Subgingival irrigation in the maintenance phase of periodontal therapy

The purpose of this study was to evaluate the effect of subgingival scaling versus subgingival pocket irrigation with 0.1% chlorhexidine or saline controls on the repopulation of subgingival periodontal sites with disease-associated micro-organisms following a single procedure of scaling and root planing. Additionally, pertinent clinical parameters (attachment level, plaque index, bleeding on probing) were also recorded. 375 sites in 30 individuals with previously untreated periodontal disease were thoroughly scaled and subsequently either rescaled, irrigated, or not treated at all for the following 6 months at 1-month intervals. The results show that the initial scaling and root planing procedure led to significant clinical and microbiological improvements in all experimental groups. These improvements were maintained in all but the untreated sites. Based on the observed clinical and microbiological changes, subgingival irrigation of periodontal pockets at 1-month intervals was equally effective as scaling and root planing performed at the same pace. 0.1% chlorhexidine however, being used as test irrigant, was not more effective than saline controls.     

Validated numerical modeling of the effects of combined orthodontic and orthognathic surgical treatment on TMJ loads and muscle forces.

Investigations of the changes in the mechanics of the craniomandibular system as a result of treatment have been limited by the lack of validated models of this system. The aims of this project were to (1) validate numerical model predictions of temporomandibular joint (TMJ) eminence morphology and muscle forces produced during molar biting and (2) use the validated models to calculate the changes in TMJ and muscle forces as a consequence of treatment involving orthognathic surgery. Ten volunteers participated; their combined orthodontic and orthognathic surgical treatments were completed. Three-dimensional anatomical data from each subject were used in computer models to predict the sagittal TMJ eminence morphology and joint and muscle forces for each subject, consistent with the neuromuscular objectives of minimizing joint loads and muscle effort. The actual shape of the eminence in each subject was measured with jaw tracking. Surface electromyographic recordings were a measure of the muscle forces involved in static molar biting. Model predictions were compared with measured data from the subjects for eminence shape (R(2) = 0.96) and for muscle activity ratios (R(2) = 0.98). The strength of these relationships validated the models for use in calculating changes in joint loads and muscle forces after treatment. The results suggested that the mechanics of the masticatory system are affected by the combined treatments. The TMJ loads increased in 8 subjects. The average increases in condylar and muscle forces were 4% relative to the applied bite force, but in 1 case the increases were up to 20%. Therefore, although average increases in the forces were small, some persons may experience biologically significant increases in joint and muscle forces as a result of treatment.     

Assessment of arch constriction in patients with bilateral cleft lip and palate and isolated cleft palate: a pilot study

The objective of this study was to test the use of the modified Huddart/Bodenham scoring system on patients with a bilateral cleft lip and palate (BCLP) or an isolated cleft palate (CP). Study models of 5- and 10-year-old patients with BCLP (n = 19) and isolated CP (n = 55) from the Cleft Services in Scotland database were scored using the system by four examiners on two separate occasions to test inter- and intraexaminer reliability. The weighted kappa statistic was used to evaluate reliability. The interexaminer reliability ranged from 0.48 to 0.74 (moderate to good agreement) for the BCLP group and 0.77 to 0.86 (good to very good agreement) for the isolated CP group. The number of study models available for the BCLP group was small due to the low incidence of this cleft group, but the scoring system was shown to be reliable when used in cleft types other than unilateral cleft lip and palate. The modified Huddart/Bodenham scoring system provides a useful tool suitable for assessing arch constriction in all types of orofacial clefting, which is objective, sensitive, and versatile.     

Electron microscope quantitation of inflammatory infiltrates in childhood gingivitis

Quantitation of inflammatory cell infiltrates in gingival connective tissues was carried out on 12 gingival biopsies from the deciduous dentition of 11 children aged 4–8 years. The tissue was prepared for electron microscopy and from ultrathin sections mounted on 200 mesh grids, cells in one third of the grid squares enclosing infiltrated connective tissue were counted.
The infiltrate displayed large numbers of small and medium lymphocytes and was moderately vascular. A distinct population of peripherally distributed plasma cells was present and pathologically altered fibroblasts together with marked collagen loss were notable features. Small numbers of macrophages, mast cells and polymorphonuclear neutrophils were recorded but T-blasts (immunoblasts) were very rarely encountered.
The childhood lesions have much in common with the early lesion of adult gingivitis which is considered to be a cell-mediated immune phenomenon. However, the lack of T-blasts and rather larger proportion of plasma cells suggest that the lesion of childhood gingivitis represents a position between the early and established phases of gingival disease described in older individuals. A more exact interpretation of these, the earliest stages of human gingival disease should be achieved when the lymphocytes contributing to the childhood infiltrates can be assigned to the T- and B- cell lines.     

Subcritical crack growth behavior and life data analysis of two types of dental Y-TZP ceramics

Objectives

The aim of this study was to evaluate the mechanical properties and the subcritical crack growth behavior of a presintered dental Y-TZP (Kavo Everest ZS) and a hot isostatic pressed Y-TZP (Kavo Everest ZH) and to perform life data analysis.

Methods

For each material 150 bending bars were produced. The initial fracture strength was determined in a four-point bending test. The subcritical crack growth parameters n and A were determined in a dynamic fatigue method at four decreasing loading rates from 110 MPa/s to 0.11 MPa/s in distilled water at 38 °C. For each loading rate Weibull statistics were performed and the Weibull moduli m and characteristic strengths σ₀ were calculated. Using these data, strength-fracture probability-life time (SPT) predictions were derived for 1 day, 1 year, 5 years and 10 years, based on a static crack growth mechanism.

Results

The “hipped” Y-TZP ceramic exhibited a higher initial strength (σ_c = 1618.18), characteristic strength (σ₀ = 837.15) and fracture toughness (K_IC = 4.52 MPa/m^1/2) than the pre-sintered ceramic (σ_c = 1431, σ₀ = 745.46 and K_IC = 3.17 MPa/m^1/2, respectively). Fatigue parameters, n and A, were 28.5 and 7.97 × 10⁻²⁴ for Everest ZH and 30.15 and 5.47 × 10⁻²⁰ for Everest ZS. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was 259.34 MPa for Everest ZH and 263.2 MPa for Everest ZS.

Conclusions

Although the “hipped” Y-TZP showed favorable initial mechanical properties, no significant difference could be found in the susceptibility of both ceramics to subcritical crack growth and their long-term strength.     

Identification of cultivable microorganisms from primary endodontic infections with exposed and unexposed pulp space

This study was aimed at comparing the cultivable microorganisms in canals with periapical radiolucencies with exposed and unexposed pulp space. Microbiological samples were taken and analyzed from 45 canals with exposed pulp space, and 43 canals with unexposed pulp space. The canal contents were analyzed by aerobic/anaerobic culture, and conventional identification techniques. There were 211 isolates of bacteria belonging to 28 genera and 55 species recovered from exposed canals. In the unexposed group, 185 isolates of bacteria were recovered, of which 54 species of 28 genera were identified. Among the four most common genera, Prevotella was significantly more common in the exposed group (51/211 in the exposed group versus 30/185 in the unexposed group) (p = 0.049), while there were no differences in prevalence of Actinomyces, Peptostreptococcus, and Campylobacter between two groups of canals. In addition, Fusobacterium nucleatum and Propionibacterium acne were significantly more common in the unexposed canals (p = 0.047 and p = 0.0051, respectively). Similarity in bacterial species in these two groups suggests that pulp space exposure may not be a significant factor in determining the type of bacteria present in infected canals.     

Effect of a peripheral NMDA receptor antagonist on glutamate-evoked masseter muscle pain and mechanical sensitization in women

AIMS: To test the hypothesis that local injection of the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine would significantly attenuate glutamate-evoked masseter mechanical sensitization and muscle pain in healthy young women either taking oral contraceptives (W+OC) or not taking oral contraceptives (W-OC). METHODS: Experimental pain was evoked in 47 healthy female subjects (W+OC, n=25; W-OC, n=22) by 2 injections of glutamate (0.2 mL, 1 mol/L) into the masseter muscle. A first injection of glutamate alone was followed by a second injection, 35 minutes later, of glutamate combined with ketamine (0, 1, or 10 mmol/L). Evoked pain intensity was scored on a 10-cm electronic visual analog scale (VAS). Distribution of perceived pain was drawn on a lateral view of the face (pain drawing). Masseter muscle pressure pain thresholds (PPT) and pressure-pain tolerances (PPTOL) were determined bilaterally before and at regular time intervals after injections. Analyses of variance (ANOVA) were used to test the data. RESULTS: There were no main effects of ketamine on any of the VAS pain parameters or on the pain drawing (ANOVAs: P > .055). Furthermore, there were no differences in PPT, PPTOL, VAS peak pain, duration, overall VAS pain, or pain drawing when W-OC were compared with W+OC (ANOVAs: P > .087). Repeated injection of glutamate alone significantly decreased PPT and PPTOL (ANOVAs: P < .001); however, this effect was not significantly attenuated by ketamine. CONCLUSIONS: Peripherally administered ketamine had no effect on glutamate-evoked masseter muscle pain and sensitization in healthy young women, which contrasts with recent observations in healthy young men. Further studies will be needed to reveal the mechanisms that underlie this apparent sex-related difference in ketamine-mediated analgesia.     

Experimental evaluation of microsurgical repair of the lingual nerve

Epineural microsurgical repair of the lingual nerve has been shown to be effective in leading to return of sensation in an animal model. Cadaver dissections have provided information regarding surgical access to the operative site, some possible anatomic variations that may be encountered, and a method for nerve repositioning to allow a gain in length.