TREATMENT FOR TEETH WITH INCOMPLETE FRACTURES

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The restorative treatment for a tooth with an incomplete fracture involves the placement of a restoration that prevents independent movement of the tooth segments on either side of the crack.^3,8 Traditionally, this treatment involves either a cuspal-coverage pin-retained amalgam restoration or a cast-metal cuspal-coverage restoration. Restoring the cracked tooth with amalgam has been shown to resolve symptoms predictably and requires less time than that needed to fabricate and insert a cast restoration.^8,9

In the case of amalgam restorations retained with either threaded pins or amalgapins, pulpal symptoms are alleviated by binding together the fractured portions of the tooth. Mechanical retention placed on either side of the crack allows the overlying amalgam restoration to create a splint for the fracture, preventing independent movement of the fractured segments. In addition, the overlying amalgam distributes the occlusal load over a large area of the tooth, reducing the stresses along the line of fracture. Self-threading pins and amalgapins also have been shown to provide excellent resistance to displacement of complex (cuspal coverage) amalgam restorations.^10,11

Threaded pins. The use of threaded pins is not without disadvantages. An in vitro investigation by Webb and colleagues¹² demonstrated that self-threading pins frequently are placed into or near the pulp. These investigators found that even when pins did not enter the pulp, pin placement resulted in dentinal crazing severe enough to reach the pulp in 73 percent of the cases. Felton and colleagues¹³ conducted an in vivo study to examine the effects of threaded-pin placement on pulpal inflammation. The results of their study showed that pins placed in the vicinity of the pulp resulted in inflammatory changes within the pulp.

Amalgapins. Amalgapins have been found to create virtually no dentinal crazing, and have provided resistance to restoration displacement equivalent to that of threaded pins.¹¹ The primary disadvantage related to the use of slots and amalgapin-type resistance features is the propensity for the restoration to undergo a fracture when the matrix is removed.¹⁴ Although amalgapins require less dentin penetration than self-threading pins (1- to 1.5-millimeter depth for amalgapins vs. 2 mm for self-threading pins), both methods of pin placement require the removal of tooth structure to the extent that the dental pulp might be approached.^15,16

Resin adhesive agents. Resin adhesive agents offer a means of providing resistance and retention to complex amalgam restorations that avoids the need to remove more tooth structure than is required for basic cavity preparation.¹⁷ Burgess¹⁸ and Imbery and colleagues¹⁹ conducted in vitro studies and found that resin adhesives were capable of providing more resistance to dislodging forces than conventional self-threading pins. These in vitro findings were validated by in vivo research supporting the efficacy of using adhesively retained complex amalgam restorations. In two independent clinical trials, amalgam bonding agents proved to be effective in retaining complex amalgam restorations.^20,21 Although these ongoing studies cannot be considered long-term at this juncture, the two-year findings of Belcher and Stewart²¹ included a 100 percent retention and a 0 percent incidence of sensitivity in adhesively bonded complex amalgam restorations.

Clinical and laboratory studies indicate the potential of amalgam adhesives to retain complex restorations and seal dentinal tubules.^22–24 However, no clinical studies have been reported that assess the efficacy of these adhesive agents in treating the symptoms of incomplete tooth fracture. Consequently, the objective of this study was to compare resin-bonded complex amalgam restorations with conventional pin/amalgapin–retained complex amalgam restorations in regard to resolution of chewing pain and cold sensitivity in teeth with incomplete fractures.

The objective of this study was to compare resin-bonded complex amalgam restorations with conventional pin/amalgapin–retained complex amalgam restorations in regard to resolution of chewing pain and cold sensitivity in teeth with incomplete fractures.

	MATERIALS AND METHODS

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Patient selection. Thirty-eight adult volunteers were selected from among patients who came to a military dental clinic with symptoms suggesting incomplete tooth fracture. Each prospective subject was interviewed and examined by one of the two investigators. The nature and purpose of the study were discussed, and patients who expressed interest in participating in the study were evaluated further to determine if they satisfied the study’s inclusion criteria. To participate in the study, each patient had to have a complaint of chewing pain that could be localized to a specific molar that had the following characteristics:

– demonstrated pain on chewing only and was not sensitive to percussion testing or to closing the teeth together into maximum intercuspation;

– demonstrated a vital response to thermal (cold) pulp testing;

– demonstrated no spontaneous pain or lingering discomfort (longer than 45 seconds) to a cold stimulus;

– demonstrated less than Class II mobility;

– demonstrated no periodontal pocket greater than 5 mm;

– could be restored without pulp capping or pulp exposure.

In addition to satisfying the aforementioned criteria, candidates for the study were required to exhibit—via a medical history—no medical contraindications to restorative dental treatment that involved administration of local anesthetic (2 percent lidocaine containing epinephrine in a ratio of 1:100,000). A commercially available fracture-finding device (Frac Finder, Hu Friedy Co.) was used to assist in locating incomplete tooth fractures. Of the 38 patients who were enrolled in the study, two had two cracked teeth. Thus, a total of 40 molars with incomplete fractures were evaluated in this investigation. We completed all of the preoperative and postoperative evaluations, as well as placed all of the restorations.

Preoperative protocol. After the initial interview and dental examination, patients completed the necessary documentation for giving informed consent. Each patient was then given specific instructions regarding the use of the visual analog scale, or VAS, which was to be used to record cold sensitivity data. When using the VAS, patients were asked to place a mark on the 10-centimeter line indicating the intensity of their discomfort (the left end of the scale denoted no discomfort [a measurement of 0] and the right end denoted severe pain [a measurement of 100]). The distance of each mark from the left end of the scale, measured in millimeters, was used as a measure of each patient’s perception of cold sensitivity.

Preoperative levels of chewing pain and cold-related sensitivity were documented. To assess chewing pain, we used the fracture-finding device and recorded the patient’s response. Possible responses to the chewing tests were limited to painful or not painful. All patients exhibited preoperative chewing pain (as specified in the inclusion criteria for the study). The cold test consisted of placing a cotton pellet soaked in an ethyl chloride skin refrigerant (Fluro Ethyl, Gebauer Co.) against the facial surface of the tooth with the incomplete fracture for five seconds. Patients recorded their perceived cold sensitivity on the VAS. Patients whose cold sensitivity lingered longer than 45 seconds were excluded from the study. Discomfort lingering for more than 30 seconds was noted. Five patients demonstrated discomfort from the cold stimulus that lasted between 30 and 45 seconds. We then made preoperative photographs of the fractured tooth using a 35-mm intraoral camera.

Restorative protocol. Patients were randomly assigned to one of the two treatment groups. Cracked teeth of patients in group 1 were restored with mechanically retained complex amalgam restorations. Patients in group 2 were treated with adhesively retained complex amalgam restorations. The mean (± standard deviation) age of patients in group 1 was 41.1 years (± 11.1 years) and 38.9 years (± 14.4 years) for patients in group 2. There were 14 men and five women in group 1 and 12 men and seven women in group 2.

Using 2 percent lidocaine with 1:100,000 epinephrine and standard dental techniques, we administered the local anesthetic. We used a rubber dam to isolate the teeth in the quadrant of the patient’s dentition that contained the cracked tooth. An air rotor high-speed handpiece and tungsten carbide burs were used for the majority of tooth preparations. Air-water spray was used for all preparations involving the high-speed handpiece. Existing restorations and weakened tooth structure were removed, and cusps over the fractured area of the tooth were reduced. Cusps were also reduced where, in the opinion of the dentist, they were at risk of being fractured because of inadequate dentin support. Carious tooth structure was removed with a slow-speed handpiece and round burs or a spoon excavator. Beyond this initial stage of preparation, the cavity design varied according to group assignment.

Group 1 (nonbonded). Areas of the tooth in which self-threading pins were to be placed were reduced by approximately 4 mm. We reduced all other areas to be restored by approximately 2 mm. At least one self-threading Thread Mate System, or TMS, 0.024-inch pin (Coltene/Whale-dent Inc.) or an amalgapin was placed on either side of the fracture line. If fracture lines were not visualized, retention features were placed such that, in our estimation, at least one TMS pin or amalgapin was located in the fractured portion of the tooth (previously identified during testing), and one was located elsewhere in the tooth. When self-threading pins were used, they were extended 2 mm into the dentin. We then used a diamond bur to reduce them in height so that 2 mm of pin was left to extend into the amalgam.

Amalgapins were prepared with a number 330 bur and were approximately 1 mm in width and 1.5 mm in depth. Figure 1 depicts a typical threaded-pin–retained preparation. A low-viscosity resin (Prime and Bond 2.1, DENTSPLY/L.D. Caulk) was placed on the prepared tooth and polymerized before the amalgam was placed to act as a dentin-sealing agent. The resin was placed according to the manufacturer’s directions without the use of a separate acid-etch step. The sealer was polymerized for 20 seconds with a light-activating unit (The Max, DENTSPLY/L.D. Caulk). We placed a matrix band using modeling compound for external matrix reinforcement.

View larger version (69K): [in this window] [in a new window]   Figure 1. A typical threaded-pin–retained preparation.

View larger version (77K): [in this window] [in a new window]   Figure 2. A typical cavity preparation for an amalgapin-retained restoration and an adhesively retained restoration.

We gave patients postoperative instructions that included advising them to avoid chewing on the restored tooth for at least eight hours, but to resume normal chewing function on the tooth the next day. Patients were also advised to contact the dental clinic if more-than-mild postoperative discomfort occurred. No patients sought follow-up care for postoperative discomfort. Finally, we scheduled patients for postoperative visits.

Postoperative assessments. Recall evaluations were performed two weeks, three months and 12 months after the restorations were placed. Chewing pain and cold sensitivity were assessed during these postoperative evaluations.

Chewing pain. We asked each patient if he or she had used the restored tooth for chewing and if chewing pain had been experienced in the area of the restored tooth. Responses were recorded as being painful or not painful. When a painful response was recorded, we used the fracture-finding device to determine whether the symptoms originated from the restored tooth or another tooth in the area.

Cold sensitivity. A cotton pellet saturated with ethyl chloride skin refrigerant was applied to the buccal surface of the restored tooth for five seconds. The patient recorded his or her response on the VAS. We noted any pain that lingered for more than 30 seconds.

Patients were questioned about the occurrence of spontaneous pain after the restoration was placed. We used a ² test to compare the incidence of chewing pain between the two groups ( = .05). A paired t-test ( = .05) was used to compare differences between preoperative and postoperative cold sensitivity levels for each tooth in each group.

	RESULTS

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Table 1 shows the distribution of teeth with incomplete fractures according to tooth type and group assignment. At the preoperative examination, cold sensitivity was found to be similar among patients in the bonded group and the non-bonded group. Mean (± SD) VAS sensitivity score measurements at the preoperative evaluation were 43.6 (± 33.2) for patients in the nonbonded group and 41.0 (± 31.2) for patients in the bonded group. A Student’s t-test revealed no significant difference between the groups (P > .05). Three patients in the nonbonded group and two patients in the bonded group experienced discomfort that lingered for 30 to 45 seconds after application of the cold stimulus at the preoperative evaluation.

Three-month evaluation. At the three-month evaluation, chewing pain had returned for one patient in the nonbonded group. Chewing tests verified that the discomfort was localized to the tooth that had been treated for incomplete fracture. This tooth had been restored with a complete cuspal-coverage amalgam restoration with threaded-pin retention.

At the three-month assessment, the mean VAS sensitivity score was 32.6 (± 34.3) for patients in the nonbonded group and 17.1 (± 20.8) for patients in the bonded group. A paired t-test showed that the teeth in the bonded group were significantly less sensitive to cold after three months than at the time of the baseline measurements (P < .0001). This analysis showed no significant difference between preoperative and postoperative cold sensitivity scores for patients in the nonbonded group (P > .05).

Twelve-month evaluation. Results at the 12-month evaluation were similar to those at the three-month evaluation. The mean VAS score was 25.6 (± 33.8) for patients in the non-bonded group and 13.9 (± 23.6) for patients in the bonded group. The postoperative cold sensitivity response remained significantly lower than the preoperative cold sensitivity response in patients in the bonded group, while the preoperative and postoperative cold sensitivity responses were not significantly different in patients in the nonbonded group.

In addition to assessing chewing pain and cold sensitivity, we noted some other interesting observations. The majority of the molars with incomplete fractures (30 [75 percent] of 40) were first molars. More mandibular molars were cracked (n = 24 [60 percent]) than maxillary molars (n = 16 [40 percent]). Of particular note was the fact that most of the teeth with incomplete fractures had received minimal restorative treatment before the preoperative examination. At the baseline assessment, 31 teeth (78 percent) were noted to have received a one-surface restoration, a small-to-medium–sized two-surface restoration (less than half the intercuspal width) or no restorative treatment at all. Table 2 provides a more detailed description of these findings.

	DISCUSSION

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The consequences of incomplete tooth fracture can range from mild aggravation to complete loss of the fractured tooth. In our experience, patients demonstrating symptoms of pain on chewing caused by incomplete tooth fracture often avoid chewing on the side of the arch in which the offending tooth is located. We also have noted that the cold sensitivity and chewing pain associated with incomplete tooth fracture persist until one of the following develops:

– the tooth is restored with a splinting type of restoration;

– endodontic therapy is performed because of pulpalgia;

– the cracked portion fractures completely away from the tooth;

– the fracture progresses through the root of the tooth.

Oblique progression of the fracture may result in the loss of a portion of the tooth; however, vertical progression of the fracture down the root generally causes irreversible damage, requiring extraction of the tooth. Given these potential sequelae, the detection and restoration of teeth with incomplete fractures is of serious clinical significance. A cuspal-coverage amalgam restoration may be placed as a definitive treatment or as an interim restoration designed to protect the cracked tooth until a cast restoration can be completed.

Our findings indicate that chewing-related discomfort can be relieved by placing cusp-protective splinting amalgam restorations that are either adhesively bonded or retained with conventional mechanical retention. The amount of tooth reduction required for adhesively retained amalgam restorations is significantly less than that needed for either threaded-pin–retained or amalgapin-retained amalgam restorations.

Tooth preparation. The use of threaded pins requires the removal of 4 mm of occlusal tooth structure (2 mm to allow space for the pins and 2 mm for bulk of amalgam occlusal to the pins for structural strength) plus 2 mm for the pin channel.¹⁶ Tooth preparation for restorations retained with amalgapins is much more conservative than that needed for restorations retained with threaded pins. Two millimeters of tooth reduction is required to allow for a 2-mm bulk of amalgam (needed for structural strength) and an additional 1 to 1.5 mm is needed for each amalgapin channel. Although more conservative than a threaded-pin–style tooth preparation, the amalgapin-type preparation requires more tooth reduction in a pulpal direction than that required for an adhesively retained amalgam restoration.

Given the preliminary results of this study, a logical approach could be to combine amalgapin-type resistance features with the use of adhesives, eliminate the use of vertically placed threaded pins altogether and eliminate amalgapin channel preparation in areas approximating the pulp. If long-term symptom relief and restoration retention prove to be the same for bonded and non-bonded restorative approaches, adhesives should become an integral aspect of the treatment for cracked teeth and may replace conventional resistance features completely.

We were mildly surprised to find 100 percent relief from chewing discomfort in both treatment groups as early as the two-week evaluation. Likewise, we were somewhat surprised at the absence of significant postoperative pulpal discomfort after both the two-week and three-month intervals. No patients reported spontaneous discomfort after the restoration was placed. These findings may have been related to the screening process used to select patients for the study. We excluded patients with teeth demonstrating extreme pulpal sensitivity (teeth were excluded if they exhibited spontaneous pain or sensitivity to cold lingering more than 45 seconds). This could have had the effect of excluding teeth with incomplete fractures too extensive to be splinted with bonded or pin-retained amalgam restorations.

The amount of tooth reduction required for adhesively retained amalgam restorations is significantly less than that needed for either threaded-pin–retained or amalgapin-retained amalgam restorations.

The choice of 45 seconds as the threshold for exclusion for lingering discomfort was somewhat arbitrary. We previously restored several teeth with cold-related sensitivity lasting for as long as 30 seconds as part of a pilot investigation, and found symptom resolution to be predictable. Based on this finding, we included five teeth that had preoperative cold sensitivity that lingered for 30 to 45 seconds (three in the bonded group and two in the nonbonded group). Chewing sensitivity was eliminated for all five teeth, and sensitivity to cold was reduced to a similar degree as that of the other teeth in the study.

VAS scores. Whenever a standardized test is used to measure pain, one must question the clinical meaning of the results. Todd and colleagues²⁵ conducted a study in which they found that patients correlated changes of 13 mm on a 100-mm VAS with a consciously detectable change in discomfort. At the two-week point in our study, six patients in the nonbonded group and four patients in the bonded group reported sensitivity increases of 13 mm or more. By the three-month evaluation, only four patients in the nonbonded group and none of the patients in the bonded group reported sensitivity ratings that were more than 13 mm greater than their baseline scores.

At the two-week evaluation, seven patients in the bonded group and six patients in the nonbonded group reported sensitivity decreases of more than 13 mm. At three months, 11 patients in the bonded group and 10 patients in the non-bonded group reported sensitivity decreases of 13 mm or more. Although analysis with Fisher’s Exact Test indicated no significant difference between the groups (P > .05), it is noteworthy that after three months, cold sensitivity had diminished by a clinically detectable degree in 21 (57 percent) of 37 patients. Coupled with the fact that 37 (97 percent) of 38 patients experienced complete relief of chewing sensitivity, this finding illustrates the efficacy of placing cusp-protective, splinting-type amalgam restorations in teeth with incomplete fractures.

Our findings are in agreement with those of previous investigators who reported that the most commonly fractured teeth were mandibular molars.^1–3 Of the 40 molars with incomplete fractures included in this study, 24 (60 percent) were mandibular molars. We found that incomplete fracture occurred most commonly in first molars. Thirty-three cracked teeth (82.5 percent) were first molars, five teeth (12.5 percent) were second molars and two teeth (5 percent) were third molars. Our communication with clinicians in our dental facility revealed that during the several-month period of patient recruitment for this study, no patients sought treatment for incomplete tooth fracture in nonmolar teeth. Although incomplete tooth fracture certainly can develop in non-molar teeth, these informal results indicate that it is an unusual occurrence.

At the outset of this study, 31 (77.5 percent) of 40 teeth were either unrestored or had been restored with only an occlusal restoration or a small-to-medium–sized two-surface restoration. This finding is in agreement with that of Hiatt,¹ who reported that 74 percent of teeth with incomplete fractures had been minimally restored. This leads us to believe that excessive occlusal stresses, rather than weakening of teeth through extensive restorative treatment, are the primary etiologic factors in incomplete tooth fracture. We speculate that teeth that are weakened because of restorative treatment are likely to experience complete cuspal fracture rather than incomplete fracture. Although the following finding is not directly related to the findings of this study, we believe that patients who are diagnosed as having incomplete tooth fracture, or who otherwise demonstrate evidence of excessive occlusal forces, are candidates for protective acrylic occlusal splints made for nighttime wear.

We considered omitting the use of a resin sealer beneath the nonbonded restorations; however, we felt ethically compelled to seal the dentin in the vicinity of the crack to the best of our abilities to preclude the ingress of exogenous fluids. Because the teeth in both the bonded and nonbonded groups received a layer of resin between the amalgam and the dentin, the difference in cold sensitivity detected at three months must be attributed to something other than the presence of the resin in the bonded group. A logical explanation for this finding is that the additional dentin removed from the nonbonded restorations may have made a difference in the pulpal response to cold.

A spherical amalgam was used for the first layer because several laboratory studies have shown that spherical amalgams bond better to dentin than do admixed amalgams. We needed more operating time than most spherical amalgams offer to develop the appropriate occlusion in the new restorations. Thus, the slow-setting admix amalgam (Original D, Wykle Research Inc.) was packed over the first increment of the spherical amalgam (Tytin). One of us (J.O.) has participated in two laboratory studies that have shown no problems with using two types of amalgam in the same restoration.²⁶

	CONCLUSIONS

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In this study, we found that both bonded and nonbonded complex amalgam restorations were effective in eliminating chewing pain in molars with incomplete fractures. Compared with baseline cold sensitivity measurements, neither bonded nor non-bonded complex amalgam restorations significantly reduced cold sensitivity at the two-week postoperative evaluation. At both the three-month and 12-month postoperative evaluations, cold sensitivity was significantly reduced (compared with preoperative levels) in bonded amalgam restorations, while a significant reduction in cold sensitivity was not found in nonbonded restorations. Teeth that were either intact or minimally restored were most often diagnosed as having incomplete fracture.

The results of this investigation suggest that bonded complex amalgam restorations may be preferred over mechanically retained complex amalgam restorations for molars with incomplete fractures. However, long-term follow-up studies are needed to determine whether bonded complex amalgam restorations will provide the longevity that is achieved with mechanically retained restorations.