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Notizen: Abstract Previous experimental studies into the use of dentin bonding agents for reattachment of enamel-dentin crown fragments have demonstrated fracture strength about 50–60% of that of intact teeth. In the clinic this has been reflected in the frequent need of repeated bonding of the treated incisors due to refracture. Recently newer bonding agents have been developed which can bond equally well with enamel and dentin. Employing the same experimental model, these bonding agents (All-Bond 2, Scotchbond MP) were used to reattach crown fragments to the remaining portion of sheep incisors. Loading of teeth bonded with these agents in an Instron testing machine at a speed of 1 mm/min demonstrated similar fracture strengths as those previously achieved with Gluma, Scotchbond 2 or Tenure. A second study was carried out whereby fragments were bonded with Scotchbond MP and loaded at various speeds. The results demonstrated that the fracture strength decreased exponentially with increased loading speed. By extrapolation, it was concluded that the strength was nil at a loading speed of approximately 2 m/min. It was concluded that the weak link in the bond between tooth fragment and remaining tooth structure is the bonding resin. Theoretically, a resin which is slightly elastic might act as a shock absorber to withstand functional stress. However, studies carried out with resins of varying moduli of elasticity gave disappointing results probably due to their low flexural strength. It is concluded on basis of previous and present results that reattachment with a bonding resin of the enamel dentin crown fragment after crown fracture is a realistic alternative to composite resin build-up although only half the strength of intact teeth is achieved.

Notizen: Abstract A relationship between type of luxation injury, stage of root development and development of pulp necrosis after injury has been demonstrated. It was therefore decided to delve more deeply into the relationship between stage of root development and the later development of pulp necrosis after injury in a material of luxated permanent teeth. In this context, the diameter of the apical foramen and the distance from the apical foramen to the pulp horn, as measured on radiographs taken at the time of injury, were used as indicators of root development. In order to justify this approach, the precision of the measuring technique and the accuracy of the radiographic technique were studied. Regarding precision of the measuring technique, it was found that there was a 1% to 4.3% error of the means of all measurements for the various parameters and exposure techniques employed. With respect to accuracy of the radiographic technique, it was found that there was a systematic error in the radio-graphic technique which resulted in a median relative distortion of between 3.5% and 8% image magnification for the various parameters and the exposure techniques employed. These findings indicated that the measuring technique employed in the present investigation was reliable for studying the parameters in question. In a material of 226 extruded, intruded and laterally luxated maxillary permanent incisors, observed for up to 10 years, it was found that the development of pulp necrosis after injury was significantly related to the diameter of the apical foramen. For extruded and laterally luxated teeth, the smaller the diameter, the greater the probability of pulp necrosis. Intruded teeth with incomplete root development (i.e. radiographic diameters ≥1.2 mm) were associated with a much higher probability of pulp survival than teeth with complete root development (i.e. radiographic diameters ≤0.7 mm). The distance from the apical foramen to the pulp horn did not appear to be of importance in predicting pulp survival when diameter of the apical foramen was taken into account. Pulp survival after luxation injuries with displacement thus appears to be dependent upon the size of apical contact between the pulp and the periodontium.

Notizen: Abstract  – The effect of temperature of various storage media and at varying storage periods upon periodontal ligament (PDL) and pulpal healing after tooth replantation was examined in green vervet monkeys (Cercopithecus aethiops). Mandibular lateral incisors with mature root formation were extracted and kept in dry storage at 22, 4 and −18 °C; in saline at 37, 22, 4 and −18 °C; or in saliva (i.e. in the buccal vestibule) at 37 °C for either 60 or 120 min prior to replantation. The animals were sacrificed 8 weeks after replantation and the replanted teeth examined histometrically. The following histological parameters were registered for each tooth: normal PDL, surface resorption, inflammatory resorption, replacement resorption (ankylosis), downgrowth of pocket epithelium, periapical inflammatory changes, and the extent of vital pulp. A total of 125 replanted teeth were examined. Storage in saliva at 37 °C showed a similar amount of normal PDL compared to saline storage for both 60 and 120 min. Saline storage for 60 or 120 min showed no difference in the extent of normal PDL when storage was compared at 37, 22 and 4 °C. However, storage at −18 °C resulted in significantly less normal PDL than storage at other temperatures. Dry storage for 60 min showed significantly less root resorption at 4 °C compared to 22 °C. Furthermore, dry storage at −18 °C showed significantly less normal PDL than storage at 4 °C. When the dry storage period was extended to 120 min, no difference was found between 22, 4 and −18 °C. It is concluded that the temperature (above 0 °C) of the storage medium is of importance only for dry storage and in such a situation only for shorter extra-alveolar periods, i.e. for 60-min storage and not for 120 min, where extensive destruction of the PDL always takes place. It is suggested that the temperature effect of 4 °C could be related to less evaporation from the PDL and thereby less damage to the PDL cells or a strict temperature effect upon cell metabolism. Pulp healing in all the cases was limited to the entrance of the pulp canal, and no significant pattern was found between storage media, time and temperature.

Notizen: Abstract A material of 322 patients with 400 avulsed and replanted permanent teeth were followed prospectively in the period from 1965 to 1988 (mean observation period=5.1 yrs). The age of the patients at the time of replantation ranged from 5 to 52 yrs (mean =13.7 yrs and median =11.0 yrs). Standardized patient records were used through the entire period in order to obtain valid data concerning the extent of injury and treatment provided. At the follow–up period, pulpal and periodontal healing were monitored by clinical examination, mobility testing and standardized radio–graphic controls. Thirty–two of the replanted teeth (8%) showed pulpal healing. When related to teeth with incomplete root formation, where pulpal revascularization was anticipated (n = 94) the frequency of pulpal healing was 34%. Periodontal ligament healing (i.e. with no evidence of external root resorption) was found in 96 teeth (24%). Gingival healing was found in 371 teeth (93%). During the observation period, 119 teeth (30%) were extracted. Tooth loss was slightly more frequent in teeth with incomplete root formation at the time of replantation than in teeth with completed root formation.

Notizen: Abstract –  This is the second part of a retrospective study of 400 root-fractured permanent incisors. In this article, the effect of various treatment procedures is analyzed. Treatment delay, i.e. treatment later than 24 h after injury, did not change the root fracture healing pattern, healing with hard tissue between fragments (HH1), interposition of bone and/or periodontal ligament (PDL) or pulp necrosis (NEC). When initial displacement did not exceed 1 mm, optimal repositioning appeared to significantly enhance both the likelihood of pulpal healing and hard tissue repair (HH1). Significant differences in healing were found among the different splinting techniques. The lowest frequency of healing was found with cap splints and the highest with fiberglass or Kevlar® splints. The latter splinting procedure showed almost the same healing result as non-splinting. Comparison between non-splinting and splinting for non-displaced teeth was found to reveal no benefit from splinting. With respect to root fractures with displacement, too few cases were available for analysis. No beneficial effect of splinting periods greater than 4 weeks could be demonstrated. The administration of antibiotics had the paradoxical effect of promoting both HH1 and NEC. No explanation could be found. It was concluded that, optimal repositioning seems to favor healing. Furthermore, the chosen splinting method appears to be related to healing of root fractures, with a preference to pulp healing and healing fusion of fragments to a certain flexibility of the splint and possibly also non-traumatogenic splint application. Splinting for more than 4 weeks was not found to influence the healing pattern. A certain treatment delay (a few days) appears not to result in inferior healing. The role of antibiotics upon fracture healing is questionable.

Notizen: Abstract A study into the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root resorption cavities was performed in a cadaver material. Film contrast and horizontal angulation were varied in order to identify factors in radiographic exposure which resulted in the greatest diagnostic reliability. In an autopsy material of 5 jaw blocks containing both mandibular premolars, “small, medium and large” cavities simulating root resorptions of 0.6, 1.2 and 1.8 mm in diameter and 0.3, 0.6 and 0.9 mm in depth, respectively, were drilled at the cervical, middle and apical thirds of the proximal and oral root surfaces of the premolars. Cavity locations were distributed to ensure an equal number of locations with and without cavities and an equal number of cavities of each size. Results of the investigation indicated that the small cavities were never visualized, nor were 6 out of 13 medium cavities nor 1 out of 13 large cavities; that cavities located proximally were more readily seen than those located orally and that there was no clif Terence in cavity visualization between cavities on the apical, middle or cervical thirds of the roots; high density (contrast) films allowed the best cavity visualization. Finally, radiographs from the time of injury (i.e. preresorption radiographs) as well as radiographs taken at various horizontal angulations were found to be of importance in order to increase the possibility of cavity visualization.

Notizen: Abstract The effect of damage to the Hertwig's epithelial root sheath (HERS) during autotransplantation was examined in 12 green vervet monkeys. During the transplantation of permanent incisor tooth germs, either one-half or the entire root sheath was amputated or a contusion injury made to the root sheath. Transplanted incisors served as controls, where attempts were made not to injure the HERS. After an observation period of 9 months, a histologic examination of the transplanted teeth was performed. This examination showed variations in root growth among the various experimental groups. Thus, arrested root formation with ingrowth of bone from the base of the socket was the normal finding in the groups where either the entire HERS was amputated or contused. The group with partial amputation of HERS showed formation of a new but diminutive root. The control group showed teeth with normal root formation. The development of pulp necrosis usually led to complete or almost complete arrest of root formation irrespective of group. The present study indicated that the HERS can function normally subsequent to trauma elicited by surgical separation of the follicle and the post-transplantation disturbances in nutrition. Furthermore, a regenerative potential appeared to exist in this structure, even if just a fraction of it was left intact.

Notizen: Abstract The tissue solvent capacity of a 2% stabilized sodium hypochlorite solution (Milton®) and a commercial calcium hydroxide solution (Calasept®) was examined under in vitro conditions where autolyzed human pulp fragments weighing approximately 0.0065 g were immersed in these solutions at 37°C for periods of up to 10 days. It appeared that sodium hypochlorite was able to dissolve half the volume of pulp tissue within 1 h and the remaining tissue after 2–2 1/2 h. Calcium hydroxide dissolved half the pulp volume within 2 h, whereas it took 1 week for the remaining tissue to dissolve. These findings support the use of sodium hypochlorite as an irrigation solution during canal preparation and calcium hydroxide as a canal dressing for the purpose of creating a canal free of pulp remnants before root filling.

Notizen: Abstract Horizontal and vertical rigidity of teeth fixed with seven types of denial splints were evaluated by two tooth mobility measuring devices. Altogether 21 dissected sheep mandibles including soft tissues were used for the experiments in which Fermit, flexible wire-composite, Kevlar, Fiber, Protemp, rigid wire-composite and Triad Gel splints were applied to four incisors. The mean rigidity of the central incisors within the splint was measured by means of Mühlemann periodontometer (horizontal mobility) and Periotest (horizontal and vertical mobilities). Mobility values of teeth before splinting were used as covariants and the values with the splints were illustrated as adjusted mobility. Statistical significance between the rigidity of various splints was analyzed by an unpaired t-test. It was shown that the most rigid splints both in horizontal and vertical directions were Triad Gel, rigid wire-composite and Fermit splints. Kevlar and Fiber splint allowed more horizontal movement than other splints. Protemp and flexible wire-composite splints proved to produce adequate lateral support for the fixed teeth and allowed vertical flexibility which is experimentally known to improve periodontal healing of luxated teeth.

Notizen: Abstract A method is described, by which the fracture strength of bonded, previously fractured incisors can be measured. The study employed incisors from sheep, which could be obtained in suitable numbers and with limited variation in size. The incisors were fractured parallel to the incisal edge. The mean fracture area + SD of central incisors was 8.45 ± 0.89 mm2 and of lateral incisors 6.50 ± 0.64 mm2. The enamel area constituted about 30% of the total fracture area. Acid etching of the enamel and bonding of the fractures with an unfilled resin yielded a fracture strength, which was approximately 38% of the fracture strength of fractured teeth restored with acid etching of enamel, Gluma treatment of dentin and bonding with the unfilled resin. Teeth restored in this way, but using the dentin bonding agent Tenure or Scotchbond2 instead of Gluma, exhibited mean fracture strengths which were not significantly different from that obtained when Gluma was employed as the bonding agent. The mean fracture strength by using one of the three bonding agents in combination with acid etching of enamel was about 8 MPa, which is approximately 50% of the fracture strength of intact teeth.