reported that, in terms of cleaning, 1 min of PUI/ UAI per canal was equivalent to 3 min per canal for canal cleanliness, but that 3 min provided cleaner isthmuses when utilizing a continual ßushing system. Further research into the effect of time is needed when more standard PUI/UAI techniques are developed. The size of the endodontic access opening may also play a factor in the ability of the irrigant to reach the canal. However, no research has looked at this.

Studies looking at the use of PUI/UAI to remove either calcium hydroxide or other paste Þllers from root canals have given mixed results. Complete removal of a medicament is necessary since there is a potential to prevent sealing of the canal due to interference with the Þlling material by the remaining paste [47, 77, 102]. The addition of PUI/UAI to remove calcium hydroxide and Ledermix was found to improve overall removal, but did not assure complete removal of all material [131]. Wisemann et al. [169] reported similar results. Capar et al. [37] reported that PUI/UAI removed signiÞcantly more calcium hydroxide from artiÞcial grooves in the apical third of the root canal as compared to needle irrigation. Complete removal of the paste was not achieved.

The impact of canal curvature on the effectiveness of PUI/UAI has also been reported. SigniÞcantly improved cleaning of canals and isthmuses occurred at the apical 5 mm in curved canals versus needle irrigation [69, 82, 112, 135]. Malki et al. [100] report that the ßow of irrigant beyond the ultrasonic Þle tip was not affected by curvature of the canal. Ahmad et al. [5] and Lumley et al. [96] reported improved efÞcacy when pre-bent Þles were utilized for PUI/ UAI. Amato et al. [10] reported better cleaning of artiÞcially made lateral canals in teeth with PUI/ UAI in both straight and curved canals as compared to needle irrigation. However, better cleaning was observed in the straight canals. This could be due to the fact that the ultrasonic Þle was placed within 1 mm of the apex and contacted the inner wall of the canal at the curvature and the outer wall near the apex therefore leading to diminished or restricted ultrasonic activation of the irrigant. Al-Jadaa et al. [9] reported similar

results when comparing the use of straight, prebent, and NiTi ultrasonic Þles placed within 1 mm of the apex of straight and curved canals. In this study, the use of the NiTi Þle resulted in better debris removal and less transportation versus the straight and precurved stainless steel Þles/ wires.

Bacteria/Biofilm Removal

The removal or reduction in the number of bacteria within the root canal system is one of the primary goals of endodontic therapy. The utilization of ultrasonically activated irrigation to achieve this goal has been researched. A large number of studies have reported a signiÞcant reduction in the number of bacteria (as measured by colony forming units Ð CFUÕs) following the use of PUI/UAI [6, 16, 32, 60, 81, 103, 146, 147, 158] when compared to needle irrigation. Only one study failed to show an improvement in CFU reduction [143].

The above studies concentrated on the reduction of free bacteria (planktonic) and not the removal of bioÞlm. The impact of PUI/UAI on removing bioÞlms has also been evaluated, but to a lesser extent. Bhuva et al. [17] reported no improvement in removal when utilizing an artiÞcially produced bioÞlm of E. faecalis. Shen et al. [140] reported an increase in killing of artiÞcial bioÞlm when PUI/UAI was utilized with chlorhexidine on dentin discs. Case et al. [40] reported similar results when testing ozone Ð PUI/ UAI helped reduce E. faecalis bioÞlm. GrŸndling et al. [71] reported that PUI/UAI helped reduce E. faecalis bioÞlm only when NaOCl was used as an irrigant. Joyce et al. [86] looked at the mechanism of action of ultrasonics on bioÞlm and stated that PUI/UAI caused deagglomeration of the bioÞlm via the cavitation effect.

Safety

The potential risk of extrusion of debris and irrigant during the use of PUI/UAI has been evaluated. Malki et al. [100] reported that ßuid movement and cleaning extends 3 mm beyond

the ultrasonic Þle tip. Munoz et al. [116] reported that the use of PUI/UAI does transport irrigant solution to the apex of the root canal. Vera et al. [164, 165] stated that maintaining apical patency is important to allow irrigant to reach the canal apex during PUI/UAI. Tambe et al. [150] and Mitchel et al. [113] both reported more extrusion of irrigant and debris out the apex of the root canal following the use of PUI/UAI as compared to needle irrigation. Tasdemir et al. [153], however, reported less apical extrusion of irrigant versus needle irrigation. Malentacca et al. [99] reported no extrusion of irrigant out the root apex when the PUI/UAI Þle was kept at 3 and 5 mm from the apex. However extrusion did occur when the Þle was placed within 1 mm of the apex. No reports have been made of sodium hypochlorite accidents occurring during the use of PUI/UAI in the literature.

Continuous Ultrasonic

Irrigation (CUI)

As PUI/UAI was reported to improve the cleanliness of root canals and canal isthmuses, the issue of time for the technique and irrigant replenishment became an issue. In vivo studies by Haidet et al. [74] and Archer et al. [12] on mandibular molars utilized 3 min cleaning cycles per canal. This did not include any time utilized to replenish irrigants in the canals and the problems reported with continuous ßushing. This 3 min technique could add almost 15 min of treatment time to a mandibular molar. Another problem that was previously noted was the potential for straightening of curved canals and Þle breakage. These issues lead to the development of an ultrasonically activated irrigating needle which could simultaneously activate and replenish irrigant deep within the canals. This system was designated continuous ultrasonic irrigation (CUI).

Gutarts et al. [73] published the Þrst study using this customized ultrasonic tip (Fig. 10.10). Their in vivo results indicated cleaner canals and canal isthmuses within 3 mm of the canal apex, in vital mandibular molar mesial roots, and irrigating times of 1 min per canal with 5.25 % NaOCl.

Fig. 10.10 CUI system used by Gutarts et al. [73], Carver et al. [39], Burleson et al. [28]

Placement of the needle was no deeper within the prepared canals (size 30/.04) than 1Ð2 mm short of binding of the needle. A 25-gauge needle was utilized and 15 ml of irrigant was delivered over the 1 min of continuous ultrasonic activation. This study was followed by Carver et al. [39] who looked at the in vivo removal of planktonic bacteria using the same treatment technique and CUI in necrotic mandibular molars. This group reported a signiÞcant increase in negative cultures and reduction of CFUÕs compared to canal preparation alone with needle irrigation (NaOCl).

Burleson et al. [28] utilized the same device/ technique to look at in vivo bioÞlm removal. Using necrotic mandibular molars, this group prepared and cleaned the mesial root canals similar to Gutarts et al. [73] and extracted, stained, and sectioned the roots from the apical 1Ð3 mm. They reported signiÞcantly cleaner canals and isthmuses following the use of CUI as compared to needle irrigation (Fig. 10.11).

Currently there are two products commercially available for clinical use to provide CUI: Dentsply Tulsa Dental Specialties ProUltra¨ Piezoßowª Ultrasonic tip (Fig. 10.12) and Vista Dental Products StreamCleanª Flo-thru tip (Fig. 10.13). The Piezoßow tip is a 25-gauge, blunt-ended stainless steel needle, while the StreamCleanª tip is a 30-gauge blunt-ended NiTi tube with external serrations.

Research utilizing the commercial tips has been rather limited and has looked at the efÞcacy

Fig. 10.11 Photomicrograph of cross section at the 2.0 mm level Ð (a) Needle irrigation group (magniÞcation: 100 ×). (b) CUI group (magniÞcation: 40 ×) (Burleson MasterÕs thesis, 2006)

Fig. 10.12 Dentsply Tulsa Dental Specialties ProUltra¨ Piezoßowª Ultrasonic tip (Dentsply Tulsa Dental)

B

Fig. 10.13 Vista Dental StreamCleanª Flo-thru tip (Vista)

and safety of CUI. YŸcel et al. [173] reported that CUI with the Piezoßowª tip removed calcium hydroxide better than needle irrigation. Yoo et al. [172] reported that CUI with the StreamCleanª tip cleaned canals and isthmuses better than needle irrigation in extracted mandibular molars. Curtis and Sedgley [51] also reported cleaner canals at the 1Ð3 mm level from the apex using the StreamCleanª tip compared to needle irrigation. Castelo-Baz et al. [41] reported that CUI with the Piezoßowª tip was more effective than PUI/UAI in getting irrigant into lateral canals. Malentacca et al. [99] reported that CUI with the Piezoßowª tip removed pulp tissue signiÞcantly better than needle irrigation and PUI/ UAI. However, Howard et al. [78] reported no

differences in debris removal with the Piezoßowª tip over needle irrigation.

In terms of safety, i.e., extrusion of debris irrigant past the canal apex, Malentacca et al. [99] reported that the use of the Piezoßowª tip resulted in signiÞcant irrigant extrusion beyond the apex when placed within 5 mm of the apex. Placement beyond this length does not follow the manufacturerÕs recommendations. Utilizing this same system but attaching suction to the ultrasonic tip and placing irrigant in the pulp chamber (similar to the EndoVac system by SybronEndo) proved to be extremely safe [99]. Desai and Himel [61] reported that the use of CUI (using the Burleson et al. set-up) extruded more irrigant out the root apex than needle irrigation. Pafford

[118] reported, in a clinical study using the prototype Piezoßowª tip, little or no intraor postoperative treatment pain during and following the use of CUI in vital and necrotic posterior teeth. No sodium hypochlorite accidents have been reported in the literature during the use of a CUI system.

Debate has developed if ultrasonic activation actually is capable of cleaning the apical portions of the root canal due to a phenomenon known as vapor lock. Vapor lock is reported to occur due to the root end being enclosed by the boney socket which results in gas entrapment at its closed end during irrigation. It was Þrst reported in the engineering literature by Dovgyallo et al. [63]. De Gregorio et al. [55] and Tay et al. [155] reported that this effect occurred in the root canal and therefore apical cleaning was impossible (Fig. 10.14). This phenomenon may be a factor that can be controlled in the lab by either sealing the apex of an extracted tooth or by maintaining patency. However, clinically, the debate over an open versus closed system remains. Salzgeber and Brilliant [137] reported that radiopaque dye infused irrigant extruded out the apex of vital and necrotic teeth during hand Þling preparation. Vera et al. [164] explained that irrigant can reach the apex of a root (in vivo) when apical patency is

maintained with a size 10 Þle during NiTi rotary preparation of canals with or without the utilization of PUI/UAI. Since there are multiple unfortunate reports of NaOCl accidents in the literature, one may presume that the in vivo status of the root canal system is open unless it becomes blocked with dentin or tissue debris and patency is not maintained. Boutsioukis et al. [24] reported that vapor lock can be removed by increasing the depth of needle penetration, increasing apical preparation size, using an open-ended needle and temporarily increasing ßuid ßow rate of the irrigant within the root canal.

Laser-Activated Irrigation (LAI)

Activation or agitation of root canal irrigants via the use of lasers is a relatively new concept in endodontics. Previous work with laser has focused on direct canal cleaning and shaping (similar to ultrasonics), disinfection, and smear layer removal. However, issues have arisen in terms of potential damage to the root canal wall dentin, overheating of the root and periodontium, access around the canal curvatures, and the size of the laser tip.

Blanken and Verdaasdonk [19] Þrst reported the effects of using an Er,Cr:YSGG (erbium- chromium-yttrium-scandium-garnett) laser on irrigating ßuids. They stated that there was immediate ßuid movement after each laser pulse and they visualized cavitation (expansion and implosion of gas bubbles) effects. This work was conÞrmed by Blanken et al. [18], De Moor et al. [57], and Matsumoto et al. [110], who utilized an Er:YAG laser. Matsumoto et al. [110] detailed the cavitational effects by stating that the ßuid in the canal (water in their study) instantly vaporized (1 μs) next to the laser tip. The vaporized water expanded forming a void (bubble) as the irradiation continued and heated more water on the inner surface of the void. They reported that this expansion occurred for 700 μs. When the laser pulse ceased, the bubble began to shrink, but the pressure of the surrounding ßuid caused a violent collapse resulting in acoustic waves which traveled through the ßuid-acoustic streaming (Fig. 10.15). It is these waves (as previously discussed) which result in cleaning of the canal by shearing debris off the walls (Fig. 10.16). Therefore, the cleaning effect of LAI is very similar to that of PUI/UAI and CUI and hence the term laser-activated irrigation. Another term seen in the literature for a similar process is photoninduced photoacoustic streaming (PIPS). The difference in this technique over the LAI techniques is that the laser tip is not placed within the root canal but only placed at the canal oriÞce [62].

Numerous studies have looked at the cleaning/ disinfecting potential of LAI. In terms of bacte-

ria/bioÞlm removal, most studies utilizing LAI have shown an improvement in the removal of artiÞcially placed bioÞlms of E. faecalis. Ordinola-Zapata et al. [117] reported improved bioÞlm removal from dentin discs viewed under SEM when compared to PUI/UAI and sonic agitation. Zhu et al. [174] and Sahar-Helft et al. [136] reported the addition of LAI that improved the effects of irrigating solutions (EDTA, NaOCl, chlorhexidine) to remove E. faecalis bioÞlm. However, Zhu et al. [174] found no improvement with LAI (versus needle irrigation) in terms of reducing CFUs. Yavari et al. [171] also reported better results with needle irrigation versus the use of LAI. Seet et al. [139] found that LAI was better at removing E. faecalis from dentinal tubules compared to sonic agitation. Peters et al. [127] reported increased disinfection with the use of LAI compared to PUI/UAI, but not complete removal of the bioÞlm or bacteria.

Debris/material removal from root canals has also beneÞtted from the use of LAI. Kaptan et al. [88] reported an improvement in calcium hydroxide paste removal following the use of Er:YAG LAI, but the difference in cleaning compared to needle irrigation was not signiÞcant. Calcium hydroxide remained in the canals. Deleu et al. [59] reported that the use of Er:YAG laser with a plain tip was the best method to remove dentin debris from artiÞcially prepared canal grooves. De Groot et al. [56] reported LAI with an Er:YAG laser was superior to PUI/UAI in a similar model. Arslan et al. [13] also reported superior debris removal utilizing Er:YAG LAI for 1 min in the