Wednesday, October 30, 2013

Long-term Photographic and Radiographic Assessment of Bonded Resin Composite Strip Crowns for Primary Incisors: Results After 3 Years

Long-term Photographic and Radiographic Assessment of Bonded Resin Composite Strip Crowns for Primary Incisors: Results After 3 Years
Author: Kupietzky, Ari
Pediatric Dentistry 2005
Resident: Margaret Cannon
The aim of this study was to examine the photographic and radiographic success of the treatment of maxillary anterior primary incisors with composite resin strip crowns placed in a private-practice setting after a minimum of 18 months.

Methods: 145 restorations, placed in 52 children, were evaluated by two independent pediatric dentist. Radiographs and photographs were used to evaluate the results. The average time of evaluation was 31.3 months after initial placement of the resin crown. 

Results: None of the restorations were totally lost.  20% of the restoration showed some form of lost resin material, resulting in an overall 80% retention rate. 92% of teeth indicated healthy pulps, 6% had signs of change but did not require immediate attention. Some of these changes included premature resorption, calcific metamorphosis and internal resorption. Only 2 teeth showed signs of radiographic evidence of pulpal pathology that required immediate treatment.

Strip crowns are an excellent choice for teeth that present with multi-surface caries. The long term prognosis has a high degree of predictability and esthetics are unparalleled by other similar restorations. With these results, clinicians should be more apt to choose strip crowns over some of the other more expensive and less esthetic options.

Assessment: I thought this article provided good evidence for restorations that we commonly use, and more info for choosing between ext or restoring anterior teeth in patients that need strip crowns to last several years.

Parental Satisfaction With Bonded Resin Composite Strip Crowns for Primary Incisors

Resident: Mackenzie Craik
Article: Parental Satisfaction With Bonded Resin Composite Strip Crowns for Primary Incisors.

Author: Kupietzky and Waggoner

Publication: Pediatric Dentistry, Volume 26, Number 4, July/August 2004, pp. 337-40(4).

Purpose: The purpose of this study was to evaluate the parental satisfaction of bonded
resin composite strip crowns for the treatment of maxillary anterior primary incisors and
compare their satisfaction with the clinical evaluation and success of the crowns.

Methods: This was a retrospective, clinical study of patients who had strip crowns
placed on maxillary primary incisors, returned for at least 1 recall examination. Color photographs were used for evaluation by 2 independent pediatric dentists. Parental satisfaction regarding the esthetics of the crowns was evaluated by a questionnaire.

Key Points:
-One hundred and twelve restorations placed in 40 children were evaluated.
-The evaluations were performed after the crowns had been in place for an average of 18 months.
-Overall parental satisfaction with the treatment was excellent, however, satisfaction with regard to color received the lowest rating.
-No significant differences were found between dentist and parent evaluations of color, size, and overall appearance.
-Parents rated their overall satisfaction as being positive regardless of their poor ratings of color, size, or overall appearance.
-A significant relationship was found between durability and overall satisfaction.
-Parents who gave poor ratings to durability also rated their overall satisfaction as being poor.

Assessment: I felt this to be a very informative article, and was interested to see that parents overall satisfaction/dissatisfaction was based more on durability than it was on esthetics. I also found it to be inconsistent that the pediatric dentists were evaluating pictures of the teeth, and parents were actually inspecting them in real life. To make the results more consistent it seems you would have both groups evaluate the results in the same way.

Tuesday, October 29, 2013

Effect of Adhesive Restorations Over Incomplete Dentin Caries Removal: 5-year Follow-up Study in Primary Teeth

Resident: Todd Bushman

Article:  Effect of Adhesive Restorations Over Incomplete Dentin Caries Removal: 5-year Follow-up Study in Primary Teeth

Authors: Casagrande L, Falster CA, Di Hipolito V, De Goes MF, Straffon LH, Nor JE, Borba de Araujo F

Journal of Dentistry for Children 2009

To evaluate the effect of the materials used for indirect pulp treatment on the long-term outcome of primary molars

Background Information:
-Evidence of IPT's success can be observed by the deposition of a tertiary dentin matrix (increased distance between the lesion and the pulp chamber) in radiographs.
-Complete removal of all carious tissue from the lateral walls of the cavity preparation is traditionally required to improve the marginal seal and adequately control microleakage. Carious dentin can be arrested if the restoration's margins remain sealed.
-Main cause of IPT failure can be related to marginal defects of the restoration associated with the maintenance of high caries activity by the patient.
-Narrow gaps, crevices, ditches, and "microleakage" do not lead to secondary caries, but wide voids may vary.

-LA, RDI, Class I prep, most surperficial, infected, and necrotic dentin was removed at sites of pulp exposure risk, then cavity was rinsed with saline
-Experimental group (N=25) Scotchbond Multipurpose Adhesive system
-Control group (N=23) Dycal CaOH
-Z-100 restoration

-25 teeth were available for the final eval (2-5 year follow-up)
-14/15 from experimental group and 8/10 from control group were considered clinically and radiographically successful
-4-to5- year clinical outcome was independent of material use on demineralized dentin

Assessment of Article:  
I think that it is important for us especially in pediatrics.  We don''t always have the most cooperative patients and getting all the decay out before finishing the restoration sometimes isn't possible.  

Veneer Retention of Pre-veneered Primary Stainless Steel Crowns After Crimping

Resident: Jeff Higbee
Article: Veneer Retention of Pre-veneered Primary Stainless Steel Crowns After Crimping
Journal: Journal of Dentistry for Children-75:1, 2008
Authors: Monica Gupta, DMD, MS, et al

Purpose: to determine if crimping the lingual aspect of commercially available, pre-veneered, anterior stainless steel primary crowns affects the fracture resistance of the veneer facings.

- Twenty-six anterior NuSmile crowns were divided into 2 groups
- Group 1 served as the control, and group 2 was manually crimped evenly on the lingual cervical portion.
- All crowns were cemented onto a screw-mounted resin core duplicated from a manually prepared Kilgore tooth and tested under compression.
- Fracture resistance, percent of veneer facing loss, and fracture to the gingival margin were all recorded.
- Differences between the control and experimental groups were analyzed by independent t test and chi-square (alpha=0.05).

- The mean shear force required to fracture the veneers of the non-crimped crowns was 510.11 N and 511.02 N for the crimped crowns.
- The mean percentage of veneer facing removed in the non-crimped crowns was 33%, and 43% in the crimped crowns.
- No significant difference in shear strengths (P=.970) and in percentage of veneer loss (P=.063) was shown between crimped and non-crimped crowns.
- A mean of 8% of the non-crimped crowns and 23% of the crimped crowns had veneers fracturing to the gingival margin.

- The veneer resistance to fracture for the crimped crowns was comparable to non-crimped crowns.
- The crimped crowns, however, were associated with greater veneer surface area loss.

Even though we don’t use pre-veneered crowns frequently in our clinic, it is important to be familiar with them as we may use them more often in private practice.  This article shows that there is an association between crimping and veneer surface loss.  These crowns should be placed without crimping (or as specified in the manufactures instructions)  if possible to maintain the integrity of the veneered surface.

Compomers as Class II Restorations in Primary Molars

Resident: Hofelich
Author: Casamassimo, Griffen, Gross
Journal: Pediatric Dentistry 23:1
Year: 2001

Purpose:  The purpose of the present study was to evaluate the clinical performance of two componers, Hytac and Dyract, and to compare these results to those reported for other intracoronal restorative materials.  For restoration of permanent teeth, composites offer advantages over compomers and glass ionomers in wear resistance and esthetic stability. However, requirements may differ for primary teeth. Primary teeth have a limited lifespan, and the enamel of primary teeth is less wear resistant than permanent teeth. In addition, caries rates are likely to be high in children with proximal lesions so that fluoride release may be helpful. Manufacturer states that separate acid etch step is not required because the bonding agent is acidic enough to etch dentin and produces acceptable bond strengths, therefore eliminating an addition step that may be beneficial when working with children. 

Materials and Methods:
Dyrac (Dentsply)
Hytac (ESPE)

49 healthy children between 5 and 8 years old with 2 primary molars that need class II restorations 
radiographic evidence of caries into the inner half of enamel but not the inner half of dentin
proximal contact with adjacent healthy or restored teeth
occlusal contact with opposing healthy or restored teeth
no indication for pulp therapy or other restorative treatment 
a predicted survival until exfoliation of at least two years

2 operators placed restorations according to guidelines - 1 restoration Dyrac and 1 restoration Hytac
6 subjects received only 1 compomer restoration due to pulp exposure

Evaluated on 4 parameters:
margin adaptation
margin discoloration


 At 2 years - 58 restorations (63%) were evaluated , 8 (12%) were lost to natural exfoliation, and the rest did not return for follow up

The overall failure rate was 10.3%.  
   1- insufficient fill
   1- bulk fracture at the proximal box
   4- recurrent caries

No significant difference between the 2 brands

 Evaluation after 24 months shows Hytac and Dyract to have performed well and comparably as class II restorations in primary teeth. The low failure rate, even in a population with a high caries increment, suggests that compomers are a suitable alternative to amalgam or other, tooth-colored materials when used as class II restorations in primary molars.

I don't have any experience with compomers so it would be interesting to be able to work with the materials.

Pinkham Chapter 39: Aesthetic Restorative Dentistry for the Adolescent

K. Vargas, et al.

Resident: Anna Abrahamian

Fundamentals of Materials Selection
- Clinical success of composite restorations depends on adhesive systems that provide durable bonding of composite to dentin and enamel.
- Three types of composite resins can be used; amount of filler determines type  1) Microfilled – filler particles average 0.04 microns, 2) Hybrid – a blend of different particle sizes is used (0.04 and 0.2 to 3 microns), 3) Nanofilled – nanoparticles and clusters as fillers.
- Mechanical and physical properties of hybrid resin composites are superior to those of microfilled resins (because contain higher proportion of filler particles), but microfilled resins can be polished to an enamel-like luster.  
- Better to use microfilled in the esthetic zone where occlusal forces are not as heavy; when esthetics are important but restorations must also take a higher load, can use a hybrid material as a substrate then veneer with a microfilled composite resin.

Fundamentals of Clinical Technique
- Shade selection is always the first step. Shade should be matched to a tooth that is not yet dehydrated, so match before rubber dam is placed.
- Can polymerize a small piece of the composite on the tooth and then remove it once shade has been evaluated. Use moistened shade guides and allow the patient to pick between two similar shades.
- Etch for 15 seconds and rinse for 5-10 seconds, use the appropriate dentin-enamel bonding agent, and build composite in layers no thicker than 2.0mm.
- Opaque and translucent materials should be used accordingly to replicate the look of dentin and enamel. 
- Carbide finishing burs, ultrafine diamonds, and finishing disks should be used for contouring and finishing.

Fundamentals of Tooth Color and Form
- In many cases, use of a hybrid composite as a foundation under a microfilled composite improves both the strength and the appearance of the restoration.
- Embrasure spaces should be symmetric whenever possible, and contours should match those of the adjacent teeth.  
- Adolescent anteriors should show little sign of wear and display prominent incisal embrasure spaces with rounded incisal point angles.

Restorations for Fractured Anterior Teeth
- If pulp is involved in tooth fracture then tooth may require pulpotomy or pulpectomy.
- In the past, some clinicians considered restoring the tooth with a large class IV restoration   
  an interim restoration, however the strength and color stability of newer materials and
  techniques have changed this.
- Acid etch techniques have lessened the requirements for excessiveretentive features.
- The primary retentive feature is a beveled enamel cavosurface margin of a minimum of    
  1.0 to 2.0 mm in length.  

Restoration of Diastemas
- Composite resin diastema closures are a viable option and can last between 5 and 10
- Orthodontic treatment may be required prior to some diastema closures if gap is too
  wide; best to allow a few months between end of orthodontic treatment and diastema
  closure with restorative material so that the anterior teeth will be more stable and settle
   into their final position.
-  In some patients partial diastema closure is the ultimate treatment due to the width of    
   the diastema and considering the fact that making the teeth too wide can produce an   
   esthetic appearance that is just as displeasing to the patient.

Restoration of Discolored Teeth
Treatment of Hypoplastic Spots
- Can be improved with microabrasion.
- Microabrasion requires little enamel removal and does not necessitate the placement of a
- The technique for enamel microabrasion involves application of an acidic abrasive paste
   by a reduced-speed dental handpiece.
- Microabrasion is sometimes combined with vital bleaching.

Lab constructed veneers: When moderate to severe staining exists.  Can be constructed from either porcelain or composite.  Requires the removal of 0.3 - 0.5 mm of enamel but occasionally more in severely stained teeth.  For optimum periodontal health the finish line should be kept supragingival.

Direct Veneers:  Constructed directly in the mouth.  Offer improved marginal adaptation.  May be performed with or without any enamel removal.  The composite should be applied 1-1.5 mm thick and contoured using brushes.  Finishing and polishing is best done with burs and disks.

Vital Bleaching
- Includes power bleaching and night guard bleaching. 
- Power bleaching is an in office procedure which includes the use of high concentration
   hydrogen peroxide solution applied to rubber-dam isolated teeth, while heating the teeth
   with an electric lamp; can cause thermal sensitivity.  Usually takes 3-4 office visits. 
- Night guard bleaching uses a milder peroxide solution; takes 2-3 weeks and is as effective  
   as power bleaching with less thermal sensitivity.

Resin-Retained Fixed Prostheses
Cast metal appliances that can be bonded to enamel with composite resins. Teeth must have adequate enamel for bonding because exposed dentin decreases retentive strength.  An alternative treatment useful in some cases: allows for greater conservation of tooth structure and often lower cost.

Effect of Shortening the Etching Time on Bonding to Sound and Caries-affected Dentin of Primary Teeth
Tathiane Larissa Lenzi, DDS, MSc1 • Fausto Medeiros Mendes, DDS, MSc, PhD2 • Rachel de Oliveira Rocha, DDS, MSc, PhD3 • Daniela PrĂ³cida Raggio, DDS, MSc, PhD4

Resident: Avani Khera
Purpose: To evaluate the influence of shortening the etching time of bonding of an acid etch and rinse and a 2 step self etch adhesive system to sound dentin and caries affected primary tooth dentin.

Methods: Flat dentin surfaces from 48 primary molars were assigned to eight groups, according to sound dentin versus caries affected dentin, adhesive, and etching time (recommend by manufacturers and reduced by 50 percent).
Results: Shortening the etching time does not jeopardize the bonding to sound and caries-affected dentin of primary teeth.
Discussion: Primary tooth dentin has greater tubular density and larger diameter than permanent tooth dentin. Since the penetration of acids occurs primarily along the tubules, it could be possible that a large number with large diameter tubules could result in a deeper penetration of the acidic conditioner. Additionally, primary tooth dentin seems to be more reactive to acid etching due to a reduced degree of mineralization. Therefore, it has been suggested that shortening the etching time would yield the formation of a more functional hybrid layer in primary teeth. It has been shown that a linear relationship between etching time and hybrid layers thickness exists. Even after increasing the thickness of hybrid layers, prolonged acid etching times tends to lower bond strengths.

Microleakage of Adhesive and Non-adhesive Luting Cements for Stainless Steel Crowns

Resident: Derek Nobrega
Title: Microleakage of Adhesive and Non-adhesive Luting Cements for Stainless Steel Crowns
Authors: Mahtab Memarpour, DMD, MScD; Maryam Mesbahi, DMD, MScD; Gita Rezvani, DMD, MScD; Mehran Rahimi, DMD, MScD
Journal: Pediatric Dentistry 33 (&): 501-504.

Main Purpose: To compare the ability of 5 luting cements to reduce microleakage at SSC margins on primary molars.  

Methods: One hundred extracted primary molars (28 mandibular 1st molars, 25 mandibular 2nd molars, 26 maxillary 1st molars, and 21 maxillary 2nd molars) with less than 2/3 root resorption were used. The teeth were mounted in acrylic resin blocks and prepared by a single operator. After preparation, the teeth were randomly divided into 5 groups according to the cement used:
1. Polycarboxylate cement – Durelon
2. Zinc Phosphate cement – Elite cement
3. Glass Ionomer cement – Ketac-Cem
4. Resin modified glass ionomer cement – Rely X Luting 2
5. Dentin Bonding Agent + Resin modified glass ionomer cement – Single Bond + Rely X Luting 2
SSCs were placed with each cement according to manufacturer’s instructions, and the teeth were placed in water for 4 weeks. Teeth were immersed in methylene blue due for 24 hours, removed and sectioned facio-lingually across the center of the restoration. The teeth were examined at 40X magnification and dye penetration was measured in millimeters from the margin of the SSC through the interfaces between the tooth and the cement.

Key Points:
1. Microleakage was less with adhesive cements than non-adhesive cements.  
2. Crowns cemented with polycarboxylate cement (Durelon) showed the greatest microleakage.
3. Dentin Bond + Resin modified glass ionomer cement showed the least microleakage.
3. Glass ionomer cements (Ketac-Cem, Rely X Luting 2) led to significantly less microleakage than polycarboxylate cement and zinc phosphate cement.
4. None of the luting cements investigated could seal crown margins completely.

Good, comprehensive in vitro study on cementing SSCs. I wonder if the results translate to the actual conditions in the mouth. These results also show that even in an ideal situation, cements cannot completely seal crown margins. This is important for us to know, as we must ensure proper fit of crowns before cementation to minimize microleakage. We cannot rely on the cement to make up for poor margins on our crowns. 

Wednesday, October 23, 2013

Effectiveness of a Glass Ionomer Cement Used as a Pit and Fissure Sealant in Recently Erupted Permanent first Molars

Resident: Jeff Higbee
Article: Effectiveness of a Glass Ionomer Cement Used as a Pit and Fissure Sealant in
Recently Erupted Permanent first Molars
Journal: Journal of Dentistry for Children
Authors: Fernanda Barja-Fidalgo, et al

Purpose: This study’s purpose was to evaluate the caries-preventive effect of a glass ionomer
cement (GIC) used as an occlusal sealant on recently erupted permanent first molars.
Methods: A double-blind, randomized, controlled, clinical trial was undertaken that included
36 5- to 8-year-olds (and 92 permanent first molars) who were randomly allocated
to the test group (GIC) or the control group (auto-polymerized resin-based sealant [RBS]).
Results: After 6 months, 1 occlusal surface in the test group and 2 occlusal surfaces in the
control group showed carious lesions (P=.15). In the fifth year of follow-up, 2 occlusal
surfaces in the test group and 7 occlusal surfaces in the control group were filled or carious
(P=.42), and the mean number of sealed surfaces that became carious or filled was
0.2 (95% confidence interval [CI]=0.02-0.70) for the GIC-sealed teeth and 0.6 (95%
CI=0.20-1.30) for the RBS-sealed teeth (P=.30).
Conclusion: High-viscosity glass ionomer cement can provide some level of protection
against dental caries when used as a dental sealant in newly erupted permanent first molars.

Preventive Resin Restorations: Practice and Billing Patterns of Pediatric

Resident: Margaret Cannon
Title: Preventive Resin Restorations: Practice and Billing Patterns of Pediatric
Author: Savage et al
Journal: Pediatric Dentistry 2009

Main purpose: To determine the billing patterns of PRRs.
  • Survey sent to 475 dentists randomly selected from the AAPD database
  • 16 questions on demographics, treatment planning, techniques in preparation and restoration, billing, and the need for a code for PRRs
Key Points:
  • 238 surveys responded (50%)
  • 72% perform PRRs
  • 64% believe there should be a code for PRRs
  • 52% believe that NOT having a code will lead to dentists doing more invasive dentistry to comply with billing
  • Pediatric dentists most commonly treatment plan a PRR for caries that does NOT extend into dentin and does NOT require anesthetic for preparation
  • PRRs are most commonly restored with flowable or packable with a sealant combination
Good survey on a procedure that we do every day. I found it interesting that almost 1/4 of pediatric dentists responded that they don't do PRRs, and that packable composite is a common restorative material for a PRR.
I agree with the idea that there should be a code for PRRs. 

The longevity of amalgam versus composite/compomer restorations in posterior primary and permanent teeth. Findings from the New England children’s amalgam trial

Resident: Derek Nobrega
Title: The longevity of amalgam versus composite/compomer restorations in posterior primary and permanent teeth. Findings from the New England children’s amalgam trial.
Authors: Soncini, J. A., et al.
Journal: J Am Dent Assoc (2007) 138(6): 763-772

Background: Limited information is available from randomized clinical trials comparing the longevity of amalgam and resin-based compomers and composite restorations. The authors compared replacement rates of these types of restorations in posterior teeth during the five-year follow-up of the New England Children’s Amalgam Trial (NECAT). The NECAT randomly assigned children aged 6 to 10 years to groups receiving restorations of either amalgam or resin-based compomer/composite material and prospectively followed them for approximately five years.

Main Purpose: To clarify the issue of restoration longevity by using a randomized clinical trial to compare the replacement rates of restorative material in children's posterior teeth.

Materials and Methods:
The authors randomized children aged 6-10 years whol had two or more posterior occlusal carious lesions into groups that received amalgam (n=267) or compomer (primary teeth) or composite (permanent teeth) (n=267). The patients were followed semi-anually. They compared the longeivity of restorations placed on all posterior surfaces using random effects survival analysis.

Key Points
- Restorations were repaired if they had less than ideal marginal adaptation and/or stained margins, and repo\laced if there were new caries, recurrent caries, fracture, or restoration loss.
- In primary teeth, the replacement rate was 5.8% of compomers versus 4.0% of amalgams.
- 3.0% of compomers were replaced due to recurrent caries, and 0.5% of amalgams were replaced due to recurrent caries.
- In permanent teeth, the replacement rate was 14.9% of composites versus 10.8% of amalgams.
- The repair rate was 2.8% of composites versus 0.4% of amalgams.
- The need for replacement increased significantly with the size of the restoration.
- The overall difference in longeivity is not statistically significant, however compomer was replaced significantly more frequently due to recurrent decay, and composite restorations required seven times as many repairs as did amalgam restorations.
- Compomer/Composite restorations on posterior tooth surfaces in children may require more frequent replacement or repair than amalgam restorations.

This was a good study with a high number of patients. This is something to think about when placing restorations, as we have grown accustomed to using only composite. For some larger restorations, we may benefit from placing amalgam. However, patient demand has made most pediatric dentists use composite or “tooth colored fillings” for all restorations. For larger restorations, we could benefit from telling patients and parents that if we place a “white” filling, it may need to be replaced more often than a “silver” one. 

Tuesday, October 22, 2013

Reversal of soft-tissue local anesthesia with phentolamine mesylate in pediatric patients.

Resident: Mackenzie Craik
Article: Reversal of soft-tissue local anesthesia with phentolamine mesylate in pediatric patients.
Author: Mary Tavares DMD, MPH
Journal: JADA, 2008.

. The authors evaluated the safety and efficacy of a formulation
of phentolamine mesylate (PM) as a local anesthesia reversal agent
for pediatric patients.


A total of 152 pediatric subjects received injections of local

anesthetic with 2 percent lidocaine and 1:100,000 epinephrine before

undergoing dental procedures. The authors then randomized subjects to

receive a PM injection or a control injection (sham injection in which a

needle does not penetrate the tissue) in the same sites as the local anesthetic

was administered in a 1:1 cartridge ratio after the procedure was

completed. Over a two- to-four-hour period, they measured the duration of

soft-tissue anesthesia and evaluated vital signs, pain and adverse events.


The median recovery time to normal lip sensation was 60 minutes

for the subjects in the PM group versus 135 minutes for subjects in

the control group. The authors noted no differences in adverse events, pain,

analgesic use or vital signs, and no subjects failed to complete the study.


PM was well-tolerated and safe in children 4 to 11 years

of age, and it accelerated the reversal of soft-tissue local anesthesia after a

dental procedure in children 6 to 11 years of age.

Clinical Implications.

PM can help dental clinicians shorten the posttreatment

duration of soft-tissue anesthesia and can reduce the number of

posttreatment lip and tongue injuries in children.

Monday, October 21, 2013

Fracture Resistance of Human Root Dentin Exposed to Intracanal Calcium Hydroxide

GE Doyon, et al.
Journal of Endodontics, 2005: 31(12) 895-897
Resident: Anna Abrahamian

The purpose of this study was to determine if intracanal exposure of root dentin to calcium hydroxide for 30 days and 180 days had deleterious effects on the fracture resistance of root dentin.
Materials & Methods:
One hundred and two freshly extracted human teeth (max/mand incisors, canines, and premolars) stored in saline were randomly assigned into three groups of 34 teeth each. Each of the teeth were accessed with a round bur, instrumented with a hand K files and rotary ProFiles to 1 mm beyond the apical foramen, sterile saline irrigation throughout. The root canals of group 1 were filled with saline and sealed apically and coronally with bonded resin composite. Group 2 canals were filled with USP Ca(OH)and sealed apically and coronally with bonded resin composite Group 3 teeth were filled with Metapaste and sealed in the same manner as group 1 and 2. The teeth were maintained at room temperature in saline-soaked gauze during the preparatory phase then stored in sterile 0.9% saline solution. After 30 days, half of the teeth in each group (17 teeth from groups 1,2, and 3) were sectioned with a diamond saw. The roots were sectioned horizontally into 4-8 discs (depending on root length), 1mm in width.  Each section was loaded with a universal testing machine (1.2mm punch) at a speed of 2.5mm/min at the midway point of dentin in between the canal and the outside edge of dentin until the specimen fractured. After 180 days, the remaining 17 teeth from each of the groups, 1-3 were removed from saline and tested in the same manner.
There were no statistically significant differences among the fracture resistance for any of the 30 day specimens. However, a decrease in the peak load at fracture of the specimens whose root dentin was exposed to USP Ca(OH)for 180 days was noted to be statistically significant.
Ca(OH)2 has a variety of applications in dentistry: as a pulp capping agent, an intracanal medicament to control inflammation/root resorption after trauma, interim filling material in between appointments for RCT, and in apexification therapy. The long term effects of Ca(OH)2 on human dentin are not well understood, but anecdotal observations exist that show immature teeth treated with Ca(OH)2 show a high failure rate due to a high prevalence of root fracture. The results of this study support the author’s postulate that long term exposure of root dentin to Ca(OH)2 may cause changes in the physical properties of dentin that result in a decrease in it’s strength. The author’s contend that the decrease in strength may be a result of the change in the organic matrix (pH increase may reduce the organic support of the matrix, disrupting the interaction between collage fibrils and hydroxyapatite crystals). The difference in peak load fracture between the 180 day USP Ca(OH)2 group and the other experimental group range from 9.9-19.0% - i.e., it may be that a 10-20% decrease in strength is sufficient to significantly increase the likelihood of fracture to already structurally compromise teeth.
Good article - fairly good sample size. Some problems in design: storage medium of avulsed teeth does not reflect in vivo conditions, need to take into consideration the effects of coronal access and restoration on root fracture.