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Orthopedic coordination of dentofacial development in skeletal Class II malocclusion in conjunction with edgewise therapy. Part I.

The skeletal Class II malocclusion may be considered to develop as a failure of the coordinating process to maintain harmonious relationships within the developing dentofacial apparatus. If the skeletal elements are too far apart for adaptation to occur and/or if there are functional abnormalities of the orofacial musculature which inhibit coordination from taking place, a malocclusion will result. An orthopedic technique and appliance system has been developed with the intention of improving those factors responsible for the development and perpetuation of the skeletal Class II malocclusion in a primary stage of treatment. This is accomplished by means of restraint and redirection of forward maxillary growth and an increase in the velocity of mandibular growth. Concurrently, adverse soft-tissue influences are eliminated or ameliorated. Edgewise appliance therapy is subsequently carried out for the final correction. The subject is considered in two articles. This first article describes the effects of the restraint of maxillary growth on craniofacial development and the dental changes produced by a maxillary removable splint with extraoral traction and shows how they can be used clinically for correction of the skeletal Class II malocclusion. The experimental and clinical evidence supporting this approach is considered, and case histories show the clinical use of the maxillary splint. This form of maxillary therapy for the skeletal Class II malocclusion has limitations, and it is desirable for it to be incorporated into a comprehensive orthopedic system.

Cephalometry↗

Lacrimo-auriculo-dento-digital syndrome. Case report, review of the literature, and clinical spectrum.

Lacrimo-auriculo-dento-digital (LADD) syndrome, also known as Levy-Hollister syndrome, is characterized by pronounced dysplasias in various organ systems. The resulting disturbances affect primarily the lacrimal glands, the inner and outer ear, the salivary glands, and the osseous framework. Although the degree to which the different organs are involved varies considerably, dental anomalies are regularly reported. An autosomal-dominant trait has been recognized for this syndrome, but the majority of cases described in the literature concerned sporadic new mutations. We report on this unusual and relatively unknown syndrome with reference to a 13-year-old girl suffering from LADD syndrome presenting symptoms of severe xerostomia and various craniofacial malformations, hearing loss, enamel dysplasia, microdontia, and hypodontia.

Abnormalities, Multiple↗

Immunochemical and immunohistochemical study of the 27- and 29-kDa calcium-binding proteins and related proteins in the porcine tooth germ.

Our previous report identified 27- and 29-kDa calcium-binding proteins in porcine immature dental enamel. In this study we revealed that the N-terminal amino acid sequences of the two proteins were identical: LLANPXGXIPNLARGPAGRSRGPPG. The sequence matches a portion of the amino acid sequence of the porcine sheath protein, sheathlin. Porcine tooth germs were investigated immunochemically and immunohistochemically using specific antibodies raised against synthetic peptide that included residues 13-25 of this sequence. The affinity-purified antibodies reacted with several proteins extracted from newly formed immature enamel in immunochemical analyses, especially protein bands migrating at 62, 35-45, 29, and 27 kDa in SDS-polyacrylamide gels. The largest protein detected was a weak band near 70 kDa. In immunochemical analyses of proteins extracted from the inner (old) immature enamel, the antibody reacted faintly with the 27- and 29-kDa proteins. In immunohistochemical preparations, the Golgi apparatus and secretory granules of the secretory ameloblast, and the surface layer of immature enamel showed immunoreactivity. The immunoreactivity of immature enamel just beneath the secretory face of the Tomes' process was intense. No immunoreactivity was found in the Golgi apparatus of the maturation ameloblast. These results suggest that the 70-kDa protein, whose degradation might be very fast, is the parent protein of the 27- and 29-kDa proteins.

Ameloblasts↗

Root surface smoothness or roughness following open debridement. An in vivo study.

Consensus has not been reached on the desired characteristics of the root surface following cleaning. It is also not clear what degree of roughness or smoothness results from use of different instruments. In the present human clinical study, various instruments for root surface cleaning were evaluated. 18 teeth destined for extraction for periodontal reasons were utilized. After reflection of soft tissue flaps, the 72 root surface aspects of the 18 teeth were uniformally treated with one of the following instruments: Gracey curette (GC), piezo ultrasonic scaler (PUS), Perioplaner curette (PPC), sonic scaler (SS), 75 microns diamond (75 D) and 15 microns diamond (15.D). The degree of roughness of each surface was measured after extraction. A planimetry apparatus was used to establish the average surface roughness (Ra) and the mean depth of the roughness profile (Rz). It was demonstrated that hand- and machine-driven curettes as well as very fine rotating diamonds created the smoothest root surfaces, while "vibrating" instruments such as sonic and ultrasonic scalers, as well as coarse diamonds, tended to roughen the root surface. Whether the root surface should be rough or smooth in order to enhance tissue healing remains an open question.

Dental High-Speed Equipment↗

Sheath proteins: synthesis, secretion, degradation and fate in forming enamel.

We investigated expression of ameloblastin and sheathlin, recently cloned enamel matrix proteins from the rat and pig, in forming enamel immunocytochemically and immunochemically, using region-specific antibodies. The results obtained from the rat and pig were essentially the same. Antibodies which recognize the N-terminal region stained the secretory machinery of the secretory ameloblast and the entire thickness of the enamel matrix, especially the peripheral region of the enamel rod. Immunostained protein bands were observed near 65 or 70 kDa and below 20 kDa. C-terminal-specific antibodies stained the secretory machinery of the ameloblast and the immature enamel adjacent to the secretion sites. Immunostained protein bands were found ranging from 25 to 70 kDa. Antibodies which recognize a region in the protein just prior to the C-terminal region stained the cis-side of the Golgi apparatus but not the enamel matrix. Immunostained protein bands were observed of about 55 kDa. These results suggest that post-translational and post-secretory modifications of ameloblastin and sheathlin are similar to each other, and further showed that their cleaved N-terminal polypeptides concentrate in the prism sheath. We propose that sheathlin and ameloblastin share the same role in amelogenesis and should be classified as sheath proteins.

Animals↗

Clinical and laboratory evaluation of powered electric toothbrushes: laboratory determination of relative abrasion of three powered toothbrushes.

Previously established data on average forces applied to various brushing instruments during in vivo toothbrushing were incorporated into a laboratory abrasion model. The apparatus included a specially constructed and standardized brushing machine and utilized an acrylic resin substrate. Three powered brushing instruments (Rota-dent, Interplak and Braun Oral-B Plaque Remover) and a manual toothbrush (Oral-B P40), were compared in this model. The system demonstrated excellent precision and could distinguish between brushing instruments with as little as 10% difference in abrasivity. It was found that brushing abrasivity increased in the order of Rota-dent < Braun < Interplak.

Acrylic Resins↗

Minimizing dentinal fluid flow associated with gap formation.

The relationship between gap formation and outward fluid flow and procedures to minimize both phenomena were investigated in extracted human premolars restored in vitro with MOD composite restorations. We hypothesized that either glass-ionomer cement (GIC) liners or low-shrinkage composite could reduce fluid flow related to gap formation. Two groups restored with bonding agents with either high- or low-shrinkage resin composites, and 2 groups restored by either conventional or light-cured GIC liner plus resin composite were compared (8 teeth/group). Fluid flow was measured with an automated apparatus. Baseline fluid flow was low and unchanged after bonding, but increased sharply (though transiently) after teeth were lined with GIC. Outward flow was significantly greater with conventional than with light-cured GIC. Inward fluid flow occurred during light-curing, followed by extensive, prolonged outward flow after curing. Low-shrinkage composite or GIC liners reduced gap formation and limited outward fluid flow. GIC liners promoted outward fluid flow during their setting reactions.

Analysis of Variance↗

The ex vivo effect of ligation technique on the static frictional resistance of stainless steel brackets and archwires.

This ex vivo investigation compared the effect of various orthodontic ligation techniques on the static frictional resistance of stainless steel brackets and archwires under both dry and wet conditions. The techniques studied were: elastomeric modules tied conventionally and in a 'figure of 8' pattern, stainless steel ligatures, and Teflon-coated ligatures. The first part of the investigation involved the construction of calibration curves for each of the materials, so an estimate of the normal force exerted by the ligatures could be ascertained. Secondly, a pair of ligature locking pliers were modified so that ligatures could be placed with a standardized force. Finally, the four methods of ligation were directly compared on a specially constructed testing apparatus. Results revealed that elastomeric modules tied in a 'figure of 8' pattern produced significantly more friction than any other method tested, under both dry and wet conditions. No significant differences in frictional resistance were found between conventionally tied elastomeric modules and stainless steel ligatures. Teflon-coated ligatures, however, were associated with the lowest frictional forces. The results of the calibration tests indicated that the normal forces exerted by all four methods of ligation may be higher than previously estimated.

Calibration↗

Determining the slow crack growth parameter and Weibull two-parameter estimates of bilaminate disks by constant displacement-rate flexural testing.

OBJECTIVES: This study examined the influence of displacement-rate and relative layer heights (RLH) on the slow crack growth exponent and Weibull two-parameter estimates of bilayered ceramic composite disks composed of In-Ceram Alumina and Vitadur Alpha porcelain. METHODS: Equibiaxial disks were fabricated with RLH of 1:2, 1:1 and 2:1, for In-Ceram Alumina and Vitadur Alpha porcelain, respectively. Ninety specimens each (30 1:2, 30 1:1, and 30 2:1) were tested in an equibiaxial ring-on-ring testing apparatus at displacement-rates of 0.127, 1.27 and 12.7 mm min(-1). RESULTS: Weibull parameters were statistically significantly affected by changes in RLH at a constant displacement-rate and the slow crack growth parameters were significantly affected by RLH. Many specimens exhibited nonbrittle failure modes. Nonbrittle failures usually exhibited a fall, followed by a rise in load prior to catastrophic failure, and most occurred in specimens with thicker cores at low displacement-rates. SIGNIFICANCE: Geometries of layered materials may affect their reliability and longevity.

Aluminum Oxide↗

Regenerative periodontal therapy.

Regenerative periodontal therapy comprises procedures which are specially designed to restore parts of the tooth supporting apparatus which have been lost due to periodontitis. A procedure must fulfill certain criteria to be considered a therapy which encourages regeneration. This paper discusses a variety of surgical approaches including root surface conditioning, the placement of bone garfts or bone substitute implants and the use of organic or synthetic barrier membranes (GTR). Evidence is presented that regenerative surgery utilising the GTR principle fulfills all the criteria required of a surgical procedure to be considered a procedure leading to periodontal regeneration.

Animals↗

Protein and mineral release during in vitro demineralization of bovine dentine.

Intact bovine dentine specimens were partially demineralized using 100 mM acetic acid (pH 4.5 or 5.0) at room temperature. Mineral and protein release was measured. The experiments were performed in dissolution cells as well as in a flow dialysis apparatus previously described by Van der Linden et al. (1985). The average demineralization rates were approximately 1.5 times higher at pH 4.5 than at pH 5.0. No collagen release could be detected after one week of demineralization but about 50% of the non-collagenous proteins (NCP) were released during demineralization. This study showed that (1) a large fraction of NCP's is retained in dentine during demineralization and (2) that dentine collagen cannot be destroyed by acid alone.

Animals↗

Graphic assessment of interincisal point movements during chewing of hard and soft foods.

Interincisal point movements in 35 healthy, dentate subjects were investigated with an electrognathic apparatus. The main focus of the study was to find the average values of determined point graphic assessment in frontal and sagittal planes during chewing of hard and soft foods. However, as this was insufficient to obtain information on areas where occlusal contacts were reached, border movement envelopes were also recorded to obtain indirect information in connection to the previous task. The results showed that the graphic assessment form of mandibular movements was dependent on the consistency of the food that was chewed.

Adult↗

Ultrastructure of the human enamel organ. II. Internal enamel epithelium, preameloblasts, and secretory ameloblasts.

The fine structure of internal enamel epithelium, preameloblasts and secretory ameloblasts in primary tooth germs (bell stage) from four human foetuses was investigated. The characteristics of the differentiation of internal enamel epithelium via preameloblasts to secretory ameloblasts are described. The internal enamel epithelium consists of a row of low differentiated prismatic cells separated from the dental papilla by a distinct even basal lamina. In the preameloblasts the rough endoplasmic reticulum cisterns and mitochondria increase in number, the Golgi complexes become extensive and take up a distal position, and secretory granules are formed. Furthermore, the basal lamina is removed by coated vesicles, and proximally and distally in the cells a complex of zonulae adhaerentes, terminal webs and gap junctions is formed. The secretory ameloblasts make up a layer of highly differentiated cells demonstrating typical merocrine secretion.

Ameloblasts↗

Parameter on systemic conditions affected by periodontal diseases. American Academy of Periodontology.

The American Academy of Periodontology has developed the following parameter on systemic conditions affected by periodontal diseases. It is well known that systemic conditions may affect the onset, progression, and treatment of such diseases (see Parameter on Periodontitis Associated With Systemic Conditions, pages 876-879). The concept of periodontal diseases as localized entities affecting only the teeth and supporting apparatus is increasingly being questioned. Periodontal diseases may have widespread systemic effects. While these effects may be limited in some individuals, periodontal infections may significantly impact systemic health in others, and may serve as risk indicators for certain systemic diseases or conditions. As part of the approach to establishing and maintaining health, patients should be informed of the possible effects of periodontal infection on their overall well-being. Given this information, patients should then be able to make informed decisions regarding their periodontal therapy.

Coronary Disease↗

Frictional resistances in stainless steel bracket-wire combinations with effects of vertical deflections.

This research evaluated the effects of different bracket-wire combinations and second-order deflections on kinetic friction. Thirteen different brackets, six with 0.018 x 0.025 inch slots and seven with 0.022 x 0.028-inch slots were evaluated with six different sizes and shapes of stainless steel orthodontic wire, i.e., 0.016, 0.016 x 0.022, 0.017 x 0.025, 0.018, 0.018 x 0.025 and 0.019 x 0.026 inch for four second order deflections of 0.00, 0.25, 0.50, and 0.75 mm. The wires were ligated into the brackets with elastomeric modules. Bracket movement was implemented by means of an Instron universal testing instrument (RMO, Denver, Colo.), and frictional forces were measured by a tension load cell and recorded on an X-Y recorder (Hewlett-Packard, Anaheim, Calif.). Second-order deflection was created by a specially designed and machined testing apparatus that allowed two alternate pairs of the four total brackets to be offset in increments of 0.25 mm. The kinetic frictional force increased for every bracket-wire combination tested as the second-order deflection increased. Friction also increased with an increase in wire size, whereas rectangular wires produced greater friction than round wires. Bracket designs that limited the force of ligation on the wire generated less friction at low second-order deflections (0.00 and 0.25 mm).

Dental Stress Analysis↗

[Investigations of sag-resistance of precious alloys for porcelain fusing. (Part 2) The effect of Fe, In, Sn addition on the distortion at high temperature of 85% Au alloys for porcelain fusing (author's transl)].

Fifteen alloys were prepared by adding 0-1.00 wt% Fe, In and Sn (total amount 1.00 wt%) to 85 Au-10 Pd-5 Pt master alloy. The distortion at high temperature in the firing cycle was measured by the apparatus for trial manufacture reported in the preceding paper, and the influence of each additional elements was discussed. The results were summarized as follows; 1) The distortion of the alloys containing additional elements (Fe, In and/or Sn) was obviously less than that of the master alloy. 2) The distortion of the alloys containing only 1 wt% Fe was the least in all of the alloys. 3) Adding both In and Sn had tendency to less distortion at high temperature, but the adding effect was less than that of Fe.

Chemical Phenomena↗

In vitro wear assessment of titanium alloy teeth.

PURPOSE: Wear of commercially pure (CP) titanium prosthetic teeth has frequently been observed. The greatest wear has been found when the same grades of CP titanium are used for both maxillary and mandibular teeth. This study examined the wear behavior of teeth made with cast titanium alloy and compared these results with those for CP titanium and gold alloy teeth. MATERIALS AND METHODS: All tooth specimens were cast with grade 3 alpha titanium, 3 metastable beta alloys [Ti-15Mo-2.8Nb-0.2Si (Timetal 21 SRx), Ti-13Nb-13Zr, and Ti-15V-3Cr-3Sn-3Al], and 2 alpha+beta alloys (Ti-6Al-7Nb and Ti-6Al-4V). As a control, Type IV gold alloy was also cast conventionally. All teeth (both maxillary and mandibular) were secured in an in vitro 2-body wear testing apparatus that simulated chewing function (60 strokes/min; grinding distance, 2 mm under flowing water). Wear resistance was assessed as volume loss (mm(3)) at 5 kgf (grinding force) after 50,000 strokes. The results (n = 5) were analyzed using analysis of variance or Fisher's exact test (alpha = 0.05). RESULTS: Of the titanium teeth, the wear of 2 of the metastable beta alloys (Timetal 21 SRx and Ti-15V-3Cr-3Sn-3Al) was found to be significantly (p <0.05) higher than that of CP titanium and the 2 alpha+beta alloys. The Type IV gold alloy exhibited better wear resistance than all of the titanium teeth tested. No correlation was found between wear loss and hardness among all the metals tested. CONCLUSIONS: Among the titanium teeth examined, the alpha+beta alloys exhibited significantly less wear than the other types of titanium. The dental casting gold alloy tested exhibited the best wear resistance among all of the metals tested.

Alloys↗

[Influence of interocclusal distance of mandibular unilateral distal extension removable partial denture on masticatory function].

The purpose of this study was to elucidate the influence on masticatory function when the mandibular unilateral distal extension removable partial denture changed the interocclusal distance. The experiments, crushability, the sense of mastication, and the masticatory strokes until swallowing, were conducted, on four subjects, using the denture with the apparatus that enabled to change the interocclusal distance. The results were as follows: The particle size distribution showed that the ratio of small particle (diameter 2.5-4.5 mm) decreased, while that of large particle (more than 5.0 mm) increased, on three of four subjects, and the value of crushability diminished. A reduction of the value of crushability when the interocclusal distance was extended more than 800 microns was found. As for the other subject, no change was recognized on the particle size distribution under experimental condition, and the value of crushability showed no significant change.

Dental Occlusion↗