Nonlinear optomechanical measurement of mechanical motion.

Precision measurement of nonlinear observables is an important goal in all facets of quantum optics. This allows measurement-based non-classical state preparation, which has been applied to great success in various physical systems, and provides a route for quantum information processing with otherwise linear interactions. In cavity optomechanics much progress has been made using linear interactions and measurement, but observation of nonlinear mechanical degrees-of-freedom remains outstanding. Here we report the observation of displacement-squared thermal motion of a micro-mechanical resonator by exploiting the intrinsic nonlinearity of the radiation-pressure interaction. Using this measurement we generate bimodal mechanical states of motion with separations and feature sizes well below 100 pm. Future improvements to this approach will allow the preparation of quantum superposition states, which can be used to experimentally explore collapse models of the wavefunction and the potential for mechanical-resonator-based quantum information and metrology applications.

Reverse torque failure of screw-shaped implants in baboons: baseline data for abutment torque application.

Torque failure for endosseous implants has been used as a biomechanical measure of anchorage, though the significance of such data is not known. A practical understanding of the resistance to torque failure of implant-tissue interfaces at stage 2 surgery would help in assigning torque levels for implant abutment-screw fastening. The purpose of this study was to measure torque failure levels of commercially pure (CP) titanium, Ti-6Al-4V, hydroxyapatite-coated (HA-coated) screw-shaped implants placed into the maxillae and mandibles of baboons. Implants identical in size were placed into the edentulous posterior maxillae and mandibles of six female baboons (n = 37 each group) using a standardized surgical protocol. Reverse-torque data were collected at postinsertion time intervals ranging from 3 to 4 months using a counterclockwise torque driver and the data were analyzed (repeated measures ANOVA) for torque differences related to time, biomaterial, and jaw. The HA-coated implants exhibited significantly greater torque-removal values compared to both metallic implants (HA: 186.0 Ncm [50.1]; Ti-6Al-4V: 78.6 Ncm [18.1]; CP Ti 74.0 Ncm [24.4]). Analysis of torque interactions with jaw showed no significant difference; however, the mandible was found to be greater than the maxilla in torque resistance for all groups tested. Understanding the risks in inferring animal data to human application, the clinical implications of these data suggest that the recommended torque level of 35 Ncm for abutment fastening may provide a margin of safety for most implants of similar design and material as used in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Histomorphometric analysis of implant anchorage for 3 types of dental implants following 6 months of healing in baboon jaws.

In an effort to better understand the supporting anatomy for unloaded endosseous dental implants, this study focused on the histomorphometric analysis of 3 different types of implants placed into non-human primate jaws and allowed to heal for 6 months. This report describes data from 24 screw-type dental implants placed in edentulated (2 months healing time) posterior arches of 4 adult female baboons. Three different implants were placed and allowed to heal for 6 months prior to processing for evaluation: commercially pure titanium (n = 8), titanium alloy (n = 8), and titanium plasma-sprayed (n = 8). Circumferential bone-implant interface sampling from 6 regions along the entire length of each implant was obtained for evaluation of percent bone-implant contact (%BIC) and percent bone area (%BA), within 3 mm of the implant. Data were collected (reliability of 1.6% for both parameters) and analyzed by an observer blinded to implant material using IMAGE analysis software for differences between jaws, implant biomaterials, and jaw/biomaterial (analysis of variance, pairwise comparison using least squares method with Bonferroni adjustment). The results indicated that the overall mean %BIC was 55.8 and mean %BA was 48.1. Maxillary and mandibular differences for both parameters were statistically significantly different: %BIC in maxilla 50.8, in mandible 60.8; %BA in maxilla 43.6, in mandible 52.6 (both significant at the P < .05 level). The biomaterial analyses revealed no significant differences between the different implants for %BIC or %BA. The trend observed--that mandibular values were greater than maxillary values for the overall jaw comparisons--was found to be consistent at the jaw/biomaterial level, although the small sample size limited statistical power. These data, along with data from a previous 3-month study, provide insight into baseline supporting anatomy for dental implants.

Reverse-torque failure of screw-shaped implants in baboons after 6 months of healing.

Mechanical testing of the implant-tissue interface has been the focus of numerous investigations concerning the anchorage capacity of implants. The purpose of this study was to measure reverse-torque failure after 6 months of healing for three different biomaterials in the posterior jaws of four adult female baboons. The animals had all of their posterior teeth surgically extracted and, following 10 weeks of healing, 7 implants were placed in each quadrant. The biomaterials included titanium plasma-sprayed surfaces, titanium-aluminum-vanadium surfaces (both 3.8 mm x 10 mm), and a commercially pure titanium surface (3.75 mm x 10 mm). After 6 months, torque data were collected using a counterclockwise computerized torque driver and were analyzed by repeated measures analysis of variance for differences related to biomaterial, jaw, and biomaterial/jaw. Post-hoc Tukey Kramer analysis was also performed for within-group differences (alpha = .05 level). The biomaterial comparison revealed a significant difference between the titanium plasma-sprayed and the combined commercially pure titanium/titanium -aluminum-vanadium groups (analysis of variance, Tukey Kramer, P < .05). The jaw comparison showed no significant difference, although the data suggest that higher forces may be required for mandibular torsional failure. The biomaterial/jaw comparison revealed that jaw differences for the mean values of commercially pure titanium and titanium-aluminum-vanadium implants were greater than jaw differences for mean values of titanium plasma-sprayed implants, although these differences were not statistically significant. Because of the lack of correlation between single-cycle biomechanical tests and clinical performance, it is necessary to be selective in assigning usefulness to data of this type.

Quantitative histomorphometric description of implant anchorage for three types of dental implants following 3 months of healing in baboons.

Important to the understanding of the dynamics associated with dental implant anchorage over time is a knowledge of the supporting anatomy for common endosseous implants prior to being placed into function. This study followed 20 screw-shaped dental implants placed in edentulated (2 months' healing time) posterior jaws of five adult female baboons. Implants made of three biomaterials were placed and allowed to heal for 3 months prior to processing for evaluation. Percentage integration and bone area data from six horizontal sections along the entire length of each implant were collected and analyzed for differences between jaws, implant biomaterials, jaw/biomaterial, and sections of the implants (ANOVA, pairwise comparison using LSM with Bonferroni adjustment). The results indicated that overall mean percentage integration was 46.5 and mean percentage bone area was 39.9. Maxillary and mandibular differences for both parameters were statistically different (integration: maxillary = 38.1%, mandibular = 56.7%; bone area: maxillary = 35.8%, mandibular = 44.9%; both were significant at the P < .05 level). The biomaterial analyses revealed significant differences for percentage integration between the metal implants and the hydroxyapatite-coated implant (commercially pure titanium = 39.1%, titanium-aluminum-vanadium = 40.0%, hydroxyapatite-coated = 61.5%), but no such difference was noted for percentage bone area (commercially pure titanium = 38.8%, titanium-aluminum-vanadium = 38.9%, hydroxyapatite-coated = 42.3%). Discussion of the relative importance of the two parameters highlights the fact that resistance to functional loads requires establishing and then maintaining an adequate volume of bone, which may have a functionally specific structure based on the mechanical properties of the local jaw environment.

Effect of prosthetic superstructure accuracy on the osteointegrated implant bone interface.

OBJECTIVE: This study evaluated the biologic result of forces induced by a misfitting prosthetic superstructure on implants placed in a New Zealand white rabbit tibia model. STUDY DESIGN: Nine rabbits had two dental implants placed in both right and left proximal tibias. After 6 weeks, one animal was sacrificed for baseline integration data, and the remaining animals had fitting or misfitting prosthetic superstructures attached to the implants for 12 weeks. Implants were evaluated clinically, radiographically, and histomorphometrically at the scanning electron microscopic level. RESULTS: No clinical, radiographic, or histomorphometric evidence exists of integration failure with implants subjected to superstructure strain, although bone remodeling is noted. CONCLUSIONS: Given the limitations of sample size, animal model used, duration of prosthetic superstructure attachment, and loading confounders possible, the study of prosthetic framework misfit must be evaluated with another animal model, such as an intraoral primate model, to determine the relationship between clinical performance and histologic findings.

Alveolar osteitis after surgical removal of impacted mandibular third molars. Identification of the patient at risk.

One hundred thirty-eight impacted mandibular third molars were surgically removed. A prospective study of risk factors associated with the development of alveolar osteitis (dry socket) postoperatively was undertaken. Two surgeons, one experienced and one inexperienced, removed the teeth. Patients were controlled for age, sex, use of oral contraceptives, radiographic difficulty of the extraction, and tobacco use. Patients treated by the inexperienced surgeon and those using tobacco had a significantly greater incidence of alveolar osteitis. Previously identified risk factors of increased age, female sex, oral contraceptive use, and increased surgical time were not associated with an increased incidence of dry socket. Recommendations are made regarding prevention of alveolar osteitis in those patients identified as being at high risk.

The effect of a chlorhexidine rinse on the incidence of alveolar osteitis following the surgical removal of impacted mandibular third molars.

A prospective randomized double-blind placebo-controlled study was conducted with 139 patients (278 bilaterally impacted mandibular third molars) to determine the effect of a perioperative 0.12% chlorhexidine gluconate rinse on the incidence of alveolar osteitis following surgical removal of impacted mandibular third molars. A statistically significant 60% reduction in the incidence of alveolar osteitis was obtained in the chlorhexidine group compared with the placebo group. In most subgroups analyzed, chlorhexidine was associated with at least a 50% reduction in alveolar osteitis compared with control groups.

The diagnosis and treatment of the dislocated mandible.

Dislocation of the mandible occurs commonly. Most patients present to the emergency department for treatment. This article discusses the normal temporomandibular joint (TMJ) anatomy and the etiology, types, and diagnosis of mandibular dislocation. It also describes the initial management, including techniques for reduction of the acute anteriorly dislocated mandible.

The use of a pedicled temporalis muscle-pericranial flap for replacement of the TMJ disc: preliminary report.

Disc replacement in temporomandibular joint surgery has been troublesome. Problems such as migration, fragmentation, foreign body reactions, and unpredictable biodegradation have occurred. Autogenous tissue is presently the material of choice, but requires a second surgical site. In addition, it is a free graft, and thus its fate is unknown. A technique has been developed that uses a pedicled autogenous flap composed of a portion of the temporalis muscle and pericranium to act as an interpositional material in temporomandibular joint surgery. The flap, based on the deep temporal arteries, and pedicled off of the coronoid process, is rotated anterior to the articular eminence and then posteriorly into the temporomandibular joint where it is sutured to the retrodiscal tissue. This procedure allows maintenance of tissue viability and functional movement of the flap during mandibular excursions. The technique offers numerous advantages over the existing autogenous, allogeneic, and alloplastic materials presently used in temporomandibular joint surgery.

A systematic approach to management of high-flow vascular malformations of the mandible.

High-flow vascular malformations of the mandible are associated with significant morbidity and mortality. As these lesions are rare, the experience that a clinician has with treatment may be limited. To facilitate understanding and treatment of such lesions in a controlled and efficient manner, a treatment protocol is presented that includes careful preoperative planning, embolization, and surgery.

Generalized eruptive keratoacanthoma.

Two forms of keratoacanthoma are presently recognized: a solitary form and a multiple form. The multiple form has two variants: multiple self-healing epitheliomas of skin or Ferguson Smith type and eruptive keratoacanthoma or Grzybowski type. Though solitary cutaneous keratoacanthomas are common, the multiple variants are extremely rare. A case of eruptive keratoacanthoma with oral involvement is presented with a brief discussion contrasting the two variants of multiple keratoacanthoma.

Etiology of implant complications: anecdotal reports vs prospective clinical trials.

The dental profession has in the past overreacted to anecdotal reports of both positive and negative outcomes involving implants. Because implant complications usually involve multiple variables, it is necessary to isolate these variables as much as possible when structuring a study to assess implant success vs failure. The methodology used in a study of Omniloc implants is reported, including detailed criteria for patient exclusion, patient demographics, statistical method, measurement indices, control procedures, and success criteria.

The relationship of Periotest values, biomaterial, and torque to failure in adult baboons.

A quantitative measure of implant stability would be beneficial to decision-making regarding the status of the bone anchorage around an implant. The Periotest device has been reported to provide such a measure, but the in vivo data are incomplete and inconclusive in support of this claim. The purpose of this study was to determine in an in vivo model the relationship between Periotest values (PTV), three different implant biomaterials, and torque to failure. A total of 79 screw-shape implants made of commericially pure titanium, titanium alloy, and HA-coated alloy were evaluated in the posterior maxillary and mandibular quadrants of six female baboons following healing for 3 to 4 months. At uncovering, the implants were tested with the Periotest device and torqued to failure using an electronic torque driver. Analysis of the PTV-biomaterial relationship revealed no significant difference among the implants based on the biomaterial (P = .7453). Analysis of PTV-torque revealed a significant relationship (P = .0117), however, the association between PTV and torque was not strong and does not explain 92% of the variation between the parameters (Pearson correlation .2823, R2 = .08).

Histomorphometric comparison of implant anchorage for two types of dental implants after 3 and 6 months' healing in baboon jaws.

STATEMENT OF PROBLEM: A complete understanding of dental implant prognosis requires better knowledge of the bone anatomy after implant healing. Such baseline data are necessary to compare against load-induced changes in anatomy. PURPOSE: The purpose of this article is to describe and compare measures of implant support (percentage [%] integration and percentage [%] bone area) for various implants in baboon jaws after healing times of 3 and 6 months. MATERIAL AND METHODS: Commercially pure titanium (cpTi) and titanium alloy (Ti-alloy) screw-shaped implants were placed in the posterior jaws of 9 female baboons after 2 months of postextraction healing. Specimens were harvested after 3 months (5 baboons: 8 cpTi, 7 Ti-alloy) and after 6 months (4 baboons: 8 cpTi, 8 Ti-alloy). Each implant provided 6 polished horizontal sections for data collection, which was accomplished from digitized images with the IMAGE analysis system (reliability at 1.6%). Three- and six-month data for each parameter were compared with the use of ANOVA (P<.01). RESULTS: The results revealed a significant increase in the % integration (cpTi 39.1 to 56.2; Ti-alloy 40.0 to 55.2) and the % bone area (cpTi 38.8 to 47.9; Ti-alloy 38.9 to 49.2) from 3 to 6 months for both implants. This significant increase was also true for comparisons by jaw for each implant material (P<.01 for overall and by jaw comparisons). CONCLUSION: A time-dependent increase in jawbone anchorage was measured in this nonhuman primate population, and it was shown that the 6-month maxillary data were comparable to the 3-month mandibular data. These results lend support to the clinical strategy of waiting longer to load implants in the maxilla.