Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2005  |  Volume : 23  |  Issue : 4  |  Page : 171--178

Photographic appraisal of crystal lattice growth technique

DN Kapoor1, DV Mahendru2, VP Sharma2, P Tandon2,  
1 Kothiwal Dental College and Research Centre, Moradabad and Dental Faculty and Head of Orthodontics, KGMC Lucknow, India
2 Department of Orthodontics, KGMC, Lucknow, India

Correspondence Address:
D N Kapoor
Kothiwal Dental College and Research Centre, Moradabad and Dental Faculty and Head of Orthodontics, KGMC Lucknow


Concept of creating mechanical retention for bonding through crystal growth has been successfully achieved in the present study. By using polyacrylic acid, sulphated with sulphuric acid as etchant, abundant crystal growth was demonstrated. Keeping in view the obvious benefits of crystal growth technique, the present SEM study was aimed to observe and compare the changes brought about by different etching agents (phosphoric acid, polyacrylic acid and polyacrylic acid sulphated) and to evaluate their advantages and disadvantages in an attempt to reduce iatrogenic trauma caused due to surface enamel alteration. Control and experimental groups were made of 24 and 30 premolars, respectively, for scanning electron microscopic appraisal of normal unetched and etched enamel surface and fracture site and finished surface evaluation. When compared with conventional phosphoric acid and weaker polyacrylic acid, investigations indicated that crystal growth treatment on enamel surface caused minimal iatrogenic trauma and surface alteration were restored to the original untreated condition to a large extent.

How to cite this article:
Kapoor D N, Mahendru D V, Sharma V P, Tandon P. Photographic appraisal of crystal lattice growth technique.J Indian Soc Pedod Prev Dent 2005;23:171-178

How to cite this URL:
Kapoor D N, Mahendru D V, Sharma V P, Tandon P. Photographic appraisal of crystal lattice growth technique. J Indian Soc Pedod Prev Dent [serial online] 2005 [cited 2021 Jun 20 ];23:171-178
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Full Text

Tooth enamel lacks regenerative power, hence damage to enamel once caused is a permanent defect in the tooth structure. After being subjected to orthodontic bonding procedure (etching, bonding, debonding and finishing) and on completion of treatment, the altered enamel underlying the bracket is exposed to the oral environment for the remainder of life. Therefore, it becomes essential that following bonding and debonding, restoration of enamel surface should be attained as for as possible.

A new concept of building up a crystal layer for mechanical retention instead of creating a rough surface by means of strong etching has been studied. Crystal growth involves the application of an appropriate solution to a clean enamel surface, which interacts with the surface to form calcium sulphate dihydrate crystals, which serve as means of bracket attachment.

Keeping iatrogenic enamel loss to minimum as our prime objective and the obvious benefits of crystal growth technique in view this present SEM study was undertaken to:

1.Observe effect of crystal growth and different etching agents on enamel.

2.Compare the severity of these effects.

3.Study consequences of bonding, debonding and finishing procedures on tooth surface.

4.Estimate iatrogenic trauma.

5.Evaluate proximity of restoration of this altered tooth surface to untreated unaltered surface.

 Materials and Methods

The study comprised of 54 premolars extracted exclusively for orthodontic purposes divided into control and experimental groups of 24 and 30 teeth, respectively.

The control group was further divided into four subgroups of six teeth each for appraisal of normal unetched, phosphoric acid etched, polyacrylic acid etched and polyacrylic acid sulphated etched surface.

The experimental group comprised of three subgroups of ten teeth each on the basis of phosphoric acid, polyacrylic acid and polyacrylic acid sulphated surface treatment. Five teeth of each subgroup were randomly studied for occurrence of fracture-site and remaining five for finished surface evaluation.

All 54 samples were scanned and recorded photographically to be subjected to qualitative analysis.

Phosphoric acid used was obtained from Rely-a-Bond Orthodontic Bonding System Kit. Polyacrylic acid was glass ionomer liquid Shofu Inc., Japan, polyacrylic acid sulphated was prepared in the department as per specifications.[1]

All teeth in control group were cleaned with pumice slurry using polishing brush and their surface treated with specific acids. All 24 teeth were subjected to SEM examination. The surface alterations observed were considered as normal control standards for the experimental group.

In experimental group all 30 teeth also underwent similar prophylaxis and etch procedure. They were bonded using no mix direct bonding material as per manufacturer's instructions. Bracket was positioned mesiodistally in the centre of facial surface and 3.5 mm occlusogingivally from the buccal cusp tip. Bracket bonded teeth were kept for 24 h to ensure complete polymerization. The bracket were subsequently debonded using debonding pliers.[2] Fracture site occurrence was studied under SEM and recorded. Residual adhesive on tooth surface was assessed visually and clinically using an explorer and scored according to adhesive remnant index (ARI) parameters as per criteria laid down by Artun and Bergland.[3] Teeth with an ARI score of 2-3 were finished using 12 fluted tungsten carbide bur.[4],[5] Final finishing of all teeth was done with pumice slurry and polishing brush to reduce surface roughness. These teeth were also recorded after SEM examination.

Teeth were sectioned along cemento-enamel junction and central fossa to separate the buccal cusp. The sectioned cusp was mounted onto an aluminium stub, the specimen prepared and subjected to SEM examination. Viewing was initially done at a lower (15) magnification and then at higher (1000). For qualitative analysis, visual representative photographs were taken on X mode and surface roughness by amplitude variation was assessed on Y mode.

In the present study, a comparison has been done between normal unaltered, phosphoric acid, polyacrylic acid and polyacrylic acid sulphated treated enamel surface at etching, bonding, debonding and finishing stages. This comparison has not been reported before. Scanning electron microscopic photographic surface roughness amplitude variation on basis of Y - mode interpretation has also been reported for the first time in the present study.

The values were subjected to statistical analysis as evident in [Table 1][Table 2][Table 3][Table 4]


Control group


Removal of pellicle layer on prophylaxis exposes typical paddle shaped keyhole appearance of enamel, with superficial perikymata (Orbans[6]) [Figure 1]. Natural regular surface unevenness of enamel is represented by uniform low intensity amplitude deviations [Figure 2].

Phosphoric acid

Characteristic keyhole pattern has been transformed to peripheral etch pattern (Diedrich[7]) [Figure 3]. Severe roughening of enamel has occurred as evident by closely placed high intensity amplitude variation when compared with normal [Figure 4].

Polyacrylic acid

Nonuniform indentations show disturbed keyhole pattern (Smith[8]) [Figure 5]. Surface amplitude fluctuation has enhanced from normal but divergence is not as severs [Figure 6] as in the phosphoric acid subgroup.

Polyacrylic acid sulphated

A dense growth of long, needle shaped, spherulitic crystals is uniformly spread all over the etched area [Figure 7] obscuring normal enamel.[9],[10] Intense amplitude fluctuations with high peaks and closed proximity show drastic increase in surface area [Figure 8] similar to that observed by phosphoric acid etch.

Experimental group

Phosphoric acid fracture site

Fracture seen at bracket-adhesive interface. Almost 100% retained adhesive with bracket base mesh imprinted visible [Figure 9]. ARI score 2-3 exposed enamel is significantly transmuted with large adhesive remnants. Surface does not resemble either normal or phosphoric acid etched surface [Figure 10].

Polyacrylic acid fracture site

Fracture occurred at enamel-adhesive interface. All adhesive has been removed exposing underlying etched area [Figure 11]. ART score is 0-1. Perikymata is visible. Exposed enamel resembles polyacrylic acid etched surface. Traces of residual adhesive are seen [Figure 12].

Polyacrylic acid sulphated fracture site

All fractures have occurred at enamel-adhesive interface. Central etched area is well differentiated from bordering unetched enamel. Perikymata is visible. Residual adhesive is absent [Figure 13]. ARI score is 0. Thin residual layer of crystal growth has persisted even after debonding [Figure 14].

Phosphoric acid finished surface

No normal enamel structure are seen. Rough tooth surface with impregnated residual adhesive seen [Figure 15]. Even after final finishing enamel does not resemble unaltered tooth surface at all reduction from extreme peak variation in phosphoric acid control subgroup to lesser variant amplitude fluctuation is seen [Figure 16].

Polyacrylic acid finished surface

Surface shows faint resemblance to polyacrylic acid etch pattern seen in control subgroup. No residual adhesive remnants are distinguishable. Enamel surface appears smooth [Figure 17]. Amplitude variations are more [Figure 18] than those presents in phosphoric acid finished surface subgroup.

Polyacrylic acid sulphated finished surface

Crystal residues have been removed exposing altered enamel surface resembling polyacrylic acid control subgroup. Etch pattern is clearly visible [Figure 19]. Peak of amplitude and the proximity of their spacing has dramatically reduced [Figure 20]. Compared with polyacryl acid sulphated control subgroup.


Control group


Paddle shape pattern represent rods, rodsheath and interprismatic substance.[6] Variation in amplitude is detected due to high and lows created on enamel surface by height of interprismatic substance and depth of prism core. Uniformly spaced deviations of low intensity indicate an overall regular uneveness of enamel surface to create a smooth surface structure.

Phosphoric acid

Strong etching has accentuated the key hole pattern by selective dissolution of interprismatic substance forming peripheral etch pattern (Diedrich).[7] Photographically, exaggerated depth variation are distinctly evident. Intensification of surface roughness is depicted by increased amplitude peak indicating severe difference between height and depth of enamel structures. As compared with unetched enamel, enhancement of surface area is clear.

Polyacrylic acid

Weak polyacrylic acid has caused mild etching of rods in enamel. Photographic estimation of amount of enamel loss, as seen by topographic alterations, is much less when compared with that caused by phosphoric acid etch u. Increase in surface area is not as drastic as achieved with phosphoric acid. Surface amplitude fluctuations have enhanced when compared with unaltered enamel. But peaks of amplitude are not as severe and proximity of spacing of these fluctuations is not as close as in phosphoric acid subgroup.

Polyacrylic acid SO4

Expected mildly etched enamel by polyacrylic acid action can not be viewed due to presence of crystal growth. The calcium sulphate dehydrate crystals formed by the interaction of sulphate ions in acid with calcium ions etched out of enamel, are dense, long and typically spherulitic. As the basic etch has been caused by weak polyacrylic acid, loss of enamel substrate is much less but the drastic surface area increase pattern is similar to the observed with phosphoric acid. Basic difference is that, in phosphoric acid subgroup, increase in surface area was because of loss of interprismatic substance from within the tooth but in polyacrylic acid sulphated subgroup increase in surface area is achieved by formation of crystals over enamel surface with minimum loss from within enamel. The advantage of polyacrylic acid etch of reduced enamel loss and of phosphoric acid etch of increased surface area have been combined in polyacrylic acid sulphated etch.

Experimental group

Phosphoric acid fracture site

Dental resin has flown into spaces created by etched out interprismatic substance to form tags for mechanical retention. Lower bond strength at adhesive-bracket interface than at enamel-adhesive interface, have resulted in bracket-adhesive as fracture site.[3] Exaggerated depth of resin tag penetration have retained almost 100% adhesive onto tooth surface resulting in ARI score of 2-3. Where tagging was less, fracture has occurred at enamel-adhesive interface exposing transmuted tooth surface. This significantly altered enamel shows areas where resin has been retained mixed with areas from where tags have been pulled out on debonding causing iatrogenic trauma.[11],[12] Debonded surface shows no resemblance to keyhole pattern of normal enamel on peripheral etch of phosphoric acid treated enamel.

Polyacrylic acid fracture site

As etching effect in mild, resin penetration is shallow resulting in reduced adhesion of resin to tooth. Bond strength at adhesive-bracket interface is more than at enamel-adhesive interface leading to fracture site being enamel-adhesive. Shallow penetration has also led to pulling out of resin tags exposing etched out area. Few, if any resin tags have been let behind. Alteration of enamel surface is superficial, i.e. upto 20-25 mm as perikymata are distinctly visible. Bonding and debonding procedures have not significantly altered enamel, which resembles polyacrylic acid etched surface.

Polyacryylic acid sulphated fracture site

Basic etch is caused by polyacrylic acid hence all features are similar to ones observed in polyacrylic acid fracture site subgroup. All fracture have occurred at weaker enamel adhesive interface[3],[13],[14] with no residual adhesive[3],[15] and perikymata are visible on etched patch exposed on debonding. No tooth surface is visible due to persistence of spares layer of crystals which has resisted removal from enamel surface even after bracket has been debonded showing that calcium sulphate dehydrate crystal are strongly attached to underlying polyacrylic acid etched enamel. Persistance of crystal layer also indicates that resin has not come in direct contact with enamel surface at all and that crystals act as a barrier from resin onslaught. All the possibilities of iatrogenic enamel loss due to resin penetration on bonding and subsequent tag pulling and retention on debonding have been eliminated.

Phosphoric acid finished surface

As the ARI score is 2-3, the debonded surface needed subjection to finishing with 12 fluted tungsten carbide bur. Final finishing was done with pumice slurry using polishing brush. On SEM examination no normal structure could be perceived and surface is significantly rough and altered. Due to excessive depth of penetration, tags have not entirely been pulled out on debonding. Residual adhesive fragments are still impregnated and have fractured at enamel surface, some have been pulled out and rest have been leveled to surface by finishing action of tungsten carbide bur. Substantial enamel loss and permanent alteration have resulted in a finished surface drastically different form that of normal enamel (Casperson[16] and Gwinnett and Gorelick[17]). Amplitude variation has reduced when compared with phosphoric acid control subgroup due to false smoothening of enamel by filling in of etched out areas with resin. Substrate loss during etching has been leveled by creation of resin tags. Where resin has been pulled out, high intensity peaks are still present. Even though surface looks smooth, eventual roughening is expected due to resin tag drop outs when wearing of tooth surface occurs.

Polyacrylic acid finished surface

With an ARI score of 0-1, no tungsten carbide finishing was required. It left enamel free of scratches caused by rotary action. Pumice finishing left surface smooth as compared to rough surface exhibited by phosphoric acid finished surface. Finished surface does not resemble unetched surface but is similar to polyacrylic acid etched surface. No residual adhesive is observed indicating that all adhesive had been removed due to shallow penetration. Amplitude peaks have more fluctuation than the variation seen in phosphoric acid finished surface subgroup, as no leveling of etched enamel is achieved by retention of resin tags. Even though polyacrylic acid finished surface is rougher than phosphoric acid finished surface, it is a static state as there will be no resintag drop outs and enamel smoothness will only be enhanced by natural wearing of tooth surface.

Polyacrylic acid sulphated finished surface

With an ARI score of 0 only pumice finishing was done (Artun and Bergland).[3] Enamel is saved from the trauma caused by rotary finishing. Crystal left after debonding have cleared off exposing underlying polyacrylic acid etched enamel. As adhesive has not come in contact with enamel at all, etch pattern is also distinctly visible. Since no filling in of etched area with resin had occurred, surface appears relatively rough. But surface roughness is superficialas perikymata are still visible and much less than the permanent deep roughness caused by phosphoric acid etching and debondmg procedures. As compared with polyacrylic acid finished surface subgroup, polyacrylic acid sulphated finished surface is not much altered. Natural wearing of tooth surface is forecasted to smoothen out the superficially roughened enamel. Peaks of amplitude fluctuations as well as the proximity of their spacing has reduced drastically as compared to peaks observed in polyacrylic acid sulphated control subgroup and become similar to those seen in polyacrylic acid control subgroup. This clearly indicates that the drastic increase in surface area is caused by crystal growth layer itself and not due to substantial tooth loss as in phosphoric acid group. Consequently iatrogenic enamel loss has been reduced at every stage of etch, bond, debond, and finishing procedure with polyacrylic acid sulphated. From the present in vitro scanning electron microscope photographic evaluation study undertaken, it was concluded that topographically, untreated enamel surface exhibits uniformly uneven surface. Phosphoric acid etch provides substantial loss within enamel as well as bonding and debonding presents a much altered enamel surface. Polyacrylic acid causes mild etching, which is restricted to superficial layer there by presenting comparatively reduced enamel loss and unnoticeable tooth topographic transformation. Crystal growth seems to open a wide spectrum of realistic modifications and improvements in the scope of etching technique to make bonding most beneficial to both, the patient and the clinician.

According to the present study conducted when compared with conventional phosphoric acid and weaker polyacrylic acid, investigations indicate that crystal growth enamel surface treatment technique causes minimal iatrogenic trauma during etching, bonding, debonding and finishing procedure and surface alteration can be restored to the original untreated condition to a large extent. Crystal formation protects enamel surface from onslaught of adhesive and totally eliminates retention of adhesive remnants. At the same time, the merits of acid etching technique of increased surface energy and enhanced surface area are also met with satisfactorily.


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