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Biomedical subjects

Peter E Larsen

Publications and source records attributed to Peter E Larsen.

8 recordsLinked to original sources
PubMed2006

Heat production by 3 implant drill systems after repeated drilling and sterilization.

PURPOSE: The goal was to measure heat generated in bone by 3 implant drill systems after repeated drilling and sterilization. MATERIALS AND METHODS: Temperature was measured with thermocouple technology in vitro using the bovine femoral cortical bone model. Intermittent drilling was accomplished at a constant 2.4-kg load and drill speed of 2,500 rpm. External irrigation at 40 mL/min with normal saline was used. Three implant drill systems-system A (triple twist drills with a relief angle), system B (triple twist drills without a relief angle), and system C (double twist drills with a relief angle)-were evaluated and heat was measured at the final drill in the drilling sequence (4.0 mm or 4.2 mm) at a depth of 15 mm. Thermocouples were placed 0.5 mm from the osteotomy at a depth of 15 mm. Heat measurements were recorded out to 25 uses. RESULTS: Results showed temperature increased with multiple uses. System A and C drills had temperature measurements that were below 47 degrees C, even after 25 uses. System B drills had temperatures that exceeded 47 degrees C from the initial use. Light microscopy showed little drill wear even after 25 uses. CONCLUSIONS: Drill geometry plays a major role in heat production and may explain the increased temperature readings seen in system B. These drills lack relief angles and have the smallest clearance angles of the 3 systems. It also has fewer drills in its drilling sequence compared with systems A and C. This study shows that temperatures increase when drills are used multiple times. Systems A and C had acceptable temperature measurements out to 25 uses. System B drills showed significantly higher heat production with little visual signs of wear.

Animals↗
PubMed2006

Effect of alendronate on endosseous implant integration: an in vivo study in rabbits.

PURPOSE: Alendronate sodium (Fosamax; Merck, Whitehouse Station, NJ) is a second-generation bisphosphonate used widely in osteopenic individuals for decreasing bone resorption and increasing bone density. The ability of alendronate to affect systemic bone remodeling raises natural questions about the drug's influence on dental implant osseointegration. Current knowledge regarding the effect of systemic bisphosphonates, specifically alendronate, on all 3 phrases of osseointegration is incomplete and only a few studies have started to investigate peri-implant bone responses to alendronate-coated implants. The purpose of this study was to determine the effect of systemic alendronate therapy on osseointegration of dental implants based on torque-removal values in rabbits. MATERIALS AND METHODS: Identical titanium dental implants were placed using a standardized surgical protocol in the bilateral distal femur and proximal tibia of 20 New Zealand white rabbits (79 implants total). One week before implant placement, 10 rabbits were given doses of alendronate and continued on weekly dosing for 5 weeks until euthanized. The other 10 rabbits were untreated controls. Torque-removal values were determined using a Tohinichi 15-BTG torque wrench (Tohinichi Mfg Co, Ltd, Tokyo, Japan) for all implants. RESULTS: Analysis of torque data showed no statistical differences between the alendronate and control groups in both femur and tibia sites. A statistically significant difference, however, was noted in torque removal values between femur and tibia sites regardless of drug or non-drug groups. CONCLUSIONS: In summary, orally dosed alendronate administration in rabbits had no significant effect on dental implant torque-removal values 6 weeks after endosseous placement in femur and tibia.

Alendronate↗
PubMed2006

Suppression of the tumorigenic phenotype in human oral squamous cell carcinoma cells by an ethanol extract derived from freeze-dried black raspberries.

Despite focused efforts to improve therapy, 5-yr survival rates for persons with advanced-stage oral squamous cell carcinoma (SCC) remain discouragingly low. Clearly, early detection combined with strategies for local intervention, such as chemoprevention prior to SCC development, could dramatically improve clinical outcomes. Previously conducted oral cavity human chemoprevention trials, however, have provided mixed results. Although some therapies showed efficacy, they were often accompanied by either significant toxicities or circulating antiadenoviral antibodies. It is clearly apparent that identification of nontoxic, effective treatments is essential to prevent malignant transformation of oral epithelial dysplasias. This study employed cell lines isolated from human oral SCC tumors to investigate the effects of a freeze-dried black raspberry ethanol extract (RO-ET) on cellular growth characteristics often associated with a transformed phenotype such as sustained proliferation, induction of angiogenesis, and production of high levels of reactive species. Our results demonstrate that RO-ET suppresses cell proliferation without perturbing viability, inhibits translation of the complete angiogenic cytokine vascular endothelial growth factor, suppresses nitric oxide synthase activity, and induces both apoptosis and terminal differentiation. These data imply that RO-ET is a promising candidate for use as a chemopreventive agent in persons with oral epithelial dysplasia.

Adult↗
PubMed2005

Pull-out strength of monocortical screws placed in the maxillae and mandibles of dogs.

BACKGROUND: Mini-implants can facilitate orthodontic tooth movement by serving as anchors. The purpose of this investigation was to determine whether the pull-out strength of screws in bone varies depending on the site of insertion in the maxilla or the mandible. MATERIALS: Fifty-six titanium screws (2 mm diameter, 6 mm length, Synthes USA, Monument, Colo) were placed in 4 beagle dogs (14 screws per dog) within 30 minutes after they were killed. The screws were inserted to obtain monocortical anchorage, at predetermined sites in the anterior, middle, and posterior regions of the jaws bilaterally. Two screws were placed in the posterior palate in each dog. The jaws were harvested, and bone blocks, each containing a screw, were prepared for mechanical testing. The bone/screw block was aligned on a custom-made fixture, and the maximum force (F max ) at pullout was recorded. Cortical bone thickness was measured after extraction of the screw. Statistical analyses to test for differences were conducted with ANOVA and Tukey-Kramer tests. RESULTS: Screws placed in the anterior mandibular region had significantly ( P < .05) lower F max (134.5 +/- 24N, mean +/- SE) than those placed in the posterior mandibular region (388.3 +/- 23.1N). Regression analyses suggested a weak (r = 0.39, P = .02) but significant correlation between F max and cortical bone thickness. CONCLUSIONS: The bone supporting monocortical screws would most likely withstand immediate loading and support tooth-moving forces.

Analysis of Variance↗
PubMed2005

A comparison of providers' and consumers' perceptions of facial-profile attractiveness.

INTRODUCTION: The purpose of this study was to evaluate the perception of facial attractiveness in profile digital photographs that were incrementally altered to produce different combinations of mandibular anteroposterior positions and lower anterior facial heights. The specific aims were to determine whether there is concordance between providers and consumers in their perceptions of facial attractiveness, and to evaluate whether interactions of the anteroposterior and vertical dimensions and the magnitude of these interactions influence perception of facial attractiveness. METHODS: Profile digital photographs and cephalograms of 3 men and 3 women were used. The position of the jaw was altered incrementally with Dolphin imaging equipment (Dolphin Imaging and Management, Chatsworth, Calif), and booklets were created. One hundred raters (50 laypersons, 25 oral surgeons, 25 orthodontists) scored the profiles on a visual analog scale. All images were duplicated to test intrarater reliability. Factorial ANOVA with repeated measures and the Tukey-Kramer post-hoc test for multiple comparisons were used to test for differences in facial attractiveness. The level of significance was set at .05 (P = .05) for all analyses. RESULTS: Intrarater reliability was good (ICC = 0.71), and general concordance was found between providers and consumers in their perceptions of facial attractiveness. Interactions of the anteroposterior and vertical dimensions and the magnitude of change in each dimension influence the perception of facial attractiveness. CONCLUSIONS: The results suggest that preferences of facial attractiveness by laypersons, orthodontists, and oral surgeons in central Ohio are generally in agreement. This information might assist clinicians in treatment planning and making recommendations.

Adolescent↗
PubMedDate not supplied

Prospective study of 429 hydroxyapatite-coated cylindric omniloc implants placed in 121 patients.

PURPOSE: Controversy over the long-term clinical effectiveness of hydroxyapatite (HA)-coated dental implants still persists, despite numerous clinical studies documenting high survival rates. The Ohio State University College of Dentistry undertook a 5-year prospective study of 429 HA-coated cylindric implants placed into 121 patients to determine the long-term clinical performance of the implants. MATERIALS AND METHODS: All study subjects were patients screened and evaluated in the university's dental clinic by one of the principal investigators and one member of the surgical team. A total of 429 HA-coated implants were placed in 121 patients. The Ohio State University Human Subjects Committee approved and reviewed this study. RESULTS: At the time of this report, 375 implants had completed 5 years of clinical follow-up. Beyond the 5-year limit of the study, 282 implants had completed 6 years and 114 implants had completed 7 years of clinical monitoring. The cumulative survival rate was 96% at 5 years and 95% at 7 years of follow-up. Mean combined mesial/distal bone loss was 1.2 mm in the mandible and 1.4 mm in the maxilla after 5 years of functional loading. Implant failures were most commonly associated with short implants or angled abutments. DISCUSSION: Prospective clinical data are extremely valuable for clinicians evaluating the reliability of dental implant systems. In the present study, the implants achieved 100% osseointegration with minimal marginal bone loss, and 96% of the implants remained in function at 5 years. CONCLUSION: The HA-coated cylindric implants in this study provided a predictable means of oral rehabilitation.

Adolescent↗