Gap measurement and bond strength of five selected adhesive systems bonded to tooth structure.

The ability of a restorative material to bond and seal the interface with tooth structure is perhaps the most significant factor in determining resistance to marginal caries. Thus, the quality and durability of marginal seal and bond strength are major considerations in the selection of restorative materials. The purpose of this study was to compare the bond strength and marginal discrepancies of five adhesive systems: All-Bond 2, Clearfil Liner Bond, KB 200, ProBond and AELITE Bond. Twenty-five buccal and 25 lingual cavities were prepared in 25 caries-free extracted molar teeth, giving 10 cavities for each of the 5 adhesive systems. All teeth were restored with the resin composite Pertac Hybrid, or PRISMA Total Performance Hybrid with their appropriate adhesive systems. After restoration, the teeth were thermocycled, were stained with a 1.5% aqueous solution of a procion dye (reactive orange 14) and sectioned coronally with a saw microtome. Three sections of 200 microns thickness were prepared from each restoration which were then examined microscopically to measure marginal gap widths using a confocal tandem microscope. Shear bond strength measurements were carried out on the dentine bond using a universal testing machine. The All-Bond 2 adhesive system was found to have higher shear bond strength and to have the least gap width at the cementodentinal margin.

A laboratory study of dimensional changes for three elastomeric impression materials using custom and stock trays.

Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. Three elastomeric impression materials were used in custom and stock trays to determine the accuracy of impressions taken from an experimental stainless steel model representing premolar and molar bridge abutment preparations. Horizontal and vertical individual abutment and interabutment dimensions were measured on die stone replicas, and the measurements compared with those obtained from stainless steel master models. The results of this study demonstrate polysulphide is the least accurate impression material for both vertical and horizontal individual abutment dimensions. However, for interabutment horizontal dimensions, no statistical differences were noted between impression material types when using a custom tray. Stock trays produced unreliable results for all the materials tested.

A preliminary study of the effects of laser radiation on collagen metabolism in cell culture.

A low power Ga-As pulse laser was used to stimulate cultured human embryonic fibroblast cells. Energy fluencies varied from 0-1 J/cm2 over a period of 1-4 days. Fibroblast procollagen production was monitored by the synthesis of [3H] hydroxyproline, and DNA replication was assessed by [3H] thymidine incorporation. Following laser treatment, controlled pepsin digestion measured the increase in cell biostimulation. Maximum increase in collagen production and cell biostimulation occurred after 4 episodes of laser treatment at 24-hour intervals. Laser doses between 0.099 and 0.522 J/cm2 had the most significant stimulatory effects on fibroblast function. Clinical efficacy of the low power Ga-As pulse laser may be related to enhanced connective tissue repair.

Collagen type in dysfunctional temporomandibular joint disks.

Controlled studies were undertaken to ascertain the nature of the fibrous tissue component of surgically removed dysfunctional human temporomandibular joint disks. Each disk was divided into several parts and dissociative methods were used to extract collagenous residues. The resultant residues were digested with cyanogen bromide and the obtained soluble peptides were characterized by their electrophoretic mobility on polyacrylamide slab gels. The separated peptides were then scanned on a laser densitometer. Type III collagen was identified in samples taken from both the women's and the men's posterior disk attachment tissues. The amount of type III collagen in the women's attachments was approximately twice that found in the men's and both of these quantities were greater than those previously found in nondysfunctional tissues. The finding that there was more type III collagen in the posterior attachments of the women's chronically damaged disks may indicate that these tissues in women are less able to withstand functional loading.

Effects of splint therapy in TMJ dysfunction: a study using magnetic resonance imaging.

This pilot study was undertaken to correlate clinical and MRI diagnoses in seven symptomatic TMJ dysfunction patients and to account, if possible, for the clinical improvement in the signs and symptoms after the use of a maxillary stabilizing splint. The symptomatic TMJs were evaluated by means of MRI prior to splint insertion. Sagittal open/closed, and coronal closed images were obtained with a 0.3 T Fonar MR Scanner. A follow-up MRI was taken after three months of splint therapy for the purposes of a comparative study. All subjects responded positively even at the early phase of splint treatment. By the end of the three month period, six subjects experienced full remission of pain in the TMJ and associated masticatory muscles with one subject experiencing only partial remission following therapy. Baseline MRI study revealed that only three subjects had anterior disc displacement while the other four subjects had normal disc/condyle relationships and morphology. In the follow-up MRI study, there were no signs of recapture of the three anteriorly displaced discs despite there being evidence of improved jaw movement and remission of pain symptoms. The use of MRI in this preliminary study indicates that some but not all TMJ pain dysfunction syndromes are caused by internal derangements of the joint. A larger MRI study using the same clinical parameters is indicated for future research.

Dental abnormalities associated with a chromosome 2 deletion.

This case report describes the dental and physical anomalies observed in a young female patient who had a chromosome abnormality involving deletion of the q 33-q 35 region of chromosome 2. The dental dysplasia observed in this patient is proposed to be of genetic origin but the complication of anoxia at birth makes it difficult to assign the intellectual and physical impairments solely to the genetic deletion.

Comparison between two procion dyes and alizarin red to assess marginal leakage in resin restorations. A laboratory study.

To assess the width of the gaps that may occur in resin restorations bonded to dentine, buccal and lingual cavities were prepared in 18 caries- and restoration-free extracted molar teeth. All teeth were restored with composite resin. Nine of the teeth were then thermocycled for five hours. All teeth were stained with 0.5 per cent, 1.0 per cent or 1.5 per cent solutions of chloro-s-triazinyl dyes (Reactive Red and Reactive Orange 14) or Alizarin Red in order to assess the effectiveness of each stain in detecting marginal leakage. Quantitative assessment indicated that Reactive Orange 14 was superior to the other two stains as it more clearly defined the marginal gaps of the restorations. This superiority was evident for both thermocycled and nonthermocycled teeth.

Hereditary opalescent dentine: variation in expression.

A family is described in which two females are more severely affected by hereditary opalescent dentine than the males. The genealogy of this family does not provide an accepted pattern of inheritance for this dentine anomaly. This may indicate that there is considerable variation in inheritance patterns for hereditary opalescent dentine and that this trait does not always exhibit 100 percent penetrance.

Preliminary studies on the use of MRI in the diagnosis of TMJ disc displacement.

The temporomandibular joints of seven patients exhibiting clinical signs and symptoms of TMJ dysfunction were scanned using a 0.3T magnetic resonance system. Images were obtained with the mandible in open and closed positions. Patients were also scanned wearing a maxillary occlusal splint. Images obtained showed varying degrees of disc displacement and pathological changes in the joint depending on the severity of the clinical symptoms presented. In all patients, splints were shown to distract the joint slightly and place the condyle, disc and fossa in a more favourable relationship.

Endodontic follow up of proximal restorations in primary molars.

Proximal restorations in primary molars were assessed according to surface, teeth affected, and the need for subsequent follow up. All primary molars demonstrated a similar incidence of proximal surface restorative intervention, but the distal surface of the first primary molar and the mesial surface of the second primary molar showed the highest incidence of proximal restorations. The patient's age at initial restorative intervention did not appear to influence the need for subsequent endodontic treatment in restored teeth, indicating that early diagnosis and treatment of the carious lesion was critical for long-term pulpal health.

Presence of type III collagen in disc attachments of human temporomandibular joints.

Samples of discs and disc attachments were extracted by dissociative methods and the resultant collagenous residues cleaved with cyanogen bromide. Soluble peptides thus released were characterized by their electrophoretic mobility following SDS-PAGE and by Western blot staining with specific antibodies against type I and type III collagens. Type III collagen was identified in samples taken from the posterior discal attachments. This may explain why this disc is prone to detachment and internal derangement and the high incidence of patients with temporomandibular joint dysfunction.

Significance of variable parameters in magnetic resonance imaging of the temporomandibular joint.

Twelve asymptomatic volunteers were examined using three different groups of Magnetic Resonance Imaging (MRI) acquisition parameters (Group a: TE 30 ms, TR 480 ms; Group B: TE 20 ms, TR 315 ms; Group C: TE 30 ms, TR 1200 ms). Altering the parameters was aimed at improving the signal to noise (S:N) ratio. Group C parameters demonstrated the best clarity of the three groups. Closed jaw views gave better images than open views in all three groups.

Agenesis of the second premolar in males and females: distribution, number and sites affected.

One of the most common anomalies of the dentition is congenitally absent second premolars and this form of hypodontia may occur as an isolated trait or in association with a syndrome. Using radiographs and clinical examinations, hypodontia of second premolars was assessed in 176 subjects (80 male and 96 female). Distribution of the hypodontia was assessed according to site and number missing in males and females. No significant differences were observed in males and females with respect to the number of premolars absent, sites affected or symmetry of the agenesis. Agenesis of a single second premolar was the most common form of this hypodontia with absence of three second premolars occurring least frequently.

Mechanisms of disc displacement in the temporomandibular joint.

The sign of 'clicking' in the temporomandibular joint is not a normal phenomenon. It is, in fact, often the first indication of potential myofascial pain or temporomandibular joint pain dysfunction syndrome and as such should be detected early and diagnosed correctly. Clicking is a cardinal sign of altered function within the joint, the aetiology for which can only be diagnosed from a sound knowledge of anatomy and physiology. With this background it is possible to ascertain whether the cause is essentially biochemical, neuromuscular, or occlusal in nature or multifactorial components of all three categories. An attempt has been made to provide background knowledge in order that a correct diagnosis can be made.

A laboratory study of the effect of thermocycling in saline and artificial saliva on two dentine bonding agents.

Thermocycling of composite resins in saline and artificial saliva was carried out in order to determine the effect of these solutions on the bonding of Lumifor/Gluma and Valux/Scotchbond to dentine and enamel. Minimal Class V cavities were prepared in extracted human teeth and restored with light-cured composite resins, following each manufacturer's instructions. The restored teeth were subjected to 500 cycles at temperatures ranging between 5 degrees C and 45 degrees C. One group was thermocycled in saline, the other in artificial saliva. The resultant marginal gaps were stained and evaluated microscopically. No difference was found between the respective composite resins. However, significantly more gaps were present in those restorations thermocycled in saline.

Abnormal amino acid analyses obtained from osteogenesis imperfecta dentin.

Amino acid analyses were carried out on dentin proteins obtained from 33 normal teeth and 59 teeth from osteogenesis imperfecta patients. The analyses revealed that in the control teeth approximately 95% of the insoluble dentin fraction was collagen. The majority of the analyses for teeth obtained from the O.I. patients were biochemically abnormal (55 out of 59). Specifically, there was a significant increase in the acidic amino acids, with a corresponding decrease in the basic amino acids. A small group of patients showed double peaks in the histidine, hydroxylysine, and lysine areas of the chromatograms. These results emphasize that despite the fact that the teeth of O.I. patients may appear to be clinically normal, all but four of the teeth examined had abnormal dentin collagen.