Differences in bonding to acid-etched or Er:YAG-laser-treated enamel and dentin surfaces.

STATEMENT OF PROBLEM: Er:YAG (erbium-doped yttrium aluminium garnet) lasers have been effective in the removal of dental tissues. It has been suggested that they are also useful for preparing dental surfaces for adhesion, but results to date have been controversial. PURPOSE: This study compared the tensile strength of bracket-tooth bonds obtained after preparation of the surface for adhesion (dentin or enamel) by conventional acid-etching or by Er:YAG laser etching and investigated microstructure of resin-tooth interfaces using the 2 procedures. MATERIAL AND METHODS: Eighty healthy human premolars were used. Brackets were cemented to acid-etched enamel, laser-etched enamel, acid-etched dentin, or laser-etched dentin (20 teeth per group). Dentin was previously exposed using a high-speed handpiece. Acid-etching was with 37% orthophosphoric acid (15 seconds for enamel, 5 seconds for dentin). Laser etching was with Er:YAG laser (four 200 mJ pulses per second for enamel; four 160 mJ pulses per second for dentin). Brackets were bonded with autocuring resin paste, having first applied a primer (dentin only) and then light-cured bonding resin. Tensile strength was determined with a universal testing machine. Data were analyzed with 2-way ANOVA and subsequent t test with Bonferroni correction. Fracture patterns were compared by the Wilcoxon test with Bonferroni correction. For SEM studies of the resin-tooth interface, a total of 12 premolars were used (3 for each tissue per treatment combination). RESULTS: Mean tensile bond strength for acid-etched enamel (14.05 +/- 5.03 MPa) was significantly higher (P<.05) than for laser-etched enamel (8.45 +/- 3.07 MPa), and significantly higher (P<.05) for acid-etched dentin (4.70 +/- 2.50 MPa) than laser-etched dentin (2.48 +/- 1.94 MPa). Bond failure after laser etching was due to microcohesive fracture of tooth tissue. SEM studies of both resin-enamel and resin-dentin interfaces indicated extensive subsurface fissuring after laser etching. CONCLUSION: Adhesion to dental hard tissues after Er:YAG laser etching is inferior to that obtained after conventional acid etching. Enamel and dentin surfaces prepared by Er:YAG laser etching show extensive subsurface fissuring that is unfavorable to adhesion.

A secure method for making removable dies.

Removable dies greatly facilitate fixed prosthesis fabrication and accurate marginal fit. The major difficulty when using removable dies is the correct positioning of the dowel pin in the stone base. This article describes a method for preparing removable dies that ensures accurate positioning of the dowel pin and provides external landmarks for precise location of the cuts to be made with the die saw. The method described is accurate, simple, inexpensive and can be performed in the dental laboratory.

Simple method for articulator mounting of mandibular diagnostic casts.

The method described in this article is inexpensive, simple, and rapid and can be performed by a single operator. There is no risk of the rubber bands slipping, because they are included within the stone itself.

The occlusal plane indicator: a new device for determining the inclination of the occlusal plane.

Accurate determination of the inclination of the occlusal plane is important in a number of situations, and includes confirming the correct development of the dentition in children, providing a basis for nonanatomic tooth design in the preparation of fixed prostheses, and assisting in decisions as to whether to perform intrusions or extrusions. This article describes a simple device for determination of the inclination of the occlusal plane.

[Anomalies of the inclination of the occlusal plane: early treatment using indirect guide-planes--electromyographic response]. / Anomalies d'inclinaison du plan occlusal: traitement précoce par les pistes indirectes--réponse électromyographique.

We discuss five cases of ANGLE's malocclusion Classes I, II or III that were rehabilitated basically by: restoration of masticatory function (previously pathological); the use of removable orthopaedic plates with indirect guideplanes. The patients (aged 6-15 years when treatment began) now have symmetrical balanced occlusion. Surface electromyography was used to study the function of the anterior temporal, surface masseter, deep masseter and anterior digastric muscles of 12 patients during rehabilitation of severe malocclusion. Electromyograms were obtained both with and without orthopaedic guideplanes installed. There were no significant differences as regards mean resting myoelectric activity. During maximum voluntary clenching in centric occlusion, the anterior temporal muscles were the most active, followed by the surface masseters. The activity of the anterior temporal muscles during clenching was significantly less (P < 0.01) with guideplanes than without. During lateral displacements, the non-working side anterior temporal muscle exhibited a significantly higher potential than the other muscles monitored, especially with guideplanes installed. The activity was lees with guideplanes during swallowing.

[Median inter-incisor line. Clinical symptomatology]. / Ligne médiane interincisive. Sémiologie clinique.

Since unilateral mastication causes asymmetry of mouth and face, a child's interincisal midline can reveal the first signs of alteration of masticatory function. Early detection of the functional pathology, preferably before it has established itself as such, allows the clinician to correct it by means that are relatively unburdensome for the patient, thereby forestalling severe organic alteration and favouring proper, balanced occlusal development. Centering the mandible in stable centric occlusion, together with simple treatment promoting alternating bilateral mastication, allows the correct development of the growing patient's stomatognathic system.