Thermal effects of various drill materials during implant site preparation-Ceramic vs. stainless steel drills: A comparative in vitro study in a standardised bovine bone model.

OBJECTIVES: The aim of this study was to evaluate thermal effects of ceramic and metal implant drills during implant site preparation using a standardised bovine model. MATERIAL AND METHODS: A total of 320 automated intermittent osteotomies of 10- and 16-mm drilling depths were performed using zirconium dioxide-based and stainless steel drills. Various drill diameters (2.0/ 2.2, 2.8, 3.5, 4.2 mm ∅) and different cooling methods (without/ with external saline irrigation) were investigated at room temperature (21 ± 1°C). Temperature changes were recorded in real time using two custom-built multichannel thermoprobes in 1- and 2-mm distance to the osteotomy site. For comparisons, a linear mixed model was estimated. RESULTS: Comparing thermal effects, significantly lower temperatures could be detected with steel-based drills in various drill diameters, regardless of drilling depth or irrigation method. Recorded temperatures for metal drills of all diameters and drilling depths using external irrigation were below the defined critical temperature threshold of 47°C, whereas ceramic drills of smaller diameters reached or exceeded the harmful temperature threshold at 16-mm drilling depths, regardless of whether irrigation was applied or not. The results of this study suggest that the highest temperature changes were not found at the deepest point of the osteotomy site but were observed at subcortical and deeper layers of bone, depending on drill material, drill diameter, drilling depth and irrigation method. CONCLUSIONS: This standardised investigation revealed drill material and geometry to have a substantial impact on heat generation, as well as external irrigation, drilling depth and drill diameter.

A novel standardized bone model for thermal evaluation of bone osteotomies with various irrigation methods.

OBJECTIVES: Based on a novel standardized bovine specimen, the aim of this study was to investigate thermal effects of different irrigation methods during intermittent and graduated drilling. MATERIAL AND METHODS: Temperature changes during implant osteotomies (n = 320) of 10 and 16 mm drilling depths with various irrigation methods were investigated on manufactured uniform bone samples providing homogenous cortical and cancellous areas and analogous thermal conductivity comparable to human bone. Automated sequences were performed with surgical twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. Real-time recording of temperature increase was done using two custom-built multichannel thermoprobes with 14 temperature sensors at a predefined distance of 1 and 2 mm to the final osteotomy. The effects of drilling depth, drilling diameter and irrigation methods on temperature changes were investigated by a linear mixed model. RESULTS: Using this uniform bone specimen, the greatest temperature rise was observed without any coolant supply with 29.87°C, followed by external with 28.47°C and then internal with 25.86°C and combined irrigation with 25.68°C. Significant differences (P ≤ 0.0156) between drill depths of 10 vs. 16 mm could be observed with all irrigation methods evaluated. With each of the irrigation methods, significantly higher temperature changes (P < 0.0001) during osteotomies could be observed between twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. During 10 and 16 mm drilling osteotomies, external irrigation showed significantly higher temperatures (P < 0.05) for all conical drills compared with internal or combined irrigation, respectively. Significantly lower temperatures (P < 0.05) could be detected with internal or combined irrigation for the use of conical drills with various diameters and drilling depths. CONCLUSIONS: This fully standardized bone model provides optimized comparability for the evaluation of bone osteotomies and resulting temperature changes. As regards the efficiency of the various irrigation methods, it could be demonstrated that internal and combined irrigation appears to be more beneficial than external irrigation.

The use of a polylactide-based copolymer as a temporary skin substitute in deep dermal burns: 1-year follow-up results of a prospective clinical noninferiority trial.

Deep dermal burns can be covered with different kind of materials and techniques; one of them is a polylactide-based temporary skin substitute. The aim of this study was to intraindividually compare its 1-year outcome with the results obtained by use of autologous skin grafts in patients suffering from deep dermal burns. A prospective noninferiority trial was designed in order to assess skin quality and scar formation by use of subjective (Vancouver Scar Scale; Patient and Observer Scar Assessment Scale) and objective (noninvasive cutometry) burn scar assessment tools. All items of the Patient and Observer Scar Assessment Scale, except vascularity, were found to be noninferior in the areas covered with the temporary skin substitute vs. autologous skin. Results of objective scar evaluation showed comparable viscoelastic parameters without reaching noninferiority. Overall, the outcome of deep dermal burns covered with a polylactide-based temporary skin substitute revealed satisfactory results in terms of scar formation and skin quality as compared with autologous skin. This paper supports its use in deep dermal burns, where autologous skin donor sites require either to be reserved for coverage of full-thickness skin defects in severe burns or to be saved for reduction of additional morbidity in selected patient collectives.

Drilling- and withdrawing-related thermal effects of implant site preparation for ceramic and stainless steel twist drills in standardized bovine bone.

INTRODUCTION: Excessive surgical trauma is believed to be among the most important causes for early implant losses. As thermal injury to the bone is not only dependent on the amount of generated heat but also on the tissue exposure time, and the greatest temperature increase was found within the withdrawing period, the entire osteotomy procedure with the parameters contributing to thermal damage is of particular clinical relevance. The aim of this study was to investigate the thermal performance of metal-based and ceramic implant drills regarding the temperature exposure time during the whole osteotomy process. MATERIALS AND METHODS: This investigation consisted of 240 individual preparations in total, comprising two different drilling depths (10 and 16 mm), two irrigation methods (external and without irrigation), two implant drill materials (stainless steel and zirconia), and three consecutive drill diameters per material (2.0/2.2, 2.8, and 3.5 mm) with 10 identical repetitions. Real-time multichannel temperature measurement was conducted during automated drilling procedures in standardized bovine bone specimens. RESULTS: The maximum temperature changes were highly associated with the time period of passive drill withdrawing (p ≤ 0.05), irrespective of drill material, drilling depth, or drill diameter. Statistically significant differences in temperature generation between stainless steel and ceramic drills were observed in irrigated testing sites at both drilling depths with smaller drill diameters (2.0/2.2 and 2.8 mm, p ≤ 0.05). CONCLUSION: Results of this in vitro study could demonstrate a strong association between the highest temperature increase and the passive withdrawing time period in both investigated drill materials. Considering these findings and the resulting thermal bone damage due to the whole surgical procedure, high overall temperatures in combination with a prolonged heat exposure time may impact the future osseointegration process.

Survival rate of autotransplanted teeth after 5 years - A retrospective cohort study.

BACKGROUND: Autotransplantation of teeth (TX) is a predictable treatment option, although this type of therapy is often overlooked compared to other types of restorations. PURPOSE: As current literature contains few long-term studies concerning the outcome of autotransplanted immature molars, the aim was to evaluate results after a follow-up period of 5 years. MATERIAL AND METHODS: This retrospective study enrolled all patients treated with immature autotransplanted molars after a follow-up period of 5 years. In order to ensure comparable results, survival rate was investigated as well as clinical and radiological parameters. Contralateral teeth (TC) were used as controls for further assessments and for ensuring comparable future results. RESULTS: 52 patients with 66 TX were examined. Mean age at the time of surgery was 19.64 years. Tooth survival rate after 5 years was 89.39%. The results for parameters such as PPD, BOP, mobility, dental caries, periapical pathologies and endodontic treatments showed no differences. In contrast, dental restorations (p < 0.001), occlusal contacts (p = 0.003) and sensitivity (p < 0.001) differed significantly between TX and TC. CONCLUSIONS: The current findings clearly confirm that TX is an effective alternative treatment option to fixed prosthodontic restorations and dental implants, and provides for results equivalent to those with the patients' natural teeth.

The combination of muscle transpositions and static procedures for reconstruction in the paralyzed face of the patient with limited life expectancy or who is not a candidate for free muscle transfer.

BACKGROUND: In long-standing complete and irreversible facial palsy where reconstruction by nerve grafting alone is no longer sufficient, reconstruction by dynamic procedures such as muscle transplantation or muscle transposition is required. The authors present the results obtained by regional muscle transposition for reconstruction of eye closure and smile in patients with irreversible facial palsy. METHODS: Twenty-nine patients treated by temporalis transposition for the eye and eight patients treated by masseter transposition for the mouth are presented. Assessment of outcome was based on clinical examination and analysis of facial movements by three-dimensional video analysis. RESULTS: Preoperatively, the paretic eye fissure was on average 2.30 +/- 2.17 mm wider than the healthy one. The difference was reduced postoperatively to 0.95 +/- 1.89 mm. Paralytic lagophthalmus during closure of the eyes was 9.59 +/- 3.03 mm preoperatively and was reduced postoperatively to 4.33 +/- 2.68 mm. Ocular tearing and desiccation were reduced drastically in all patients. Static asymmetry of the mouth corner improved from 14.17 +/- 5.26 mm preoperatively to 5.38 +/- 3.23 mm postoperatively. The index of dynamic symmetry improved from -0.17 +/- 0.25 preoperatively to 0.18 +/- 0.19 postoperatively. This means that, postoperatively, the amplitude of motion on the reconstructed side reached 18 +/- 19 percent that of the amplitude on the healthy side, whereas preoperatively a shift of the paralyzed mouth corner toward the healthy side occurred. CONCLUSIONS: Muscle transposition improves static symmetry and provides dynamic activity to a certain degree. It is therefore a valuable concept for patients with limited life expectancy.

Three-dimensional video analysis of the paralyzed face reanimated by cross-face nerve grafting and free gracilis muscle transplantation: quantification of the functional outcome.

BACKGROUND: Surgeons have found it difficult to quantify facial paralysis and its improvement by reconstructive surgery. This article presents the results achieved by free functional muscle transplantation for reconstruction of the paralyzed face, registered by three-dimensional video analysis of facial movements. METHODS: Of patients treated consecutively between 1997 and 2006, two groups were constituted: group 1 comprised 22 patients with reinnervation completed after a single cross-face nerve graft and a free gracilis muscle graft for reconstruction of the smile; group 2 comprised nine patients treated with two cross-face nerve grafts followed by a territorially differentiated gracilis muscle transplant for reconstruction of the smile and eye closure. Smiling with showing teeth, maximal showing of teeth, and closing the eyes as in sleep were analyzed in detail. RESULTS: In group 1, static asymmetry was reduced from 12.19 +/- 8.73 mm preoperatively to -1.84 +/- 7.67 mm at 18 months postoperatively. Smile amplitude increased from 9 to 60 percent of that on the healthy side in 10 incomplete facial palsies of this group, and from 0 to 62 percent in eight functionally successful muscle grafts among 11 patients with complete lesions. In group 2, static asymmetry improved from 7.24 +/- 12.64 mm to -5.36 +/- 9.07 mm; the overcorrection was intentional. Movement was improved in eight cases. Smile amplitude reached 68 +/- 43 percent of that on the normal side. Lagophthalmus improved from 7.21 +/- 3.59 mm to 1.38 +/- 2.49 mm. All improvements were statistically significant (p

Effect of platelet-released growth factors and collagen type I on osseous regeneration of mandibular defects. A pilot study in minipigs.

OBJECTIVE: To study the effects of platelet-released growth factors (PRGF) and collagen type I on bone defect healing in minipig mandibles. MATERIAL AND METHODS: In eight adult minipigs defects were trephined in the facial mandibular wall from extra-oral and filled with collagen+PRGF or with collagen alone. Control defects were left untreated. PRGF were defined as the supernatants obtained after centrifugation of washed, thrombin-activated allogenic cells of platelet-rich plasma. The animals were sacrificed at 4 and 8 weeks. For histological analysis, undecalcified ground specimens stained with the Levai-Laczko stain were used. RESULTS: For the entire follow-up, the amount of newly formed bone was 35.49 +/- 3.84% in the collagen+PRGF group, 46.34 +/- 3.84% in the collagen-only group and 33.83 +/- 4.11% in the controls. The differences between the collagen+PRGF and the collagen-only group (p = 0.0343), and between the collagen-only group and the controls (p = 0.0305) were significant. Histologically, defects filled with collagen+PRGF showed inflammatory reactions at 4 weeks, and new bone formation near the remnants of the filler collagen was reduced. CONCLUSION: The data suggest that collagen type I alone, but not its combination with PRGF can support the early stages of cortical bone repair.