Amelogenesis imperfecta in a new animal model--a mutation in chromosome 5 (human 4q21).

Candidate genes for amelogenesis imperfecta (AI) and dentinogenesis imperfecta (DI) are located on 4q21 in humans. We tested our hypothesis that mutations in the portion of mouse chromosome 5 corresponding to human chromosome 4q21 would cause enamel and dentin abnormalities. Male C3H mice were injected with ethylnitrosourea (ENU). Within a dominant ENU mutagenesis screen, a mouse mutant was isolated with an abnormal tooth enamel (ATE) phenotype. The structure and ultrastructure of teeth were studied. The mutation was located on mouse chromosome 5 in an interval of 9 cM between markers D5Mit18 and D5Mit10. Homozygotic mutants showed total enamel aplasia with exposed dentinal tubules, while heterozygotic mutants showed a significant reduction in enamel width. Dentin of mutant mice showed a reduced content of mature collagen cross-links. We were able to demonstrate that a mutation on chromosome 5 corresponding to human chromosome 4q21 can cause amelogenesis imperfecta and changes in dentin composition.

Quantitation of arachidonic acid metabolites in small tissue biopsies by reversed-phase high-performance liquid chromatography.

Arachidonic acid metabolites exert a variety of distinct biological effects on the initiation and resolution of inflammatory diseases and their measurements in tissue can be critical to evaluate their regulatory function during the course of inflammation and to supplement in vitro experiments. The aim of this study was the detection and quantitative analysis of four arachidonic acid metabolites in small-sized biopsies of human periodontal tissues. The biopsies were homogenized and injected directly into a single analytical column of a RP-HPLC system. Detection was performed by a photodiode array detector. Calibration was established by dilutions of authentic standards of prostaglandin E2 (PGE2), leukotriene B4 (LTB4), 12(R)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), and 15(S)-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE). A total of 38 specimens weighing between 19 and 191 mg (wet tissue) were analyzed (mean = 59.9 +/- 30.2 mg). The detection limits were 1 pg for LTB4 and 12-HETE, 0.5 pg for 15-HETE, and 10 ng for PGE2. The concentrations of PGE2 and LTB4 were significantly higher in inflamed than in healthy periodontal tissues (P = 0.0079; P = 0. 0114). 12-HETE was detected in one biopsy (30 pg/g); 15-HETE was not detected. This method of homogenization, extraction, and analysis of arachidonic acid metabolites by RP-HPLC appears to be well suited for studies of human oral biopsies. Only small tissue samples and minimal laboratory equipment were required for a sensitive analysis.

Recombinant human osteogenic protein-1 induces dentin formation: an experimental study in miniature swine.

It was the aim of the present study to investigate the induction of dentin formation by recombinant human osteogenic protein-1 (hOP-1). In 4 adult miniature pigs a total of 16 teeth with artificially exposed dental pulps were capped with 3 mg of a complex of recombinant hOP-1 in collagen matrix (2.5 micrograms/mg), collagen matrix alone, or calcium hydroxide paste. Teeth were removed in block section after a healing period of 5 weeks. Decalcified sections were processed for light microscopy and histomorphometric analysis. In hOP-1 treated teeth substantial amounts of hard tissue formation (osteodentin and tubular dentin) had consistently led to a complete bridging of the defects. Less dentin formation was seen after calcium hydroxide application. In control defects collagen matrix alone failed to form complete dentin bridges. Recombinant human osteogenic protein-1 in a collagen carrier matrix appeared to be suitable as a bio-active capping agent for surgically exposed dental pulps.

Progressive peri-implantitis. Incidence and prediction of peri-implant attachment loss.

The aim of this prospective study was to characterize an implant patient population exhibiting clinical signs of peri-implantitis and to determine subsequently the incidence of progressive attachment loss. The predictive values of diagnostic parameters were evaluated. 25 patients with 54 endosseous implants that had been loaded for 41 +/- 15 months were included in the study. Clinical parameters included the assessment of plaque, bleeding on probing, probing depth, attachment levels, and Periotest values. Probing measurements were performed in duplicate by means of a controlled force electronic probe (Periprobe). Peri-implant crevicular fluid samples were collected and assayed for neutral proteolytic enzyme (NPE) activity (Periocheck). Analysis of duplicate baseline probing data revealed a high degree of reproducibility (mean difference: 0.1 +/- 0.3 mm). A minimum threshold of 1.0 mm (> 3 x S.D.) loss of probing attachment was chosen to classify a site as positive for breakdown. Alternatively, the tolerance method was employed to identify sites with progressive attachment loss. After 6 months, irrespective of the analytical method, 6 percent of all sites (in 19% of the implants) and 28% of the patients had experienced further peri-implant attachment loss. There were significant differences (p < 0.05) in mean plaque (73% vs. 45%) and NPE (36% vs. 12%) scores between patients with progressive peri-implantitis and those with stable peri-implant conditions. Both bleeding on probing and the NPE-test were characterized by high negative predictive values, and thus negative scores can serve as indicators for stable peri-implant conditions. For monitoring peri-implant health during recall visits, attachment level recordings with a controlled force electronic probe in conjunction with enzymatic diagnostic tests of the host response can be recommended.

[The effect of modified forms of preparation on the quality of SR Isosit composite inlay margins]. / Der Einfluss modifizierter Präparationsformen auf die Randqualität von Kompositinlays aus SR-Isosit.

Butt joint, plain and round beveled MOD cavities were prepared in extracted human molars. Composite resin inlays (SR-Isosit) were fixed adhesively and analysed by quantitative SEM-evaluation after thermocycling and mechanical load application. The marginal adaptation of the inlays differed significantly depending on the type of cavosurface preparation. Best results with a high percentage of perfect margins not only before but also after in vitro load application were obtained with cavities prepared with rounded bevels.

[Optimizing accuracy of Isosit IO composite restorations]. / Optimierung der Primärpassung von Komposit-Restaurationen aus Isosit IO.

Using a modified technique for producing composite inlays from Isosit IO resin material resulted in an optimized accuracy of inlays primary fit. SEM evaluation of MOD composite resin inlays manufactured by this technique and inserted on extracted teeth showed that the mean thickness of the luting composite space measured less than 50 microns.

[SEM study on finishing the joint between inlay and luting composite resin]. / REM-Untersuchungen zur Nacharbeitung der Befestigungskompositfunge adhäsiv zementierter Kompositinlays.

This in vitro study compared different methods of finishing luting composite resin spaces after insertion of composite resin inlays. SEM-evaluation revealed significant differences between the various finishing methods. Best results with high rates of perfect margins were obtained by use of twelve-fluted carbide burrs followed by surface polishing with silicone points.

[Animal experimental studies of treatment of bony periodontal pockets using hydroxyapatite]. / Tierexperimentelle Untersuchungen zur Behandlung von parodontalen Knochentaschen mit Hilfe von Hydroxylapatitkeramik.

The purpose of the present report was to evaluate the effect of a solide hydroxylapatite (HA) granulate implanted into artificial periodontal defects in 3 beagle dogs. In order to collect data about the type of periodontal wound healing blocksections were taken 3-6-12 months after implantation and evaluation by light microscopy. Three forms of tissue reaction in relation to the implants were observed: The first showed extraalveolar a fibrous connective tissue encapsulation of the HA-granulate, the second interalveolar an organized bone tissue around the implants, while in the third type of tissue reaction a deposit of mineralized tissue on the surface limited in width, was observed interpreted as cementum formation. In some cases the lost of cementum on the root surface was followed by a bone-like analysis. Analysis of the blocksections revealed new connective tissue attachment to a certain extent and bone/cementum-like tissue formation. But none of this tissue-formation can be calculated before implantation.

[Accuracy of fit and margins of laboratory-finished SR-Isosit composite inlays]. / Die Passgenauigkeit und Randdichte laborgefertigter Kompositinlays aus SR-Isosit.

30 inlays were produced exactly by manufactures instruction using the SR-Isosit composite. Before cementation the marginal gaps of the inlays extended to 280 microns occlusal resp. to 350 microns gingivoproximal. After insertion the thickness of the luting composite ranged from 40 to 400 microns occlusal resp. from 40 to 470 microns gingivoproximal. Dye penetration test indicated that only 43.7% of the inlays had a good marginal behaviour after storage in water over a six month period. Particularly remarkable was the insufficient junction between the luting composite and the highly polymerized inlay.

[SR Isosit composite inlays in a short term clinical test]. / Kompositinlays aus SR-Isosit im klinischen Kurzzeittest.

This in vivo study assessed the clinical behaviour and early cavomarginal breakdown of a total of 42 "SR-Isosit" composite inlay restorations. Indirect examination of replica models by means of stereomicroscope and SEM-analysis indicated a stepwise loss of marginal adaptation within the six month period of clinical use. Microfractures were most frequently found in inlay margins located on functional cusp sites, while the resin luting agent still remained in place on etched enamel.

[Cervico-approximal "Sofort" polishing of amalgam fillings. Optimizing filling quality]. / Die zerviko-approximale "Sofort politur" von Amalgamfüllungen. (Hinweise zur Optimierung der Füllungsqualität).

Results from SEM-evaluation indicates that finishing the gingivoproximal part of freshly restored amalgam restorations with interproximal finishing strips (fine and x-fine grits) produces an improvement in marginal integrity and surface smoothness. For clinical success the procedure requires both only moderate trimming of the proximal cavity margin and using a fast setting spherical alloy. In case of admixture or lathecut alloys the interproximal finishing within the first 25 minutes after trituration causes an unwelcome roughness of the restorations surface texture and is therefore contraindicated.

[Cementable and adhesive pulpal pins as alternatives to self-threading screws]. / Zementierbare und geklebte Parapulpärstifte als Alternative zu selbstschneidenden Schrauben.

Self-threading retentive pins are to be disputed in case of the possible dentinal damage in form of cracks and craze patterns. For a short time two new pin systems are offered on the german market. The essential retention shall be attained by cementing or otherwise by gluing in the pin channel. It is obvious that the promised elimination of cracking and crazing stands in opposition to a significantly reduced retention in the dentin, compared to self-threading systems. A general dispensation of self-threading pins is therefore not to be recommended.

[Optimizing marginal fit of amalgam restorations on the cervico-interproximal aspect]. / Optimierung des Randschlusses von Amlagamrestaurationen im zerviko-approximalen Bereich.

SEM studies were conducted to demonstrate that marginal fit and surface quality of cervico-interproximal amalgam fillings may be improved considerably by polishing the fresh filling with fine grain finishing paper. The time of finishing as a function of the amalgam used was crucial, while the method of plugging (manual or automatic) had very little influence on later finishing of the filling surface.

[Influence of self-tapping parapulpal posts on dentin structures]. / Der Einfluss gewindeschneidender parapulpärer Stiftsysteme auf die Dentinstruktur.

A combined light and scanning electron microscopic study in human molars examined the effects of seven different parapulpal screw systems on dentin structure. Dentin changes were systematically categorized into four different groups occurring alone or in combinations. Based on these observations a less traumatic screw system must be postulated. The assessment of a modified system demonstrated a considerable reduction of dentin lesions.