Scientific Article Remineralizationof caries-like lesions of enamelwith acidulatedcalcifying fluids: a polarized light microscopicstudy Catherine M. Flaitz DDS, MS M. John Hicks DDS, MS, PhD, MD Abstract 45%of 10-year-old children and 72% of 14-year-old adolescents have experiencedcaries. 1, 2 By age 17 years, The purposeof this in vitro study was to evaluate the dental caries has occurred in almost 85%of these late effects of acidulated calcifying fluids (CF) adolescents.i, 2 The caries prevalence data from the remineralization of caries-like lesions of enamel. Lesions 1 were created in sound enamelusing an acidified gel. Cen- NIDRsurvey represent only clinically detectable car- ies and do not include caries that would be diagnosed tral longitudinal sections weretaken from each tooth (N 20)following lesion formation to serve as control lesions by radiographic examination. Furthermore, it is well (CL). Each tooth was sectioned into quarters and each knownthat enamel caries may exist for a considerable quarter was assigned to one of four groups: 1) 1 mMcal- length of time prior to either radiographic or clinical detection. 4 The prevalence of such undetectable white cium CFat pH 7.0 (CF1); 2) 1 mMcalcium CF at pH (ACF1); 3) 3 mMcalcium CF at pH 7.0 (CF3); 4) spot lesions within the pediatric, adolescent or adult calcium CFat pH5.0 (ACF3).Tooth quarters were treated populations is not known. This information reinforces the need to develop innovative techniques and alter with assigned CFs(HAP [Ca/P = 1.63], pH7.0 or 5.0, 0.05 mMFl) for ten 60-sec periods. Longitudinal sections were existing regimens for prevention and remineralization of both clinically detectable enamellesions with intact preparedand imbibedin water for polarized light study. Mean lesion depths were determined and compared surfaces and clinically undetectable white spot lesions. A variety of calcifying fluids, synthetic salivas, and (ANOVAand DMR). With I mMcalcium CFs, mean le- oral fluids have been developed in the past to sion depths were 187 l~m for CL, 154 l~m for CF1and 133 ~tm for ACF1. With 3 mMcalcium CFs, mean lesion remineralize enamel caries, s-~7 Unfortunately, remin- depths were 192 t~m for CL, 172for CF3and 149 for ACF3. eralization of naturally occurring white spot lesions Acidulated (22%, 29%) and nonacidulated (10%, 18%) and caries-like lesions of enamel requires numerous CFsresulted in significant reductions(P < 0.05) in lesion exposures to the treatment fluid for considerable time depths when comparedwith control lesions. Acidulated periods. Recently, acid-etching of caries-like lesions of CFs(13%, 14%)resulted in significant lesion depth re- enamel prior to treatment with calcifying fluids has ductions (P < 0.05) when comparedwith nonacidulated been shownto enhance remineralization, using a regi- CFs. The acidulated I mMcalcium CF producedthe great- men that would appear to be clinically applicable/ est degree of remineralization. Acidulation of CFs en- With this encouraging information, it maybe possible hancedthe degree of remineralization over that attained to facilitate remineralization by acidulating calcifying fluids, thereby eliminating the need for the acid-etch by nonacidulated CFs. This improvement in remineralizingability of acidulated calcifying fluids may step prior to calcifying fluid treatment. be due to creation of a more reactive enamel surface. The purpose of this in vitro study was to evaluate the effects of acidulation of synthetic calcifying fluids (Pediatr Dent 18:205-9, 1996) containing 1 mMand 3 mMcalcium on remin- eralization of caries-like lesions of enamelusing polar- ental caries within the pediatric and adolescent ized light microscopic techniques. ~population continues to be a disease of consid- DLerable clinical importance. - Althougha recent Methods and materials NIDRcaries prevalence surveyI indicated that slightly Twenty macroscopically caries-free human molar less than 50%of children and adolescents were caries- teeth were chosen for this laboratory study. Following free, these results are somewhatmisleading. 2 In fact, a fluoride-free prophylaxis, the specimens were coated PediatricDentistry - 18:3,1996 AmericanAcademy of PediatricDentistry 205 with an acid-resistant varnish except for two windows ing polarized light microscopic techniques. Photomi- of sound enamel on both buccal and lingual surfaces. crographs of the lesions were projected onto a digi- The specimens were then exposed to a dialyzed-recon- tized tablet and five measurements were made along stituted acidified gel18 (1.0 mMcalcium, 0.6 mMphos- the advancing front of the body of the lesion to de- phate, 0.05 mMfluoride at pH 4.75 _+ 0.02) to create termine mean body of the lesion depth. In addition, cariesqike lesions in the exposed enamel windows. mean surface zone depth was obtained by taking five After 10 weeks, central longitudinal sections were pre- measurements along the inner aspect of the surface pared from each specimen to serve as control lesions zone. Data from 40 paired lesions from each of the prior to experimental treatment. After obtaining cen- experimental and control groups were available for tral longitudinal sections, the teeth were sectioned into statistical analysis. Comparisons were made among quarters and specific quarters from each tooth were the mean depths for each group using ANOVAand assigned to a treatment group: Duncan’smultiple range test for a paired design with 1.1 mMcalcium calcifying fluid (CF) at pH 7.0 an alpha level of P 0.05. (mesiolingual) Results 2. 1 mMcalcium CF at pH 5.0 (mesiobuccal) 3.3 mMcalcium CF at pH 7.0 (distolingual) With I mMcalcifying fluids, lesion depths for both 4. 3 mMcalcium CF at pH 5.0 (distobuccal). nonacidulated (pH 7.0) and acidulated (pH 5.0) After tooth quarter preparation, a fluoride-free (Table, Fig 1) were significantly reduced (P < 0.05) toothbrush prophylaxis was performed to remove re- whencompared with that of the paired control lesions. sidual acidified gel from the specimens. Acid-resistant The body of the lesion depth was reduced by 18%with varnish was applied to the cut faces of the specimens the nonacidulated CF and by 29%with the acidulated CF. Acidulation of the 1 mMcalcium CF resulted TABLE. REMINERALIZATIONOF CARIES-LIKE LESIONS OF ENAMEL: in a further 14%reduc- EFFECTOF ACIDULATEDCALCIFYING FLUIDS tion in body of the lesion Surface Zone DepthBody of Lesion Reduction depth when compared (Mean + SD) Depth (Mean + SD) in Lesion Depth with paired lesions treated with the non- 1 mMcalcium calcifying~fluids acidulated CF (P < 0.05). The mean surface zone Control lesions 22-+ 5 l~m 187-+g’h 19 ~m depth with the acidu- 18% e r~ ’1 lated CF was increased Calcifying fluid at pH7.0 19_+4 Bma, 154_+15 ~mg,i, I 2.9%o by 18% (P > 0.05) and a’ f h’ 37% (P < 0.05) when Calcifying fluid at pH5.0 26_+ 4 lum 133+ 12 ~rn i, n compared with paired 10%I 3 rnMcalcium calciJidingyquids control lesions and 11% nonacidulated CF- treat- Control lesions 18b,c + 6 ~u-n 192k _+ 171.tmJ, ed lesions, respectively. 10%’1 With 3 mMcalcifying Calcifying fluid at pH7.0 29 _ 5 ~Ffl b’ d, e 172_+ 13 ~mi,t, m I 22%I fluids, acidulation re- 13% suited in a 22%reduc- Calcifying fluid at pH5.0 37 + 7 Brnc’ a, f 149-+ 15 l~nk’ 1, n I tion (P < 0.05) in mean body of the lesion depth when compared with ANOVA& DMR-paired sample results: meanswith same letters significantly different (P < 0.05). that for paired control and adjacent to the enamel windows, leaving two win- lesions (Table, Fig 2). In contrast, remineralization dowswith caries-like enamel lesions per tooth quarter the lesions with the nonacidulated CF produced a exposed. The 1 rnM and 3 mMcalcium calcifying flu- 10% decrease in lesion depth when compared with ids at pH7.00 _+ 0.02 and pH5.00 _+ 0.02 were prepared control lesions (P < 0.05). The body of the lesion from hydroxyapatite (Ca:P ratio = 1.63), with addition depth was reduced by 13%with acidulation of the 3 of sodiumchloride to adjust ionic strength and 0.05 mM mMcalcium CF (P < 0.05) when compared with the (1 ppm) fluoride. 12,13,17 The specimens underwent 10 nonacidulated CF. Surface zones from lesions treated separate 60-sec exposures to the assigned calcifying with either nonacidulated (61%) or acidulated (105%) fluid (2 ml/specimen). After each exposure period, the CFs had significant (P < 0.05) depth increases when specimens were rinsed with deionized distilled water compared with paired control lesions. Acidulation of for 30 min. After the final treatment and following the the 3 mMcalcium CF resulted in a further 28%in- water rinse, longitudinal sections from each tooth quar- crease in surface zone depth when compared with ter were taken, imbibed in water, and examined us- nonacidulated CF (P < 0.05). 206 American Academy of Pediatric Dentistry Pediatric Dentistry - 18:3, 1996 more reactive, somewhat porous enamel surface.19" -' It is well known that the acid-etch technique al- lows for creation of char- acteristic etching patterns and microporosities that Fig 1: Remineralization of caries-like lesions of enamel with 1 mm calcium calcifying fluid extend into the enamel to (arrow = surface zone; B = body of lesion; water imbibition, polarized light microscopy; depths of 50-100 pm; original magnification 250x). thereby allowing resin a. Representative paired lesion from control group. material to penetrate into b. Representative paired lesion remineralized with nonacidulated (pH 7.0) calcifying fluid. the etched enamel.23-25 c. Representative paired lesion remineralized with acidulated (pH 5.0) calcifying fluid. In contrast, the acidu- lation of topical fluoride agents provides a means for enhanced and rapid substitution of hydroxyl groups for fluorine ions.20"22'26"28 The incorpo- ration of fluoride into hy- droxyapatite produces a fluoridated hydroxyapa- Fig 2: Remineralization of caries-like lesions of enamel with 3 mm calcium calcifying fluid (arrow = surface zone; B = body of lesion; water imbibition, polarized light microscopy; tite, which has a signifi- original magnification 250x).