Universities of Applied Sciences.

When the SARS-CoV-2 pandemic started,[1] science came to the immediate attention of the broad public. People and politicians were hanging on every word of medical doctors, virologists, molecular biologists, data scientists and many others in the hope of finding other protective measures than those used for centuries such as basic hygiene, distance, or quarantine. Here, at the Institute of Chemistry and Biotechnology at the Zurich University of Applied Sciences (ZHAW) we were also willing to provide scientific solutions to overcome the pandemic. Together with our partners from industry, we contributed to the development of a Swiss vaccine, are working on filters for active ventilated full protective suits and are developing tests to show the efficacy and safety of an active antiviral textile that allows controlled virus inactivation through an electrochemical reaction by applying a small current.

Surface modification of ultrafine-grained titanium: Influence on mechanical properties, cytocompatibility, and osseointegration potential.

OBJECTIVE: The main objective of this study was to demonstrate that dental implants made from ultrafine-grain titanium (UFG-Ti) can be created that replicate state of the art surfaces of standard coarse-grain titanium (Ti), showing excellent cytocompatibility and osseointegration potential while also providing improved mechanical properties. MATERIAL AND METHODS: UFG-Ti was prepared by continuous equal channel angular processing (ECAP), and surfaces were treated by sandblasting and acid etching. Mechanical properties (tensile and fatigue strength), wettability, and roughness parameters were evaluated. Human trabecular bone-derived osteoblast precursor cells (HBCs) were cultured on all samples to examine cytocompatibility and mineralization after 4 and 28 days, respectively. Biomechanical pull-out measurements were performed in a rabbit in vivo model 4 weeks after implantation. RESULTS: Both yield and tensile strength as well as fatigue endurance were higher for UFG-Ti compared to Ti by 40%, 45%, and 34%, respectively. Fatigue endurance was slightly reduced following surface treatment. Existing surface treatment protocols could be applied to UFG-Ti and resulted in similar roughness and wettability as for standard Ti. Cell attachment and spreading were comparable on all samples, but mineralization was higher for the surfaces with hydrophilic treatment with no significant difference between UFG-Ti and Ti. Pull-out tests revealed that osseointegration of surface-treated UFG-Ti was found to be similar to that of surface-treated Ti. CONCLUSION: It could be demonstrated that existing surface treatments for Ti can be translated to UFG-Ti and, furthermore, that dental implants made from surface-treated UFG-Ti exhibit superior mechanical properties while maintaining cytocompatibility and osseointegration potential.

Ridge preservation after ridge expansion with simultaneous guided bone regeneration: a preclinical study.

OBJECTIVE: To evaluate ridge preservation after ridge splitting with simultaneous implant placement and guided bone regeneration (GBR) in a miniature pig model. MATERIAL AND METHODS: In miniature pigs, the mandibular premolars and first molars were extracted together with removal of the interdental and buccal bone. Three months later, ridge splitting and expansion of the buccal plate were performed with simultaneous placement of two titanium implants per quadrant. On the test side, access by a mucoperiosteal flap followed by GBR with a biphasic calcium phosphate and a collagen membrane was performed. On the contralateral control side, a mucosal flap (MF), leaving the periosteum attached to the buccal bone, was elevated. After healing periods of 6 and 12 weeks, eight and four animals, respectively, were sacrificed for histological and histometric evaluation. RESULTS: In the MF group, all 16 implants were osseointegrated, while in the GBR group, one bone fracture occurred, and six of 16 implants were lost. After 6 weeks, significantly higher bone crest levels were found for the GBR group than for the MF group both buccally and lingually (P < 0.001), and buccal bone thickness was greater in the GBR group than in the MF group (P < 0.001 at the implant shoulder [IS]). After 12 weeks, bone was significantly higher in the GBR group compared to the MF group. Furthermore, buccal bone thickness in the GBR group was 0.93, 4.5, and 5.94 mm at, and 2 and 4 mm apical to the IS, respectively. The corresponding values in the MF group were greatly reduced (0, 0.21, and 2.56 mm). Bone loss on the buccal side compared to the lingual side was significantly greater only in the MF group. CONCLUSIONS: In this ridge expansion model in miniature pigs, the buccal bone volume was significantly better preserved with GBR when compared to a mucosal access flap, provided that soft tissue healing occurred complication free.

Bone loss after ridge expansion with or without reflection of the periosteum.

OBJECTIVE: To evaluate the role of the periosteum in preserving the buccal bone after ridge splitting and expansion with simultaneous implant placement. MATERIAL AND METHODS: In 12 miniature pigs, the mandibular premolars and first molars were removed together with the interdental bone septa and the buccal bone. Three months later, ridge splitting and expansion of the buccal plate was performed with simultaneous placement of two titanium implants per quadrant. Access by a mucosal flap (MF) was prepared on test sides, while a mucoperiosteal flap (MPF) with complete denudation of the buccal bone was increased on control sides. After healing periods of six and 12 weeks, the animals were sacrificed for histologic and histometric evaluation. RESULTS: In the MF group, all 16 implants were osseointegrated, while in the MPF group, four of 16 implants were lost. Noticeable differences of bone levels on the implant surface and of the bone crest (BC) were found between the MF and the MPF group. Buccally after 6 weeks, the median distance between the implant shoulder (IS) and the coronal-most bone on the implant (cBIC) was for the MF group -1.42 ± 0.42 mm and for the MPF group -4.80 ± 2.72 mm (P = 0.15). The median distance between the IS and the buccal BC was -1.24 ± 0.51 mm and -2.78 ± 1.98 mm (P = 0.12) for the MF and MPF group, respectively. After 12 weeks, median IS-cBIC was -2.12 ± 0.84 mm for MF and -7.19 mm for MPF, while IS-BC was -2.08 ± 0.79 mm for MF and -5.96 mm for MPF. After 6 weeks, the median buccal bone thickness for MF and MPF was 0.01 and 0 mm (P < 0.001) at IS, 1.48 ± 0.97 mm and 0 ± 0.77 mm (P = 0.07) at 2 mm apical to IS, and 2.12 ± 1.19 mm and 1.72 ± 01.50 mm (P = 0.86) at 4 mm apical to IS, respectively. After 12 weeks, buccal bone thickness in the MF group was 0 mm at IS, 0.21 mm at 2 mm apical to IS, and 2.56 mm at 4 mm apical to IS, whereas complete loss of buccal bone was measured from IS to 4 mm apical to IS for the MPF group. CONCLUSIONS: In this ridge expansion model in miniature pigs, buccal bone volume was significantly better preserved when the periosteum remained attached to the bone.

Comparison of two dental implant surface modifications on implants with same macrodesign: an experimental study in the pelvic sheep model.

OBJECTIVES: The aim of this study was to compare two different surfaces of one uniform macro-implant design in order to focus exclusively on the osseointegration properties after 2, 4 and 8 weeks and to discuss the animal model chosen. MATERIAL AND METHODS: In six mature sheep, n = 36 implants with a highly crystalline and phosphate-enriched anodized titanium oxide surface (TiU) and n = 36 implants with a hydrophilic, sandblasted, large grit and acid-etched surface (SLA) were placed in the pelvic bone. TiU implants were custom-made to match the SLA implant design. The implant stability and bone-to-implant contact (BIC) were assessed by resonance frequency (ISQ), backscatter scanning electron microscopy (B-SEM), light microscopy (LM), micro-CT and intravital fluorochrome staining. Biomechanical removal torque testing was performed. RESULTS: Overall, no statistically significant differences in BIC total (trabecular + cortical) between TiU and SLA were found via LM and B-SEM. BIC values (B-SEM; LM) in both groups revealed a steady rise in trabecular bone attachment to the implant surface after 2, 4 and 8 weeks. In the 2- to 4-week time interval in the TiU group (P = 0.005) as well as in the SLA group (P = 0.01), a statistically significant increase in BIC trabecular could be observed via LM. B-SEM values confirmed the statistically significant increase for TiU (P = 0.001). In both groups, BIC trabecular values after 8 weeks were significantly higher (P ≤ 0.05) than after 2 weeks (B-SEM; LM). Biomechanical data confirmed the histological data. CONCLUSION: The two surfaces proved comparable osseointegration in this sheep model.

Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep.

OBJECTIVES: The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time. MATERIAL AND METHODS: In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group). RESULTS: Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5). CONCLUSION: Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found.

Influence of non-steroidal anti-inflammatory drugs (NSAIDs) on osseointegration of dental implants in rabbit calvaria.

AIM: Until recently, adverse effects of non-steroidal anti-inflammatory drugs (NSAIDs) on osseointegration of dental implants were unknown. Hence, this study investigated the short- and long-term effects of a 7-day regimen of parecoxib and diclofenac sodium on osseointegration of dental implants in calvarial bone. MATERIAL AND METHODS: Eighteen New Zealand White rabbits were randomly allocated into three groups (each n = 6): Control group with no postoperative pain killers (Group A), diclofenac group (Group B) and parecoxib group (Group C). In each animal, one dental implant was placed into the calvarial bone (total n = 18). Three rabbits from each group were sacrificed in Week 4. The other three rabbits from each group were sacrificed in Week 12 postoperatively. The implant together with the calvarial bone and dura mater was harvested and subjected to micro-computed tomography (micro-CT) and histomorphometric analysis. RESULTS: Quantitative analysis of micro-CT data and histomorphometric data neither revealed any statistically significant (P ≤ 0.05) differences between the three different groups related to osseointegration nor between different time points of observation. CONCLUSION: In rabbits, a 7-day regimen of appropriate doses of diclofenac sodium and parecoxib did not adversely affect osseointegration of dental implants and bone healing in calvaria, neither short nor long term (12 weeks).

Osseointegration of titanium implants functionalised with phosphoserine-tethered poly(epsilon-lysine) dendrons: a comparative study with traditional surface treatments in sheep.

The aim of this study was to analyse the osseointegrative potential of phosphoserine-tethered dendrons when applied as surface functionalisation molecules on titanium implants in a sheep model after 2 and 8 weeks of implantation. Uncoated and dendron-coated implants were implanted in six sheep. Sandblasted and etched (SE) or porous additive manufactured (AM) implants with and without additional dendron functionalisation (SE-PSD; AM-PSD) were placed in the pelvic bone. Three implants per group were examined histologically and six implants were tested biomechanically. After 2 and 8 weeks the bone-to-implant contact (BIC) total values of SE implants (43.7±12.2; 53.3±9.0%) and SE-PSD (46.7±4.5; 61.7±4.9%) as well as AM implants (20.49±5.1; 43.9±9.7%) and AM-PSD implants (19.7±3.5; 48.3±15.6%) showed no statistically significant differences. For SE-PSD and AM-PSD a separate analysis of only the cancellous BIC demonstrated a statistically significant difference after 2 and 8 weeks. Biomechanical findings proved the overall increased stability of the porous implants after 8 weeks. Overall, the great effect of implant macro design on osseointegration was further supported by additional phosphoserine-tethered dendrons for SE and AM implants.

"Anatomical simulation" of the biomechanical behavior of the human mandible.

INTRODUCTION: The load-carrying behavior of the human mandible can be described using finite element simulation, enabling investigations about physiological and pathological skeletal adaption. "Anatomical simulation" implies a stepwise approximation towards the anatomical reality. METHOD: The project is structured in three steps. In Step 1, the preprocessing, the simulation model is provided. Step 2 is the numerical computation. Step 3 is dedicated to the interpretation of the results. The requirements of the preprocessing are: a) realization of the organ's individual anatomy, namely its outer shape; b) the tissue's elastic properties, thus its inner consistency; and c) the organ's mechanical loads. For physiological mandibular loading, these are due to muscles, temporomandibular joints, and tooth forces. Meanwhile, the reconstruction of the macroscopic anatomy from computed tomography data is standard. The periodontal ligament is inserted ex post using an approach developed by the authors. The bone is modeled anisotropically and inhomogeneously. By the visualization of the individual fiber course, the muscular force vectors are realized. The mandibular condyle is freely mobile in a kind of simplified joint capsule. For the realization of bite forces, several approaches are available. RESULTS: An extendible software tool is provided, enabling the user - by variable input of muscle and bite forces - to examine the individual patient's biomechanics, eg, the influence of the periodontal ligament, the condition of the temporomandibular joints, atrophic processes, or the biomechanical situation of dental implants. DISCUSSION: By stepwise approximation towards the anatomical reality, the mandibular simulation will be advanced to a valuable tool for diagnosis and prognosis.

Nanostructures and hydrophilicity influence osseointegration: a biomechanical study in the rabbit tibia.

OBJECTIVE: Implant surface properties have long been identified as an important factor to promote osseointegration. The importance of nanostructures and hydrophilicity has recently been discussed. The aim of this study was to investigate how nanostructures and wettability influence osseointegration and to identify whether the wettability, the nanostructure or both in combination play the key role in improved osseointegration. MATERIALS AND METHODS: Twenty-six adult rabbits each received two Ti grade 4 discs in each tibia. Four different types of surface modifications with different wettability and nanostructures were prepared: hydrophobic without nanostructures (SLA), with nanostructures (SLAnano); hydrophilic with two different nanostructure densities (low density: pmodSLA, high density: SLActive). All four groups were intended to have similar chemistry and microroughness. The surfaces were evaluated with contact angle measurements, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and interferometry. After 4 and 8 weeks healing time, pull-out tests were performed. RESULTS: SLA and SLAnano were hydrophobic, whereas SLActive and pmodSLA were super-hydrophilic. No nanostructures were present on the SLA surface, but the three other surface modifications clearly showed the presence of nanostructures, although more sparsely distributed on pmodSLA. The hydrophobic samples showed higher carbon contamination levels compared with the hydrophilic samples. After 4 weeks healing time, SLActive implants showed the highest pull-out values, with significantly higher pull-out force than SLA and SLAnano. After 8 weeks, the SLActive implants had the highest pull-out force, significantly higher than SLAnano and SLA. CONCLUSIONS: The strongest bone response was achieved with a combination of wettability and the presence of nanostructures (SLActive).

Effects of Er:YAG laser on bacteria associated with titanium surfaces and cellular response in vitro.

This in vitro study examined (a) the anti-bacterial efficacy of a pulsed erbium-doped yttrium aluminum garnet (Er:YAG) laser applied to Streptococcus sanguinis or Porphyromonas gingivalis adhered to either polished or microstructured titanium implant surfaces, (b) the response of osteoblast-like cells and (c) adhesion of oral bacteria to titanium surfaces after laser irradiation. Thereto, (a) bacteria adhered to titanium disks were irradiated with a pulsed Er:YAG laser (λ = 2,940 nm) at two different power settings: a lower mode (12.74 J/cm(2) calculated energy density) and a higher mode (63.69 J/cm(2)). (b) After laser irradiation with both settings of sterile titanium, disks were seeded with 10(4) MG-63 cells/cm(2). Adhesion and proliferation were determined after 1, 4, and 24 h by fluorescence microscopy and scanning electron microscopy. (c) Bacterial adhesion was also studied on irradiated (test) and non-irradiated (control) surfaces. Adhered P. gingivalis were effectively killed, even at the lower laser setting, independent of the material's surface. S. sanguinis cells adhered were effectively killed only at the higher setting of 63.69 J/cm(2). Laser irradiation of titanium surfaces had no significant effects on (b) adhesion or proliferation of osteoblast-like MG-63 cells or (c) adhesion of both oral bacterial species in comparison to untreated surfaces. An effective decontamination of polished and rough titanium implant surfaces with a Er:YAG laser could only be achieved with a fluence of 63.69 J/cm(2). Even though this setting may lead to certain surface alterations, no significant adverse effect on subsequent colonization and proliferation of MG-63 cells or increased bacterial adhesion was found in comparison to untreated control surfaces.

Tooth-Whitening with a Novel Phthalimido Peroxy Caproic Acid: Short Communication.

Professional tooth whitening in the dental office is a popular cosmetic procedure and is performed under carefully monitored conditions. This allows the controlled application of a relatively high concentration of bleaching ingredients based on hydrogen peroxide or peroxide derivatives which produce reactive oxygen species, and consequently induce enamel erosion, alteration of the microhardness of the teeth, irritation of the gums, pain or post bleach sensitivity. This short communication describes the successful and reliable application of a new professional tooth whitening technique using a novel phthalimido peroxycaproic acid complex while avoiding reactive oxygen species.

Healing of osteotomy sites applying either piezosurgery or two conventional saw blades: a pilot study in rabbits.

PURPOSE: The purpose of this study was to compare bone healing of experimental osteotomies applying either piezosurgery or two different oscillating saw blades in a rabbit model. METHODS: The 16 rabbits were randomly assigned into four groups to comply with observation periods of one, two, three and five weeks. In all animals, four osteotomy lines were performed on the left and right nasal bone using a conventional saw blade, a novel saw blade and piezosurgery. RESULTS: All three osteotomy techniques revealed an advanced gap healing starting after one week. The most pronounced new bone formation took place between two and three weeks, whereby piezoelectric surgery revealed a tendency to faster bone formation and remodelling. Yet, there were no significant differences between the three modalities. CONCLUSIONS: The use of a novel as well as the piezoelectric bone-cutting instrument revealed advanced bone healing with a favourable surgical performance compared to a traditional saw.

Efficient cleaning of a macro-structured micro-rough dental implant shoulder with a new coronal vertical groove design: A technical note.

This evaluation assessed the influence of a new implant shoulder design on cleanability using a now established in-vitro study model. Eight test (Botticelli, Di Meliora AG, Basel, Switzerland) and eight control implants (T3 Osseotite, ZimVie, Winterthur, Switzerland), were embedded in standardized defects in simulated bone. The implant surfaces were painted to be visually distinguishable and debrided with ultrasonic instruments (US) and an air powder waterjet device (AIR). Uncleaned implants served as positive controls. After the standardized cleaning, the implants were photographed and divided into three zones (upper marginal shoulder zone (A); lower marginal shoulder zone (B); fully threaded sub-shoulder zone (C)), and analyzed with an image processing software. On test implants, AIR was almost 100% efficacious compared to 80-90% with US, in both upper zones (A/B). In control implants, results of both AIR and US were almost 100% in zone A, but only 55-75% in zone B. In both implants, AIR showed statistically significant higher efficacy than US (P<0.05). Within the limitations of the present in-vitro model, a new macro-structured micro-rough dental implant shoulder with a new coronal vertical groove design shows similar cleanability in comparison to a smooth and machined surface.

Osseointegration and biocompatibility of different metal implants--a comparative experimental investigation in sheep.

BACKGROUND: In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep. METHODS: Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically. RESULTS: Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials. CONCLUSION: This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.

Influence of gaseous ozone in peri-implantitis: bactericidal efficacy and cellular response. An in vitro study using titanium and zirconia.

Dental implants are prone to bacterial colonization which may result in bone destruction and implant loss. Treatments of peri-implant disease aim to reduce bacterial adherence while leaving the implant surface intact for attachment of bone-regenerating host cells. The aims of this study were to investigate the antimicrobial efficacy of gaseous ozone on bacteria adhered to various titanium and zirconia surfaces and to evaluate adhesion of osteoblast-like MG-63 cells to ozone-treated surfaces. Saliva-coated titanium (SLA and polished) and zirconia (acid etched and polished) disks served as substrates for the adherence of Streptococcus sanguinis DSM20068 and Porphyromonas gingivalis ATCC33277. The test specimens were treated with gaseous ozone (140 ppm; 33 mL/s) for 6 and 24 s. Bacteria were resuspended using ultrasonication, serially diluted and cultured. MG-63 cell adhesion was analyzed with reference to cell attachment, morphology, spreading, and proliferation. Surface topography as well as cell morphology of the test specimens were inspected by SEM. The highest bacterial adherence was found on titanium SLA whereas the other surfaces revealed 50-75% less adherent bacteria. P. gingivalis was eliminated by ozone from all surfaces within 24 s to below the detection limit (≥99.94% reduction). S. sanguinis was more resistant and showed the highest reduction on zirconia substrates (>90% reduction). Ozone treatment did not affect the surface structures of the test specimens and did not influence osteoblastic cell adhesion and proliferation negatively. Titanium (polished) and zirconia (acid etched and polished) had a lower colonization potential and may be suitable material for implant abutments. Gaseous ozone showed selective efficacy to reduce adherent bacteria on titanium and zirconia without affecting adhesion and proliferation of osteoblastic cells. This in vitro study may provide a solid basis for clinical studies on gaseous ozone treatment of peri-implantitis and revealed an essential base for sufficient tissue regeneration.

Bactericidal effects of different laser systems on bacteria adhered to dental implant surfaces: an in vitro study comparing zirconia with titanium.

OBJECTIVES: The purpose of this study was to examine in vitro the anti-bacterial efficacy of two different laser systems (CO(2) and diode) applied to Streptococcus sanguinis or Porphyromonas gingivalis cells in suspensions or adhered to zirconia or titanium dental implant materials, with two different surfaces each. MATERIALS AND METHODS: Bacteria were irradiated at two different power settings with either a CO(2) (lambda=10,600 nm) or a diode laser (lambda=810 nm). The lower mode is used clinically (for CO(2) 100 J/cm(2), diode 50 J/cm(2)) and the higher may alter the materials' surface (for CO(2) 1200 J/cm(2), diode 150 J/cm(2)). After irradiation, the number of viable bacteria was determined by culture. RESULTS: Planktonic cells of both species were more resistant to the laser irradiations than bacteria that adhered to surfaces. Adhered P. gingivalis were effectively killed at both wavelengths lambda=10,600 and 810 nm even at the lower settings, independent of the material. S. sanguinis cells that adhered to either zirconia surface were effectively killed by the CO(2) laser at the lower setting of 100 J/cm(2). However, the higher settings of both lasers were needed to reduce S. sanguinis that adhered to titanium surfaces. The CO(2) laser at the lower setting and the diode laser at the higher setting effectively reduced the viability of S. sanguinis or P. gingivalis that adhered to zirconia surfaces. CONCLUSIONS: Under irradiation conditions known not to alter zirconia implant surfaces in vitro, both CO(2) laser (100 J/cm(2)) and the diode laser (150 J/cm(2)) effectively reduced the viability of adhered S. sanguinis or P. gingivalis.

Comparison of Er:YAG laser, piezoelectric, and drill osteotomy for dental implant site preparation: a biomechanical and histological analysis in sheep.

BACKGROUND AND OBJECTIVES: The aim of this study was to examine the influence of implant bed preparation, using either Er:YAG laser ablation, piezoelectric surgery or drill osteotomy, on osseointegration of titanium dental implants after 4, 6, and 8 weeks. MATERIAL AND METHODS: A total of 108 implants (Camlog) were placed in the pelvis of 6 sheep (18 implants/sheep). Implant sites were prepared by an Er:YAG laser, a dental drill or a piezoelectric device. For each time period, six implants were used for biomechanical removal torque testing and six implants for a semi-quantitative histological assessment of the bone-to-implant contact (BIC). RESULTS: An initially missing implant adjusted site preparation led to slightly higher BIC and torque values in the piezoelectric and laser groups due to a press-fit effect after 4 weeks. Statistical analysis of the average mean BIC after 4, 6, and 8 weeks revealed no significant differences (P > 0.05) between the different osteotomy techniques. Comparison of individual removal torque values showed the highest value for laser osteotomy after 8 weeks (1,698.50 +/- 67.52 Nmm), which was significantly higher than the corresponding value for drill osteotomy (P = 0.006). CONCLUSION: Although BIC and removal torque values decreased in the laser and piezoelectric groups at 6 weeks during an active remodeling process, favorable and superior BIC as well as torque values could be demonstrated at 8 weeks. Thus laser and piezoelectric osteotomy seem to be at least comparable to drill osteotomy, concerning early osseointegration and implant stability.

Comparison of Er:YAG laser and piezoelectric osteotomy: An animal study in sheep.

OBJECTIVES: It was the aim of this study to compare the feasibility of complete osteotomy of long bones in sheep using a newly designed variable square pulsed Er:YAG laser and piezoelectric surgery. In addition to uneventful bone healing after laser osteotomy, the goal was to assess the possibility to cut thick bony structures with both techniques in a surgically acceptable time frame of 2-3 minutes. MATERIAL AND METHODS: A tibia midshaft osteotomy was performed in 24 sheep using either an Er:YAG laser (n = 12) or piezoelectric device (n = 12). Laser and piezoelectric groups were divided in two subgroups (n = 6) with sheep sacrificed after 2 and 3 months, respectively. A complete radiological, histological and histomorphometric analysis was performed to compare the course of bone/fracture healing and remodelling. RESULTS: Laser and piezoelectric osteotomies of the sheep tibia up to a depth of 22 mm were possible without any thermal damage. Radiological and histological results after 2 months showed primary gap healing with distinct periosteal callus formation on the transcortex. After 3 months, radiological and histological analysis revealed less callus formation on the transcortex, with almost no visible osteotomy gap and a distinct formation of lamellar bone crossing the original osteotomy gap. CONCLUSION: Er:YAG laser osteotomy can successfully be used in long bones with a depth of up to 22 mm, thus challenging the dogma of adverse effects of laser osteotomy due to thermal or other damages.

Surface alterations of polished and sandblasted and acid-etched titanium implants after Er:YAG, carbon dioxide, and diode laser irradiation.

PURPOSE: Laser treatment has become a popular method for resolving peri-implantitis, but the full range of its effects on implant surfaces is unknown. The purpose of the present investigation was to analyze the influence of different clinically applicable erbium:yttrium-aluminum-garnet (Er:YAG), carbon dioxide (CO2), and diode laser parameters on titanium surfaces that were either polished or sandblasted, large-grit, acid-etched (SLA). MATERIALS AND METHODS: Six polished and six SLA titanium disks were irradiated at nine different power settings (n = 54 polished, 54 SLA) with Er:YAG, CO2, or diode lasers. The CO2 and diode lasers were used in continuous wave mode, and the Er:YAG laser was used in a pulsed manner. The surface of each disk was analyzed by scanning electron microscopy and confocal white light microscopy. Each disk was irradiated on six circular areas of 5 mm in diameter with the same specific laser setting for 10 seconds. RESULTS: Within the chosen parameters, the CO2 and diode laser did not cause any visible surface alterations on either the polished or SLA disks. In contrast, both polished and SLA disks showed surface alterations when irradiated with the pulsed Er:YAG laser. The SLA surfaces showed alteration after 10 seconds of irradiation with Er:YAG laser at 300 mJ/10 Hz. The surfaces of the polished disks did not show alteration with the Er:YAG laser until they were irradiated at the higher energy of 500 mJ/10 Hz for 10 seconds. The results of confocal white light microscopy were in agreement with scanning electron micrographs. CONCLUSION: In contrast to continuous-wave diode and CO2 laser irradiation, pulsed Er:YAG laser irradiation caused distinct alterations with power settings beyond 300 mJ/10 Hz on the SLA surface and 500 mJ/10 Hz on the polished surface. Thus, it is only safe to use the Er:YAG laser for implant surface irradiation with settings no higher than 300 or 500 mJ/10 Hz.