 months of healing and retrieved after another 6 to 8 months. Histomorphometry indicated equal degrees of osseointegration for the 2 intraoral reconstruction techniques when looking at bone-implant contact, bone area in threads, and newly formed bone (NFB) (Student t test for unpaired observations). There was a significant difference between simultaneous and delayed implant placement with respect to BIC and NFB (Student t test for paired observations). Three additional MIs placed in the nongrafted residual alveolar ridge and retrieved after 6 months showed significantly more bone in threads and NFB (Student t test for paired observations; P = .003 and P = .009, respectively) compared to MIs placed at graft placement (6 months' healing). DISCUSSION: Timing of implant placement appeared more important than healing time or surgical technique. The delayed approach resulted in better implant integration, probably because of the initial revascularization of the graft. CONCLUSIONS: Implant integration was similar in the IBG and OBG groups. Placement of MIs after an initial healing period of 6 months resulted in better integration than placement simultaneously with grafting.     

Effect of platform switching on peri-implant bone levels: a randomized clinical trial

Objective: The concept of platform switching has been introduced to implant dentistry based on observations of reduced peri‐implant bone loss. However, randomized clinical trials are still lacking. This study aimed to test the hypothesis that platform switching has a positive impact on crestal bone‐level changes. Material and methods: Two implants with diameters of 4 mm were inserted epicrestally into one side of the posterior mandibles of 25 subjects. After 3 months of submerged healing, the reentry surgery was performed. On the randomly placed test implant, an abutment 3.3 mm in diameter was mounted, resulting in a horizontal circular step of 0.35 mm (platform switching). The control implant was straight, with an abutment 4 mm in diameter. Single‐tooth crowns were cemented provisionally. All patients were monitored at short intervals over the course of 1 year. Standardized radiographs and microbiological samples from the implants' inner spaces were obtained at baseline (implant surgery), and after 3, 4, and 12 months. Results: After 1 year, the mean radiographic vertical bone loss at the test implants was 0.53±0.35 mm and at the control implants, it was 0.58±0.55 mm. The mean intraindividual difference was 0.05±0.56 mm, which is significantly <0.35 mm (P=0.0093, post hoc power 79.9%). The crestal bone‐level changes depended on time (P<0.001), but not on platform switching (P=0.4). The implants' internal spaces were contaminated by bacteria, with no significant differences in the total counts between the test and the control at any time point (P=0.98). Conclusions: The present randomized clinical trial could not confirm the hypothesis of a reduced peri‐implant bone loss at implants restored according to the concept of platform switching. To cite this article:
Enkling N, Jöhren P, Klimberg V, Bayer S, Mericske‐Stern R, Jepsen S. Effect of platform switching on peri‐implant bone levels: a randomized clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 1185–1192.
doi: 10.1111/j.1600‐0501.2010.02090.x     

Effect of oxybenzone on PGE2-production in vitro and on plaque and gingivitis in vivo

OBJECTIVES: To study the effect of oxybenzone on prostaglandin E2 (PGE2) production in cell culture and to evaluate the effect of an oxybenzone-containing dentifrice on plaque and gingivitis in a 6-week clinical trial. MATERIAL AND METHODS: Human embryo palatal mesenchyme (HEPM) cells were used for testing the inhibition of IL-1beta-stimulated PGE2-production in vitro by different concentrations of oxybenzone. For the in vivo study, a total of 66 individuals with a Quigley & Hein plaque index of at least 1.5 and an Ainamo & Bay gingival index of at least 0.2 were included in a double-blind clinical trial with two cells and a parallel design. Two compositions of fluoride dentifrice were used, one with the addition of 0.5% oxybenzone, and one without. Plaque and gingival index were obtained at three time points: (1) at baseline, (2) after 3 weeks, and (3) after 6 weeks. RESULTS: A dose-dependent inhibition of PGE2-production was found in the HEPM cell culture following oxybenzone exposure. In the clinical trial, a 25% reduction of gingival index was observed in the oxybenzone group (p<0.001) after 6 weeks as compared with 2% for the placebo group. CONCLUSIONS: These findings indicate that PGE2-production is reduced by oxybenzone in vitro and that the use of oxybenzone in a dentifrice reduces gingivitis in vivo.     

Effect of grafting materials on osseointegration of dental implants surrounded by circumferential bone defects. An experimental study in the dog

Aims: This study was designed to evaluate the effect of gap width and graft placement on bone healing around implants placed into simulated extraction sockets in the mandibles of four beagle dogs. Materials and methods: Four Ti‐Unite^® implants (13 mm × 3.3 mm) were placed on each side of the mandible. Three implants were surrounded by a 1.35 mm circumferential and a 5 mm deep gap around the coronal portion of the implants. A fourth implant was inserted conventionally into both sides of the mandibles as a positive control. The gaps were filled with either Bio‐Oss^®, autogenous bone or with a blood clot alone. The study design was balanced for animal, side and modality. Ground sections were prepared from biopsies taken at 3 months, and computer‐aided histometric measurements of bone/implant contact and area of bone within threads were made for the coronal 5 mm. Data were analysed using analysis of variance. Results: The mean bone/implant contact was 9.8 mm for the control and ranged from 9.3 to 11.3 mm for the three test modalities. The corresponding values for area within threads were 1 mm² and 1–1.2 mm². Modality had a significant effect on both bone/implant contact (F=16.9; P<0.0001) and area within threads (F=16.7; P<0.0001). Conclusion: The results of this study suggest that both autogenous bone graft and Bio‐Oss^® played an important role in the amount of hard tissue fill and osseointegration occurring within marginal bone defects around implants.