Quintessence International, 01/2001

Numerous authors and textbooks have advocated the concept of bilateral simultaneous occlusal contacts as one of the necessary components of an optimum occlusal condition. All occluding surfaces should meet at the same moment of time during a mandibular closure. Articulating paper labeling that appeared widely distributed throughout the arch was thought to represent this advocated occlusal condition. However, computerized occlusal analysis shows that true bilateral occlusal contact time simultaneity is not accurately represented by widespread paper labeling. Articulating paper labeling is an inadequate indicator of perceived occlusal contact time simultaneity as it renders no occlusal contact force or time sequencing. When occlusal adjustments are guided by computerized occlusal analysis, occlusal contacts on all potentially occluding teeth can be approximated to occur within .2 second. This technique report describes a clinical procedure that employs computerized occlusal analysis to guide sequential occlusal adjustments to obtain measurable bilateral occlusal contact simultaneity. Additionally, the phenomenon of how articulator paper labeling can be a misleading indicator of occlusal contact timing and force content is presented.

Objective: Dental adhesion has become one of the most challenging topics of restorative dentistry. Acids are now applied on dentin to improve adhesion. If the acid penetrates deeper than the adhesive resin subsequently applied, an area of vulnerable collagen fibers may weaken the bonding. This in vitro study was designed to evaluate the effect of etching time on the depth of dentin demineralization, using Field Emission Scanning Electron Microscopy. The null hypothesis tested was that the depth of dentin demineralization would not vary proportionally with etching time. Method and materials: Twenty-one dentin disks were obtained from extracted human molars by diamond saw sectioning. The specimens were equally assigned to 7 different etching times (n = 3). The dentin surfaces were etched with 35% phosphoric acid, fixed, dehydrated, and dried. The specimens were observed using a Field Emission Scanning Electron Microscope. The morphological appearance of the dentin surfaces was compared both from an occlusal view and from a lateral view. The depth of demineralization of intertubular dentin was registered for all specimens. Results: For an etching time of 5 seconds, the mean depth of demineralization was 1.1 µm. For an etching time of 120 seconds, the mean depth of dentin demineralization was 8.1 µm. Conclusion: Although there was a significant correlation between etching time and depth of intertubular penetration, the depth of phosphoric acid penetration into dentin was not proportionally correlated to the respective etching time. When the acid was replenished with fresh etchant after 60 seconds, the depth of penetration increased substantially.

Objective: This study was undertaken to determine if any current materials can prevent coronal leakage in the restoration of endodontic access openings in permanently fixed crowns following nonsurgical root canal therapy. Method and materials: Sixty mandibular first molars and 36 maxillary central incisors were assigned into 1 of 8 complete-coverage crown groups. Endodontic access openings were made through the restorations and randomly placed in 1 of 5 access restorative modalities. A culture of Proteus vulgaris was placed into the coronal reservoir of each assembly of a leakage assessment apparatus for 30 days. Specimens were examined weekly, and turbidity was recorded. Results: Chi-square tests and Fisher's exact test were used for statistical evaluation. A total of 51% of specimens (41/80) demonstrated turbidity. The findings did not indicate a statistically significant association between the materials used and the presence of bacterial leakage. All-metal noble crowns demonstrated the lowest rate of turbidity (20%), and all-porcelain crowns exhibited the highest rate of turbidity (70%) among posterior teeth. Anterior teeth were more than 3.5 times as likely to exhibit bacterial leakage as posterior teeth. Conclusion: When challenged with bacteria, all materials allowed significant leakage. All-porcelain crowns demonstrated more leakage than the other types of crowns. Anterior crowns leaked the most, regardless of crown or restoration type.

Objective: This study was undertaken to determine if any materials in clinical use can prevent coronal leakage when used to restore endodontic access openings in permanently fixed crown restorations. Method and materials: Ninety-six teeth were allocated to 1 of 8 complete-coverage crown groups. Endodontic access openings were made through the crowns and restored with 1 of 5 restorative modalities. Methylene blue dye was placed in the coronal reservoir of each assembly of a leakage assessment apparatus for 30 days. Teeth were embedded in methylmethacrylate, sectioned, and computer scanned. Three calibrated, independent examiners assessed computer-projected views with a predetermined scoring system. Results: The overall difference between the material-crown margin and the crown-tooth margin indicated more leakage on the latter, but the difference was not statistically significant. Porcelain-covered crowns showed greater leakage, but no statistically significant difference was found among crown types. Glass-ionomer restorations had higher leakage values, but there was no statistically significant difference among materials. Conclusion: Coronal leakage at the material-crown margin is substantial when endodontic access openings are restored in complete-crown restorations that have undergone nonsurgical root canal therapy.

Objective: The purpose of this case report is to provide a simple forced eruption technique to recover a decayed canine that was a primary abutment for a fixed partial denture (FPD). After an analysis of casts on an articulator, a forced eruption technique was applied, using the old FPD as a bracket to apply the extrusion force on the root of the canine. After 6 weeks, the desired 5-mm extrusion was achieved, maintaining the old FPD in its original position. This simple procedure has many advantages compared with the traditional root extrusion techniques. The use of the old FPD allowed preservation of esthetics and function, better application of the eruption force, guided extrusion of the tooth, and reasonable stabilization time.

Objective: This study measured and compared the in vitro microleakage behavior of a compomer restorative material, Dyract (LD Caulk); a conventional glass ionomer, Ketac-Fil (ESPE Premier); and a resin-modified glass ionomer, Fuji II LC (GC America). Method and materials: Class V preparations measuring 2 mm 3 3 mm 3 2 mm were cut at the cementoenamel junction on the facial surfaces of 30 freshly extracted bovine incisor teeth. The 30 teeth were randomly divided into 3 groups of 10 each, restored using the material of choice following the manufacturer's instructions, and placed in distilled water at 37°C. After 10 days' storage, the teeth were thermocycled between 4°C and 58°C for 100 cycles using a 1-minute dwell time, followed by a 2-hour immersion in Ca45 isotope. The teeth were sectioned longitudinally, wet-ground until smooth using 600 grit SiC paper, and placed on a radiographic film for 12 hours to produce autoradiographs. Microleakage was evaluated on a 0 (no microleakage) to 3 (gross microleakage) scale with separate scores for the incisal and gingival margins. Results: The results were analyzed using the Mann-Whitney U Test. Results showed no significant differences between groups at the incisal margin (P = 0.10). At the gingival margin, the mean leakage score for Dyract was significantly greater than Fuji II LC and Ketac-Fil (P = 0.08 and P = 0.06, respectively). Conclusion: These results suggest that this new compomer composition may not be as effective as conventional and hybrid ionomers at sealing gingival margins in Class V restorations.

Primary failure of eruption, or primary retention, is an abnormality of tooth eruption that is characterized by cessation of eruption in the pre-eruptive stage, resulting in a deeply embedded tooth in the alveolar bone. This condition should be differentiated from secondary failure of eruption, which implicates termination of the eruptive process following tooth emergence into the oral cavity, resulting in infraclusion associated with impaired growth of the supporting alveolar bone. Primary failure of eruption of primary molars may have several effects on the developing dentition, which include malformation, impaction, or ectopic eruption of the succeeding premolars. Another possible complication is inversion between the premolar and its embedded predecessor primary molar. Primary retention of the primary second molars may result in ectopic eruption of the permanent first molars. This paper reviews the characteristics, etiology, and sequelae of primary failure of eruption of primary molars and describes a case of an unerupted mandibular right primary second molar in a healthy 5-year-old girl. The child had no previous facial trauma or infection and a noncontributory familial history. Treatment consisted of surgical extraction of the embedded molar followed by placement of an intra-alveolar space maintainer and regular follow-up examinations.

In the mid-1940s at Columbia University School of Dental and Oral Surgery, Dr Irwin Mandel began a pioneering career in research on salivary chemistry in health and disease. It brought him an international reputation, an array of awards, and honorary degrees from prestigious universities. In the first half of his 50-year tenure at Columbia, he shared his commitment to research with the operation of a half-time private practice in Manhattan. Then, after giving up his practice, he became a full-time faculty member at Columbia as division head of preventive dentistry and community health, and concluded his service as associate dean for research. Dr Mandel has become recognized by his peers at Columbia and by the academic community across the United States as a symbol of integrity, both in his research and as a person. Shaped in childhood by a culture of caring in a community of Jewish immigrants to which his father was dedicated, he became well-known for his thoughtful mentoring of rising scientists. Additionally, for much of his life, he was a committed social activist.