R.E. Corpron

In vivo Remineralization of Artificial Enamel Lesions by a Fluoride Dentifrice or Mouthrinse

Acid-softened bovine enamel slabs were mounted in acrylic mandibular removable appliances and worn by 8 male subjects. Control slabs were worn for 4 days without exposure to topical fluoride agents. T

The effects of combined nerve resection and cavity preparation and restoration on response dentine formation in rabbit incisors.

Abstract This study was carried out to determine the effects of nerve resection and cavity preparation with restoration (CPR) on the formation of response dentine in continually developing rabbit incisor teeth. Resections of the inferior alveolar nerve (IAN) and/or the superior cervical ganglion (SCG) were performed on the right side of 42 adult New Zealand rabbits. Fifteen days were allowed for neural degeneration, after which uniform CPR were placed in both resected and adjacent normal incisors. Half of the operated animals were killed 14 days after CPR placement and the second half, 35 days after. Both radiographic and histological evidence revealed a dramatic increase in dentine deposition following IAN and IAN-SCG with CPR both 14 and 35 days after cavity preparation. The pulps of these neural-resected and CPR incisors were small and limited to the growing end of the tooth. Most of the newly formed dentine appeared regular and without defects; however, the dentine found at the apex was distorted with the appearance of osteodentine. At 14 and 35 days after CPR, the SCG-resected incisors showed no more response dentine formation than adjacent non-resected teeth. Radiographic and histologic appearance of CPR treated incisors indicated they were comparable in size and morphology to the controls.

In situ Remineralization of Subsurface Enamel Lesion after the Use of a Fluoride Chewing Gum

In situ remineralization of early enamel lesions by a fluoride chewing gum was studied. Human enamel specimens with subsurface lesions were mounted in removable lower appliances for 6 adults. Subjects used a F-free dentifrice 3x/day and chewed five sticks/day for the F gum group (0.1 mg F/stick) or five sticks of sugarless gum. No gum was chewed for controls. Surface microhardness was performed on: (1) sound enamel; (2) lesions; (3) after intraoral exposure, and (4) after acid-resistance testing (ART). Separate specimens were etched and measured for F uptake and image analyses on microradiographs were performed for all regimens. delta Z values were calculated and converted to percent of mineralization. Values for F gum were significantly higher (p > 0.05) than non-F gum and controls for ART, percent remineralization, and F uptake up to 70 microns depth.

Ultrastructure of Intradentinal Nerves After Resection of the Inferior Alveolar Nerve in Mice

Intradentinal nerves in humans have been described by light microscopic techniques by Fearnhead (J Anat 91:267-277, 1957), Rapp, Avery, and Rector (I Canad Dent .Assn 23: 447-453, 1957), Arwill (Trans R Sch Dceit 3:1-88, 1958), and Bernick (J Dent RJs 43:406-411, 1969). Ultrastructure of intradentinal nerves has been reported by Frank (Den1line and Pulp, N. B. B. SYMONS (ed), 1968. pp 115-145). Although the presence of nerves in predentin and in calcified dentin has been established, the origin of these nerves has remained in doubt. Fearnhead (Proc Roy Soc Med 54:877884, 1961) found no intradentinal nerves in a monkey after resection of the infeiior alveolar nerve. However, there is no ultrastructural evidence to date to clarify whether the nerves present in predentin or circLimpulpal dentin ate from the inferior alveolar or sympathetic nerves. The present observations are from first molars of mature white mice (50 days) in which the inferior alveolar nerve was resected by the inframandibuilar approach on the right side; the teeth of the left side served as controls. Verification of resection was established by gross dissection at the time of killing. At 21 days after resection, the teeth were fixed in 1.33% osmic acid in s-collidine buffer at 4 C for two hours, dehydrated through graded alcohols and propylene oxide, embedded in Epon 812, sectioned at 500 to 800 A, and viewed with an electron microscope.: Nerve fibers from both the control and resected teeth were selected for comparison from similar locations, namely at the odontoblastic-predentinal border at a cuspal tip. Small unmyelinated nerve fibers from the normal side located just inside the predentin from the odontoblast exhibited a central axon that contained a mitochondrion, several large vesicles, and cross-sectioned neurofilaments. The axon was surrounded completely by a Schwann cell (Fig 1). The nerve fiber from the resected side also was a small unmyelinated nerve located at the odontoblastic-predentinal border. The nerve exhibited an axon that appeared badly shrunken and degenerated and that contained a large dark body and apparent remnants of a mitochondrion, but no vesicles (Fig 2). The Schwann cell surrounding the degen-

In situ Remineralization of Enamel Lesions using Continuous versus Intermittent Fluoride Application

Remineralization of early enamel lesions was studied in situ using a F chewing gum or a F-releasing device (FRD). Enamel specimens with subsurface lesions were mounted in removable lower appliances in 6 adults. A F-free dentifrice was used for all regimens. Test groups chewed five sticks/day (0.1 mg F/stick), or one FRD (0.5 mg F/day) was mounted in the midline of the appliance. The microhardness was measured after the 21-day intraoral exposure, and in vitro acid resistance testing was performed. Separate specimens were used to measure F content or changes in mineral density. Comparable values for both F gum and FRDs were higher (p > 0.05) than controls for acid resistance testing and percent remineralization. The F content for FRDs exceeded that of both F gum and controls.

Ultrastructure of Capillaries in the Odontoblastic Layer

Terminal extensions of subodontoblastic capillaries have been observed histologically among odontoblasts in coronal pulp in a variety of species, including man. James (J Anat 89:54749, 1955), Adams (I Dent Res 38:968-78, 1959), Klingsberg et al (J Dent Res 38:419, 1959), Adams (Arch Oral Biol 7:773-774, 1962), and Jesson (Atda Odontol Scand 25: 491-523, 1967) observed capillaries at varying depths among odontoblasts, but not in contact with the predentinal surface. This study was carried out to clarify the ultr:astructural relationships of terminal capillaries in the odontoblastic layer of coronal pulp. Present observations are from 70 first molars in functional occlusion in 35 white mice (30 to 60 days old). The teeth were extracted and fixed 1.33% osmic acid in s-collidine buffer at 4 C for two hours, dehydrated through graded ethanol and propylene oxide, embedded in Epon 812, sectioned at 500 to 800 A, stained with uranyl acetate, and viewed with an electron microscope. The capillaries were located at varying depths within the odontoblastic layer and frequently were close to the predentinal surface in the pulpal horns (Fig I). In older teeth (50 to 60 days), the capillaries seemed closer to the predentin than in the younger molars (30 to 40 days). The ultrastructure of the terminal capillaries revealed an endothelial-lined channel with a lumen slightly larger than one red blood cell (Fig 1). The wall of the endothelial cell was thin with an irregular-shaped nucleus. Intracytoplasmic structures included several elements of rough endoplasmic ricticulum, occasional small, round mitochondria, and frequent pinocytotic microvesicles. Along the more flattened side of the capillary opposite the nucleus occasional pores or fenestrations appeared in the endothelial cell wall (Fig 2). A continuous basement lamina enclosed the periphery of the capillary and separated the endothelial cell wall from the thin extensions of the pericytes or adjacent odontoblasts. The terminal capillaries were not encircled completely by the processes of the pericytes and were classified as A-l-alpha capillaries (BENNETT ET AL, Am J Physiol 196: 381-90, 1959). Fenestrations of the terminal capillaries among odontoblasts appeared in the region of the endothelial cell wall not enclosed by pericytes (Fig 2); this left only the basal lamina separating the capillary pores from adjacent odontoblasts. This arrangement allows

In situ Remineralization of Root Surface Lesions Using a Fluoride Chewing Gum or Fluoride-Releasing Device

The in situ remineralization of early root surface lesions was studied using a fluoride-releasing device (FRD) or a fluoride chewing gum. Root specimens with subsurface lesions were mounted in removable lower appliances in 6 adult subjects. Test groups chewed five sticks/day (0.1 mg F/stick) or one FRD (0.5 mg F/day release rate) was mounted in the midline of the appliance. A fluoride-free dentifrice was used three times/day for each 21-day control and the two test regimens. Separate root lesions were used to measure fluoride uptake or changes in mineral content by quantitative microradiography. Comparable values for percent remineralization for both FRDs and F gum were higher than controls, and the F uptake for FRDs exceeded both the F gum and controls (p = 0.05).

Dose Related Remineralization Using Intraoral Fluoride-Releasing Devices in situ

Dose-related remineralization of enamel lesions was studied in situ. Enamel specimens with subsurface lesions were mounted on lower molars bilaterally and exposed to five regimens: (A) control with a F-free dentifrice three times daily; (B) NaF dentifrice brushed three times daily; (C) fluoride-releasing device (FRD; 0.07 mg F/day release rate) plus F-free dentifrice; (D) FRD (0.232 mg F/day) plus F-free dentifrice, F/day and (E) FRD (0.232 mg/F/day) plus NaF dentifrice. Resting and stimulated saliva samples were obtained for salivary flow and F content determinations. Twenty-eight subjects participated in this double-blind, random-assignment crossover study. After 50 days the enamel specimens were recovered, sectioned, microradiographed, and scanned with image analysis. Regimens D and E demonstrated approximately 30% additional remineralization as compared with to controls, and regimens B and C showed 13.7 and 10.5% increased remineralization as compared with to controls. The increased remineralization of the regimens generally paralleled the increase in salivary F and clearly demonstrated a dose-related response which was some threefold in relation to release rate, salivary F, and percent remineralization.

Comparison of the Effects of Two Topical Fluoride Regimens on Demineralized Enamel in vivo

The purpose of this investigation was to study the intra-oral remineralization of acid-softened enamel by a NaF dentifrice compared with that from a combination of topical F agents. Bovine enamel slabs were demineralized with 0.1 mol/L lactic acid at pH 4.0 for 14 hr and then mounted in a removable mandibular appliance. Control slabs were worn for 96 hr by seven adult males who brushed daily with a F-free dentifrice. Test slabs were brushed with a NaF dentifrice 4 x / day or with the same dentifrice 4 x /day and a 0.02% APF mouthrinse and a 0.4% SnF2 gel which were applied oncelday for three days. The natural dentition was also brushed with the NaF dentifrice during both test periods. Microhardness testing was performed on sound enamel, and after acid-softening, intra-oral exposure (IOE), and acid resistance testing (ART) in 0.01 mol/L lactic acid at pH 4.0 for 24 hr. Control and test slabs were etched with 0.5 mol/L HClO4 for from 15 to 60 sec. The F content was measured with a F electrode and PO4 by spectrophotometry. Contact microradiography and image analyses were performed on control and test slabs so that changes in mineral content resulting from treatment could be assessed. Both test groups were significantly harder after both IOE and ART than were controls, but no differences appeared between the effects of the two test groups. The F content of control slabs was significantly less than that of both test groups, and the combination-treated slabs showed greater F than did the dentifrice-treated slabs. Microradiographs revealed a higher mineral content in the basal 2/3 of combination-treated lesions, while diffuse mineral deposition occurred, especially subjacent to the surface in the dentifrice-treated lesions. Control lesions showed little added mineral.

Effects on Artificial Enamel Lesions in vivo by Exposure to NaF Lozenges

Bovine enamel slabs were acid softened, mounted in acrylic mandibular removable appliances, and worn by 8 male subjects. Control slabs were worn for 4 days and brushed four times daily with a fluoride