Post extraction complications

Back to DrTedHomepage   Back to Article RemovingWisdomTeeth  PreventionofDrySocket

FREE  ORTHODONTIC CONSULTATION

Request Appointment Form

Etiology, Prevention and Management of Post Extraction Complications

Continuing Dental Education Course -  4 CEUs

Author Michael Florman, DDS

NYU Post Graduate Orthodontics 2004

This CE course appeared as an insert in Dental Economics, August 2004

 This course is written for Dentists, Dental Hygienists and Dental Assistants

Way back on February 30, 2000 Jane Brody, who writes articles related  to health, wrote one entitled: "When wisdom teeth should be extracted." That article proved to be one of the top five pages that internauts come to read when they land on the www.drted.com web site. It seems to be an excellent complement to Dr. Florman's Article. Here then is the link to that page and 16 links to the websites of Specialists in Oral Surgery.   "When wisdom teeth should be removed".

 Objectives

This continuing education course has been written to discuss the etiology of complications associated with post-operative extractions. Techniques to manage difficulties occurring post-operatively and days after will be discussed. Topic include: causes of difficult extractions, the healing process, high risk patients, management of bleeding hemostatic agents, dry sockets, prevention of dry sockets, and treatment of dry-sockets, Surgical techniques and pain management will not be discussed in this course.

 

Introduction

Difficulties with extractions are unpredictable.  Having a thorough medical history prior to surgery will allow the surgeon to better deal with complications that may arise. Be certain to always follow proper surgical techniques, and know your limitations prior to beginning any extractions. If and when difficulties develop, it is always recommended to explain the situation to the patient.

 

Factors That Increase Extraction Difficulty

In most instances, extraction of non-impacted teeth is routine dental procedure. Extraction difficulty increases when the following conditions exist: strong supporting tissues, difficult root morphology ( divergent, hooked locked, ankylosed, geminated or misshaped) teeth exhibiting hypercementoses, teeth containing weakened coronal surfaces due to large restorations, teeth that have been abraded or exhibit abfractions or deep caries, dedicated or brittle teeth  associated with endodontic treatment, patients experiencing inflammatory disorders associated with alveolar bone including Pagetís disease, patients with radionecrotic bone caused by radiation therapy, and patients with limited opening or trismus.

 

Normal healing process

Immediately after teeth are extracted, blood flowing from the alveolar bone and gingiva begin to clot. The clot functions by preventing debris, food and other irritants from entering the extraction site. It also protects the underlying bone from the bacteria and finally acts as a supporting system in which granulation tissue develops.  Tissue damage provokes the inflammatory reaction, and the vessels of the socket expand. Leucocytes and fibroblasts invade from the surrounding connective tissues until the clot is replaced by granulation tissue. Leucocytes gradually digest the clot, while epithelium begins to proliferate over the surface during the second week post-operatively. This eventually forms a complete protective covering.

 

During this time, there is an increased blood supply to the socket which is associated with the resorption of the dense lamina dura by osteoclasts. Small fragments of bone which have lost their blood supply are encapsulated by osteoclasts and eventually pushed to the surface or resorbed. Approximately one month after an extraction. Coarse woven bone is then laid down by osteoblasts. Trabecular bone then follows, until the normal pattern of the alveolus is restored. Finally compact bone forms of the surface of the alveolus, and remodeling continues as the bone shrinks.

 

Bleeding Challenge

Bleeding challenges sometimes present themselves. Due to the nature of the bodyís hemostatic system, the high vascularization of the head and neck region is both friend and foe to the dental surgeon. Once a tooth is extracted, direct primary wound closure is sometimes impossible. Due to the lack of soft tissue that leaves large openings in the alveolus. Unlike other wounds or surgical openings, there is an inability to apply and sustain direst pressure to the socket of an extracted tooth  Other forces exist to even complicate things further, such as disruptive forces from the tongue, passage of food, and normal speech.  Salivary enzymes also interfere with blood clotting and the processes that follow in the evolution of the clot.

 

Preventing Problems

A thorough medical history should be taken, including question regarding bleeding problems.  Some conditions that may prolong bleeding are: non-alcoholic liver disease (primarily hepatitis) and hypertension. Patients with known bleeding disorders should only be treated by oral and maxillofacial surgeons or dentists that have had extensive training in managing the medically compromised patients.  Techniques to manage bleeding may employ the administration of blood transfusions containing adequate factor replacement which will allow for hemostasis. The health history should include questions that discover bleeding problems associated with minor scrapes and cuts.  Family medical history is also important in order to detect possible genetic diseases that patients are unaware of potentially having. Complete and current medication lists should be documented and checked against references that may indicate side effects.  It is also advisable that patients taking extensive medications receive clearance to undergo surgery from their physician.

 

Many drugs interfere with coagulation. There are five groups of drugs known to promote bleeding: aspirin broad- spectrum antibiotics, anticoagulants, alcohol and chemotherapeutic agents. Aspirin and aspirin containing preparations interfere with platelet function and bleeding time. Broad-spectrum antibiotics decrease vitamin K production which is necessary for coagulation factors produced in the liver. Chronic alcohol abuse can lead to liver cirrhosis and decreased production of liver-dependent coagulation factors. Chemotherapeutic agents that interfere with the hematopoietic system can reduce the number of circulating platelets. Patients who are known or suspected to have bleeding disorders should be evaluated and laboratory tested before surgery. Prothrombin time (PT) can be ascertained.

 

Bleeding

Once the tooth is completely remove. The wound should be properly cleaned. It should be inspected for the presence of any specific bleeding arteries or other potential anomalies. If and when arteries exist in the soft tissue, they should be controlled with direct pressure by claming and eventual ligation with resorbable suture. If no arteries exist in the extraction field, complete hemostatic control can usually be maintained for most procedures by using direct pressure over the area of the soft tissue for approximately five minutes.

 

Bleeding from isolated vessels within the bone can occur. Treatment involves crushing the foramen with the closed ends of the hemostat. This will usually occlude the bleeding vessel. Once the foramen is crushed, the socket should be covered with a damp 2x2 inch gauze sponge that ahs been folded to fit directly into the extraction site. The patient should be instructed to bite down firmly on this damp gauze sponge for at least 30 minutes. Do mot dismiss the patient from the office until hemostastis has been achieved, Check the patientís extraction socket approximately fifteen minutes after the completion of the surgery, The patient should open his/her mouth widely, the gauze should be removed, and the area should be inspected  carefully for any persistent bleeding. Replace the gauze with a new piece and repeat again in thirty minutes. If bleeding persists and inspection reveals no arterial bleeding, the surgeon should immediately place a hemostat into the socket.  After placing the hemostatic agent, a gauze sponge should be placed over the top of the socket and is held with pressure.

 

Hemostatic Agents

The most commonly used least expensive hemostatic agent is absorbable gelatin sponge (Gelfoam, Pfizer). Gelfoam sterile compressed sponge is a pliable surgical hemostat prepared for specially treated purified gelatin solution. It is capable of absorbing and holding within its meshes many times its weight in whole blood. It is designed to be inserted in the dry state, and functions wonderfully as a hemostatic agent. Gelfoam forms a scaffold for the formation of a blood clot. Gelfoam has been sued to aid in primary closure for large extraction sites, and is placed into the socket and retained with a suture.  Oxidized regenerated methylcellulose (Surgicel, Johnson and Johnson) is another hemostat used in dental surgery. It binds platelets and chemically precipitates fibrin. It is placed into the socket and sutured. I can not be mixed with thrombin.

 

Topical thrombin (Thrombostat, Pfizer) is derived from bovine thrombin (5,000 units). Thrombin bypasses all steps in the coagulation cascade and helps to convert fibrinogen to fibrin which forms the clot. It is usually saturate into Gelfoam and inserted into the tooth socket when needed.

 

Collagen type products can also be used to help control bleeding, by promoting platelet aggregation and thereby accelerating blood coagulation. Microfibular collagen (Avitene Davol) is a fibular material that is loose and fluffy, but able to be packed. Collaplug/Collatape, (Sulzer Calcitek) are more highly cross-linked collagen and can also be packed. Collagen type products stimulate platelet adherence which helps stabilize the clot, but are much more expensive and usually not used.

 

It is more important to note that when using hemostatic agents, the materials are place in the socket and sutured  to the gingival margin surrounding the extraction site. This will assure that they are secure.

 

Secondary Bleeding

Patients will sometimes return to the office with secondary bleeding, caused in most cases by improper adherence of post-operative instructions. In these cases, the extraction site should be cleared of al blood and saliva suing suction. The dental surgeon should visualize the bleeding site to carefully determine the source of bleeding. If it is determined that the bleeding is generalized, the site should be covered with a folded, damp gauze sponge, and held in place with firm pressure by either the dentist or dental auxiliary for at least 5 minutes. This measure is usually sufficient to control most bleeding. If 5 minutes of this treatment does not control the bleeding, the dental surgeon must administer a local anesthetic so that the socket can be treated more aggressively. Block techniques are encouraged instead of local infiltrations. If infiltration is used and the anesthetic contains epinephrine, temporary vasoconstriction may be achieved and create the impression that the bleeding has stopped permanently. Be cautious.

 

Once anesthesia has been achieved, gently curette the tooth extraction socket and suction all areas of the old blood clot. The specific are of the bleeding should be identified. The same measures described for control of primary bleeding should be followed. The use of Gelfoam (absorbable gelatin sponge) saturated with topical thrombin, then sutured, is an effective way to stop bleeding. Reinforcement should be repeated with the application of firm pressure. In many situations, Gelfoam and gauze sponge pressure is adequate. Before the patient with secondary bleeding to go home, the clinician should monitor the patient for at least 30 minutes to ensure that adequate hemostatic control has been achieved. Be certain to give the patient specific instructions on how to apply gauze packs and pressure directly to the bleeding site should additional bleeding occur.

 

Subcutaneous tissue spaces may become collection areas for bleeding associated with some extractions.  When this occurs, overlying soft tissue areas will appear bruised 2 to 5 days after the surgery. This bruising is called ecchymosis.  Ecchymosis occurs more frequently in elderly patients.  Ecchymosis may extend into the neck and as far as the upper anterior chest. Ecchymosis does not increase the potential for infection or other sequelae. Elderly patients should be warned that there is the potential for ecchymosis.  Reducing trauma is the best way to prevent ecchymosis. Moist heat may be applied to speed up the recovery.

 

Delayed Healing

Normal healing of extraction site are dependent on clot formation and the progression ft that clot to a reorganized matrix preceding the formation of bone. It is uncommon for the blood clot to fail to form except in cases where there is interruption of the local blood supply.

 

It is now thought that the infection is the most common cause delaying wound healing. Signs and symptoms associated with infection can include: fever, swelling and erythema. Careful asepsis and thorough wound  debridement should be performed after surgery.  Irrigate bone copiously with saline to aid in the control of foreign debris. Patients prone to infection should be given postoperative antibiotics to reduce infection blowups.

 

Wound dehiscence should be avoided by following food surgical techniques. Leaving unsupported soft tissue flaps can often lead to  tissue sagging and separation along the incision line, Suturing wound under tension can cause ischemia of flap margins, which may lead to tissue necrosis.

 

Other factors, though rarely seen that can delay healing are:  prolonged bleeding due to clotting defects, formation of an oro-antral fistulas, proliferation of a malignant tumor, radiation therapy, immunosuppresion due to corticosteroid use, dietary deficiencies including but not limited to vitamin C, and overall immune system disorders.

 

DRY SOCKET IDENTIFICATION

 

Dry socket delays the healing of the extraction site and surrounding bone.  Dry socket can be diagnosed by looking for certain symptoms.  Moderate to severe localized pain near the extraction sites developing on or after the third or fourth day post extraction is a sure giveaway.  Patients can state that there is an apparent improvement in discomfort on the second day only to be followed by a sudden worsening of the pain.  The pain is moderate to severe, consisting of a dull aching sensation, usually throbbing which radiate to the ear. Examination will reveal an empty socket, exposed bone surfaces, with a partially or completely lost blood clot.  A bad odor and taste may or may not be present.  Loss of sleep is caused by pain; control of the pain is very difficult even with narcotic analgesics.  Dramatic relief within an hour can be seen after placement of dry socket medicaments. 

 

DRY SOCKET INCIDENCE

 

The incidence of dry socket has been reported in the literature by many investigators, and ranges between .5% - 68.4%, depending on which study is reviewed.  The average is approximately 3% of all extractions.  It has been shown that occurrence of dry socket is between 9-30% in impacted mandibular third molars.  The condition occurs two times as often after single extractions as compared to multiple extractions completed during the same time frame.

 

DRY SOCKET ETIOLOGY AND PREDISPOSING FACTORS

 

Fibrinolysis is the breakdown or failure of normal clot formation due to high levels of fibrinolytic or proteolytic activity in and around the socket.  Fibrinolytic activity results in lysis of the blood clot and subsequent exposure of the bone.

Mandibular teeth are most commonly associated with dry socket.  Sites affected are ranked in order from highest to lowest as follows:  lower molars, upper molars, premolars, canines and incisors.

Studies have demonstrated that the more difficult the extraction, the higher the chance of dry socket.  It has also been demonstrated that less-experienced dental surgeons have a higher incidence of dry socket in lower third molars. The peak age for dry socket is 30-34 years.  Most reported cases occur between the ages of 20 and 40. 

Bacteria, especially anaerobic, have been linked to the formation of dry sockets.  Investigators have found strains of Streptococci, Fusospirochaetal, Treponema denticola, and bacteroides within extraction sites.

Researchers have identified that women have a 20% better chance to develop dry socket than males.  Oral contraceptives are also linked to higher incidence of dry socket along with post extraction trismus and pain.

Patients with uncontrolled diabetes mellitus have a greater incidence of dry socket and should be monitored carefully.

 

PREVENTION OF DRY SOCKET

 

Developing cures and techniques that will prevent dry socket has been a topic of interest in oral surgery for many years.  Well controlled studies indicate that the incidence of dry socket after mandibular third molar surgery can be reduced.

Proper surgical techniques should include thorough debriding and irrigation of the extraction site with copious quantities of saline.  This should be first on your list in controlling the incidence of dry socket.

The incidence of dry socket may be decreased by preoperative and post operative rinsing with antimicrobial mouth rinses, such as chlorhexidine gluconate (Peridex Zila Pharmaceuticals).  A study was performed involving preoperative prophylaxis in conjunction with chlorhexidine gluconate 0.2 percent rinses.  Incidence of dry socket was decreased to some degree.  Use of other medicaments such as Betadine Mouthwash may also be useful in reducing bacterial loads prior to surgery.

Use of topically placed antibiotics administered within the extraction site immediately after completion of the extraction has been the most widely studied modality to reduce dry socket.  Antibiotics such as clindamycin or tetracycline have been successfully used to help decrease the incidence of dry socket in mandibular third molars.

 

Tetracycline

Tetracycline has been studied to determine if it can prevent dry socket when placed directly into the extraction site, immediately following surgery.  One study showed that placement of tetracycline in a suspension with a few drops of saline combined with a square of Gelfoam significantly reduce the incidence of dry socket when used as a dressing after impacted mandibular third molar extractions.  This study supports findings reported by other authors.  Both the tetracycline studies had strikingly similar findings showing an average of 3.8% incidence of dry socket when using tetracycline prophylactically.

Another study looked at neomycin, bacitracin, and tetracycline combined with saline, soaked in Gelfoam, and placed in the extraction socket of third molars.  Results demonstrated that tetracycline was far more effective than either neomycin or bacitracin (combined with Gelfoam) in decreasing dry socket.

 

Clindamycin

 

Effects of a 1x1 cm square of Gelfoam soaked with 1ml of clindamycin phosphate solution (150 milligrams/milliliter) compared to controls using no clindamycin was studied.  Results indicated that out of 172 impacted molar sites, only 7 dry sockets occurred, all of which were control sites that were not exposed to clindamycin.  Clindamycin is especially preferred as the drug of choice in the prevention of dry socket due to its anaerobic properties.

A study of 520 mandibular teeth in 270 patients was performed, in which extractions sites were irrigated with Betadine (Purdue Frederick) prior to placement of clindamycin.  One site received Gel foam soaked in clindamycin, the other received Gelfoam without clindamycin.  Results indicated that there was a significant decrease in dry socket in the sites that received Gelfoam soaked in clindamycin.

These studies demonstrate reduction in dry socket is as low as 3% from 36% when antibiotic medicaments were placed.  There is evidence that bacteria through mechanisms not yet understood play a role in the fibrinolytic phenomenon of dry socket.

 

TREATING OF DRY SOCKET

 

If dry socket (alveolar osteitis) should arise, treatment should be focused on relieving pain.  If the patient does not receive treatment for the relief of pain, the healing process will eventually resolve itself with no difference in time as if treated. Treatment should begin by gently irrigating with saline, and the insertion of medicated dressing.  Do not curette the socket because this will increase the amount of exposed bone and the pain, and remove parts of the blood clot that have not been lysed.  The socket should then be carefully suctioned of all excess saline.  Then, a small piece of gelatin sponge or gauze soaked with the medication should be placed.  This may need to be repeated for 3-6 days depending on the severity of the pain. 

At each visit, the socket will need to be irrigated, and insertion of the medicated dressing repeated.

Medicaments used to treat dry socket may contain a combination of the following ingredients:  bone pain relievers (Eugenol, benzocaine), antimicrobials (idoform), and carrying vehicles (balsam of Peru, Penghawar).

Dry socket pastes and liquids (various manufacturers) can be used and placed directly in the socket alone or using absorbable products such as Gelfoam.

Once place in the extraction socket, the patient will experience profound relief from pain within 5 minutes. Generally, anesthesia is not recommended when placing those products.

 

CONCLUSION

 

This continuing dental education course was designed to review the etiology and treatment modalities associated with complications associated with extractions.  A review of the literature uncovered numerous studies aimed at exploring solutions to post extraction problems.  Further research is still needed, along with education geared toward teaching surgical techniques and therapeutic solutions.

 

Scientific Articles Cited Are Available on Request

 

Continuing Dental Education Questions:

 

1.    Having a thorough medical history prior to surgery will allow the surgeon to better deal with complications that may arise.  Be certain to always follow proper  surgical techniques, and know your limitations prior to beginning any extraction.                        

          a. The first statement is TRUE.  The second statement is     

b.      The first statement is TRUE.  The second statement is FALSE

c.       The first statement is FALSE. The second statement is TRUE

d.      The first statement is FALSE.  The second statement is FALSE

2.    If and when difficulties develop, it is always recommended to explain the situation to the patient

a.    TRUE

b.    FALSE

3.    Extraction difficulty increases when the following conditions exsist except

a.    strong supporting tissue

b.    difficult root morphology

c.     teeth containing weakened coronal surfaces

d.    desiccated teeth

e.    none of the above 

4.    The clot functions by:

a.      preventing debris, food, and other irritants from entering the extraction site

b.      protecting the underlying bone from bacteria

c.       acting as a support system in which granulation tissue develops.

d.      All of the above

5.    The clot is replaced by:

a.      granulation tissue

b.      woven bone

c.       cancellous bone

d.      all of the above

6.    During normal healing, there is an increased blood supply to the socket associated with resorption of the dense lamina dura by:

a.      Leucocytes

b.      Fibroblast

c.       Osteoclasts

d.      Osteoblasts

7.    One of the following is not true regarding small fragments which have lost their blood supply.  Bone fragments:

a.      can be pushed to the surface and expelled

b.      can be encapsulated by osteoclasts

c.       can be suctioned out during curettage

d.      can be converted to vascularized bone

8.    Approximately how long does it take for course woven bone to be layed down by osteoblasts?

a.      One month after an extraction

b.      One week after an extraction

c.       One day after an extraction

d.      Three months after an extraction

9.    Woven bone follows trabecular bone, until the normal pattern of the alveolus is restored.  Finally, compact bone forms over the surface of the alveolus, and remodeling continues as the bone shrinks.

a.      The first statement is TRUE.  The second statement is TRUE.

b.      The first statement is TRUE.  The second statement is FALSE.

c.       The first statement is FALSE.  The second statement is TRUE.

d.      The first statement is FALSE.  The second statement is FALSE.

10.     Once a tooth is extracted, direct primary wound closure is sometimes impossible, and there is usually an inability to apply and sustain direct pressure to the socket of an extracted tooth.

a.    TRUE

b.    FALSE

11.     Which of the following complicate clotting?

a.    Disruptive forces from the tongue

b.    Passage of food

c.     Normal Speech

d.    All of the Above

12.     Which is not a condition that may prolong bleeding?

a.      Hepatitis

b.      Hypertension

c.       Osteoporosis

d.      None of the Above

13.     There are how many groups of drugs are known to promote bleeding?

a.      3

b.      4

c.       2

d.      5

14.Broad-spectrum antibiotics decrease production of what vitamin necessary for coagulation factors to be produced in the liver ?

a. Vitamin A

b. Vitamin D

c.  Vitamin E

d.  Vitamin K

15.  Chronic alcohol abuse can lead to liver cirrhosis and decresed production of?

a. Liver dependant coagulation factors

b. Collagenase

c.  Nitrites

d. All of the above

16.  If no arteries exsist in the extraction field, complete hemostatic control can usually be maintained for most procedures by:

        a.  rinsing with warm water

        b.  finding arteries deep in the bone

c.  using direct pressure over the area of soft tissue for approx.  five minutes

d.  None of the above

17.  This course recommends which of the following treatments when bleeding from isolated vessels occur within the bone?

        a.  Crushing the vesselís forearm

        b.  Apply a thrombin

        c.  Cauterize the vessel

        d.  All of the above

18.  What is the most commonly used, least exoensive hemostatic agent? 

        a.  Absorbable gelatin sponge

        b. Collagen tape

        c.  Oxidized regenerated methylcellulose

        d.  Iodoform  Gauze

19.  Gelatin sponge forms a scaffold for the formation of:

        a.  exudates.

        b.  osseous bone

        c.  a blood clot

        d.  none of the above

20.  Topical thrombin is derived from:

        a.  equine thrombin

        b.  bovine thrombin

        c.  Porcine thrombin

        d.  feline thrombin

21.  Thrombin bypasses all steps in the coagulation cascadeand helps to convert fibrogen to:

        a.  cancellous bone

        b.  collagen

        c.  fibrin

        d.  None of the above

22.  It is recommended that block techniques are encouraged instead of local infiltration when treating secondary bleeding.

        a.  TRUE
        b.  FALSE

23.  Ecchymosis can appear ____ after the surgery.

        a.  Immediately

b.  1-2 days

        c.  2-5 days

        d.  3-6 days

24.  Ecchymosis occurs more frequently in which patient population?

        a.  Children

        b.  Teenagers

        c.  Elderly patients

        d.  Young Adults

25.  Signs and symptoms associated with infection can include:

        a.  fever

        b.  swelling

        c.  erythema

        d.  all of the above

26.  Which is not a factor that can delay healing?

        a.  Clotting defects

        b.  Formation of oro-antral fistula

        c.  Proliferation of malignant tumors

        d.   Corticosteroid use

        e.  None of the above

27.  Which is a symptom of dry socket?

        a.  Localized pain

        b.  Bad odor

        c.  Bad taste

        d.  Dramatic relief when treated

28. The incidence of dry socket on average is approximately what percent of all extractions?

  1. 2%
  2. 1%
  3. 4%
  4. 3%

29. What is the percentage of occurrence of dry socket in impacted mandibular third molars?

      a. 9-30%

      b. 10-40%

      c. 11-50%

      d. 12-60%  

30. Which teeth are most commonly associated with the dry socket?

      a. Upper molars

      b. Lower molars

      c. Premolars

      d. Canines

31. Studies have demonstrated extraction difficulty is related to dry socket frequency.

      a. TRUE

      b. FALSE

32. It has been demonstrated that less-experienced dental surgeons have a higher incidence of dry sockets in lower third molars.

      a. TRUE

      b. FALSE

33. What is the peak patient age for dry sockets?

      a. 15-19 years

      b. 20-29 years

      c. 30-34 years

      d. 35-40 years

34. Smokes are how many times more likely to develop third molar dry sockets than nonsmokers?

      a. 4

      b. 3

      c  2

      d.  None

35. Researchers have identifies that women have a higher chance to develop dry socket than males. How much higher is the incidence in women?

     a. 10%

     b. 20%

     c. 30%

     d. 35%

36. What are the two most studied antibiotics that have been successfully used to help decrease the incidence of dry socket in mandibular third molars?

a.            a. Cefzil and Cipro

b.           b. Penicillin and Biaxin

c.            c. Clindimycin & Zithromax

d.           d. Clindimycin and Tetracyclin

e.        37. When antibiotic medicaments were placed in dry socket studies, there was a reduction form:

f.             a. 34%-1%

g.           b. 35%-2%

h.           c. 36%-3%

i.             d. 37%-4%

 

1. a b c d e

2. a b

3. a b c d e

4. a b c d e

5. a b c d e

6. a b c d e

7. a b c d e

8. a b c d e

9. a b c d e

10. a b

11. a b c d e

12. a b c d e

13. a b c d e

14. a b c d e

15. a b c d e

16. a b c d e

17. a b c d e

18. a b c d e

19. a b c d e

20. a b c d e

21. a b c d e

22. a b

23. a b c d e

24. a b c d e

25. a b c d e

26. a b c d e

27. a b c d e

28. a b c d e

29. a b c d e

30. a b c d e

31. a b

32. a b

33. a b c d e

34. a b c d e

35. a b c d e

36. a b c d e

37. a b c d e