Biomedical subjects

David F Murchison

Publications and source records attributed to David F Murchison.

6 recordsLinked to original sources

PubMed2005

Oral surgical handpiece use time parameters.

PURPOSE: To evaluate the clinical usage time parameters of handpieces used in oral surgical procedures. METHOD AND MATERIALS: One hundred randomly selected clinical oral surgery exodontia procedures were timed to record lengths of continuous segments of both handpiece use and non-usage. Providers with experience ranging from general dentists to board certified oral surgeons were timed during surgical exodontia treatment involving 1 to 4 teeth of various complexities. Usage times were compared with manufacturers' recommendations that on times should not exceed 20 seconds in any 50-second interval (20/50 rule). RESULTS: Handpiece run time increased with the number of teeth and surgical case complexity (both P < .001) but was unrelated to operator experience (P = .763), in a 3-predictor model (R2 = 0.20; P < .001). Ninety-four of the 100 cases experienced at least 1 second in violation of the 20/50 rule and 42% of all run seconds were in violation. CONCLUSION: Clinicians should be aware of recommended handpiece duty use cycles. Manufacturers' recommendations about handpiece use time cycles do not reflect actual clinical usage. Under the conditions of this study, actual surgical handpiece use time was not correlated with user experience. Less experienced providers did require longer to complete treatment, but increased treatment times were due to time spent that did not require surgical handpiece use.

Clinical Competence↗

PubMed2002

Comparison of moist and dry heat penetration through orofacial tissues.

Application of superficial moist heat has been shown to have a beneficial effect on Temporomandibular Disorder (TMD) symptoms and is often recommended for patients with this disorder. A review of the literature shows that few studies have compared the effects of moist to dry heat. Throughout this study, moist and dry heat were applied through a commercial heating pad alternately for 20 minute intervals. The application sequence was randomized and all individuals received both moist and dry modalities. Intraoral and extraoral thermocouples were positioned on the mid-cheek area of 46 volunteers to record temperature readings. Dry and moist heat applications were equally effective in both maximum tissue temperature rise and the rate of thermal transfer (p> 0.05). However, in a small number of subjects moist heat was preferred. As there seems to be little difference between using moist rather than dry heat, patients may be counseled to employ the superficial heating option that: 1. is an individual's personal preference or 2. improves convenience and optimizes compliance.

Adult↗

PubMed2002

Higher-concentration carbamide peroxide effects on surface roughness of composites.

BACKGROUND: Ten percent carbamide peroxide has been used extensively within the dental profession for the purpose of bleaching teeth. Although this method has been successful, the use of higher-concentration carbamide peroxides (20-35%) for home bleaching has increased substantially in the past few years. The purpose of this study was to evaluate changes in surface roughness of a hybrid and a microfilled composite after exposure to bleaching agents containing higher concentrations of carbamide peroxide. MATERIALS AND METHODS: Sixty-eight circular, resin-based composite specimens (8 mm x 2 mm) were prepared against a Mylar surface. Half of the specimens were fabricated from a hybrid composite material and the other half with a microfilled composite. Specimens were polished with aluminum oxide finishing disks, divided into four groups, and then exposed either to 20% carbamide peroxide for 3 hours per day for 14 days or to 35% carbamide peroxide for 1 hour per day for 14 days. The mean surface roughness (Ra) was determined for each specimen before and after exposure to bleaching agents, using mechanical profilometry. Data were analyzed by two-way analysis of variance (ANOVA) for differences between composite type, carbamide peroxide concentrations, and interaction of the two factors with respect to average surface roughness. All data analysis was performed at alpha = 0.05. RESULTS: Mean change from baseline of surface roughness (Ra) of microfilled composite and 20% carbamide peroxide was -0.03 microm +/- 0.10 microm; microfilled composite and 35% carbamide peroxide: 0.01 microm x 0.02 microm; hybrid composite and 20% carbamide peroxide: -0.43 microm x 0.91 microm; hybrid composite and 35% carbamide peroxide: -0.19 microm x 0.43 microm. Surface roughness of hybrid or microfilled composite did not change significantly from baseline with either concentration of carbamide peroxide (p = .300). CLINICAL SIGNIFICANCE: Higher-concentration carbamide peroxide bleaching agents, used as intended by the manufacturer, pose no significant risk to resin composite restoration surfaces.

Aluminum Oxide↗

PubMedDate not supplied

Surface roughness of various packable composites.

Packable composite restorations have become a popular alternative to dental amalgam restorations in posterior teeth. A drawback inherent to composites is their difficulty in polishing, which often results in a dull or rough surface. This study compared the surface roughness of a resin-based hybrid composite material and five packable resin-based composites polished with either aluminum oxide disks or a rubber polishing system. Sixteen specimens of each of the six composite materials were polished with either Sof-Lex XT disks or Enhance rubber polishers followed by fine and superfine polishing pastes. The specimens were evaluated for surface roughness using surface profilometry. Mean values were calculated for each material type and method of polishing. Data were subjected to a two-way ANOVA. Post hoc comparison was accomplished using Tukey's HSD. No significant difference in surface roughness was detected among polishing techniques (p=0.067); however, a strong trend-that aluminum oxide disks provided a smoother surface than rubber polishers in five out of six materials-was noted.

Aluminum Oxide↗

PubMedDate not supplied

Fracture strength of amalgam crowns with repaired endodontic access.

Endodontic therapy is accessed occlusally in posterior teeth, many of which have large, pre-existing amalgam restorations. These teeth are also commonly restored with an occlusal amalgam to repair the access opening. This study determined the fracture resistance of complex amalgam restorations that have repaired endodontic access compared with original, unrepaired, complex amalgams on endodontically-treated teeth. Two groups of 30 molars were used in the study. The first group was decoronated and received an endodontic access preparation. These teeth were restored using chamber retention and four TMS pins. The second group was decoronated and restored using pin retention. Later, they received an endodontic access through the restoration. The access was then repaired with amalgam. The samples were loaded in an Instron Universal Testing Machine until failure. The Group 1 samples failed at a mean force of 2297.5 N. The mean failure load for the samples in Group 2 was 1586.1 N. Student's t-test found this difference to be statistically significant. Endodontic access through an amalgam crown significantly compromises the fracture strength of the original restoration.

Dental Alloys↗

PubMedDate not supplied

The effect of resin composite pins on the retention of class IV restorations.

Standardized Class IV cavity preparations were made in 48 human incisors. They were then divided into three groups of 16 teeth each. Group 1 was prepared with no internal retentive features. Groups 2 and 3 included an internal pin channel prepared with a #330 and a #329 bur, respectively. All specimens were restored with a micro-hybrid resin-based composite restorative material and a fifth generation dentin bonding system. Specimens were loaded to failure in an Instron Universal Testing Machine perpendicular to the long axis of the teeth. There was no evidence to suggest a difference in force required to dislodge the restoration among the three groups tested (p=0.185). Resin composite pins do not increase the retention of Class IV resin composite restorations.

Acid Etching, Dental↗