Clinical short term study of marginal integrity of resin restorations

The marginal adaptation of 649 Durafill and Silux fillings in beveled and acid etched enamel cavities was assessed in a clinical study. The investigation included Class III with and without lingual extension, Class IV and Class V. The frequency of marginal discoloration and marginal gaps after 15 months was markedly reduced in all Classes when a low-viscous resin was used prior to application of the restorative.     

Clinical evaluation of the Prophy-Jet as an instrument for routine removal of tooth stain and plaque

The Prophy-Jet was evaluated for its effectiveness in removing plaque and stain from teeth and on its effects on the marginal gingiva. Using a randomized split-mouth design, half the mouth was treated with the Prophy-Jet and the contralateral side with a rubber cup and prophylaxis paste. The results indicated that the Prophy-Jet removes tooth plaque and stain as well as the rubber cup and prophylaxis paste method, and does so in less time. It was also found that there was some immediate soft tissue trauma following both treatment modalities, with a mean Trauma Index score of 0.23 not equal to 0.16 for the rubber cup and prophylaxis paste and 0.75 not equal to 0.37 for the Prophy-Jet. Within 6 days, the trauma index scores were not significantly different. Similar results were found for marginal gingival redness and bleeding on probing. The Prophy-Jet is an excellent alternative instrument for removal of tooth stain and dental plaque.     

Streptococcus milleri (Guthof) and Streptococcus mutans in the mouths of infants before and after tooth eruption.

Group I infants had no primary teeth, group II had 2–8 primary teeth, and group III had all primary teeth erupted. Streptococcus sanguisand Streptococcus salivarius were analysed as reference organisms. Strep. milleri was detected in samples taken from 6 of the 21 infants in group I, in 9 of the 16 in group II, and in 15 of the 16 infants in group III. The prevalence of Strep. milleri was similar to that of Strep, sanguis, suggesting that the presence of teeth favours the establishment of Strep, milleri. Small numbers of Strep.mutans were observed in all 3 groups. The low prevalence and proportions of Strep, milleri,Strep. sanyuis and Strep. mutans in predentate infants suggest that they are not indigenous to the mouth.     

Diabetes increases collagenase activity in extracts of rat gingiva and skin

The connective tissues of diabetic humans and experimental animals exhibit abnormalities in collagen metabolism including an increased production of collagenolytic enzymes by gingival explants in tissue culture. In the current study, gingival tissue and skin were obtained from control and diabetic rats, the latter on the 5th, 10th, 15th, and 22nd day after inducing the disease with streptozotocin. Extracts of the tissues were assessed for collagenase activity using either ¹⁴C-labeled collagen fibrils or Peptide-P as substrate and by detecting collagenase digestion products by SDS-polyacrylamide gel electrophoresis. Elastase was measured using the specific substrate, succinyl-(L-Alanyl)₃-p-nitroanilide. Diabetes increased the activity of collagenase in extracts of gingiva and skin; elastase, however, was increased dramatically only in the latter tissue. These findings (1) indicate that diabetes-induced enhanced gingival collagenase activity occurs in vivo as well as in vitro and (2) explain, at least in part, the greater loss of collagen in skin than in gingiva of the diabetic rat and other complications such as unusually severe periodontal breakdown.     

The effects of intraoral splints on the masticatory system of pigs

While evidence exists to support the effectiveness of splints on conditions involving the masticatory musculature, few research projects have examined the results of long-term splint wear. The purpose of this study was to examine the function of the masticatory system over a 2-month time period of splint wear. Young adult female miniature pigs were divided into three groups: a control (C) group that wore no intraoral splint, a control splint (CS) group that wore a splint increasing bite height, and a protrusive splint (PS) group that wore a splint increasing bite height and moving the mandible anteriorly. Splints were worn constantly. Fine-wire needle EMG was performed prior to splint delivery and at 1 and 2 months post-splint delivery. Bilateral superficial masseters and zygomaticomandibularis (ZM, equivalent to deep masseter) muscles were monitored during normal feeding. Absolute EMG output, percentage output, and cycle timing were unaffected by chronic splint wear. However, chewing coordination was significantly changed in the splinted groups in both sessions post-splint delivery relative to baseline readings and to the C group (P < 0.005). Trends indicate that the coordination of the PS group was more greatly altered than that of the CS group.     

Stainless steel bands in endodontics: effects on cuspal flexure and fracture resistance

AIMS: This study investigated the effect of stainless steel bands on cuspal flexure and fracture resistance of extracted maxillary premolars. METHODOLOGY: Twenty extracted maxillary premolars (10 matched pairs) with mesio-occluso-distal (MOD) cavities and endodontic access were subjected to occlusal loading tests (100 N) using a servo-hydraulic testing machine. Cuspal deflections were measured by an extensometer, with and without the band present. Ten teeth (one of each pair) then had the band removed, and all teeth were subjected to loading until fracture. RESULTS: Mean cuspal flexure of teeth with bands was one-half of flexure without bands (P < 0.001). Teeth with bands fractured at higher load than their matched pairs with the band removed (P < 0.001), with mean loads at fracture of 1282 N and 729 N, respectively. CONCLUSIONS: The study showed that stainless steel bands used in endodontics reduce the cuspal flexure of maxillary premolars and increase their fracture resistance.     

Immunolocalization of PTCH protein in odontogenic cysts and tumors

The human patched gene (PTCH) functions in both embryologic development and tumor suppression. PTCH mutations have been found in odontogenic keratocysts. However, the expression and localization of the protein product of the gene have not been determined in odontogenic tumors and cysts. We investigated 68 odontogenic lesions by immunohistochemistry, and compared their PTCH expression with that in basal cell carcinomas. All odontogenic lesions, including two keratocysts with truncating mutations, were positive for PTCH. Different types of lesions had different amounts of staining. Lack of staining was noted in the majority of basal cell carcinomas. Taken together, these data suggest that odontogenic keratocysts arise with heterozygous mutations of the PTCH gene.     

Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: a radiographic study in the canine mandible

BACKGROUND: Accumulating evidence suggests that alveolar crestal bone resorption occurs as a result of the microgap that is present between the implant-abutment interface in dental implants. The objective of this longitudinal radiographic study was to determine whether the size of the interface or the microgap between the implant and abutment influences the amount of crestal bone loss in unloaded non-submerged implants. METHODS: Sixty titanium implants having sandblasted with large grit, acid-etched (SLA) endosseous surfaces were placed in edentulous mandibular areas of 5 American fox hounds. Implant groups A, B, and C had a microgap between the implant-abutment connection of <10 microm, 50 microm, or 100 microm, respectively, as did groups D, E, and F, respectively. Abutments were either welded (1 -piece) in groups A, B, and C or non-welded (2-piece screwed) in D, E, and F. All abutment interfaces were placed 1 mm above the alveolar crest. Radiographic assessment was undertaken to evaluate peri-implant crestal bone levels at baseline and at 1, 2, and 3 months after implant placement whereupon all animals were sacrificed. RESULTS: The size of the microgap at the abutment/implant interface had no significant effect upon crestal bone loss. At 1 month, most implants developed crestal bone loss compared with baseline levels. However, during this early healing period, the non-welded group (D, E, and F) showed significantly greater crestal bone loss from baseline to one month (P <0.04) and 2 months (P < 0.02) compared with the welded group (A, B, and C). No significant differences were observed between these 2 groups at 3 months (P > 0.70). CONCLUSIONS: Crestal bone loss was an early manifestation of wound healing occurring after 1 month of implant placement. However, the size of the microgap at the implant-abutment interface had no significant effect upon crestal bone resorption. Thus, 2-piece non-welded implants showed significantly greater crestal bone loss compared with 1-piece welded implants after 1 and 2 months suggesting that the stability of the implant/abutment interface may have an important early role to play in determining crestal bone levels. At 3 months, this influence followed a similar trend but was not observed to be statistically significant. This finding implies that implant configurations incorporating interfaces will be associated with biological changes regardless of interface size and that mobility between components may have an early influence on wound healing around the implant.