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Biomedical subjects

R Maijer

Publications and source records attributed to R Maijer.

15 recordsLinked to original sources
PubMed1993

Pressurized infusion of sodium hyaluronate for closed lock of the temporomandibular joint. Part I: A case study.

Patients with temporomandibular joint disorders (TMD) report a myriad of problems including headaches, facial pain, limited mouth opening capacity, and clicking and/or grating sounds from the temporomandibular joints. Although conservative therapy with an occlusal splint can bring relief for many of these patients, a small number of subjects must be treated by means of surgical procedures. Direct injections of either air or fluids (saline, local anesthetic, corticosteroid, hyaluronate) into the superior and/or inferior temporomandibular joint (TMJ) cavities have gained popularity. The injection of a local anesthetic and hyaluronic acid can provide relief for patients with persistent, painful nontranslatory closed-lock conditions of the TMJs. As documented through objective electronic and computer-enhanced measurements, this case report describes the effect of sodium hyaluronate on a closed lock condition of the TMJ. This case report explains the methodology employed for a larger group of closed lock patients treated and monitored for over one year. The results of that larger group will be reported at a later time after long-term efficacy is confirmed.

Adult↗
PubMed1988

A comparison between zinc phosphate and glass ionomer cement in orthodontics.

In the past orthodontic band cementation has relied heavily on mechanically retentive cements such as zinc phosphate luting agents. The clinical performance of a glass ionomer cement (GIC), a chemically retentive cement, was evaluated against a conventional zinc phosphate cement (ZP). The recementation values for ZP were significantly higher over a 2-year treatment period than those of GIC. Failures between cement and enamel, and cement and stainless steel were noted for the ZP. Glass ionomer cement had significantly better retentive strength to enamel than to band material. Moisture contamination does not appear to be a problem in orthodontic band cementation with glass ionomer cement.

Cementation↗
PubMed1986

Crystal growth on the outer enamel surface--an alternative to acid etching.

Over the past 2 years an increasing concern has developed about the possible iatrogenic effects of phosphoric acid-etch bonding techniques on the enamel surface. There is an evident need to develop a mechanical or chemical retention system that would not alter (or would minimally alter) the outer enamel surface. An alternative to the conventional phosphoric acid etch technique has been developed. A preliminary clinical trial showed promising performance under normal clinical conditions. These results were achieved with a minimal loss of surface enamel as evidenced by scanning electron microscopy. Debonding and cleanup were greatly facilitated. Creating a micromechanical retentive surface by the formation of a crystalline interface is a potential alternative to phosphoric acid etching.

Acid Etching, Dental↗
PubMed1986

Biodegradation of the orthodontic bracket system.

Corrosion of the orthodontic appliance may occur in vivo with time. Electrochemical breakdown of corrosion-resistant high nickel and titanium wire can also occur. The use of recycled brackets could possibly accelerate the corrosion process. New and recycled brackets were evaluated in vitro in an artificial saliva system. The results indicated that different brands of new brackets have differences in corrosion behavior. In addition, recycling by the three commercial processes tested increased the liability of brackets to undergo corrosion. Superior behavior was noted for two types of bracket bases. Bracket corrosion may be assessed by a simple in vitro test.

Biodegradation, Environmental↗
PubMed1983

Improvements in bracket base design.

Acid etch bonding of orthodontic attachments to the labial and lingual surfaces of teeth is generally adequate for clinical service. Failures do occur, and these are related to technique problems in acid etching or resin manipulation or to bracket base design. The widely used foil mesh base can present problems in retention because of design defects or corrosion. Improvement in mechanical retention of resin to the attachment base would result in significant improvements in bonding and fewer clinical failures. One of our approaches to improved retention is to fuse metallic or ceramic particles onto the bracket base so as to achieve a particulate or porous layer into which resin can penetrate. The results of bond-strength tests showed that a 100 percent increase in bond strength could be obtained with sintered porous metal-coated brackets. Further development is proceeding.

Animals↗
PubMed1982

Corrosion of orthodontic bracket bases.

Attention has recently been focused on the development of black and green stains in association with directly bonded stainless steel brackets. Twelve clinical cases of staining were studied in this investigation. After intraoral photography of the stains, the brackets were removed for examination with the scanning electron microscope. Multiple voids were observed at the resin-bracket interface, especially at the periphery. Considerable deterioration of the alloy base and mesh structure was observed in the void areas. Preliminary analysis of the stains showed that chromium compounds were present. The findings suggested that the presence of voids, together with poor oral hygiene, led to crevice corrosion of the Type 304 stainless steel and formation of colored corrosion products which can result in enamel stains. The use of stainless steels of improved corrosion resistance is recommended to overcome this problem.

Chemical Phenomena↗
PubMed1981

Variables influencing the bond strength of metal orthodontic bracket bases.

The purpose of this study was to examine the retention variables that exist between commercially available bracket bases. Premolar bracket bases from seven manufacturers were examined in the scanning electron microscope (SEM) as received. They were then bonded to human premolars with Dynabond and, after storage in water for 24 hours, tested to failure in shear. The bond-fracture surfaces were also examined in the SEM. Comparison of the SEM observations and shear strength data led to the following conclusions: (1) Weld spots reduce the retentive area. (2) Weld spurs could be responsible for lower bond strengths in some foil-mesh samples. (3) Weld spots on the edges of attachment bases should be avoided to prevent a poor marginal resin-mesh seal. (4) Bracket bases should be designed to prevent air entrapment under the base. (5) The best resin penetration and bond strength were obtained with a fine mesh bracket base of the woven mesh type.

Adhesives↗
PubMed1979

A new surface treatment for bonding.

Bonding resins to enamel requires some form of mechanical attachment. Currently the dissolution of the outermost enamel layer is involved in etching with phosphoric acid. A new approach to mechanical bonding is described using a crystalline interface which itself bonds chemically to enamel. The crystals can be removed from the enamel with an ultrasonci or sickle-scaler followed by pumice prophylaxis. Many variations of the crystal growth principle may be visualized, including the development of fluoride-containing crystals.

Acrylates↗