Motor control of jaw muscles in chewing and in isometric biting with graded narrowing of jaw gape

When a certain bite force is applied during unilateral chewing, the combination of jaw elevator muscle activities is different than when a comparable force is applied in unilateral isometric biting, e.g. on a force transducer. Masticatory peak force is generated in a nearly isometric phase of the chewing cycle, with a jaw gape of about 1 mm. In contrast, peak force in isometric biting on force measuring equipment usually induces jaw gapes of 6 mm or even more. Therefore, we tested the hypothesis that the jaw gape influences relative activation of elevator muscles in unilateral isometric biting. We further examined whether such influence could explain the different activity combinations of chewing and isometric biting. In thirty asymptomatic males, masseter and temporalis activities were recorded during intermittent isometric biting with jaw gapes of 6, 5, 3, 2 and 1 mm and during unilateral chewing. Activity combinations were described by working/balancing ratios and by temporalis/masseter ratios. With decreasing jaw gape the working/balancing ratio of the posterior temporalis decreased (P < 0.002) while that of the masseter increased (P < 0.001). Likewise, the temporalis/masseter ratio on the balancing side increased (P < 0.001). With decreasing jaw gape, activity ratios of isometric biting approached ratios of chewing. We conclude that: (i) relative jaw muscle activation in isometric biting depends on the jaw gape, (ii) relative muscle activation in chewing resembles relative activation of isometric biting with a small 'chewing-like' gape. This suggests that characteristic activity combinations in chewing are mainly a result of the approximately isometric contraction during the slow closing phase of the chewing cycle.     

Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.     

The influence of Bio-Oss Collagen on healing of an extraction socket: an experimental study in the dog

The objective of the present experiment was to evaluate the effect on hard tissue modeling and remodeling of the placement of a xenograft in fresh extraction sockets in dogs. Five mongrel dogs were used. Two mandibular premolars (4P4) were hemisected in each dog, and the distal roots were carefully removed. In one socket, a graft consisting of Bio-Oss Collagen (Geistlich) was placed, whereas the contralateral site was left without grafting. After 3 months of healing, the dogs were euthanized and biopsies sampled. From each experimental site, four ground sections (two from the mesial root and two from the healed socket) were prepared, stained, and examined under the microscope. The presence of Bio-Oss Collagen failed to inhibit the processes of modeling and remodeling that took place in the socket walls following tooth extraction. However, it apparently promoted de novo hard tissue formation, particularly in the cortical region of the extraction site. Thus, the dimension of the hard tissue was maintained and the profile of the ridge was better preserved. The placement of a biomaterial in an extraction socket may promote bone modeling and compensate, at least temporarily, for marginal ridge contraction.     

Disodium clodronate in the treatment of diffuse sclerosing osteomyelitis (DSO) of the mandible

Diffuse sclerosing osteomyelitis (DSO) of the mandible is a chronic condition, the cause of which is not known. Jaw pain, occurring irregularly, is a typical symptom. The aim of the study was to assess the effectiveness of disodium clodronate for relieving pain in patients with DSO. Disodium clodronate is a bisphosphonate used to treat diseases of bone and calcium metabolism. Ten DSO patients experiencing pain received disodium clodronate or placebo intravenously on a randomized double-blind basis. Both minimum (300 mg) and maximum (900 mg) doses were well tolerated. Disodium clodronate administration did not result in better immediate pain relief than placebo administration. However, 6 months after treatment there was a statistically significant difference in pain intensity between the groups, with the disodium clodronate group experiencing significantly less pain.     

Combined effect of zinc ions and cationic antibacterial agents on intraoral volatile sulphur compounds (VSC)

OBJECTIVE: Volatile sulphur compounds (VSC) are major components of oral malodour. As both zinc ions and cationic antibacterial agents inhibit the formation of oral VSC, this study aimed to determine whether these agents combined have synergistic anti-VSC actions. METHODS: Baseline oral VSC measurements of mouth air from 10 volunteers following cysteine rinsing (6mM, pH 7.2) were obtained using gas chromatography (GC). Subjects rinsed for 1 min with 10ml of the test solutions, 0.3% zinc acetate (Zn), 0.025% chlorhexidine (CHX), 0.025% cetyl pyridinium (CPC), and the combinations Zn+CHX and Zn+CPC. Cysteine rinses were repeated at 1h, 2h and 3h and VSC measurements recorded. Three subjects rinsed with the Zn+CHX combination and fasted for 9h, undergoing cysteine rinses and VSC measurements at 3h intervals. 10 microl of the test solutions were also added to 1ml aliquots of human whole saliva (n=8). Following incubation at 37 degrees C for 24h VSC levels in the saliva headspace were measured by GC. Inhibition of VSC formation and the fractional inhibitory index indicating synergy were calculated. RESULTS: Zn+CHX mouthrinse had a synergistic anti-VSC effect, and was effective for at least 9h. Zn+CPC mouthrinse was less effective. Both combinations showed a synergistic inhibiting effect in-vitro. CONCLUSIONS: Synergy between Zn and the antibacterial agents confirms different mechanisms of operation.     

Dental care utilization: a study of 50- to 75-year-olds in southern Sweden

This study investigates dental care utilization in an adult population in Southern Sweden in relation to dental and social conditions, attitudes to costs, and perceived need to obtain dental services. The study was based on responses to a questionnaire sent in 1998 to a random sample, 1974 persons, aged 56-75 years. The response rate was 66%. A significantly higher probability of dental care utilization less than once a year was found for men, for those with few remaining teeth, and for those with removable dentures. A higher probability of dental care utilization less than once a year was found for those who stated perceived need to obtain dental care with no possibility because of the cost and for those who stated that the cost had influenced their attendance for dental care. The results showed that there were differences for sex and dental conditions in dental care utilization and that dental care utilization was related to attitudes towards costs of dental care.     

Indikationen zur primären operativen Therapie von Gefäßanomalien im Säuglingsalter

Laser therapy. Since the introduction of laser therapy for treatment of hemangiomas and vascular malformations, primary surgical therapy has gradually lost importance. Particularly hemangiomas, but also venous malformations and lymphangiomas, are nowadays primarily treated by different types of lasers. Especially the Nd:YAG laser with a percutaneous or transcutaneous application technique often leads to satisfying results. Surgical therapy. Surgical therapy is mostly used secondarily in late childhood or in adults after several laser applications for excision of residual scars or other corrective procedures. Despite these improvements in laser therapy, there is still an indication for primary surgical treatment in subcutaneous vascular malformations and in rapidly growing hemangiomas after unsuccessful laser therapy. Even in large vascular anomalies, safe excision with only a little blood loss is possible if the tumors are encapsulated. Case reports. In this paper we want to point out the necessity of primary surgery in three children in whom complications such as loss of sight, facial nerve palsy, and a lethal outcome due to massive hemorrhage in a cystic lymphangioma could be avoided.     

Fracture behavior of structurally compromised non-vital maxillary premolars restored using experimental fiber reinforced composite crowns

PURPOSE: To study the fracture behavior of direct resin composite crowns with or without experimental fiber reinforcement. METHODS: Clinical crowns of single-rooted maxillary premolars were cut off at the cemento-enamel junction. Canals were prepared with Gates Glidden drills up to size 4. No additional post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardized (depth 2 mm, diameter 1.75 mm). Three groups of 14 samples were treated as follows: (1) custom-made glass FRC post (EverStick Post); fibers 5 mm deep in the canal, (2) similar post-system as (1) with incorporation of a new type of glass fiber fabric, (3) no fiber reinforcement (control). Posts were cemented with resin cement (Panavia F). Resin composite crowns (Filtek Z250) were made using an anatomically formed mold. Static load until fracture was applied using a universal loading device with a cylindrical bar (diameter 2 mm) with a crosshead speed of 5 mm/minute (loading angle: 30 degrees to the tooth long-axis). Failure modes were categorized as favorable and unfavorable failures. RESULTS: There was no significant difference in mean failure loads among the four groups (P > 0.05). Favorable failures occurred significantly more often in Group 2 than in the other groups (P < 0.05). The results suggest that an incorporated glass fiber fabric does not affect the load-bearing capacity of resin composite complete crowns on structurally compromised and non-vital premolars. Incorporation of a glass fiber fabric, however, has a beneficial effect on the failure mode.     

Periodontal repair in dogs: evaluation of a bioresorbable calcium phosphate cement (Ceredex) as a carrier for rhBMP-2

BACKGROUND: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to induce clinically relevant bone formation for orthopedic, craniofacial, and oral indications. It appears critical, in particular for onlay indications, that the associated carrier technology exhibits structural integrity to offset compressive forces in support of rhBMP-2-induced bone formation. The objective of this study was to evaluate a calcium phosphate (CP) cement, Ceredex, as a candidate carrier for rhBMP-2 in a defect model with limited osteogenic potential. MATERIALS: Bilateral, critical size, 6-mm, supra-alveolar, periodontal defects were created in six, adult, male, Hound Labrador mongrels. Three animals received rhBMP-2/Ceredex (rhBMP-2 at 0.20 and 0.40 mg/ml) in contralateral defect sites (implant volume/defect approximately 1 ml). One defect site in each of the three remaining animals received Ceredex without rhBMP-2 (control). The animals were euthanized at 12 weeks postsurgery for histologic and histometric analysis. RESULTS: Mean induced bone height exceeded 80% of the defect height for supra-alveolar periodontal defects receiving rhBMP-2/Ceredex without major differences between rhBMP-2 concentrations compared with approximately 40% for the control. The newly formed bone, a mixture of lamellar and woven bone in fibrovascular tissue, circumscribed relatively large portions of the residual Ceredex biomaterial. Inflammatory lesions were associated with limited bone formation in some sites. From a periodontal perspective, sites receiving rhBMP-2/Ceredex exhibited increased cementum formation compared with control, but without a functionally oriented periodontal ligament, and increased ankylosis and root resorption. Control sites exhibited early wound failure and exposure, loss of the Ceredex biomaterial, and limited bone formation. CONCLUSIONS: The Ceredex CP cement appears a potentially promising carrier technology for rhBMP-2 onlay indications. However, a slow resorption rate may prevent its wider use. This study does not support use of the rhBMP-2/Ceredex combination for periodontal indications.