ADDITIVE dentistry and MODIFIED 3 STEP technique to treat a case of Initial Dental Erosion Using Pressed Lithium Disilicate Ceramic Restorations: A 6 year follow-up case Report
Dental erosion is spreading rapidly among younger generations of patients. Clinicians often underestimate the extent of this disease and postpone its treatment due to a lack of awareness and/or to uncertainty regarding the proper course of action.
The discussion of when and how to treat young individuals affected by dental erosion has split the dental community into two groups: clinicians who treat eroded teeth excessively and clinicians who do not treat eroded teeth at all.
In this case report, a young adult patient affected by generalized dental erosion was treated even though his tooth degradation was only at an initial stage. The rationale behind this early intervention was that no or minimal tooth preparation would have been required for treatment. In fact, only ADDITIVE adhesive procedures were implemented to replace the missing tooth structure and protect the remaining dentition from further damage.
A 25-year-old male Caucasian patient presented to the School of Dental Medicine at the University of Geneva, Geneva, Switzerland. His chief complaint was the weakening and fracturing of his maxillary incisal edges. During a previous dental consultation, a parafunctional habit (bruxism) was suggested as the main cause of lost tooth structure; however, no occlusal guard had been prescribed. Clinical examination revealed that the patient also showed generalized initial dental erosion.
The patient presented accelerated loss of enamel, especially on the palatal aspect of the maxillary anterior teeth and occlusal surfaces of the premolars. In addition, the mandibular first molars presented concave occlusal surfaces with reduced areas of contact with the antagonistic teeth. Wear facets at the canines were also present, indicating moderate parafunctional habits. The remaining dentition was intact.
The patient was questioned regarding the possible etiology of the dental erosion, and he denied any excessive consumption of acidic beverages or food. The clinician recommended further investigation of a possible intrinsic origin of the acid (e.g, gastric reflux) through a visit to a gastroenterologist. However, the patient did not comply with this suggestion, and the etiology of the dental erosion remained unknown.
Anterior erosive classification (ACE)1 was used to determine the extent of erosion. Following the examination, the patient’s erosion was classified as ACE class III because the palatal dentin was exposed at the level of the contact points with the antagonistic mandibular teeth and the incisal edges were starting to fracture (loss of less than 2.0 mm of the original tooth length). Since reduced vertical overlap (overbite) was a risk factor for accelerated damage of the incisal edges and the etiology of the problem was still unknown, the potential for a higher ACE classification was a concern.
The benefits of early intervention were discussed, with special consideration paid to the young age of the patient. It was decided to restore the patient’s affected teeth with no or minimal tooth preparation following exclusively adhesive principles.
ACE class III maxillary anterior teeth can be restored using only palatal veneers. To obtain the necessary interocclusal space to deliver the restorations without tooth preparation, an increase of the vertical dimen-sion of occlusion (VDO) should be considered as long as no orthodontic measures are implemented. Since the posterior teeth also showed signs of dental erosion, it was decided to increase the VDO by restoring the posterior teeth as well.
In addition to the loss of tooth structure related to dental erosion, the patient presented esthetic problems at the maxillary central incisors. Even though the facial aspect of these teeth was intact (except for their incisal edges), their coloring was darker compared to the rest of the dentition. Several unsuccessful attempts at external bleaching had been made in the past. The central incisors had changed color following prior trauma to the anterior teeth. At the radiographic examination, both pulp chambers were obliterated, and the vitality test was negative. However, neither radiographic signs of periapical lesions nor symptoms related to a loss of vitality were evident. The percussion test was also negative. After consultation with an endodontist, it was decided to maintain the status quo without performing elective endodontic therapy until signs or symptoms of pulp necrosis arose. Consequently, two facial veneers were also planned to mask the discoloration.
Delivering two veneers, one palatal and one facial, to restore a single tooth is called the “sandwich approach,” which has been proven to be the most conservative treatment for ACE class IV to VI anterior teeth. However, in this ACE class III patient, the sandwich approach was dictated more by the patient’s esthetic demands than by loss of tooth structure.
MODIFIED 3 STEP Technique
Generally, patients affected by dental erosion are treated following the 3 STEP technique.2–4 Due to the early detection of the erosion, this patient did not require full-mouth rehabilitation. Thus, a MODIFIED 3 STEP technique was used.
The typical first step (the maxillary vestibular mock-up) was not necessary because the esthetic occlusal plane did not required major alteration and the shape of the maxillary anterior teeth needed only minor modification (lengthening of the incisal edges of few millimeters). Instead, treatment began directly with the increase of the VDO and creation of anterior open bite (step 2). Due to the minimal increase of the VDO, no provisional restorations were necessary to test the increase of VDO. Consequently, instead of the posterior provisional stage in the CLASSIC 3 STEP technique, final restorations for the posterior teeth were fabricated.
During the first visit, two alginate impressions were taken, and casts were mounted on a semi-adjustable articulator using a face bow in maximum intercuspal position (MIP). The VDO was arbitrarily increased to obtain the space necessary to restore the occlusal surfaces of the posterior teeth and the palatal aspect of the maxillary anterior teeth.
The space gained in the posterior quadrants by the increased VDO was shared between the maxillary premolars and mandibular molars. Posterior support at the increased VDO was obtained only by insertion of the eight ceramic onlays for the premolars. The remaining posterior teeth were not involved in the restorative treatment.
Once this stage of treatment was finalized, the patient was scheduled for another appointment. The final impression of the maxillary and mandibular arches was made using polyvinyl siloxane to fabricate the working casts.
POSTERIOR CERAMIC ONLAYS
An ADDITIVE diagnostic wax-up was used as the starting point for fabrication of exceptionally thin and highly conservative posterior lithium disilicate ceramic onlays. Developing thin occlusal ceramic onlays while simultaneously providing adequate occlusal function is a complicated procedure. Conventional ceramic on-lays require a minimum thickness of 1.5 to 2.0 mm, whereas thin occlusal ceramic onlays have a maximum thickness ranging from 0.5 to 0.6 mm. These highly conservative restorations can be produced with mini-mal or no tooth reduction and are highly indicated to restore eroded posterior teeth.
Thin occlusal ceramic onlays are very fragile and may fracture during waxing or fabrication procedures. The first step is to make the investment casts. The working casts must be duplicated in the investment. The working casts are painted with die spacer (Color Spacer, Yeti Dental, Engen, Germany) and then duplicated using polyvinyl siloxane (Zhermack Elite, Zhermack, Badia Polesine, Italy) and phosphate-bonded investment material (IPS Press Vest Speed, Ivoclar Vivadent)
The wax-up of the occlusal onlays must be made directly on the investment replica following the morphology obtained in the wax-up. Waxing directly to the investment is a far more delicate procedure than waxing directly on the microstone. Since investment material is less rigid than stone, contact of the hot waxing instrument on the investment may damage its surface, resulting in permanent distortion.
Correct placement of the sprue is crucial during the fabrication of thin occlusal ceramic onlays. An inadequate placement and amount of wax for the sprue may result in loss of the ceramic onlay’s peripheral contour. A solution for this drawback is to wax the sprue directly over the investment. This procedure allows better contour and marginal fit without removing the wax before investment into the cylinder. Once the restorations are waxed with the correctly located sprue, the investment material surrounding the restorations is carefully trimmed, leading to individual waxed invest-ment dies. Trimming the investment around the waxed tooth facilitates positioning into the investment ring. However, before positioning the whole set into the investment ring, the investment dies should be soaked in alcohol to prevent them from absorbing moisture from the investment coating too quickly.
The thin occlusal onlays were made with a highly opalescent shade ingot (Impulse 01, IPS e.max Press, Ivoclar Vivadent) to match the natural teeth.
According to the manufacturer, opal ingots can be used as enamel replacements because of their optical properties and adequate strength. To provide suitable optical properties, the maximum thickness of the opalescent ingot must not exceed 0.5 to 0.6 mm. Thicker restorations often result in an undesirable increase in value. The final step is to glaze the restorations as recommended by the manufacturer.
The patient was informed that the third appointment would have been a long one since the eight ceramic on-lays had to be inserted in the same visit. No anesthesia was required, and the field was isolated with rubber dam. Figures 16 to 23 demonstrate the placement procedures. Enamel was etched (37% phosphoric acid) for 30 seconds, and the adhesive resin (Optibond FL, Kerr, Orange, California, USA) was applied on the teeth and left unpolymerized.
The pressed lithium disilicate glass-ceramic onlays were etched with hydrofluoric acid for 20 seconds and cleaned in alcohol in an ultrasonic bath. Three coats of silane were applied (Monobond Plus, Ivoclar Vivadent) to the intaglio surfaces of the restorations, and a final layer of the adhesive resin was added without curing.
A microhybrid composite resin (Enamel plus, Micerium, Avegno, Italy) was heated and applied to the restorations before they were placed on the teeth and light polymerized. The challenge was to bond the ceramic onlays while maintaining the original interproximal contacts. In addition, the extremely thin onlays required additional attention to avoid fracture during the bonding procedure.
The patient’s new occlusion was controlled after 1 week to intercept occlusal interferences. The patient was comfortable, and no signs of temporomandibular joint disorders were detected.
In the following appointment, the palatal aspect of the maxillary anterior teeth was prepared for the palatal veneers. All exposed dentin was immediately sealed without anesthesia. The palatal dentin was cleaned with non-fluoridated pumice, and the most superficial layer was removed with diamond burs. The exposed sclerotic dentin was etched with 37% phosphoric acid for 15 seconds and immediately sealed with three-step etch-and-rinse ethanol- and water-based adhesive (Optibond FL) and flowable composite resin (Tetric Flow T, Ivoclar Vivadent) just before the final impression was taken.5–9
Finally, the irregular margins of the incisal edges were smoothed. No additional tooth preparation was necessary. The interproximal contacts between the maxillary anterior teeth were left closed, and the final impression was taken using metal strips in between the teeth, as for the posterior teeth. No provisional restorations were delivered.
It was decided to fabricate the palatal veneers in pressed lithium disilicate glass-ceramic (IPS e. max Press) for the maxillary lateral incisors and canines and in composite resin (Adoro, Ivoclar Vivadent) for the maxillary central incisors. The presence of composite resin on the palatal aspect would facilitate not only the bonding procedure with the future ceramic facial veneers (sandwich approach), but also the eventual creation of an access hole for future root canal treatment.
The same laboratory technique described for the thin occlusal ceramic onlays was adopted for the palatal veneers, with the exception of those for the maxillary central incisors. For the central incisors, a laboratory microfilled composite resin was used.
After 2 weeks, the six palatal ceramic veneers were bonded, one at a time, under rubber dam without anesthesia. A three-hour appointment was necessary. The sealed palatal dentin was tribochemically coated (Cojet, 3M ESPE, St Paul, Minnesota, USA), the surrounding enamel was etched with 37% phosphoric acid for 30 seconds, and the adhesive (Optibond FL) was applied to the enamel and dentin and left uncured.
The intaglio surfaces of the palatal composite resin veneers were also tribochemically coated. The four pressed ceramic palatal veneers were etched with hydrofluoric acid for 20 seconds.
All veneers were cleaned in alcohol and placed in an ultrasonic bath, followed by the application of three coats of silane (Monobond Plus). A coat of the adhesive resin was placed and left unpolymerized. Composite resin (Enamel plus) was heated and applied to the restorations before they were placed on the teeth and then light polymerized for 90 seconds for each surface.
To complete the treatment, the next step was the restoration of the facial aspect of the maxillary central incisors. Unfortunately, the initial position of these teeth was very labial. To keep the tooth preparation to a minimum, the prospect of a slightly bulkier facial surface was discussed with the patient (ADDITIVE approach). Thanks to the preview provided by the mock-up on the central incisors, the patient agreed to the slightly thicker teeth. The option to restore the facial aspect of the lateral incisors was not considered due to the principle of minimal invasiveness. Unfortunately, minimal tooth preparation of the central incisors was inevitable due to their dark yellowish color. Facial veneers with a thickness of 1.0 mm were necessary to mask the underlying color. Because the teeth did not respond to the vitality test, no local anesthesia was necessary for the preparation.
After the final impression, provisional restorations were fabricated directly in the mouth using a provisional composite resin material (Telio, Ivoclar Vivadent), and retention was achieved by the contraction of the product and the presence of minimal interproximal excess.
The labial veneers were fabricated using the refractory die technique and feldspathic porcelain. Ceramic layering was performed to better match the color and optical details of the adjacent anterior teeth. These highly translucent facial veneers blend easily with the underlying preparation.
Bonding of the feldspathic ceramic veneers was carried out after 2 weeks, following the protocol developed by P. Magne.10–14 Final external bleaching provided a pleasing esthetic outcome. The patient was very satisfied with the overall treatment. In terms of biologic success, no tooth preparation was performed for this almost full-mouth rehabilitation except for the facial surfaces of the maxillary central incisors.
The incisal edges of the maxillary anterior teeth were reinforced by the presence of the restorative materials, the exposed dentin was covered, and the thinner enamel was also reinforced. An occlusal guard was delivered to the patient to control his light para-functional habit, and a visit to a gastroenterologist was again recommended.
At the 6-year follow-up, non signs of degradation of the restorations were visible. The patient was very happy with the overall rehabilitation, since in 3 visits (MODIFIED 3 step technique) the damage related to the dental erosion had been repaired without any healthy tooth structure preparation.
This article presented a case report of a patient affected by initial dental erosion. Early intervention was performed due to the exposed dentin and risk of fracture of the anterior teeth. Only time will tell if this type of early and minimally if not invasive approach is the best solution for patients affected by initial dental erosion.
The Italian version of this article exists just thank to the help of several people. The authors strongly thank (in alphabetical order) Fortunato Alfonsi, Ciro Bocchetti, Davide Foschi and Giuseppe Puma.
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